net: bridge: add support for IGMP/MLD stats and export them via netlink

This patch adds stats support for the currently used IGMP/MLD types by the
bridge. The stats are per-port (plus one stat per-bridge) and per-direction
(RX/TX). The stats are exported via netlink via the new linkxstats API
(RTM_GETSTATS). In order to minimize the performance impact, a new option
is used to enable/disable the stats - multicast_stats_enabled, similar to
the recent vlan stats. Also in order to avoid multiple IGMP/MLD type
lookups and checks, we make use of the current "igmp" member of the bridge
private skb->cb region to record the type on Rx (both host-generated and
external packets pass by multicast_rcv()). We can do that since the igmp
member was used as a boolean and all the valid IGMP/MLD types are positive
values. The normal bridge fast-path is not affected at all, the only
affected paths are the flooding ones and since we make use of the IGMP/MLD
type, we can quickly determine if the packet should be counted using
cache-hot data (cb's igmp member). We add counters for:
* IGMP Queries
* IGMP Leaves
* IGMP v1/v2/v3 reports

* MLD Queries
* MLD Leaves
* MLD v1/v2 reports

These are invaluable when monitoring or debugging complex multicast setups
with bridges.

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 2 deletions

diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index 8217aecf025b..f2fede05d32c 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -345,8 +345,8 @@ static int find_portno(struct net_bridge *br)
 static struct net_bridge_port *new_nbp(struct net_bridge *br,
 				       struct net_device *dev)
 {
-	int index;
 	struct net_bridge_port *p;
+	int index, err;
 
 	index = find_portno(br);
 	if (index < 0)
@@ -366,7 +366,12 @@ static struct net_bridge_port *new_nbp(struct net_bridge *br,
 	br_init_port(p);
 	br_set_state(p, BR_STATE_DISABLED);
 	br_stp_port_timer_init(p);
-	br_multicast_add_port(p);
+	err = br_multicast_add_port(p);
+	if (err) {
+		dev_put(dev);
+		kfree(p);
+		p = ERR_PTR(err);
+	}
 
 	return p;
 }