cmd/ctrld: do set/reset DNS only when start/stop/uninstall

cmd/ctrld/cli.go

@@ -117,10 +117,6 @@ func initCLI() {
 			}
 			initCache()
 
-			if iface == "auto" {
-				iface = defaultIfaceName()
-			}
-
 			if daemon {
 				exe, err := os.Executable()
 				if err != nil {
@@ -173,8 +169,6 @@ func initCLI() {
 	runCmd.Flags().StringVarP(&cdUID, "cd", "", "", "Control D resolver uid")
 	runCmd.Flags().StringVarP(&homedir, "homedir", "", "", "")
 	_ = runCmd.Flags().MarkHidden("homedir")
-	runCmd.Flags().StringVarP(&iface, "iface", "", "", `Update DNS setting for iface, "auto" means the default interface gateway`)
-	_ = runCmd.Flags().MarkHidden("iface")
 
 	rootCmd.AddCommand(runCmd)
 
@@ -214,7 +208,8 @@ func initCLI() {
 				}
 			}
 
-			s, err := service.New(&prog{}, sc)
+			prog := &prog{}
+			s, err := service.New(prog, sc)
 			if err != nil {
 				stderrMsg(err.Error())
 				return
@@ -226,12 +221,12 @@ func initCLI() {
 				{s.Start, true},
 			}
 			if doTasks(tasks) {
-				stdoutMsg("Service started")
-				return
+				mainLog.Info().Msg("Service started")
+				prog.setDNS()
 			}
 		},
 	}
-	// Keep these flags in sync with runCmd above, except for "-d".
+	// Keep these flags in sync with runCmd above, except for "-d", "--iface".
 	startCmd.Flags().StringVarP(&configPath, "config", "c", "", "Path to config file")
 	startCmd.Flags().StringVarP(&configBase64, "base64_config", "", "", "Base64 encoded config")
 	startCmd.Flags().StringVarP(&listenAddress, "listen", "", "", "Listener address and port, in format: address:port")
@@ -249,13 +244,16 @@ func initCLI() {
 		Short:  "Stop the ctrld service",
 		Args:   cobra.NoArgs,
 		Run: func(cmd *cobra.Command, args []string) {
-			s, err := service.New(&prog{}, svcConfig)
+			prog := &prog{}
+			s, err := service.New(prog, svcConfig)
 			if err != nil {
 				stderrMsg(err.Error())
 				return
 			}
+			initLogging()
 			if doTasks([]task{{s.Stop, true}}) {
-				stdoutMsg("Service stopped")
+				mainLog.Info().Msg("Service stopped")
+				prog.resetDNS()
 			}
 		},
 	}
@@ -272,6 +270,7 @@ func initCLI() {
 				stderrMsg(err.Error())
 				return
 			}
+			initLogging()
 			if doTasks([]task{{s.Restart, true}}) {
 				stdoutMsg("Service restarted")
 			}
@@ -310,7 +309,8 @@ func initCLI() {
 		Short:  "Uninstall the ctrld service",
 		Args:   cobra.NoArgs,
 		Run: func(cmd *cobra.Command, args []string) {
-			s, err := service.New(&prog{}, svcConfig)
+			prog := &prog{}
+			s, err := service.New(prog, svcConfig)
 			if err != nil {
 				stderrMsg(err.Error())
 				return
@@ -319,8 +319,10 @@ func initCLI() {
 				{s.Stop, false},
 				{s.Uninstall, true},
 			}
+			initLogging()
 			if doTasks(tasks) {
-				stdoutMsg("Service uninstalled")
+				mainLog.Info().Msg("Service uninstalled")
+				prog.resetDNS()
 				return
 			}
 		},
@@ -391,9 +393,7 @@ func initCLI() {
 		Use:    "start",
 		Short:  "Quick start service and configure DNS on interface",
 		Run: func(cmd *cobra.Command, args []string) {
-			if !cmd.Flags().Changed("iface") {
-				os.Args = append(os.Args, "--iface="+ifaceStartStop)
-			}
+			iface = ifaceStartStop
 			startCmd.Run(cmd, args)
 		},
 	}
@@ -405,9 +405,7 @@ func initCLI() {
 		Use:    "stop",
 		Short:  "Quick stop service and remove DNS from interface",
 		Run: func(cmd *cobra.Command, args []string) {
-			if !cmd.Flags().Changed("iface") {
-				os.Args = append(os.Args, "--iface="+ifaceStartStop)
-			}
+			iface = ifaceStartStop
 			stopCmd.Run(cmd, args)
 		},
 	}

cmd/ctrld/main.go

@@ -3,7 +3,6 @@ package main
 import (
 	"fmt"
 	"io"
-	"net"
 	"os"
 	"path/filepath"
 	"time"
@@ -36,7 +35,6 @@ var (
 
 	cdUID          string
 	iface          string
-	netIface       *net.Interface
 	ifaceStartStop string
 )
 

cmd/ctrld/os_linux.go

@@ -3,16 +3,18 @@ package main
 import (
 	"bufio"
 	"bytes"
+	"context"
+	"fmt"
 	"net"
 	"net/netip"
 	"os/exec"
 	"strings"
 	"syscall"
+	"time"
 
-	"github.com/insomniacslk/dhcp/dhcpv4"
-	"github.com/insomniacslk/dhcp/dhcpv4/client4"
+	"github.com/insomniacslk/dhcp/dhcpv4/nclient4"
 	"github.com/insomniacslk/dhcp/dhcpv6"
-	"github.com/insomniacslk/dhcp/dhcpv6/client6"
+	"github.com/insomniacslk/dhcp/dhcpv6/nclient6"
 	"tailscale.com/net/dns"
 	"tailscale.com/util/dnsname"
 
@@ -63,40 +65,56 @@ func setDNS(iface *net.Interface, nameservers []string) error {
 
 func resetDNS(iface *net.Interface) error {
 	var ns []string
-	c := client4.NewClient()
-	conversation, err := c.Exchange(iface.Name)
+	c, err := nclient4.New(iface.Name)
 	if err != nil {
-		return err
+		return fmt.Errorf("nclient4.New: %w", err)
 	}
-	for _, packet := range conversation {
-		if packet.MessageType() == dhcpv4.MessageTypeAck {
-			nameservers := packet.DNS()
-			for _, nameserver := range nameservers {
-				ns = append(ns, nameserver.String())
-			}
+	defer c.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+	defer cancel()
+	lease, err := c.Request(ctx)
+	if err != nil {
+		return fmt.Errorf("nclient4.Request: %w", err)
+	}
+	for _, nameserver := range lease.ACK.DNS() {
+		if nameserver.Equal(net.IPv4zero) {
+			continue
 		}
+		ns = append(ns, nameserver.String())
 	}
 
 	if supportsIPv6() {
-		c := client6.NewClient()
-		conversation, err := c.Exchange(iface.Name)
+		c, err := nclient6.New(iface.Name)
 		if err != nil {
-			mainLog.Warn().Err(err).Msg("could not exchange DHCPv6")
+			mainLog.Warn().Err(err).Msg("could not create DHCPv6 client")
+			return nil
 		}
-		for _, packet := range conversation {
-			if packet.Type() == dhcpv6.MessageTypeReply {
-				msg, err := packet.GetInnerMessage()
-				if err != nil {
-					return err
-				}
-				nameservers := msg.Options.DNS()
-				for _, nameserver := range nameservers {
-					ns = append(ns, nameserver.String())
-				}
-			}
-		}
-	}
+		defer c.Close()
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+		defer cancel()
 
+		solicit, err := dhcpv6.NewSolicit(iface.HardwareAddr)
+		if err != nil {
+			return fmt.Errorf("dhcpv6.NewSolicit: %w", err)
+		}
+		advertise, err := dhcpv6.NewAdvertiseFromSolicit(solicit)
+		if err != nil {
+			return fmt.Errorf("dhcpv6.NewAdvertiseFromSolicit: %w", err)
+		}
+		msg, err := c.Request(ctx, advertise)
+		if err != nil {
+			return fmt.Errorf("nclient6.Request: %w", err)
+		}
+		nameservers := msg.Options.DNS()
+		for _, nameserver := range nameservers {
+			if nameserver.Equal(net.IPv6zero) {
+				continue
+			}
+			ns = append(ns, nameserver.String())
+		}
+
+	}
 	return ignoringEINTR(func() error {
 		return setDNS(iface, ns)
 	})

cmd/ctrld/prog.go

@@ -35,7 +35,6 @@ func (p *prog) Start(s service.Service) error {
 }
 
 func (p *prog) run() {
-	p.setDNS()
 	if p.cfg.Service.CacheEnable {
 		cacher, err := dnscache.NewLRUCache(p.cfg.Service.CacheSize)
 		if err != nil {
@@ -170,7 +169,6 @@ func (p *prog) Stop(s service.Service) error {
 		mainLog.Error().Err(err).Msg("de-allocate ip failed")
 		return err
 	}
-	p.resetDNS()
 	mainLog.Info().Msg("Service stopped")
 	return nil
 }
@@ -195,18 +193,23 @@ func (p *prog) deAllocateIP() error {
 }
 
 func (p *prog) setDNS() {
+	if cfg.Listener == nil || cfg.Listener["0"] == nil {
+		return
+	}
 	if iface == "" {
 		return
 	}
+	if iface == "auto" {
+		iface = defaultIfaceName()
+	}
 	logger := mainLog.With().Str("iface", iface).Logger()
-	var err error
-	netIface, err = netInterface(iface)
+	netIface, err := netInterface(iface)
 	if err != nil {
 		logger.Error().Err(err).Msg("could not get interface")
 		return
 	}
 	logger.Debug().Msg("setting DNS for interface")
-	if err := setDNS(netIface, []string{p.cfg.Listener["0"].IP}); err != nil {
+	if err := setDNS(netIface, []string{cfg.Listener["0"].IP}); err != nil {
 		logger.Error().Err(err).Msgf("could not set DNS for interface")
 		return
 	}
@@ -214,10 +217,18 @@ func (p *prog) setDNS() {
 }
 
 func (p *prog) resetDNS() {
-	if netIface == nil {
+	if iface == "" {
 		return
 	}
+	if iface == "auto" {
+		iface = defaultIfaceName()
+	}
 	logger := mainLog.With().Str("iface", iface).Logger()
+	netIface, err := netInterface(iface)
+	if err != nil {
+		logger.Error().Err(err).Msg("could not get interface")
+		return
+	}
 	logger.Debug().Msg("Restoring DNS for interface")
 	if err := resetDNS(netIface); err != nil {
 		logger.Error().Err(err).Msgf("could not reset DNS")

go.mod

@@ -5,6 +5,7 @@ go 1.19
 require (
 	github.com/go-playground/validator/v10 v10.11.1
 	github.com/hashicorp/golang-lru/v2 v2.0.1
+	github.com/insomniacslk/dhcp v0.0.0-20211209223715-7d93572ebe8e
 	github.com/kardianos/service v1.2.1
 	github.com/lucas-clemente/quic-go v0.29.1
 	github.com/miekg/dns v1.1.50
@@ -14,6 +15,7 @@ require (
 	github.com/spf13/viper v1.14.0
 	github.com/stretchr/testify v1.8.1
 	golang.org/x/sys v0.4.0
+	golang.zx2c4.com/wireguard/windows v0.5.3
 	tailscale.com v1.34.1
 )
 
@@ -35,7 +37,6 @@ require (
 	github.com/hdevalence/ed25519consensus v0.0.0-20220222234857-c00d1f31bab3 // indirect
 	github.com/illarion/gonotify v1.0.1 // indirect
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect
-	github.com/insomniacslk/dhcp v0.0.0-20211209223715-7d93572ebe8e // indirect
 	github.com/josharian/native v1.0.0 // indirect
 	github.com/jsimonetti/rtnetlink v1.1.2-0.20220408201609-d380b505068b // indirect
 	github.com/leodido/go-urn v1.2.1 // indirect
@@ -45,8 +46,10 @@ require (
 	github.com/marten-seemann/qtls-go1-19 v0.1.0 // indirect
 	github.com/mattn/go-colorable v0.1.12 // indirect
 	github.com/mattn/go-isatty v0.0.14 // indirect
+	github.com/mdlayher/ethernet v0.0.0-20190606142754-0394541c37b7 // indirect
 	github.com/mdlayher/genetlink v1.2.0 // indirect
 	github.com/mdlayher/netlink v1.6.0 // indirect
+	github.com/mdlayher/raw v0.0.0-20191009151244-50f2db8cc065 // indirect
 	github.com/mdlayher/socket v0.2.3 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
 	github.com/nxadm/tail v1.4.8 // indirect
@@ -72,7 +75,6 @@ require (
 	golang.org/x/tools v0.1.12 // indirect
 	golang.zx2c4.com/wintun v0.0.0-20211104114900-415007cec224 // indirect
 	golang.zx2c4.com/wireguard v0.0.0-20220920152132-bb719d3a6e2c // indirect
-	golang.zx2c4.com/wireguard/windows v0.5.3 // indirect
 	gopkg.in/ini.v1 v1.67.0 // indirect
 	gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect

go.sum

@@ -164,6 +164,7 @@ github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T
 github.com/hdevalence/ed25519consensus v0.0.0-20220222234857-c00d1f31bab3 h1:aSVUgRRRtOrZOC1fYmY9gV0e9z/Iu+xNVSASWjsuyGU=
 github.com/hdevalence/ed25519consensus v0.0.0-20220222234857-c00d1f31bab3/go.mod h1:5PC6ZNPde8bBqU/ewGZig35+UIZtw9Ytxez8/q5ZyFE=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
+github.com/hugelgupf/socketpair v0.0.0-20190730060125-05d35a94e714 h1:/jC7qQFrv8CrSJVmaolDVOxTfS9kc36uB6H40kdbQq8=
 github.com/hugelgupf/socketpair v0.0.0-20190730060125-05d35a94e714/go.mod h1:2Goc3h8EklBH5mspfHFxBnEoURQCGzQQH1ga9Myjvis=
 github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=
 github.com/ianlancetaylor/demangle v0.0.0-20200824232613-28f6c0f3b639/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=
@@ -212,6 +213,7 @@ github.com/mattn/go-colorable v0.1.12 h1:jF+Du6AlPIjs2BiUiQlKOX0rt3SujHxPnksPKZb
 github.com/mattn/go-colorable v0.1.12/go.mod h1:u5H1YNBxpqRaxsYJYSkiCWKzEfiAb1Gb520KVy5xxl4=
 github.com/mattn/go-isatty v0.0.14 h1:yVuAays6BHfxijgZPzw+3Zlu5yQgKGP2/hcQbHb7S9Y=
 github.com/mattn/go-isatty v0.0.14/go.mod h1:7GGIvUiUoEMVVmxf/4nioHXj79iQHKdU27kJ6hsGG94=
+github.com/mdlayher/ethernet v0.0.0-20190606142754-0394541c37b7 h1:lez6TS6aAau+8wXUP3G9I3TGlmPFEq2CTxBaRqY6AGE=
 github.com/mdlayher/ethernet v0.0.0-20190606142754-0394541c37b7/go.mod h1:U6ZQobyTjI/tJyq2HG+i/dfSoFUt8/aZCM+GKtmFk/Y=
 github.com/mdlayher/genetlink v1.2.0 h1:4yrIkRV5Wfk1WfpWTcoOlGmsWgQj3OtQN9ZsbrE+XtU=
 github.com/mdlayher/genetlink v1.2.0/go.mod h1:ra5LDov2KrUCZJiAtEvXXZBxGMInICMXIwshlJ+qRxQ=
@@ -222,6 +224,7 @@ github.com/mdlayher/netlink v1.1.1/go.mod h1:WTYpFb/WTvlRJAyKhZL5/uy69TDDpHHu2VZ
 github.com/mdlayher/netlink v1.6.0 h1:rOHX5yl7qnlpiVkFWoqccueppMtXzeziFjWAjLg6sz0=
 github.com/mdlayher/netlink v1.6.0/go.mod h1:0o3PlBmGst1xve7wQ7j/hwpNaFaH4qCRyWCdcZk8/vA=
 github.com/mdlayher/raw v0.0.0-20190606142536-fef19f00fc18/go.mod h1:7EpbotpCmVZcu+KCX4g9WaRNuu11uyhiW7+Le1dKawg=
+github.com/mdlayher/raw v0.0.0-20191009151244-50f2db8cc065 h1:aFkJ6lx4FPip+S+Uw4aTegFMct9shDvP+79PsSxpm3w=
 github.com/mdlayher/raw v0.0.0-20191009151244-50f2db8cc065/go.mod h1:7EpbotpCmVZcu+KCX4g9WaRNuu11uyhiW7+Le1dKawg=
 github.com/mdlayher/socket v0.1.1/go.mod h1:mYV5YIZAfHh4dzDVzI8x8tWLWCliuX8Mon5Awbj+qDs=
 github.com/mdlayher/socket v0.2.3 h1:XZA2X2TjdOwNoNPVPclRCURoX/hokBY8nkTmRZFEheM=
@@ -275,6 +278,7 @@ github.com/spf13/viper v1.14.0 h1:Rg7d3Lo706X9tHsJMUjdiwMpHB7W8WnSVOssIY+JElU=
 github.com/spf13/viper v1.14.0/go.mod h1:WT//axPky3FdvXHzGw33dNdXXXfFQqmEalje+egj8As=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0 h1:1zr/of2m5FGMsad5YfcqgdqdWrIhu+EBEJRhR1U7z/c=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=