This patch changes ospfd from only listening mode for BFD status updates to interacti...

This patch changes ospfd from only listening mode for BFD status updates to interactive mode of dynamically registering/deregistering neighbors discovered on BFD enabled interfaces with PTM/BFD through zebra. Neighbor is registered with BFD when 2-way adjacency is established and deregistered when adjacency goes down if the BFD is enabled on the interface through which the neighbor was discovered.

OSPF BFD command enhancement to configure BFD parameters (detect multiplier, min rx and min tx).
interface <if-name>
  ip ospf bfd <detect mult> <min rx> <min tx>

This patch also adds BFD support for IPv6 OSPF. ospf6d  will dynamically register/deregister IPv6 neighbors with BFD for monitoring the connectivity of the neighbor. Neighbor is registered with BFD when 2-way adjacency is established and deregistered when adjacency goes down if the BFD is enabled on the interface through which the neighbor was discovered.

OSPF6 BFD command added to configure BFD and parameters (detect multiplier, min rx and min tx).
interface <if-name>
  ipv6 ospf6 bfd <detect mult> <min rx> <min tx>

Signed-off-by: Radhika Mahankali <radhika@cumulusnetworks.com>
Reviewed-by:   Donald Sharp <sharpd@cumulusnetworks.com>
Reviewed-by:   Kanna Rajagopal <kanna@cumulusnetworks.com>