Fix lingering of TCP socket in the initial state.

When the socket is set with SO_LINGER and close()'d in the initial state, it
should not linger and return immediately.

PiperOrigin-RevId: 334263149

3 files changed, 55 insertions, 1 deletions

diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 87db13720..7ad894840 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -927,7 +927,12 @@ func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 	result := waiter.EventMask(0)
 
 	switch e.EndpointState() {
-	case StateInitial, StateBound, StateConnecting, StateSynSent, StateSynRecv:
+	case StateInitial, StateBound:
+		// This prevents blocking of new sockets which are not
+		// connected when SO_LINGER is set.
+		result |= waiter.EventHUp
+
+	case StateConnecting, StateSynSent, StateSynRecv:
 		// Ready for nothing.
 
 	case StateClose, StateError, StateTimeWait:
@@ -1098,6 +1103,8 @@ func (e *endpoint) closeNoShutdownLocked() {
 		e.notifyProtocolGoroutine(notifyClose)
 	} else {
 		e.transitionToStateCloseLocked()
+		// Notify that the endpoint is closed.
+		e.waiterQueue.Notify(waiter.EventHUp)
 	}
 }
 
diff --git a/test/packetimpact/tests/tcp_linger_test.go b/test/packetimpact/tests/tcp_linger_test.go
index 913e49e06..b9a0409aa 100644
--- a/test/packetimpact/tests/tcp_linger_test.go
+++ b/test/packetimpact/tests/tcp_linger_test.go
@@ -251,3 +251,20 @@ func TestTCPLingerShutdownSendNonZeroTimeout(t *testing.T) {
 		})
 	}
 }
+
+func TestTCPLingerNonEstablished(t *testing.T) {
+	dut := testbench.NewDUT(t)
+	newFD := dut.Socket(t, unix.AF_INET, unix.SOCK_STREAM, unix.IPPROTO_TCP)
+	dut.SetSockLingerOption(t, newFD, lingerDuration, true)
+
+	// As the socket is in the initial state, Close() should not linger
+	// and return immediately.
+	start := time.Now()
+	dut.CloseWithErrno(context.Background(), t, newFD)
+	diff := time.Since(start)
+
+	if diff > lingerDuration {
+		t.Errorf("expected close to return within %s, but returned after %s", lingerDuration, diff)
+	}
+	dut.TearDown()
+}
diff --git a/test/syscalls/linux/tcp_socket.cc b/test/syscalls/linux/tcp_socket.cc
index ab731db1d..e0981e28a 100644
--- a/test/syscalls/linux/tcp_socket.cc
+++ b/test/syscalls/linux/tcp_socket.cc
@@ -1643,6 +1643,36 @@ TEST_P(SimpleTcpSocketTest, GetSocketDetachFilter) {
               SyscallFailsWithErrno(ENOPROTOOPT));
 }
 
+TEST_P(SimpleTcpSocketTest, CloseNonConnectedLingerOption) {
+  FileDescriptor s =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(GetParam(), SOCK_STREAM, IPPROTO_TCP));
+
+  constexpr int kLingerTimeout = 10;  // Seconds.
+
+  // Set the SO_LINGER option.
+  struct linger sl = {
+      .l_onoff = 1,
+      .l_linger = kLingerTimeout,
+  };
+  ASSERT_THAT(setsockopt(s.get(), SOL_SOCKET, SO_LINGER, &sl, sizeof(sl)),
+              SyscallSucceeds());
+
+  struct pollfd poll_fd = {
+      .fd = s.get(),
+      .events = POLLHUP,
+  };
+  constexpr int kPollTimeoutMs = 0;
+  ASSERT_THAT(RetryEINTR(poll)(&poll_fd, 1, kPollTimeoutMs),
+              SyscallSucceedsWithValue(1));
+
+  auto const start_time = absl::Now();
+  EXPECT_THAT(close(s.release()), SyscallSucceeds());
+  auto const end_time = absl::Now();
+
+  // Close() should not linger and return immediately.
+  ASSERT_LT((end_time - start_time), absl::Seconds(kLingerTimeout));
+}
+
 INSTANTIATE_TEST_SUITE_P(AllInetTests, SimpleTcpSocketTest,
                          ::testing::Values(AF_INET, AF_INET6));