Seems that routers don't do the packet rewriting that I'm observing
here. It's the domain of bandwith management systems. There are
at least four players. I got reactions from several.
Disabling TCP options in the Linux kernel does help, especially when
you're talking to non-Linux systems.
Wietse
Austin Schutz:
> [bugtraq removed from cc:]
>
> I've noticed this problem on my network. I'm behind an Ascend
> pipeline 50. I had thought that this might be the root of the problem.
> Supposedly there's something similar reported as a problem with older
> ascend software.
>
> Any idea what the other people experiencing the prolbem are using
> as gateway routers?
>
> Austin
> On Fri, Mar 24, 2000 at 04:26:13PM -0800, Blu3Viper wrote:
> > How about taking this to linux-kernel for discussion since it appears to be
> > a development kernel bug possibly?
> >
> > -d
> >
> > On Fri, 24 Mar 2000, Wietse Venema wrote:
> >
> > > Date: Fri, 24 Mar 2000 10:38:36 -0500
> > > From: Wietse Venema <wietse@PORCUPINE.ORG>
> > > To: BUGTRAQ@SECURITYFOCUS.COM
> > > Subject: Update: Subtle data corruption of TCP streams
> > >
> > > Apparently, once instance of this data corruption problem is caused
> > > by an unnamed bandwidth management system. It runs as a bridge,
> > > and does not show up in traceroute etc. output. We were able to
> > > estimate its location (at 5 ms round-trip time from one endpoint)
> > > by analyzing packet arrival times.
> > >
> > > Until now, this TCP data corruption problem has been observed only
> > > when one of the connection endpoints runs a recent LINUX version.
> > > Sightings have been reported by sites in Germany and in France.
> > >
> > > Only recent LINUX versions request the use of timestamp options
> > > that cause the tell-tale patterns of "01 01 08 0a" in TCP packets,
> > > and that end up being regurgitated as ^A^A^H^J data.
> > >
> > > I have updated the analysis at ftp://ftp.porcupine.org/pub/debugging/
> > >
> > > Wietse
> > >
> > > Wietse Venema:
> > > > This note is about a subtle data corruption problem with TCP data
> > > > streams that may bite people as more and more (LINUX) systems are
> > > > sending network traffic with TCP-level options turned on.
> > > >
> > > > Last week, several Postfix users reported mail delivery failures
> > > > because sequences of control characters (for example, ^A^A^H) were
> > > > being inserted into their SMTP connections, resulting in SMTP
> > > > protocol errors and non-delivery of email.
> > > >
> > > > These data corruption problems are not host specific: they are
> > > > observed with both Linux and BSD/OS systems, and with mail sent to
> > > > and/or received from systems running Postfix, Sendmail and qmail.
> > > >
> > > > Over the weekend of March 18, 2000, a few people left tcpdump
> > > > running on their machines, in order to record some of these corrupted
> > > > SMTP sessions. This note is based on an analysis of that data.
> > >
> >
> >
> > -
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>
>
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