Add BFD protocol option 'strict bind' to use separate listening socket
for each BFD interface bound to its address instead of using shared
listening sockets.
There is a simple universal IO loop, taking care of events, timers and
sockets. Primarily, one instance of a protocol should use exactly one IO
loop to do all its work, as is now done in BFD.
Contrary to previous versions, the loop is now launched and cleaned by
the nest/proto.c code, allowing for a protocol to just request its own
loop by setting the loop's lock order in config higher than the_bird.
It is not supported nor checked if any protocol changed the requested
lock order in reconfigure. No protocol should do it at all.
Direct BFD sessions needs to be dispatched not only by IP addresses, but
also by interfaces, in order to avoid collisions between neighbors with
the same IPv6 link-local addresses.
Extend BFD session hash_ip key by interface index to handle that. Use 0
for multihop sessions.
Thanks to Sebastian Hahn for the original patch.
BFD session options are configured per interface in BFD protocol. This
patch allows to specify them also per-request in protocols requesting
sessions (currently limited to BGP).
Implement BFD authentication (part of RFC 5880). Supports plaintext
passwords and cryptographic MD5 / SHA-1 authentication.
Based on former commit from Pavel Tvrdik
