net: iface: Prevent iface/TCP mutexes deadlock

In rare occasions iface and TCP mutexes could cause a deadlock. As
notifying the interface readiness takes place just before the iface
mutex is released, it should be not harm to release it just before the
TCP is notified about interface going down to avoid the deadlock.

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

Author: rlubos

subsys/net/ip/net_if.c

@@ -5762,7 +5762,6 @@ 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);
@@ -5774,6 +5773,12 @@ static void notify_iface_down(struct net_if *iface)
 		clear_joined_ipv4_mcast_groups(iface);
 		net_ipv4_autoconf_reset(iface);
 	}
+
+	if (IS_ENABLED(CONFIG_NET_NATIVE_TCP)) {
+		net_if_unlock(iface);
+		net_tcp_close_all_for_iface(iface);
+		net_if_lock(iface);
+	}
 }
 
 const char *net_if_oper_state2str(enum net_if_oper_state state)