Return error while calling shutdown on a bound unconnected UDP socket.

PiperOrigin-RevId: 542057418

pkg/tcpip/transport/udp/endpoint.go

@@ -745,6 +745,9 @@ func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
 		}
 	}
 
+	if e.net.State() == transport.DatagramEndpointStateBound {
+		return &tcpip.ErrNotConnected{}
+	}
 	return nil
 }
 

test/syscalls/linux/socket_inet_loopback.cc

@@ -1572,7 +1572,8 @@ TEST_P(SocketInetReusePortTest, UdpPortReuseMultiThread) {
 
           // Shutdown all sockets to wake up other threads.
           for (int j = 0; j < kThreadCount; j++)
-            shutdown(listener_fds[j].get(), SHUT_RD);
+            EXPECT_THAT(shutdown(listener_fds[j].get(), SHUT_RD),
+                        SyscallFailsWithErrno(ENOTCONN));
         });
   }
 

test/syscalls/linux/udp_socket.cc

@@ -2432,6 +2432,21 @@ TEST_P(UdpSocketTest, SendPacketLargerThanSendBufOnNonBlockingSocket) {
             SyscallFailsWithErrno(EAGAIN)));
 }
 
+TEST_P(UdpSocketTest, ReadShutdownOnBoundSocket) {
+  ASSERT_NO_ERRNO(BindLoopback());
+
+  // Bind `sock_` to loopback.
+  struct sockaddr_storage addr_storage = InetLoopbackAddr();
+  struct sockaddr* addr = AsSockAddr(&addr_storage);
+  ASSERT_NO_ERRNO(BindSocket(sock_.get(), addr));
+
+  int shut_opts[] = {SHUT_RD, SHUT_WR, SHUT_RDWR};
+  for (int shut_opt : shut_opts) {
+    EXPECT_THAT(shutdown(sock_.get(), shut_opt),
+                SyscallFailsWithErrno(ENOTCONN));
+  }
+}
+
 INSTANTIATE_TEST_SUITE_P(AllInetTests, UdpSocketControlMessagesTest,
                          ::testing::Values(AddressFamily::kIpv4,
                                            AddressFamily::kIpv6,