cmd/tailscale: fix "tailscale ip $self-host-hostname"

And in the process, fix the related confusing error messages from
pinging your own IP or hostname.

Fixes #2803

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscale/cli/file.go

@@ -91,7 +91,7 @@ func runCp(ctx context.Context, args []string) error {
 	} else if hadBrackets && (err != nil || !ip.Is6()) {
 		return errors.New("unexpected brackets around target")
 	}
-	ip, err := tailscaleIPFromArg(ctx, target)
+	ip, _, err := tailscaleIPFromArg(ctx, target)
 	if err != nil {
 		return err
 	}

cmd/tailscale/cli/ip.go

@@ -57,7 +57,7 @@ func runIP(ctx context.Context, args []string) error {
 	}
 	ips := st.TailscaleIPs
 	if of != "" {
-		ip, err := tailscaleIPFromArg(ctx, of)
+		ip, _, err := tailscaleIPFromArg(ctx, of)
 		if err != nil {
 			return err
 		}
@@ -101,5 +101,12 @@ func peerMatchingIP(st *ipnstate.Status, ipStr string) (ps *ipnstate.PeerStatus,
 			}
 		}
 	}
+	if ps := st.Self; ps != nil {
+		for _, pip := range ps.TailscaleIPs {
+			if ip == pip {
+				return ps, true
+			}
+		}
+	}
 	return nil, false
 }

cmd/tailscale/cli/ping.go

@@ -84,10 +84,14 @@ func runPing(ctx context.Context, args []string) error {
 	go func() { pumpErr <- pump(ctx, bc, c) }()
 
 	hostOrIP := args[0]
-	ip, err := tailscaleIPFromArg(ctx, hostOrIP)
+	ip, self, err := tailscaleIPFromArg(ctx, hostOrIP)
 	if err != nil {
 		return err
 	}
+	if self {
+		fmt.Printf("%v is local Tailscale IP\n", ip)
+		return nil
+	}
 
 	if pingArgs.verbose && ip != hostOrIP {
 		log.Printf("lookup %q => %q", hostOrIP, ip)
@@ -107,6 +111,10 @@ func runPing(ctx context.Context, args []string) error {
 		case pr := <-prc:
 			timer.Stop()
 			if pr.Err != "" {
+				if pr.IsLocalIP {
+					fmt.Println(pr.Err)
+					return nil
+				}
 				return errors.New(pr.Err)
 			}
 			latency := time.Duration(pr.LatencySeconds * float64(time.Second)).Round(time.Millisecond)
@@ -147,33 +155,39 @@ func runPing(ctx context.Context, args []string) error {
 	}
 }
 
-func tailscaleIPFromArg(ctx context.Context, hostOrIP string) (ip string, err error) {
+func tailscaleIPFromArg(ctx context.Context, hostOrIP string) (ip string, self bool, err error) {
 	// If the argument is an IP address, use it directly without any resolution.
 	if net.ParseIP(hostOrIP) != nil {
-		return hostOrIP, nil
+		return hostOrIP, false, nil
 	}
 
 	// Otherwise, try to resolve it first from the network peer list.
 	st, err := tailscale.Status(ctx)
 	if err != nil {
-		return "", err
+		return "", false, err
+	}
+	match := func(ps *ipnstate.PeerStatus) bool {
+		return strings.EqualFold(hostOrIP, dnsOrQuoteHostname(st, ps)) || hostOrIP == ps.DNSName
 	}
 	for _, ps := range st.Peer {
-		if hostOrIP == dnsOrQuoteHostname(st, ps) || hostOrIP == ps.DNSName {
+		if match(ps) {
 			if len(ps.TailscaleIPs) == 0 {
-				return "", errors.New("node found but lacks an IP")
+				return "", false, errors.New("node found but lacks an IP")
 			}
-			return ps.TailscaleIPs[0].String(), nil
+			return ps.TailscaleIPs[0].String(), false, nil
 		}
 	}
+	if match(st.Self) && len(st.Self.TailscaleIPs) > 0 {
+		return st.Self.TailscaleIPs[0].String(), true, nil
+	}
 
 	// Finally, use DNS.
 	var res net.Resolver
 	if addrs, err := res.LookupHost(ctx, hostOrIP); err != nil {
-		return "", fmt.Errorf("error looking up IP of %q: %v", hostOrIP, err)
+		return "", false, fmt.Errorf("error looking up IP of %q: %v", hostOrIP, err)
 	} else if len(addrs) == 0 {
-		return "", fmt.Errorf("no IPs found for %q", hostOrIP)
+		return "", false, fmt.Errorf("no IPs found for %q", hostOrIP)
 	} else {
-		return addrs[0], nil
+		return addrs[0], false, nil
 	}
 }

ipn/ipnstate/ipnstate.go

@@ -456,6 +456,10 @@ type PingResult struct {
 	// running the server on.
 	PeerAPIPort uint16 `json:",omitempty"`
 
+	// IsLocalIP is whether the ping request error is due to it being
+	// a ping to the local node.
+	IsLocalIP bool `json:",omitempty"`
+
 	// TODO(bradfitz): details like whether port mapping was used on either side? (Once supported)
 }
 

wgengine/pendopen.go

@@ -117,7 +117,7 @@ func (e *userspaceEngine) trackOpenPostFilterOut(pp *packet.Parsed, t *tstun.Wra
 	// like:
 	//    open-conn-track: timeout opening (100.115.73.60:52501 => 17.125.252.5:443); no associated peer node
 	if runtime.GOOS == "ios" && flow.Dst.Port() == 443 && !tsaddr.IsTailscaleIP(flow.Dst.IP()) {
-		if _, err := e.peerForIP(flow.Dst.IP()); err != nil {
+		if _, _, err := e.peerForIP(flow.Dst.IP()); err != nil {
 			return
 		}
 	}
@@ -157,7 +157,7 @@ func (e *userspaceEngine) onOpenTimeout(flow flowtrack.Tuple) {
 	}
 
 	// Diagnose why it might've timed out.
-	n, err := e.peerForIP(flow.Dst.IP())
+	n, _, err := e.peerForIP(flow.Dst.IP())
 	if err != nil {
 		e.logf("open-conn-track: timeout opening %v; peerForIP: %v", flow, err)
 		return

wgengine/userspace.go

@@ -1244,7 +1244,7 @@ func (e *userspaceEngine) UpdateStatus(sb *ipnstate.StatusBuilder) {
 
 func (e *userspaceEngine) Ping(ip netaddr.IP, useTSMP bool, cb func(*ipnstate.PingResult)) {
 	res := &ipnstate.PingResult{IP: ip.String()}
-	peer, err := e.peerForIP(ip)
+	peer, self, err := e.peerForIP(ip)
 	if err != nil {
 		e.logf("ping(%v): %v", ip, err)
 		res.Err = err.Error()
@@ -1257,6 +1257,13 @@ func (e *userspaceEngine) Ping(ip netaddr.IP, useTSMP bool, cb func(*ipnstate.Pi
 		cb(res)
 		return
 	}
+	if self {
+		res.Err = fmt.Sprintf("%v is local Tailscale IP", ip)
+		res.IsLocalIP = true
+		cb(res)
+		return
+	}
+
 	pingType := "disco"
 	if useTSMP {
 		pingType = "TSMP"
@@ -1400,12 +1407,12 @@ func (e *userspaceEngine) WhoIsIPPort(ipport netaddr.IPPort) (tsIP netaddr.IP, o
 //
 // peerForIP acquires both e.mu and e.wgLock, but neither at the same
 // time.
-func (e *userspaceEngine) peerForIP(ip netaddr.IP) (n *tailcfg.Node, err error) {
+func (e *userspaceEngine) peerForIP(ip netaddr.IP) (n *tailcfg.Node, isSelf bool, err error) {
 	e.mu.Lock()
 	nm := e.netMap
 	e.mu.Unlock()
 	if nm == nil {
-		return nil, errors.New("no network map")
+		return nil, false, errors.New("no network map")
 	}
 
 	// Check for exact matches before looking for subnet matches.
@@ -1414,7 +1421,7 @@ func (e *userspaceEngine) peerForIP(ip netaddr.IP) (n *tailcfg.Node, err error)
 	for _, p := range nm.Peers {
 		for _, a := range p.Addresses {
 			if a.IP() == ip && a.IsSingleIP() && tsaddr.IsTailscaleIP(ip) {
-				return p, nil
+				return p, false, nil
 			}
 		}
 		for _, cidr := range p.AllowedIPs {
@@ -1427,6 +1434,11 @@ func (e *userspaceEngine) peerForIP(ip netaddr.IP) (n *tailcfg.Node, err error)
 			}
 		}
 	}
+	for _, a := range nm.Addresses {
+		if a.IP() == ip && a.IsSingleIP() && tsaddr.IsTailscaleIP(ip) {
+			return nm.SelfNode, true, nil
+		}
+	}
 
 	e.wgLock.Lock()
 	defer e.wgLock.Unlock()
@@ -1450,17 +1462,17 @@ func (e *userspaceEngine) peerForIP(ip netaddr.IP) (n *tailcfg.Node, err error)
 	if !bestKey.IsZero() {
 		for _, p := range nm.Peers {
 			if p.Key == bestKey {
-				return p, nil
+				return p, false, nil
 			}
 		}
 	}
 	if bestInNM == nil {
-		return nil, nil
+		return nil, false, nil
 	}
 	if bestInNMPrefix.Bits() == 0 {
-		return nil, errors.New("exit node found but not enabled")
+		return nil, false, errors.New("exit node found but not enabled")
 	}
-	return nil, fmt.Errorf("node %q found, but not using its %v route", bestInNM.ComputedNameWithHost, bestInNMPrefix)
+	return nil, false, fmt.Errorf("node %q found, but not using its %v route", bestInNM.ComputedNameWithHost, bestInNMPrefix)
 }
 
 type closeOnErrorPool []func()