Comment 28 for bug 1698986

Reviewed: https://review.opencontrail.org/33053
Committed: http://github.com/Juniper/contrail-vrouter/commit/83b005a867a6897576b8d62afd1fae7e5f46be11
Submitter: Zuul (<email address hidden>)
Branch: R4.0

commit 83b005a867a6897576b8d62afd1fae7e5f46be11
Author: Divakar D <email address hidden>
Date: Tue Jun 20 17:22:52 2017 +0530

Fill the NH of the packet in fragment assembler

When fragments are recieved out of order, assembler code caches them
till head fragment is received. While holding the packet, packet's nh is
not cached to avoid taking a reference to NH. Once the head fragment is
received, these out of order fragments are released for flow processing.
While doing this, packet's nh is not filled if the encap is Vxlan packet
as this requires a mac address lookup. For Mpls packets, label is looked
up to extract the NH. Not filling the NH, is resulting in Flow lookup
failure as NH id is also a key for the flow table. Failure to look up
the original flow entry (of head fragment) results in either creating
the new flow entry (with wrong key nh id) in Hold state, or dropping the
packet without flow processing.

To avoid this, bridge look up is done in the given VRF, to extract the
NH.

Change-Id: I03101536e3ac063f16bc4ea31a4b4f5041a5f2f6
closes-bug: #1698986