net: tcp: Fix error reporting on listening socket on iface down

A listening TCP context has no active connection therefore it has no a
second ref from the TCP stack. Thereby, when shutting down connections
when interface goes down, net_tcp_put() should not be called on a
listening socket to release the ref on the TCP stack behalf.

Instead, report the error via the registered accept_cb callback no
notify the application about the error, which should then close the
socket and release the associated TCP context.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>

Author: rlubos

subsys/net/ip/tcp.c

@@ -4765,7 +4765,18 @@ static void close_tcp_conn(struct tcp *conn, void *user_data)
 	}
 
 	/* net_tcp_put() will handle decrementing refcount on stack's behalf */
-	net_tcp_put(context, true);
+	if (net_context_get_state(context) != NET_CONTEXT_LISTENING) {
+		net_tcp_put(context, true);
+	} else {
+		if (context->conn_handler) {
+			net_conn_unregister(context->conn_handler);
+			context->conn_handler = NULL;
+		}
+
+		if (conn->accept_cb != NULL) {
+			conn->accept_cb(conn->context, NULL, 0, -ENETDOWN, context->user_data);
+		}
+	}
 }
 
 void net_tcp_close_all_for_iface(struct net_if *iface)

subsys/net/lib/sockets/sockets_inet.c

@@ -217,8 +217,13 @@ static void zsock_accepted_cb(struct net_context *new_ctx,
 		net_context_ref(new_ctx);
 
 		(void)k_condvar_signal(&parent->cond.recv);
-	}
+	} else if (status < 0) {
+		parent->user_data = INT_TO_POINTER(-status);
+		sock_set_error(parent);
 
+		k_fifo_cancel_wait(&parent->recv_q);
+		(void)k_condvar_signal(&parent->cond.recv);
+	}
 }
 
 static void zsock_received_cb(struct net_context *ctx,