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c32efd9118
Without this rule, Windows 8.1 and newer devices issue parallel DNS requests to DNS servers associated with all network adapters, even when "Override local DNS" is enabled and/or a Mullvad exit node is being used, resulting in DNS leaks. This also adds "disable-local-dns-override-via-nrpt" nodeAttr that can be used to disable the new behavior if needed. Fixes tailscale/corp#20718 Signed-off-by: Nick Khyl <nickk@tailscale.com>
79 lines
1.8 KiB
Go
79 lines
1.8 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package dns
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import (
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"bytes"
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"fmt"
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"os"
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"tailscale.com/control/controlknobs"
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"tailscale.com/health"
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"tailscale.com/types/logger"
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)
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type kv struct {
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k, v string
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}
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func (kv kv) String() string {
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return fmt.Sprintf("%s=%s", kv.k, kv.v)
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}
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// NewOSConfigurator created a new OS configurator.
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//
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// The health tracker may be nil; the knobs may be nil and are ignored on this platform.
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func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ *controlknobs.Knobs, interfaceName string) (OSConfigurator, error) {
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return newOSConfigurator(logf, health, interfaceName,
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newOSConfigEnv{
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rcIsResolvd: rcIsResolvd,
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fs: directFS{},
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})
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}
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// newOSConfigEnv are the funcs newOSConfigurator needs, pulled out for testing.
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type newOSConfigEnv struct {
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fs directFS
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rcIsResolvd func(resolvConfContents []byte) bool
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}
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func newOSConfigurator(logf logger.Logf, health *health.Tracker, interfaceName string, env newOSConfigEnv) (ret OSConfigurator, err error) {
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var debug []kv
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dbg := func(k, v string) {
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debug = append(debug, kv{k, v})
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}
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defer func() {
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if ret != nil {
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dbg("ret", fmt.Sprintf("%T", ret))
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}
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logf("dns: %v", debug)
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}()
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bs, err := env.fs.ReadFile(resolvConf)
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if os.IsNotExist(err) {
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dbg("rc", "missing")
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return newDirectManager(logf, health), nil
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}
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if err != nil {
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return nil, fmt.Errorf("reading /etc/resolv.conf: %w", err)
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}
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if env.rcIsResolvd(bs) {
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dbg("resolvd", "yes")
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return newResolvdManager(logf, interfaceName)
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}
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dbg("resolvd", "missing")
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return newDirectManager(logf, health), nil
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}
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func rcIsResolvd(resolvConfContents []byte) bool {
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// If we have the string "# resolvd:" in resolv.conf resolvd(8) is
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// managing things.
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if bytes.Contains(resolvConfContents, []byte("# resolvd:")) {
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return true
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}
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return false
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}
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