Skip listening TCP ports when trying to bind a free port.

PiperOrigin-RevId: 327686558

1 files changed, 29 insertions, 31 deletions

diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 21a4b6e2f..9df22ac84 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -2169,7 +2169,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc
 			if sameAddr && p == e.ID.RemotePort {
 				return false, nil
 			}
-			if _, err := e.stack.ReservePort(netProtos, ProtocolNumber, e.ID.LocalAddress, p, e.portFlags, e.bindToDevice, addr); err != nil {
+			if _, err := e.stack.ReservePort(netProtos, ProtocolNumber, e.ID.LocalAddress, p, e.portFlags, e.bindToDevice, addr, nil /* testPort */); err != nil {
 				if err != tcpip.ErrPortInUse || !reuse {
 					return false, nil
 				}
@@ -2207,7 +2207,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc
 				tcpEP.notifyProtocolGoroutine(notifyAbort)
 				tcpEP.UnlockUser()
 				// Now try and Reserve again if it fails then we skip.
-				if _, err := e.stack.ReservePort(netProtos, ProtocolNumber, e.ID.LocalAddress, p, e.portFlags, e.bindToDevice, addr); err != nil {
+				if _, err := e.stack.ReservePort(netProtos, ProtocolNumber, e.ID.LocalAddress, p, e.portFlags, e.bindToDevice, addr, nil /* testPort */); err != nil {
 					return false, nil
 				}
 			}
@@ -2505,47 +2505,45 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) (err *tcpip.Error) {
 		}
 	}
 
-	port, err := e.stack.ReservePort(netProtos, ProtocolNumber, addr.Addr, addr.Port, e.portFlags, e.bindToDevice, tcpip.FullAddress{})
-	if err != nil {
-		return err
-	}
-
-	e.boundBindToDevice = e.bindToDevice
-	e.boundPortFlags = e.portFlags
-	e.isPortReserved = true
-	e.effectiveNetProtos = netProtos
-	e.ID.LocalPort = port
-
-	// Any failures beyond this point must remove the port registration.
-	defer func(portFlags ports.Flags, bindToDevice tcpip.NICID) {
-		if err != nil {
-			e.stack.ReleasePort(netProtos, ProtocolNumber, addr.Addr, port, portFlags, bindToDevice, tcpip.FullAddress{})
-			e.isPortReserved = false
-			e.effectiveNetProtos = nil
-			e.ID.LocalPort = 0
-			e.ID.LocalAddress = ""
-			e.boundNICID = 0
-			e.boundBindToDevice = 0
-			e.boundPortFlags = ports.Flags{}
-		}
-	}(e.boundPortFlags, e.boundBindToDevice)
-
+	var nic tcpip.NICID
 	// If an address is specified, we must ensure that it's one of our
 	// local addresses.
 	if len(addr.Addr) != 0 {
-		nic := e.stack.CheckLocalAddress(addr.NIC, netProto, addr.Addr)
+		nic = e.stack.CheckLocalAddress(addr.NIC, netProto, addr.Addr)
 		if nic == 0 {
 			return tcpip.ErrBadLocalAddress
 		}
-
-		e.boundNICID = nic
 		e.ID.LocalAddress = addr.Addr
 	}
 
-	if err := e.stack.CheckRegisterTransportEndpoint(e.boundNICID, e.effectiveNetProtos, ProtocolNumber, e.ID, e.boundPortFlags, e.boundBindToDevice); err != nil {
+	port, err := e.stack.ReservePort(netProtos, ProtocolNumber, addr.Addr, addr.Port, e.portFlags, e.bindToDevice, tcpip.FullAddress{}, func(p uint16) bool {
+		id := e.ID
+		id.LocalPort = p
+		// CheckRegisterTransportEndpoint should only return an error if there is a
+		// listening endpoint bound with the same id and portFlags and bindToDevice
+		// options.
+		//
+		// NOTE: Only listening and connected endpoint register with
+		// demuxer. Further connected endpoints always have a remote
+		// address/port. Hence this will only return an error if there is a matching
+		// listening endpoint.
+		if err := e.stack.CheckRegisterTransportEndpoint(nic, netProtos, ProtocolNumber, id, e.portFlags, e.bindToDevice); err != nil {
+			return false
+		}
+		return true
+	})
+	if err != nil {
 		return err
 	}
 
+	e.boundBindToDevice = e.bindToDevice
+	e.boundPortFlags = e.portFlags
+	// TODO(gvisor.dev/issue/3691): Add test to verify boundNICID is correct.
+	e.boundNICID = nic
+	e.isPortReserved = true
+	e.effectiveNetProtos = netProtos
+	e.ID.LocalPort = port
+
 	// Mark endpoint as bound.
 	e.setEndpointState(StateBound)