Linux Ethernet Bridging - Mar 2014 - [Bridge] [PATCH] Notify userspace about bridge learning MAC on new port

Currently, the userspace is informed about the port the MAC is learned on a
bridge and about the bridge removing the MAC from its forwarding table, but not
when the MAC is learned on a different port.
This is inconsistent and makes it difficult for applications to keep track
of all MACs learned by a bridge on a subset of its ports.

Signed-off-by: Michael Braun <michael-dev at fami-braun.de>
Acked-by: Roopa Prabhu <roopa at cumulusnetworks.com>
Cc: <bridge at lists.linux-foundation.org>
Cc: <netdev at vger.kernel.org>
---
 net/bridge/br_fdb.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 9203d5a..25a7772 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -487,6 +487,7 @@ void br_fdb_update(struct net_bridge *br, struct
net_bridge_port *source,
 {
 	struct hlist_head *head = &br->hash[br_mac_hash(addr, vid)];
 	struct net_bridge_fdb_entry *fdb;
+	struct net_bridge_port *origsrc;
 
 	/* some users want to always flood. */
 	if (hold_time(br) == 0)
@@ -507,10 +508,14 @@ void br_fdb_update(struct net_bridge *br, struct
net_bridge_port *source,
 					source->dev->name);
 		} else {
 			/* fastpath: update of existing entry */
+			origsrc = fdb->dst;
 			fdb->dst = source;
 			fdb->updated = jiffies;
 			if (unlikely(added_by_user))
 				fdb->added_by_user = 1;
+			/* notify applications of modified slave device */
+			if (origsrc != source)
+				fdb_notify(br, fdb, RTM_NEWNEIGH);
 		}
 	} else {
 		spin_lock(&br->hash_lock);
-- 
1.8.3.2

From: Michael Braun <michael-dev at fami-braun.de>
Date: Wed, 12 Mar 2014 14:14:56 +0100
> Currently, the userspace is informed about the port the MAC is learned on a
> bridge and about the bridge removing the MAC from its forwarding table, but
not
> when the MAC is learned on a different port.
> This is inconsistent and makes it difficult for applications to keep track
> of all MACs learned by a bridge on a subset of its ports.
> 
> Signed-off-by: Michael Braun <michael-dev at fami-braun.de>
> Acked-by: Roopa Prabhu <roopa at cumulusnetworks.com>
Please use a proper subsystem prefix in your Subject lines, for
example:

"Subject: [PATCH] bridge: Notify userspace about learning MAC on new
port"

Would have been more appropriate here.

Stephen, can you review the substance of this patch please?