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

Jon Maxwell
2014-05-16T08:54:38Z

----- Original Message -----
> From: "Jon Maxwell" <jmaxwell@redhat.com>
> To: stephen@networkplumber.org
> Cc: davem@davemloft.net, "makita toshiaki" <makita.toshiaki@lab.ntt.co.jp>, vyasevic@redhat.com,
> bridge@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, jpirko@redhat.com
> Sent: Friday, May 16, 2014 6:12:51 PM
> Subject: Re: [PATCH net] bridge: notify user space of fdb port change
>
> Please use this patch. My bad, the previous one
> incorrectly did the notify before fdb->added_by_user = 1.
>

I just realized I did the port compare after fdb->dst = source;
So the notify will never trigger. It's been a long
day, I'll rewrite this tomorrow and resubmit after
testing it on my reproducer. Please ignore this one
too.

> ----- Original Message -----
> > From: "Jon Maxwell" <jmaxwell37@gmail.com>
> > To: stephen@networkplumber.org
> > Cc: davem@davemloft.net, "makita toshiaki" <makita.toshiaki@lab.ntt.co.jp>,
> > vyasevic@redhat.com,
> > bridge@lists.linux-foundation.org, netdev@vger.kernel.org,
> > linux-kernel@vger.kernel.org, jpirko@redhat.com,
> > jmaxwell@redhat.com, "Jon Maxwell" <jmaxwell37@gmail.com>
> > Sent: Friday, May 16, 2014 6:08:39 PM
> > Subject: [PATCH net] bridge: notify user space of fdb port change
> >
> > 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..67480c2 100644
> > --- a/net/bridge/br_fdb.c
> > +++ b/net/bridge/br_fdb.c
> > @@ -511,6 +511,8 @@ void br_fdb_update(struct net_bridge *br, struct
> > net_bridge_port *source,
> > fdb->updated = jiffies;
> > if (unlikely(added_by_user))
> > fdb->added_by_user = 1;
> > + if (unlikely(source->port_no != fdb->dst->port_no))
> > + fdb_notify(br, fdb, RTM_NEWNEIGH);
> > }
> > } else {
> > spin_lock(&br->hash_lock);
> > --
> > 1.8.3.1
> >
> >
>