net: tcp: Close all connections when interface goes down

If the network interface goes down, close all TCP connections
that are bound to that interface. The reasoning here is that we
need a way to remove IP address from the interface and it might
not be possible if there is a TCP socket that is bound to that address.
If the interface comes back on, we might get the same IP address in
which case the socket closure was not really needed but it is not
possible to know in advance.

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

Author: jukkar

subsys/net/ip/net_if.c

@@ -36,6 +36,7 @@ LOG_MODULE_REGISTER(net_if, CONFIG_NET_IF_LOG_LEVEL);
 #include "net_private.h"
 #include "ipv4.h"
 #include "ipv6.h"
+#include "tcp_internal.h"
 
 #include "net_stats.h"
 
@@ -5761,6 +5762,7 @@ static void notify_iface_up(struct net_if *iface)
 
 static void notify_iface_down(struct net_if *iface)
 {
+	net_tcp_close_all_for_iface(iface);
 	net_if_flag_clear(iface, NET_IF_RUNNING);
 	net_mgmt_event_notify(NET_EVENT_IF_DOWN, iface);
 	net_virtual_disable(iface);

subsys/net/ip/tcp.c

@@ -4751,6 +4751,28 @@ struct k_sem *net_tcp_conn_sem_get(struct net_context *context)
 	return &conn->connect_sem;
 }
 
+static void close_tcp_conn(struct tcp *conn, void *user_data)
+{
+	struct net_if *iface = user_data;
+	struct net_context *context = conn->context;
+
+	if (!net_context_is_used(context)) {
+		return;
+	}
+
+	if (net_context_get_iface(context) != iface) {
+		return;
+	}
+
+	/* net_tcp_put() will handle decrementing refcount on stack's behalf */
+	net_tcp_put(context, true);
+}
+
+void net_tcp_close_all_for_iface(struct net_if *iface)
+{
+	net_tcp_foreach(close_tcp_conn, iface);
+}
+
 void net_tcp_init(void)
 {
 	int i;

subsys/net/ip/tcp_internal.h

@@ -494,6 +494,24 @@ static inline void net_tcp_conn_accepted(struct net_context *child_ctx)
 }
 #endif
 
+/**
+ * @brief Close and unref all TCP context bound to an network interface.
+ *
+ * @details This releases all the TCP contexts that are bound to a specific
+ * network interface. It is not possible to send or receive data via those
+ * contexts after this call.
+ *
+ * @param iface The network interface to use to find out the bound contexts.
+ */
+#if defined(CONFIG_NET_NATIVE_TCP)
+void net_tcp_close_all_for_iface(struct net_if *iface);
+#else
+static inline void net_tcp_close_all_for_iface(struct net_if *iface)
+{
+	ARG_UNUSED(iface);
+}
+#endif
+
 #ifdef __cplusplus
 }
 #endif