Fix Accept to not return error for sockets in accept queue.

Accept on gVisor will return an error if a socket in the accept queue was closed
before Accept() was called. Linux will return the new fd even if the returned
socket is already closed by the peer say due to a RST being sent by the peer.

This seems to be intentional in linux more details on the github issue.

Fixes #3780

PiperOrigin-RevId: 329828404

1 files changed, 11 insertions, 2 deletions

diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 3f18efeef..4cf966b65 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -2453,7 +2453,9 @@ func (e *endpoint) startAcceptedLoop() {
 
 // Accept returns a new endpoint if a peer has established a connection
 // to an endpoint previously set to listen mode.
-func (e *endpoint) Accept() (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
+//
+// addr if not-nil will contain the peer address of the returned endpoint.
+func (e *endpoint) Accept(peerAddr *tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
 	e.LockUser()
 	defer e.UnlockUser()
 
@@ -2475,6 +2477,9 @@ func (e *endpoint) Accept() (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
 	default:
 		return nil, nil, tcpip.ErrWouldBlock
 	}
+	if peerAddr != nil {
+		*peerAddr = n.getRemoteAddress()
+	}
 	return n, n.waiterQueue, nil
 }
 
@@ -2577,11 +2582,15 @@ func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
 		return tcpip.FullAddress{}, tcpip.ErrNotConnected
 	}
 
+	return e.getRemoteAddress(), nil
+}
+
+func (e *endpoint) getRemoteAddress() tcpip.FullAddress {
 	return tcpip.FullAddress{
 		Addr: e.ID.RemoteAddress,
 		Port: e.ID.RemotePort,
 		NIC:  e.boundNICID,
-	}, nil
+	}
 }
 
 func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) {