On Mon, 5 May 2014 07:29:34 +1000
Jon Maxwell <jmaxwel...@gmail.com> wrote:
> 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 flapping 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 detect port flapping and log a message so that this condition
> can be detected earlier.
>
> Signed-off-by: Jon Maxwell <jmaxw...@redhat.com>
> ---
> net/bridge/br_fdb.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> index 9203d5a..c08607b 100644
> --- a/net/bridge/br_fdb.c
> +++ b/net/bridge/br_fdb.c
> @@ -507,6 +507,13 @@ 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 &&
> + net_ratelimit())
> + br_warn(br, "Port flapping detected source
> entry dev = %s mac = %pM, port_no = %d\n existing entry dev = %s mac = %pM,
> port_no = %d\n",
> + source->dev->name,
> + addr, source->port_no,
> + fdb->dst->dev->name, addr,
> + fdb->dst->port_no);
> fdb->dst = source;
> fdb->updated = jiffies;
> if (unlikely(added_by_user))
Ok, but please shorten the message to a single line without excess wordage.
Plus flapping to mean means link going up and down. Maybe use same message
as BSD?
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