[squid-users] File corruption with reverse proxy

From: Andy Osborne <andy_at_oznet.demon.co.uk>
Date: Tue, 28 Aug 2012 14:21:44 +0100

Hi All,

I'm trying to debug a problem at the moment where a small
proportion of people visiting our sites (Squid 3.1.20 as a reverse
proxy with Apache origin servers) are seeing file corruption.

So far all the confirmed cases are using Windows 7 with
IE 9 or a recent Chrome. Unfortunately we can't reproduce
the problem on any machine we have, which is making it
difficult to debug.

The corruption doesn't always occur but when it does it looks
like a few contiguous bytes getting one or two bits flipped.

I managed to get access to a PC belonging to a client to do
some testing. This machine has the problem and runs Win 7
Pro (64 bit). Unplugging it from the network and using
it's ethernet cable to test using a variety of laptops (Mac,
Win 7, Win XP) showed no problems. That would normally
be enough to put the whole thing down to some weird
Windows bug and give up.

However, overriding DNS via the hosts file to point this
problematic machine directly at an origin server made
the problem disappear. I still think it's probably a Windows
bug, but it seems that something about the reverse proxy
(Squid or the machine running it) is triggering the bug.

Test downloads from various locations hasn't found any
difference between files downloaded directly or via the
reverse proxy. Basically, all my testing shows no problems.

Has anyone else seen a similar problem recently ?. One
reason to support it being a Windows bug is that it only
started occurring about 3 weeks ago and we haven't changed
anything in our hosting set up in that time frame.

It would also be a help if anyone can point me at some sites
that are known to be using Squid as a reverse proxy. Seeing
if they also exhibit the problem might help to narrow things


Received on Tue Aug 28 2012 - 13:21:47 MDT

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