Implement BFD authentication (part of RFC 5880). Supports plaintext
passwords and cryptographic MD5 / SHA-1 authentication.
Based on former commit from Pavel Tvrdik
It is possible that sockets_add() are called between sockets_prepare()
and sockets_fire() during poll loop in birdloop_main(), so we need to
use loop->poll_fd.used instead of loop->sock_num to find the last field.
When a BFD session is removed while being scheduled for notification,
the session stays in notify list and is removed twice, which leads to
a strange crash after a while.
I/O:
- BSD: specify src addr on IP sockets by IP_HDRINCL
- BSD: specify src addr on UDP sockets by IP_SENDSRCADDR
- Linux: specify src addr on IP/UDP sockets by IP_PKTINFO
- IPv6: specify src addr on IP/UDP sockets by IPV6_PKTINFO
- Alternative SKF_BIND flag for binding to IP address
- Allows IP/UDP sockets without tx_hook, on these
sockets a packet is discarded when TX queue is full
- Use consistently SOL_ for socket layer values.
OSPF:
- Packet src addr is always explicitly set
- Support for secondary addresses in BSD
- Dynamic RX/TX buffers
- Fixes some minor buffer overruns
- Interface option 'tx length'
- Names for vlink pseudoifaces (vlinkX)
- Vlinks use separate socket for TX
- Vlinks do not use fixed associated iface
- Fixes TTL for direct unicast packets
- Fixes DONTROUTE for OSPF sockets
- Use ifa->ifname instead of ifa->iface->name
