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f22185cae1
Fixes #1886.
Signed-off-by: David Anderson <danderson@tailscale.com>
(cherry picked from commit 6690f86ef4
)
229 lines
7.0 KiB
Go
229 lines
7.0 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package dns
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import (
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"runtime"
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"time"
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"inet.af/netaddr"
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"tailscale.com/net/dns/resolver"
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"tailscale.com/net/tsaddr"
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"tailscale.com/types/logger"
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"tailscale.com/util/dnsname"
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"tailscale.com/wgengine/monitor"
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)
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// We use file-ignore below instead of ignore because on some platforms,
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// the lint exception is necessary and on others it is not,
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// and plain ignore complains if the exception is unnecessary.
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//lint:file-ignore U1000 reconfigTimeout is used on some platforms but not others
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// reconfigTimeout is the time interval within which Manager.{Up,Down} should complete.
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//
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// This is particularly useful because certain conditions can cause indefinite hangs
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// (such as improper dbus auth followed by contextless dbus.Object.Call).
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// Such operations should be wrapped in a timeout context.
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const reconfigTimeout = time.Second
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// Manager manages system DNS settings.
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type Manager struct {
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logf logger.Logf
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resolver *resolver.Resolver
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os OSConfigurator
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config Config
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}
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// NewManagers created a new manager from the given config.
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func NewManager(logf logger.Logf, oscfg OSConfigurator, linkMon *monitor.Mon) *Manager {
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logf = logger.WithPrefix(logf, "dns: ")
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m := &Manager{
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logf: logf,
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resolver: resolver.New(logf, linkMon),
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os: oscfg,
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}
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m.logf("using %T", m.os)
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return m
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}
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func (m *Manager) Set(cfg Config) error {
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m.logf("Set: %+v", cfg)
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rcfg, ocfg, err := m.compileConfig(cfg)
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if err != nil {
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return err
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}
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m.logf("Resolvercfg: %+v", rcfg)
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m.logf("OScfg: %+v", ocfg)
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if err := m.resolver.SetConfig(rcfg); err != nil {
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return err
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}
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if err := m.os.SetDNS(ocfg); err != nil {
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return err
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}
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return nil
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}
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// compileConfig converts cfg into a quad-100 resolver configuration
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// and an OS-level configuration.
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func (m *Manager) compileConfig(cfg Config) (rcfg resolver.Config, ocfg OSConfig, err error) {
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authDomains := make(map[dnsname.FQDN]bool, len(cfg.AuthoritativeSuffixes))
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for _, dom := range cfg.AuthoritativeSuffixes {
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authDomains[dom] = true
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}
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addRoutes := func() {
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for suffix, resolvers := range cfg.Routes {
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// Don't add resolver routes for authoritative domains,
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// since they're meant to be authoritatively handled
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// internally.
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if authDomains[suffix] {
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continue
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}
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rcfg.Routes[suffix] = resolvers
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}
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}
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// The internal resolver always gets MagicDNS hosts and
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// authoritative suffixes, even if we don't propagate MagicDNS to
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// the OS.
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rcfg.Hosts = cfg.Hosts
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rcfg.LocalDomains = cfg.AuthoritativeSuffixes
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// Similarly, the OS always gets search paths.
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ocfg.SearchDomains = cfg.SearchDomains
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// Deal with trivial configs first.
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switch {
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case !cfg.needsOSResolver():
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// Set search domains, but nothing else. This also covers the
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// case where cfg is entirely zero, in which case these
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// configs clear all Tailscale DNS settings.
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return rcfg, ocfg, nil
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case cfg.hasDefaultResolversOnly():
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// Trivial CorpDNS configuration, just override the OS
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// resolver.
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ocfg.Nameservers = toIPsOnly(cfg.DefaultResolvers)
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return rcfg, ocfg, nil
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case cfg.hasDefaultResolvers():
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// Default resolvers plus other stuff always ends up proxying
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// through quad-100.
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rcfg.Routes = map[dnsname.FQDN][]netaddr.IPPort{
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".": cfg.DefaultResolvers,
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}
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addRoutes()
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ocfg.Nameservers = []netaddr.IP{tsaddr.TailscaleServiceIP()}
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return rcfg, ocfg, nil
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}
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// From this point on, we're figuring out split DNS
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// configurations. The possible cases don't return directly any
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// more, because as a final step we have to handle the case where
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// the OS can't do split DNS.
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// Workaround for
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// https://github.com/tailscale/corp/issues/1662. Even though
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// Windows natively supports split DNS, it only configures linux
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// containers using whatever the primary is, and doesn't apply
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// NRPT rules to DNS traffic coming from WSL.
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//
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// In order to make WSL work okay when the host Windows is using
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// Tailscale, we need to set up quad-100 as a "full proxy"
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// resolver, regardless of whether Windows itself can do split
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// DNS. We still make Windows do split DNS itself when it can, but
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// quad-100 will still have the full split configuration as well,
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// and so can service WSL requests correctly.
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//
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// This bool is used in a couple of places below to implement this
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// workaround.
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isWindows := runtime.GOOS == "windows"
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if cfg.singleResolverSet() != nil && m.os.SupportsSplitDNS() && !isWindows {
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// Split DNS configuration requested, where all split domains
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// go to the same resolvers. We can let the OS do it.
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ocfg.Nameservers = toIPsOnly(cfg.singleResolverSet())
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ocfg.MatchDomains = cfg.matchDomains()
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return rcfg, ocfg, nil
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}
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// Split DNS configuration with either multiple upstream routes,
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// or routes + MagicDNS, or just MagicDNS, or on an OS that cannot
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// split-DNS. Install a split config pointing at quad-100.
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rcfg.Routes = map[dnsname.FQDN][]netaddr.IPPort{}
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addRoutes()
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ocfg.Nameservers = []netaddr.IP{tsaddr.TailscaleServiceIP()}
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// If the OS can't do native split-dns, read out the underlying
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// resolver config and blend it into our config.
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if m.os.SupportsSplitDNS() {
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ocfg.MatchDomains = cfg.matchDomains()
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}
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if !m.os.SupportsSplitDNS() || isWindows {
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bcfg, err := m.os.GetBaseConfig()
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if err != nil {
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return resolver.Config{}, OSConfig{}, err
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}
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rcfg.Routes["."] = toIPPorts(bcfg.Nameservers)
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ocfg.SearchDomains = append(ocfg.SearchDomains, bcfg.SearchDomains...)
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}
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return rcfg, ocfg, nil
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}
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// toIPsOnly returns only the IP portion of ipps.
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// TODO: this discards port information on the assumption that we're
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// always pointing at port 53.
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// https://github.com/tailscale/tailscale/issues/1666 tracks making
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// that not true, if we ever want to.
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func toIPsOnly(ipps []netaddr.IPPort) (ret []netaddr.IP) {
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ret = make([]netaddr.IP, 0, len(ipps))
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for _, ipp := range ipps {
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ret = append(ret, ipp.IP)
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}
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return ret
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}
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func toIPPorts(ips []netaddr.IP) (ret []netaddr.IPPort) {
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ret = make([]netaddr.IPPort, 0, len(ips))
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for _, ip := range ips {
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ret = append(ret, netaddr.IPPort{IP: ip, Port: 53})
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}
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return ret
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}
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func (m *Manager) EnqueueRequest(bs []byte, from netaddr.IPPort) error {
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return m.resolver.EnqueueRequest(bs, from)
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}
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func (m *Manager) NextResponse() ([]byte, netaddr.IPPort, error) {
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return m.resolver.NextResponse()
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}
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func (m *Manager) Down() error {
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if err := m.os.Close(); err != nil {
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return err
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}
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m.resolver.Close()
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return nil
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}
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// Cleanup restores the system DNS configuration to its original state
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// in case the Tailscale daemon terminated without closing the router.
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// No other state needs to be instantiated before this runs.
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func Cleanup(logf logger.Logf, interfaceName string) {
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oscfg, err := NewOSConfigurator(logf, interfaceName)
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if err != nil {
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logf("creating dns cleanup: %v", err)
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return
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}
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dns := NewManager(logf, oscfg, nil)
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if err := dns.Down(); err != nil {
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logf("dns down: %v", err)
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}
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}
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