2.1.129: "TCPv4 bad checksum" errors with PPP

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Sat, 21 Nov 1998 23:03:13 +0000


Hi,

Since 2.1.127 or thereabouts, I've noticed lots of "TCPv4 bad checksum"
errors in my kernel logs. This is over a PPP connection.

I know that there are supposed to be bugs with some ISPs VJ header
compression, so I disabled it at the Linux end with "novj".
Unfortunately, there are still checksums errors with VJ header
compression disabled. :-(

It's possible that these errors were occurring with some earlier kernels
and I wasn't seeing them. However when they occur, the responsiveness
of the connection is affected noticably, and I didn't notice this with
some older kernels.

These errors come in bursts, lasting a few minutes. Traffic does
continue to get through, but things like FTP downloads tend to stall for
a few tens of seconds while this is happening.

The errors sometimes take a couple of hours to appear, but they do
always appear. My logs for the last week are full of them.

I logged some of the received PPP frames, in case that information is
useful.

Any thoughts?

-- Jamie

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