net/{packet,tstun}: send peerapi port in TSMP pongs

For discovery when an explicit hostname/IP is known. We'll still
also send it via control for finding peers by a list.

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

cmd/tailscale/cli/ping.go

@@ -143,7 +143,11 @@ func runPing(ctx context.Context, args []string) error {
 				via = "TSMP"
 			}
 			anyPong = true
-			fmt.Printf("pong from %s (%s) via %v in %v\n", pr.NodeName, pr.NodeIP, via, latency)
+			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
 			}

cmd/tailscaled/tailscaled.go

@@ -229,7 +229,10 @@ func run() error {
 
 	var ns *netstack.Impl
 	if useNetstack {
-		tunDev, magicConn := e.(wgengine.InternalsGetter).GetInternals()
+		tunDev, magicConn, ok := e.(wgengine.InternalsGetter).GetInternals()
+		if !ok {
+			log.Fatalf("%T is not a wgengine.InternalsGetter", e)
+		}
 		ns, err = netstack.Create(logf, tunDev, e, magicConn)
 		if err != nil {
 			log.Fatalf("netstack.Create: %v", err)