[1398] in linux-net channel archive
strange smtp/http hangs
daemon@ATHENA.MIT.EDU (Ron Tapia)
Fri Nov 17 16:50:16 1995
Date: Thu, 16 Nov 1995 12:06:38 -0700 (MST)
From: Ron Tapia <tapia@nmia.com>
To: Linux Servers mailing list <BIG-LINUX@netspace.org>
cc: linux-net <linux-net@vger.rutgers.edu>, sao@nmia.com
In-Reply-To: <199511080636.WAA11966@dandelion.com>
I'm seeing a problem under Linux 1.2.10 & 1.2.9. Both machines that have seen
the problem are 486 DX2/66 machines with 3c509 network cards.
The above kernels have been very stable for quite a while. However, in the
past couple of weeks I've run into `mail problems'. My mail server (running
smail) stops responding, but eventually recovers. The hangs happen whether or
not smail is run from inetd.
On a closer examiniation, the problem seems to be associated with a state
where I have (in netstat output) 5 connections from the same host stuck in
the state `SYN_RECV'. (I don't know why the hangs only seem to happen when
there are 5 connections in that state).
As far as I can tell, there's no real error, just a long wait in the main
loop of the server(s). That is, the timeout happens before the server forks a
process to handle the connection. End users aren't happy with that response,
though...sigh.
When this first occurred, I filtered packets from the offending host in my
router. This got rid of the problem for a week.
Today, however, I saw two hosts causing similar problems for me. One on my
http server and one on my smtp server. The first time this happened, I
attributed the problem to a buggy host on the remote end. The second and
third occurrences make me suspect that there might be something wrong with
the Linux networking code.
Any ideas? Is anyone else seeing this?
Right now, I'm supposing that some new version of networking software out
there is doing something that tickles a bug in the Linux networking code. Any
input would be appreciated.
Thanks for your time,
Ron
--
Hagbard@LambdaMOO % I mean, it's the 90's. You can't just go
Ron@JaysHouseMOO % around trusting every layer you interface
Ron@MediaMOO % with. - tommyd@microsoft.com
<A HREF="http://www.nmia.com/~tapia/">My home page</A>
