extmod/modlwip: Fix non-blocking socket ENOTCONN handling.

Move the STATE_LISTENING check to the top of lwip_tcp_receive() to ensure
consistent error handling for both blocking and non-blocking sockets. This
prevents non-blocking sockets from incorrectly returning EAGAIN instead of
ENOTCONN when recv() is called on a listening socket.

Also extend the test to cover both blocking and non-blocking modes with
various listen() arguments to ensure the fix works correctly in all cases.

Signed-off-by: Andrew Leech <[email protected]>

Author: pi-anl

extmod/modlwip.c

@@ -825,6 +825,12 @@ static mp_uint_t lwip_tcp_receive(lwip_socket_obj_t *socket, byte *buf, mp_uint_
     // Check for any pending errors
     STREAM_ERROR_CHECK(socket);
 
+    if (socket->state == STATE_LISTENING) {
+        // original socket in listening state, not the accepted connection.
+        *_errno = MP_ENOTCONN;
+        return -1;
+    }
+
     if (socket->incoming.tcp.pbuf == NULL) {
 
         // Non-blocking socket or flag
@@ -860,12 +866,6 @@ static mp_uint_t lwip_tcp_receive(lwip_socket_obj_t *socket, byte *buf, mp_uint_
         }
     }
 
-    if (socket->state == STATE_LISTENING) {
-        // original socket in listening state, not the accepted connection.
-        *_errno = MP_ENOTCONN;
-        return -1;
-    }
-
     MICROPY_PY_LWIP_ENTER
 
     assert(socket->pcb.tcp != NULL);

tests/multi_net/tcp_accept_recv.py

@@ -13,52 +13,61 @@ def instance0():
     multitest.globals(IP=multitest.get_network_ip())
     multitest.next()
 
-    for i, listen_arg in enumerate(LISTEN_ARGS):
-        s = socket.socket()
-        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
-        s.bind(socket.getaddrinfo("0.0.0.0", PORT)[0][-1])
+    test_num = 0
+    for blocking_mode in [True, False]:
+        for listen_arg in LISTEN_ARGS:
+            test_num += 1
+            s = socket.socket()
+            s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+            s.bind(socket.getaddrinfo("0.0.0.0", PORT)[0][-1])
 
-        # Call listen with or without argument based on test case
-        if listen_arg is None:
-            print(f"Test case {i + 1}/{len(LISTEN_ARGS)}: listen()")
-            s.listen()
-        else:
-            print(f"Test case {i + 1}/{len(LISTEN_ARGS)}: listen({listen_arg})")
-            s.listen(listen_arg)
+            # Call listen with or without argument based on test case
+            if listen_arg is None:
+                print(f"Test case {test_num}/8: listen() blocking={blocking_mode}")
+                s.listen()
+            else:
+                print(f"Test case {test_num}/8: listen({listen_arg}) blocking={blocking_mode}")
+                s.listen(listen_arg)
 
-        # Signal client that server is ready
-        multitest.broadcast(f"server_ready_{i}")
+            # Signal client that server is ready
+            multitest.broadcast(f"server_ready_{test_num}")
 
-        # Wait for client connection
-        c, _ = s.accept()
+            # Wait for client connection
+            c, _ = s.accept()
 
-        try:
-            print("recv", s.recv(10))  # should raise Errno 107 ENOTCONN
-        except OSError as er:
-            # Verify the error code is either 107 (ENOTCONN) or 128 (ENOTCONN on Windows)
-            print(er.errno in (107, 128))
+            # Set blocking mode after accept
+            s.setblocking(blocking_mode)
 
-        # Cleanup
-        c.close()
-        s.close()
+            try:
+                print("recv", s.recv(10))  # should raise Errno 107 ENOTCONN
+            except OSError as er:
+                # Verify the error code is either 107 (ENOTCONN) or 128 (ENOTCONN on Windows)
+                print(er.errno in (107, 128))
 
-        # Signal client we're done with this test case
-        multitest.broadcast(f"server_done_{i}")
+            # Cleanup
+            c.close()
+            s.close()
+
+            # Signal client we're done with this test case
+            multitest.broadcast(f"server_done_{test_num}")
 
 
 # Client
 def instance1():
     multitest.next()
 
-    for i, _ in enumerate(LISTEN_ARGS):
-        # Wait for server to be ready
-        multitest.wait(f"server_ready_{i}")
-
-        # Connect to server
-        s = socket.socket()
-        s.connect(socket.getaddrinfo(IP, PORT)[0][-1])
-        s.send(b"GET / HTTP/1.0\r\n\r\n")
-        s.close()
-
-        # Wait for server to finish this test case
-        multitest.wait(f"server_done_{i}")
+    test_num = 0
+    for blocking_mode in [True, False]:
+        for _ in LISTEN_ARGS:
+            test_num += 1
+            # Wait for server to be ready
+            multitest.wait(f"server_ready_{test_num}")
+
+            # Connect to server
+            s = socket.socket()
+            s.connect(socket.getaddrinfo(IP, PORT)[0][-1])
+            s.send(b"GET / HTTP/1.0\r\n\r\n")
+            s.close()
+
+            # Wait for server to finish this test case
+            multitest.wait(f"server_done_{test_num}")