Re: [2.1.99] TCPv4 bad checksum

David S. Miller (
Fri, 1 May 1998 09:35:45 -0700

From: Kevin Fenzi <>
Date: Fri, 1 May 1998 10:16:10 -0600 (MDT)

I know we all (or many of us) have been seeing:

TCPv4 bad checksum from to,len=20/20/40
TCPv4 bad checksum from to,len=35/35/55

Ewe, these are aparently slip/ppp lines at AOL and IBM respectively ;-)

Davem maintains (I am pretty sure correctly) that these are caused
by VJ header compression bugs in various other ppp implementations.

And there are also issues of just plain bad bytes going over the lines
due to FIFO overflows on either side of the serial connection for a
particular packets.

Is there anything we can do to confirm this?

Tell the people at the slip/ppp end to disable VJ compression and see
if it happens anymore ;-)

Anyhow, these messages cause no harm that I can tell but it would
be nice to resolve them before 2.2...If nothing else, we should
remove them if they no longer tell us meaningfull info...

Of course, just like in 2.0.x it will be off or a

We leave them on during the development phase so that if our stack is
in fact generating/checking csums improperly, we'll know right away.

David S. Miller

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