net: ipv4: Added mechanism to add 224.0.0.1 address to a multicast filter

The purpose of the change was to have the Zephyr network stack
internally add the IGMP all systems 224.0.0.1 multicast address to a
multicast membership list so that multicast hash filter implementations
can add this address to the hash filter.

Fixes #53548

Signed-off-by: Chamira Perera <chamira.perera@audinate.com>

subsys/net/ip/Kconfig.ipv4

@@ -34,6 +34,7 @@ config NET_IF_UNICAST_IPV4_ADDR_COUNT
 
 config NET_IF_MCAST_IPV4_ADDR_COUNT
 	int "Max number of multicast IPv4 addresses per network interface"
+	default 2 if NET_IPV4_IGMP
 	default 1
 
 config NET_ICMPV4_ACCEPT_BROADCAST

subsys/net/ip/igmp.c

@@ -127,7 +127,15 @@ static int send_igmp_report(struct net_if *iface,
 	}
 
 	for (i = 0; i < NET_IF_MAX_IPV4_MADDR; i++) {
-		if (!ipv4->mcast[i].is_used || !ipv4->mcast[i].is_joined) {
+		/* We don't need to send an IGMP membership report to the IGMP
+		 * all systems multicast address of 224.0.0.1 so skip over it.
+		 * Since the IGMP all systems multicast address is marked as
+		 * used and joined during init time, we have to check this
+		 * address separately to skip over it.
+		 */
+		if (!ipv4->mcast[i].is_used || !ipv4->mcast[i].is_joined ||
+			net_ipv4_addr_cmp_raw((uint8_t *)&ipv4->mcast[i].address.in_addr,
+					(uint8_t *)&all_systems)) {
 			continue;
 		}
 
@@ -139,7 +147,15 @@ static int send_igmp_report(struct net_if *iface,
 	}
 
 	for (i = 0; i < NET_IF_MAX_IPV4_MADDR; i++) {
-		if (!ipv4->mcast[i].is_used || !ipv4->mcast[i].is_joined) {
+		/* We don't need to send an IGMP membership report to the IGMP
+		 * all systems multicast address of 224.0.0.1 so skip over it.
+		 * Since the IGMP all systems multicast address is marked as
+		 * used and joined during init time, we have to check this
+		 * address separately to skip over it.
+		 */
+		if (!ipv4->mcast[i].is_used || !ipv4->mcast[i].is_joined ||
+			net_ipv4_addr_cmp_raw((uint8_t *)&ipv4->mcast[i].address.in_addr,
+					(uint8_t *)&all_systems)) {
 			continue;
 		}
 
@@ -326,3 +342,39 @@ int net_ipv4_igmp_leave(struct net_if *iface, const struct in_addr *addr)
 					sizeof(struct in_addr));
 	return ret;
 }
+
+void net_ipv4_igmp_init(struct net_if *iface)
+{
+	struct net_if_mcast_addr *maddr;
+
+	/* Ensure multicast addresses are available */
+	if (CONFIG_NET_IF_MCAST_IPV4_ADDR_COUNT < 1) {
+		return;
+	}
+
+	/* This code adds the IGMP all systems 224.0.0.1 multicast address
+	 * to the list of multicast addresses of the given interface.
+	 * The address is marked as joined. However, an IGMP membership
+	 * report is not generated for this address. Populating this
+	 * address in the list of multicast addresses of the interface
+	 * and marking it as joined is helpful for multicast hash filter
+	 * implementations that need a list of multicast addresses it needs
+	 * to add to the multicast hash filter after a multicast address
+	 * has been removed from the membership list.
+	 */
+	maddr = net_if_ipv4_maddr_lookup(&all_systems, &iface);
+	if (maddr && net_if_ipv4_maddr_is_joined(maddr)) {
+		return;
+	}
+
+	if (!maddr) {
+		maddr = net_if_ipv4_maddr_add(iface, &all_systems);
+		if (!maddr) {
+			return;
+		}
+	}
+
+	net_if_ipv4_maddr_join(maddr);
+
+	net_if_mcast_monitor(iface, &maddr->address, true);
+}

subsys/net/ip/net_if.c

@@ -4159,6 +4159,21 @@ exit:
 	}
 }
 
+static void init_igmp(struct net_if *iface)
+{
+#if defined(CONFIG_NET_IPV4_IGMP)
+	/* Ensure IPv4 is enabled for this interface */
+	if (iface->config.ip.ipv4 == NULL) {
+		return;
+	}
+
+	net_ipv4_igmp_init(iface);
+#else
+	ARG_UNUSED(iface);
+	return;
+#endif
+}
+
 int net_if_up(struct net_if *iface)
 {
 	int status = 0;
@@ -4187,6 +4202,8 @@ int net_if_up(struct net_if *iface)
 		goto out;
 	}
 
+	init_igmp(iface);
+
 done:
 	net_if_flag_set(iface, NET_IF_UP);
 	net_mgmt_event_notify(NET_EVENT_IF_ADMIN_UP, iface);

subsys/net/ip/net_private.h

@@ -173,6 +173,15 @@ enum net_verdict net_context_packet_received(struct net_conn *conn,
 extern uint16_t net_calc_chksum_ipv4(struct net_pkt *pkt);
 #endif /* CONFIG_NET_IPV4 */
 
+#if defined(CONFIG_NET_IPV4_IGMP)
+/**
+ * @brief Initialise the IGMP module for a given interface
+ *
+ * @param iface		Interface to init IGMP
+ */
+void net_ipv4_igmp_init(struct net_if *iface);
+#endif /* CONFIG_NET_IPV4_IGMP */
+
 #if defined(CONFIG_NET_IPV4_IGMP)
 uint16_t net_calc_chksum_igmp(uint8_t *data, size_t len);
 enum net_verdict net_ipv4_igmp_input(struct net_pkt *pkt,