4 files changed, 97 insertions(+), 31 deletions(-)

M ipn/ipnlocal/local.go
M ipn/ipnlocal/local_test.go
M ipn/ipnlocal/serve_test.go
M wgengine/netstack/netstack.go

@@ 3329,13 3329,24 @@ var (
 // TCPHandlerForDst returns a TCP handler for connections to dst, or nil if
 // no handler is needed. It also returns a list of TCP socket options to
 // apply to the socket before calling the handler.
+// TCPHandlerForDst is called both for connections to our node's local IP
+// as well as to the service IP (quad 100).
 func (b *LocalBackend) TCPHandlerForDst(src, dst netip.AddrPort) (handler func(c net.Conn) error, opts []tcpip.SettableSocketOption) {
-	if dst.Port() == 80 && (dst.Addr() == magicDNSIP || dst.Addr() == magicDNSIPv6) {
-		if b.ShouldRunWebClient() {
-			return b.handleWebClientConn, opts
+	// First handle internal connections to the service IP
+	hittingServiceIP := dst.Addr() == magicDNSIP || dst.Addr() == magicDNSIPv6
+	if hittingServiceIP {
+		switch dst.Port() {
+		case 80:
+			if b.ShouldRunWebClient() {
+				return b.handleWebClientConn, opts
+			}
+			return b.HandleQuad100Port80Conn, opts
+		case TailFSLocalPort:
+			return b.handleTailFSConn, opts
 		}
-		return b.HandleQuad100Port80Conn, opts
 	}
+
+	// Then handle external connections to the local IP.
 	if !b.isLocalIP(dst.Addr()) {
 		return nil, nil
 	}


@@ 3353,18 3364,6 @@ func (b *LocalBackend) TCPHandlerForDst(src, dst netip.AddrPort) (handler func(c
 	if dst.Port() == webClientPort && b.ShouldRunWebClient() {
 		return b.handleWebClientConn, opts
 	}
-	if dst.Port() == TailFSLocalPort {
-		fs, ok := b.sys.TailFSForLocal.GetOK()
-		if ok {
-			return func(conn net.Conn) error {
-				if !b.TailFSAccessEnabled() {
-					conn.Close()
-					return nil
-				}
-				return fs.HandleConn(conn, conn.RemoteAddr())
-			}, opts
-		}
-	}
 	if port, ok := b.GetPeerAPIPort(dst.Addr()); ok && dst.Port() == port {
 		return func(c net.Conn) error {
 			b.handlePeerAPIConn(src, dst, c)


@@ 3377,6 3376,15 @@ func (b *LocalBackend) TCPHandlerForDst(src, dst netip.AddrPort) (handler func(c
 	return nil, nil
 }
 
+func (b *LocalBackend) handleTailFSConn(conn net.Conn) error {
+	fs, ok := b.sys.TailFSForLocal.GetOK()
+	if !ok || !b.TailFSAccessEnabled() {
+		conn.Close()
+		return nil
+	}
+	return fs.HandleConn(conn, conn.RemoteAddr())
+}
+
 func (b *LocalBackend) peerAPIServicesLocked() (ret []tailcfg.Service) {
 	for _, pln := range b.peerAPIListeners {
 		proto := tailcfg.PeerAPI4

@@ 2173,3 2173,72 @@ func TestOnTailnetDefaultAutoUpdate(t *testing.T) {
 		})
 	}
 }
+
+func TestTCPHandlerForDst(t *testing.T) {
+	b := newTestBackend(t)
+
+	tests := []struct {
+		desc      string
+		dst       string
+		intercept bool
+	}{
+		{
+			desc:      "intercept port 80 (Web UI) on quad100 IPv4",
+			dst:       "100.100.100.100:80",
+			intercept: true,
+		},
+		{
+			desc:      "intercept port 80 (Web UI) on quad100 IPv6",
+			dst:       "[fd7a:115c:a1e0::53]:80",
+			intercept: true,
+		},
+		{
+			desc:      "don't intercept port 80 on local ip",
+			dst:       "100.100.103.100:80",
+			intercept: false,
+		},
+		{
+			desc:      "intercept port 8080 (TailFS) on quad100 IPv4",
+			dst:       "100.100.100.100:8080",
+			intercept: true,
+		},
+		{
+			desc:      "intercept port 8080 (TailFS) on quad100 IPv6",
+			dst:       "[fd7a:115c:a1e0::53]:8080",
+			intercept: true,
+		},
+		{
+			desc:      "don't intercept port 8080 on local ip",
+			dst:       "100.100.103.100:8080",
+			intercept: false,
+		},
+		{
+			desc:      "don't intercept port 9080 on quad100 IPv4",
+			dst:       "100.100.100.100:9080",
+			intercept: false,
+		},
+		{
+			desc:      "don't intercept port 9080 on quad100 IPv6",
+			dst:       "[fd7a:115c:a1e0::53]:9080",
+			intercept: false,
+		},
+		{
+			desc:      "don't intercept port 9080 on local ip",
+			dst:       "100.100.103.100:9080",
+			intercept: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.dst, func(t *testing.T) {
+			t.Log(tt.desc)
+			src := netip.MustParseAddrPort("100.100.102.100:51234")
+			h, _ := b.TCPHandlerForDst(src, netip.MustParseAddrPort(tt.dst))
+			if !tt.intercept && h != nil {
+				t.Error("intercepted traffic we shouldn't have")
+			} else if tt.intercept && h == nil {
+				t.Error("failed to intercept traffic we should have")
+			}
+		})
+	}
+}

@@ 684,7 684,8 @@ func newTestBackend(t *testing.T) *LocalBackend {
 
 	b.netMap = &netmap.NetworkMap{
 		SelfNode: (&tailcfg.Node{
-			Name: "example.ts.net",
+			Name:         "example.ts.net",
+			Capabilities: []tailcfg.NodeCapability{tailcfg.NodeAttrsTailFSAccess},
 		}).View(),
 		UserProfiles: map[tailcfg.UserID]tailcfg.UserProfile{
 			tailcfg.UserID(1): {

@@ 1131,25 1131,13 @@ func (ns *Impl) acceptTCP(r *tcp.ForwarderRequest) {
 	// Local Services (DNS and WebDAV)
 	hittingServiceIP := dialIP == serviceIP || dialIP == serviceIPv6
 	hittingDNS := hittingServiceIP && reqDetails.LocalPort == 53
-	hittingTailFS := hittingServiceIP && ns.tailFSForLocal != nil && reqDetails.LocalPort == ipnlocal.TailFSLocalPort
-	if hittingDNS || hittingTailFS {
+	if hittingDNS {
 		c := getConnOrReset()
 		if c == nil {
 			return
 		}
 		addrPort := netip.AddrPortFrom(clientRemoteIP, reqDetails.RemotePort)
-		if hittingDNS {
-			go ns.dns.HandleTCPConn(c, addrPort)
-		} else if hittingTailFS {
-			if !ns.lb.TailFSAccessEnabled() {
-				c.Close()
-				return
-			}
-			err := ns.tailFSForLocal.HandleConn(c, net.TCPAddrFromAddrPort(addrPort))
-			if err != nil {
-				ns.logf("netstack: tailfs.HandleConn: %v", err)
-			}
-		}
+		go ns.dns.HandleTCPConn(c, addrPort)
 		return
 	}