mirror of
https://github.com/qdm12/gluetun.git
synced 2026-05-06 20:10:11 +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
64 lines
1.6 KiB
Go
64 lines
1.6 KiB
Go
package dns
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import (
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"context"
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"fmt"
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"net"
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"net/netip"
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"github.com/qdm12/dns/v2/pkg/provider"
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)
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// Client is a simple plaintext UDP DNS client, to be used for healthchecks.
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// Note the client connects to a DNS server only over UDP on port 53,
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// because we don't want to use DoT or DoH and impact the TCP connections
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// when running a healthcheck.
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type Client struct {
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serverAddrs []netip.AddrPort
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dnsIPIndex int
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}
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func New() *Client {
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return &Client{
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serverAddrs: concatAddrPorts([][]netip.AddrPort{
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provider.Cloudflare().Plain.IPv4,
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provider.Google().Plain.IPv4,
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provider.Quad9().Plain.IPv4,
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provider.OpenDNS().Plain.IPv4,
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provider.LibreDNS().Plain.IPv4,
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provider.Quadrant().Plain.IPv4,
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provider.CiraProtected().Plain.IPv4,
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}),
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}
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}
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func concatAddrPorts(addrs [][]netip.AddrPort) []netip.AddrPort {
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var result []netip.AddrPort
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for _, addrList := range addrs {
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result = append(result, addrList...)
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}
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return result
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}
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func (c *Client) Check(ctx context.Context) error {
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dnsAddr := c.serverAddrs[c.dnsIPIndex].String()
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resolver := &net.Resolver{
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PreferGo: true,
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Dial: func(ctx context.Context, _, _ string) (net.Conn, error) {
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dialer := net.Dialer{}
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return dialer.DialContext(ctx, "udp", dnsAddr)
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},
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}
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ips, err := resolver.LookupIP(ctx, "ip", "github.com")
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switch {
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case err != nil:
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c.dnsIPIndex = (c.dnsIPIndex + 1) % len(c.serverAddrs)
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return fmt.Errorf("with DNS server %s: %w", dnsAddr, err)
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case len(ips) == 0:
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c.dnsIPIndex = (c.dnsIPIndex + 1) % len(c.serverAddrs)
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return fmt.Errorf("with DNS server %s: no IPs found from DNS lookup", dnsAddr)
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default:
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return nil
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}
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}
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