Re: [PATCH net] bridge: notify user space of fdb port change

Jiri Pirko
2014-05-13T15:16:29Z

Tue, May 13, 2014 at 09:55:08AM CEST, jmaxwell37@gmail.com wrote:
>From: Jon Maxwell <jmaxwell37@gmail.com>
>
>There has been a number incidents recently where customers running KVM have
>reported that VM hosts on different Hypervisors are unreachable. Based on
>pcap traces we found that the bridge was broadcasting the ARP request out
>onto the network. However some NICs have an inbuilt switch which on occasions
>were broadcasting the VMs ARP request back through the physical NIC on the
>Hypervisor. This resulted in the bridge changing ports and incorrectly learning
>that the VMs mac address was external. As a result the ARP reply was directed
>back onto the external network and VM never updated it's ARP cache. This patch
>will notify the bridge command to identify such port toggling.
>
>Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>
>---
> net/bridge/br_fdb.c | 2 ++
> 1 file changed, 2 insertions(+)
>
>diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
>index 9203d5a..37742e2 100644
>--- a/net/bridge/br_fdb.c
>+++ b/net/bridge/br_fdb.c
>@@ -507,6 +507,8 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
> source->dev->name);
> } else {
> /* fastpath: update of existing entry */
>+ if (source->port_no != fdb->dst->port_no)
>+ fdb_notify(br, fdb, RTM_NEWNEIGH);
> fdb->dst = source;
> fdb->updated = jiffies;
> if (unlikely(added_by_user))
>--
>1.8.3.1

Reviewed-by: Jiri Pirko <jiri@resnulli.us>