bridge: Add multicast_querier toggle and disable queries by default

Sending general queries was implemented as an optimisation to speed
up convergence on start-up.  In order to prevent interference with
multicast routers a zero source address has to be used.

Unfortunately these packets appear to cause some multicast-aware
switches to misbehave, e.g., by disrupting multicast packets to us.

Since the multicast snooping feature still functions without sending
our own queries, this patch will change the default to not send
queries.

For those that need queries in order to speed up convergence on start-up,
a toggle is provided to restore the previous behaviour.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 0 deletions

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index b3647d090e1f..708e84f31888 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -783,6 +783,7 @@ static void br_multicast_send_query(struct net_bridge *br,
         struct br_ip br_group;
 
         if (!netif_running(br->dev) || br->multicast_disabled ||
+            !br->multicast_querier ||
             timer_pending(&br->multicast_querier_timer))
                 return;
 
@@ -1565,6 +1566,7 @@ void br_multicast_init(struct net_bridge *br)
         br->hash_max = 512;
 
         br->multicast_router = 1;
+        br->multicast_querier = 0;
         br->multicast_last_member_count = 2;
         br->multicast_startup_query_count = 2;
 
@@ -1760,6 +1762,24 @@ unlock:
         return err;
 }
 
+int br_multicast_set_querier(struct net_bridge *br, unsigned long val)
+{
+        val = !!val;
+
+        spin_lock_bh(&br->multicast_lock);
+        if (br->multicast_querier == val)
+                goto unlock;
+
+        br->multicast_querier = val;
+        if (val)
+                br_multicast_start_querier(br);
+
+unlock:
+        spin_unlock_bh(&br->multicast_lock);
+
+        return 0;
+}
+
 int br_multicast_set_hash_max(struct net_bridge *br, unsigned long val)
 {
         int err = -ENOENT;