Return to BSD News archive
Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!news.mira.net.au!news.netspace.net.au!news.mel.connect.com.au!munnari.OZ.AU!news.ecn.uoknor.edu!news.wildstar.net!newsfeed.direct.ca!op.net!news.mathworks.com!newsfeed.internetmci.com!demos!news1.best.com!nntp1.best.com!usenet
From: dillon@flea.best.net (Matt Dillon)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Max TCP connections
Date: 16 Dec 1996 19:22:28 GMT
Organization: BEST Internet Communications, Inc.
Lines: 48
Message-ID: <5947hk$eto@nntp1.best.com>
References: <593r4g$orq@Mercury.mcs.net> <59475c$el0@nntp1.best.com>
NNTP-Posting-Host: flea.best.net
Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:32692
:In article <59475c$el0@nntp1.best.com>,
:Matt Dillon <dillon@flea.best.net> wrote:
:>:In article <593r4g$orq@Mercury.mcs.net>,
:>:Tim Daneliuk <tundra@tundraware.com> wrote:
:>:>Is there a kernel or other configuration which determines the maximum
:>:>number of TCP/IP connections allowed in a running FreeBSD image or is
:>:>this dynamically allocated out of the memory pool? I am occasionally
:>:>seeing a problem with remote sites unable to establish SMTP
:>:>connections with my machine, even though it is up and running fine. I
:>:>wonder if I am starved for TCP/IP connections.
:>:>--
:>:>------------------------------------------------------------------------------
:>:>Tim Daneliuk / tundra@tundraware.com
:>:>Voicemail/FAX 847.827.1706
:>
:> There is an mbuf parameter for network clusters somewhere, but I doubt
:> that is your problem.
:>
:> Try this when you are having problems:
:>
:> netstat -tn | fgrep SYN_R
:>
:> It could be that your sendmail is not setting the listen queue
:> large enough. Nominally this is only 5 or 10, but in internet-connected
:> sites remote machines often try to connect to you over broken networks
:> which can fill up the listen queue with sockets in a SNY_RCVD state,
:> causing other unrelated connection attempts to fail.
:>
:> If you are running a recent sendmail (8.7 or 8.8 I think), you
:> can increase the liste queue size with the DaemonPortOptions option...
:>
:> DaemonPortOptions=Listen=255,Port=esmtp
:>
:> Your kernel must also be compiled with a large SOMAXCONN ... I'm not
:> sure what the default is.
:>
:> -Matt
Oh, wait, you may just want:
DaemonPortOptions=Listen=255
I'm not sure what Port=esmtp is supposed to do. If the netstat
-tn piped to a grep of SYN_R shows a lot of port 25 connections stuck
in SYN_RCVD, then the listen queue size is definitely your problem.
-Matt