If we have 2 VMs with same IP belong to two different network and the
subnet associated with different routers having same external network and
external bgpvpn. In such as case, when traffic initiated using same
internal port some both the VMs, one of the VMs doesn't undergo SNAT
translation and the packet gets continuously looped between ODL and OVS.

When the packet is punted to controller, check is only done if the packet
is already received for an given internal-ip and internal-port. As a
result, VM1 packet is processed properly and SNAT translation happens. But
when VM2 packet arrives, we see with internal-ip and internal-port already
processed and hence we sent back to OVS without SNAT translation which
resulted in looping.