Re: [squid-users] 2.4STABLE1 hangs for a few minutes on Linux 2.2.18

From: Alain Fauconnet <>
Date: Thu, 22 Nov 2001 16:22:24 +0700

Thanks for the reply!

On Thu, Nov 22, 2001 at 10:12:47AM +0100, Henrik Nordstrom wrote:
> On Thursday 22 November 2001 08.59, Alain Fauconnet wrote:
> > ... it would "stop listening" to  its  port  (3128)  for  a
> > length of time ranging from 1 to 15 minutes. It means that a telnet to
> > this port does  *NOT*  get  connection  refused,  but  the  connection
> > doesn't  establish  either. It stops to "Trying...". Tcpdump shows the
> > SYN packet coming, then nothing else.
> Smells like your connection backlog queue is filled by some junk which does
> not get out of there..
> Try increasing the SYN backlog queue.
> echo NNN >/proc/sys/net/ipv4/tcp_max_syn_backlog

This one I've set to 128 already as written in my first posting.

> It could also help enabling the SYN flood defender mechanisms such as
> syncookies in the kernel..
> echo 1 >/proc/sys/net/ipv4/tcp_syncookies

This one is not set yet.

> A reliable way to diagnose if the SYN backlog is the problem is to not make
> the above changes and instead set up a second http_port. If Squid still
> accepts new connections on this second port when there is problems with the
> first then your problem is with 100% certainty the SYN backlog queue, and the
> above mechanisms (prefereably in combination) will solve your problem.

The SYN backlog queue is then a per-port resource, right ? (sorry if
that's a stupid question).

I'll try this and summarize.

Thanks again,
Received on Thu Nov 22 2001 - 02:22:32 MST

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