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https://github.com/tailscale/tailscale.git
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38a83e937f
interfaces.Tailscale only returns an interface if it has at least one Tailscale
IP assigned to it. In the resolved DNS manager, when we're called upon to tear
down DNS config, the interface no longer has IPs.
Instead, look up the interface index on construction and reuse it throughout
the daemon lifecycle.
Fixes #1892.
Signed-off-by: David Anderson <dave@natulte.net>
(cherry picked from commit cfde997699
)
241 lines
6.2 KiB
Go
241 lines
6.2 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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"bytes"
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"context"
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"errors"
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"fmt"
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"io/ioutil"
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"os"
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"os/exec"
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"time"
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"github.com/godbus/dbus/v5"
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"tailscale.com/types/logger"
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"tailscale.com/util/cmpver"
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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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func NewOSConfigurator(logf logger.Logf, interfaceName string) (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 := ioutil.ReadFile("/etc/resolv.conf")
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if os.IsNotExist(err) {
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dbg("rc", "missing")
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return newDirectManager()
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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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switch resolvOwner(bs) {
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case "systemd-resolved":
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dbg("rc", "resolved")
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if err := dbusPing("org.freedesktop.resolve1", "/org/freedesktop/resolve1"); err != nil {
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dbg("resolved", "no")
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return newDirectManager()
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}
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if err := dbusPing("org.freedesktop.NetworkManager", "/org/freedesktop/NetworkManager/DnsManager"); err != nil {
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dbg("nm", "no")
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return newResolvedManager(logf, interfaceName)
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}
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dbg("nm", "yes")
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if err := nmIsUsingResolved(); err != nil {
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dbg("nm-resolved", "no")
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return newResolvedManager(logf, interfaceName)
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}
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dbg("nm-resolved", "yes")
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// Version of NetworkManager before 1.26.6 programmed resolved
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// incorrectly, such that NM's settings would always take
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// precedence over other settings set by other resolved
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// clients.
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//
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// If we're dealing with such a version, we have to set our
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// DNS settings through NM to have them take.
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//
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// However, versions 1.26.6 later both fixed the resolved
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// programming issue _and_ started ignoring DNS settings for
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// "unmanaged" interfaces - meaning NM 1.26.6 and later
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// actively ignore DNS configuration we give it. So, for those
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// NM versions, we can and must use resolved directly.
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old, err := nmVersionOlderThan("1.26.6")
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if err != nil {
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// Failed to figure out NM's version, can't make a correct
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// decision.
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return nil, fmt.Errorf("checking NetworkManager version: %v", err)
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}
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if old {
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dbg("nm-old", "yes")
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return newNMManager(interfaceName)
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}
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dbg("nm-old", "no")
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return newResolvedManager(logf, interfaceName)
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case "resolvconf":
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dbg("rc", "resolvconf")
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if err := resolvconfSourceIsNM(bs); err == nil {
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dbg("src-is-nm", "yes")
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if err := dbusPing("org.freedesktop.NetworkManager", "/org/freedesktop/NetworkManager/DnsManager"); err == nil {
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dbg("nm", "yes")
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old, err := nmVersionOlderThan("1.26.6")
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if err != nil {
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return nil, fmt.Errorf("checking NetworkManager version: %v", err)
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}
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if old {
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dbg("nm-old", "yes")
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return newNMManager(interfaceName)
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} else {
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dbg("nm-old", "no")
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}
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} else {
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dbg("nm", "no")
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}
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} else {
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dbg("src-is-nm", "no")
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}
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if _, err := exec.LookPath("resolvconf"); err != nil {
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dbg("resolvconf", "no")
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return newDirectManager()
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}
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dbg("resolvconf", "yes")
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return newResolvconfManager(logf)
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case "NetworkManager":
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dbg("rc", "nm")
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if err := dbusPing("org.freedesktop.NetworkManager", "/org/freedesktop/NetworkManager/DnsManager"); err != nil {
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dbg("nm", "no")
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return newDirectManager()
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}
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dbg("nm", "yes")
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old, err := nmVersionOlderThan("1.26.6")
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if err != nil {
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return nil, fmt.Errorf("checking NetworkManager version: %v", err)
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}
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if old {
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dbg("nm-old", "yes")
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return newNMManager(interfaceName)
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}
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dbg("nm-old", "no")
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return newDirectManager()
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default:
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dbg("rc", "unknown")
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return newDirectManager()
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}
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}
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func resolvconfSourceIsNM(resolvDotConf []byte) error {
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b := bytes.NewBuffer(resolvDotConf)
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cfg, err := readResolv(b)
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if err != nil {
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return fmt.Errorf("parsing /etc/resolv.conf: %w", err)
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}
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var (
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paths = []string{
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"/etc/resolvconf/run/interface/NetworkManager",
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"/run/resolvconf/interface/NetworkManager",
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"/var/run/resolvconf/interface/NetworkManager",
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"/run/resolvconf/interfaces/NetworkManager",
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"/var/run/resolvconf/interfaces/NetworkManager",
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}
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nmCfg OSConfig
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found bool
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)
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for _, path := range paths {
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nmCfg, err = readResolvFile(path)
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if os.IsNotExist(err) {
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continue
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} else if err != nil {
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return err
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}
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found = true
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break
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}
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if !found {
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return errors.New("NetworkManager resolvconf snippet not found")
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}
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if !nmCfg.Equal(cfg) {
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return errors.New("NetworkManager config not applied by resolvconf")
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}
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return nil
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}
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func nmVersionOlderThan(want string) (bool, error) {
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conn, err := dbus.SystemBus()
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if err != nil {
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// DBus probably not running.
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return false, err
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}
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nm := conn.Object("org.freedesktop.NetworkManager", dbus.ObjectPath("/org/freedesktop/NetworkManager"))
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v, err := nm.GetProperty("org.freedesktop.NetworkManager.Version")
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if err != nil {
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return false, err
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}
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version, ok := v.Value().(string)
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if !ok {
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return false, fmt.Errorf("unexpected type %T for NM version", v.Value())
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}
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return cmpver.Compare(version, want) < 0, nil
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}
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func nmIsUsingResolved() error {
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conn, err := dbus.SystemBus()
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if err != nil {
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// DBus probably not running.
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return err
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}
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nm := conn.Object("org.freedesktop.NetworkManager", dbus.ObjectPath("/org/freedesktop/NetworkManager/DnsManager"))
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v, err := nm.GetProperty("org.freedesktop.NetworkManager.DnsManager.Mode")
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if err != nil {
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return fmt.Errorf("getting NM mode: %w", err)
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}
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mode, ok := v.Value().(string)
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if !ok {
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return fmt.Errorf("unexpected type %T for NM DNS mode", v.Value())
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}
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if mode != "systemd-resolved" {
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return errors.New("NetworkManager is not using systemd-resolved for DNS")
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}
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return nil
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}
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func dbusPing(name, objectPath string) error {
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ctx, cancel := context.WithTimeout(context.Background(), time.Second)
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defer cancel()
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conn, err := dbus.SystemBus()
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if err != nil {
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// DBus probably not running.
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return err
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}
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obj := conn.Object(name, dbus.ObjectPath(objectPath))
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call := obj.CallWithContext(ctx, "org.freedesktop.DBus.Peer.Ping", 0)
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return call.Err
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}
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