mrib: re-evaluate forwarding state of known sources on membership change

src/mrib.c

@@ -173,15 +173,23 @@ static size_t mrib_find(int ifindex)
 	return i;
 }
 
+// Build the forwarding-filter for a (group, source) pair from all users
+static void mrib_filter_build(struct mrib_iface *iface,
+		const struct in6_addr *group, const struct in6_addr *source,
+		mrib_filter *filter)
+{
+	struct mrib_user *user;
+	list_for_each_entry(user, &iface->users, head)
+		if (user->cb_newsource)
+			user->cb_newsource(user, group, source, filter);
+}
+
 // Notify all users of a new multicast source
 static void mrib_notify_newsource(struct mrib_iface *iface,
 		const struct in6_addr *group, const struct in6_addr *source)
 {
 	mrib_filter filter = 0;
-	struct mrib_user *user;
-	list_for_each_entry(user, &iface->users, head)
-		if (user->cb_newsource)
-			user->cb_newsource(user, group, source, &filter);
+	mrib_filter_build(iface, group, source, &filter);
 
 	char groupbuf[INET6_ADDRSTRLEN], sourcebuf[INET6_ADDRSTRLEN];
 	inet_ntop(AF_INET6, group, groupbuf, sizeof(groupbuf));
@@ -203,6 +211,29 @@ static void mrib_notify_newsource(struct mrib_iface *iface,
 	}
 }
 
+// Re-evaluate the forwarding state of all known sources of a group
+// (e.g. after a downstream membership change). Sources are usually
+// detected before the first downstream member subscribes, in which
+// case their multicast route is installed as a placeholder without
+// outgoing interfaces and would only be re-evaluated after the
+// regular lifetime-based cleanup otherwise.
+void mrib_refresh_user(struct mrib_user *user, const struct in6_addr *group)
+{
+	struct mrib_iface *iface = user->iface;
+	if (!iface)
+		return;
+
+	struct mrib_route *c;
+	list_for_each_entry(c, &iface->routes, head) {
+		if (!IN6_ARE_ADDR_EQUAL(&c->group, group))
+			continue;
+
+		mrib_filter filter = 0;
+		mrib_filter_build(iface, &c->group, &c->source, &filter);
+		mrib_set(&c->group, &c->source, iface, filter, 0);
+	}
+}
+
 // Calculate IGMP-checksum
 static uint16_t igmp_checksum(const uint16_t *buf, size_t len)
 {

src/mrib.h

@@ -80,6 +80,9 @@ int mrib_flush(struct mrib_user *user, const struct in6_addr *group, uint8_t gro
 // Add interface to filter
 int mrib_filter_add(mrib_filter *filter, struct mrib_user *user);
 
+// Re-evaluate forwarding state of all known sources of a group
+void mrib_refresh_user(struct mrib_user *user, const struct in6_addr *group);
+
 // Send IGMP-packet
 int mrib_send_igmp(struct mrib_querier *querier, struct igmpv3_query *igmp, size_t len,
 		const struct sockaddr_in *dest);

src/proxy.c

@@ -35,6 +35,7 @@ struct proxy_downlink {
 	struct querier_user_iface iface;
 	struct mrib_user mrib;
 	struct client client;
+	struct proxy *proxy;
 	enum proxy_flags flags;
 };
 
@@ -92,8 +93,13 @@ static void proxy_trigger(struct querier_user_iface *user, const struct in6_addr
 		bool include, const struct in6_addr *sources, size_t len)
 {
 	struct proxy_downlink *iface = container_of(user, struct proxy_downlink, iface);
-	if (proxy_match_scope(iface->flags, group))
+	if (proxy_match_scope(iface->flags, group)) {
 		client_set(&iface->client, group, include, sources, len);
+
+		// Re-evaluate the forwarding state of all known sources of this
+		// group, as source detection may have happened before membership
+		mrib_refresh_user(&iface->proxy->mrib, group);
+	}
 }
 
 // Remove proxy with given name
@@ -181,6 +187,8 @@ int proxy_set(int uplink, const int downlinks[], size_t downlinks_cnt, enum prox
 		if (!downlink)
 			goto err;
 
+		downlink->proxy = proxy;
+
 		if (client_init(&downlink->client, uplink))
 			goto downlink_err3;