1 files changed, 179 insertions, 0 deletions
diff --git a/cmd/tailscaled/cli/ping.go b/cmd/tailscaled/cli/ping.go
new file mode 100644
index 000000000..25470aa69
--- /dev/null
+++ b/cmd/tailscaled/cli/ping.go
@@ -0,0 +1,179 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cli
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"strings"
+	"time"
+
+	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/client/tailscale"
+	"tailscale.com/ipn"
+	"tailscale.com/ipn/ipnstate"
+)
+
+var pingCmd = &ffcli.Command{
+	Name:       "ping",
+	ShortUsage: "ping <hostname-or-IP>",
+	ShortHelp:  "Ping a host at the Tailscale layer, see how it routed",
+	LongHelp: strings.TrimSpace(`
+
+The 'tailscale ping' command pings a peer node at the Tailscale layer
+and reports which route it took for each response. The first ping or
+so will likely go over DERP (Tailscale's TCP relay protocol) while NAT
+traversal finds a direct path through.
+
+If 'tailscale ping' works but a normal ping does not, that means one
+side's operating system firewall is blocking packets; 'tailscale ping'
+does not inject packets into either side's TUN devices.
+
+By default, 'tailscale ping' stops after 10 pings or once a direct
+(non-DERP) path has been established, whichever comes first.
+
+The provided hostname must resolve to or be a Tailscale IP
+(e.g. 100.x.y.z) or a subnet IP advertised by a Tailscale
+relay node.
+
+`),
+	Exec: runPing,
+	FlagSet: (func() *flag.FlagSet {
+		fs := flag.NewFlagSet("ping", flag.ExitOnError)
+		fs.BoolVar(&pingArgs.verbose, "verbose", false, "verbose output")
+		fs.BoolVar(&pingArgs.untilDirect, "until-direct", true, "stop once a direct path is established")
+		fs.BoolVar(&pingArgs.tsmp, "tsmp", false, "do a TSMP-level ping (through IP + wireguard, but not involving host OS stack)")
+		fs.IntVar(&pingArgs.num, "c", 10, "max number of pings to send")
+		fs.DurationVar(&pingArgs.timeout, "timeout", 5*time.Second, "timeout before giving up on a ping")
+		return fs
+	})(),
+}
+
+var pingArgs struct {
+	num         int
+	untilDirect bool
+	verbose     bool
+	tsmp        bool
+	timeout     time.Duration
+}
+
+func runPing(ctx context.Context, args []string) error {
+	c, bc, ctx, cancel := connect(ctx)
+	defer cancel()
+
+	if len(args) != 1 || args[0] == "" {
+		return errors.New("usage: ping <hostname-or-IP>")
+	}
+	var ip string
+	prc := make(chan *ipnstate.PingResult, 1)
+	bc.SetNotifyCallback(func(n ipn.Notify) {
+		if n.ErrMessage != nil {
+			log.Fatal(*n.ErrMessage)
+		}
+		if pr := n.PingResult; pr != nil && pr.IP == ip {
+			prc <- pr
+		}
+	})
+	pumpErr := make(chan error, 1)
+	go func() { pumpErr <- pump(ctx, bc, c) }()
+
+	hostOrIP := args[0]
+	ip, err := tailscaleIPFromArg(ctx, hostOrIP)
+	if err != nil {
+		return err
+	}
+
+	if pingArgs.verbose && ip != hostOrIP {
+		log.Printf("lookup %q => %q", hostOrIP, ip)
+	}
+
+	n := 0
+	anyPong := false
+	for {
+		n++
+		bc.Ping(ip, pingArgs.tsmp)
+		timer := time.NewTimer(pingArgs.timeout)
+		select {
+		case <-timer.C:
+			fmt.Printf("timeout waiting for ping reply\n")
+		case err := <-pumpErr:
+			return err
+		case pr := <-prc:
+			timer.Stop()
+			if pr.Err != "" {
+				return errors.New(pr.Err)
+			}
+			latency := time.Duration(pr.LatencySeconds * float64(time.Second)).Round(time.Millisecond)
+			via := pr.Endpoint
+			if pr.DERPRegionID != 0 {
+				via = fmt.Sprintf("DERP(%s)", pr.DERPRegionCode)
+			}
+			if pingArgs.tsmp {
+				// TODO(bradfitz): populate the rest of ipnstate.PingResult for TSMP queries?
+				// For now just say it came via TSMP.
+				via = "TSMP"
+			}
+			anyPong = true
+			extra := ""
+			if pr.PeerAPIPort != 0 {
+				extra = fmt.Sprintf(", %d", pr.PeerAPIPort)
+			}
+			fmt.Printf("pong from %s (%s%s) via %v in %v\n", pr.NodeName, pr.NodeIP, extra, via, latency)
+			if pingArgs.tsmp {
+				return nil
+			}
+			if pr.Endpoint != "" && pingArgs.untilDirect {
+				return nil
+			}
+			time.Sleep(time.Second)
+		case <-ctx.Done():
+			return ctx.Err()
+		}
+		if n == pingArgs.num {
+			if !anyPong {
+				return errors.New("no reply")
+			}
+			if pingArgs.untilDirect {
+				return errors.New("direct connection not established")
+			}
+			return nil
+		}
+	}
+}
+
+func tailscaleIPFromArg(ctx context.Context, hostOrIP string) (ip string, err error) {
+	// If the argument is an IP address, use it directly without any resolution.
+	if net.ParseIP(hostOrIP) != nil {
+		return hostOrIP, nil
+	}
+
+	// Otherwise, try to resolve it first from the network peer list.
+	st, err := tailscale.Status(ctx)
+	if err != nil {
+		return "", err
+	}
+	for _, ps := range st.Peer {
+		if hostOrIP == dnsOrQuoteHostname(st, ps) || hostOrIP == ps.DNSName {
+			if len(ps.TailscaleIPs) == 0 {
+				return "", errors.New("node found but lacks an IP")
+			}
+			return ps.TailscaleIPs[0].String(), 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)
+	} else if len(addrs) == 0 {
+		return "", fmt.Errorf("no IPs found for %q", hostOrIP)
+	} else {
+		return addrs[0], nil
+	}
+}