minor libalias/natd improvements (first snapshot)

[Clement Laforet]

Hi guys,

I've been working on extending the libalias LSNAT features, and as most
of you surely know, incoming redirections have **REALLY** poor performance, 
due to links management (_FindLinkIn loop eats CPU cycles).
So, I dug into libalias and try my best to make it work better :)

Here's the stuff :
- Add Redirections list + new hash for incoming packets (based on client 
  address).
      This little workaround considerably improves natd incoming
      redirections/forwards speed (specially on heavy loaded servers),
      and uses less CPU time (ex: for _FindLinkIn 47% => 0.9% CPU time
      (according to gprof))
- Add two weighted round robin scheduling types, and prepare for more.
	Ex: A=1,B=2,C=3
	  rr: A,B,C,A,B,C,A,...
	  wrr: A,B,C,B,C,C,A,...
          wsrr: A,B,B,C,C,C,A,... (useless, for testing only)
- now, natd can be reloaded  (killall -HUP natd)
 

"All-in-one" tarball can be found here (natd-libalias.tar.gz): 
(I'll make a patch soon, after cleaning up the code)
http://www.cultdeadsheep.org/sheepkiller/FreeBSD/patch-libalias/

Quick Howto ;-)
#fetch http://www.cultdeadsheep.org/sheepkiller/FreeBSD/patch-libalias/natd-libalias.tar.gz
# tar zxf natd-libalias.tar.gz
# cd natd-libalias
# make
<nice warnings, aren't they ? ;)>
# $EDITOR <your natd config file> 
To play with scheduling:
redirect_port proto <scheduling> IP:port[@weight,IP:port[@weight]] [IP:]port
ex :
redirect_port tcp wrr 192.168.0.1:80 at 2,192.168.0.2:80,192.168.0.3 at 5 10.0.0.1:80
#./natd -f <your natd config file>
# $EDITOR <your natd config file> 
# killall -HUP natd

<scheduling> can be : rr,wrr,wsrr

KNOWN BUGS:
- wrr scheduling take second server for its first redirection.
- Others are hidden ;-)

TODO:
1. Add *RR to RedirectAddress and fix it [done]
2. Add more efficient load sharing/balancing scheduling types
3. Clean some dirty code (famous "FIX ME")
4. Separate natd/libalias
5. Patch ppp
6. Writing docs  8-)
7. a lot of tests
8. and more...

BENCHMARKS:
In progress... Advices are welcome :-)

Feedback, comments, benchmarks, questions, insults, patches are welcome :-)

regards,

clem