net: tcp: Allow immediate connection tear down

If the network interface goes down, then we do not have any time
to tear down TCP connection gracefully because there is no more
a connection to send data to. In this case the TCP connection is
forcefully closed without going into FIN_WAIT_1 state.

Signed-off-by: Jukka Rissanen <[email protected]>

Author: jukkar

subsys/net/ip/net_context.c

@@ -650,7 +650,7 @@ int net_context_get(sa_family_t family, enum net_sock_type type, uint16_t proto,
 		    !net_if_is_ip_offloaded(net_if_get_default()) &&
 		    proto == IPPROTO_TCP) {
 			/* Free the TCP context that we allocated earlier */
-			net_tcp_put(&contexts[i]);
+			net_tcp_put(&contexts[i], false);
 		}
 
 		return ret;
@@ -735,7 +735,7 @@ int net_context_put(struct net_context *context)
 	context->send_cb = NULL;
 
 	/* net_tcp_put() will handle decrementing refcount on stack's behalf */
-	net_tcp_put(context);
+	net_tcp_put(context, false);
 
 	/* Decrement refcount on user app's behalf */
 	net_context_unref(context);

subsys/net/ip/tcp.c

@@ -3137,7 +3137,7 @@ static enum net_verdict tcp_in(struct tcp *conn, struct net_pkt *pkt)
 				 * the TCP context and put the connection into
 				 * active close (TCP_FIN_WAIT_1).
 				 */
-				net_tcp_put(conn->context);
+				net_tcp_put(conn->context, false);
 				break;
 			}
 
@@ -3690,7 +3690,7 @@ static enum net_verdict tcp_in(struct tcp *conn, struct net_pkt *pkt)
 }
 
 /* Active connection close: send FIN and go to FIN_WAIT_1 state */
-int net_tcp_put(struct net_context *context)
+int net_tcp_put(struct net_context *context, bool force_close)
 {
 	struct tcp *conn = context->tcp;
 
@@ -3713,26 +3713,43 @@ int net_tcp_put(struct net_context *context)
 				conn->send_data_total);
 			conn->in_close = true;
 
-			/* How long to wait until all the data has been sent?
-			 */
-			k_work_reschedule_for_queue(&tcp_work_q,
-						    &conn->send_data_timer,
-						    K_MSEC(TCP_RTO_MS));
+			if (force_close) {
+				k_work_cancel_delayable(&conn->send_data_timer);
+
+				keep_alive_timer_stop(conn);
+				tcp_conn_close(conn, -ENETRESET);
+			} else {
+				/* How long to wait until all the data has been sent?
+				 */
+				k_work_reschedule_for_queue(&tcp_work_q,
+							    &conn->send_data_timer,
+							    K_MSEC(TCP_RTO_MS));
+			}
+
 		} else {
-			NET_DBG("[%p] TCP connection in %s close, "
-				"not disposing yet (waiting %dms)",
-				conn, "active", tcp_max_timeout_ms);
-			k_work_reschedule_for_queue(&tcp_work_q,
-						    &conn->fin_timer,
-						    FIN_TIMEOUT);
+			if (force_close) {
+				NET_DBG("[%p] TCP connection in %s close, "
+					"disposing immediately",
+					conn, "forced");
 
-			tcp_out(conn, FIN | ACK);
-			conn_seq(conn, + 1);
-			tcp_setup_retransmission(conn);
+				keep_alive_timer_stop(conn);
+				tcp_conn_close(conn, -ENETRESET);
+			} else {
+				NET_DBG("[%p] TCP connection in %s close, "
+					"not disposing yet (waiting %dms)",
+					conn, "active", tcp_max_timeout_ms);
+				k_work_reschedule_for_queue(&tcp_work_q,
+							    &conn->fin_timer,
+							    FIN_TIMEOUT);
+
+				tcp_out(conn, FIN | ACK);
+				conn_seq(conn, + 1);
+				tcp_setup_retransmission(conn);
 
-			conn_state(conn, TCP_FIN_WAIT_1);
+				conn_state(conn, TCP_FIN_WAIT_1);
 
-			keep_alive_timer_stop(conn);
+				keep_alive_timer_stop(conn);
+			}
 		}
 	} else if (conn->in_connect) {
 		conn->in_connect = false;
@@ -4411,7 +4428,7 @@ enum net_verdict tp_input(struct net_conn *net_conn,
 		if (is("CLOSE2", tp->op)) {
 			struct tcp *conn =
 				(void *)sys_slist_peek_head(&tcp_conns);
-			net_tcp_put(conn->context);
+			net_tcp_put(conn->context, false);
 		}
 		if (is("RECV", tp->op)) {
 #define HEXSTR_SIZE 64

subsys/net/ip/tcp_internal.h

@@ -354,15 +354,19 @@ static inline int net_tcp_update_recv_wnd(struct net_context *context,
  * @brief Close and delete the TCP connection for the net_context
  *
  * @param context Network context
+ * @param force_close If true, close the connection immediately. This is
+ * used e.g., when network interface goes down and we cannot wait for proper
+ * connection close procedure as we cannot send any packets anymore.
  *
  * @return 0 on success, < 0 on error
  */
 #if defined(CONFIG_NET_NATIVE_TCP)
-int net_tcp_put(struct net_context *context);
+int net_tcp_put(struct net_context *context, bool force_close);
 #else
-static inline int net_tcp_put(struct net_context *context)
+static inline int net_tcp_put(struct net_context *context, bool force_close)
 {
 	ARG_UNUSED(context);
+	ARG_UNUSED(force_close);
 
 	return -EPROTONOSUPPORT;
 }