utility to help in using arla behind a NAT

[Matthew Fredette]

Hi.  I have written a utility that can help in using arla on internal
network clients behind a NAT.  Normally, NATs delete mappings for UDP
connections after a timeout; this breaks AFS callbacks.

natkeep monitors the network, watching for connections between AFS
clients and servers, and periodically transmits fake packets matching
those connections.  These fake packets have a junk one-byte UDP
payload, but have a user-specified TTL that is supposed to be just
enough to get the packet through the NAT, without reaching the AFS
servers.

natkeep is available at:

http://mit.edu/fredette/www/natkeep/natkeep-0.1.tar.gz

More documentation is available in the README.  I've been using
natkeep behind a NAT based on FreeBSD's natd.  Callbacks to me get
through, even when my arla has been idle longer than natd's default 60
second UDP timeout.

Some final notes: natkeep requires libpcap (a packet capture library)
and pth (the GNU portable thread library).  

Thanks,

Matt

--
Matt Fredette
fredette at aquery.com, fredette at mit.edu, fredette at theory.lcs.mit.edu
http://mit.edu/fredette/www
"If you understood everything I said, you'd be me."  - Miles Davis