#1118 Use IP_RECVDSTADDR sockopt

[Niki Denev]

This patch makes net-snmp use IP_RECVDSTADDR sockopt where available, so if the agent is multihomed it would reply from the IP that the request was sent to.
This is already the case for Linux which uses IP_PKTINFO, but this patch enables the similar behaviour for *BSD hosts.
Without it in environments with asymetric routing and statefull firewalls it's very hard to access some snmp enabled nodes.

[Niki Denev]

Patch for net-snmp-5.5

[Dave Shield]

SVN revision 20183

[Dave Shield]

Thanks for the patch! It has been applied to the 5.5.x and later code branches and the main development tree, and will appear in future releases of the Net-SNMP package.