ipfw: Too many dynamic rules

[Jeremy Chadwick]

On Tue, Sep 14, 2010 at 01:12:00PM +0200, Gareth de Vaux wrote:
> On Tue 2010-09-14 (04:03), Jeremy Chadwick wrote:
> > You're absolutely certain these are all in FIN_WAIT_2 state and not
> > TIME_WAIT?
> 
> Yup,
> 
> $ netstat -an | grep FIN_WAIT_1 | wc -l
>       57
> $ netstat -an | grep FIN_WAIT_2 | wc -l
>      431
> $ netstat -an | grep TIME_WAIT | wc -l
>       17

Regarding net.inet.tcp.finwait2_timeout=15000 -- you don't see any
improvement at all?  That's a bit strange.  There's probably something
about ipfw I'm not getting.  Adding luigi@ to the CC list, since I think
he's familiar with ipfw internals.

FWIW, I'd recommend keeping an appended log of output from something
like this script:

while true
do
  echo "`date` -- `netstat -n | grep -c FIN_WAIT_2`" >> /some/log
  sleep 5
done

Just make sure the sleep interval is lower than the FIN timeout.

Another thing to try: setting net.inet.tcp.fast_finwait2_recycle=1 and
see if this makes a difference.  I'm not familiar with this setting
myself, but some Google results indicate some people do use it.  The
sysctl description is a bit vague too.

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |