[ovs-dev] [PATCH] Handle gratuitous ARP requests and replies in tnl_arp_snoop()

Ben Pfaff blp at ovn.org
Tue Apr 10 23:27:12 UTC 2018

On Thu, Apr 05, 2018 at 12:20:27PM +0000, Manohar Krishnappa Chidambaraswamy wrote:
> Problem:
> ========
> In user-space tunneling implementation, tnl_arp_snoop() snoops only ARP
> *reply* packets to resolve tunnel nexthop IP addresses to MAC addresses.
> Normally the ARP requests are periodically sent by the local host IP stack,
> so that the ARP cache in OVS is refreshed and entries do not time out.
> However, if the remote tunnel nexthop is a VRRP IP, and the gateway
> periodically sends gratuitous ARP *requests* to announce itself,
> tnl_arp_snoop() treats them as INVALID. Consequently, the ARP cache in OVS
> expires after 10 minutes, which results in dropping of the next packet(s)
> until a new ARP request is responded to.
> Fix:
> ====
> Enhance the tunnel neighbor resolution logic in OVS to not only snoop on
> ARP replies but also on gratuitous ARP requests.
> Signed-off-by: Jan Scheurich <jan.scheurich at ericsson.com>
> From: Manohar K C <manohar.krishnappa.chidambaraswamy at ericsson.com>
> CC: Jan Scheurich <jan.scheurich at ericsson.com>

Thanks, applied to master.

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