[ovs-git] [ovn-org/ovn] e2aa12: ovn-northd: Add ARP responder flows for SNAT entries.

[numansiddique]

  Branch: refs/heads/master
  Home:   https://github.com/ovn-org/ovn
  Commit: e2aa124ff7c24e3128951fce13ca24337121ad27
      https://github.com/ovn-org/ovn/commit/e2aa124ff7c24e3128951fce13ca24337121ad27
  Author: Numan Siddique <numans at ovn.org>
  Date:   2020-08-11 (Tue, 11 Aug 2020)

  Changed paths:
    M northd/ovn-northd.8.xml
    M northd/ovn-northd.c
    M tests/ovn-northd.at
    M tests/system-ovn.at

  Log Message:
  -----------
  ovn-northd: Add ARP responder flows for SNAT entries.

If the below SNAT entry is added:
ovn-nbctl lr-nat-add snat 172.168.0.120 10.0.0.5

And when the logical port with IP - 10.0.0.5, sends a packet destined to
outside, gets SNATted to 172.168.0.120 as expected, but for the reverse traffic
if the upstream switch sends an ARP request for 172.168.0.120, then OVN doesn't
reply and the reply traffic never reaches the logical port.

This patch fixes this issue by addding ARP responder flows for SNAT entries.

Note that, if 172.168.0.120 happens to be the logical router IP, then it works.

Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=1861294
Reported-by: Alexander Constantinescu <aconstan at redhat.com>
Acked-by: Dumitru Ceara <dceara at redhat.com>
Signed-off-by: Numan Siddique <numans at ovn.org>