Comment 7 for bug 1525028

Reviewed: https://review.opencontrail.org/15850
Committed: http://github.org/Juniper/contrail-vrouter/commit/fdeb3c5bf6ba12f23b1c16eded5eeee24d90a25a
Submitter: Zuul
Branch: R2.21.x

commit fdeb3c5bf6ba12f23b1c16eded5eeee24d90a25a
Author: Divakar <email address hidden>
Date: Wed Dec 16 15:01:05 2015 +0530

Trapping DHCP packets in the ingress processing of Tap interface

Right the DHCP packets are processed in L2 multicast nexthop as DHCP
request packet is a multicast packet. In a scaled setup, this leads to
issues, as Agent receives the config late and VRF correspodning to VMI,
L2 broadcast route and multicast nexthop also does not get added. This
leads to DHCP request packet getting dropped.

As "D" flag is set on VMI by Agent when nova-compute plugs the
interface, the DHCP packet can be trapped to Agent without even the
configuration. Agent in this case can provide the short lease to VM.

So as a fix, the DHCP processing both in V4 and V6 are moved from L2
multicast nexthop to Vm ingress processing.

Change-Id: I2a01aa282b6662ea1ef5832770cc92da931ee833
closes-bug: #1525028