mirror of
https://github.com/qdm12/gluetun.git
synced 2026-05-07 04:20:12 +02:00
Quentin McGaw
4a78989d9d
- main reason being it's a burden to always define sentinel errors at global scope, wrap them with `%w` instead of using a string directly - only use sentinel errors when it has to be checked using `errors.Is` - replace all usage of these sentinel errors in `fmt.Errorf` with direct strings that were in the sentinel error - exclude the sentinel error definition requirement from .golangci.yml - update unit tests to use ContainersError instead of ErrorIs so it stays as a "not a change detector test" without requiring a sentinel error
87 lines
2.8 KiB
Go
87 lines
2.8 KiB
Go
package pmtud
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import (
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"context"
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"errors"
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"fmt"
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"net/netip"
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"time"
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"github.com/qdm12/gluetun/internal/firewall/iptables"
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"github.com/qdm12/gluetun/internal/pmtud/constants"
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"github.com/qdm12/gluetun/internal/pmtud/icmp"
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"github.com/qdm12/gluetun/internal/pmtud/tcp"
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)
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// PathMTUDiscover discovers the maximum MTU using both ICMP and TCP.
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// Multiple ICMP addresses and TCP addresses can be specified for redundancy.
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// ICMP PMTUD is run first. If successful, the range of possible MTU values to
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// check for TCP PMTUD is reduced to [maxMTU-150, maxMTU] where maxMTU is the
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// maximum MTU found with ICMP PMTUD. Otherwise, TCP PMTUD is run with the
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// whole range of possible MTU values up to the physical link MTU to check.
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// If the physicalLinkMTU is zero, it defaults to 1500 which is the ethernet standard MTU.
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// If the pingTimeout is zero, it defaults to 1 second.
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// If the logger is nil, a no-op logger is used.
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// It returns [ErrMTUNotFound] if the MTU could not be determined.
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func PathMTUDiscover(ctx context.Context, icmpAddrs []netip.Addr, tcpAddrs []netip.AddrPort,
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physicalLinkMTU uint32, tryTimeout time.Duration, fw tcp.Firewall, logger Logger) (
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mtu uint32, err error,
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) {
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if physicalLinkMTU == 0 {
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const ethernetStandardMTU = 1500
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physicalLinkMTU = ethernetStandardMTU
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}
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if tryTimeout == 0 {
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tryTimeout = time.Second
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}
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if logger == nil {
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logger = &noopLogger{}
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}
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// Try finding the MTU using ICMP
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maxPossibleMTU := physicalLinkMTU
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icmpSuccess := false
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for _, icmpIP := range icmpAddrs {
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mtu, err := icmp.PathMTUDiscover(ctx, icmpIP, physicalLinkMTU,
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tryTimeout, logger)
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switch {
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case err == nil:
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logger.Debugf("ICMP path MTU discovery against %s found maximum valid MTU %d", icmpIP, mtu)
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icmpSuccess = true
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maxPossibleMTU = mtu
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case errors.Is(err, icmp.ErrNotPermitted), errors.Is(err, icmp.ErrMTUNotFound):
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logger.Debugf("ICMP path MTU discovery failed: %s", err)
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default:
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return 0, fmt.Errorf("ICMP path MTU discovery: %w", err)
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}
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if icmpSuccess {
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break
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}
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}
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minMTU := constants.MinIPv4MTU
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if tcpAddrs[0].Addr().Is6() {
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minMTU = constants.MinIPv6MTU
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}
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if icmpSuccess {
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const mtuMargin = 150
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minMTU = max(maxPossibleMTU-mtuMargin, minMTU)
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}
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mtu, err = tcp.PathMTUDiscover(ctx, tcpAddrs, minMTU, maxPossibleMTU, tryTimeout, fw, logger)
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if err != nil {
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if errors.Is(err, iptables.ErrMarkMatchModuleMissing) {
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logger.Debugf("aborting TCP path MTU discovery: %s", err)
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if icmpSuccess {
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return maxPossibleMTU, nil // only rely on ICMP PMTUD results
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}
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}
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if icmpSuccess {
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return 0, fmt.Errorf("PMTUD succeeded with ICMP but failed with TCP "+
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"- discarding ICMP obtained MTU %d", maxPossibleMTU)
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}
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return 0, errors.New("PMTUD failed with both ICMP and TCP")
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}
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logger.Debugf("TCP path MTU discovery found maximum valid MTU %d", mtu)
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return mtu, nil
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}
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