[create-pull-request] automated change

- always use `proto tcp-client` when using TCP
- parses `tcp-client` (on top of `tcp`, `tcp4`, `tcp6`) as meaning TCP
- Fix #3302

.devcontainer/Dockerfile

@@ -1,2 +1,3 @@
 FROM ghcr.io/qdm12/godevcontainer:v0.21-alpine
-RUN apk add wireguard-tools htop openssl
+RUN apk add wireguard-tools htop openssl tcpdump iptables
+RUN apk add nodejs npm && npm install markdownlint-cli2 --global && apk del npm

.github/labels.yml

@@ -23,6 +23,8 @@
   color: "959a9c"
 - name: "Closed: ☠️ cannot be done"
   color: "959a9c"
+- name: "Closed: 🤖🍺 drunk AI"
+  color: "959a9c"
 
 - name: "Priority: 🚨 Urgent"
   color: "03adfc"
@@ -126,6 +128,8 @@
   color: "ffc7ea"
 - name: "Category: Firewall ⛓️"
   color: "ffc7ea"
+- name: "Category: MTU discovery 🔦"
+  color: "ffc7ea"
 - name: "Category: Routing 🛤️"
   color: "ffc7ea"
 - name: "Category: IPv6 🛰️"

.github/workflows/ci.yml

@@ -45,6 +45,7 @@ jobs:
           level: error
           exclude: |
             ./internal/storage/servers.json
+            ./.golangci.yml
             *.md
 
       - name: Linting
@@ -137,7 +138,7 @@ jobs:
       # https://github.com/docker/metadata-action
       - name: Extract Docker metadata
         id: meta
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           flavor: |
             latest=${{ github.ref == format('refs/heads/{0}', github.event.repository.default_branch) }}
@@ -152,15 +153,15 @@ jobs:
             type=semver,pattern=v{{major}},enable=${{ !startsWith(github.ref, 'refs/tags/v0.') }}
             type=raw,value=latest,enable=${{ github.ref == format('refs/heads/{0}', github.event.repository.default_branch) }}
 
-      - uses: docker/setup-qemu-action@v3
-      - uses: docker/setup-buildx-action@v3
+      - uses: docker/setup-qemu-action@v4
+      - uses: docker/setup-buildx-action@v4
 
-      - uses: docker/login-action@v3
+      - uses: docker/login-action@v4
         with:
           username: qmcgaw
           password: ${{ secrets.DOCKERHUB_PASSWORD }}
 
-      - uses: docker/login-action@v3
+      - uses: docker/login-action@v4
         with:
           registry: ghcr.io
           username: qdm12
@@ -168,10 +169,14 @@ jobs:
 
       - name: Short commit
         id: shortcommit
-        run: echo "::set-output name=value::$(git rev-parse --short HEAD)"
+        run: |
+          # Use the PR head SHA if it exists, otherwise fallback to GITHUB_SHA
+          FULL_SHA="${{ github.event.pull_request.head.sha || github.sha }}"
+          SHORT_SHA=
+          echo "value=$(echo $FULL_SHA | cut -c1-7)" >> $GITHUB_OUTPUT
 
       - name: Build and push final image
-        uses: docker/build-push-action@v6
+        uses: docker/build-push-action@v7
         with:
           platforms: linux/amd64,linux/386,linux/arm64,linux/arm/v6,linux/arm/v7,linux/ppc64le
           labels: ${{ steps.meta.outputs.labels }}

.github/workflows/closed-issue.yml

@@ -14,8 +14,12 @@ jobs:
           token: ${{ github.token }}
           issue-number: ${{ github.event.issue.number }}
           body: |
-            Closed issues are **NOT** monitored, so commenting here is likely to be not seen.
-            If you think this is *still unresolved* and have **more information** to bring, please create another issue.
+            Closed issues are **NOT** monitored, so commenting here will likely NOT be seen.
+            If you think this is *still unresolved* and have **more information** to bring, please either
+            re-open this issue or create another issue.
+
+            ❤️😠 temporarily help the Gluetun community and fight the AI slop scam website `gluetun[dot]com` by setting `BORINGPOLL_GLUETUNCOM=on` on the latest image.
+            See [the option in the wiki for more information](https://github.com/qdm12/gluetun-wiki/blob/main/setup/options/others.md)
 
             This is an automated comment setup because @qdm12 is the sole maintainer of this project
-            which became too popular to monitor issues closed.
+            which became too popular to monitor closed issues.

.github/workflows/labels.yml

@@ -12,6 +12,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
-      - uses: crazy-max/ghaction-github-labeler@v5
+      - uses: crazy-max/ghaction-github-labeler@v6
         with:
           yaml-file: .github/labels.yml

.github/workflows/markdown.yml

@@ -20,7 +20,7 @@ jobs:
     steps:
       - uses: actions/checkout@v6
 
-      - uses: DavidAnson/markdownlint-cli2-action@v21
+      - uses: DavidAnson/markdownlint-cli2-action@v22
         with:
           globs: "**.md"
           config: .markdownlint-cli2.jsonc
@@ -37,7 +37,7 @@ jobs:
           use-quiet-mode: yes
           config-file: .github/workflows/configs/mlc-config.json
 
-      - uses: peter-evans/dockerhub-description@v4
+      - uses: peter-evans/dockerhub-description@v5
         if: github.repository == 'qdm12/gluetun' && github.event_name == 'push'
         with:
           username: qmcgaw

.github/workflows/update-servers-list.yml

@@ -0,0 +1,98 @@
+name: Update servers list
+on:
+  workflow_dispatch:
+    inputs:
+      provider:
+        description: "VPN Provider to update"
+        required: true
+        default: "all"
+        type: choice
+        options:
+          - all
+          - airvpn
+          - cyberghost
+          - expressvpn
+          - fastestvpn
+          - giganews
+          - hidemyass
+          - ipvanish
+          - ivpn
+          - mullvad
+          - nordvpn
+          - perfect privacy
+          - privado
+          - private internet access
+          - privatevpn
+          - protonvpn
+          - purevpn
+          - slickvpn
+          - surfshark
+          - torguard
+          - vpnsecure
+          - vpn unlimited
+          - vyprvpn
+          - windscribe
+  schedule:
+    - cron: "11 3 1 */2 *" # Run at 03:11 on the 1st of every 2nd month
+jobs:
+  update-servers-list:
+    if: github.repository == 'qdm12/gluetun'
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: write
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: actions/setup-go@v6
+        with:
+          go-version-file: go.mod
+
+      - name: Update servers list
+        run: |
+          SELECTED_PROVIDER="${{ github.event.inputs.provider || 'all' }}"
+
+          if [ "$SELECTED_PROVIDER" = "all" ]; then
+            FLAGS="-all"
+          else
+            FLAGS="-providers $SELECTED_PROVIDER"
+          fi
+
+          go run ./cmd/gluetun/main.go update $FLAGS \
+            -maintainer \
+            -proton-email "${{ secrets.PROTON_EMAIL }}" \
+            -proton-password "${{ secrets.PROTON_PASSWORD }}"
+
+      - name: Check for changes
+        run: |
+          if git diff --exit-code internal/storage/servers.json >/dev/null; then
+            echo "Error: internal/storage/servers.json was not modified."
+            exit 1
+          fi
+
+      - name: Check no other file changes
+        run: |
+          if ! git diff --exit-code --quiet ':!internal/storage/servers.json'; then
+            echo "Error: Unexpected changes detected in files other than servers.json"
+            git status --short
+            exit 1
+          fi
+
+      - name: Create Pull Request
+        id: createpr
+        uses: peter-evans/create-pull-request@v8
+        with:
+          branch-suffix: timestamp
+          branch: bot/update-servers-list
+          base: master
+          delete-branch: true
+          title: "feat(providers/${{ github.event.inputs.provider || 'all' }}): servers data update"
+          body: |
+            This PR was automatically generated by the [Update servers list](${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}) workflow run.
+
+      # - name: Merge Pull Request
+      #   env:
+      #     GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      #   run: |
+      #     gh pr merge ${{ steps.createpr.outputs.pull-request-number }} --auto -m -d

.gitignore

@@ -1 +1,2 @@
 scratch.txt
+.DS_Store

.golangci.yml

@@ -22,6 +22,7 @@ linters:
         - "^disabled$"
         # Firewall and routing strings
         - "^(ACCEPT|DROP)$"
+        - "^--append$"
         - "^--delete$"
         - "^all$"
         - "^(tcp|udp)$"
@@ -47,7 +48,7 @@ linters:
         path: internal\/server\/.+\.go
       - linters:
           - ireturn
-        text: returns interface \(github\.com\/vishvananda\/netlink\.Link\)
+        text: returns interface \(golang\.org\/x\/sys\/unix\.Sockaddr\)
       - linters:
           - ireturn
         path: internal\/openvpn\/pkcs8\/descbc\.go
@@ -59,6 +60,10 @@ linters:
       - linters:
           - lll
         source: "^// https://.+$"
+      - linters:
+          - mnd
+        source: "^	cleanups\\.Add.+$"
+        path: internal\/(wireguard|amneziawg)\/run\.go
       - linters:
           - err113
           - mnd

AGENTS.md

@@ -0,0 +1,195 @@
+# AGENTS
+
+Guidance for coding agents working in this repository.
+
+## Scope and priorities
+
+- Keep changes minimal and targeted. Feel free to do light refactors that are relevant to the modifications.
+- Breaking changes:
+  - Do not introduce breaking usage behavior (cli flags, environment variables, etc.) unless explicitly agreed.
+  - Do not introduce breaking changes for the Go API in the `pkg/` directory.
+  - If a compatibility break seems beneficial, stop and ask for confirmation before implementing it.
+- Update or add tests when behavior changes.
+
+## Go coding conventions
+
+### General guidelines
+
+- Use explicit, descriptive variable names by default.
+  - Notable bad examples: `req`, `resp`, `cfg`, `v`
+  - Allowed short-name exceptions:
+    - indexes such as `i`, `j`
+    - `ctx` for `context.Context`
+    - `t` for `*testing.T` and `b` for `*testing.B`
+    - `ctrl` for `*gomock.Controller`
+    - `err` for `error`, `errs` for `[]error`
+    - `wg` for `*sync.WaitGroup`
+- Avoid using global variables except for:
+  - exported sentinel errors that are used outside the package boundaries
+  - regular expressions defined with `regexp.MustCompile`
+  - variables set by the build pipeline, such as `Version` and `BuildDate`
+- Constants
+  - Prefer defining them inline in a function if it's only used in that function, rather than at the package level.
+  - Each one should be defined right above where it's used, instead of having multiple defined at the same place in a `const ()` block
+  - If one is only used in a single production code function, define it right above it so it's more local for readability.
+  - Do not define constants when constants exist in other packages, for example `http.StatusBadRequest` or `log.LevelDebug`.
+- Structs
+  - Prefer defining them inline in a function if it's only used in that function, rather than at the package level.
+- Do not use the short if form, prefer the longer one
+- Follow modern Go, according to the Go version defined in go.mod. Prefer modern constructs when equivalent:
+  - Example: use `for i := range 5` rather than `for i := 0; i < 5; i++`.
+  - Example: use `new("string")` rather than helper wrappers such as `stringPtr("string")`.
+  - Example: no need to pin variables in for loops when using them in goroutines or subtests.
+- Use `New(...) *Item` constructor per package. Each package should ideally only have one constructor, although this is not a strict rule. The constructor should return a pointer to the struct, and not an interface.
+- Always prefer using context-aware functions, for example:
+  - `exec.CommandContext` rather than `exec.Command`
+  - `http.NewRequestWithContext` rather than `http.NewRequest`
+- Never export a symbol unless absolutely necessary.
+- Always use the most restrictive builtin types. For example prefer `uint` over `int` if it's only zero or positive. Prefer `uint16` is the max value is 65535.
+- Prefer using builtin types whenever possible AND do not define single field structs unless necessary
+- Prefer splitting a code line only when it triggers the `lll` linter, do not split a command or arguments list for each element
+- Use `netip` types instead of `net` types whenever possible
+- Use constants instead of variables whenever possible, especially function-local inline constants.
+- Do not use `time.Sleep`, prefer using a `time.Timer` with a `select` statement also listening on a context cancelation
+- `panic`:
+  - should only be used when a programming error is encountered and you should NOT return errors for programming errors (such as passing nil objects)
+  - Its counterpart `recover` should not really be used, except for testing a panic in test code (or use `assert.PanicsWithValue`).
+
+### Directory structure and file naming
+
+- Executable main packages with a single `main()` function must be in the `cmd` directory.
+  Prefer having top level logic and have a longer `main()` function rather than having an `internal/app` package.
+- Code lives by default in subpackages within the `internal` directory
+- Code needing to be imported by external Go modules must be in subpackages within the `pkg` directory
+- Example code especially using the `pkg` directory must be in `main` packages within the `examples` directory, each with a single `main.go` function.
+- If AND only if the repository is a Go library and not a Go application, you may have Go files at the root of the project to simplify import paths. Most of the code should still be in subpackages in the `internal` directory.
+- Interfaces should be defined in `interfaces.go` files for each package. If there are unexported interfaces which need to be mocked, which is rare, they should be defined in `interfaces_local.go` files.
+- Mock files are
+  - `mocks_generate_test.go` which only contains `//go:generate` directives for generating mocks, and no actual code
+  - `mocks_test.go` which contains the generated mocks from exported interfaces and no other code, and is ignored in coverage reports
+  - `mocks_local_test.go` (rare) which contains the generated mocks from unexported interfaces and no other code, and is ignored in coverage reports
+  - NEVER generate an exported mock in a non test file, prefer re-generating files across packages.
+- Package naming
+  - Your package name should be the same as the directory containing it, **except for the `main` package**
+  - Use single words for package names
+  - Do not use generic names for package names such as `utils` or `helpers`
+- Package nesting
+  - Try to avoid nesting packages by default
+  - You can nest packages if you have different implementations for the same interface (e.g. a store interface)
+  - You can nest packages if you start having a lot of Go files (more than 10) and it really does make sense to make subpackages
+
+### Linting
+
+The linter is `golangci-lint` with the configuration defined in `.golangci.yml`.
+
+To exclude code from linting, prefer using, when absolutely necessary, command comments `//nolint:<linter>`.
+This allows the `nolintlint` linter to detect and report unnecessary `//nolint` comments later.
+You can notably use `//nolint:lll` and, for good valid reasons, `//nolint:gosec`. Sometimes `//nolint:mnd` when it just doesn't make sense to extract a constant such as `n = n << 4`
+Always prefer placing `//nolint` comments on the same code line where the error comes from, and not above a code block.
+
+### Mocking
+
+Mocking works with the `go.uber.org/mock` library, and the `mockgen` tool.
+
+- Mocks from exported interfaces are generated using go generate commands in `mocks_generate_test.go` files, and stored in `mocks_test.go` files, using:
+
+    ```go
+    //go:generate mockgen -destination=mocks_test.go -package=$GOPACKAGE . InterfaceA,InterfaceB
+    ```
+
+- Mocks from unexported interfaces are generated using go generate commands in `mocks_generate_test.go` files, and stored in `mocks_local_test.go` files. The source file for unexported interfaces is `interfaces_local.go`. The go generate command is similar to:
+
+    ```go
+    //go:generate mockgen -destination=mocks_local_test.go -package $GOPACKAGE -source interfaces_local.go
+    ```
+
+- Mocks from external interfaces are generated using go generate commands in `mocks_generate_test.go` files, and stored in `mocks_<package-name>_test.go` files, using:
+
+    ```go
+    //go:generate mockgen -destination=mocks_<package-name>_test.go -package $GOPACKAGE module-name InterfaceA,InterfaceB
+    ```
+
+- Generated mocks usage in tests:
+  - Define mocks in the subtest, not in the parent test. You can also have a function returning the mocks as a field of the test case struct, which takes in the subtest `*testing.T` as argument, and call it in the subtest to get the mocks.
+  - **Never** use `gomock.Any()` as argument. Always use concrete, precise arguments. You might need to define a custom GoMock matcher for your argument in some very niche and corner cases.
+  - **Never** use `.AnyTimes()` on mocks. Always define the number of times a certain mock call should be called, with `.Times(3)` for example.
+  - **Always** set the `.Return(...)` on the mock if the function returns something.
+  - Avoid using **mock helpers** functions, prefer a bit of repetition than tight coupling and dependency
+
+### main.go
+
+- Make the program OS signal aware, so it attempts a graceful shutdown when interruped. Force quit the program on a second interrupt signal.
+
+### Formatting
+
+The Go formatter used is gofumpt.
+
+### Errors
+
+- Always prefer wrapping errors with some context with `fmt.Errorf("doing this: %w", err)`
+- In rare cases, you can just use `return err` notably:
+  - If the function is called **recursively**, since we don't wrap the wrapping multiple times for each recursion
+  - If the current function only statement is the call to another function, for example:
+
+      ```go
+      func (s *Struct) Fetch() error {
+        return fetch() // do not wrap the error
+      }
+      ```
+
+- When wrapping errors, use verbs ending in "ing" and no "failed to" or "cannot" to avoid redundancy. For example, use `fmt.Errorf("resolving host: %w", err)` rather than `fmt.Errorf("failed to resolve host: %w", err)`.
+- When wrapping an error, the context should NEVER contain variables injected as arguments in the function returning an error, to avoid repeating the same variable in multiple error messages.
+- Testing errors:
+  - If the error does not wrap a sentinel error, use `assert.ErrorContains` to check for error messages, rather than `assert.EqualError`, to avoid having to update tests for minor changes in error messages. And use `assert.NoError` to check for no error.
+  - If the error wraps a sentinel error, use `assert.ErrorIs` to check both for the sentinel error or an expected nil error. You can also check the error message with `assert.ErrorContains`
+
+### User program settings
+
+- For configuration structs, each field Go zero value (i.e. `0` for `int`, `nil` for `*string`) should be an INVALID value in the user sense. This is used to detect when a field is not set, in order to default it, merge it or override it. For example if `""` is not a valid value, the field should be of type `string`. Conversely, if `""` is a valid value, the field should be of type `*string` to distinguish between "not set" and "set to empty string". Notably, boolean fields are ALWAYS of type `*bool` for this reason, since both `true` and `false` are valid values.
+- Configuration reading and handling relies on the Go library github.com/qdm12/gosettings please use it whenever appropriate.
+  - Do not wrap errors coming from `reader.Reader` methods, since they already contain the necessary context.
+  - All keys passed to `reader.Reader` methods must be in environment variable format, i.e. uppercase with underscores. These get converted to lowercase and dashes for flags notably.
+- For each settings structs, define the following methods, which are usually unexported, but can be exported especially for the top level Settings struct, in this order:
+  - `func (s *Settings) setDefaults()` whichs sets defaults (using `gosettings.Default*` functions) on unset fields
+  - If the settings need to be patched at runtime, which is rarely the case, define `func (s *Settings) overrideWith(other Settings)` which overrides the settings with another settings struct, only for fields that are set in the other struct (using `gosettings.OverrideWith` functions).
+  - `func (s Settings) validate() error` which validates the settings, and returns an error if anything is invalid
+  - `func (s *Settings) read(r *reader.Reader) error` which reads the settings from a gosettings/reader.Reader (which can be from multiple sources, such as environment variables, cli flags, config files etc.)
+  - `func (s Settings) String() string` which uses `toLinesNode().String()` to return a string representation of the settings
+  - `func (s Settings) toLinesNode() *gotree.Node` which a github.com/qdm12/gotree `*Node` representing the settings
+
+### Testing
+
+- Use the github.com/stretchr/testify library for assertions
+- Most tests should be table tests with parallel subtests
+- Prefer map-based table tests of the form `map[string]struct{ ... }`, with the key as the test name.
+  Use underscores in test names, not spaces, to keep `go test` output searchable.
+- Use `testCases` for the table variable name, and `testCase` for each iterated case value.
+- Run all tests in parallel:
+  - call `t.Parallel()` in the top-level test
+  - call `t.Parallel()` in each subtest
+
+### Libraries to use
+
+- Logging: `github.com/qdm12/log`
+- Splash information at program start: `github.com/qdm12/gosplash`
+- Long running services (i.e. health server, http prod server, backup loop etc.): `github.com/qdm12/goservices`
+- String tree structures: `github.com/qdm12/gotree`
+
+### Extra rules
+
+- Do not use `http.DefaultClient`, use a custom `*http.Client` with a fixed timeout and share with dependency injections.
+- Do not check for injected dependencies being `nil`, prefer to just panic on a nil pointer. By default it's fine to panic if a developer injects a dependency `nil`. `nil` does not mean use a default.
+
+## Validation checklist
+
+Run the following before finishing changes:
+
+1. Go building `go build ./...`
+1. Go linting `golangci-lint run`
+1. Go unit tests `go test ./...`
+1. If a module is added or modified, run `go mod tidy`
+1. If an interface or mock command is modified, run `go generate -run mockgen ./...`
+
+If a Markdown file is modified and `markdownlint-cli2` is available, run `markdownlint-cli2 "**/*.md"`
+
+If a command is unavailable in the current environment, report it clearly and provide the exact command needed once available.

Dockerfile

@@ -1,5 +1,5 @@
-ARG ALPINE_VERSION=3.22
-ARG GO_ALPINE_VERSION=3.22
+ARG ALPINE_VERSION=3.23
+ARG GO_ALPINE_VERSION=3.23
 ARG GO_VERSION=1.25
 ARG XCPUTRANSLATE_VERSION=v0.9.0
 ARG GOLANGCI_LINT_VERSION=v2.4.0
@@ -13,7 +13,7 @@ FROM --platform=${BUILDPLATFORM} ghcr.io/qdm12/binpot:mockgen-${MOCKGEN_VERSION}
 FROM --platform=${BUILDPLATFORM} golang:${GO_VERSION}-alpine${GO_ALPINE_VERSION} AS base
 COPY --from=xcputranslate /xcputranslate /usr/local/bin/xcputranslate
 # Note: findutils needed to have xargs support `-d` flag for mocks stage.
-RUN apk --update add git g++ findutils
+RUN apk --update add git g++ findutils iptables
 ENV CGO_ENABLED=0
 COPY --from=golangci-lint /bin /go/bin/golangci-lint
 COPY --from=mockgen /bin /go/bin/mockgen
@@ -110,8 +110,66 @@ ENV VPN_SERVICE_PROVIDER=pia \
     WIREGUARD_PERSISTENT_KEEPALIVE_INTERVAL=0 \
     WIREGUARD_ADDRESSES= \
     WIREGUARD_ADDRESSES_SECRETFILE=/run/secrets/wireguard_addresses \
-    WIREGUARD_MTU=1320 \
+    WIREGUARD_MTU= \
     WIREGUARD_IMPLEMENTATION=auto \
+    # Amnezia
+    AMNEZIAWG_ENDPOINT_IP= \
+    AMNEZIAWG_ENDPOINT_PORT= \
+    AMNEZIAWG_CONF_SECRETFILE=/run/secrets/wg0.conf \
+    AMNEZIAWG_PRIVATE_KEY= \
+    AMNEZIAWG_PRIVATE_KEY_SECRETFILE=/run/secrets/wireguard_private_key \
+    AMNEZIAWG_PRESHARED_KEY= \
+    AMNEZIAWG_PRESHARED_KEY_SECRETFILE=/run/secrets/wireguard_preshared_key \
+    AMNEZIAWG_PUBLIC_KEY= \
+    AMNEZIAWG_ALLOWED_IPS= \
+    AMNEZIAWG_PERSISTENT_KEEPALIVE_INTERVAL=0 \
+    AMNEZIAWG_ADDRESSES= \
+    AMNEZIAWG_ADDRESSES_SECRETFILE=/run/secrets/wireguard_addresses \
+    AMNEZIAWG_MTU= \
+    AMNEZIAWG_JC=0 \
+    AMNEZIAWG_JMIN=0 \
+    AMNEZIAWG_JMAX=0 \
+    AMNEZIAWG_S1=0 \
+    AMNEZIAWG_S2=0 \
+    AMNEZIAWG_S3=0 \
+    AMNEZIAWG_S4=0 \
+    AMNEZIAWG_H1= \
+    AMNEZIAWG_H2= \
+    AMNEZIAWG_H3= \
+    AMNEZIAWG_H4= \
+    AMNEZIAWG_I1= \
+    AMNEZIAWG_I2= \
+    AMNEZIAWG_I3= \
+    AMNEZIAWG_I4= \
+    AMNEZIAWG_I5= \
+    # Wireguard AmneziaWG userspace obfuscation (requires WIREGUARD_IMPLEMENTATION=amneziawg)
+    AMNEZIAWG_JC=0 \
+    AMNEZIAWG_JMIN=0 \
+    AMNEZIAWG_JMAX=0 \
+    AMNEZIAWG_S1=0 \
+    AMNEZIAWG_S2=0 \
+    AMNEZIAWG_S3=0 \
+    AMNEZIAWG_S4=0 \
+    AMNEZIAWG_H1= \
+    AMNEZIAWG_H2= \
+    AMNEZIAWG_H3= \
+    AMNEZIAWG_H4= \
+    AMNEZIAWG_I1= \
+    AMNEZIAWG_I2= \
+    AMNEZIAWG_I3= \
+    AMNEZIAWG_I4= \
+    AMNEZIAWG_I5= \
+    # VPN server port forwarding
+    VPN_PORT_FORWARDING=off \
+    VPN_PORT_FORWARDING_PROVIDER= \
+    VPN_PORT_FORWARDING_UP_COMMAND= \
+    VPN_PORT_FORWARDING_DOWN_COMMAND= \
+    VPN_PORT_FORWARDING_LISTENING_PORTS=0 \
+    VPN_PORT_FORWARDING_PORTS_COUNT=1 \
+    VPN_PORT_FORWARDING_STATUS_FILE="/tmp/gluetun/forwarded_port" \
+    # PMTUD
+    PMTUD_ICMP_ADDRESSES=1.1.1.1,8.8.8.8 \
+    PMTUD_TCP_ADDRESSES=1.1.1.1:443,8.8.8.8:443,1.1.1.1:53,8.8.8.8:53,[2606:4700:4700::1111]:53,[2001:4860:4860::8888]:53,[2606:4700:4700::1111]:443,[2001:4860:4860::8888]:443 \
     # VPN server filtering
     SERVER_REGIONS= \
     SERVER_COUNTRIES= \
@@ -123,14 +181,8 @@ ENV VPN_SERVICE_PROVIDER=pia \
     OWNED_ONLY=no \
     # # Private Internet Access only:
     PRIVATE_INTERNET_ACCESS_OPENVPN_ENCRYPTION_PRESET= \
-    VPN_PORT_FORWARDING=off \
-    VPN_PORT_FORWARDING_LISTENING_PORT=0 \
-    VPN_PORT_FORWARDING_PROVIDER= \
-    VPN_PORT_FORWARDING_STATUS_FILE="/tmp/gluetun/forwarded_port" \
     VPN_PORT_FORWARDING_USERNAME= \
     VPN_PORT_FORWARDING_PASSWORD= \
-    VPN_PORT_FORWARDING_UP_COMMAND= \
-    VPN_PORT_FORWARDING_DOWN_COMMAND= \
     # # Cyberghost only:
     OPENVPN_CERT= \
     OPENVPN_KEY= \
@@ -162,7 +214,9 @@ ENV VPN_SERVICE_PROVIDER=pia \
     FIREWALL_VPN_INPUT_PORTS= \
     FIREWALL_INPUT_PORTS= \
     FIREWALL_OUTBOUND_SUBNETS= \
-    FIREWALL_DEBUG=off \
+    FIREWALL_IPTABLES_LOG_LEVEL=info \
+    # IPv6
+    IPV6_CHECK_ADDRESSES=[2001:4860:4860::8888]:53,[2606:4700:4700::1111]:53 \
     # Logging
     LOG_LEVEL=info \
     # Health
@@ -172,9 +226,9 @@ ENV VPN_SERVICE_PROVIDER=pia \
     HEALTH_SMALL_CHECK_TYPE=icmp \
     HEALTH_RESTART_VPN=on \
     # DNS
-    DNS_SERVER=on \
     DNS_UPSTREAM_RESOLVER_TYPE=DoT \
-    DNS_UPSTREAM_RESOLVERS=cloudflare \
+    # Note: DNS_UPSTREAM_RESOLVERS defaults to cloudflare in code if DNS_UPSTREAM_PLAIN_ADDRESSES is empty
+    DNS_UPSTREAM_RESOLVERS= \
     DNS_BLOCK_IPS= \
     DNS_BLOCK_IP_PREFIXES= \
     DNS_CACHING=on \
@@ -185,8 +239,7 @@ ENV VPN_SERVICE_PROVIDER=pia \
     DNS_UNBLOCK_HOSTNAMES= \
     DNS_REBINDING_PROTECTION_EXEMPT_HOSTNAMES= \
     DNS_UPDATE_PERIOD=24h \
-    DNS_ADDRESS=127.0.0.1 \
-    DNS_KEEP_NAMESERVER=off \
+    DNS_UPSTREAM_PLAIN_ADDRESSES= \
     # HTTP proxy
     HTTPPROXY= \
     HTTPPROXY_LOG=off \
@@ -228,6 +281,7 @@ ENV VPN_SERVICE_PROVIDER=pia \
     PPROF_HTTP_SERVER_ADDRESS=":6060" \
     # Extras
     VERSION_INFORMATION=on \
+    BORINGPOLL_GLUETUNCOM=off \
     TZ= \
     PUID=1000 \
     PGID=1000

README.md

@@ -2,6 +2,8 @@
 
 ⚠️ This and [gluetun-wiki](https://github.com/qdm12/gluetun-wiki) are the only websites for Gluetun, other websites claiming to be official are scams ⚠️
 
+💁 You can optionally set `BORINGPOLL_GLUETUNCOM=on` to... [poll](./internal/boringpoll/boringpoll.go) that **scammy AI slop** website every few minutes so it costs them too much to keep it up. My gentle email reminders to take it down are being grossly ignored 🤷 This would make me very happy and serve this community.
+
 Lightweight swiss-army-knife-like VPN client to multiple VPN service providers
 
 ![Title image](https://raw.githubusercontent.com/qdm12/gluetun/master/title.svg)
@@ -57,14 +59,15 @@ Lightweight swiss-army-knife-like VPN client to multiple VPN service providers
 
 ## Features
 
-- Based on Alpine 3.22 for a small Docker image of 41.1MB
-- Supports: **AirVPN**, **Cyberghost**, **ExpressVPN**, **FastestVPN**, **Giganews**, **HideMyAss**, **IPVanish**, **IVPN**, **Mullvad**, **NordVPN**, **Perfect Privacy**, **Privado**, **Private Internet Access**, **PrivateVPN**, **ProtonVPN**, **PureVPN**,  **SlickVPN**, **Surfshark**, **TorGuard**, **VPNSecure.me**, **VPNUnlimited**, **Vyprvpn**, **Windscribe** servers
+- Based on Alpine 3.23 for a small Docker image of 43.1MB
+- Supports: **AirVPN**, **Cyberghost**, **ExpressVPN**, **FastestVPN**, **Giganews**, **HideMyAss**, **IPVanish**, **IVPN**, **Mullvad** (Wireguard only), **NordVPN**, **Perfect Privacy**, **Privado**, **Private Internet Access**, **PrivateVPN**, **ProtonVPN**, **PureVPN**,  **SlickVPN**, **Surfshark**, **TorGuard**, **VPNSecure.me**, **VPNUnlimited**, **Vyprvpn**, **Windscribe** servers
 - Supports OpenVPN for all providers listed
 - Supports Wireguard both kernelspace and userspace
   - For **AirVPN**, **FastestVPN**, **Ivpn**, **Mullvad**, **NordVPN**, **Perfect privacy**, **ProtonVPN**, **Surfshark** and **Windscribe**
   - For **Cyberghost**, **Private Internet Access**, **PrivateVPN**, **PureVPN**, **Torguard**, **VPN Unlimited** and **VyprVPN** using [the custom provider](https://github.com/qdm12/gluetun-wiki/blob/main/setup/providers/custom.md)
   - For custom Wireguard configurations using [the custom provider](https://github.com/qdm12/gluetun-wiki/blob/main/setup/providers/custom.md)
   - More in progress, see [#134](https://github.com/qdm12/gluetun/issues/134)
+- Supports AmneziaWG only with the custom provider for now
 - DNS over TLS baked in with service provider(s) of your choice
 - DNS fine blocking of malicious/ads/surveillance hostnames and IP addresses, with live update every 24 hours
 - Choose the vpn network protocol, `udp` or `tcp`

ci/internal/simple.go

@@ -17,7 +17,7 @@ import (
 func ptrTo[T any](v T) *T { return &v }
 
 func simpleTest(ctx context.Context, env []string, logger Logger) error {
-	const timeout = 30 * time.Second
+	const timeout = 60 * time.Second
 	ctx, cancel := context.WithTimeout(ctx, timeout)
 	defer cancel()
 

cmd/gluetun/main.go

@@ -16,7 +16,10 @@ import (
 	_ "time/tzdata"
 
 	_ "github.com/breml/rootcerts"
+	"github.com/qdm12/dns/v2/pkg/doh"
+	dnsprovider "github.com/qdm12/dns/v2/pkg/provider"
 	"github.com/qdm12/gluetun/internal/alpine"
+	"github.com/qdm12/gluetun/internal/boringpoll"
 	"github.com/qdm12/gluetun/internal/cli"
 	"github.com/qdm12/gluetun/internal/command"
 	"github.com/qdm12/gluetun/internal/configuration/settings"
@@ -168,7 +171,7 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 
 	defer fmt.Println(gluetunLogo)
 
-	announcementExp, err := time.Parse(time.RFC3339, "2024-12-01T00:00:00Z")
+	announcementExp, err := time.Parse(time.RFC3339, "2026-04-30T00:00:00Z")
 	if err != nil {
 		return err
 	}
@@ -179,7 +182,7 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 		Version:      buildInfo.Version,
 		Commit:       buildInfo.Commit,
 		Created:      buildInfo.Created,
-		Announcement: "All control server routes will become private by default after the v3.41.0 release",
+		Announcement: "Set BORINGPOLL_GLUETUNCOM=on to help combat AI slop and shutdown that scam website",
 		AnnounceExp:  announcementExp,
 		// Sponsor information
 		PaypalUser:    "qmcgaw",
@@ -207,9 +210,6 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 	netLinker.PatchLoggerLevel(logLevel)
 
 	routingLogger := logger.New(log.SetComponent("routing"))
-	if *allSettings.Firewall.Debug { // To remove in v4
-		routingLogger.Patch(log.SetLevel(log.LevelDebug))
-	}
 	routingConf := routing.New(netLinker, routingLogger)
 
 	defaultRoutes, err := routingConf.DefaultRoutes()
@@ -222,11 +222,11 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 		return err
 	}
 
+	iptablesLogLevel, _ := log.ParseLevel(allSettings.Firewall.Iptables.LogLevel)
+	iptablesLogger := logger.New(log.SetComponent("iptables"), log.SetLevel(iptablesLogLevel))
+
 	firewallLogger := logger.New(log.SetComponent("firewall"))
-	if *allSettings.Firewall.Debug { // To remove in v4
-		firewallLogger.Patch(log.SetLevel(log.LevelDebug))
-	}
-	firewallConf, err := firewall.NewConfig(ctx, firewallLogger, cmder,
+	firewallConf, err := firewall.NewConfig(ctx, firewallLogger, iptablesLogger, cmder,
 		defaultRoutes, localNetworks)
 	if err != nil {
 		return err
@@ -237,6 +237,10 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 		if err != nil {
 			return err
 		}
+		err = netLinker.FlushConntrack()
+		if err != nil {
+			logger.Warnf("flushing conntrack failed: %s", err)
+		}
 	}
 
 	// TODO run this in a loop or in openvpn to reload from file without restarting
@@ -246,10 +250,13 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 		return err
 	}
 
-	ipv6Supported, err := netLinker.IsIPv6Supported()
+	ipv6SupportLevel, err := netLinker.FindIPv6SupportLevel(ctx,
+		allSettings.IPv6.CheckAddresses, firewallConf)
 	if err != nil {
 		return fmt.Errorf("checking for IPv6 support: %w", err)
 	}
+	ipv6Supported := ipv6SupportLevel == netlink.IPv6Supported ||
+		ipv6SupportLevel == netlink.IPv6Internet
 
 	err = allSettings.Validate(storage, ipv6Supported, logger)
 	if err != nil {
@@ -264,7 +271,7 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 
 	puid, pgid := int(*allSettings.System.PUID), int(*allSettings.System.PGID)
 
-	const clientTimeout = 15 * time.Second
+	const clientTimeout = 35 * time.Second
 	httpClient := &http.Client{Timeout: clientTimeout}
 	// Create configurators
 	alpineConf := alpine.New()
@@ -279,7 +286,7 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 	err = printVersions(ctx, logger, []printVersionElement{
 		{name: "Alpine", getVersion: alpineConf.Version},
 		{name: "OpenVPN", getVersion: ovpnVersion},
-		{name: "IPtables", getVersion: firewallConf.Version},
+		{name: "Firewall", getVersion: firewallConf.Version},
 	})
 	if err != nil {
 		return err
@@ -395,7 +402,7 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 
 	dnsLogger := logger.New(log.SetComponent("dns"))
 	dnsLooper, err := dns.NewLoop(allSettings.DNS, httpClient,
-		dnsLogger)
+		dnsLogger, localNetworksToPrefixes(localNetworks))
 	if err != nil {
 		return fmt.Errorf("creating DNS loop: %w", err)
 	}
@@ -428,20 +435,31 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 	go healthcheckServer.Run(healthServerCtx, healthServerDone)
 	healthChecker := healthcheck.NewChecker(healthLogger)
 
+	// Note: we use a separate DoH dialer for the VPN servers data updater, separate from the
+	// main DNS local server to make sure no request is blocked by filters.
+	dohDialer, err := doh.New(doh.Settings{
+		UpstreamResolvers: []dnsprovider.Provider{dnsprovider.Cloudflare(), dnsprovider.Google()},
+	})
+	if err != nil {
+		return fmt.Errorf("creating updater DoH dialer: %w", err)
+	}
 	updaterLogger := logger.New(log.SetComponent("updater"))
 
 	unzipper := unzip.New(httpClient)
-	parallelResolver := resolver.NewParallelResolver(allSettings.Updater.DNSAddress)
+	parallelResolver := resolver.NewParallelResolver(dohDialer)
 	openvpnFileExtractor := extract.New()
 	providers := provider.NewProviders(storage, time.Now, updaterLogger,
 		httpClient, unzipper, parallelResolver, publicIPLooper.Fetcher(),
 		openvpnFileExtractor, allSettings.Updater)
 
+	boringPollLogger := logger.New(log.SetComponent("boring poll"))
+	boringPoll := boringpoll.New(httpClient, boringPollLogger, allSettings.BoringPoll)
+
 	vpnLogger := logger.New(log.SetComponent("vpn"))
-	vpnLooper := vpn.NewLoop(allSettings.VPN, ipv6Supported, allSettings.Firewall.VPNInputPorts,
-		providers, storage, allSettings.Health, healthChecker, healthcheckServer, ovpnConf, netLinker, firewallConf,
-		routingConf, portForwardLooper, cmder, publicIPLooper, dnsLooper, vpnLogger, httpClient,
-		buildInfo, *allSettings.Version.Enabled)
+	vpnLooper := vpn.NewLoop(allSettings.VPN, ipv6SupportLevel, allSettings.Firewall.VPNInputPorts,
+		providers, storage, boringPoll, allSettings.Health, healthChecker, healthcheckServer,
+		ovpnConf, netLinker, firewallConf, routingConf, portForwardLooper, cmder, publicIPLooper,
+		dnsLooper, vpnLogger, httpClient, buildInfo, *allSettings.Version.Enabled)
 	vpnHandler, vpnCtx, vpnDone := goshutdown.NewGoRoutineHandler(
 		"vpn", goroutine.OptionTimeout(time.Second))
 	go vpnLooper.Run(vpnCtx, vpnDone)
@@ -479,7 +497,7 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 	httpServer, err := server.New(httpServerCtx, allSettings.ControlServer,
 		logger.New(log.SetComponent("http server")),
 		buildInfo, vpnLooper, portForwardLooper, dnsLooper, updaterLooper, publicIPLooper,
-		storage, ipv6Supported)
+		storage, ipv6SupportLevel.IsSupported())
 	if err != nil {
 		return fmt.Errorf("setting up control server: %w", err)
 	}
@@ -549,13 +567,24 @@ func printVersions(ctx context.Context, logger infoer,
 	return nil
 }
 
+func localNetworksToPrefixes(localNetworks []routing.LocalNetwork) (prefixes []netip.Prefix) {
+	prefixes = make([]netip.Prefix, len(localNetworks))
+	for i, localNetwork := range localNetworks {
+		prefixes[i] = localNetwork.IPNet
+	}
+	return prefixes
+}
+
 type netLinker interface {
 	Addresser
 	Router
 	Ruler
 	Linker
 	IsWireguardSupported() (ok bool, err error)
-	IsIPv6Supported() (ok bool, err error)
+	FindIPv6SupportLevel(ctx context.Context,
+		checkAddresses []netip.AddrPort, firewall netlink.Firewall,
+	) (level netlink.IPv6SupportLevel, err error)
+	FlushConntrack() error
 	PatchLoggerLevel(level log.Level)
 }
 
@@ -607,6 +636,8 @@ type RunStarter interface {
 	Run(cmd *exec.Cmd) (output string, err error)
 	Start(cmd *exec.Cmd) (stdoutLines, stderrLines <-chan string,
 		waitError <-chan error, err error)
+	RunAndLog(ctx context.Context, commandString string,
+		logger command.Logger) (err error)
 }
 
 const gluetunLogo = `                         @@@

go.mod

@@ -4,31 +4,34 @@ go 1.25.0
 
 require (
 	github.com/ProtonMail/go-srp v0.0.7
-	github.com/breml/rootcerts v0.3.3
+	github.com/amnezia-vpn/amneziawg-go v0.2.16
+	github.com/breml/rootcerts v0.3.4
 	github.com/fatih/color v1.18.0
 	github.com/golang/mock v1.6.0
 	github.com/jsimonetti/rtnetlink v1.4.2
-	github.com/klauspost/compress v1.18.1
+	github.com/klauspost/compress v1.18.4
 	github.com/klauspost/pgzip v1.2.6
 	github.com/mdlayher/genetlink v1.3.2
+	github.com/mdlayher/netlink v1.9.0
 	github.com/pelletier/go-toml/v2 v2.2.4
-	github.com/qdm12/dns/v2 v2.0.0-rc10
+	github.com/qdm12/dns/v2 v2.0.0-rc9.0.20260421173011-9de8e7fdbe3a
 	github.com/qdm12/gosettings v0.4.4
 	github.com/qdm12/goshutdown v0.3.0
-	github.com/qdm12/gosplash v0.2.0
+	github.com/qdm12/gosplash v0.2.1-0.20260305164749-b713de4fee6c
 	github.com/qdm12/gotree v0.3.0
 	github.com/qdm12/log v0.1.0
 	github.com/qdm12/ss-server v0.6.0
 	github.com/stretchr/testify v1.11.1
+	github.com/ti-mo/netfilter v0.5.3
 	github.com/ulikunitz/xz v0.5.15
 	github.com/youmark/pkcs8 v0.0.0-20201027041543-1326539a0a0a
 	golang.org/x/exp v0.0.0-20241009180824-f66d83c29e7c
-	golang.org/x/net v0.49.0
-	golang.org/x/sys v0.40.0
-	golang.org/x/text v0.33.0
+	golang.org/x/net v0.51.0
+	golang.org/x/sys v0.42.0
+	golang.org/x/text v0.35.0
 	golang.zx2c4.com/wireguard v0.0.0-20231211153847-12269c276173
 	golang.zx2c4.com/wireguard/wgctrl v0.0.0-20230429144221-925a1e7659e6
-	gopkg.in/ini.v1 v1.67.0
+	gopkg.in/ini.v1 v1.67.1
 )
 
 require (
@@ -40,10 +43,8 @@ require (
 	github.com/cronokirby/saferith v0.33.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/google/go-cmp v0.7.0 // indirect
-	github.com/josharian/native v1.1.0 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/mdlayher/netlink v1.7.2 // indirect
 	github.com/mdlayher/socket v0.5.1 // indirect
 	github.com/miekg/dns v1.1.62 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
@@ -55,11 +56,10 @@ require (
 	github.com/prometheus/procfs v0.15.1 // indirect
 	github.com/qdm12/goservices v0.1.1-0.20251104135713-6bee97bd4978 // indirect
 	github.com/riobard/go-bloom v0.0.0-20200614022211-cdc8013cb5b3 // indirect
-	golang.org/x/crypto v0.47.0 // indirect
-	golang.org/x/mod v0.31.0 // indirect
-	golang.org/x/sync v0.19.0 // indirect
-	golang.org/x/time v0.3.0 // indirect
-	golang.org/x/tools v0.40.0 // indirect
+	golang.org/x/crypto v0.48.0 // indirect
+	golang.org/x/mod v0.33.0 // indirect
+	golang.org/x/sync v0.20.0 // indirect
+	golang.org/x/tools v0.42.0 // indirect
 	golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2 // indirect
 	google.golang.org/protobuf v1.35.1 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect

go.sum

@@ -6,10 +6,12 @@ github.com/ProtonMail/go-crypto v1.3.0-proton h1:tAQKQRZX/73VmzK6yHSCaRUOvS/3OYS
 github.com/ProtonMail/go-crypto v1.3.0-proton/go.mod h1:9whxjD8Rbs29b4XWbB8irEcE8KHMqaR2e7GWU1R+/PE=
 github.com/ProtonMail/go-srp v0.0.7 h1:Sos3Qk+th4tQR64vsxGIxYpN3rdnG9Wf9K4ZloC1JrI=
 github.com/ProtonMail/go-srp v0.0.7/go.mod h1:giCp+7qRnMIcCvI6V6U3S1lDDXDQYx2ewJ6F/9wdlJk=
+github.com/amnezia-vpn/amneziawg-go v0.2.16 h1:XY6HOq/xtqH8ZXMncRWkjFs85EKdN10NLNnw23kTpE0=
+github.com/amnezia-vpn/amneziawg-go v0.2.16/go.mod h1:nRkPpIzjCxMW8pZKXTRkpqAQVlmFJdVOGkeQSC7wbms=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
-github.com/breml/rootcerts v0.3.3 h1://GnaRtQ/9BY2+GtMk2wtWxVdCRysiaPr5/xBwl7NKw=
-github.com/breml/rootcerts v0.3.3/go.mod h1:S/PKh+4d1HUn4HQovEB8hPJZO6pUZYrIhmXBhsegfXw=
+github.com/breml/rootcerts v0.3.4 h1:9i7WNl/ctd9OEAOaTfLy//Wrlfxq/tRQ7v4okYFN9Ys=
+github.com/breml/rootcerts v0.3.4/go.mod h1:S/PKh+4d1HUn4HQovEB8hPJZO6pUZYrIhmXBhsegfXw=
 github.com/bwesterb/go-ristretto v1.2.0/go.mod h1:fUIoIZaG73pV5biE2Blr2xEzDoMj7NFEuV9ekS419A0=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
@@ -20,22 +22,21 @@ github.com/cloudflare/circl v1.6.1 h1:zqIqSPIndyBh1bjLVVDHMPpVKqp8Su/V+6MeDzzQBQ
 github.com/cloudflare/circl v1.6.1/go.mod h1:uddAzsPgqdMAYatqJ0lsjX1oECcQLIlRpzZh3pJrofs=
 github.com/cronokirby/saferith v0.33.0 h1:TgoQlfsD4LIwx71+ChfRcIpjkw+RPOapDEVxa+LhwLo=
 github.com/cronokirby/saferith v0.33.0/go.mod h1:QKJhjoqUtBsXCAVEjw38mFqoi7DebT7kthcD7UzbnoA=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
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@@ -49,8 +50,8 @@ github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWE
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@@ -73,16 +74,16 @@ github.com/prometheus/common v0.60.1 h1:FUas6GcOw66yB/73KC+BOZoFJmbo/1pojoILArPA
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@@ -93,28 +94,39 @@ github.com/riobard/go-bloom v0.0.0-20200614022211-cdc8013cb5b3 h1:f/FNXud6gA3MNr
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@@ -122,14 +134,14 @@ golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4/go.mod h1:p54w0d4576C0XHj96b
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@@ -142,8 +154,8 @@ golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBc
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-golang.org/x/sys v0.40.0 h1:DBZZqJ2Rkml6QMQsZywtnjnnGvHza6BTfYFWY9kjEWQ=
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@@ -153,17 +165,17 @@ golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
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-golang.org/x/text v0.33.0 h1:B3njUFyqtHDUI5jMn1YIr5B0IE2U0qck04r6d4KPAxE=
-golang.org/x/text v0.33.0/go.mod h1:LuMebE6+rBincTi9+xWTY8TztLzKHc/9C1uBCG27+q8=
-golang.org/x/time v0.3.0 h1:rg5rLMjNzMS1RkNLzCG38eapWhnYLFYXDXj2gOlr8j4=
-golang.org/x/time v0.3.0/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
+golang.org/x/text v0.35.0 h1:JOVx6vVDFokkpaq1AEptVzLTpDe9KGpj5tR4/X+ybL8=
+golang.org/x/text v0.35.0/go.mod h1:khi/HExzZJ2pGnjenulevKNX1W67CUy0AsXcNubPGCA=
+golang.org/x/time v0.9.0 h1:EsRrnYcQiGH+5FfbgvV4AP7qEZstoyrHB0DzarOQ4ZY=
+golang.org/x/time v0.9.0/go.mod h1:3BpzKBy/shNhVucY/MWOyx10tF3SFh9QdLuxbVysPQM=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.1.1/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
 golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
-golang.org/x/tools v0.40.0 h1:yLkxfA+Qnul4cs9QA3KnlFu0lVmd8JJfoq+E41uSutA=
-golang.org/x/tools v0.40.0/go.mod h1:Ik/tzLRlbscWpqqMRjyWYDisX8bG13FrdXp3o4Sr9lc=
+golang.org/x/tools v0.42.0 h1:uNgphsn75Tdz5Ji2q36v/nsFSfR/9BRFvqhGBaJGd5k=
+golang.org/x/tools v0.42.0/go.mod h1:Ma6lCIwGZvHK6XtgbswSoWroEkhugApmsXyrUmBhfr0=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
@@ -178,12 +190,13 @@ google.golang.org/protobuf v1.35.1/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojt
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
-gopkg.in/ini.v1 v1.67.0 h1:Dgnx+6+nfE+IfzjUEISNeydPJh9AXNNsWbGP9KzCsOA=
-gopkg.in/ini.v1 v1.67.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
+gopkg.in/ini.v1 v1.67.1 h1:tVBILHy0R6e4wkYOn3XmiITt/hEVH4TFMYvAX2Ytz6k=
+gopkg.in/ini.v1 v1.67.1/go.mod h1:x/cyOwCgZqOkJoDIJ3c1KNHMo10+nLGAhh+kn3Zizss=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-gvisor.dev/gvisor v0.0.0-20230927004350-cbd86285d259 h1:TbRPT0HtzFP3Cno1zZo7yPzEEnfu8EjLfl6IU9VfqkQ=
-gvisor.dev/gvisor v0.0.0-20230927004350-cbd86285d259/go.mod h1:AVgIgHMwK63XvmAzWG9vLQ41YnVHN0du0tEC46fI7yY=
+gvisor.dev/gvisor v0.0.0-20231202080848-1f7806d17489 h1:ze1vwAdliUAr68RQ5NtufWaXaOg8WUO2OACzEV+TNdE=
+gvisor.dev/gvisor v0.0.0-20231202080848-1f7806d17489/go.mod h1:10sU+Uh5KKNv1+2x2A0Gvzt8FjD3ASIhorV3YsauXhk=
 kernel.org/pub/linux/libs/security/libcap/cap v1.2.70 h1:QnLPkuDWWbD5C+3DUA2IUXai5TK6w2zff+MAGccqdsw=
 kernel.org/pub/linux/libs/security/libcap/cap v1.2.70/go.mod h1:/iBwcj9nbLejQitYvUm9caurITQ6WyNHibJk6Q9fiS4=
 kernel.org/pub/linux/libs/security/libcap/psx v1.2.70 h1:HsB2G/rEQiYyo1bGoQqHZ/Bvd6x1rERQTNdPr1FyWjI=

internal/amneziawg/constructor.go

@@ -0,0 +1,22 @@
+package amneziawg
+
+type Amneziawg struct {
+	logger   Logger
+	settings Settings
+	netlink  NetLinker
+}
+
+func New(settings Settings, netlink NetLinker,
+	logger Logger,
+) (a *Amneziawg, err error) {
+	settings.SetDefaults()
+	if err := settings.Check(); err != nil {
+		return nil, err
+	}
+
+	return &Amneziawg{
+		logger:   logger,
+		settings: settings,
+		netlink:  netlink,
+	}, nil
+}

internal/amneziawg/constructor_test.go

@@ -0,0 +1,86 @@
+package amneziawg
+
+import (
+	"net/netip"
+	"testing"
+
+	"github.com/qdm12/gluetun/internal/wireguard"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.zx2c4.com/wireguard/device"
+)
+
+func Test_New(t *testing.T) {
+	t.Parallel()
+
+	const validKeyString = "oMNSf/zJ0pt1ciy+qIRk8Rlyfs9accwuRLnKd85Yl1Q="
+	logger := NewMockLogger(nil)
+	netLinker := NewMockNetLinker(nil)
+
+	testCases := map[string]struct {
+		settings  Settings
+		amneziawg *Amneziawg
+		err       error
+	}{
+		"bad_settings": {
+			settings: Settings{
+				Wireguard: wireguard.Settings{
+					PrivateKey: "",
+				},
+			},
+			err: wireguard.ErrPrivateKeyMissing,
+		},
+		"minimal valid settings": {
+			settings: Settings{
+				Wireguard: wireguard.Settings{
+					PrivateKey: validKeyString,
+					PublicKey:  validKeyString,
+					Endpoint:   netip.AddrPortFrom(netip.AddrFrom4([4]byte{1, 2, 3, 4}), 0),
+					Addresses: []netip.Prefix{
+						netip.PrefixFrom(netip.AddrFrom4([4]byte{5, 6, 7, 8}), 32),
+					},
+					FirewallMark: 100,
+				},
+			},
+			amneziawg: &Amneziawg{
+				logger:  logger,
+				netlink: netLinker,
+				settings: Settings{
+					Wireguard: wireguard.Settings{
+						InterfaceName: "wg0",
+						PrivateKey:    validKeyString,
+						PublicKey:     validKeyString,
+						Endpoint:      netip.AddrPortFrom(netip.AddrFrom4([4]byte{1, 2, 3, 4}), 51820),
+						Addresses: []netip.Prefix{
+							netip.PrefixFrom(netip.AddrFrom4([4]byte{5, 6, 7, 8}), 32),
+						},
+						AllowedIPs: []netip.Prefix{
+							netip.MustParsePrefix("0.0.0.0/0"),
+						},
+						FirewallMark:   100,
+						MTU:            device.DefaultMTU,
+						IPv6:           ptrTo(false),
+						Implementation: "auto",
+					},
+				},
+			},
+		},
+	}
+
+	for name, testCase := range testCases {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			wireguard, err := New(testCase.settings, netLinker, logger)
+
+			if testCase.err != nil {
+				require.Error(t, err)
+				assert.Equal(t, testCase.err.Error(), err.Error())
+			} else {
+				assert.NoError(t, err)
+			}
+
+			assert.Equal(t, testCase.amneziawg, wireguard)
+		})
+	}
+}

internal/amneziawg/helpers_test.go

@@ -0,0 +1,5 @@
+package amneziawg
+
+func ptrTo[T any](v T) *T {
+	return &v
+}

internal/amneziawg/log.go

@@ -0,0 +1,11 @@
+package amneziawg
+
+//go:generate mockgen -destination=log_mock_test.go -package amneziawg . Logger
+
+type Logger interface {
+	Debug(s string)
+	Debugf(format string, args ...interface{})
+	Info(s string)
+	Error(s string)
+	Errorf(format string, args ...interface{})
+}

internal/amneziawg/log_mock_test.go

@@ -0,0 +1,104 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/qdm12/gluetun/internal/amneziawg (interfaces: Logger)
+
+// Package amneziawg is a generated GoMock package.
+package amneziawg
+
+import (
+	reflect "reflect"
+
+	gomock "github.com/golang/mock/gomock"
+)
+
+// MockLogger is a mock of Logger interface.
+type MockLogger struct {
+	ctrl     *gomock.Controller
+	recorder *MockLoggerMockRecorder
+}
+
+// MockLoggerMockRecorder is the mock recorder for MockLogger.
+type MockLoggerMockRecorder struct {
+	mock *MockLogger
+}
+
+// NewMockLogger creates a new mock instance.
+func NewMockLogger(ctrl *gomock.Controller) *MockLogger {
+	mock := &MockLogger{ctrl: ctrl}
+	mock.recorder = &MockLoggerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockLogger) EXPECT() *MockLoggerMockRecorder {
+	return m.recorder
+}
+
+// Debug mocks base method.
+func (m *MockLogger) Debug(arg0 string) {
+	m.ctrl.T.Helper()
+	m.ctrl.Call(m, "Debug", arg0)
+}
+
+// Debug indicates an expected call of Debug.
+func (mr *MockLoggerMockRecorder) Debug(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Debug", reflect.TypeOf((*MockLogger)(nil).Debug), arg0)
+}
+
+// Debugf mocks base method.
+func (m *MockLogger) Debugf(arg0 string, arg1 ...interface{}) {
+	m.ctrl.T.Helper()
+	varargs := []interface{}{arg0}
+	for _, a := range arg1 {
+		varargs = append(varargs, a)
+	}
+	m.ctrl.Call(m, "Debugf", varargs...)
+}
+
+// Debugf indicates an expected call of Debugf.
+func (mr *MockLoggerMockRecorder) Debugf(arg0 interface{}, arg1 ...interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	varargs := append([]interface{}{arg0}, arg1...)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Debugf", reflect.TypeOf((*MockLogger)(nil).Debugf), varargs...)
+}
+
+// Error mocks base method.
+func (m *MockLogger) Error(arg0 string) {
+	m.ctrl.T.Helper()
+	m.ctrl.Call(m, "Error", arg0)
+}
+
+// Error indicates an expected call of Error.
+func (mr *MockLoggerMockRecorder) Error(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Error", reflect.TypeOf((*MockLogger)(nil).Error), arg0)
+}
+
+// Errorf mocks base method.
+func (m *MockLogger) Errorf(arg0 string, arg1 ...interface{}) {
+	m.ctrl.T.Helper()
+	varargs := []interface{}{arg0}
+	for _, a := range arg1 {
+		varargs = append(varargs, a)
+	}
+	m.ctrl.Call(m, "Errorf", varargs...)
+}
+
+// Errorf indicates an expected call of Errorf.
+func (mr *MockLoggerMockRecorder) Errorf(arg0 interface{}, arg1 ...interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	varargs := append([]interface{}{arg0}, arg1...)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Errorf", reflect.TypeOf((*MockLogger)(nil).Errorf), varargs...)
+}
+
+// Info mocks base method.
+func (m *MockLogger) Info(arg0 string) {
+	m.ctrl.T.Helper()
+	m.ctrl.Call(m, "Info", arg0)
+}
+
+// Info indicates an expected call of Info.
+func (mr *MockLoggerMockRecorder) Info(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Info", reflect.TypeOf((*MockLogger)(nil).Info), arg0)
+}

internal/amneziawg/netlinker.go

@@ -0,0 +1,36 @@
+package amneziawg
+
+import (
+	"net/netip"
+
+	"github.com/qdm12/gluetun/internal/netlink"
+)
+
+//go:generate mockgen -destination=netlinker_mock_test.go -package amneziawg . NetLinker
+
+type NetLinker interface {
+	AddrReplace(linkIndex uint32, addr netip.Prefix) error
+	Router
+	Ruler
+	Linker
+	IsWireguardSupported() (ok bool, err error)
+}
+
+type Router interface {
+	RouteList(family uint8) (routes []netlink.Route, err error)
+	RouteAdd(route netlink.Route) error
+}
+
+type Ruler interface {
+	RuleAdd(rule netlink.Rule) error
+	RuleDel(rule netlink.Rule) error
+}
+
+type Linker interface {
+	LinkAdd(link netlink.Link) (linkIndex uint32, err error)
+	LinkList() (links []netlink.Link, err error)
+	LinkByName(name string) (link netlink.Link, err error)
+	LinkSetUp(linkIndex uint32) error
+	LinkSetDown(linkIndex uint32) error
+	LinkDel(linkIndex uint32) error
+}

internal/amneziawg/netlinker_mock_test.go

@@ -0,0 +1,209 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/qdm12/gluetun/internal/amneziawg (interfaces: NetLinker)
+
+// Package amneziawg is a generated GoMock package.
+package amneziawg
+
+import (
+	netip "net/netip"
+	reflect "reflect"
+
+	gomock "github.com/golang/mock/gomock"
+	netlink "github.com/qdm12/gluetun/internal/netlink"
+)
+
+// MockNetLinker is a mock of NetLinker interface.
+type MockNetLinker struct {
+	ctrl     *gomock.Controller
+	recorder *MockNetLinkerMockRecorder
+}
+
+// MockNetLinkerMockRecorder is the mock recorder for MockNetLinker.
+type MockNetLinkerMockRecorder struct {
+	mock *MockNetLinker
+}
+
+// NewMockNetLinker creates a new mock instance.
+func NewMockNetLinker(ctrl *gomock.Controller) *MockNetLinker {
+	mock := &MockNetLinker{ctrl: ctrl}
+	mock.recorder = &MockNetLinkerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockNetLinker) EXPECT() *MockNetLinkerMockRecorder {
+	return m.recorder
+}
+
+// AddrReplace mocks base method.
+func (m *MockNetLinker) AddrReplace(arg0 uint32, arg1 netip.Prefix) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "AddrReplace", arg0, arg1)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// AddrReplace indicates an expected call of AddrReplace.
+func (mr *MockNetLinkerMockRecorder) AddrReplace(arg0, arg1 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "AddrReplace", reflect.TypeOf((*MockNetLinker)(nil).AddrReplace), arg0, arg1)
+}
+
+// IsWireguardSupported mocks base method.
+func (m *MockNetLinker) IsWireguardSupported() (bool, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "IsWireguardSupported")
+	ret0, _ := ret[0].(bool)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// IsWireguardSupported indicates an expected call of IsWireguardSupported.
+func (mr *MockNetLinkerMockRecorder) IsWireguardSupported() *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "IsWireguardSupported", reflect.TypeOf((*MockNetLinker)(nil).IsWireguardSupported))
+}
+
+// LinkAdd mocks base method.
+func (m *MockNetLinker) LinkAdd(arg0 netlink.Link) (uint32, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "LinkAdd", arg0)
+	ret0, _ := ret[0].(uint32)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// LinkAdd indicates an expected call of LinkAdd.
+func (mr *MockNetLinkerMockRecorder) LinkAdd(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "LinkAdd", reflect.TypeOf((*MockNetLinker)(nil).LinkAdd), arg0)
+}
+
+// LinkByName mocks base method.
+func (m *MockNetLinker) LinkByName(arg0 string) (netlink.Link, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "LinkByName", arg0)
+	ret0, _ := ret[0].(netlink.Link)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// LinkByName indicates an expected call of LinkByName.
+func (mr *MockNetLinkerMockRecorder) LinkByName(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "LinkByName", reflect.TypeOf((*MockNetLinker)(nil).LinkByName), arg0)
+}
+
+// LinkDel mocks base method.
+func (m *MockNetLinker) LinkDel(arg0 uint32) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "LinkDel", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// LinkDel indicates an expected call of LinkDel.
+func (mr *MockNetLinkerMockRecorder) LinkDel(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "LinkDel", reflect.TypeOf((*MockNetLinker)(nil).LinkDel), arg0)
+}
+
+// LinkList mocks base method.
+func (m *MockNetLinker) LinkList() ([]netlink.Link, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "LinkList")
+	ret0, _ := ret[0].([]netlink.Link)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// LinkList indicates an expected call of LinkList.
+func (mr *MockNetLinkerMockRecorder) LinkList() *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "LinkList", reflect.TypeOf((*MockNetLinker)(nil).LinkList))
+}
+
+// LinkSetDown mocks base method.
+func (m *MockNetLinker) LinkSetDown(arg0 uint32) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "LinkSetDown", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// LinkSetDown indicates an expected call of LinkSetDown.
+func (mr *MockNetLinkerMockRecorder) LinkSetDown(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "LinkSetDown", reflect.TypeOf((*MockNetLinker)(nil).LinkSetDown), arg0)
+}
+
+// LinkSetUp mocks base method.
+func (m *MockNetLinker) LinkSetUp(arg0 uint32) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "LinkSetUp", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// LinkSetUp indicates an expected call of LinkSetUp.
+func (mr *MockNetLinkerMockRecorder) LinkSetUp(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "LinkSetUp", reflect.TypeOf((*MockNetLinker)(nil).LinkSetUp), arg0)
+}
+
+// RouteAdd mocks base method.
+func (m *MockNetLinker) RouteAdd(arg0 netlink.Route) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "RouteAdd", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// RouteAdd indicates an expected call of RouteAdd.
+func (mr *MockNetLinkerMockRecorder) RouteAdd(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "RouteAdd", reflect.TypeOf((*MockNetLinker)(nil).RouteAdd), arg0)
+}
+
+// RouteList mocks base method.
+func (m *MockNetLinker) RouteList(arg0 byte) ([]netlink.Route, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "RouteList", arg0)
+	ret0, _ := ret[0].([]netlink.Route)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// RouteList indicates an expected call of RouteList.
+func (mr *MockNetLinkerMockRecorder) RouteList(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "RouteList", reflect.TypeOf((*MockNetLinker)(nil).RouteList), arg0)
+}
+
+// RuleAdd mocks base method.
+func (m *MockNetLinker) RuleAdd(arg0 netlink.Rule) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "RuleAdd", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// RuleAdd indicates an expected call of RuleAdd.
+func (mr *MockNetLinkerMockRecorder) RuleAdd(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "RuleAdd", reflect.TypeOf((*MockNetLinker)(nil).RuleAdd), arg0)
+}
+
+// RuleDel mocks base method.
+func (m *MockNetLinker) RuleDel(arg0 netlink.Rule) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "RuleDel", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// RuleDel indicates an expected call of RuleDel.
+func (mr *MockNetLinkerMockRecorder) RuleDel(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "RuleDel", reflect.TypeOf((*MockNetLinker)(nil).RuleDel), arg0)
+}

internal/amneziawg/run.go

@@ -0,0 +1,133 @@
+package amneziawg
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net"
+
+	amneziaconn "github.com/amnezia-vpn/amneziawg-go/conn"
+	amneziadevice "github.com/amnezia-vpn/amneziawg-go/device"
+	amneziatun "github.com/amnezia-vpn/amneziawg-go/tun"
+	"github.com/qdm12/gluetun/internal/cleanup"
+	"github.com/qdm12/gluetun/internal/wireguard"
+)
+
+var (
+	errTunNameMismatch = errors.New("TUN device name is mismatching")
+	errDeviceWaited    = errors.New("device waited for")
+)
+
+// Run runs the amneziawg interface and waits until the context is done, then it cleans up the
+// interface and returns any error that occurred during setup or waiting. It sends an error to
+// waitError if any error occurs during setup or waiting, otherwise it sends nil when the context
+// is done. It sends a signal to ready when the setup is complete and the interface is ready to use.
+// See https://github.com/amnezia-vpn/amneziawg-go/blob/master/main.go
+func (a *Amneziawg) Run(ctx context.Context, waitError chan<- error, ready chan<- struct{}) {
+	setup := func(ctx context.Context, cleanups *cleanup.Cleanups) (
+		linkIndex uint32, waitAndCleanup func() error, err error,
+	) {
+		return setupUserspace(ctx, a.settings.Wireguard.InterfaceName,
+			a.netlink, a.settings.Wireguard.MTU, cleanups, a.logger, a.settings)
+	}
+
+	wireguard.Run(ctx, waitError, ready, setup, a.settings.Wireguard, a.netlink, a.logger)
+}
+
+func setupUserspace(ctx context.Context,
+	interfaceName string, netLinker NetLinker, mtu uint32,
+	cleanups *cleanup.Cleanups, logger Logger,
+	settings Settings,
+) (
+	linkIndex uint32, waitAndCleanup func() error, err error,
+) {
+	tun, err := amneziatun.CreateTUN(interfaceName, int(mtu))
+	if err != nil {
+		return 0, nil, fmt.Errorf("creating TUN device: %w", err)
+	}
+
+	cleanups.Add("closing TUN device", 7, tun.Close)
+
+	tunName, err := tun.Name()
+	if err != nil {
+		return 0, nil, fmt.Errorf("getting created TUN device name: %w", err)
+	} else if tunName != interfaceName {
+		return 0, nil, fmt.Errorf("%w: expected %q and got %q",
+			errTunNameMismatch, interfaceName, tunName)
+	}
+
+	link, err := netLinker.LinkByName(interfaceName)
+	if err != nil {
+		return 0, nil, fmt.Errorf("finding link %s: %w", interfaceName, err)
+	}
+	cleanups.Add("deleting link", 5, func() error {
+		return netLinker.LinkDel(link.Index)
+	})
+
+	bind := amneziaconn.NewDefaultBind()
+	cleanups.Add("closing bind", 7, bind.Close)
+
+	deviceLogger := amneziadevice.Logger{
+		Verbosef: logger.Debugf,
+		Errorf:   logger.Errorf,
+	}
+	device := amneziadevice.NewDevice(tun, bind, &deviceLogger)
+
+	cleanups.Add("closing Wireguard device", 6, func() error {
+		device.Close()
+		return nil
+	})
+
+	uapiFile, err := wireguard.UAPIOpen(interfaceName)
+	if err != nil {
+		return 0, nil, fmt.Errorf("opening UAPI socket: %w", err)
+	}
+	cleanups.Add("closing UAPI file", 3, uapiFile.Close)
+
+	uapiListener, err := wireguard.UAPIListen(interfaceName, uapiFile)
+	if err != nil {
+		return 0, nil, fmt.Errorf("listening on UAPI socket: %w", err)
+	}
+	cleanups.Add("closing UAPI listener", 2, uapiListener.Close)
+
+	uapiConfig := settings.uapiConfig()
+	err = device.IpcSet(uapiConfig)
+	if err != nil {
+		return 0, nil, fmt.Errorf("setting amneziawg uapi config: %w", err)
+	}
+
+	// acceptAndHandle exits when uapiListener is closed
+	uapiAcceptErrorCh := make(chan error)
+	go acceptAndHandle(uapiListener, device, uapiAcceptErrorCh)
+	waitAndCleanup = func() error {
+		select {
+		case <-ctx.Done():
+			err = ctx.Err()
+		case err = <-uapiAcceptErrorCh:
+			close(uapiAcceptErrorCh)
+		case <-device.Wait():
+			err = errDeviceWaited
+		}
+
+		cleanups.Cleanup(logger)
+
+		<-uapiAcceptErrorCh // wait for acceptAndHandle to exit
+
+		return err
+	}
+
+	return link.Index, waitAndCleanup, nil
+}
+
+func acceptAndHandle(uapi net.Listener, device *amneziadevice.Device,
+	uapiAcceptErrorCh chan<- error,
+) {
+	for { // stopped by uapiFile.Close()
+		conn, err := uapi.Accept()
+		if err != nil {
+			uapiAcceptErrorCh <- err
+			return
+		}
+		go device.IpcHandle(conn)
+	}
+}

internal/amneziawg/settings.go

@@ -0,0 +1,69 @@
+package amneziawg
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/wireguard"
+)
+
+type Settings struct {
+	Wireguard       wireguard.Settings
+	JunkPacketCount uint16
+	JunkPacketMin   uint16
+	JunkPacketMax   uint16
+	PaddingS1       uint16
+	PaddingS2       uint16
+	PaddingS3       uint16
+	PaddingS4       uint16
+	HeaderH1        string
+	HeaderH2        string
+	HeaderH3        string
+	HeaderH4        string
+	InitPacketI1    string
+	InitPacketI2    string
+	InitPacketI3    string
+	InitPacketI4    string
+	InitPacketI5    string
+}
+
+func (s Settings) uapiConfig() string {
+	uintFields := map[string]uint16{
+		"jc":   s.JunkPacketCount,
+		"jmin": s.JunkPacketMin,
+		"jmax": s.JunkPacketMax,
+		"s1":   s.PaddingS1,
+		"s2":   s.PaddingS2,
+		"s3":   s.PaddingS3,
+		"s4":   s.PaddingS4,
+	}
+	stringFields := map[string]string{
+		"h1": s.HeaderH1,
+		"h2": s.HeaderH2,
+		"h3": s.HeaderH3,
+		"h4": s.HeaderH4,
+		"i1": s.InitPacketI1,
+		"i2": s.InitPacketI2,
+		"i3": s.InitPacketI3,
+		"i4": s.InitPacketI4,
+		"i5": s.InitPacketI5,
+	}
+	lines := make([]string, 0, len(uintFields)+len(stringFields))
+
+	for key, val := range uintFields {
+		lines = append(lines, fmt.Sprintf("%s=%d", key, val))
+	}
+
+	for key, val := range stringFields {
+		lines = append(lines, key+"="+val)
+	}
+	return strings.Join(lines, "\n")
+}
+
+func (s *Settings) SetDefaults() {
+	s.Wireguard.SetDefaults()
+}
+
+func (s *Settings) Check() error {
+	return s.Wireguard.Check()
+}

internal/boringpoll/boringpoll.go

@@ -0,0 +1,189 @@
+package boringpoll
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"math/rand"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/qdm12/gluetun/internal/configuration/settings"
+)
+
+type BoringPoll struct {
+	// Injected dependencies
+	client *http.Client
+	logger Logger
+
+	// Internal state
+	urlToData map[string]*urlData
+
+	// Internal signals and channels
+	cancel context.CancelFunc
+	done   *sync.WaitGroup
+	mutex  sync.Mutex
+}
+
+type urlData struct{}
+
+func New(client *http.Client, logger Logger, settings settings.BoringPoll) *BoringPoll {
+	urlToData := make(map[string]*urlData)
+	if *settings.GluetunCom {
+		urlToData["https://gluetun.com/wp-json"] = &urlData{}
+	}
+	return &BoringPoll{
+		client:    client,
+		logger:    logger,
+		urlToData: urlToData,
+	}
+}
+
+func (b *BoringPoll) Start() (runError <-chan error, err error) {
+	b.mutex.Lock()
+	defer b.mutex.Unlock()
+
+	if len(b.urlToData) == 0 {
+		return nil, nil //nolint:nilnil
+	}
+
+	const minPeriod = time.Minute
+	const maxPeriod = 5 * time.Minute
+	const logEveryBytes = 100 * 1000 * 1000 // 100 IEC MB
+
+	var ready, done sync.WaitGroup
+	b.done = &done
+	ready.Add(len(b.urlToData))
+	done.Add(len(b.urlToData))
+	ctx, cancel := context.WithCancel(context.Background())
+	b.cancel = cancel
+	for url := range b.urlToData {
+		go func(url string) {
+			defer done.Done()
+
+			b.logger.Infof("running against %s periodically between %s and %s "+
+				"and will log every %s downloaded",
+				url, minPeriod, maxPeriod, byteCountSI(logEveryBytes))
+			totalDownloaded := uint64(0)
+			lastDownloaded := uint64(0)
+			consecutiveFails := 0
+			const maxConsecutiveErrs = 3
+			const coolDownTimeout = time.Hour
+			timer := time.NewTimer(time.Hour)
+			var err error
+
+			ready.Done()
+			for {
+				timeout := minPeriod + time.Duration(rand.Int63n(int64(maxPeriod-minPeriod))) //nolint:gosec
+				if consecutiveFails >= maxConsecutiveErrs {
+					b.logger.Debugf("pausing poll to %s for %s due to %d consecutive errors, last error: %s",
+						url, coolDownTimeout, consecutiveFails, err)
+					timeout = coolDownTimeout
+				}
+				timer.Reset(timeout)
+				select {
+				case <-ctx.Done():
+					timer.Stop()
+					totalDownloaded += lastDownloaded
+					if totalDownloaded > 0 {
+						b.logger.Infof("stopping poll to %s, downloaded %s!", url, byteCountSI(totalDownloaded))
+					}
+					return
+				case <-timer.C:
+				}
+				var n int64
+				n, err = fetchURL(ctx, b.client, url)
+				if err != nil {
+					consecutiveFails++
+					continue
+				}
+				consecutiveFails = 0
+				totalDownloaded += uint64(n) //nolint:gosec
+				lastDownloaded += uint64(n)  //nolint:gosec
+				if lastDownloaded >= logEveryBytes {
+					b.logger.Infof("thanks for helping! You have downloaded %s from %s so far!",
+						byteCountSI(totalDownloaded), url)
+					lastDownloaded = 0
+				}
+			}
+		}(url)
+	}
+	return nil, nil //nolint:nilnil
+}
+
+func fetchURL(ctx context.Context, client *http.Client, url string) (downloaded int64, err error) {
+	const requestTimeout = 10 * time.Second
+	ctx, cancel := context.WithTimeout(ctx, requestTimeout)
+	defer cancel()
+	request, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		cancel()
+		return 0, err
+	}
+	request.Header.Set("Cache-Control", "no-cache, no-store, must-revalidate")
+	request.Header.Set("Pragma", "no-cache")
+	request.Header.Set("Expires", "0")
+	request.Header.Set("User-Agent", getRandomUserAgent())
+
+	response, err := client.Do(request)
+	if err != nil {
+		return 0, err
+	}
+	downloaded, err = io.Copy(io.Discard, response.Body)
+	_ = response.Body.Close()
+	if err != nil {
+		return 0, err
+	}
+	return downloaded, nil
+}
+
+func getRandomUserAgent() string {
+	//nolint:lll
+	userAgents := [...]string{
+		"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36",
+		"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36",
+		"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36",
+		"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:122.0) Gecko/20100101 Firefox/122.0",
+		"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.2.1 Safari/605.1.15",
+		"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Edge/121.0.0.0 Safari/537.36",
+		"Mozilla/5.0 (iPhone; CPU iPhone OS 17_2_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.2 Mobile/15E148 Safari/604.1",
+		"Mozilla/5.0 (iPad; CPU OS 17_2_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.2 Mobile/15E148 Safari/604.1",
+		"Mozilla/5.0 (Android 14; Mobile; rv:122.0) Gecko/122.0 Firefox/122.0",
+		"Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Mobile Safari/537.36",
+		"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36 OPR/106.0.0.0",
+		"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36 OPR/106.0.0.0",
+		"Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)",
+		"Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)",
+	}
+	return userAgents[rand.Intn(len(userAgents))] //nolint:gosec
+}
+
+func (b *BoringPoll) Stop() error {
+	b.mutex.Lock()
+	defer b.mutex.Unlock()
+
+	if b.cancel == nil {
+		return nil
+	}
+	b.cancel()
+	b.done.Wait()
+	b.cancel = nil
+	b.done = nil
+	return nil
+}
+
+func byteCountSI(b uint64) string {
+	const unit = 1000
+	if b < unit {
+		return fmt.Sprintf("%dB", b)
+	}
+
+	div, exp := uint64(unit), 0
+	for n := b / unit; n >= unit; n /= unit {
+		div *= unit
+		exp++
+	}
+
+	return fmt.Sprintf("%.1f%cB", float64(b)/float64(div), "kMGTPE"[exp])
+}

internal/boringpoll/interfaces.go

@@ -0,0 +1,6 @@
+package boringpoll
+
+type Logger interface {
+	Infof(format string, args ...any)
+	Debugf(format string, args ...any)
+}

internal/cleanup/cleanup.go

@@ -0,0 +1,51 @@
+package cleanup
+
+import "sort"
+
+type Cleanups []cleanup
+
+type cleanup struct {
+	operation  string
+	orderIndex uint
+	cleanup    func() error
+	done       bool
+}
+
+// Add adds a cleanup function to the list of cleanups, with a description of the
+// operation being cleaned up, and an order index that determines the order in which
+// the cleanup functions are run. The lower the order index, the earlier the cleanup
+// function is run.
+func (c *Cleanups) Add(operation string, orderIndex uint,
+	cleanupFunc func() error,
+) {
+	closer := cleanup{
+		operation:  operation,
+		orderIndex: orderIndex,
+		cleanup:    cleanupFunc,
+	}
+	*c = append(*c, closer)
+}
+
+// Cleanup runs the cleanup functions in the order of their orderIndex,
+// and logs any error that occurs during cleanup.
+// It can also be re-called in case a cleanup fails, and already cleaned up
+// functions will not be re-run.
+func (c *Cleanups) Cleanup(logger Logger) {
+	closers := *c
+
+	sort.Slice(closers, func(i, j int) bool {
+		return closers[i].orderIndex < closers[j].orderIndex
+	})
+
+	for i, closer := range closers {
+		if closer.done {
+			continue
+		}
+		closers[i].done = true
+		logger.Debug(closer.operation + "...")
+		err := closer.cleanup()
+		if err != nil {
+			logger.Error("failed " + closer.operation + ": " + err.Error())
+		}
+	}
+}

internal/cleanup/cleanup_test.go

@@ -0,0 +1,57 @@
+package cleanup
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/golang/mock/gomock"
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_Cleanups(t *testing.T) {
+	t.Parallel()
+
+	ctrl := gomock.NewController(t)
+
+	var ACloseCalled, BCloseCalled, CCloseCalled bool
+	var (
+		AErr error
+		BErr = errors.New("B failed")
+		CErr = errors.New("C failed")
+	)
+
+	var cleanups Cleanups
+	cleanups.Add("cleaning up A", 5, func() error {
+		ACloseCalled = true
+		return AErr
+	})
+
+	cleanups.Add("cleaning up B", 3, func() error {
+		BCloseCalled = true
+		return BErr
+	})
+
+	cleanups.Add("cleaning up C", 2, func() error {
+		CCloseCalled = true
+		return CErr
+	})
+
+	logger := NewMockLogger(ctrl)
+	prevCall := logger.EXPECT().Debug("cleaning up C...")
+	prevCall = logger.EXPECT().Error("failed cleaning up C: C failed").After(prevCall)
+	prevCall = logger.EXPECT().Debug("cleaning up B...").After(prevCall)
+	prevCall = logger.EXPECT().Error("failed cleaning up B: B failed").After(prevCall)
+	logger.EXPECT().Debug("cleaning up A...").After(prevCall)
+
+	cleanups.Cleanup(logger)
+
+	cleanups.Cleanup(logger) // run twice should not close already closed
+
+	for _, cleanup := range cleanups {
+		assert.True(t, cleanup.done)
+	}
+
+	assert.True(t, ACloseCalled)
+	assert.True(t, BCloseCalled)
+	assert.True(t, CCloseCalled)
+}

internal/cleanup/interfaces.go

@@ -0,0 +1,6 @@
+package cleanup
+
+type Logger interface {
+	Debug(string)
+	Error(string)
+}

internal/cleanup/mocks_generate_test.go

@@ -0,0 +1,3 @@
+package cleanup
+
+//go:generate mockgen -destination=mocks_test.go -package=$GOPACKAGE . Logger

internal/cleanup/mocks_test.go

@@ -0,0 +1,58 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/qdm12/gluetun/internal/cleanup (interfaces: Logger)
+
+// Package cleanup is a generated GoMock package.
+package cleanup
+
+import (
+	reflect "reflect"
+
+	gomock "github.com/golang/mock/gomock"
+)
+
+// MockLogger is a mock of Logger interface.
+type MockLogger struct {
+	ctrl     *gomock.Controller
+	recorder *MockLoggerMockRecorder
+}
+
+// MockLoggerMockRecorder is the mock recorder for MockLogger.
+type MockLoggerMockRecorder struct {
+	mock *MockLogger
+}
+
+// NewMockLogger creates a new mock instance.
+func NewMockLogger(ctrl *gomock.Controller) *MockLogger {
+	mock := &MockLogger{ctrl: ctrl}
+	mock.recorder = &MockLoggerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockLogger) EXPECT() *MockLoggerMockRecorder {
+	return m.recorder
+}
+
+// Debug mocks base method.
+func (m *MockLogger) Debug(arg0 string) {
+	m.ctrl.T.Helper()
+	m.ctrl.Call(m, "Debug", arg0)
+}
+
+// Debug indicates an expected call of Debug.
+func (mr *MockLoggerMockRecorder) Debug(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Debug", reflect.TypeOf((*MockLogger)(nil).Debug), arg0)
+}
+
+// Error mocks base method.
+func (m *MockLogger) Error(arg0 string) {
+	m.ctrl.T.Helper()
+	m.ctrl.Call(m, "Error", arg0)
+}
+
+// Error indicates an expected call of Error.
+func (mr *MockLoggerMockRecorder) Error(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Error", reflect.TypeOf((*MockLogger)(nil).Error), arg0)
+}

internal/cli/noopfirewall.go

@@ -0,0 +1,14 @@
+package cli
+
+import (
+	"context"
+	"net/netip"
+)
+
+type noopFirewall struct{}
+
+func (f *noopFirewall) AcceptOutput(_ context.Context, _, _ string, _ netip.Addr,
+	_ uint16, _ bool,
+) (err error) {
+	return nil
+}

internal/cli/openvpnconfig.go

@@ -11,6 +11,7 @@ import (
 	"github.com/qdm12/gluetun/internal/configuration/settings"
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gluetun/internal/netlink"
 	"github.com/qdm12/gluetun/internal/openvpn/extract"
 	"github.com/qdm12/gluetun/internal/provider"
 	"github.com/qdm12/gluetun/internal/storage"
@@ -40,7 +41,9 @@ type IPFetcher interface {
 }
 
 type IPv6Checker interface {
-	IsIPv6Supported() (supported bool, err error)
+	FindIPv6SupportLevel(ctx context.Context,
+		checkAddresses []netip.AddrPort, firewall netlink.Firewall,
+	) (level netlink.IPv6SupportLevel, err error)
 }
 
 func (c *CLI) OpenvpnConfig(logger OpenvpnConfigLogger, reader *reader.Reader,
@@ -58,12 +61,14 @@ func (c *CLI) OpenvpnConfig(logger OpenvpnConfigLogger, reader *reader.Reader,
 	}
 	allSettings.SetDefaults()
 
-	ipv6Supported, err := ipv6Checker.IsIPv6Supported()
+	ipv6SupportLevel, err := ipv6Checker.FindIPv6SupportLevel(context.Background(),
+		allSettings.IPv6.CheckAddresses, &noopFirewall{})
 	if err != nil {
 		return fmt.Errorf("checking for IPv6 support: %w", err)
 	}
 
-	if err = allSettings.Validate(storage, ipv6Supported, logger); err != nil {
+	err = allSettings.Validate(storage, ipv6SupportLevel.IsSupported(), logger)
+	if err != nil {
 		return fmt.Errorf("validating settings: %w", err)
 	}
 
@@ -79,13 +84,13 @@ func (c *CLI) OpenvpnConfig(logger OpenvpnConfigLogger, reader *reader.Reader,
 		unzipper, parallelResolver, ipFetcher, openvpnFileExtractor, allSettings.Updater)
 	providerConf := providers.Get(allSettings.VPN.Provider.Name)
 	connection, err := providerConf.GetConnection(
-		allSettings.VPN.Provider.ServerSelection, ipv6Supported)
+		allSettings.VPN.Provider.ServerSelection, ipv6SupportLevel == netlink.IPv6Internet)
 	if err != nil {
 		return err
 	}
 
 	lines := providerConf.OpenVPNConfig(connection,
-		allSettings.VPN.OpenVPN, ipv6Supported)
+		allSettings.VPN.OpenVPN, ipv6SupportLevel.IsSupported())
 
 	fmt.Println(strings.Join(lines, "\n"))
 	return nil

internal/cli/update.go

@@ -10,6 +10,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/qdm12/dns/v2/pkg/doh"
+	dnsprovider "github.com/qdm12/dns/v2/pkg/provider"
 	"github.com/qdm12/gluetun/internal/configuration/settings"
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/constants/providers"
@@ -38,12 +40,12 @@ type UpdaterLogger interface {
 func (c *CLI) Update(ctx context.Context, args []string, logger UpdaterLogger) error {
 	options := settings.Updater{}
 	var endUserMode, maintainerMode, updateAll bool
-	var csvProviders, ipToken, protonUsername, protonEmail, protonPassword string
+	var dnsServer, csvProviders, ipToken, protonUsername, protonEmail, protonPassword string
 	flagSet := flag.NewFlagSet("update", flag.ExitOnError)
 	flagSet.BoolVar(&endUserMode, "enduser", false, "Write results to /gluetun/servers.json (for end users)")
 	flagSet.BoolVar(&maintainerMode, "maintainer", false,
 		"Write results to ./internal/storage/servers.json to modify the program (for maintainers)")
-	flagSet.StringVar(&options.DNSAddress, "dns", "8.8.8.8", "DNS resolver address to use")
+	flagSet.StringVar(&dnsServer, "dns", "", "no longer used, your DNS will use DoH with Cloudflare and Google")
 	const defaultMinRatio = 0.8
 	flagSet.Float64Var(&options.MinRatio, "minratio", defaultMinRatio,
 		"Minimum ratio of servers to find for the update to succeed")
@@ -58,6 +60,10 @@ func (c *CLI) Update(ctx context.Context, args []string, logger UpdaterLogger) e
 		return err
 	}
 
+	if dnsServer != "" {
+		logger.Warn("The -dns flag is no longer used, your DNS will use DoH with Cloudflare and Google")
+	}
+
 	if !endUserMode && !maintainerMode {
 		return fmt.Errorf("%w", ErrModeUnspecified)
 	}
@@ -97,10 +103,21 @@ func (c *CLI) Update(ctx context.Context, args []string, logger UpdaterLogger) e
 		return fmt.Errorf("creating servers storage: %w", err)
 	}
 
+	dohSettings := doh.Settings{
+		UpstreamResolvers: []dnsprovider.Provider{
+			dnsprovider.Cloudflare(),
+			dnsprovider.Google(),
+		},
+	}
+	dnsDialer, err := doh.New(dohSettings)
+	if err != nil {
+		return fmt.Errorf("creating DoH dialer: %w", err)
+	}
+
 	const clientTimeout = 10 * time.Second
 	httpClient := &http.Client{Timeout: clientTimeout}
 	unzipper := unzip.New(httpClient)
-	parallelResolver := resolver.NewParallelResolver(options.DNSAddress)
+	parallelResolver := resolver.NewParallelResolver(dnsDialer)
 	nameTokenPairs := []api.NameToken{
 		{Name: string(api.IPInfo), Token: ipToken},
 		{Name: string(api.IP2Location)},

internal/command/interfaces.go

@@ -0,0 +1,6 @@
+package command
+
+type Logger interface {
+	Info(s string)
+	Error(s string)
+}

internal/command/split.go

@@ -9,13 +9,13 @@ import (
 )
 
 var (
-	ErrCommandEmpty            = errors.New("command is empty")
-	ErrSingleQuoteUnterminated = errors.New("unterminated single-quoted string")
-	ErrDoubleQuoteUnterminated = errors.New("unterminated double-quoted string")
-	ErrEscapeUnterminated      = errors.New("unterminated backslash-escape")
+	errCommandEmpty            = errors.New("command is empty")
+	errSingleQuoteUnterminated = errors.New("unterminated single-quoted string")
+	errDoubleQuoteUnterminated = errors.New("unterminated double-quoted string")
+	errEscapeUnterminated      = errors.New("unterminated backslash-escape")
 )
 
-// Split splits a command string into a slice of arguments.
+// split splits a command string into a slice of arguments.
 // This is especially important for commands such as:
 // /bin/sh -c "echo hello"
 // which should be split into: ["/bin/sh", "-c", "echo hello"]
@@ -23,9 +23,9 @@ var (
 // It does not support:
 // - the $" quoting style.
 // - expansion (brace, shell or pathname).
-func Split(command string) (words []string, err error) {
+func split(command string) (words []string, err error) {
 	if command == "" {
-		return nil, fmt.Errorf("%w", ErrCommandEmpty)
+		return nil, fmt.Errorf("%w", errCommandEmpty)
 	}
 
 	const bufferSize = 1024
@@ -42,7 +42,7 @@ func Split(command string) (words []string, err error) {
 		case character == '\\':
 			// Look ahead to eventually skip an escaped newline
 			if command[startIndex+runeSize:] == "" {
-				return nil, fmt.Errorf("%w: %q", ErrEscapeUnterminated, command)
+				return nil, fmt.Errorf("%w: %q", errEscapeUnterminated, command)
 			}
 			character, runeSize := utf8.DecodeRuneInString(command[startIndex+runeSize:])
 			if character == '\n' {
@@ -119,7 +119,7 @@ func handleDoubleQuoted(input string, startIndex int, buffer *bytes.Buffer) (
 			startIndex = cursor
 		}
 	}
-	return "", 0, fmt.Errorf("%w", ErrDoubleQuoteUnterminated)
+	return "", 0, fmt.Errorf("%w", errDoubleQuoteUnterminated)
 }
 
 func handleSingleQuoted(input string, startIndex int, buffer *bytes.Buffer) (
@@ -127,7 +127,7 @@ func handleSingleQuoted(input string, startIndex int, buffer *bytes.Buffer) (
 ) {
 	closingQuoteIndex := strings.IndexRune(input[startIndex:], '\'')
 	if closingQuoteIndex == -1 {
-		return "", 0, fmt.Errorf("%w", ErrSingleQuoteUnterminated)
+		return "", 0, fmt.Errorf("%w", errSingleQuoteUnterminated)
 	}
 	buffer.WriteString(input[startIndex : startIndex+closingQuoteIndex])
 	const singleQuoteRuneLength = 1
@@ -139,7 +139,7 @@ func handleEscaped(input string, startIndex int, buffer *bytes.Buffer) (
 	word string, newStartIndex int, err error,
 ) {
 	if input[startIndex:] == "" {
-		return "", 0, fmt.Errorf("%w", ErrEscapeUnterminated)
+		return "", 0, fmt.Errorf("%w", errEscapeUnterminated)
 	}
 	character, runeLength := utf8.DecodeRuneInString(input[startIndex:])
 	if character != '\n' { // backslash-escaped newline is ignored

internal/command/split_test.go

@@ -6,7 +6,7 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func Test_Split(t *testing.T) {
+func Test_split(t *testing.T) {
 	t.Parallel()
 
 	testCases := map[string]struct {
@@ -17,7 +17,7 @@ func Test_Split(t *testing.T) {
 	}{
 		"empty": {
 			command:    "",
-			errWrapped: ErrCommandEmpty,
+			errWrapped: errCommandEmpty,
 			errMessage: "command is empty",
 		},
 		"concrete_sh_command": {
@@ -74,22 +74,22 @@ func Test_Split(t *testing.T) {
 		},
 		"unterminated_single_quote": {
 			command:    "'abc'\\''def",
-			errWrapped: ErrSingleQuoteUnterminated,
+			errWrapped: errSingleQuoteUnterminated,
 			errMessage: `splitting word in "'abc'\\''def": unterminated single-quoted string`,
 		},
 		"unterminated_double_quote": {
 			command:    "\"abc'def",
-			errWrapped: ErrDoubleQuoteUnterminated,
+			errWrapped: errDoubleQuoteUnterminated,
 			errMessage: `splitting word in "\"abc'def": unterminated double-quoted string`,
 		},
 		"unterminated_escape": {
 			command:    "abc\\",
-			errWrapped: ErrEscapeUnterminated,
+			errWrapped: errEscapeUnterminated,
 			errMessage: `splitting word in "abc\\": unterminated backslash-escape`,
 		},
 		"unterminated_escape_only": {
 			command:    "   \\",
-			errWrapped: ErrEscapeUnterminated,
+			errWrapped: errEscapeUnterminated,
 			errMessage: `unterminated backslash-escape: "   \\"`,
 		},
 	}
@@ -98,7 +98,7 @@ func Test_Split(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 
-			words, err := Split(testCase.command)
+			words, err := split(testCase.command)
 
 			assert.Equal(t, testCase.words, words)
 			assert.ErrorIs(t, err, testCase.errWrapped)

internal/command/startnlog.go

@@ -0,0 +1,48 @@
+package command
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+)
+
+func (c *Cmder) RunAndLog(ctx context.Context, command string, logger Logger) (err error) {
+	args, err := split(command)
+	if err != nil {
+		return fmt.Errorf("parsing command: %w", err)
+	}
+
+	cmd := exec.CommandContext(ctx, args[0], args[1:]...) // #nosec G204
+	stdout, stderr, waitError, err := c.Start(cmd)
+	if err != nil {
+		return err
+	}
+
+	streamCtx, streamCancel := context.WithCancel(context.Background())
+	streamDone := make(chan struct{})
+	go streamLines(streamCtx, streamDone, logger, stdout, stderr)
+
+	err = <-waitError
+	streamCancel()
+	<-streamDone
+	return err
+}
+
+func streamLines(ctx context.Context, done chan<- struct{},
+	logger Logger, stdout, stderr <-chan string,
+) {
+	defer close(done)
+
+	var line string
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case line = <-stdout:
+			logger.Info(line)
+		case line = <-stderr:
+			logger.Error(line)
+		}
+	}
+}

internal/configuration/settings/amneziawg.go

@@ -0,0 +1,243 @@
+package settings
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/qdm12/gosettings"
+	"github.com/qdm12/gosettings/reader"
+	"github.com/qdm12/gotree"
+)
+
+type AmneziaWg struct {
+	// Wireguard contains the configuration for Wireguard, given
+	// AmneziaWg is based on Wireguard
+	Wireguard       Wireguard `json:"wireguard"`
+	JunkPacketCount *uint16   `json:"junk_packet_count"`
+	JunkPacketMin   *uint16   `json:"junk_packet_min"`
+	JunkPacketMax   *uint16   `json:"junk_packet_max"`
+	PaddingS1       *uint16   `json:"padding_s1"`
+	PaddingS2       *uint16   `json:"padding_s2"`
+	PaddingS3       *uint16   `json:"padding_s3"`
+	PaddingS4       *uint16   `json:"padding_s4"`
+	HeaderH1        *string   `json:"header_h1"`
+	HeaderH2        *string   `json:"header_h2"`
+	HeaderH3        *string   `json:"header_h3"`
+	HeaderH4        *string   `json:"header_h4"`
+	InitPacketI1    *string   `json:"init_packet_i1"`
+	InitPacketI2    *string   `json:"init_packet_i2"`
+	InitPacketI3    *string   `json:"init_packet_i3"`
+	InitPacketI4    *string   `json:"init_packet_i4"`
+	InitPacketI5    *string   `json:"init_packet_i5"`
+}
+
+func (a *AmneziaWg) read(r *reader.Reader) (err error) {
+	const amneziawg = true
+	err = a.Wireguard.read(r, amneziawg)
+	if err != nil {
+		return err // do not wrap this error
+	}
+
+	uint16Fields := map[string]**uint16{
+		"AMNEZIAWG_JC":   &a.JunkPacketCount,
+		"AMNEZIAWG_JMIN": &a.JunkPacketMin,
+		"AMNEZIAWG_JMAX": &a.JunkPacketMax,
+		"AMNEZIAWG_S1":   &a.PaddingS1,
+		"AMNEZIAWG_S2":   &a.PaddingS2,
+		"AMNEZIAWG_S3":   &a.PaddingS3,
+		"AMNEZIAWG_S4":   &a.PaddingS4,
+	}
+	for key, dst := range uint16Fields {
+		*dst, err = r.Uint16Ptr(key)
+		if err != nil {
+			return err
+		}
+	}
+	stringFields := map[string]**string{
+		"AMNEZIAWG_H1": &a.HeaderH1,
+		"AMNEZIAWG_H2": &a.HeaderH2,
+		"AMNEZIAWG_H3": &a.HeaderH3,
+		"AMNEZIAWG_H4": &a.HeaderH4,
+		"AMNEZIAWG_I1": &a.InitPacketI1,
+		"AMNEZIAWG_I2": &a.InitPacketI2,
+		"AMNEZIAWG_I3": &a.InitPacketI3,
+		"AMNEZIAWG_I4": &a.InitPacketI4,
+		"AMNEZIAWG_I5": &a.InitPacketI5,
+	}
+	opt := reader.ForceLowercase(false)
+	for key, dst := range stringFields {
+		*dst = r.Get(key, opt)
+	}
+	return nil
+}
+
+func (a AmneziaWg) copy() (copied AmneziaWg) {
+	return AmneziaWg{
+		Wireguard:       a.Wireguard.copy(),
+		JunkPacketCount: gosettings.CopyPointer(a.JunkPacketCount),
+		JunkPacketMin:   gosettings.CopyPointer(a.JunkPacketMin),
+		JunkPacketMax:   gosettings.CopyPointer(a.JunkPacketMax),
+		PaddingS1:       gosettings.CopyPointer(a.PaddingS1),
+		PaddingS2:       gosettings.CopyPointer(a.PaddingS2),
+		PaddingS3:       gosettings.CopyPointer(a.PaddingS3),
+		PaddingS4:       gosettings.CopyPointer(a.PaddingS4),
+		HeaderH1:        gosettings.CopyPointer(a.HeaderH1),
+		HeaderH2:        gosettings.CopyPointer(a.HeaderH2),
+		HeaderH3:        gosettings.CopyPointer(a.HeaderH3),
+		HeaderH4:        gosettings.CopyPointer(a.HeaderH4),
+		InitPacketI1:    gosettings.CopyPointer(a.InitPacketI1),
+		InitPacketI2:    gosettings.CopyPointer(a.InitPacketI2),
+		InitPacketI3:    gosettings.CopyPointer(a.InitPacketI3),
+		InitPacketI4:    gosettings.CopyPointer(a.InitPacketI4),
+		InitPacketI5:    gosettings.CopyPointer(a.InitPacketI5),
+	}
+}
+
+func (a *AmneziaWg) overrideWith(other AmneziaWg) {
+	a.Wireguard.overrideWith(other.Wireguard)
+	a.JunkPacketCount = gosettings.OverrideWithPointer(a.JunkPacketCount, other.JunkPacketCount)
+	a.JunkPacketMin = gosettings.OverrideWithPointer(a.JunkPacketMin, other.JunkPacketMin)
+	a.JunkPacketMax = gosettings.OverrideWithPointer(a.JunkPacketMax, other.JunkPacketMax)
+	a.PaddingS1 = gosettings.OverrideWithPointer(a.PaddingS1, other.PaddingS1)
+	a.PaddingS2 = gosettings.OverrideWithPointer(a.PaddingS2, other.PaddingS2)
+	a.PaddingS3 = gosettings.OverrideWithPointer(a.PaddingS3, other.PaddingS3)
+	a.PaddingS4 = gosettings.OverrideWithPointer(a.PaddingS4, other.PaddingS4)
+	a.HeaderH1 = gosettings.OverrideWithPointer(a.HeaderH1, other.HeaderH1)
+	a.HeaderH2 = gosettings.OverrideWithPointer(a.HeaderH2, other.HeaderH2)
+	a.HeaderH3 = gosettings.OverrideWithPointer(a.HeaderH3, other.HeaderH3)
+	a.HeaderH4 = gosettings.OverrideWithPointer(a.HeaderH4, other.HeaderH4)
+	a.InitPacketI1 = gosettings.OverrideWithPointer(a.InitPacketI1, other.InitPacketI1)
+	a.InitPacketI2 = gosettings.OverrideWithPointer(a.InitPacketI2, other.InitPacketI2)
+	a.InitPacketI3 = gosettings.OverrideWithPointer(a.InitPacketI3, other.InitPacketI3)
+	a.InitPacketI4 = gosettings.OverrideWithPointer(a.InitPacketI4, other.InitPacketI4)
+	a.InitPacketI5 = gosettings.OverrideWithPointer(a.InitPacketI5, other.InitPacketI5)
+}
+
+func (a *AmneziaWg) setDefaults(vpnProvider string) {
+	a.Wireguard.setDefaults(vpnProvider)
+	a.Wireguard.Implementation = "userspace" // unused except in logs
+	a.JunkPacketCount = gosettings.DefaultPointer(a.JunkPacketCount, 0)
+	a.JunkPacketMin = gosettings.DefaultPointer(a.JunkPacketMin, 0)
+	a.JunkPacketMax = gosettings.DefaultPointer(a.JunkPacketMax, 0)
+	a.PaddingS1 = gosettings.DefaultPointer(a.PaddingS1, 0)
+	a.PaddingS2 = gosettings.DefaultPointer(a.PaddingS2, 0)
+	a.PaddingS3 = gosettings.DefaultPointer(a.PaddingS3, 0)
+	a.PaddingS4 = gosettings.DefaultPointer(a.PaddingS4, 0)
+	a.HeaderH1 = gosettings.DefaultPointer(a.HeaderH1, "")
+	a.HeaderH2 = gosettings.DefaultPointer(a.HeaderH2, "")
+	a.HeaderH3 = gosettings.DefaultPointer(a.HeaderH3, "")
+	a.HeaderH4 = gosettings.DefaultPointer(a.HeaderH4, "")
+	a.InitPacketI1 = gosettings.DefaultPointer(a.InitPacketI1, "")
+	a.InitPacketI2 = gosettings.DefaultPointer(a.InitPacketI2, "")
+	a.InitPacketI3 = gosettings.DefaultPointer(a.InitPacketI3, "")
+	a.InitPacketI4 = gosettings.DefaultPointer(a.InitPacketI4, "")
+	a.InitPacketI5 = gosettings.DefaultPointer(a.InitPacketI5, "")
+}
+
+func (a AmneziaWg) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("AmneziaWG settings:")
+	node.AppendNode(a.Wireguard.toLinesNode())
+
+	uintFields := []struct {
+		key string
+		val *uint16
+	}{
+		{"JC", a.JunkPacketCount},
+		{"JMIN", a.JunkPacketMin},
+		{"JMAX", a.JunkPacketMax},
+		{"S1", a.PaddingS1},
+		{"S2", a.PaddingS2},
+		{"S3", a.PaddingS3},
+		{"S4", a.PaddingS4},
+	}
+	for _, f := range uintFields {
+		node.Appendf("%s: %d", f.key, *f.val)
+	}
+
+	stringFields := []struct {
+		key string
+		val *string
+	}{
+		{"H1", a.HeaderH1},
+		{"H2", a.HeaderH2},
+		{"H3", a.HeaderH3},
+		{"H4", a.HeaderH4},
+		{"I1", a.InitPacketI1},
+		{"I2", a.InitPacketI2},
+		{"I3", a.InitPacketI3},
+		{"I4", a.InitPacketI4},
+		{"I5", a.InitPacketI5},
+	}
+	for _, f := range stringFields {
+		node.Appendf("%s: %s", f.key, *f.val)
+	}
+
+	return node
+}
+
+var (
+	ErrAmenziawgImplementationNotValid = errors.New("AmneziaWG implementation is not valid")
+	ErrJunkPacketBounds                = errors.New("junk packet minimum must be lower than or equal to maximum")
+	ErrJunkPacketMinMaxNotSet          = errors.New("junk packet min and max must be set when junk packet count is set")
+	ErrJunkPacketCountNotSet           = errors.New("junk packet count must be set when junk packet min or max is set")
+	ErrHeaderRangeMalformed            = errors.New("header range is malformed")
+)
+
+func (a AmneziaWg) validate(vpnProvider string, ipv6Supported bool) error {
+	const amneziaWG = true
+	err := a.Wireguard.validate(vpnProvider, ipv6Supported, amneziaWG)
+	if err != nil {
+		return fmt.Errorf("wireguard settings: %w", err)
+	}
+
+	if *a.JunkPacketCount == 0 {
+		if *a.JunkPacketMin != 0 || *a.JunkPacketMax != 0 {
+			return fmt.Errorf("%w: jc=%d and jmin=%d and jmax=%d",
+				ErrJunkPacketCountNotSet, a.JunkPacketCount, *a.JunkPacketMin, *a.JunkPacketMax)
+		}
+	} else {
+		if *a.JunkPacketMin == 0 || *a.JunkPacketMax == 0 {
+			return fmt.Errorf("%w: jc=%d and jmin=%d and jmax=%d",
+				ErrJunkPacketMinMaxNotSet, a.JunkPacketCount, *a.JunkPacketMin, *a.JunkPacketMax)
+		} else if *a.JunkPacketMin > *a.JunkPacketMax {
+			return fmt.Errorf("%w: jmin=%d and jmax=%d",
+				ErrJunkPacketBounds, *a.JunkPacketMin, *a.JunkPacketMax)
+		}
+	}
+
+	nameToHeaderRange := map[string]string{
+		"h1": *a.HeaderH1,
+		"h2": *a.HeaderH2,
+		"h3": *a.HeaderH3,
+		"h4": *a.HeaderH4,
+	}
+	for name, headerRange := range nameToHeaderRange {
+		if headerRange == "" {
+			continue
+		}
+		fields := strings.Split(headerRange, "-")
+		switch len(fields) {
+		case 1:
+			_, err := strconv.Atoi(fields[0])
+			if err != nil {
+				return fmt.Errorf("%w: %s value %s is not a number",
+					ErrHeaderRangeMalformed, name, headerRange)
+			}
+		case 2: //nolint:mnd
+			for _, field := range fields {
+				_, err := strconv.Atoi(field)
+				if err != nil {
+					return fmt.Errorf("%w: %s value %s is not a valid range",
+						ErrHeaderRangeMalformed, name, headerRange)
+				}
+			}
+		default:
+			return fmt.Errorf("%w: %s value %s must be in the form n or n-m",
+				ErrHeaderRangeMalformed, name, headerRange)
+		}
+	}
+
+	return nil
+}

internal/configuration/settings/boringpoll.go

@@ -0,0 +1,51 @@
+package settings
+
+import (
+	"github.com/qdm12/gosettings"
+	"github.com/qdm12/gosettings/reader"
+	"github.com/qdm12/gotree"
+)
+
+type BoringPoll struct {
+	GluetunCom *bool
+}
+
+func (b BoringPoll) validate() error {
+	return nil
+}
+
+func (b BoringPoll) Copy() BoringPoll {
+	return BoringPoll{
+		GluetunCom: gosettings.CopyPointer(b.GluetunCom),
+	}
+}
+
+func (b *BoringPoll) overrideWith(other BoringPoll) {
+	b.GluetunCom = gosettings.OverrideWithPointer(b.GluetunCom, other.GluetunCom)
+}
+
+func (b *BoringPoll) setDefaults() {
+	b.GluetunCom = gosettings.DefaultPointer(b.GluetunCom, false)
+}
+
+func (b BoringPoll) String() string {
+	return b.toLinesNode().String()
+}
+
+func (b BoringPoll) toLinesNode() *gotree.Node {
+	if !*b.GluetunCom {
+		return nil
+	}
+
+	node := gotree.New("Boring-poll settings:")
+	node.Append("gluetun.com: on")
+	return node
+}
+
+func (b *BoringPoll) read(r *reader.Reader) (err error) {
+	b.GluetunCom, err = r.BoolPtr("BORINGPOLL_GLUETUNCOM")
+	if err != nil {
+		return err
+	}
+	return nil
+}

internal/configuration/settings/deprecated.go

@@ -14,6 +14,10 @@ func readObsolete(r *reader.Reader) (warnings []string) {
 		"DOT_VALIDATION_LOGLEVEL":      "DOT_VALIDATION_LOGLEVEL is obsolete because DNSSEC validation is not implemented.",
 		"HEALTH_VPN_DURATION_INITIAL":  "HEALTH_VPN_DURATION_INITIAL is obsolete",
 		"HEALTH_VPN_DURATION_ADDITION": "HEALTH_VPN_DURATION_ADDITION is obsolete",
+		"DNS_SERVER":                   "DNS_SERVER is obsolete because the forwarding server is always enabled.",
+		"DOT":                          "DOT is obsolete because the forwarding server is always enabled.",
+		"DNS_KEEP_NAMESERVER": "DNS_KEEP_NAMESERVER is obsolete because the forwarding server is always used and " +
+			"forwards local names to private DNS resolvers found in /etc/resolv.conf",
 	}
 	sortedKeys := maps.Keys(keyToMessage)
 	slices.Sort(sortedKeys)

internal/configuration/settings/dns.go

@@ -13,20 +13,25 @@ import (
 	"github.com/qdm12/gotree"
 )
 
+const (
+	DNSUpstreamTypeDot   = "dot"
+	DNSUpstreamTypeDoh   = "doh"
+	DNSUpstreamTypePlain = "plain"
+)
+
 // DNS contains settings to configure DNS.
 type DNS struct {
-	// ServerEnabled is true if the server should be running
-	// and used. It defaults to true, and cannot be nil
-	// in the internal state.
-	ServerEnabled *bool
-	// UpstreamType can be dot or plain, and defaults to dot.
+	// UpstreamType can be [DNSUpstreamTypeDot], [DNSUpstreamTypeDoh]
+	// or [DNSUpstreamTypePlain]. It defaults to [DNSUpstreamTypeDot].
 	UpstreamType string `json:"upstream_type"`
 	// UpdatePeriod is the period to update DNS block lists.
 	// It can be set to 0 to disable the update.
 	// It defaults to 24h and cannot be nil in
 	// the internal state.
 	UpdatePeriod *time.Duration
-	// Providers is a list of DNS providers
+	// Providers is a list of DNS providers.
+	// It defaults to ["cloudflare"] and is ignored if the UpstreamType is
+	// [DNSUpstreamTypePlain] and the UpstreamPlainAddresses field is set.
 	Providers []string `json:"providers"`
 	// Caching is true if the server should cache
 	// DNS responses.
@@ -36,32 +41,22 @@ type DNS struct {
 	// Blacklist contains settings to configure the filter
 	// block lists.
 	Blacklist DNSBlacklist
-	// ServerAddress is the DNS server to use inside
-	// the Go program and for the system.
-	// It defaults to '127.0.0.1' to be used with the
-	// local server. It cannot be the zero value in the internal
-	// state.
-	ServerAddress netip.Addr
-	// KeepNameserver is true if the existing DNS server
-	// found in /etc/resolv.conf should be used
-	// Note setting this to true will likely DNS traffic
-	// outside the VPN tunnel since it would go through
-	// the local DNS server of your Docker/Kubernetes
-	// configuration, which is likely not going through the tunnel.
-	// This will also disable the DNS forwarder server and the
-	// `ServerAddress` field will be ignored.
-	// It defaults to false and cannot be nil in the
-	// internal state.
-	KeepNameserver *bool
+	// UpstreamPlainAddresses are the upstream plaintext DNS resolver
+	// addresses to use by the built-in DNS server forwarder.
+	// Note, if the upstream type is [dnsUpstreamTypePlain] and this field is set,
+	// the Providers field is ignored.
+	UpstreamPlainAddresses []netip.AddrPort
 }
 
 var (
 	ErrDNSUpstreamTypeNotValid = errors.New("DNS upstream type is not valid")
 	ErrDNSUpdatePeriodTooShort = errors.New("update period is too short")
+	ErrDNSUpstreamPlainNoIPv6  = errors.New("upstream plain addresses do not contain any IPv6 address")
+	ErrDNSUpstreamPlainNoIPv4  = errors.New("upstream plain addresses do not contain any IPv4 address")
 )
 
 func (d DNS) validate() (err error) {
-	if !helpers.IsOneOf(d.UpstreamType, "dot", "doh", "plain") {
+	if !helpers.IsOneOf(d.UpstreamType, DNSUpstreamTypeDot, DNSUpstreamTypeDoh, DNSUpstreamTypePlain) {
 		return fmt.Errorf("%w: %s", ErrDNSUpstreamTypeNotValid, d.UpstreamType)
 	}
 
@@ -71,13 +66,27 @@ func (d DNS) validate() (err error) {
 			ErrDNSUpdatePeriodTooShort, *d.UpdatePeriod, minUpdatePeriod)
 	}
 
-	providers := provider.NewProviders()
-	for _, providerName := range d.Providers {
-		_, err := providers.Get(providerName)
-		if err != nil {
-			return err
+	if d.UpstreamType == DNSUpstreamTypePlain {
+		selectedHasPlainIPv4, selectedHasPlainIPv6 := false, false
+		for _, addrPort := range d.UpstreamPlainAddresses {
+			if !selectedHasPlainIPv4 && addrPort.Addr().Is4() {
+				selectedHasPlainIPv4 = true
+			}
+			if !selectedHasPlainIPv6 && addrPort.Addr().Is6() {
+				selectedHasPlainIPv6 = true
+			}
+			if selectedHasPlainIPv4 && selectedHasPlainIPv6 {
+				break
+			}
+		}
+		switch {
+		case *d.IPv6 && !selectedHasPlainIPv6:
+			return fmt.Errorf("%w: in %d addresses", ErrDNSUpstreamPlainNoIPv6, len(d.UpstreamPlainAddresses))
+		case !*d.IPv6 && !selectedHasPlainIPv4:
+			return fmt.Errorf("%w: in %d addresses", ErrDNSUpstreamPlainNoIPv4, len(d.UpstreamPlainAddresses))
 		}
 	}
+	// Note: all DNS built in providers have both IPv4 and IPv6 addresses for all modes
 
 	err = d.Blacklist.validate()
 	if err != nil {
@@ -89,15 +98,13 @@ func (d DNS) validate() (err error) {
 
 func (d *DNS) Copy() (copied DNS) {
 	return DNS{
-		ServerEnabled:  gosettings.CopyPointer(d.ServerEnabled),
-		UpstreamType:   d.UpstreamType,
-		UpdatePeriod:   gosettings.CopyPointer(d.UpdatePeriod),
-		Providers:      gosettings.CopySlice(d.Providers),
-		Caching:        gosettings.CopyPointer(d.Caching),
-		IPv6:           gosettings.CopyPointer(d.IPv6),
-		Blacklist:      d.Blacklist.copy(),
-		ServerAddress:  d.ServerAddress,
-		KeepNameserver: gosettings.CopyPointer(d.KeepNameserver),
+		UpstreamType:           d.UpstreamType,
+		UpdatePeriod:           gosettings.CopyPointer(d.UpdatePeriod),
+		Providers:              gosettings.CopySlice(d.Providers),
+		Caching:                gosettings.CopyPointer(d.Caching),
+		IPv6:                   gosettings.CopyPointer(d.IPv6),
+		Blacklist:              d.Blacklist.copy(),
+		UpstreamPlainAddresses: gosettings.CopySlice(d.UpstreamPlainAddresses),
 	}
 }
 
@@ -105,48 +112,30 @@ func (d *DNS) Copy() (copied DNS) {
 // settings object with any field set in the other
 // settings.
 func (d *DNS) overrideWith(other DNS) {
-	d.ServerEnabled = gosettings.OverrideWithPointer(d.ServerEnabled, other.ServerEnabled)
 	d.UpstreamType = gosettings.OverrideWithComparable(d.UpstreamType, other.UpstreamType)
 	d.UpdatePeriod = gosettings.OverrideWithPointer(d.UpdatePeriod, other.UpdatePeriod)
 	d.Providers = gosettings.OverrideWithSlice(d.Providers, other.Providers)
 	d.Caching = gosettings.OverrideWithPointer(d.Caching, other.Caching)
 	d.IPv6 = gosettings.OverrideWithPointer(d.IPv6, other.IPv6)
 	d.Blacklist.overrideWith(other.Blacklist)
-	d.ServerAddress = gosettings.OverrideWithValidator(d.ServerAddress, other.ServerAddress)
-	d.KeepNameserver = gosettings.OverrideWithPointer(d.KeepNameserver, other.KeepNameserver)
+	d.UpstreamPlainAddresses = gosettings.OverrideWithSlice(d.UpstreamPlainAddresses, other.UpstreamPlainAddresses)
 }
 
 func (d *DNS) setDefaults() {
-	d.ServerEnabled = gosettings.DefaultPointer(d.ServerEnabled, true)
-	d.UpstreamType = gosettings.DefaultComparable(d.UpstreamType, "dot")
+	d.UpstreamType = gosettings.DefaultComparable(d.UpstreamType, DNSUpstreamTypeDot)
 	const defaultUpdatePeriod = 24 * time.Hour
 	d.UpdatePeriod = gosettings.DefaultPointer(d.UpdatePeriod, defaultUpdatePeriod)
-	d.Providers = gosettings.DefaultSlice(d.Providers, []string{
-		provider.Cloudflare().Name,
-	})
+	d.UpstreamPlainAddresses = gosettings.DefaultSlice(d.UpstreamPlainAddresses, []netip.AddrPort{})
+	d.Providers = gosettings.DefaultSlice(d.Providers, defaultDNSProviders())
 	d.Caching = gosettings.DefaultPointer(d.Caching, true)
 	d.IPv6 = gosettings.DefaultPointer(d.IPv6, false)
 	d.Blacklist.setDefaults()
-	d.ServerAddress = gosettings.DefaultValidator(d.ServerAddress,
-		netip.AddrFrom4([4]byte{127, 0, 0, 1}))
-	d.KeepNameserver = gosettings.DefaultPointer(d.KeepNameserver, false)
 }
 
-func (d DNS) GetFirstPlaintextIPv4() (ipv4 netip.Addr) {
-	localhost := netip.AddrFrom4([4]byte{127, 0, 0, 1})
-	if d.ServerAddress.Compare(localhost) != 0 && d.ServerAddress.Is4() {
-		return d.ServerAddress
+func defaultDNSProviders() []string {
+	return []string{
+		provider.Cloudflare().Name,
 	}
-
-	providers := provider.NewProviders()
-	provider, err := providers.Get(d.Providers[0])
-	if err != nil {
-		// Settings should be validated before calling this function,
-		// so an error happening here is a programming error.
-		panic(err)
-	}
-
-	return provider.Plain.IPv4[0].Addr()
 }
 
 func (d DNS) String() string {
@@ -155,22 +144,25 @@ func (d DNS) String() string {
 
 func (d DNS) toLinesNode() (node *gotree.Node) {
 	node = gotree.New("DNS settings:")
-	node.Appendf("Keep existing nameserver(s): %s", gosettings.BoolToYesNo(d.KeepNameserver))
-	if *d.KeepNameserver {
-		return node
-	}
-	node.Appendf("DNS server address to use: %s", d.ServerAddress)
-
-	node.Appendf("DNS forwarder server enabled: %s", gosettings.BoolToYesNo(d.ServerEnabled))
-	if !*d.ServerEnabled {
-		return node
-	}
 
 	node.Appendf("Upstream resolver type: %s", d.UpstreamType)
 
 	upstreamResolvers := node.Append("Upstream resolvers:")
-	for _, provider := range d.Providers {
-		upstreamResolvers.Append(provider)
+	if len(d.UpstreamPlainAddresses) > 0 {
+		if d.UpstreamType == DNSUpstreamTypePlain {
+			for _, addr := range d.UpstreamPlainAddresses {
+				upstreamResolvers.Append(addr.String())
+			}
+		} else {
+			node.Appendf("Upstream plain addresses: ignored because upstream type is not plain")
+			for _, provider := range d.Providers {
+				upstreamResolvers.Append(provider)
+			}
+		}
+	} else {
+		for _, provider := range d.Providers {
+			upstreamResolvers.Append(provider)
+		}
 	}
 
 	node.Appendf("Caching: %s", gosettings.BoolToYesNo(d.Caching))
@@ -188,11 +180,6 @@ func (d DNS) toLinesNode() (node *gotree.Node) {
 }
 
 func (d *DNS) read(r *reader.Reader) (err error) {
-	d.ServerEnabled, err = r.BoolPtr("DNS_SERVER", reader.RetroKeys("DOT"))
-	if err != nil {
-		return err
-	}
-
 	d.UpstreamType = r.String("DNS_UPSTREAM_RESOLVER_TYPE")
 
 	d.UpdatePeriod, err = r.DurationPtr("DNS_UPDATE_PERIOD")
@@ -217,15 +204,42 @@ func (d *DNS) read(r *reader.Reader) (err error) {
 		return err
 	}
 
-	d.ServerAddress, err = r.NetipAddr("DNS_ADDRESS", reader.RetroKeys("DNS_PLAINTEXT_ADDRESS"))
-	if err != nil {
-		return err
-	}
-
-	d.KeepNameserver, err = r.BoolPtr("DNS_KEEP_NAMESERVER")
+	err = d.readUpstreamPlainAddresses(r)
 	if err != nil {
 		return err
 	}
 
 	return nil
 }
+
+func (d *DNS) readUpstreamPlainAddresses(r *reader.Reader) (err error) {
+	// If DNS_UPSTREAM_PLAIN_ADDRESSES is set, the user must also set DNS_UPSTREAM_TYPE=plain
+	// for these to be used. This is an added safety measure to reduce misunderstandings, and
+	// reduce odd settings overrides.
+	d.UpstreamPlainAddresses, err = r.CSVNetipAddrPorts("DNS_UPSTREAM_PLAIN_ADDRESSES")
+	if err != nil {
+		return err
+	}
+
+	// Retro-compatibility - remove in v4
+	// If DNS_ADDRESS is set to a non-localhost address, append it to the other
+	// upstream plain addresses, assuming port 53, and force the upstream type to plain
+	// to maintain retro-compatibility behavior.
+	serverAddress, err := r.NetipAddr("DNS_ADDRESS",
+		reader.RetroKeys("DNS_PLAINTEXT_ADDRESS"),
+		reader.IsRetro("DNS_UPSTREAM_PLAIN_ADDRESSES"))
+	if err != nil {
+		return err
+	} else if !serverAddress.IsValid() {
+		return nil
+	}
+	isLocalhost := serverAddress.Compare(netip.AddrFrom4([4]byte{127, 0, 0, 1})) == 0
+	if isLocalhost {
+		return nil
+	}
+	const defaultPlainPort = 53
+	addrPort := netip.AddrPortFrom(serverAddress, defaultPlainPort)
+	d.UpstreamPlainAddresses = append(d.UpstreamPlainAddresses, addrPort)
+	d.UpstreamType = DNSUpstreamTypePlain
+	return nil
+}

internal/configuration/settings/dns_test.go

@@ -0,0 +1,26 @@
+package settings
+
+import (
+	"testing"
+
+	"github.com/qdm12/dns/v2/pkg/provider"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_defaultDNSProviders(t *testing.T) {
+	t.Parallel()
+
+	names := defaultDNSProviders()
+
+	found := false
+	providers := provider.NewProviders()
+	for _, name := range names {
+		provider, err := providers.Get(name)
+		require.NoError(t, err)
+		if len(provider.Plain.IPv4) > 0 {
+			found = true
+			break
+		}
+	}
+	require.True(t, found, "no default DNS provider has a plaintext IPv4 address")
+}

internal/configuration/settings/dnsblacklist.go

@@ -23,7 +23,9 @@ type DNSBlacklist struct {
 	AddBlockedIPs        []netip.Addr
 	AddBlockedIPPrefixes []netip.Prefix
 	// RebindingProtectionExemptHostnames is a list of hostnames
-	// exempt from DNS rebinding protection.
+	// exempt from DNS rebinding protection. It can contain parent
+	// domains which are of the form "*.example.com". Note the wildcard
+	// can only be used at the start of the hostname.
 	RebindingProtectionExemptHostnames []string
 }
 
@@ -55,6 +57,9 @@ func (b DNSBlacklist) validate() (err error) {
 	}
 
 	for _, host := range b.RebindingProtectionExemptHostnames {
+		if len(host) > 2 && host[:2] == "*." {
+			host = host[2:]
+		}
 		if !hostRegex.MatchString(host) {
 			return fmt.Errorf("%w: %s", ErrRebindingProtectionExemptHostNotValid, host)
 		}

internal/configuration/settings/firewall.go

@@ -15,7 +15,7 @@ type Firewall struct {
 	InputPorts      []uint16
 	OutboundSubnets []netip.Prefix
 	Enabled         *bool
-	Debug           *bool
+	Iptables        Iptables
 }
 
 func (f Firewall) validate() (err error) {
@@ -33,6 +33,11 @@ func (f Firewall) validate() (err error) {
 		}
 	}
 
+	err = f.Iptables.validate()
+	if err != nil {
+		return fmt.Errorf("iptables settings: %w", err)
+	}
+
 	return nil
 }
 
@@ -51,7 +56,7 @@ func (f *Firewall) copy() (copied Firewall) {
 		InputPorts:      gosettings.CopySlice(f.InputPorts),
 		OutboundSubnets: gosettings.CopySlice(f.OutboundSubnets),
 		Enabled:         gosettings.CopyPointer(f.Enabled),
-		Debug:           gosettings.CopyPointer(f.Debug),
+		Iptables:        f.Iptables.copy(),
 	}
 }
 
@@ -63,12 +68,12 @@ func (f *Firewall) overrideWith(other Firewall) {
 	f.InputPorts = gosettings.OverrideWithSlice(f.InputPorts, other.InputPorts)
 	f.OutboundSubnets = gosettings.OverrideWithSlice(f.OutboundSubnets, other.OutboundSubnets)
 	f.Enabled = gosettings.OverrideWithPointer(f.Enabled, other.Enabled)
-	f.Debug = gosettings.OverrideWithPointer(f.Debug, other.Debug)
+	f.Iptables.overrideWith(other.Iptables)
 }
 
-func (f *Firewall) setDefaults() {
+func (f *Firewall) setDefaults(globalLogLevel string) {
 	f.Enabled = gosettings.DefaultPointer(f.Enabled, true)
-	f.Debug = gosettings.DefaultPointer(f.Debug, false)
+	f.Iptables.setDefaults(globalLogLevel)
 }
 
 func (f Firewall) String() string {
@@ -83,9 +88,7 @@ func (f Firewall) toLinesNode() (node *gotree.Node) {
 		return node
 	}
 
-	if *f.Debug {
-		node.Appendf("Debug mode: on")
-	}
+	node.AppendNode(f.Iptables.toLinesNode())
 
 	if len(f.VPNInputPorts) > 0 {
 		vpnInputPortsNode := node.Appendf("VPN input ports:")
@@ -133,9 +136,9 @@ func (f *Firewall) read(r *reader.Reader) (err error) {
 		return err
 	}
 
-	f.Debug, err = r.BoolPtr("FIREWALL_DEBUG")
+	err = f.Iptables.read(r)
 	if err != nil {
-		return err
+		return fmt.Errorf("reading iptables settings: %w", err)
 	}
 
 	return nil

internal/configuration/settings/firewall_test.go

@@ -4,6 +4,7 @@ import (
 	"net/netip"
 	"testing"
 
+	"github.com/qdm12/log"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -15,7 +16,10 @@ func Test_Firewall_validate(t *testing.T) {
 		errWrapped error
 		errMessage string
 	}{
-		"empty": {},
+		"empty": {
+			errWrapped: log.ErrLevelNotRecognized,
+			errMessage: "iptables settings: log level: level is not recognized: ",
+		},
 		"zero_vpn_input_port": {
 			firewall: Firewall{
 				VPNInputPorts: []uint16{0},
@@ -41,6 +45,7 @@ func Test_Firewall_validate(t *testing.T) {
 		},
 		"public_outbound_subnet": {
 			firewall: Firewall{
+				Iptables: Iptables{LogLevel: log.LevelInfo.String()},
 				OutboundSubnets: []netip.Prefix{
 					netip.MustParsePrefix("1.2.3.4/32"),
 				},
@@ -48,6 +53,7 @@ func Test_Firewall_validate(t *testing.T) {
 		},
 		"valid_settings": {
 			firewall: Firewall{
+				Iptables:      Iptables{LogLevel: log.LevelInfo.String()},
 				VPNInputPorts: []uint16{100, 101},
 				InputPorts:    []uint16{200, 201},
 				OutboundSubnets: []netip.Prefix{

internal/configuration/settings/iptables.go

@@ -0,0 +1,67 @@
+package settings
+
+import (
+	"fmt"
+
+	"github.com/qdm12/gosettings"
+	"github.com/qdm12/gosettings/reader"
+	"github.com/qdm12/gotree"
+	"github.com/qdm12/log"
+)
+
+// Iptables contains settings to customize iptables.
+type Iptables struct {
+	LogLevel string
+}
+
+func (i Iptables) validate() (err error) {
+	_, err = log.ParseLevel(i.LogLevel)
+	if err != nil {
+		return fmt.Errorf("log level: %w", err)
+	}
+
+	return nil
+}
+
+func (i *Iptables) copy() (copied Iptables) {
+	return Iptables{
+		LogLevel: i.LogLevel,
+	}
+}
+
+func (i *Iptables) overrideWith(other Iptables) {
+	i.LogLevel = gosettings.OverrideWithComparable(i.LogLevel, other.LogLevel)
+}
+
+func (i *Iptables) setDefaults(globalLogLevel string) {
+	defaultLevel := globalLogLevel
+	if defaultLevel == log.LevelDebug.String() {
+		// Given iptables debug logger is quite verbose, we only turn it to debug level
+		// if it is explicitly asked to be at debug level; even if the global logger is
+		// at the debug level, we keep iptables at info level by default.
+		defaultLevel = log.LevelInfo.String()
+	}
+	i.LogLevel = gosettings.DefaultComparable(i.LogLevel, defaultLevel)
+}
+
+func (i Iptables) String() string {
+	return i.toLinesNode().String()
+}
+
+func (i Iptables) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Iptables settings:")
+	node.Appendf("Log level: %s", i.LogLevel)
+	return node
+}
+
+func (i *Iptables) read(r *reader.Reader) (err error) {
+	debugMode, err := r.BoolPtr("FIREWALL_DEBUG", reader.IsRetro("FIREWALL_IPTABLES_LOG_LEVEL"))
+	if err != nil {
+		return err
+	}
+	if debugMode != nil && *debugMode {
+		i.LogLevel = log.LevelDebug.String()
+	}
+	i.LogLevel = r.String("FIREWALL_IPTABLES_LOG_LEVEL")
+	return nil
+}

internal/configuration/settings/ipv6.go

@@ -0,0 +1,58 @@
+package settings
+
+import (
+	"net/netip"
+
+	"github.com/qdm12/gosettings"
+	"github.com/qdm12/gosettings/reader"
+	"github.com/qdm12/gotree"
+)
+
+// IPv6 contains settings regarding IPv6 configuration.
+type IPv6 struct {
+	// CheckAddresses are the TCP ip:port addresses to dial to check if
+	// IPv6 is supported, in case a default IPv6 route is found.
+	// It defaults to google and cloudflare IPv6 anycast addresses
+	// [2001:4860:4860::8888]:53,[2606:4700:4700::1111]:53
+	CheckAddresses []netip.AddrPort
+}
+
+func (i IPv6) validate() (err error) {
+	return nil
+}
+
+func (i *IPv6) copy() (copied IPv6) {
+	return IPv6{
+		CheckAddresses: gosettings.CopySlice(i.CheckAddresses),
+	}
+}
+
+func (i *IPv6) overrideWith(other IPv6) {
+	i.CheckAddresses = gosettings.OverrideWithSlice(i.CheckAddresses, other.CheckAddresses)
+}
+
+func (i *IPv6) setDefaults() {
+	defaultCheckAddresses := []netip.AddrPort{
+		netip.MustParseAddrPort("[2001:4860:4860::8888]:53"),
+		netip.MustParseAddrPort("[2606:4700:4700::1111]:53"),
+	}
+	i.CheckAddresses = gosettings.DefaultSlice(i.CheckAddresses, defaultCheckAddresses)
+}
+
+func (i IPv6) String() string {
+	return i.toLinesNode().String()
+}
+
+func (i IPv6) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("IPv6 settings:")
+	addrsNode := node.Appendf("Check addresses:")
+	for _, addr := range i.CheckAddresses {
+		addrsNode.Append(addr.String())
+	}
+	return node
+}
+
+func (i *IPv6) read(r *reader.Reader) (err error) {
+	i.CheckAddresses, err = r.CSVNetipAddrPorts("IPV6_CHECK_ADDRESSES")
+	return err
+}

internal/configuration/settings/openvpnselection.go

@@ -60,7 +60,6 @@ func (o OpenVPNSelection) validate(vpnProvider string) (err error) {
 		providers.Giganews,
 		providers.Ipvanish,
 		providers.Perfectprivacy,
-		providers.Privado,
 		providers.Vyprvpn,
 	) {
 		return fmt.Errorf("%w: for VPN service provider %s",
@@ -75,8 +74,8 @@ func (o OpenVPNSelection) validate(vpnProvider string) (err error) {
 			providers.Privatevpn, providers.Torguard:
 		// no custom port allowed
 		case providers.Expressvpn, providers.Fastestvpn,
-			providers.Giganews, providers.Ipvanish, providers.Nordvpn,
-			providers.Privado, providers.Purevpn,
+			providers.Giganews, providers.Ipvanish,
+			providers.Nordvpn, providers.Purevpn,
 			providers.Surfshark, providers.VPNSecure,
 			providers.VPNUnlimited, providers.Vyprvpn:
 			return fmt.Errorf("%w: for VPN service provider %s",
@@ -99,6 +98,9 @@ func (o OpenVPNSelection) validate(vpnProvider string) (err error) {
 			case providers.Perfectprivacy:
 				allowedTCP = []uint16{44, 443, 4433}
 				allowedUDP = []uint16{44, 443, 4433}
+			case providers.Privado:
+				allowedTCP = []uint16{443, 1194, 8080, 8443}
+				allowedUDP = []uint16{443, 1194, 8080, 8443}
 			case providers.PrivateInternetAccess:
 				allowedTCP = []uint16{80, 110, 443}
 				allowedUDP = []uint16{53, 1194, 1197, 1198, 8080, 9201}
@@ -130,7 +132,6 @@ func (o OpenVPNSelection) validate(vpnProvider string) (err error) {
 	// Validate EncPreset
 	if vpnProvider == providers.PrivateInternetAccess {
 		validEncryptionPresets := []string{
-			presets.None,
 			presets.Normal,
 			presets.Strong,
 		}

internal/configuration/settings/pmtud.go

@@ -0,0 +1,111 @@
+package settings
+
+import (
+	"errors"
+	"fmt"
+	"net/netip"
+
+	"github.com/qdm12/gosettings"
+	"github.com/qdm12/gosettings/reader"
+	"github.com/qdm12/gotree"
+)
+
+// PMTUD contains settings to configure Path MTU Discovery.
+type PMTUD struct {
+	// ICMPAddresses is the redundancy list of addresses to use
+	// for ICMP path MTU discovery. Each address MUST handle ICMP
+	// packets for PMTUD to work.
+	// It cannot be nil in the internal state.
+	ICMPAddresses []netip.Addr `json:"icmp_addresses"`
+	// TCPAddresses is the redundancy list of addresses to use
+	// for TCP path MTU discovery. Each address MUST have a listening
+	// TCP server on the port specified.
+	// It cannot be nil in the internal state.
+	TCPAddresses []netip.AddrPort `json:"tcp_addresses"`
+}
+
+var (
+	ErrPMTUDICMPAddressNotValid = errors.New("PMTUD ICMP address is not valid")
+	ErrPMTUDTCPAddressNotValid  = errors.New("PMTUD TCP address is not valid")
+)
+
+// Validate validates PMTUD settings.
+func (p PMTUD) validate() (err error) {
+	for i, addr := range p.ICMPAddresses {
+		if !addr.IsValid() {
+			return fmt.Errorf("%w: at index %d", ErrPMTUDICMPAddressNotValid, i)
+		}
+	}
+	for i, addr := range p.TCPAddresses {
+		if !addr.IsValid() {
+			return fmt.Errorf("%w: at index %d", ErrPMTUDTCPAddressNotValid, i)
+		}
+	}
+	return nil
+}
+
+func (p *PMTUD) copy() (copied PMTUD) {
+	return PMTUD{
+		ICMPAddresses: gosettings.CopySlice(p.ICMPAddresses),
+		TCPAddresses:  gosettings.CopySlice(p.TCPAddresses),
+	}
+}
+
+func (p *PMTUD) overrideWith(other PMTUD) {
+	p.ICMPAddresses = gosettings.OverrideWithSlice(p.ICMPAddresses, other.ICMPAddresses)
+	p.TCPAddresses = gosettings.OverrideWithSlice(p.TCPAddresses, other.TCPAddresses)
+}
+
+func (p *PMTUD) setDefaults() {
+	defaultICMPAddresses := []netip.Addr{
+		netip.AddrFrom4([4]byte{1, 1, 1, 1}),
+		netip.AddrFrom4([4]byte{8, 8, 8, 8}),
+	}
+	p.ICMPAddresses = gosettings.DefaultSlice(p.ICMPAddresses, defaultICMPAddresses)
+
+	const dnsPort, tlsPort = 53, 443
+	defaultTCPAddresses := []netip.AddrPort{
+		netip.AddrPortFrom(netip.AddrFrom4([4]byte{1, 1, 1, 1}), dnsPort),
+		netip.AddrPortFrom(netip.AddrFrom4([4]byte{8, 8, 8, 8}), dnsPort),
+		netip.AddrPortFrom(netip.AddrFrom4([4]byte{1, 1, 1, 1}), tlsPort),
+		netip.AddrPortFrom(netip.AddrFrom4([4]byte{8, 8, 8, 8}), tlsPort),
+		netip.AddrPortFrom(netip.MustParseAddr("2606:4700:4700::1111"), dnsPort),
+		netip.AddrPortFrom(netip.MustParseAddr("2001:4860:4860::8888"), dnsPort),
+		netip.AddrPortFrom(netip.MustParseAddr("2606:4700:4700::1111"), tlsPort),
+		netip.AddrPortFrom(netip.MustParseAddr("2001:4860:4860::8888"), tlsPort),
+	}
+	p.TCPAddresses = gosettings.DefaultSlice(p.TCPAddresses, defaultTCPAddresses)
+}
+
+func (p PMTUD) String() string {
+	return p.toLinesNode().String()
+}
+
+func (p PMTUD) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("Path MTU discovery:")
+
+	icmpAddrNode := node.Append("ICMP addresses:")
+	for _, addr := range p.ICMPAddresses {
+		icmpAddrNode.Append(addr.String())
+	}
+
+	tcpAddrNode := node.Append("TCP addresses:")
+	for _, addr := range p.TCPAddresses {
+		tcpAddrNode.Append(addr.String())
+	}
+	return node
+}
+
+func (p *PMTUD) read(r *reader.Reader) (err error) {
+	p.ICMPAddresses, err = r.CSVNetipAddresses("PMTUD_ICMP_ADDRESSES")
+	if err != nil {
+		return err
+	}
+
+	p.TCPAddresses, err = r.CSVNetipAddrPorts("PMTUD_TCP_ADDRESSES")
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

internal/configuration/settings/portforward.go

@@ -1,8 +1,10 @@
 package settings
 
 import (
+	"errors"
 	"fmt"
 	"path/filepath"
+	"slices"
 
 	"github.com/qdm12/gluetun/internal/constants/providers"
 	"github.com/qdm12/gosettings"
@@ -37,16 +39,28 @@ type PortForwarding struct {
 	// It can be the empty string to indicate to NOT run a command.
 	// It cannot be nil in the internal state.
 	DownCommand *string `json:"down_command"`
-	// ListeningPort is the port traffic would be redirected to from the
-	// forwarded port. The redirection is disabled if it is set to 0, which
-	// is its default as well.
-	ListeningPort *uint16 `json:"listening_port"`
+	// ListeningPorts are the ports traffic would be redirected to from the
+	// forwarded ports. The redirection is disabled if it is the slice [0],
+	// which is its default as well. If set and not [0], its length must match
+	// the PortsCount value, such that each forwarded port is redirected to
+	// the corresponding listening port.
+	ListeningPorts []uint16 `json:"listening_port"`
+	// PortsCount is the number of ports to forward. It is optional for ProtonVPN
+	// and be between 1 and 5. For other providers, it must be set to 1 if port
+	// forwarding is enabled.
+	PortsCount uint16 `json:"ports_count"`
 	// Username is only used for Private Internet Access port forwarding.
 	Username string `json:"username"`
 	// Password is only used for Private Internet Access port forwarding.
 	Password string `json:"password"`
 }
 
+var (
+	ErrPortsCountTooHigh = errors.New("ports count too high")
+	ErrListeningPortsLen = errors.New("listening ports length must be equal to ports count")
+	ErrListeningPortZero = errors.New("listening port cannot be 0")
+)
+
 func (p PortForwarding) Validate(vpnProvider string) (err error) {
 	if !*p.Enabled {
 		return nil
@@ -75,13 +89,36 @@ func (p PortForwarding) Validate(vpnProvider string) (err error) {
 		}
 	}
 
-	if providerSelected == providers.PrivateInternetAccess {
+	switch providerSelected {
+	case providers.PrivateInternetAccess:
+		const maxPortsCount = 1
 		switch {
+		case p.PortsCount > maxPortsCount:
+			return fmt.Errorf("%w: %d > %d", ErrPortsCountTooHigh, p.PortsCount, maxPortsCount)
 		case p.Username == "":
 			return fmt.Errorf("%w", ErrPortForwardingUserEmpty)
 		case p.Password == "":
 			return fmt.Errorf("%w", ErrPortForwardingPasswordEmpty)
 		}
+	case providers.Protonvpn:
+		const maxPortsCount = 4
+		if p.PortsCount > maxPortsCount {
+			return fmt.Errorf("%w: %d > %d", ErrPortsCountTooHigh, p.PortsCount, maxPortsCount)
+		}
+	default:
+		const maxPortsCount = 1
+		if p.PortsCount > maxPortsCount {
+			return fmt.Errorf("%w: %d > %d", ErrPortsCountTooHigh, p.PortsCount, maxPortsCount)
+		}
+	}
+
+	if !slices.Equal(p.ListeningPorts, []uint16{0}) {
+		switch {
+		case len(p.ListeningPorts) != int(p.PortsCount):
+			return fmt.Errorf("%w: %d != %d", ErrListeningPortsLen, len(p.ListeningPorts), p.PortsCount)
+		case slices.Contains(p.ListeningPorts, 0):
+			return fmt.Errorf("%w: in %v", ErrListeningPortZero, p.ListeningPorts)
+		}
 	}
 
 	return nil
@@ -89,14 +126,14 @@ func (p PortForwarding) Validate(vpnProvider string) (err error) {
 
 func (p *PortForwarding) Copy() (copied PortForwarding) {
 	return PortForwarding{
-		Enabled:       gosettings.CopyPointer(p.Enabled),
-		Provider:      gosettings.CopyPointer(p.Provider),
-		Filepath:      gosettings.CopyPointer(p.Filepath),
-		UpCommand:     gosettings.CopyPointer(p.UpCommand),
-		DownCommand:   gosettings.CopyPointer(p.DownCommand),
-		ListeningPort: gosettings.CopyPointer(p.ListeningPort),
-		Username:      p.Username,
-		Password:      p.Password,
+		Enabled:        gosettings.CopyPointer(p.Enabled),
+		Provider:       gosettings.CopyPointer(p.Provider),
+		Filepath:       gosettings.CopyPointer(p.Filepath),
+		UpCommand:      gosettings.CopyPointer(p.UpCommand),
+		DownCommand:    gosettings.CopyPointer(p.DownCommand),
+		ListeningPorts: gosettings.CopySlice(p.ListeningPorts),
+		Username:       p.Username,
+		Password:       p.Password,
 	}
 }
 
@@ -106,7 +143,7 @@ func (p *PortForwarding) OverrideWith(other PortForwarding) {
 	p.Filepath = gosettings.OverrideWithPointer(p.Filepath, other.Filepath)
 	p.UpCommand = gosettings.OverrideWithPointer(p.UpCommand, other.UpCommand)
 	p.DownCommand = gosettings.OverrideWithPointer(p.DownCommand, other.DownCommand)
-	p.ListeningPort = gosettings.OverrideWithPointer(p.ListeningPort, other.ListeningPort)
+	p.ListeningPorts = gosettings.OverrideWithSlice(p.ListeningPorts, other.ListeningPorts)
 	p.Username = gosettings.OverrideWithComparable(p.Username, other.Username)
 	p.Password = gosettings.OverrideWithComparable(p.Password, other.Password)
 }
@@ -117,7 +154,8 @@ func (p *PortForwarding) setDefaults() {
 	p.Filepath = gosettings.DefaultPointer(p.Filepath, "/tmp/gluetun/forwarded_port")
 	p.UpCommand = gosettings.DefaultPointer(p.UpCommand, "")
 	p.DownCommand = gosettings.DefaultPointer(p.DownCommand, "")
-	p.ListeningPort = gosettings.DefaultPointer(p.ListeningPort, 0)
+	p.ListeningPorts = gosettings.DefaultSlice(p.ListeningPorts, []uint16{0}) // disabled
+	p.PortsCount = gosettings.DefaultComparable(p.PortsCount, 1)
 }
 
 func (p PortForwarding) String() string {
@@ -131,11 +169,14 @@ func (p PortForwarding) toLinesNode() (node *gotree.Node) {
 
 	node = gotree.New("Automatic port forwarding settings:")
 
-	listeningPort := "disabled"
-	if *p.ListeningPort != 0 {
-		listeningPort = fmt.Sprintf("%d", *p.ListeningPort)
+	node.Appendf("Number of ports to be forwarded: %d", p.PortsCount)
+
+	if !slices.Equal(p.ListeningPorts, []uint16{0}) {
+		redirNode := node.Appendf("Redirection for listening ports:")
+		for i, port := range p.ListeningPorts {
+			redirNode.Appendf("Port #%d -> %d", i+1, port)
+		}
 	}
-	node.Appendf("Redirection listening port: %s", listeningPort)
 
 	if *p.Provider == "" {
 		node.Appendf("Use port forwarding code for current provider")
@@ -190,7 +231,13 @@ func (p *PortForwarding) read(r *reader.Reader) (err error) {
 	p.DownCommand = r.Get("VPN_PORT_FORWARDING_DOWN_COMMAND",
 		reader.ForceLowercase(false))
 
-	p.ListeningPort, err = r.Uint16Ptr("VPN_PORT_FORWARDING_LISTENING_PORT")
+	p.ListeningPorts, err = r.CSVUint16("VPN_PORT_FORWARDING_LISTENING_PORTS",
+		reader.RetroKeys("VPN_PORT_FORWARDING_LISTENING_PORT"))
+	if err != nil {
+		return err
+	}
+
+	p.PortsCount, err = r.Uint16("VPN_PORT_FORWARDING_PORTS_COUNT")
 	if err != nil {
 		return err
 	}

internal/configuration/settings/provider.go

@@ -2,6 +2,8 @@ package settings
 
 import (
 	"fmt"
+	"slices"
+	"sort"
 	"strings"
 
 	"github.com/qdm12/gluetun/internal/constants/providers"
@@ -28,10 +30,18 @@ type Provider struct {
 func (p *Provider) validate(vpnType string, filterChoicesGetter FilterChoicesGetter, warner Warner) (err error) {
 	// Validate Name
 	var validNames []string
-	if vpnType == vpn.OpenVPN {
+	switch vpnType {
+	case vpn.AmneziaWg:
+		validNames = []string{providers.Custom}
+	case vpn.OpenVPN:
 		validNames = providers.AllWithCustom()
 		validNames = append(validNames, "pia") // Retro-compatibility
-	} else { // Wireguard
+		// Remove Mullvad since it no longer supports OpenVPN as of January 15th, 2026
+		mullvadIndex := slices.Index(validNames, providers.Mullvad)
+		validNames[mullvadIndex], validNames[len(validNames)-1] = validNames[len(validNames)-1], validNames[mullvadIndex]
+		validNames = validNames[:len(validNames)-1]
+		sort.Strings(validNames)
+	case vpn.Wireguard:
 		validNames = []string{
 			providers.Airvpn,
 			providers.Custom,
@@ -45,11 +55,7 @@ func (p *Provider) validate(vpnType string, filterChoicesGetter FilterChoicesGet
 		}
 	}
 	if err = validate.IsOneOf(p.Name, validNames...); err != nil {
-		return fmt.Errorf("%w for Wireguard: %w", ErrVPNProviderNameNotValid, err)
-	}
-
-	if p.Name == providers.Mullvad && vpnType == vpn.OpenVPN {
-		warner.Warn("https://mullvad.net/en/blog/removing-openvpn-15th-january-2026")
+		return fmt.Errorf("%w for %s: %w", ErrVPNProviderNameNotValid, vpnType, err)
 	}
 
 	err = p.ServerSelection.validate(p.Name, filterChoicesGetter, warner)

internal/configuration/settings/serverselection.go

@@ -87,7 +87,7 @@ func (ss *ServerSelection) validate(vpnServiceProvider string,
 	filterChoicesGetter FilterChoicesGetter, warner Warner,
 ) (err error) {
 	switch ss.VPN {
-	case vpn.OpenVPN, vpn.Wireguard:
+	case vpn.AmneziaWg, vpn.OpenVPN, vpn.Wireguard:
 	default:
 		return fmt.Errorf("%w: %s", ErrVPNTypeNotValid, ss.VPN)
 	}
@@ -518,7 +518,8 @@ func (ss *ServerSelection) read(r *reader.Reader,
 		return err
 	}
 
-	err = ss.Wireguard.read(r)
+	amneziawg := ss.VPN == vpn.AmneziaWg
+	err = ss.Wireguard.read(r, amneziawg)
 	if err != nil {
 		return err
 	}

internal/configuration/settings/settings.go

@@ -2,7 +2,6 @@ package settings
 
 import (
 	"fmt"
-	"net/netip"
 
 	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
 	"github.com/qdm12/gluetun/internal/constants/providers"
@@ -27,7 +26,9 @@ type Settings struct {
 	Updater       Updater
 	Version       Version
 	VPN           VPN
+	IPv6          IPv6
 	Pprof         pprof.Settings
+	BoringPoll    BoringPoll
 }
 
 type FilterChoicesGetter interface {
@@ -53,10 +54,12 @@ func (s *Settings) Validate(filterChoicesGetter FilterChoicesGetter, ipv6Support
 		"system":          s.System.validate,
 		"updater":         s.Updater.Validate,
 		"version":         s.Version.validate,
+		"ipv6":            s.IPv6.validate,
 		// Pprof validation done in pprof constructor
 		"VPN": func() error {
 			return s.VPN.Validate(filterChoicesGetter, ipv6Supported, warner)
 		},
+		"boring poll": s.BoringPoll.validate,
 	}
 
 	for name, validation := range nameToValidation {
@@ -85,6 +88,8 @@ func (s *Settings) copy() (copied Settings) {
 		Version:       s.Version.copy(),
 		VPN:           s.VPN.Copy(),
 		Pprof:         s.Pprof.Copy(),
+		BoringPoll:    s.BoringPoll.Copy(),
+		IPv6:          s.IPv6.copy(),
 	}
 }
 
@@ -106,6 +111,8 @@ func (s *Settings) OverrideWith(other Settings,
 	patchedSettings.Version.overrideWith(other.Version)
 	patchedSettings.VPN.OverrideWith(other.VPN)
 	patchedSettings.Pprof.OverrideWith(other.Pprof)
+	patchedSettings.BoringPoll.overrideWith(other.BoringPoll)
+	patchedSettings.IPv6.overrideWith(other.IPv6)
 	err = patchedSettings.Validate(filterChoicesGetter, ipv6Supported, warner)
 	if err != nil {
 		return err
@@ -117,10 +124,12 @@ func (s *Settings) OverrideWith(other Settings,
 func (s *Settings) SetDefaults() {
 	s.ControlServer.setDefaults()
 	s.DNS.setDefaults()
-	s.Firewall.setDefaults()
+	s.Log.setDefaults()
+	s.Firewall.setDefaults(s.Log.Level)
 	s.Health.SetDefaults()
 	s.HTTPProxy.setDefaults()
 	s.Log.setDefaults()
+	s.IPv6.setDefaults()
 	s.PublicIP.setDefaults()
 	s.Shadowsocks.setDefaults()
 	s.Storage.setDefaults()
@@ -129,6 +138,7 @@ func (s *Settings) SetDefaults() {
 	s.VPN.setDefaults()
 	s.Updater.SetDefaults(s.VPN.Provider.Name)
 	s.Pprof.SetDefaults()
+	s.BoringPoll.setDefaults()
 }
 
 func (s Settings) String() string {
@@ -142,6 +152,7 @@ func (s Settings) toLinesNode() (node *gotree.Node) {
 	node.AppendNode(s.DNS.toLinesNode())
 	node.AppendNode(s.Firewall.toLinesNode())
 	node.AppendNode(s.Log.toLinesNode())
+	node.AppendNode(s.IPv6.toLinesNode())
 	node.AppendNode(s.Health.toLinesNode())
 	node.AppendNode(s.Shadowsocks.toLinesNode())
 	node.AppendNode(s.HTTPProxy.toLinesNode())
@@ -152,6 +163,7 @@ func (s Settings) toLinesNode() (node *gotree.Node) {
 	node.AppendNode(s.Updater.toLinesNode())
 	node.AppendNode(s.Version.toLinesNode())
 	node.AppendNode(s.Pprof.ToLinesNode())
+	node.AppendNode(s.BoringPoll.toLinesNode())
 
 	return node
 }
@@ -174,13 +186,11 @@ func (s Settings) Warnings() (warnings []string) {
 			"by creating an issue, attaching the new certificate and we will update Gluetun.")
 	}
 
-	// TODO remove in v4
-	if s.DNS.ServerAddress.Unmap().Compare(netip.AddrFrom4([4]byte{127, 0, 0, 1})) != 0 {
-		warnings = append(warnings, "DNS address is set to "+s.DNS.ServerAddress.String()+
-			" so the local forwarding DNS server will not be used."+
-			" The default value changed to 127.0.0.1 so it uses the internal DNS server."+
-			" If this server fails to start, the IPv4 address of the first plaintext DNS server"+
-			" corresponding to the first DNS provider chosen is used.")
+	for _, upstreamAddress := range s.DNS.UpstreamPlainAddresses {
+		if upstreamAddress.Addr().IsPrivate() {
+			warnings = append(warnings, "DNS upstream address "+upstreamAddress.String()+" is private: "+
+				"DNS traffic might leak out of the VPN tunnel to that address.")
+		}
 	}
 
 	return warnings
@@ -208,7 +218,9 @@ func (s *Settings) Read(r *reader.Reader, warner Warner) (err error) {
 		"updater":     s.Updater.read,
 		"version":     s.Version.read,
 		"VPN":         s.VPN.read,
+		"IPv6":        s.IPv6.read,
 		"profiling":   s.Pprof.Read,
+		"boring poll": s.BoringPoll.read,
 	}
 
 	for name, read := range readFunctions {

internal/configuration/settings/settings_test.go

@@ -29,18 +29,28 @@ func Test_Settings_String(t *testing.T) {
 |   |       └── OpenVPN server selection settings:
 |   |           ├── Protocol: UDP
 |   |           └── Private Internet Access encryption preset: strong
-|   └── OpenVPN settings:
-|       ├── OpenVPN version: 2.6
-|       ├── User: [not set]
-|       ├── Password: [not set]
-|       ├── Private Internet Access encryption preset: strong
-|       ├── Network interface: tun0
-|       ├── Run OpenVPN as: root
-|       └── Verbosity level: 1
+|   ├── OpenVPN settings:
+|   |   ├── OpenVPN version: 2.6
+|   |   ├── User: [not set]
+|   |   ├── Password: [not set]
+|   |   ├── Private Internet Access encryption preset: strong
+|   |   ├── Network interface: tun0
+|   |   ├── Run OpenVPN as: root
+|   |   └── Verbosity level: 1
+|   └── Path MTU discovery:
+|       ├── ICMP addresses:
+|       |   ├── 1.1.1.1
+|       |   └── 8.8.8.8
+|       └── TCP addresses:
+|           ├── 1.1.1.1:53
+|           ├── 8.8.8.8:53
+|           ├── 1.1.1.1:443
+|           ├── 8.8.8.8:443
+|           ├── [2606:4700:4700::1111]:53
+|           ├── [2001:4860:4860::8888]:53
+|           ├── [2606:4700:4700::1111]:443
+|           └── [2001:4860:4860::8888]:443
 ├── DNS settings:
-|   ├── Keep existing nameserver(s): no
-|   ├── DNS server address to use: 127.0.0.1
-|   ├── DNS forwarder server enabled: yes
 |   ├── Upstream resolver type: dot
 |   ├── Upstream resolvers:
 |   |   └── Cloudflare
@@ -52,9 +62,15 @@ func Test_Settings_String(t *testing.T) {
 |       ├── Block ads: no
 |       └── Block surveillance: yes
 ├── Firewall settings:
-|   └── Enabled: yes
+|   ├── Enabled: yes
+|   └── Iptables settings:
+|       └── Log level: INFO
 ├── Log settings:
 |   └── Log level: INFO
+├── IPv6 settings:
+|   └── Check addresses:
+|       ├── [2001:4860:4860::8888]:53
+|       └── [2606:4700:4700::1111]:53
 ├── Health settings:
 |   ├── Server listening address: 127.0.0.1:9999
 |   ├── Target addresses:

internal/configuration/settings/updater.go

@@ -21,10 +21,6 @@ type Updater struct {
 	// updater. It cannot be nil in the internal state.
 	// TODO change to value and add Enabled field.
 	Period *time.Duration
-	// DNSAddress is the DNS server address to use
-	// to resolve VPN server hostnames to IP addresses.
-	// It cannot be the empty string in the internal state.
-	DNSAddress string
 	// MinRatio is the minimum ratio of servers to
 	// find per provider, compared to the total current
 	// number of servers. It defaults to 0.8.
@@ -76,7 +72,6 @@ func (u Updater) Validate() (err error) {
 func (u *Updater) copy() (copied Updater) {
 	return Updater{
 		Period:         gosettings.CopyPointer(u.Period),
-		DNSAddress:     u.DNSAddress,
 		MinRatio:       u.MinRatio,
 		Providers:      gosettings.CopySlice(u.Providers),
 		ProtonEmail:    gosettings.CopyPointer(u.ProtonEmail),
@@ -89,7 +84,6 @@ func (u *Updater) copy() (copied Updater) {
 // settings.
 func (u *Updater) overrideWith(other Updater) {
 	u.Period = gosettings.OverrideWithPointer(u.Period, other.Period)
-	u.DNSAddress = gosettings.OverrideWithComparable(u.DNSAddress, other.DNSAddress)
 	u.MinRatio = gosettings.OverrideWithComparable(u.MinRatio, other.MinRatio)
 	u.Providers = gosettings.OverrideWithSlice(u.Providers, other.Providers)
 	u.ProtonEmail = gosettings.OverrideWithPointer(u.ProtonEmail, other.ProtonEmail)
@@ -98,7 +92,6 @@ func (u *Updater) overrideWith(other Updater) {
 
 func (u *Updater) SetDefaults(vpnProvider string) {
 	u.Period = gosettings.DefaultPointer(u.Period, 0)
-	u.DNSAddress = gosettings.DefaultComparable(u.DNSAddress, "1.1.1.1:53")
 
 	if u.MinRatio == 0 {
 		const defaultMinRatio = 0.8
@@ -125,7 +118,6 @@ func (u Updater) toLinesNode() (node *gotree.Node) {
 
 	node = gotree.New("Server data updater settings:")
 	node.Appendf("Update period: %s", *u.Period)
-	node.Appendf("DNS address: %s", u.DNSAddress)
 	node.Appendf("Minimum ratio: %.1f", u.MinRatio)
 	node.Appendf("Providers to update: %s", strings.Join(u.Providers, ", "))
 	if slices.Contains(u.Providers, providers.Protonvpn) {
@@ -142,11 +134,6 @@ func (u *Updater) read(r *reader.Reader) (err error) {
 		return err
 	}
 
-	u.DNSAddress, err = readUpdaterDNSAddress()
-	if err != nil {
-		return err
-	}
-
 	u.MinRatio, err = r.Float64("UPDATER_MIN_RATIO")
 	if err != nil {
 		return err
@@ -166,12 +153,3 @@ func (u *Updater) read(r *reader.Reader) (err error) {
 
 	return nil
 }
-
-func readUpdaterDNSAddress() (address string, err error) {
-	// TODO this is currently using Cloudflare in
-	// plaintext to not be blocked by DNS over TLS by default.
-	// If a plaintext address is set in the DNS settings, this one will be used.
-	// use custom future encrypted DNS written in Go without blocking
-	// as it's too much trouble to start another parallel unbound instance for now.
-	return "", nil
-}

internal/configuration/settings/vpn.go

@@ -16,14 +16,26 @@ type VPN struct {
 	// empty string in the internal state.
 	Type      string    `json:"type"`
 	Provider  Provider  `json:"provider"`
+	AmneziaWg AmneziaWg `json:"amneziawg"`
 	OpenVPN   OpenVPN   `json:"openvpn"`
 	Wireguard Wireguard `json:"wireguard"`
+	PMTUD     PMTUD     `json:"pmtud"`
+	// UpCommand is the command to use when the VPN connection is up.
+	// It can be the empty string to indicate not to run a command.
+	// It cannot be nil in the internal state.
+	UpCommand *string `json:"up_command"`
+	// DownCommand is the command to use after the VPN connection goes down.
+	// It can be the empty string to indicate to NOT run a command.
+	// It cannot be nil in the internal state.
+	DownCommand *string `json:"down_command"`
 }
 
+// Validate validates VPN settings, using the filter choices getter (aka servers data storage),
+// and if IPv6 is supported or not.
 // TODO v4 remove pointer for receiver (because of Surfshark).
 func (v *VPN) Validate(filterChoicesGetter FilterChoicesGetter, ipv6Supported bool, warner Warner) (err error) {
 	// Validate Type
-	validVPNTypes := []string{vpn.OpenVPN, vpn.Wireguard}
+	validVPNTypes := []string{vpn.AmneziaWg, vpn.OpenVPN, vpn.Wireguard}
 	if err = validate.IsOneOf(v.Type, validVPNTypes...); err != nil {
 		return fmt.Errorf("%w: %w", ErrVPNTypeNotValid, err)
 	}
@@ -33,42 +45,66 @@ func (v *VPN) Validate(filterChoicesGetter FilterChoicesGetter, ipv6Supported bo
 		return fmt.Errorf("provider settings: %w", err)
 	}
 
-	if v.Type == vpn.OpenVPN {
+	switch v.Type {
+	case vpn.AmneziaWg:
+		err = v.AmneziaWg.validate(v.Provider.Name, ipv6Supported)
+		if err != nil {
+			return fmt.Errorf("AmneziaWG settings: %w", err)
+		}
+	case vpn.OpenVPN:
 		err := v.OpenVPN.validate(v.Provider.Name)
 		if err != nil {
 			return fmt.Errorf("OpenVPN settings: %w", err)
 		}
-	} else {
-		err := v.Wireguard.validate(v.Provider.Name, ipv6Supported)
+	case vpn.Wireguard:
+		const amneziawg = false
+		err := v.Wireguard.validate(v.Provider.Name, ipv6Supported, amneziawg)
 		if err != nil {
 			return fmt.Errorf("Wireguard settings: %w", err)
 		}
 	}
 
+	err = v.PMTUD.validate()
+	if err != nil {
+		return fmt.Errorf("PMTUD settings: %w", err)
+	}
+
 	return nil
 }
 
 func (v *VPN) Copy() (copied VPN) {
 	return VPN{
-		Type:      v.Type,
-		Provider:  v.Provider.copy(),
-		OpenVPN:   v.OpenVPN.copy(),
-		Wireguard: v.Wireguard.copy(),
+		Type:        v.Type,
+		Provider:    v.Provider.copy(),
+		AmneziaWg:   v.AmneziaWg.copy(),
+		OpenVPN:     v.OpenVPN.copy(),
+		Wireguard:   v.Wireguard.copy(),
+		PMTUD:       v.PMTUD.copy(),
+		UpCommand:   gosettings.CopyPointer(v.UpCommand),
+		DownCommand: gosettings.CopyPointer(v.DownCommand),
 	}
 }
 
 func (v *VPN) OverrideWith(other VPN) {
 	v.Type = gosettings.OverrideWithComparable(v.Type, other.Type)
 	v.Provider.overrideWith(other.Provider)
+	v.AmneziaWg.overrideWith(other.AmneziaWg)
 	v.OpenVPN.overrideWith(other.OpenVPN)
 	v.Wireguard.overrideWith(other.Wireguard)
+	v.PMTUD.overrideWith(other.PMTUD)
+	v.UpCommand = gosettings.OverrideWithPointer(v.UpCommand, other.UpCommand)
+	v.DownCommand = gosettings.OverrideWithPointer(v.DownCommand, other.DownCommand)
 }
 
 func (v *VPN) setDefaults() {
 	v.Type = gosettings.DefaultComparable(v.Type, vpn.OpenVPN)
 	v.Provider.setDefaults()
+	v.AmneziaWg.setDefaults(v.Provider.Name)
 	v.OpenVPN.setDefaults(v.Provider.Name)
 	v.Wireguard.setDefaults(v.Provider.Name)
+	v.PMTUD.setDefaults()
+	v.UpCommand = gosettings.DefaultPointer(v.UpCommand, "")
+	v.DownCommand = gosettings.DefaultPointer(v.DownCommand, "")
 }
 
 func (v VPN) String() string {
@@ -80,11 +116,22 @@ func (v VPN) toLinesNode() (node *gotree.Node) {
 
 	node.AppendNode(v.Provider.toLinesNode())
 
-	if v.Type == vpn.OpenVPN {
+	switch v.Type {
+	case vpn.AmneziaWg:
+		node.AppendNode(v.AmneziaWg.toLinesNode())
+	case vpn.OpenVPN:
 		node.AppendNode(v.OpenVPN.toLinesNode())
-	} else {
+	case vpn.Wireguard:
 		node.AppendNode(v.Wireguard.toLinesNode())
 	}
+	node.AppendNode(v.PMTUD.toLinesNode())
+
+	if *v.UpCommand != "" {
+		node.Appendf("Up command: %s", *v.UpCommand)
+	}
+	if *v.DownCommand != "" {
+		node.Appendf("Down command: %s", *v.DownCommand)
+	}
 
 	return node
 }
@@ -97,15 +144,30 @@ func (v *VPN) read(r *reader.Reader) (err error) {
 		return fmt.Errorf("VPN provider: %w", err)
 	}
 
+	err = v.AmneziaWg.read(r)
+	if err != nil {
+		return fmt.Errorf("AmneziaWG: %w", err)
+	}
+
 	err = v.OpenVPN.read(r)
 	if err != nil {
 		return fmt.Errorf("OpenVPN: %w", err)
 	}
 
-	err = v.Wireguard.read(r)
+	const amneziawg = false
+	err = v.Wireguard.read(r, amneziawg)
 	if err != nil {
 		return fmt.Errorf("wireguard: %w", err)
 	}
 
+	err = v.PMTUD.read(r)
+	if err != nil {
+		return fmt.Errorf("PMTUD: %w", err)
+	}
+
+	v.UpCommand = r.Get("VPN_UP_COMMAND", reader.ForceLowercase(false))
+
+	v.DownCommand = r.Get("VPN_DOWN_COMMAND", reader.ForceLowercase(false))
+
 	return nil
 }

internal/configuration/settings/wireguard.go

@@ -7,7 +7,6 @@ import (
 	"strings"
 	"time"
 
-	"github.com/qdm12/gluetun/internal/configuration/settings/helpers"
 	"github.com/qdm12/gluetun/internal/constants/providers"
 	"github.com/qdm12/gosettings"
 	"github.com/qdm12/gosettings/reader"
@@ -38,15 +37,9 @@ type Wireguard struct {
 	Interface                   string         `json:"interface"`
 	PersistentKeepaliveInterval *time.Duration `json:"persistent_keep_alive_interval"`
 	// Maximum Transmission Unit (MTU) of the Wireguard interface.
-	// It cannot be zero in the internal state, and defaults to
-	// 1320. Note it is not the wireguard-go MTU default of 1420
-	// because this impacts bandwidth a lot on some VPN providers,
-	// see https://github.com/qdm12/gluetun/issues/1650.
-	// It has been lowered to 1320 following quite a bit of
-	// investigation in the issue:
-	// https://github.com/qdm12/gluetun/issues/2533.
-	// Note this should now be replaced with the PMTUD feature.
-	MTU uint32 `json:"mtu"`
+	// It cannot be nil in the internal state, and defaults to
+	// 0 indicating to use PMTUD.
+	MTU *uint32 `json:"mtu"`
 	// Implementation is the Wireguard implementation to use.
 	// It can be "auto", "userspace" or "kernelspace".
 	// It defaults to "auto" and cannot be the empty string
@@ -57,23 +50,8 @@ type Wireguard struct {
 var regexpInterfaceName = regexp.MustCompile(`^[a-zA-Z0-9_]+$`)
 
 // Validate validates Wireguard settings.
-// It should only be ran if the VPN type chosen is Wireguard.
-func (w Wireguard) validate(vpnProvider string, ipv6Supported bool) (err error) {
-	if !helpers.IsOneOf(vpnProvider,
-		providers.Airvpn,
-		providers.Custom,
-		providers.Fastestvpn,
-		providers.Ivpn,
-		providers.Mullvad,
-		providers.Nordvpn,
-		providers.Protonvpn,
-		providers.Surfshark,
-		providers.Windscribe,
-	) {
-		// do not validate for VPN provider not supporting Wireguard
-		return nil
-	}
-
+// It should only be ran if the VPN type chosen is Wireguard or AmneziaWg.
+func (w Wireguard) validate(vpnProvider string, ipv6Supported, amneziawg bool) (err error) {
 	// Validate PrivateKey
 	if *w.PrivateKey == "" {
 		return fmt.Errorf("%w", ErrWireguardPrivateKeyNotSet)
@@ -142,9 +120,11 @@ func (w Wireguard) validate(vpnProvider string, ipv6Supported bool) (err error)
 			ErrWireguardInterfaceNotValid, w.Interface, regexpInterfaceName)
 	}
 
-	validImplementations := []string{"auto", "userspace", "kernelspace"}
-	if err := validate.IsOneOf(w.Implementation, validImplementations...); err != nil {
-		return fmt.Errorf("%w: %w", ErrWireguardImplementationNotValid, err)
+	if !amneziawg { // amneziawg should have its own Implementation field and ignore this one
+		validImplementations := []string{"auto", "userspace", "kernelspace"}
+		if err := validate.IsOneOf(w.Implementation, validImplementations...); err != nil {
+			return fmt.Errorf("%w: %w", ErrWireguardImplementationNotValid, err)
+		}
 	}
 
 	return nil
@@ -195,8 +175,7 @@ func (w *Wireguard) setDefaults(vpnProvider string) {
 	w.AllowedIPs = gosettings.DefaultSlice(w.AllowedIPs, defaultAllowedIPs)
 	w.PersistentKeepaliveInterval = gosettings.DefaultPointer(w.PersistentKeepaliveInterval, 0)
 	w.Interface = gosettings.DefaultComparable(w.Interface, "wg0")
-	const defaultMTU = 1320
-	w.MTU = gosettings.DefaultComparable(w.MTU, defaultMTU)
+	w.MTU = gosettings.DefaultPointer(w.MTU, 0)
 	w.Implementation = gosettings.DefaultComparable(w.Implementation, "auto")
 }
 
@@ -232,7 +211,11 @@ func (w Wireguard) toLinesNode() (node *gotree.Node) {
 	}
 
 	interfaceNode := node.Appendf("Network interface: %s", w.Interface)
-	interfaceNode.Appendf("MTU: %d", w.MTU)
+	if *w.MTU == 0 {
+		interfaceNode.Append("MTU: use path MTU discovery")
+	} else {
+		interfaceNode.Appendf("MTU: %d", *w.MTU)
+	}
 
 	if w.Implementation != "auto" {
 		node.Appendf("Implementation: %s", w.Implementation)
@@ -241,14 +224,21 @@ func (w Wireguard) toLinesNode() (node *gotree.Node) {
 	return node
 }
 
-func (w *Wireguard) read(r *reader.Reader) (err error) {
-	w.PrivateKey = r.Get("WIREGUARD_PRIVATE_KEY", reader.ForceLowercase(false))
-	w.PreSharedKey = r.Get("WIREGUARD_PRESHARED_KEY", reader.ForceLowercase(false))
+func (w *Wireguard) read(r *reader.Reader, amneziaWG bool) (err error) {
+	prefix := "WIREGUARD"
+	if amneziaWG {
+		prefix = "AMNEZIAWG"
+	}
+	w.PrivateKey = r.Get(prefix+"_PRIVATE_KEY", reader.ForceLowercase(false))
+	w.PreSharedKey = r.Get(prefix+"_PRESHARED_KEY", reader.ForceLowercase(false))
 	w.Interface = r.String("VPN_INTERFACE",
-		reader.RetroKeys("WIREGUARD_INTERFACE"), reader.ForceLowercase(false))
-	w.Implementation = r.String("WIREGUARD_IMPLEMENTATION")
+		reader.RetroKeys(prefix+"_INTERFACE"), reader.ForceLowercase(false))
 
-	addressStrings := r.CSV("WIREGUARD_ADDRESSES", reader.RetroKeys("WIREGUARD_ADDRESS"))
+	if !amneziaWG {
+		w.Implementation = r.String("WIREGUARD_IMPLEMENTATION")
+	}
+
+	addressStrings := r.CSV(prefix+"_ADDRESSES", reader.RetroKeys(prefix+"_ADDRESS"))
 	// WARNING: do not initialize w.Addresses to an empty slice
 	// or the defaults for nordvpn will not work.
 	for _, addressString := range addressStrings {
@@ -263,21 +253,19 @@ func (w *Wireguard) read(r *reader.Reader) (err error) {
 		w.Addresses = append(w.Addresses, address)
 	}
 
-	w.AllowedIPs, err = r.CSVNetipPrefixes("WIREGUARD_ALLOWED_IPS")
+	w.AllowedIPs, err = r.CSVNetipPrefixes(prefix + "_ALLOWED_IPS")
 	if err != nil {
 		return err // already wrapped
 	}
 
-	w.PersistentKeepaliveInterval, err = r.DurationPtr("WIREGUARD_PERSISTENT_KEEPALIVE_INTERVAL")
+	w.PersistentKeepaliveInterval, err = r.DurationPtr(prefix + "_PERSISTENT_KEEPALIVE_INTERVAL")
 	if err != nil {
 		return err
 	}
 
-	mtuPtr, err := r.Uint32Ptr("WIREGUARD_MTU")
+	w.MTU, err = r.Uint32Ptr(prefix + "_MTU")
 	if err != nil {
 		return err
-	} else if mtuPtr != nil {
-		w.MTU = *mtuPtr
 	}
 	return nil
 }

internal/configuration/settings/wireguardselection.go

@@ -152,18 +152,22 @@ func (w WireguardSelection) toLinesNode() (node *gotree.Node) {
 	return node
 }
 
-func (w *WireguardSelection) read(r *reader.Reader) (err error) {
-	w.EndpointIP, err = r.NetipAddr("WIREGUARD_ENDPOINT_IP", reader.RetroKeys("VPN_ENDPOINT_IP"))
+func (w *WireguardSelection) read(r *reader.Reader, amneziaWG bool) (err error) {
+	prefix := "WIREGUARD"
+	if amneziaWG {
+		prefix = "AMNEZIAWG"
+	}
+	w.EndpointIP, err = r.NetipAddr(prefix+"_ENDPOINT_IP", reader.RetroKeys("VPN_ENDPOINT_IP"))
 	if err != nil {
 		return fmt.Errorf("%w - note this MUST be an IP address, "+
 			"see https://github.com/qdm12/gluetun/issues/788", err)
 	}
 
-	w.EndpointPort, err = r.Uint16Ptr("WIREGUARD_ENDPOINT_PORT", reader.RetroKeys("VPN_ENDPOINT_PORT"))
+	w.EndpointPort, err = r.Uint16Ptr(prefix+"_ENDPOINT_PORT", reader.RetroKeys("VPN_ENDPOINT_PORT"))
 	if err != nil {
 		return err
 	}
 
-	w.PublicKey = r.String("WIREGUARD_PUBLIC_KEY", reader.ForceLowercase(false))
+	w.PublicKey = r.String(prefix+"_PUBLIC_KEY", reader.ForceLowercase(false))
 	return nil
 }

internal/configuration/sources/files/amneziawg.go

@@ -0,0 +1,84 @@
+package files
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"gopkg.in/ini.v1"
+)
+
+func (s *Source) lazyLoadAmneziawgConf() AmneziawgConfig {
+	if s.cached.amneziawgLoaded {
+		return s.cached.amneziawgConf
+	}
+
+	s.cached.amneziawgLoaded = true
+	var err error
+	s.cached.amneziawgConf, err = ParseAmneziawgConf(filepath.Join(s.rootDirectory, "amneziawg", "awg0.conf"))
+	if err != nil {
+		s.warner.Warnf("skipping Amneziawg config: %s", err)
+	}
+	return s.cached.amneziawgConf
+}
+
+type AmneziawgConfig struct {
+	Wireguard WireguardConfig
+	Jc        *string
+	Jmin      *string
+	Jmax      *string
+	S1        *string
+	S2        *string
+	S3        *string
+	S4        *string
+	H1        *string
+	H2        *string
+	H3        *string
+	H4        *string
+	I1        *string
+	I2        *string
+	I3        *string
+	I4        *string
+	I5        *string
+}
+
+func ParseAmneziawgConf(path string) (config AmneziawgConfig, err error) {
+	iniFile, err := ini.InsensitiveLoad(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return AmneziawgConfig{}, nil
+		}
+		return AmneziawgConfig{}, fmt.Errorf("loading ini from reader: %w", err)
+	}
+
+	config.Wireguard, err = ParseWireguardConf(path)
+	if err != nil {
+		return AmneziawgConfig{}, err
+	}
+
+	interfaceSection, err := iniFile.GetSection("Interface")
+	if err != nil {
+		// can never happen
+		return AmneziawgConfig{}, fmt.Errorf("getting interface section: %w", err)
+	}
+
+	config.Jc = getINIKeyFromSection(interfaceSection, "Jc")
+	config.Jmin = getINIKeyFromSection(interfaceSection, "Jmin")
+	config.Jmax = getINIKeyFromSection(interfaceSection, "Jmax")
+	config.S1 = getINIKeyFromSection(interfaceSection, "S1")
+	config.S2 = getINIKeyFromSection(interfaceSection, "S2")
+	config.S3 = getINIKeyFromSection(interfaceSection, "S3")
+	config.S4 = getINIKeyFromSection(interfaceSection, "S4")
+	config.H1 = getINIKeyFromSection(interfaceSection, "H1")
+	config.H2 = getINIKeyFromSection(interfaceSection, "H2")
+	config.H3 = getINIKeyFromSection(interfaceSection, "H3")
+	config.H4 = getINIKeyFromSection(interfaceSection, "H4")
+	config.I1 = getINIKeyFromSection(interfaceSection, "I1")
+	config.I2 = getINIKeyFromSection(interfaceSection, "I2")
+	config.I3 = getINIKeyFromSection(interfaceSection, "I3")
+	config.I4 = getINIKeyFromSection(interfaceSection, "I4")
+	config.I5 = getINIKeyFromSection(interfaceSection, "I5")
+
+	return config, nil
+}

internal/configuration/sources/files/amneziawg_test.go

@@ -0,0 +1,82 @@
+package files
+
+import (
+	"io/fs"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_Source_ParseAmneziawgConf(t *testing.T) {
+	t.Parallel()
+
+	t.Run("no_file", func(t *testing.T) {
+		t.Parallel()
+
+		noFile := filepath.Join(t.TempDir(), "doesnotexist")
+		wireguard, err := ParseAmneziawgConf(noFile)
+		assert.Equal(t, AmneziawgConfig{}, wireguard)
+		assert.NoError(t, err)
+	})
+
+	testCases := map[string]struct {
+		fileContent string
+		amneziawg   AmneziawgConfig
+		errMessage  string
+	}{
+		"ini_load_error": {
+			fileContent: "invalid",
+			errMessage:  "loading ini from reader: key-value delimiter not found: invalid",
+		},
+		"empty_file": {
+			errMessage: `getting interface section: section "interface" does not exist`,
+		},
+		"success": {
+			fileContent: `
+[Interface]
+PrivateKey = QOlCgyA/Sn/c/+YNTIEohrjm8IZV+OZ2AUFIoX20sk8=
+Address = 10.38.22.35/32
+DNS = 193.138.218.74
+Jc = 4
+H1 = 721391205
+I1 = <b 0x1234>
+
+[Peer]
+PresharedKey = YJ680VN+dGrdsWNjSFqZ6vvwuiNhbq502ZL3G7Q3o3g=
+`,
+			amneziawg: AmneziawgConfig{
+				Wireguard: WireguardConfig{
+					PrivateKey:   ptrTo("QOlCgyA/Sn/c/+YNTIEohrjm8IZV+OZ2AUFIoX20sk8="),
+					PreSharedKey: ptrTo("YJ680VN+dGrdsWNjSFqZ6vvwuiNhbq502ZL3G7Q3o3g="),
+					Addresses:    ptrTo("10.38.22.35/32"),
+				},
+				Jc: ptrTo("4"),
+				H1: ptrTo("721391205"),
+				I1: ptrTo("<b 0x1234>"),
+			},
+		},
+	}
+
+	for testName, testCase := range testCases {
+		t.Run(testName, func(t *testing.T) {
+			t.Parallel()
+
+			configFile := filepath.Join(t.TempDir(), "awg.conf")
+			const permission = fs.FileMode(0o600)
+			err := os.WriteFile(configFile, []byte(testCase.fileContent), permission)
+			require.NoError(t, err)
+
+			wireguard, err := ParseAmneziawgConf(configFile)
+
+			assert.Equal(t, testCase.amneziawg, wireguard)
+			if testCase.errMessage != "" {
+				assert.EqualError(t, err, testCase.errMessage)
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}

internal/configuration/sources/files/reader.go

@@ -13,6 +13,8 @@ type Source struct {
 	cached        struct {
 		wireguardLoaded bool
 		wireguardConf   WireguardConfig
+		amneziawgLoaded bool
+		amneziawgConf   AmneziawgConfig
 	}
 }
 
@@ -71,6 +73,11 @@ func (s *Source) Get(key string) (value string, isSet bool) {
 		return strPtrToStringIsSet(s.lazyLoadWireguardConf().EndpointPort)
 	}
 
+	value, isSet, matched := s.getAmneziawgKey(key)
+	if matched {
+		return value, isSet
+	}
+
 	value, isSet, err := ReadFromFile(path)
 	if err != nil {
 		s.warner.Warnf("skipping %s: reading file: %s", path, err)
@@ -78,6 +85,58 @@ func (s *Source) Get(key string) (value string, isSet bool) {
 	return value, isSet
 }
 
+func (s *Source) getAmneziawgKey(key string) (value string, isSet, matched bool) {
+	switch key {
+	case "amnezia_private_key":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.PrivateKey)
+	case "amnezia_preshared_key":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.PreSharedKey)
+	case "amnezia_addresses":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.Addresses)
+	case "amnezia_public_key":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.PublicKey)
+	case "amnezia_endpoint_ip":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.EndpointIP)
+	case "amnezia_endpoint_port":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.EndpointPort)
+	case "amnezia_jc":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Jc)
+	case "amnezia_jmin":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Jmin)
+	case "amnezia_jmax":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Jmax)
+	case "amnezia_s1":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().S1)
+	case "amnezia_s2":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().S2)
+	case "amnezia_s3":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().S3)
+	case "amnezia_s4":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().S4)
+	case "amnezia_h1":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().H1)
+	case "amnezia_h2":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().H2)
+	case "amnezia_h3":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().H3)
+	case "amnezia_h4":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().H4)
+	case "amnezia_i1":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().I1)
+	case "amnezia_i2":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().I2)
+	case "amnezia_i3":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().I3)
+	case "amnezia_i4":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().I4)
+	case "amnezia_i5":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().I5)
+	default:
+		return "", false, false
+	}
+	return value, isSet, true
+}
+
 func (s *Source) KeyTransform(key string) string {
 	switch key {
 	// TODO v4 remove these irregular cases

internal/configuration/sources/files/wireguard.go

@@ -3,6 +3,7 @@ package files
 import (
 	"errors"
 	"fmt"
+	"net"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -82,12 +83,15 @@ func parseWireguardPeerSection(peerSection *ini.Section) (
 	publicKey = getINIKeyFromSection(peerSection, "PublicKey")
 	endpoint := getINIKeyFromSection(peerSection, "Endpoint")
 	if endpoint != nil {
-		parts := strings.Split(*endpoint, ":")
-		endpointIP = &parts[0]
-		const partsWithPort = 2
-		if len(parts) >= partsWithPort {
-			endpointPort = new(string)
-			*endpointPort = strings.Join(parts[1:], ":")
+		host, port, err := net.SplitHostPort(*endpoint)
+		if err == nil {
+			endpointIP = &host
+			// IPv6 hosts contain colons; port is managed by the provider for those
+			if !strings.Contains(host, ":") {
+				endpointPort = &port
+			}
+		} else {
+			endpointIP = endpoint
 		}
 	}
 

internal/configuration/sources/files/wireguard_test.go

@@ -179,6 +179,11 @@ Endpoint = 1.2.3.4:51820`,
 			endpointIP:   ptrTo("1.2.3.4"),
 			endpointPort: ptrTo("51820"),
 		},
+		"ipv6_endpoint": {
+			iniData: `[Peer]
+Endpoint = [2a02:bbbb:aaaa:8075::10]:51820`,
+			endpointIP: ptrTo("2a02:bbbb:aaaa:8075::10"),
+		},
 	}
 
 	for testName, testCase := range testCases {

internal/configuration/sources/secrets/amneziawg.go

@@ -0,0 +1,27 @@
+package secrets
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/qdm12/gluetun/internal/configuration/sources/files"
+)
+
+func (s *Source) lazyLoadAmneziawgConf() files.AmneziawgConfig {
+	if s.cached.amneziawgLoaded {
+		return s.cached.amneziawgConf
+	}
+
+	path := os.Getenv("AMNEZIAWG_CONF_SECRETFILE")
+	if path == "" {
+		path = filepath.Join(s.rootDirectory, "amneziawg", "awg0.conf")
+	}
+
+	s.cached.amneziawgLoaded = true
+	var err error
+	s.cached.amneziawgConf, err = files.ParseAmneziawgConf(path)
+	if err != nil {
+		s.warner.Warnf("skipping Amneziawg config: %s", err)
+	}
+	return s.cached.amneziawgConf
+}

internal/configuration/sources/secrets/reader.go

@@ -15,6 +15,8 @@ type Source struct {
 	cached        struct {
 		wireguardLoaded bool
 		wireguardConf   files.WireguardConfig
+		amneziawgLoaded bool
+		amneziawgConf   files.AmneziawgConfig
 	}
 }
 
@@ -83,6 +85,11 @@ func (s *Source) Get(key string) (value string, isSet bool) {
 		return strPtrToStringIsSet(s.lazyLoadWireguardConf().EndpointPort)
 	}
 
+	value, isSet, matched := s.getAmneziaWg(key)
+	if matched {
+		return value, isSet
+	}
+
 	value, isSet, err := files.ReadFromFile(path)
 	if err != nil {
 		s.warner.Warnf("skipping %s: reading file: %s", path, err)
@@ -104,3 +111,55 @@ func (s *Source) KeyTransform(key string) string {
 		return key
 	}
 }
+
+func (s *Source) getAmneziaWg(key string) (value string, isSet, matched bool) {
+	switch key {
+	case "amneziawg_private_key":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.PrivateKey)
+	case "amneziawg_preshared_key":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.PreSharedKey)
+	case "amneziawg_addresses":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.Addresses)
+	case "amneziawg_public_key":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.PublicKey)
+	case "amneziawg_endpoint_ip":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.EndpointIP)
+	case "amneziawg_endpoint_port":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Wireguard.EndpointPort)
+	case "amneziawg_jc":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Jc)
+	case "amneziawg_jmin":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Jmin)
+	case "amneziawg_jmax":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().Jmax)
+	case "amneziawg_s1":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().S1)
+	case "amneziawg_s2":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().S2)
+	case "amneziawg_s3":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().S3)
+	case "amneziawg_s4":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().S4)
+	case "amneziawg_h1":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().H1)
+	case "amneziawg_h2":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().H2)
+	case "amneziawg_h3":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().H3)
+	case "amneziawg_h4":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().H4)
+	case "amneziawg_i1":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().I1)
+	case "amneziawg_i2":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().I2)
+	case "amneziawg_i3":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().I3)
+	case "amneziawg_i4":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().I4)
+	case "amneziawg_i5":
+		value, isSet = strPtrToStringIsSet(s.lazyLoadAmneziawgConf().I5)
+	default:
+		return "", false, false
+	}
+	return value, isSet, true
+}

internal/constants/vpn/protocol.go

@@ -1,6 +1,7 @@
 package vpn
 
 const (
+	AmneziaWg = "amneziawg"
 	OpenVPN   = "openvpn"
 	Wireguard = "wireguard"
 )

internal/dns/leak.go

@@ -0,0 +1,131 @@
+package dns
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"math"
+	"math/rand/v2"
+	"net/http"
+	"sort"
+	"strings"
+)
+
+func leakCheck(ctx context.Context, client *http.Client) (report string, err error) {
+	const sessionLength = 40
+	session := generateRandomString(sessionLength)
+
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+	type result struct {
+		dnsToCount map[string]uint
+		err        error
+	}
+	resultsCh := make(chan result)
+
+	const requestsCount = 5
+	for range requestsCount {
+		go func() {
+			dnsToCount, err := triggerDNSQuery(ctx, client, session)
+			resultsCh <- result{dnsToCount: dnsToCount, err: err}
+		}()
+	}
+
+	dnsToCount := make(map[string]uint)
+	for range requestsCount {
+		result := <-resultsCh
+		if result.err != nil {
+			if err == nil {
+				cancel()
+				err = fmt.Errorf("request failed: %w", result.err)
+			}
+			continue
+		}
+		for dns, count := range result.dnsToCount {
+			dnsToCount[dns] += count
+		}
+	}
+
+	if err != nil {
+		return "", err
+	}
+
+	return formatPercentages(dnsToCount), nil
+}
+
+func generateRandomString(length uint) string {
+	const charset = "abcdefghijklmnopqrstuvwxyz0123456789"
+	b := make([]byte, length)
+	for i := range b {
+		b[i] = charset[rand.IntN(len(charset))] //nolint:gosec
+	}
+	return string(b)
+}
+
+var errIPLeakSessionMismatch = errors.New("ipleak.net session mismatch")
+
+func triggerDNSQuery(ctx context.Context, client *http.Client, session string) (
+	dnsToCount map[string]uint, err error,
+) {
+	const randomLength = 12
+	randomPart := generateRandomString(randomLength)
+	url := fmt.Sprintf("https://%s-%s.ipleak.net/dnsdetection/", session, randomPart)
+	request, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, fmt.Errorf("creating request: %w", err)
+	}
+
+	response, err := client.Do(request)
+	if err != nil {
+		return nil, fmt.Errorf("performing request: %w", err)
+	}
+	defer response.Body.Close()
+
+	type ipLeakData struct {
+		Session string          `json:"session"`
+		IP      map[string]uint `json:"ip"`
+	}
+
+	decoder := json.NewDecoder(response.Body)
+	var data ipLeakData
+	err = decoder.Decode(&data)
+	if err != nil {
+		return nil, fmt.Errorf("decoding response: %w", err)
+	} else if data.Session != session {
+		return nil, fmt.Errorf("%w: expected %s, got %s", errIPLeakSessionMismatch, session, data.Session)
+	}
+
+	return data.IP, nil
+}
+
+func formatPercentages(data map[string]uint) string {
+	if len(data) == 0 {
+		return ""
+	}
+
+	var total uint
+	keys := make([]string, 0, len(data))
+	for k, v := range data {
+		total += v
+		keys = append(keys, k)
+	}
+
+	sort.Slice(keys, func(i, j int) bool {
+		if data[keys[i]] == data[keys[j]] {
+			return keys[i] < keys[j] // Tie-breaker: alphabetical
+		}
+		return data[keys[i]] > data[keys[j]]
+	})
+
+	results := make([]string, len(keys))
+	for i, key := range keys {
+		var pct float64
+		if total > 0 {
+			pct = math.Ceil((float64(data[key]) / float64(total)) * 100) //nolint:mnd
+		}
+		results[i] = fmt.Sprintf("%s (%.0f%%)", key, pct)
+	}
+
+	return strings.Join(results, ", ")
+}

internal/dns/leak_test.go

@@ -0,0 +1,22 @@
+package dns
+
+import (
+	"context"
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func Test_leakCheck(t *testing.T) {
+	t.Parallel()
+
+	const timeout = 10 * time.Second
+	ctx, cancel := context.WithTimeout(t.Context(), timeout)
+	t.Cleanup(cancel)
+	client := http.DefaultClient
+	report, err := leakCheck(ctx, client)
+	require.NoError(t, err)
+	require.NotEmpty(t, report)
+}

internal/dns/logger.go

@@ -3,6 +3,8 @@ package dns
 type Logger interface {
 	Debug(s string)
 	Info(s string)
+	Infof(format string, args ...any)
 	Warn(s string)
+	Warnf(format string, args ...any)
 	Error(s string)
 }

internal/dns/loop.go

@@ -22,6 +22,7 @@ type Loop struct {
 	server         *server.Server
 	filter         *mapfilter.Filter
 	localResolvers []netip.Addr
+	localSubnets   []netip.Prefix
 	resolvConf     string
 	client         *http.Client
 	logger         Logger
@@ -39,7 +40,7 @@ type Loop struct {
 const defaultBackoffTime = 10 * time.Second
 
 func NewLoop(settings settings.DNS,
-	client *http.Client, logger Logger,
+	client *http.Client, logger Logger, localSubnets []netip.Prefix,
 ) (loop *Loop, err error) {
 	start := make(chan struct{})
 	running := make(chan models.LoopStatus)
@@ -62,6 +63,7 @@ func NewLoop(settings settings.DNS,
 		state:         state,
 		server:        nil,
 		filter:        filter,
+		localSubnets:  localSubnets,
 		resolvConf:    "/etc/resolv.conf",
 		client:        client,
 		logger:        logger,

internal/dns/plaintext.go

@@ -1,37 +0,0 @@
-package dns
-
-import (
-	"net/netip"
-	"time"
-
-	"github.com/qdm12/dns/v2/pkg/nameserver"
-)
-
-func (l *Loop) useUnencryptedDNS(fallback bool) {
-	settings := l.GetSettings()
-
-	targetIP := settings.GetFirstPlaintextIPv4()
-
-	if fallback {
-		l.logger.Info("falling back on plaintext DNS at address " + targetIP.String())
-	} else {
-		l.logger.Info("using plaintext DNS at address " + targetIP.String())
-	}
-
-	const dialTimeout = 3 * time.Second
-	const defaultDNSPort = 53
-	settingsInternalDNS := nameserver.SettingsInternalDNS{
-		AddrPort: netip.AddrPortFrom(targetIP, defaultDNSPort),
-		Timeout:  dialTimeout,
-	}
-	nameserver.UseDNSInternally(settingsInternalDNS)
-
-	settingsSystemWide := nameserver.SettingsSystemDNS{
-		IPs:        []netip.Addr{targetIP},
-		ResolvPath: l.resolvConf,
-	}
-	err := nameserver.UseDNSSystemWide(settingsSystemWide)
-	if err != nil {
-		l.logger.Error(err.Error())
-	}
-}

internal/dns/run.go

@@ -2,9 +2,9 @@ package dns
 
 import (
 	"context"
-	"errors"
 
 	"github.com/qdm12/dns/v2/pkg/nameserver"
+	"github.com/qdm12/gluetun/internal/configuration/settings"
 	"github.com/qdm12/gluetun/internal/constants"
 )
 
@@ -18,15 +18,6 @@ func (l *Loop) Run(ctx context.Context, done chan<- struct{}) {
 		return
 	}
 
-	if *l.GetSettings().KeepNameserver {
-		l.logger.Warn("⚠️⚠️⚠️  keeping the default container nameservers, " +
-			"this will likely leak DNS traffic outside the VPN " +
-			"and go through your container network DNS outside the VPN tunnel!")
-	} else {
-		const fallback = false
-		l.useUnencryptedDNS(fallback)
-	}
-
 	select {
 	case <-l.start:
 	case <-ctx.Done():
@@ -38,39 +29,40 @@ func (l *Loop) Run(ctx context.Context, done chan<- struct{}) {
 		// Their values are to be used if DOT=off
 		var runError <-chan error
 
-		settings := l.GetSettings()
-		for !*settings.KeepNameserver && *settings.ServerEnabled {
+		var settings settings.DNS
+		for {
+			settings = l.GetSettings()
 			var err error
-			runError, err = l.setupServer(ctx)
+			runError, err = l.setupServer(ctx, settings)
 			if err == nil {
-				l.backoffTime = defaultBackoffTime
-				l.logger.Info("ready")
 				break
 			}
 
 			l.signalOrSetStatus(constants.Crashed)
-
 			if ctx.Err() != nil {
 				return
 			}
-
-			if !errors.Is(err, errUpdateBlockLists) {
-				const fallback = true
-				l.useUnencryptedDNS(fallback)
-			}
 			l.logAndWait(ctx, err)
-			settings = l.GetSettings()
+		}
+
+		l.backoffTime = defaultBackoffTime
+		l.logger.Infof("ready and using DNS server with %s upstream resolvers", settings.UpstreamType)
+
+		err = l.updateFiles(ctx, settings)
+		if err != nil {
+			l.logger.Warn("downloading block lists failed, skipping: " + err.Error())
 		}
 		l.signalOrSetStatus(constants.Running)
 
-		settings = l.GetSettings()
-		if !*settings.KeepNameserver && !*settings.ServerEnabled {
-			const fallback = false
-			l.useUnencryptedDNS(fallback)
-		}
-
 		l.userTrigger = false
 
+		report, err := leakCheck(ctx, l.client)
+		if err != nil {
+			l.logger.Warnf("running leak check: %s", err)
+		} else {
+			l.logger.Infof("leak check report: %s", report)
+		}
+
 		exitLoop := l.runWait(ctx, runError)
 		if exitLoop {
 			return
@@ -82,21 +74,13 @@ func (l *Loop) runWait(ctx context.Context, runError <-chan error) (exitLoop boo
 	for {
 		select {
 		case <-ctx.Done():
-			settings := l.GetSettings()
-			if !*settings.KeepNameserver && *settings.ServerEnabled {
-				l.stopServer()
-				// TODO revert OS and Go nameserver when exiting
-			}
+			l.stopServer()
+			// TODO revert OS and Go nameserver when exiting
 			return true
 		case <-l.stop:
 			l.userTrigger = true
 			l.logger.Info("stopping")
-			settings := l.GetSettings()
-			if !*settings.KeepNameserver && *settings.ServerEnabled {
-				const fallback = false
-				l.useUnencryptedDNS(fallback)
-				l.stopServer()
-			}
+			l.stopServer()
 			l.stopped <- struct{}{}
 		case <-l.start:
 			l.userTrigger = true
@@ -104,8 +88,6 @@ func (l *Loop) runWait(ctx context.Context, runError <-chan error) (exitLoop boo
 			return false
 		case err := <-runError: // unexpected error
 			l.statusManager.SetStatus(constants.Crashed)
-			const fallback = true
-			l.useUnencryptedDNS(fallback)
 			l.logAndWait(ctx, err)
 			return false
 		}

internal/dns/settings.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"net/netip"
+	"slices"
 
 	"github.com/qdm12/dns/v2/pkg/doh"
 	"github.com/qdm12/dns/v2/pkg/dot"
@@ -26,31 +27,23 @@ func (l *Loop) SetSettings(ctx context.Context, settings settings.DNS) (
 	return l.state.SetSettings(ctx, settings)
 }
 
-func buildServerSettings(settings settings.DNS,
+func buildServerSettings(userSettings settings.DNS,
 	filter *mapfilter.Filter, localResolvers []netip.Addr,
-	logger Logger) (
+	localSubnets []netip.Prefix, logger Logger) (
 	serverSettings server.Settings, err error,
 ) {
 	serverSettings.Logger = logger
 
-	providersData := provider.NewProviders()
-	upstreamResolvers := make([]provider.Provider, len(settings.Providers))
-	for i := range settings.Providers {
-		var err error
-		upstreamResolvers[i], err = providersData.Get(settings.Providers[i])
-		if err != nil {
-			panic(err) // this should already had been checked
-		}
-	}
+	upstreamResolvers := buildProviders(userSettings, localSubnets, logger)
 
 	ipVersion := "ipv4"
-	if *settings.IPv6 {
+	if *userSettings.IPv6 {
 		ipVersion = "ipv6"
 	}
 
 	var dialer server.Dialer
-	switch settings.UpstreamType {
-	case "dot":
+	switch userSettings.UpstreamType {
+	case settings.DNSUpstreamTypeDot:
 		dialerSettings := dot.Settings{
 			UpstreamResolvers: upstreamResolvers,
 			IPVersion:         ipVersion,
@@ -59,7 +52,7 @@ func buildServerSettings(settings settings.DNS,
 		if err != nil {
 			return server.Settings{}, fmt.Errorf("creating DNS over TLS dialer: %w", err)
 		}
-	case "doh":
+	case settings.DNSUpstreamTypeDoh:
 		dialerSettings := doh.Settings{
 			UpstreamResolvers: upstreamResolvers,
 			IPVersion:         ipVersion,
@@ -68,7 +61,7 @@ func buildServerSettings(settings settings.DNS,
 		if err != nil {
 			return server.Settings{}, fmt.Errorf("creating DNS over HTTPS dialer: %w", err)
 		}
-	case "plain":
+	case settings.DNSUpstreamTypePlain:
 		dialerSettings := plain.Settings{
 			UpstreamResolvers: upstreamResolvers,
 			IPVersion:         ipVersion,
@@ -78,11 +71,11 @@ func buildServerSettings(settings settings.DNS,
 			return server.Settings{}, fmt.Errorf("creating plain DNS dialer: %w", err)
 		}
 	default:
-		panic("unknown upstream type: " + settings.UpstreamType)
+		panic("unknown upstream type: " + userSettings.UpstreamType)
 	}
 	serverSettings.Dialer = dialer
 
-	if *settings.Caching {
+	if *userSettings.Caching {
 		lruCache, err := lru.New(lru.Settings{})
 		if err != nil {
 			return server.Settings{}, fmt.Errorf("creating LRU cache: %w", err)
@@ -123,3 +116,46 @@ func buildServerSettings(settings settings.DNS,
 
 	return serverSettings, nil
 }
+
+func buildProviders(userSettings settings.DNS, localSubnets []netip.Prefix,
+	logger Logger,
+) (providers []provider.Provider) {
+	userDefinedPlainAddresses := userSettings.UpstreamType == settings.DNSUpstreamTypePlain &&
+		len(userSettings.UpstreamPlainAddresses) > 0
+	if !userDefinedPlainAddresses {
+		providers = make([]provider.Provider, len(userSettings.Providers))
+		providersData := provider.NewProviders()
+		for i, providerName := range userSettings.Providers {
+			var err error
+			providers[i], err = providersData.Get(providerName)
+			if err != nil {
+				panic(err) // this should already had been checked
+			}
+		}
+		return providers
+	}
+
+	providers = make([]provider.Provider, len(userSettings.UpstreamPlainAddresses))
+	for i, addrPort := range userSettings.UpstreamPlainAddresses {
+		addr := addrPort.Addr()
+		if addr.IsPrivate() && !addr.IsLoopback() &&
+			!slices.ContainsFunc(localSubnets, func(prefix netip.Prefix) bool {
+				return prefix.Contains(addr)
+			}) {
+			logger.Warnf("DNS server address %s is not in local subnets, "+
+				"make sure to specify it in FIREWALL_OUTBOUND_SUBNETS as %s",
+				addr, netip.PrefixFrom(addr, addr.BitLen()))
+		}
+
+		providers[i] = provider.Provider{
+			Name: addrPort.String(),
+		}
+		if addr.Is4() {
+			providers[i].Plain.IPv4 = []netip.AddrPort{addrPort}
+		} else {
+			providers[i].Plain.IPv6 = []netip.AddrPort{addrPort}
+		}
+	}
+
+	return providers
+}

internal/dns/setup.go

@@ -2,26 +2,23 @@ package dns
 
 import (
 	"context"
-	"errors"
 	"fmt"
-	"net/netip"
 
-	"github.com/qdm12/dns/v2/pkg/check"
+	"github.com/qdm12/dns/v2/pkg/middlewares/filter/update"
 	"github.com/qdm12/dns/v2/pkg/nameserver"
 	"github.com/qdm12/dns/v2/pkg/server"
+	"github.com/qdm12/gluetun/internal/configuration/settings"
 )
 
-var errUpdateBlockLists = errors.New("cannot update filter block lists")
-
-func (l *Loop) setupServer(ctx context.Context) (runError <-chan error, err error) {
-	err = l.updateFiles(ctx)
+func (l *Loop) setupServer(ctx context.Context, settings settings.DNS) (runError <-chan error, err error) {
+	var updateSettings update.Settings
+	updateSettings.SetRebindingProtectionExempt(settings.Blacklist.RebindingProtectionExemptHostnames)
+	err = l.filter.Update(updateSettings)
 	if err != nil {
-		return nil, fmt.Errorf("%w: %w", errUpdateBlockLists, err)
+		return nil, fmt.Errorf("updating filter for rebinding protection: %w", err)
 	}
 
-	settings := l.GetSettings()
-
-	serverSettings, err := buildServerSettings(settings, l.filter, l.localResolvers, l.logger)
+	serverSettings, err := buildServerSettings(settings, l.filter, l.localResolvers, l.localSubnets, l.logger)
 	if err != nil {
 		return nil, fmt.Errorf("building server settings: %w", err)
 	}
@@ -38,23 +35,13 @@ func (l *Loop) setupServer(ctx context.Context) (runError <-chan error, err erro
 	l.server = server
 
 	// use internal DNS server
-	const defaultDNSPort = 53
-	nameserver.UseDNSInternally(nameserver.SettingsInternalDNS{
-		AddrPort: netip.AddrPortFrom(settings.ServerAddress, defaultDNSPort),
-	})
+	nameserver.UseDNSInternally(nameserver.SettingsInternalDNS{})
 	err = nameserver.UseDNSSystemWide(nameserver.SettingsSystemDNS{
-		IPs:        []netip.Addr{settings.ServerAddress},
 		ResolvPath: l.resolvConf,
 	})
 	if err != nil {
 		l.logger.Error(err.Error())
 	}
 
-	err = check.WaitForDNS(ctx, check.Settings{})
-	if err != nil {
-		l.stopServer()
-		return nil, err
-	}
-
 	return runError, nil
 }

internal/dns/state/settings.go

@@ -40,8 +40,6 @@ func (s *State) SetSettings(ctx context.Context, settings settings.DNS) (
 
 	// Restart
 	_, _ = s.statusApplier.ApplyStatus(ctx, constants.Stopped)
-	if *settings.ServerEnabled {
-		outcome, _ = s.statusApplier.ApplyStatus(ctx, constants.Running)
-	}
+	outcome, _ = s.statusApplier.ApplyStatus(ctx, constants.Running)
 	return outcome
 }

internal/dns/ticker.go

@@ -28,23 +28,12 @@ func (l *Loop) RunRestartTicker(ctx context.Context, done chan<- struct{}) {
 			return
 		case <-timer.C:
 			lastTick = l.timeNow()
-
-			status := l.GetStatus()
-			if status == constants.Running {
-				if err := l.updateFiles(ctx); err != nil {
-					l.statusManager.SetStatus(constants.Crashed)
-					l.logger.Error(err.Error())
-					l.logger.Warn("skipping DNS server restart due to failed files update")
-					settings := l.GetSettings()
-					timer.Reset(*settings.UpdatePeriod)
-					continue
+			settings := l.GetSettings()
+			if l.GetStatus() == constants.Running {
+				if err := l.updateFiles(ctx, settings); err != nil {
+					l.logger.Warn("updating block lists failed, skipping: " + err.Error())
 				}
 			}
-
-			_, _ = l.statusManager.ApplyStatus(ctx, constants.Stopped)
-			_, _ = l.statusManager.ApplyStatus(ctx, constants.Running)
-
-			settings := l.GetSettings()
 			timer.Reset(*settings.UpdatePeriod)
 		case <-l.updateTicker:
 			if !timer.Stop() {

internal/dns/update.go

@@ -6,11 +6,10 @@ import (
 
 	"github.com/qdm12/dns/v2/pkg/blockbuilder"
 	"github.com/qdm12/dns/v2/pkg/middlewares/filter/update"
+	"github.com/qdm12/gluetun/internal/configuration/settings"
 )
 
-func (l *Loop) updateFiles(ctx context.Context) (err error) {
-	settings := l.GetSettings()
-
+func (l *Loop) updateFiles(ctx context.Context, settings settings.DNS) (err error) {
 	l.logger.Info("downloading hostnames and IP block lists")
 	blacklistSettings := settings.Blacklist.ToBlockBuilderSettings(l.client)
 
@@ -37,7 +36,6 @@ func (l *Loop) updateFiles(ctx context.Context) (err error) {
 		IPPrefixes: result.BlockedIPPrefixes,
 	}
 	updateSettings.BlockHostnames(result.BlockedHostnames)
-	updateSettings.SetRebindingProtectionExempt(settings.Blacklist.RebindingProtectionExemptHostnames)
 	err = l.filter.Update(updateSettings)
 	if err != nil {
 		return fmt.Errorf("updating filter: %w", err)

internal/firewall/enable.go

@@ -22,9 +22,7 @@ func (c *Config) SetEnabled(ctx context.Context, enabled bool) (err error) {
 
 	if !enabled {
 		c.logger.Info("disabling...")
-		if err = c.disable(ctx); err != nil {
-			return fmt.Errorf("disabling firewall: %w", err)
-		}
+		c.restore(ctx)
 		c.enabled = false
 		c.logger.Info("disabled successfully")
 		return nil
@@ -41,64 +39,37 @@ func (c *Config) SetEnabled(ctx context.Context, enabled bool) (err error) {
 	return nil
 }
 
-func (c *Config) disable(ctx context.Context) (err error) {
-	if err = c.clearAllRules(ctx); err != nil {
-		return fmt.Errorf("clearing all rules: %w", err)
-	}
-	if err = c.setIPv4AllPolicies(ctx, "ACCEPT"); err != nil {
-		return fmt.Errorf("setting ipv4 policies: %w", err)
-	}
-	if err = c.setIPv6AllPolicies(ctx, "ACCEPT"); err != nil {
-		return fmt.Errorf("setting ipv6 policies: %w", err)
-	}
-
-	const remove = true
-	err = c.redirectPorts(ctx, remove)
-	if err != nil {
-		return fmt.Errorf("removing port redirections: %w", err)
-	}
-
-	return nil
-}
-
-// To use in defered call when enabling the firewall.
-func (c *Config) fallbackToDisabled(ctx context.Context) {
-	if ctx.Err() != nil {
-		return
-	}
-	if err := c.disable(ctx); err != nil {
-		c.logger.Error("failed reversing firewall changes: " + err.Error())
-	}
-}
-
 func (c *Config) enable(ctx context.Context) (err error) {
-	touched := false
-	if err = c.setIPv4AllPolicies(ctx, "DROP"); err != nil {
+	c.restore, err = c.impl.SaveAndRestore(ctx)
+	if err != nil {
+		return fmt.Errorf("saving firewall rules: %w", err)
+	}
+
+	defer func() {
+		if err != nil {
+			c.restore(context.Background())
+		}
+	}()
+
+	if err = c.impl.SetIPv4AllPolicies(ctx, "DROP"); err != nil {
 		return err
 	}
-	touched = true
 
-	if err = c.setIPv6AllPolicies(ctx, "DROP"); err != nil {
+	if err = c.impl.SetIPv6AllPolicies(ctx, "DROP"); err != nil {
+		return err
+	}
+
+	// Loopback traffic
+	if err = c.impl.AcceptInputThroughInterface(ctx, "lo"); err != nil {
 		return err
 	}
 
 	const remove = false
-
-	defer func() {
-		if touched && err != nil {
-			c.fallbackToDisabled(ctx)
-		}
-	}()
-
-	// Loopback traffic
-	if err = c.acceptInputThroughInterface(ctx, "lo", remove); err != nil {
-		return err
-	}
-	if err = c.acceptOutputThroughInterface(ctx, "lo", remove); err != nil {
+	if err = c.impl.AcceptOutputThroughInterface(ctx, "lo", remove); err != nil {
 		return err
 	}
 
-	if err = c.acceptEstablishedRelatedTraffic(ctx, remove); err != nil {
+	if err = c.impl.AcceptEstablishedRelatedTraffic(ctx); err != nil {
 		return err
 	}
 
@@ -108,7 +79,9 @@ func (c *Config) enable(ctx context.Context) (err error) {
 
 	localInterfaces := make(map[string]struct{}, len(c.localNetworks))
 	for _, network := range c.localNetworks {
-		if err := c.acceptOutputFromIPToSubnet(ctx, network.InterfaceName, network.IP, network.IPNet, remove); err != nil {
+		err = c.impl.AcceptOutputFromIPToSubnet(ctx,
+			network.InterfaceName, network.IP, network.IPNet, remove)
+		if err != nil {
 			return err
 		}
 
@@ -117,7 +90,7 @@ func (c *Config) enable(ctx context.Context) (err error) {
 			continue
 		}
 		localInterfaces[network.InterfaceName] = struct{}{}
-		err = c.acceptIpv6MulticastOutput(ctx, network.InterfaceName, remove)
+		err = c.impl.AcceptIpv6MulticastOutput(ctx, network.InterfaceName)
 		if err != nil {
 			return fmt.Errorf("accepting IPv6 multicast output: %w", err)
 		}
@@ -130,7 +103,7 @@ func (c *Config) enable(ctx context.Context) (err error) {
 	// Allows packets from any IP address to go through eth0 / local network
 	// to reach Gluetun.
 	for _, network := range c.localNetworks {
-		if err := c.acceptInputToSubnet(ctx, network.InterfaceName, network.IPNet, remove); err != nil {
+		if err := c.impl.AcceptInputToSubnet(ctx, network.InterfaceName, network.IPNet); err != nil {
 			return err
 		}
 	}
@@ -139,12 +112,12 @@ func (c *Config) enable(ctx context.Context) (err error) {
 		return err
 	}
 
-	err = c.redirectPorts(ctx, remove)
+	err = c.redirectPorts(ctx)
 	if err != nil {
 		return fmt.Errorf("redirecting ports: %w", err)
 	}
 
-	if err := c.runUserPostRules(ctx, c.customRulesPath, remove); err != nil {
+	if err := c.impl.RunUserPostRules(ctx, c.customRulesPath); err != nil {
 		return fmt.Errorf("running user defined post firewall rules: %w", err)
 	}
 
@@ -164,7 +137,7 @@ func (c *Config) allowVPNIP(ctx context.Context) (err error) {
 			continue
 		}
 		interfacesSeen[defaultRoute.NetInterface] = struct{}{}
-		err = c.acceptOutputTrafficToVPN(ctx, defaultRoute.NetInterface, c.vpnConnection, remove)
+		err = c.impl.AcceptOutputTrafficToVPN(ctx, defaultRoute.NetInterface, c.vpnConnection, remove)
 		if err != nil {
 			return fmt.Errorf("accepting output traffic through VPN: %w", err)
 		}
@@ -186,7 +159,7 @@ func (c *Config) allowOutboundSubnets(ctx context.Context) (err error) {
 			firewallUpdated = true
 
 			const remove = false
-			err := c.acceptOutputFromIPToSubnet(ctx, defaultRoute.NetInterface,
+			err := c.impl.AcceptOutputFromIPToSubnet(ctx, defaultRoute.NetInterface,
 				defaultRoute.AssignedIP, subnet, remove)
 			if err != nil {
 				return err
@@ -204,7 +177,7 @@ func (c *Config) allowInputPorts(ctx context.Context) (err error) {
 	for port, netInterfaces := range c.allowedInputPorts {
 		for netInterface := range netInterfaces {
 			const remove = false
-			err = c.acceptInputToPort(ctx, netInterface, port, remove)
+			err = c.impl.AcceptInputToPort(ctx, netInterface, port, remove)
 			if err != nil {
 				return fmt.Errorf("accepting input port %d on interface %s: %w",
 					port, netInterface, err)
@@ -214,9 +187,10 @@ func (c *Config) allowInputPorts(ctx context.Context) (err error) {
 	return nil
 }
 
-func (c *Config) redirectPorts(ctx context.Context, remove bool) (err error) {
+func (c *Config) redirectPorts(ctx context.Context) (err error) {
 	for _, portRedirection := range c.portRedirections {
-		err = c.redirectPort(ctx, portRedirection.interfaceName, portRedirection.sourcePort,
+		const remove = false
+		err = c.impl.RedirectPort(ctx, portRedirection.interfaceName, portRedirection.sourcePort,
 			portRedirection.destinationPort, remove)
 		if err != nil {
 			return err

internal/firewall/firewall.go

@@ -2,28 +2,28 @@ package firewall
 
 import (
 	"context"
+	"fmt"
 	"net/netip"
 	"sync"
 
+	"github.com/qdm12/gluetun/internal/firewall/iptables"
 	"github.com/qdm12/gluetun/internal/models"
 	"github.com/qdm12/gluetun/internal/routing"
 )
 
 type Config struct {
-	runner         CmdRunner
-	logger         Logger
-	iptablesMutex  sync.Mutex
-	ip6tablesMutex sync.Mutex
-	defaultRoutes  []routing.DefaultRoute
-	localNetworks  []routing.LocalNetwork
+	runner        CmdRunner
+	logger        Logger
+	defaultRoutes []routing.DefaultRoute
+	localNetworks []routing.LocalNetwork
 
-	// Fixed state
-	ipTables        string
-	ip6Tables       string
+	// Fixed
+	impl            firewallImpl
 	customRulesPath string
 
 	// State
 	enabled           bool
+	restore           func(context.Context)
 	vpnConnection     models.Connection
 	vpnIntf           string
 	outboundSubnets   []netip.Prefix
@@ -34,29 +34,23 @@ type Config struct {
 
 // NewConfig creates a new Config instance and returns an error
 // if no iptables implementation is available.
-func NewConfig(ctx context.Context, logger Logger,
+func NewConfig(ctx context.Context, logger, iptablesLogger Logger,
 	runner CmdRunner, defaultRoutes []routing.DefaultRoute,
 	localNetworks []routing.LocalNetwork,
 ) (config *Config, err error) {
-	iptables, err := checkIptablesSupport(ctx, runner, "iptables", "iptables-nft", "iptables-legacy")
+	impl, err := iptables.New(ctx, runner, iptablesLogger)
 	if err != nil {
-		return nil, err
-	}
-
-	ip6tables, err := findIP6tablesSupported(ctx, runner)
-	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("creating iptables firewall: %w", err)
 	}
 
 	return &Config{
 		runner:            runner,
 		logger:            logger,
 		allowedInputPorts: make(map[uint16]map[string]struct{}),
-		ipTables:          iptables,
-		ip6Tables:         ip6tables,
-		customRulesPath:   "/iptables/post-rules.txt",
 		// Obtained from routing
-		defaultRoutes: defaultRoutes,
-		localNetworks: localNetworks,
+		defaultRoutes:   defaultRoutes,
+		localNetworks:   localNetworks,
+		impl:            impl,
+		customRulesPath: "/iptables/post-rules.txt",
 	}, nil
 }

internal/firewall/interfaces.go

@@ -1,6 +1,12 @@
 package firewall
 
-import "os/exec"
+import (
+	"context"
+	"net/netip"
+	"os/exec"
+
+	"github.com/qdm12/gluetun/internal/models"
+)
 
 type CmdRunner interface {
 	Run(cmd *exec.Cmd) (output string, err error)
@@ -12,3 +18,27 @@ type Logger interface {
 	Warn(s string)
 	Error(s string)
 }
+
+type firewallImpl interface { //nolint:interfacebloat
+	SaveAndRestore(ctx context.Context) (restore func(context.Context), err error)
+	AcceptEstablishedRelatedTraffic(ctx context.Context) error
+	AcceptInputThroughInterface(ctx context.Context, intf string) error
+	AcceptInputToPort(ctx context.Context, intf string, port uint16, remove bool) error
+	AcceptInputToSubnet(ctx context.Context, intf string, subnet netip.Prefix) error
+	AcceptIpv6MulticastOutput(ctx context.Context, intf string) error
+	AcceptOutput(ctx context.Context, protocol, intf string,
+		ip netip.Addr, port uint16, remove bool) error
+	AcceptOutputFromIPToSubnet(ctx context.Context, intf string, assignedIP netip.Addr,
+		subnet netip.Prefix, remove bool) error
+	AcceptOutputThroughInterface(ctx context.Context, intf string, remove bool) error
+	AcceptOutputTrafficToVPN(ctx context.Context, intf string,
+		connection models.Connection, remove bool) error
+	RedirectPort(ctx context.Context, intf string, sourcePort,
+		destinationPort uint16, remove bool) error
+	RunUserPostRules(ctx context.Context, customRulesPath string) error
+	SetIPv4AllPolicies(ctx context.Context, policy string) error
+	SetIPv6AllPolicies(ctx context.Context, policy string) error
+	TempDropOutputTCPRST(ctx context.Context, src, dst netip.AddrPort, excludeMark int) (
+		revert func(ctx context.Context) error, err error)
+	Version(ctx context.Context) (version string, err error)
+}

internal/firewall/iptables/atomic.go

@@ -0,0 +1,87 @@
+package iptables
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+// SaveAndRestore saves the current iptables and ip6tables rules and
+// returns a restore function that can be called to restore the saved rules.
+func (c *Config) SaveAndRestore(ctx context.Context) (restore func(context.Context), err error) {
+	c.iptablesMutex.Lock()
+	defer c.iptablesMutex.Unlock()
+
+	return c.saveAndRestore(ctx)
+}
+
+// callers MUST always lock both the [Config] iptablesMutex and the ip6tablesMutex
+// before calling this function. Note the restore function does not interact with mutexes
+// so the caller must make sure the mutexes are locked when calling the restore function.
+func (c *Config) saveAndRestore(ctx context.Context) (restore func(context.Context), err error) {
+	restoreIPv4, err := c.saveAndRestoreIPv4(ctx)
+	if err != nil {
+		return nil, err
+	}
+	restoreIPv6, err := c.saveAndRestoreIPv6(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	restore = func(ctx context.Context) {
+		restoreIPv4(ctx)
+		if restoreIPv6 != nil {
+			restoreIPv6(ctx)
+		}
+	}
+	return restore, nil
+}
+
+// Callers of saveAndRestoreIPv4 MUST always lock the [Config] iptablesMutex
+// before calling this function.
+func (c *Config) saveAndRestoreIPv4(ctx context.Context) (restore func(context.Context), err error) {
+	cmd := exec.CommandContext(ctx, c.ipTables+"-save") //nolint:gosec
+	data, err := c.runner.Run(cmd)
+	if err != nil {
+		return nil, fmt.Errorf("saving IPv4 iptables: %w", err)
+	}
+
+	restore = func(ctx context.Context) {
+		cmd := exec.CommandContext(ctx, c.ipTables+"-restore") //nolint:gosec
+		cmd.Stdin = strings.NewReader(data)
+		output, err := c.runner.Run(cmd)
+		if err != nil {
+			c.logger.Warn(fmt.Sprintf("restoring IPv4 iptables failed: %s", makeRestoreErrorMessage(err, output, data)))
+		}
+	}
+	return restore, nil
+}
+
+// Callers of saveAndRestoreIPv6 MUST always lock the [Config] ip6tablesMutex
+// before calling this function.
+func (c *Config) saveAndRestoreIPv6(ctx context.Context) (restore func(context.Context), err error) {
+	if c.ip6Tables == "" {
+		return nil, nil //nolint:nilnil
+	}
+
+	cmd := exec.CommandContext(ctx, c.ip6Tables+"-save") //nolint:gosec
+	data, err := c.runner.Run(cmd)
+	if err != nil {
+		return nil, fmt.Errorf("saving IPv6 iptables: %w", err)
+	}
+
+	restore = func(ctx context.Context) {
+		cmd = exec.CommandContext(ctx, c.ip6Tables+"-restore") //nolint:gosec
+		cmd.Stdin = strings.NewReader(data)
+		output, err := c.runner.Run(cmd)
+		if err != nil {
+			c.logger.Warn(fmt.Sprintf("restoring IPv6 iptables failed: %s", makeRestoreErrorMessage(err, output, data)))
+		}
+	}
+	return restore, nil
+}
+
+func makeRestoreErrorMessage(err error, output, data string) string {
+	return fmt.Sprintf("%s: %s: restoring from data:\n%s", err, output, data)
+}

internal/firewall/iptables/cmd_matcher_test.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"fmt"

internal/firewall/iptables/delete.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"context"

internal/firewall/iptables/delete_test.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"context"
@@ -69,8 +69,8 @@ func Test_deleteIPTablesRule(t *testing.T) {
 		"invalid_instruction": {
 			instruction: "invalid",
 			errWrapped:  ErrIptablesCommandMalformed,
-			errMessage: "parsing iptables command: iptables command is malformed: " +
-				"fields count 1 is not even: \"invalid\"",
+			errMessage: "parsing iptables command: parsing \"invalid\": " +
+				"iptables command is malformed: flag \"invalid\" requires a value, but got none",
 		},
 		"list_error": {
 			instruction: "-t nat --delete PREROUTING -i tun0 -p tcp --dport 43716 -j REDIRECT --to-ports 5678",

internal/firewall/iptables/firewall.go

@@ -0,0 +1,35 @@
+package iptables
+
+import (
+	"context"
+	"sync"
+)
+
+type Config struct {
+	runner        CmdRunner
+	logger        Logger
+	iptablesMutex sync.Mutex
+
+	// Fixed state
+	ipTables  string
+	ip6Tables string
+}
+
+func New(ctx context.Context, runner CmdRunner, logger Logger) (*Config, error) {
+	iptables, err := checkIptablesSupport(ctx, runner, "iptables", "iptables-nft", "iptables-legacy")
+	if err != nil {
+		return nil, err
+	}
+
+	ip6tables, err := findIP6tablesSupported(ctx, runner)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Config{
+		runner:    runner,
+		logger:    logger,
+		ipTables:  iptables,
+		ip6Tables: ip6tables,
+	}, nil
+}

internal/firewall/iptables/interfaces.go

@@ -0,0 +1,12 @@
+package iptables
+
+import "os/exec"
+
+type CmdRunner interface {
+	Run(cmd *exec.Cmd) (output string, err error)
+}
+
+type Logger interface {
+	Debug(s string)
+	Warn(s string)
+}

internal/firewall/iptables/ip6tables.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"context"
@@ -14,8 +14,8 @@ import (
 func findIP6tablesSupported(ctx context.Context, runner CmdRunner) (
 	ip6tablesPath string, err error,
 ) {
-	ip6tablesPath, err = checkIptablesSupport(ctx, runner, "ip6tables", "ip6tables-nft", "ip6tables-legacy")
-	if errors.Is(err, ErrIPTablesNotSupported) {
+	ip6tablesPath, err = checkIptablesSupport(ctx, runner, "ip6tables", "ip6tables-legacy")
+	if errors.Is(err, ErrNotSupported) {
 		return "", nil
 	} else if err != nil {
 		return "", err
@@ -24,8 +24,23 @@ func findIP6tablesSupported(ctx context.Context, runner CmdRunner) (
 }
 
 func (c *Config) runIP6tablesInstructions(ctx context.Context, instructions []string) error {
+	c.iptablesMutex.Lock() // only one iptables command at once
+	defer c.iptablesMutex.Unlock()
+
+	restore, err := c.saveAndRestoreIPv6(ctx)
+	if err != nil {
+		return err
+	}
+	err = c.runIP6tablesInstructionsNoSave(ctx, instructions)
+	if err != nil {
+		restore(ctx)
+	}
+	return err
+}
+
+func (c *Config) runIP6tablesInstructionsNoSave(ctx context.Context, instructions []string) error {
 	for _, instruction := range instructions {
-		if err := c.runIP6tablesInstruction(ctx, instruction); err != nil {
+		if err := c.runIP6tablesInstructionNoSave(ctx, instruction); err != nil {
 			return err
 		}
 	}
@@ -33,11 +48,24 @@ func (c *Config) runIP6tablesInstructions(ctx context.Context, instructions []st
 }
 
 func (c *Config) runIP6tablesInstruction(ctx context.Context, instruction string) error {
+	c.iptablesMutex.Lock() // only one iptables command at once
+	defer c.iptablesMutex.Unlock()
+
+	restore, err := c.saveAndRestoreIPv6(ctx)
+	if err != nil {
+		return err
+	}
+	err = c.runIP6tablesInstructionNoSave(ctx, instruction)
+	if err != nil {
+		restore(ctx)
+	}
+	return err
+}
+
+func (c *Config) runIP6tablesInstructionNoSave(ctx context.Context, instruction string) error {
 	if c.ip6Tables == "" {
 		return nil
 	}
-	c.ip6tablesMutex.Lock() // only one ip6tables command at once
-	defer c.ip6tablesMutex.Unlock()
 
 	if isDeleteMatchInstruction(instruction) {
 		return deleteIPTablesRule(ctx, c.ip6Tables, instruction,
@@ -56,7 +84,7 @@ func (c *Config) runIP6tablesInstruction(ctx context.Context, instruction string
 
 var ErrPolicyNotValid = errors.New("policy is not valid")
 
-func (c *Config) setIPv6AllPolicies(ctx context.Context, policy string) error {
+func (c *Config) SetIPv6AllPolicies(ctx context.Context, policy string) error {
 	switch policy {
 	case "ACCEPT", "DROP":
 	default:

internal/firewall/iptables/iptables.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"context"
@@ -26,22 +26,6 @@ func appendOrDelete(remove bool) string {
 	return "--append"
 }
 
-// flipRule changes an append rule in a delete rule or a delete rule into an
-// append rule.
-func flipRule(rule string) string {
-	switch {
-	case strings.HasPrefix(rule, "-A"):
-		return strings.Replace(rule, "-A", "-D", 1)
-	case strings.HasPrefix(rule, "--append"):
-		return strings.Replace(rule, "--append", "-D", 1)
-	case strings.HasPrefix(rule, "-D"):
-		return strings.Replace(rule, "-D", "-A", 1)
-	case strings.HasPrefix(rule, "--delete"):
-		return strings.Replace(rule, "--delete", "-A", 1)
-	}
-	return rule
-}
-
 // Version obtains the version of the installed iptables.
 func (c *Config) Version(ctx context.Context) (string, error) {
 	cmd := exec.CommandContext(ctx, c.ipTables, "--version") //nolint:gosec
@@ -54,12 +38,28 @@ func (c *Config) Version(ctx context.Context) (string, error) {
 	if len(words) < minWords {
 		return "", fmt.Errorf("%w: %s", ErrIPTablesVersionTooShort, output)
 	}
-	return words[1], nil
+	return "iptables " + words[1], nil
 }
 
 func (c *Config) runIptablesInstructions(ctx context.Context, instructions []string) error {
+	c.iptablesMutex.Lock()
+	defer c.iptablesMutex.Unlock()
+
+	restore, err := c.saveAndRestoreIPv4(ctx)
+	if err != nil {
+		return err
+	}
+
+	err = c.runIptablesInstructionsNoSave(ctx, instructions)
+	if err != nil {
+		restore(ctx)
+	}
+	return err
+}
+
+func (c *Config) runIptablesInstructionsNoSave(ctx context.Context, instructions []string) error {
 	for _, instruction := range instructions {
-		if err := c.runIptablesInstruction(ctx, instruction); err != nil {
+		if err := c.runIptablesInstructionNoSave(ctx, instruction); err != nil {
 			return err
 		}
 	}
@@ -70,6 +70,19 @@ func (c *Config) runIptablesInstruction(ctx context.Context, instruction string)
 	c.iptablesMutex.Lock() // only one iptables command at once
 	defer c.iptablesMutex.Unlock()
 
+	restore, err := c.saveAndRestoreIPv4(ctx)
+	if err != nil {
+		return err
+	}
+
+	err = c.runIptablesInstructionNoSave(ctx, instruction)
+	if err != nil {
+		restore(ctx)
+	}
+	return err
+}
+
+func (c *Config) runIptablesInstructionNoSave(ctx context.Context, instruction string) error {
 	if isDeleteMatchInstruction(instruction) {
 		return deleteIPTablesRule(ctx, c.ipTables, instruction,
 			c.runner, c.logger)
@@ -85,14 +98,7 @@ func (c *Config) runIptablesInstruction(ctx context.Context, instruction string)
 	return nil
 }
 
-func (c *Config) clearAllRules(ctx context.Context) error {
-	return c.runMixedIptablesInstructions(ctx, []string{
-		"--flush",        // flush all chains
-		"--delete-chain", // delete all chains
-	})
-}
-
-func (c *Config) setIPv4AllPolicies(ctx context.Context, policy string) error {
+func (c *Config) SetIPv4AllPolicies(ctx context.Context, policy string) error {
 	switch policy {
 	case "ACCEPT", "DROP":
 	default:
@@ -105,22 +111,19 @@ func (c *Config) setIPv4AllPolicies(ctx context.Context, policy string) error {
 	})
 }
 
-func (c *Config) acceptInputThroughInterface(ctx context.Context, intf string, remove bool) error {
+func (c *Config) AcceptInputThroughInterface(ctx context.Context, intf string) error {
 	return c.runMixedIptablesInstruction(ctx, fmt.Sprintf(
-		"%s INPUT -i %s -j ACCEPT", appendOrDelete(remove), intf,
-	))
+		"--append INPUT -i %s -j ACCEPT", intf))
 }
 
-func (c *Config) acceptInputToSubnet(ctx context.Context, intf string,
-	destination netip.Prefix, remove bool,
-) error {
+func (c *Config) AcceptInputToSubnet(ctx context.Context, intf string, destination netip.Prefix) error {
 	interfaceFlag := "-i " + intf
 	if intf == "*" { // all interfaces
 		interfaceFlag = ""
 	}
 
-	instruction := fmt.Sprintf("%s INPUT %s -d %s -j ACCEPT",
-		appendOrDelete(remove), interfaceFlag, destination.String())
+	instruction := fmt.Sprintf("--append INPUT %s -d %s -j ACCEPT",
+		interfaceFlag, destination.String())
 
 	if destination.Addr().Is4() {
 		return c.runIptablesInstruction(ctx, instruction)
@@ -131,26 +134,23 @@ func (c *Config) acceptInputToSubnet(ctx context.Context, intf string,
 	return c.runIP6tablesInstruction(ctx, instruction)
 }
 
-func (c *Config) acceptOutputThroughInterface(ctx context.Context, intf string, remove bool) error {
+func (c *Config) AcceptOutputThroughInterface(ctx context.Context, intf string, remove bool) error {
 	return c.runMixedIptablesInstruction(ctx, fmt.Sprintf(
 		"%s OUTPUT -o %s -j ACCEPT", appendOrDelete(remove), intf,
 	))
 }
 
-func (c *Config) acceptEstablishedRelatedTraffic(ctx context.Context, remove bool) error {
+func (c *Config) AcceptEstablishedRelatedTraffic(ctx context.Context) error {
 	return c.runMixedIptablesInstructions(ctx, []string{
-		fmt.Sprintf("%s OUTPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT", appendOrDelete(remove)),
-		fmt.Sprintf("%s INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT", appendOrDelete(remove)),
+		"--append OUTPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT",
+		"--append INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT",
 	})
 }
 
-func (c *Config) acceptOutputTrafficToVPN(ctx context.Context,
+func (c *Config) AcceptOutputTrafficToVPN(ctx context.Context,
 	defaultInterface string, connection models.Connection, remove bool,
 ) error {
 	protocol := connection.Protocol
-	if protocol == "tcp-client" {
-		protocol = "tcp"
-	}
 	instruction := fmt.Sprintf("%s OUTPUT -d %s -o %s -p %s -m %s --dport %d -j ACCEPT",
 		appendOrDelete(remove), connection.IP, defaultInterface, protocol,
 		protocol, connection.Port)
@@ -162,8 +162,29 @@ func (c *Config) acceptOutputTrafficToVPN(ctx context.Context,
 	return c.runIP6tablesInstruction(ctx, instruction)
 }
 
+func (c *Config) AcceptOutput(ctx context.Context,
+	protocol, intf string, ip netip.Addr, port uint16, remove bool,
+) error {
+	interfaceFlag := "-o " + intf
+	if intf == "*" { // all interfaces
+		interfaceFlag = ""
+	}
+
+	instruction := fmt.Sprintf("%s OUTPUT -d %s %s -p %s -m %s --dport %d -j ACCEPT",
+		appendOrDelete(remove), ip, interfaceFlag, protocol, protocol, port)
+	if ip.Is4() {
+		return c.runIptablesInstruction(ctx, instruction)
+	} else if c.ip6Tables == "" {
+		return fmt.Errorf("accept output to VPN server: %w", ErrNeedIP6Tables)
+	}
+	return c.runIP6tablesInstruction(ctx, instruction)
+}
+
+// AcceptOutputFromIPToSubnet accepts outgoing traffic from sourceIP to destinationSubnet
+// on the interface intf. If intf is empty, it is set to "*" which means all interfaces.
+// If remove is true, the rule is removed instead of added.
 // Thanks to @npawelek.
-func (c *Config) acceptOutputFromIPToSubnet(ctx context.Context,
+func (c *Config) AcceptOutputFromIPToSubnet(ctx context.Context,
 	intf string, sourceIP netip.Addr, destinationSubnet netip.Prefix, remove bool,
 ) error {
 	doIPv4 := sourceIP.Is4() && destinationSubnet.Addr().Is4()
@@ -184,21 +205,24 @@ func (c *Config) acceptOutputFromIPToSubnet(ctx context.Context,
 	return c.runIP6tablesInstruction(ctx, instruction)
 }
 
-// NDP uses multicast address (theres no broadcast in IPv6 like ARP uses in IPv4).
-func (c *Config) acceptIpv6MulticastOutput(ctx context.Context,
-	intf string, remove bool,
-) error {
+// AcceptIpv6MulticastOutput accepts outgoing traffic to the IPv6 multicast address
+// ff02::1:ff00:0/104, which is used for NDP (Neighbor Discovery Protocol) to resolve
+// IPv6 addresses to MAC addresses. If intf is empty, it is set to "*" which means
+// all interfaces. If remove is true, the rule is removed instead of added.
+func (c *Config) AcceptIpv6MulticastOutput(ctx context.Context, intf string) error {
 	interfaceFlag := "-o " + intf
 	if intf == "*" { // all interfaces
 		interfaceFlag = ""
 	}
-	instruction := fmt.Sprintf("%s OUTPUT %s -d ff02::1:ff00:0/104 -j ACCEPT",
-		appendOrDelete(remove), interfaceFlag)
+	instruction := fmt.Sprintf("--append OUTPUT %s -d ff02::1:ff00:0/104 -j ACCEPT", interfaceFlag)
 	return c.runIP6tablesInstruction(ctx, instruction)
 }
 
-// Used for port forwarding, with intf set to tun.
-func (c *Config) acceptInputToPort(ctx context.Context, intf string, port uint16, remove bool) error {
+// AcceptInputToPort accepts incoming traffic on the specified port, for both TCP and UDP
+// protocols, on the interface intf. If intf is empty, it is set to "*" which means all interfaces.
+// If remove is true, the rule is removed instead of added. This is used for port forwarding, with
+// intf set to the VPN tunnel interface.
+func (c *Config) AcceptInputToPort(ctx context.Context, intf string, port uint16, remove bool) error {
 	interfaceFlag := "-i " + intf
 	if intf == "*" { // all interfaces
 		interfaceFlag = ""
@@ -209,8 +233,12 @@ func (c *Config) acceptInputToPort(ctx context.Context, intf string, port uint16
 	})
 }
 
-// Used for VPN server side port forwarding, with intf set to the VPN tunnel interface.
-func (c *Config) redirectPort(ctx context.Context, intf string,
+// RedirectPort redirects incoming traffic on the specified source port to the
+// specified destination port, for both TCP and UDP protocols, on the interface intf.
+// If intf is empty, it is set to "*" which means all interfaces. If remove is true,
+// the redirection is removed instead of added. This is used for VPN server side
+// port forwarding, with intf set to the VPN tunnel interface.
+func (c *Config) RedirectPort(ctx context.Context, intf string,
 	sourcePort, destinationPort uint16, remove bool,
 ) (err error) {
 	interfaceFlag := "-i " + intf
@@ -218,7 +246,15 @@ func (c *Config) redirectPort(ctx context.Context, intf string,
 		interfaceFlag = ""
 	}
 
-	err = c.runIptablesInstructions(ctx, []string{
+	c.iptablesMutex.Lock()
+	defer c.iptablesMutex.Unlock()
+
+	restore, err := c.saveAndRestore(ctx)
+	if err != nil {
+		return err
+	}
+
+	err = c.runIptablesInstructionsNoSave(ctx, []string{
 		fmt.Sprintf("-t nat %s PREROUTING %s -p tcp --dport %d -j REDIRECT --to-ports %d",
 			appendOrDelete(remove), interfaceFlag, sourcePort, destinationPort),
 		fmt.Sprintf("%s INPUT %s -p tcp -m tcp --dport %d -j ACCEPT",
@@ -229,11 +265,12 @@ func (c *Config) redirectPort(ctx context.Context, intf string,
 			appendOrDelete(remove), interfaceFlag, destinationPort),
 	})
 	if err != nil {
+		restore(ctx)
 		return fmt.Errorf("redirecting IPv4 source port %d to destination port %d on interface %s: %w",
 			sourcePort, destinationPort, intf, err)
 	}
 
-	err = c.runIP6tablesInstructions(ctx, []string{
+	err = c.runIP6tablesInstructionsNoSave(ctx, []string{
 		fmt.Sprintf("-t nat %s PREROUTING %s -p tcp --dport %d -j REDIRECT --to-ports %d",
 			appendOrDelete(remove), interfaceFlag, sourcePort, destinationPort),
 		fmt.Sprintf("%s INPUT %s -p tcp -m tcp --dport %d -j ACCEPT",
@@ -244,6 +281,7 @@ func (c *Config) redirectPort(ctx context.Context, intf string,
 			appendOrDelete(remove), interfaceFlag, destinationPort),
 	})
 	if err != nil {
+		restore(ctx) // just in case
 		errMessage := err.Error()
 		if strings.Contains(errMessage, "can't initialize ip6tables table `nat': Table does not exist") {
 			if !remove {
@@ -257,7 +295,7 @@ func (c *Config) redirectPort(ctx context.Context, intf string,
 	return nil
 }
 
-func (c *Config) runUserPostRules(ctx context.Context, filepath string, remove bool) error {
+func (c *Config) RunUserPostRules(ctx context.Context, filepath string) error {
 	file, err := os.OpenFile(filepath, os.O_RDONLY, 0)
 	if os.IsNotExist(err) {
 		return nil
@@ -273,16 +311,15 @@ func (c *Config) runUserPostRules(ctx context.Context, filepath string, remove b
 		return err
 	}
 	lines := strings.Split(string(b), "\n")
-	successfulRules := []string{}
-	defer func() {
-		// transaction-like rollback
-		if err == nil || ctx.Err() != nil {
-			return
-		}
-		for _, rule := range successfulRules {
-			_ = c.runIptablesInstruction(ctx, flipRule(rule))
-		}
-	}()
+
+	c.iptablesMutex.Lock()
+	defer c.iptablesMutex.Unlock()
+
+	restore, err := c.saveAndRestore(ctx)
+	if err != nil {
+		return err
+	}
+
 	for _, line := range lines {
 		var ipv4 bool
 		var rule string
@@ -309,23 +346,18 @@ func (c *Config) runUserPostRules(ctx context.Context, filepath string, remove b
 			continue
 		}
 
-		if remove {
-			rule = flipRule(rule)
-		}
-
 		switch {
 		case ipv4:
-			err = c.runIptablesInstruction(ctx, rule)
+			err = c.runIptablesInstructionNoSave(ctx, rule)
 		case c.ip6Tables == "":
 			err = fmt.Errorf("running user ip6tables rule: %w", ErrNeedIP6Tables)
 		default: // ipv6
-			err = c.runIP6tablesInstruction(ctx, rule)
+			err = c.runIP6tablesInstructionNoSave(ctx, rule)
 		}
 		if err != nil {
+			restore(ctx)
 			return err
 		}
-
-		successfulRules = append(successfulRules, rule)
 	}
 	return nil
 }

internal/firewall/iptables/iptablesmix.go

@@ -0,0 +1,45 @@
+package iptables
+
+import (
+	"context"
+)
+
+func (c *Config) runMixedIptablesInstructions(ctx context.Context, instructions []string) error {
+	c.iptablesMutex.Lock()
+	defer c.iptablesMutex.Unlock()
+
+	restore, err := c.saveAndRestore(ctx)
+	if err != nil {
+		return err
+	}
+
+	for _, instruction := range instructions {
+		if err := c.runMixedIptablesInstructionNoSave(ctx, instruction); err != nil {
+			restore(ctx)
+			return err
+		}
+	}
+	return nil
+}
+
+func (c *Config) runMixedIptablesInstruction(ctx context.Context, instruction string) error {
+	c.iptablesMutex.Lock()
+	defer c.iptablesMutex.Unlock()
+
+	restore, err := c.saveAndRestore(ctx)
+	if err != nil {
+		return err
+	}
+	err = c.runMixedIptablesInstructionNoSave(ctx, instruction)
+	if err != nil {
+		restore(ctx)
+	}
+	return err
+}
+
+func (c *Config) runMixedIptablesInstructionNoSave(ctx context.Context, instruction string) error {
+	if err := c.runIptablesInstructionNoSave(ctx, instruction); err != nil {
+		return err
+	}
+	return c.runIP6tablesInstructionNoSave(ctx, instruction)
+}

internal/firewall/iptables/list.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"errors"
@@ -26,10 +26,18 @@ type chainRule struct {
 	inputInterface  string       // input interface, for example "tun0" or "*""
 	outputInterface string       // output interface, for example "eth0" or "*""
 	source          netip.Prefix // source IP CIDR, for example 0.0.0.0/0. Must be valid.
+	sourcePort      uint16       // Not specified if set to zero.
 	destination     netip.Prefix // destination IP CIDR, for example 0.0.0.0/0. Must be valid.
 	destinationPort uint16       // Not specified if set to zero.
 	redirPorts      []uint16     // Not specified if empty.
 	ctstate         []string     // for example ["RELATED","ESTABLISHED"]. Can be empty.
+	tcpFlags        tcpFlags
+	mark            mark
+}
+
+type mark struct {
+	invert bool
+	value  uint
 }
 
 var ErrChainListMalformed = errors.New("iptables chain list output is malformed")
@@ -241,19 +249,23 @@ func parseChainRuleField(fieldIndex int, field string, rule *chainRule) (err err
 }
 
 func parseChainRuleOptionalFields(optionalFields []string, rule *chainRule) (err error) {
-	for i := 0; i < len(optionalFields); i++ {
-		key := optionalFields[i]
-		switch key {
-		case "tcp", "udp":
+	i := 0
+	for i < len(optionalFields) {
+		switch optionalFields[i] {
+		case "udp":
 			i++
-			value := optionalFields[i]
-			value = strings.TrimPrefix(value, "dpt:")
-			const base, bitLength = 10, 16
-			destinationPort, err := strconv.ParseUint(value, base, bitLength)
+			consumed, err := parseUDPOptional(optionalFields[i:], rule)
 			if err != nil {
-				return fmt.Errorf("parsing destination port %q: %w", value, err)
+				return fmt.Errorf("parsing UDP optional fields: %w", err)
 			}
-			rule.destinationPort = uint16(destinationPort)
+			i += consumed
+		case "tcp":
+			i++
+			consumed, err := parseTCPOptional(optionalFields[i:], rule)
+			if err != nil {
+				return fmt.Errorf("parsing TCP optional fields: %w", err)
+			}
+			i += consumed
 		case "redir":
 			i++
 			switch optionalFields[i] {
@@ -264,20 +276,136 @@ func parseChainRuleOptionalFields(optionalFields []string, rule *chainRule) (err
 					return fmt.Errorf("parsing redirection ports: %w", err)
 				}
 				rule.redirPorts = ports
+				i++
 			default:
-				return fmt.Errorf("%w: unexpected optional field: %s",
-					ErrChainRuleMalformed, optionalFields[i])
+				return fmt.Errorf("%w: unexpected %q after redir",
+					ErrChainRuleMalformed, optionalFields[1])
 			}
 		case "ctstate":
 			i++
 			rule.ctstate = strings.Split(optionalFields[i], ",")
+			i++
+		case "mark":
+			i++
+			mark, consumed, err := parseMark(optionalFields[i:])
+			if err != nil {
+				return fmt.Errorf("parsing mark: %w", err)
+			}
+			rule.mark = mark
+			i += consumed
 		default:
-			return fmt.Errorf("%w: unexpected optional field: %s", ErrChainRuleMalformed, key)
+			return fmt.Errorf("%w: unexpected optional field: %s",
+				ErrChainRuleMalformed, optionalFields[i])
 		}
 	}
 	return nil
 }
 
+var errUDPOptionalUnknown = errors.New("unknown UDP optional field")
+
+func parseUDPOptional(optionalFields []string, rule *chainRule) (consumed int, err error) {
+	for _, value := range optionalFields {
+		if !strings.ContainsRune(value, ':') {
+			// no longer a UDP-associated option
+			return consumed, nil
+		}
+		switch {
+		case strings.HasPrefix(value, "dpt:"):
+			rule.destinationPort, err = parseDestinationPort(value)
+			if err != nil {
+				return 0, fmt.Errorf("parsing destination port: %w", err)
+			}
+			consumed++
+		case strings.HasPrefix(value, "spt:"):
+			rule.sourcePort, err = parseSourcePort(value)
+			if err != nil {
+				return 0, fmt.Errorf("parsing source port: %w", err)
+			}
+			consumed++
+		default:
+			return 0, fmt.Errorf("%w: %s", errUDPOptionalUnknown, value)
+		}
+	}
+	return consumed, nil
+}
+
+var errTCPOptionalUnknown = errors.New("unknown TCP optional field")
+
+func parseTCPOptional(optionalFields []string, rule *chainRule) (consumed int, err error) {
+	for _, value := range optionalFields {
+		if !strings.ContainsRune(value, ':') {
+			// no longer a TCP-associated option
+			return consumed, nil
+		}
+		switch {
+		case strings.HasPrefix(value, "dpt:"):
+			rule.destinationPort, err = parseDestinationPort(value)
+			if err != nil {
+				return 0, fmt.Errorf("parsing destination port: %w", err)
+			}
+			consumed++
+		case strings.HasPrefix(value, "spt:"):
+			rule.sourcePort, err = parseSourcePort(value)
+			if err != nil {
+				return 0, fmt.Errorf("parsing source port: %w", err)
+			}
+			consumed++
+		case strings.HasPrefix(value, "flags:"):
+			rule.tcpFlags, err = parseTCPFlags(value)
+			if err != nil {
+				return 0, fmt.Errorf("parsing TCP flags: %w", err)
+			}
+			consumed++
+		default:
+			return 0, fmt.Errorf("%w: %s", errTCPOptionalUnknown, value)
+		}
+	}
+	return consumed, nil
+}
+
+func parseDestinationPort(value string) (port uint16, err error) {
+	value = strings.TrimPrefix(value, "dpt:")
+	return parsePort(value)
+}
+
+func parseSourcePort(value string) (port uint16, err error) {
+	value = strings.TrimPrefix(value, "spt:")
+	return parsePort(value)
+}
+
+var errTCPFlagsMalformed = errors.New("TCP flags are malformed")
+
+func parseTCPFlags(value string) (tcpFlags, error) {
+	value = strings.TrimPrefix(value, "flags:")
+	fields := strings.Split(value, "/")
+	const expectedFields = 2
+	if len(fields) != expectedFields {
+		return tcpFlags{}, fmt.Errorf("%w: expected format 'flags:<mask>/<comparison>' in %q",
+			errTCPFlagsMalformed, value)
+	}
+	maskFlags := strings.Split(fields[0], ",")
+	mask := make([]tcpFlag, len(maskFlags))
+	var err error
+	for i, maskFlag := range maskFlags {
+		mask[i], err = parseTCPFlag(maskFlag)
+		if err != nil {
+			return tcpFlags{}, fmt.Errorf("parsing TCP mask flags: %w", err)
+		}
+	}
+	comparisonFlags := strings.Split(fields[1], ",")
+	comparison := make([]tcpFlag, len(comparisonFlags))
+	for i, comparisonFlag := range comparisonFlags {
+		comparison[i], err = parseTCPFlag(comparisonFlag)
+		if err != nil {
+			return tcpFlags{}, fmt.Errorf("parsing TCP comparison flags: %w", err)
+		}
+	}
+	return tcpFlags{
+		mask:       mask,
+		comparison: comparison,
+	}, nil
+}
+
 func parsePortsCSV(s string) (ports []uint16, err error) {
 	if s == "" {
 		return nil, nil
@@ -286,16 +414,40 @@ func parsePortsCSV(s string) (ports []uint16, err error) {
 	fields := strings.Split(s, ",")
 	ports = make([]uint16, len(fields))
 	for i, field := range fields {
-		const base, bitLength = 10, 16
-		port, err := strconv.ParseUint(field, base, bitLength)
+		ports[i], err = parsePort(field)
 		if err != nil {
-			return nil, fmt.Errorf("parsing port %q: %w", field, err)
+			return nil, err
 		}
-		ports[i] = uint16(port)
 	}
 	return ports, nil
 }
 
+var errMarkValueMalformed = errors.New("mark value is malformed")
+
+func parseMark(optionalFields []string) (m mark, consumed int, err error) {
+	switch optionalFields[consumed] {
+	case "match":
+		consumed++
+		if optionalFields[consumed] == "!" {
+			m.invert = true
+			consumed++
+		}
+
+		const base = 0 // auto-detect
+		const bits = 32
+		value, err := strconv.ParseUint(optionalFields[consumed], base, bits)
+		if err != nil {
+			return mark{}, 0, fmt.Errorf("%w: %s", errMarkValueMalformed, optionalFields[consumed])
+		}
+		m.value = uint(value)
+		consumed++
+	default:
+		return mark{}, 0, fmt.Errorf("%w: unexpected mark mode field: %s",
+			ErrChainRuleMalformed, optionalFields[consumed])
+	}
+	return m, consumed, nil
+}
+
 var ErrLineNumberIsZero = errors.New("line number is zero")
 
 func parseLineNumber(s string) (n uint16, err error) {

internal/firewall/iptables/list_test.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"net/netip"

internal/firewall/iptables/mocks_generate_test.go

@@ -1,3 +1,3 @@
-package firewall
+package iptables
 
 //go:generate mockgen -destination=mocks_test.go -package $GOPACKAGE . CmdRunner,Logger

internal/firewall/iptables/mocks_test.go

@@ -1,8 +1,8 @@
 // Code generated by MockGen. DO NOT EDIT.
-// Source: github.com/qdm12/gluetun/internal/firewall (interfaces: CmdRunner,Logger)
+// Source: github.com/qdm12/gluetun/internal/firewall/iptables (interfaces: CmdRunner,Logger)
 
-// Package firewall is a generated GoMock package.
-package firewall
+// Package iptables is a generated GoMock package.
+package iptables
 
 import (
 	exec "os/exec"
@@ -84,30 +84,6 @@ func (mr *MockLoggerMockRecorder) Debug(arg0 interface{}) *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Debug", reflect.TypeOf((*MockLogger)(nil).Debug), arg0)
 }
 
-// Error mocks base method.
-func (m *MockLogger) Error(arg0 string) {
-	m.ctrl.T.Helper()
-	m.ctrl.Call(m, "Error", arg0)
-}
-
-// Error indicates an expected call of Error.
-func (mr *MockLoggerMockRecorder) Error(arg0 interface{}) *gomock.Call {
-	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Error", reflect.TypeOf((*MockLogger)(nil).Error), arg0)
-}
-
-// Info mocks base method.
-func (m *MockLogger) Info(arg0 string) {
-	m.ctrl.T.Helper()
-	m.ctrl.Call(m, "Info", arg0)
-}
-
-// Info indicates an expected call of Info.
-func (mr *MockLoggerMockRecorder) Info(arg0 interface{}) *gomock.Call {
-	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Info", reflect.TypeOf((*MockLogger)(nil).Info), arg0)
-}
-
 // Warn mocks base method.
 func (m *MockLogger) Warn(arg0 string) {
 	m.ctrl.T.Helper()

internal/firewall/iptables/parse.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"errors"
@@ -18,10 +18,13 @@ type iptablesInstruction struct {
 	inputInterface  string       // for example "tun0" or "" for any interface.
 	outputInterface string       // for example "tun0" or "" for any interface.
 	source          netip.Prefix // if not valid, then it is unspecified.
+	sourcePort      uint16       // if zero, there is no source port
 	destination     netip.Prefix // if not valid, then it is unspecified.
 	destinationPort uint16       // if zero, there is no destination port
 	toPorts         []uint16     // if empty, there is no redirection
 	ctstate         []string     // if empty, there is no ctstate
+	tcpFlags        tcpFlags
+	mark            mark
 }
 
 func (i *iptablesInstruction) setDefaults() {
@@ -43,6 +46,8 @@ func (i *iptablesInstruction) equalToRule(table, chain string, rule chainRule) (
 		return false
 	case i.destinationPort != rule.destinationPort:
 		return false
+	case i.sourcePort != rule.sourcePort:
+		return false
 	case !slices.Equal(i.toPorts, rule.redirPorts):
 		return false
 	case !slices.Equal(i.ctstate, rule.ctstate):
@@ -55,6 +60,11 @@ func (i *iptablesInstruction) equalToRule(table, chain string, rule chainRule) (
 		return false
 	case !ipPrefixesEqual(i.destination, rule.destination):
 		return false
+	case !slices.Equal(i.tcpFlags.mask, rule.tcpFlags.mask) ||
+		!slices.Equal(i.tcpFlags.comparison, rule.tcpFlags.comparison):
+		return false
+	case i.mark != rule.mark:
+		return false
 	default:
 		return true
 	}
@@ -77,26 +87,29 @@ func parseIptablesInstruction(s string) (instruction iptablesInstruction, err er
 		return iptablesInstruction{}, fmt.Errorf("%w: empty instruction", ErrIptablesCommandMalformed)
 	}
 	fields := strings.Fields(s)
-	if len(fields)%2 != 0 {
-		return iptablesInstruction{}, fmt.Errorf("%w: fields count %d is not even: %q",
-			ErrIptablesCommandMalformed, len(fields), s)
-	}
 
-	for i := 0; i < len(fields); i += 2 {
-		key := fields[i]
-		value := fields[i+1]
-		err = parseInstructionFlag(key, value, &instruction)
+	i := 0
+	for i < len(fields) {
+		consumed, err := parseInstructionFlag(fields[i:], &instruction)
 		if err != nil {
 			return iptablesInstruction{}, fmt.Errorf("parsing %q: %w", s, err)
 		}
+		i += consumed
 	}
 
 	instruction.setDefaults()
 	return instruction, nil
 }
 
-func parseInstructionFlag(key, value string, instruction *iptablesInstruction) (err error) {
-	switch key {
+func parseInstructionFlag(fields []string, instruction *iptablesInstruction) (consumed int, err error) {
+	consumed, err = preCheckInstructionFields(fields)
+	if err != nil {
+		return 0, err
+	}
+	flag := fields[0]
+	value := fields[1]
+
+	switch flag {
 	case "-t", "--table":
 		instruction.table = value
 	case "-D", "--delete":
@@ -109,7 +122,19 @@ func parseInstructionFlag(key, value string, instruction *iptablesInstruction) (
 		instruction.target = value
 	case "-p", "--protocol":
 		instruction.protocol = value
-	case "-m", "--match": // ignore match
+	case "-m", "--match":
+		consumed, err = parseMatchModule(fields, instruction)
+		if err != nil {
+			return 0, fmt.Errorf("parsing match module: %w", err)
+		}
+	case "--mark":
+		const base = 0 // auto-detect
+		const bits = 32
+		value, err := strconv.ParseUint(value, base, bits)
+		if err != nil {
+			return 0, fmt.Errorf("parsing mark value %q: %w", fields[2], err)
+		}
+		instruction.mark.value = uint(value)
 	case "-i", "--in-interface":
 		instruction.inputInterface = value
 	case "-o", "--out-interface":
@@ -117,37 +142,61 @@ func parseInstructionFlag(key, value string, instruction *iptablesInstruction) (
 	case "-s", "--source":
 		instruction.source, err = parseIPPrefix(value)
 		if err != nil {
-			return fmt.Errorf("parsing source IP CIDR: %w", err)
+			return 0, fmt.Errorf("parsing source IP CIDR: %w", err)
+		}
+	case "--sport":
+		instruction.sourcePort, err = parsePort(value)
+		if err != nil {
+			return 0, fmt.Errorf("parsing source port: %w", err)
 		}
 	case "-d", "--destination":
 		instruction.destination, err = parseIPPrefix(value)
 		if err != nil {
-			return fmt.Errorf("parsing destination IP CIDR: %w", err)
+			return 0, fmt.Errorf("parsing destination IP CIDR: %w", err)
 		}
 	case "--dport":
-		const base, bitLength = 10, 16
-		destinationPort, err := strconv.ParseUint(value, base, bitLength)
+		instruction.destinationPort, err = parsePort(value)
 		if err != nil {
-			return fmt.Errorf("parsing destination port: %w", err)
+			return 0, fmt.Errorf("parsing destination port: %w", err)
 		}
-		instruction.destinationPort = uint16(destinationPort)
 	case "--ctstate":
 		instruction.ctstate = strings.Split(value, ",")
 	case "--to-ports":
-		portStrings := strings.Split(value, ",")
-		instruction.toPorts = make([]uint16, len(portStrings))
-		for i, portString := range portStrings {
-			const base, bitLength = 10, 16
-			port, err := strconv.ParseUint(portString, base, bitLength)
-			if err != nil {
-				return fmt.Errorf("parsing port redirection: %w", err)
-			}
-			instruction.toPorts[i] = uint16(port)
+		instruction.toPorts, err = parseToPorts(value)
+		if err != nil {
+			return 0, fmt.Errorf("parsing port redirection: %w", err)
+		}
+	case "--tcp-flags":
+		mask, comparison := value, fields[2]
+		instruction.tcpFlags, err = parseTCPFlags(mask + "/" + comparison)
+		if err != nil {
+			return 0, fmt.Errorf("parsing TCP flags: %w", err)
 		}
 	default:
-		return fmt.Errorf("%w: unknown key %q", ErrIptablesCommandMalformed, key)
+		return 0, fmt.Errorf("%w: unknown key %q", ErrIptablesCommandMalformed, flag)
+	}
+	return consumed, nil
+}
+
+func preCheckInstructionFields(fields []string) (consumed int, err error) {
+	flag := fields[0]
+	// All flags use one value after the flag, except the following:
+	switch flag {
+	case "--tcp-flags": // -m can have 1 or 2 values
+		const expected = 3
+		if len(fields) < expected {
+			return 0, fmt.Errorf("%w: flag %q requires at least 2 values, but got %s",
+				ErrIptablesCommandMalformed, flag, strings.Join(fields, " "))
+		}
+		return expected, nil
+	default:
+		const expected = 2
+		if len(fields) < expected {
+			return 0, fmt.Errorf("%w: flag %q requires a value, but got none",
+				ErrIptablesCommandMalformed, flag)
+		}
+		return expected, nil
 	}
-	return nil
 }
 
 func parseIPPrefix(value string) (prefix netip.Prefix, err error) {
@@ -162,3 +211,52 @@ func parseIPPrefix(value string) (prefix netip.Prefix, err error) {
 	}
 	return netip.PrefixFrom(ip, ip.BitLen()), nil
 }
+
+func parsePort(value string) (port uint16, err error) {
+	const base, bitLength = 10, 16
+	portValue, err := strconv.ParseUint(value, base, bitLength)
+	if err != nil {
+		return 0, err
+	}
+	return uint16(portValue), nil
+}
+
+func parseMatchModule(fields []string, instruction *iptablesInstruction) (
+	consumed int, err error,
+) {
+	_ = fields[consumed] // -m or --match flag already detected
+	consumed++
+	switch fields[consumed] {
+	case "tcp", "udp":
+		consumed++
+		// for now ignore the protocol match since it's auto-loaded
+		// when parsing the -p/--protocol flag, and we don't need to
+		// parse it twice.
+	case "mark":
+		consumed++
+		switch fields[consumed] {
+		case "!":
+			consumed++
+			instruction.mark.invert = true
+		default:
+			return consumed, fmt.Errorf("%w: unsupported match mark with value: %s",
+				ErrIptablesCommandMalformed, fields[2])
+		}
+	default:
+		return 0, fmt.Errorf("%w: unknown match value: %s",
+			ErrIptablesCommandMalformed, fields[consumed])
+	}
+	return consumed, nil
+}
+
+func parseToPorts(value string) (toPorts []uint16, err error) {
+	portStrings := strings.Split(value, ",")
+	toPorts = make([]uint16, len(portStrings))
+	for i, portString := range portStrings {
+		toPorts[i], err = parsePort(portString)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return toPorts, nil
+}

internal/firewall/iptables/parse_test.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"net/netip"
@@ -23,7 +23,7 @@ func Test_parseIptablesInstruction(t *testing.T) {
 		"uneven_fields": {
 			s:          "-A",
 			errWrapped: ErrIptablesCommandMalformed,
-			errMessage: "iptables command is malformed: fields count 1 is not even: \"-A\"",
+			errMessage: "parsing \"-A\": iptables command is malformed: flag \"-A\" requires a value, but got none",
 		},
 		"unknown_key": {
 			s:          "-x something",

internal/firewall/iptables/support.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"context"
@@ -11,10 +11,10 @@ import (
 )
 
 var (
-	ErrNetAdminMissing      = errors.New("NET_ADMIN capability is missing")
-	ErrTestRuleCleanup      = errors.New("failed cleaning up test rule")
-	ErrInputPolicyNotFound  = errors.New("input policy not found")
-	ErrIPTablesNotSupported = errors.New("no iptables supported found")
+	ErrNetAdminMissing     = errors.New("NET_ADMIN capability is missing")
+	ErrTestRuleCleanup     = errors.New("failed cleaning up test rule")
+	ErrInputPolicyNotFound = errors.New("input policy not found")
+	ErrNotSupported        = errors.New("no iptables supported found")
 )
 
 func checkIptablesSupport(ctx context.Context, runner CmdRunner,
@@ -57,7 +57,7 @@ func checkIptablesSupport(ctx context.Context, runner CmdRunner,
 	}
 
 	return "", fmt.Errorf("%w: errors encountered are: %s",
-		ErrIPTablesNotSupported, strings.Join(allUnsupportedMessages, "; "))
+		ErrNotSupported, strings.Join(allUnsupportedMessages, "; "))
 }
 
 func testIptablesPath(ctx context.Context, path string,

internal/firewall/iptables/support_test.go

@@ -1,4 +1,4 @@
-package firewall
+package iptables
 
 import (
 	"context"
@@ -101,7 +101,7 @@ func Test_checkIptablesSupport(t *testing.T) {
 				return runner
 			},
 			iptablesPathsToTry: []string{"path1", "path2"},
-			errSentinel:        ErrIPTablesNotSupported,
+			errSentinel:        ErrNotSupported,
 			errMessage: "no iptables supported found: " +
 				"errors encountered are: " +
 				"path1: output 1 (exit code 4); " +

internal/firewall/iptables/tcp.go

@@ -0,0 +1,98 @@
+package iptables
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/netip"
+	"os"
+)
+
+type tcpFlags struct {
+	mask       []tcpFlag
+	comparison []tcpFlag
+}
+
+type tcpFlag uint8
+
+const (
+	tcpFlagFIN tcpFlag = 1 << iota
+	tcpFlagSYN
+	tcpFlagRST
+	tcpFlagPSH
+	tcpFlagACK
+	tcpFlagURG
+	tcpFlagECE
+	tcpFlagCWR
+)
+
+func (f tcpFlag) String() string {
+	switch f {
+	case tcpFlagFIN:
+		return "FIN"
+	case tcpFlagSYN:
+		return "SYN"
+	case tcpFlagRST:
+		return "RST"
+	case tcpFlagPSH:
+		return "PSH"
+	case tcpFlagACK:
+		return "ACK"
+	case tcpFlagURG:
+		return "URG"
+	case tcpFlagECE:
+		return "ECE"
+	case tcpFlagCWR:
+		return "CWR"
+	default:
+		panic(fmt.Sprintf("%s: %d", errTCPFlagUnknown, f))
+	}
+}
+
+var errTCPFlagUnknown = errors.New("unknown TCP flag")
+
+func parseTCPFlag(s string) (tcpFlag, error) {
+	allFlags := []tcpFlag{
+		tcpFlagFIN, tcpFlagSYN, tcpFlagRST, tcpFlagPSH,
+		tcpFlagACK, tcpFlagURG, tcpFlagECE, tcpFlagCWR,
+	}
+	for _, flag := range allFlags {
+		if s == fmt.Sprintf("%#02x", uint8(flag)) || s == flag.String() {
+			return flag, nil
+		}
+	}
+	return 0, fmt.Errorf("%w: %s", errTCPFlagUnknown, s)
+}
+
+var ErrMarkMatchModuleMissing = errors.New("kernel is missing the mark module libxt_mark.so")
+
+// TempDropOutputTCPRST temporarily drops outgoing TCP RST packets to the specified address and port,
+// for any TCP packets not marked with the excludeMark given.
+// This is necessary for TCP path MTU discovery to work, as the kernel will try to terminate the connection
+// by sending a TCP RST packet, although we want to handle the connection manually.
+func (c *Config) TempDropOutputTCPRST(ctx context.Context,
+	src, dst netip.AddrPort, excludeMark int) (
+	revert func(ctx context.Context) error, err error,
+) {
+	_, err = os.Stat("/usr/lib/xtables/libxt_mark.so")
+	if err != nil && errors.Is(err, os.ErrNotExist) {
+		return nil, fmt.Errorf("%w", ErrMarkMatchModuleMissing)
+	}
+
+	const template = "%s OUTPUT -p tcp -s %s --sport %d -d %s --dport %d " +
+		"--tcp-flags RST RST -m mark ! --mark %d -j DROP" //nolint:dupword
+	instruction := fmt.Sprintf(template, "--append", src.Addr(), src.Port(), dst.Addr(), dst.Port(), excludeMark)
+	revertInstruction := fmt.Sprintf(template, "--delete", src.Addr(), src.Port(), dst.Addr(), dst.Port(), excludeMark)
+	run := c.runIptablesInstruction
+	if dst.Addr().Is6() {
+		run = c.runIP6tablesInstruction
+	}
+	revert = func(ctx context.Context) error {
+		return run(ctx, revertInstruction)
+	}
+	err = run(ctx, instruction)
+	if err != nil {
+		return nil, fmt.Errorf("running instruction: %w", err)
+	}
+	return revert, nil
+}