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Date: Fri, 09 Jan 2004 15:01:45 +0100
From: Andre Oppermann <andre@freebsd.org>
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Subject: Re: cvs commit: src/sys/netinet ip_icmp.c tcp.h tcp_input.c 
 tcp_subr.ctcp_usrreq.c tcp_var.h
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David Xu wrote:
> 
> I got following messages when I am running mysql stress test suite,
> and the test can not be completed.
> 
> "too many small tcp packets from 128.0.0.1:20672, av. 91byte/packet,
> dropping connection"

You can set net.inet.tcp.minmssoverload to a higher value than the
default of 1,000.  I suggest trying with 2,000 as next step and see
if it still overloads.

Appearently my default of 1,000 pps is fine for normal use but too
low for some edge cases.

Could you check the MySQL source code if it has a setsockopt() setting
the TCP_NODELAY option?  That would help to explain a lot.

-- 
Andre


> David Xu
> 
> Andre Oppermann wrote:
> > andre       2004/01/08 09:40:07 PST
> >
> >   FreeBSD src repository
> >
> >   Modified files:
> >     sys/netinet          ip_icmp.c tcp.h tcp_input.c tcp_subr.c
> >                          tcp_usrreq.c tcp_var.h
> >   Log:
> >   Limiters and sanity checks for TCP MSS (maximum segement size)
> >   resource exhaustion attacks.
> >
> >   For network link optimization TCP can adjust its MSS and thus
> >   packet size according to the observed path MTU.  This is done
> >   dynamically based on feedback from the remote host and network
> >   components along the packet path.  This information can be
> >   abused to pretend an extremely low path MTU.