mirror of
https://github.com/Control-D-Inc/ctrld.git
synced 2026-05-15 00:50:25 +02:00
cmd: allow import/running ctrld as library
This commit is contained in:
Cuong Manh Le
committed by
Cuong Manh Le
Cuong Manh Le
parent
4896563e3c
commit
829e93c079
@@ -0,0 +1,267 @@
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package cli
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import (
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"bufio"
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"bytes"
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"context"
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"fmt"
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"io"
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"net"
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"net/netip"
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"os/exec"
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"reflect"
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"strings"
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"syscall"
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"time"
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"github.com/insomniacslk/dhcp/dhcpv4/nclient4"
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"github.com/insomniacslk/dhcp/dhcpv6"
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"github.com/insomniacslk/dhcp/dhcpv6/client6"
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"tailscale.com/util/dnsname"
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"github.com/Control-D-Inc/ctrld/internal/dns"
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ctrldnet "github.com/Control-D-Inc/ctrld/internal/net"
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"github.com/Control-D-Inc/ctrld/internal/resolvconffile"
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)
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const resolvConfBackupFailedMsg = "open /etc/resolv.pre-ctrld-backup.conf: read-only file system"
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// allocate loopback ip
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// sudo ip a add 127.0.0.2/24 dev lo
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func allocateIP(ip string) error {
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cmd := exec.Command("ip", "a", "add", ip+"/24", "dev", "lo")
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if out, err := cmd.CombinedOutput(); err != nil {
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mainLog.Load().Error().Err(err).Msgf("allocateIP failed: %s", string(out))
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return err
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}
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return nil
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}
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func deAllocateIP(ip string) error {
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cmd := exec.Command("ip", "a", "del", ip+"/24", "dev", "lo")
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if err := cmd.Run(); err != nil {
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mainLog.Load().Error().Err(err).Msg("deAllocateIP failed")
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return err
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}
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return nil
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}
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const maxSetDNSAttempts = 5
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// set the dns server for the provided network interface
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func setDNS(iface *net.Interface, nameservers []string) error {
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r, err := dns.NewOSConfigurator(logf, iface.Name)
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if err != nil {
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mainLog.Load().Error().Err(err).Msg("failed to create DNS OS configurator")
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return err
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}
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ns := make([]netip.Addr, 0, len(nameservers))
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for _, nameserver := range nameservers {
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ns = append(ns, netip.MustParseAddr(nameserver))
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}
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osConfig := dns.OSConfig{
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Nameservers: ns,
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SearchDomains: []dnsname.FQDN{},
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}
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trySystemdResolve := false
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for i := 0; i < maxSetDNSAttempts; i++ {
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if err := r.SetDNS(osConfig); err != nil {
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if strings.Contains(err.Error(), "Rejected send message") &&
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strings.Contains(err.Error(), "org.freedesktop.network1.Manager") {
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mainLog.Load().Warn().Msg("Interfaces are managed by systemd-networkd, switch to systemd-resolve for setting DNS")
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trySystemdResolve = true
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break
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}
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// This error happens on read-only file system, which causes ctrld failed to create backup
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// for /etc/resolv.conf file. It is ok, because the DNS is still set anyway, and restore
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// DNS will fallback to use DHCP if there's no backup /etc/resolv.conf file.
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// The error format is controlled by us, so checking for error string is fine.
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// See: ../../internal/dns/direct.go:L278
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if r.Mode() == "direct" && strings.Contains(err.Error(), resolvConfBackupFailedMsg) {
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return nil
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}
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return err
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}
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currentNS := currentDNS(iface)
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if reflect.DeepEqual(currentNS, nameservers) {
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return nil
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}
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}
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if trySystemdResolve {
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// Stop systemd-networkd and retry setting DNS.
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if out, err := exec.Command("systemctl", "stop", "systemd-networkd").CombinedOutput(); err != nil {
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return fmt.Errorf("%s: %w", string(out), err)
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}
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args := []string{"--interface=" + iface.Name, "--set-domain=~"}
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for _, nameserver := range nameservers {
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args = append(args, "--set-dns="+nameserver)
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}
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for i := 0; i < maxSetDNSAttempts; i++ {
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if out, err := exec.Command("systemd-resolve", args...).CombinedOutput(); err != nil {
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return fmt.Errorf("%s: %w", string(out), err)
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}
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currentNS := currentDNS(iface)
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if reflect.DeepEqual(currentNS, nameservers) {
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return nil
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}
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time.Sleep(time.Second)
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}
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}
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mainLog.Load().Debug().Msg("DNS was not set for some reason")
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return nil
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}
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func resetDNS(iface *net.Interface) (err error) {
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defer func() {
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if err == nil {
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return
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}
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// Start systemd-networkd if present.
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if exe, _ := exec.LookPath("/lib/systemd/systemd-networkd"); exe != "" {
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_ = exec.Command("systemctl", "start", "systemd-networkd").Run()
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}
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if r, oerr := dns.NewOSConfigurator(logf, iface.Name); oerr == nil {
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_ = r.SetDNS(dns.OSConfig{})
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if err := r.Close(); err != nil {
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mainLog.Load().Error().Err(err).Msg("failed to rollback DNS setting")
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return
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}
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err = nil
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}
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}()
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var ns []string
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c, err := nclient4.New(iface.Name)
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if err != nil {
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return fmt.Errorf("nclient4.New: %w", err)
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}
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defer c.Close()
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ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
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defer cancel()
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lease, err := c.Request(ctx)
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if err != nil {
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return fmt.Errorf("nclient4.Request: %w", err)
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}
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for _, nameserver := range lease.ACK.DNS() {
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if nameserver.Equal(net.IPv4zero) {
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continue
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}
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ns = append(ns, nameserver.String())
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}
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// TODO(cuonglm): handle DHCPv6 properly.
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if ctrldnet.IPv6Available(ctx) {
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c := client6.NewClient()
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conversation, err := c.Exchange(iface.Name)
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if err != nil && !errAddrInUse(err) {
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mainLog.Load().Debug().Err(err).Msg("could not exchange DHCPv6")
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}
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for _, packet := range conversation {
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if packet.Type() == dhcpv6.MessageTypeReply {
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msg, err := packet.GetInnerMessage()
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if err != nil {
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mainLog.Load().Debug().Err(err).Msg("could not get inner DHCPv6 message")
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return nil
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}
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nameservers := msg.Options.DNS()
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for _, nameserver := range nameservers {
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ns = append(ns, nameserver.String())
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}
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}
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}
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}
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return ignoringEINTR(func() error {
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return setDNS(iface, ns)
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})
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}
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func currentDNS(iface *net.Interface) []string {
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for _, fn := range []getDNS{getDNSByResolvectl, getDNSBySystemdResolved, getDNSByNmcli, resolvconffile.NameServers} {
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if ns := fn(iface.Name); len(ns) > 0 {
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return ns
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}
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}
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return nil
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}
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func getDNSByResolvectl(iface string) []string {
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b, err := exec.Command("resolvectl", "dns", "-i", iface).Output()
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if err != nil {
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return nil
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}
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parts := strings.Fields(strings.SplitN(string(b), "%", 2)[0])
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if len(parts) > 2 {
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return parts[3:]
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}
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return nil
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}
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func getDNSBySystemdResolved(iface string) []string {
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b, err := exec.Command("systemd-resolve", "--status", iface).Output()
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if err != nil {
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return nil
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}
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return getDNSBySystemdResolvedFromReader(bytes.NewReader(b))
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}
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func getDNSBySystemdResolvedFromReader(r io.Reader) []string {
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scanner := bufio.NewScanner(r)
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var ret []string
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for scanner.Scan() {
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line := strings.TrimSpace(scanner.Text())
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if len(ret) > 0 {
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if net.ParseIP(line) != nil {
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ret = append(ret, line)
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}
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continue
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}
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after, found := strings.CutPrefix(line, "DNS Servers: ")
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if !found {
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continue
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}
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if net.ParseIP(after) != nil {
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ret = append(ret, after)
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}
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}
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return ret
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}
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func getDNSByNmcli(iface string) []string {
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b, err := exec.Command("nmcli", "dev", "show", iface).Output()
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if err != nil {
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return nil
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}
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s := bufio.NewScanner(bytes.NewReader(b))
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var dns []string
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do := func(line string) {
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parts := strings.SplitN(line, ":", 2)
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if len(parts) > 1 {
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dns = append(dns, strings.TrimSpace(parts[1]))
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}
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}
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for s.Scan() {
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line := s.Text()
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switch {
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case strings.HasPrefix(line, "IP4.DNS"):
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fallthrough
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case strings.HasPrefix(line, "IP6.DNS"):
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do(line)
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}
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}
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return dns
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}
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func ignoringEINTR(fn func() error) error {
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for {
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err := fn()
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if err != syscall.EINTR {
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return err
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}
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}
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}
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