net: if: Release the interface lock early when starting IPv6 DAD

In order to avoid any mutex deadlocks between iface->lock and
TX lock, release the interface lock before calling a function
that will acquire TX lock. See previous commit for similar issue
in RS timer handling.

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

Author: jukkar

include/zephyr/net/net_if.h

@@ -95,6 +95,9 @@ struct net_if_addr {
 			/** Duplicate address detection (DAD) timer */
 			sys_snode_t dad_node;
 
+			/** DAD needed list node */
+			sys_snode_t dad_need_node;
+
 			/** DAD start time */
 			uint32_t dad_start;
 

subsys/net/ip/net_if.c

@@ -1324,8 +1324,9 @@ void net_if_ipv6_start_dad(struct net_if *iface,
 
 void net_if_start_dad(struct net_if *iface)
 {
-	struct net_if_addr *ifaddr;
+	struct net_if_addr *ifaddr, *next;
 	struct net_if_ipv6 *ipv6;
+	sys_slist_t dad_needed;
 	struct in6_addr addr = { };
 	int ret;
 
@@ -1357,6 +1358,8 @@ void net_if_start_dad(struct net_if *iface)
 	/* Start DAD for all the addresses that were added earlier when
 	 * the interface was down.
 	 */
+	sys_slist_init(&dad_needed);
+
 	ARRAY_FOR_EACH(ipv6->unicast, i) {
 		if (!ipv6->unicast[i].is_used ||
 		    ipv6->unicast[i].address.family != AF_INET6 ||
@@ -1366,9 +1369,21 @@ void net_if_start_dad(struct net_if *iface)
 			continue;
 		}
 
-		net_if_ipv6_start_dad(iface, &ipv6->unicast[i]);
+		sys_slist_prepend(&dad_needed, &ipv6->unicast[i].dad_need_node);
 	}
 
+	net_if_unlock(iface);
+
+	/* Start DAD for all the addresses without holding the iface lock
+	 * to avoid any possible mutex deadlock issues.
+	 */
+	SYS_SLIST_FOR_EACH_CONTAINER_SAFE(&dad_needed,
+					  ifaddr, next, dad_need_node) {
+		net_if_ipv6_start_dad(iface, ifaddr);
+	}
+
+	return;
+
 out:
 	net_if_unlock(iface);
 }
@@ -1415,7 +1430,10 @@ void net_if_ipv6_dad_failed(struct net_if *iface, const struct in6_addr *addr)
 	net_if_ipv6_addr_rm(iface, addr);
 
 	if (IS_ENABLED(CONFIG_NET_IPV6_PE) && iface->pe_enabled) {
+		net_if_unlock(iface);
+
 		net_ipv6_pe_start(iface, addr, timeout, preferred_lifetime);
+		return;
 	}
 
 out:
@@ -1944,6 +1962,7 @@ struct net_if_addr *net_if_ipv6_addr_add(struct net_if *iface,
 {
 	struct net_if_addr *ifaddr = NULL;
 	struct net_if_ipv6 *ipv6;
+	bool do_dad = false;
 
 	net_if_lock(iface);
 
@@ -1995,8 +2014,7 @@ struct net_if_addr *net_if_ipv6_addr_add(struct net_if *iface,
 			 */
 			join_mcast_nodes(iface,
 					 &ipv6->unicast[i].address.in6_addr);
-
-			net_if_ipv6_start_dad(iface, &ipv6->unicast[i]);
+			do_dad = true;
 		} else {
 			/* If DAD is not done for point-to-point links, then
 			 * the address is usable immediately.
@@ -2010,9 +2028,17 @@ struct net_if_addr *net_if_ipv6_addr_add(struct net_if *iface,
 			sizeof(struct in6_addr));
 
 		ifaddr = &ipv6->unicast[i];
-		goto out;
+		break;
 	}
 
+	net_if_unlock(iface);
+
+	if (ifaddr != NULL && do_dad) {
+		net_if_ipv6_start_dad(iface, ifaddr);
+	}
+
+	return ifaddr;
+
 out:
 	net_if_unlock(iface);