pimd: VxLAN-AA base APIs

pimd: VxLAN-AA base APIs

1. peerlink-rif as OIF in origination mroutes -
Hosts are multi-homed to the anycast-VTEP pair and can send BUM traffic to
either switch. But the RP would have only joined one MLAG switch for
pulling down the MDT. To make that work we add the peerlink/ISL as
an OIF to origination mroutes (TORC11<=>TORC12 is an anycast VTEP pair) -
root@TORC11:~# ip mr |grep "(36.0.0.9, 239.1.1.100)"
(36.0.0.9, 239.1.1.100)  Iif: peerlink-3.4094 Oifs: peerlink-3.4094 uplink-1
root@TORC11:~#
root@TORC12:~# ip mr |grep "(36.0.0.9, 239.1.1.100)"
(36.0.0.9, 239.1.1.100)  Iif: peerlink-3.4094 Oifs: peerlink-3.4094
root@TORC12:~#

2. VTEP-PIP as register source -
TORC11 and TORC12 share the same anycast VTEP IP (36.0.0.9 in the above
example). And that is the source registered by both VTEPs for all the BUM
mcast-groups. However to allow the pim register start machine to close
the SIP in the register-pkt's IP header must be set to an unique IP address.
This is the VTEP PIP.

Signed-off-by: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>