net/portmapper: fix UPnP probing, work against all portsupnpdebug

Prior to Tailscale 1.12 it detected UPnP on any port.
Starting with Tailscale 1.11.x, it stopped detecting UPnP on all ports.

Then start plumbing its discovered Location header port number to the
code that was assuming port 5000.

Fixes #2109

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

1 files changed, 37 insertions, 22 deletions

diff --git a/net/portmapper/portmapper.go b/net/portmapper/portmapper.go
index e9ddf27c9..595ad2e08 100644
--- a/net/portmapper/portmapper.go
+++ b/net/portmapper/portmapper.go
@@ -14,9 +14,11 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"net/http"
 	"sync"
 	"time"
 
+	"go4.org/mem"
 	"inet.af/netaddr"
 	"tailscale.com/net/interfaces"
 	"tailscale.com/net/netns"
@@ -62,8 +64,11 @@ type Client struct {
 	pmpPubIPTime time.Time  // time pmpPubIP last verified
 	pmpLastEpoch uint32
 
-	pcpSawTime  time.Time // time we last saw PCP was available
-	uPnPSawTime time.Time // time we last saw UPnP was available
+	pcpSawTime time.Time // time we last saw PCP was available
+
+	uPnPSawTime    time.Time         // time we last saw UPnP was available
+	uPnPMeta       uPnPDiscoResponse // Location header from UPnP UDP discovery response
+	uPnPHTTPClient *http.Client      // nil until needed
 
 	localPort uint16
 
@@ -560,27 +565,9 @@ func (c *Client) Probe(ctx context.Context) (res ProbeResult, err error) {
 	defer cancel()
 	defer closeCloserOnContextDone(ctx, uc)()
 
-	if c.sawUPnPRecently() {
-		res.UPnP = true
-	} else {
-		hasUPnP := make(chan bool, 1)
-		defer func() {
-			res.UPnP = <-hasUPnP
-		}()
-		go func() {
-			client, err := getUPnPClient(ctx, gw)
-			if err == nil && client != nil {
-				hasUPnP <- true
-				c.mu.Lock()
-				c.uPnPSawTime = time.Now()
-				c.mu.Unlock()
-			}
-			close(hasUPnP)
-		}()
-	}
-
 	pcpAddr := netaddr.IPPortFrom(gw, pcpPort).UDPAddr()
 	pmpAddr := netaddr.IPPortFrom(gw, pmpPort).UDPAddr()
+	upnpAddr := netaddr.IPPortFrom(gw, upnpPort).UDPAddr()
 
 	// Don't send probes to services that we recently learned (for
 	// the same gw/myIP) are available. See
@@ -595,11 +582,16 @@ func (c *Client) Probe(ctx context.Context) (res ProbeResult, err error) {
 	} else {
 		uc.WriteTo(pcpAnnounceRequest(myIP), pcpAddr)
 	}
+	if c.sawUPnPRecently() {
+		res.UPnP = true
+	} else {
+		uc.WriteTo(uPnPPacket, upnpAddr)
+	}
 
 	buf := make([]byte, 1500)
 	pcpHeard := false // true when we get any PCP response
 	for {
-		if pcpHeard && res.PMP {
+		if pcpHeard && res.PMP && res.UPnP {
 			// Nothing more to discover.
 			return res, nil
 		}
@@ -612,6 +604,19 @@ func (c *Client) Probe(ctx context.Context) (res ProbeResult, err error) {
 		}
 		port := addr.(*net.UDPAddr).Port
 		switch port {
+		case upnpPort:
+			if mem.Contains(mem.B(buf[:n]), mem.S(":InternetGatewayDevice:")) {
+				meta, err := parseUPnPDiscoResponse(buf[:n])
+				if err != nil {
+					c.logf("unrecognized UPnP discovery response; ignoring")
+				}
+				// log.Printf("UPnP reply %+v, %q", meta, buf[:n])
+				res.UPnP = true
+				c.mu.Lock()
+				c.uPnPSawTime = time.Now()
+				c.uPnPMeta = meta
+				c.mu.Unlock()
+			}
 		case pcpPort: // same as pmpPort
 			if pres, ok := parsePCPResponse(buf[:n]); ok {
 				if pres.OpCode == pcpOpReply|pcpOpAnnounce {
@@ -724,3 +729,13 @@ func parsePCPResponse(b []byte) (res pcpResponse, ok bool) {
 }
 
 var pmpReqExternalAddrPacket = []byte{0, 0} // version 0, opcode 0 = "Public address request"
+
+const (
+	upnpPort = 1900
+)
+
+var uPnPPacket = []byte("M-SEARCH * HTTP/1.1\r\n" +
+	"HOST: 239.255.255.250:1900\r\n" +
+	"ST: ssdp:all\r\n" +
+	"MAN: \"ssdp:discover\"\r\n" +
+	"MX: 2\r\n\r\n")