bridge: mcast: Avoid arming group timer when (S, G) corresponds to a source

User space will soon be able to install a (*, G) with a source list,
prompting the creation of a (S, G) entry for each source.

In this case, the group timer of the (S, G) entry should never be set.

Solve this by adding a new field to the MDB configuration structure that
denotes whether the (S, G) corresponds to a source or not.

The field will be set in a subsequent patch where br_mdb_add_group_sg()
is called in order to create a (S, G) entry for each user provided
source.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/bridge/br_mdb.c

@@ -814,7 +814,7 @@ static int br_mdb_add_group_sg(const struct br_mdb_config *cfg,
 		return -ENOMEM;
 	}
 	rcu_assign_pointer(*pp, p);
-	if (!(flags & MDB_PG_FLAGS_PERMANENT))
+	if (!(flags & MDB_PG_FLAGS_PERMANENT) && !cfg->src_entry)
 		mod_timer(&p->timer,
 			  now + brmctx->multicast_membership_interval);
 	br_mdb_notify(cfg->br->dev, mp, p, RTM_NEWMDB);

net/bridge/br_private.h

@@ -98,6 +98,7 @@ struct br_mdb_config {
 	struct net_bridge_port		*p;
 	struct br_mdb_entry		*entry;
 	struct br_ip			group;
+	bool				src_entry;
 };
 #endif