Avoid ignoring incoming packet by demuxer on endpoint lookup failure

This fixes a race that occurs while the endpoint is being unregistered
and the transport demuxer attempts to match the incoming packet to any
endpoint. The race specifically occurs when the unregistration (and
deletion of the endpoint) occurs, after a successful endpointsByNIC
lookup and before the endpoints map is further looked up with ingress
NICID of the packet.

The fix is to notify the caller of lookup-with-NICID failure, so that
the logic falls through to handling unknown destination packets.
For TCP this can mean replying back with RST.

The syscall test in this CL catches this race as the ACK completing the
handshake could get silently dropped on a listener close, causing no
RST sent to the peer and timing out the poll waiting for POLLHUP.

Fixes #5850

PiperOrigin-RevId: 369023779

1 files changed, 39 insertions, 36 deletions

diff --git a/test/syscalls/linux/socket_inet_loopback.cc b/test/syscalls/linux/socket_inet_loopback.cc
index 38e6f8b5c..9a6b089f6 100644
--- a/test/syscalls/linux/socket_inet_loopback.cc
+++ b/test/syscalls/linux/socket_inet_loopback.cc
@@ -477,47 +477,50 @@ void TestHangupDuringConnect(const TestParam& param,
   TestAddress const& listener = param.listener;
   TestAddress const& connector = param.connector;
 
-  // Create the listening socket.
-  FileDescriptor listen_fd = ASSERT_NO_ERRNO_AND_VALUE(
-      Socket(listener.family(), SOCK_STREAM, IPPROTO_TCP));
-  sockaddr_storage listen_addr = listener.addr;
-  ASSERT_THAT(bind(listen_fd.get(), reinterpret_cast<sockaddr*>(&listen_addr),
-                   listener.addr_len),
-              SyscallSucceeds());
-  ASSERT_THAT(listen(listen_fd.get(), 1), SyscallSucceeds());
+  for (int i = 0; i < 100; i++) {
+    // Create the listening socket.
+    FileDescriptor listen_fd = ASSERT_NO_ERRNO_AND_VALUE(
+        Socket(listener.family(), SOCK_STREAM, IPPROTO_TCP));
+    sockaddr_storage listen_addr = listener.addr;
+    ASSERT_THAT(bind(listen_fd.get(), reinterpret_cast<sockaddr*>(&listen_addr),
+                     listener.addr_len),
+                SyscallSucceeds());
+    ASSERT_THAT(listen(listen_fd.get(), 0), SyscallSucceeds());
 
-  // Get the port bound by the listening socket.
-  socklen_t addrlen = listener.addr_len;
-  ASSERT_THAT(getsockname(listen_fd.get(),
-                          reinterpret_cast<sockaddr*>(&listen_addr), &addrlen),
-              SyscallSucceeds());
-  uint16_t const port =
-      ASSERT_NO_ERRNO_AND_VALUE(AddrPort(listener.family(), listen_addr));
+    // Get the port bound by the listening socket.
+    socklen_t addrlen = listener.addr_len;
+    ASSERT_THAT(
+        getsockname(listen_fd.get(), reinterpret_cast<sockaddr*>(&listen_addr),
+                    &addrlen),
+        SyscallSucceeds());
+    uint16_t const port =
+        ASSERT_NO_ERRNO_AND_VALUE(AddrPort(listener.family(), listen_addr));
 
-  sockaddr_storage conn_addr = connector.addr;
-  ASSERT_NO_ERRNO(SetAddrPort(connector.family(), &conn_addr, port));
+    sockaddr_storage conn_addr = connector.addr;
+    ASSERT_NO_ERRNO(SetAddrPort(connector.family(), &conn_addr, port));
 
-  // Connect asynchronously and immediately hang up the listener.
-  FileDescriptor client = ASSERT_NO_ERRNO_AND_VALUE(
-      Socket(connector.family(), SOCK_STREAM | SOCK_NONBLOCK, IPPROTO_TCP));
-  int ret = connect(client.get(), reinterpret_cast<sockaddr*>(&conn_addr),
-                    connector.addr_len);
-  if (ret != 0) {
-    EXPECT_THAT(ret, SyscallFailsWithErrno(EINPROGRESS));
-  }
+    // Connect asynchronously and immediately hang up the listener.
+    FileDescriptor client = ASSERT_NO_ERRNO_AND_VALUE(
+        Socket(connector.family(), SOCK_STREAM | SOCK_NONBLOCK, IPPROTO_TCP));
+    int ret = connect(client.get(), reinterpret_cast<sockaddr*>(&conn_addr),
+                      connector.addr_len);
+    if (ret != 0) {
+      EXPECT_THAT(ret, SyscallFailsWithErrno(EINPROGRESS));
+    }
 
-  hangup(listen_fd);
+    hangup(listen_fd);
 
-  // Wait for the connection to close.
-  struct pollfd pfd = {
-      .fd = client.get(),
-  };
-  constexpr int kTimeout = 10000;
-  int n = poll(&pfd, 1, kTimeout);
-  ASSERT_GE(n, 0) << strerror(errno);
-  ASSERT_EQ(n, 1);
-  ASSERT_EQ(pfd.revents, POLLHUP | POLLERR);
-  ASSERT_EQ(close(client.release()), 0) << strerror(errno);
+    // Wait for the connection to close.
+    struct pollfd pfd = {
+        .fd = client.get(),
+    };
+    constexpr int kTimeout = 10000;
+    int n = poll(&pfd, 1, kTimeout);
+    ASSERT_GE(n, 0) << strerror(errno);
+    ASSERT_EQ(n, 1);
+    ASSERT_EQ(pfd.revents, POLLHUP | POLLERR);
+    ASSERT_EQ(close(client.release()), 0) << strerror(errno);
+  }
 }
 
 TEST_P(SocketInetLoopbackTest, TCPListenCloseDuringConnect) {