Re: [9fans] multiple pings cause panic

[erik quanstrom <quanstro@quanstro.net>]

On Sun Apr 18 16:41:17 EDT 2010, geoff@plan9.bell-labs.com wrote:
> There are limits on the number of concurrent conversations per
> protocol.  For UDP, it's currently 1024, for TCP it's currently 1024
> on terminals and 4096 on cpu servers.  For ICMP, it's currently 128;
> you may want to raise that.  To find the current limits,
>
> 	grep '>nc = ' /sys/src/9/ip/*.c

it's surprisingly easy to burn through connections since connections
can hang out in Finwait2 for a long time, burning up packets and
connections:

	; cpu -c 'cd /net.alt/tcp; x=1??? echo $x($#x)'
	1175

i haven't had time to take a look at this issue, but i wonder if acks
during Finwait2 are resetting the timer.  this is definately related
to smtp &/| pop.

i sometimes use this script as hostowner to clear out these
connections

	x=`{grep -l Finwait2 */status|sed 's:/status::g'}
	for(i in $x)
		if(~ `{cat $i^/local} *!110 *!25)
			>$i^/ctl echo hangup

- erik