TCPv4 checksum errors

[Geert Uytterhoeven]

On Tue, 22 Dec 1998, David S. Miller wrote:
>    Date: Tue, 22 Dec 1998 10:21:58 +0100 (CET)
>    From: Geert Uytterhoeven <Geert.Uytterhoeven at cs.kuleuven.ac.be>
> 
>    > of a specific packet with a bad checksum generated by Linux/PPC?
> 
>    cassandra kernel: TCPv4 bad checksum from 10.0.24.8:03ff to 10.0.24.4:0201, len=20/20/40
> 
>    (10.0.24.8 is CHRP, 10.0.24.4 is Amiga)
> 
> My suggestion is that since you can reproduce it, you should add code
> next to this printk statement which dumps the entire packet in HEX to
> the console.  Then you can see what and who is at fault and where.
> If the packet is sufficiently small you can walk the checksum
> algorithm by hand and verify it for this test case.

Which one do I have to dump? skb->h.raw or skb->nh.raw? I guess
skb->nh.iph->tot_len bytes at skb->nh.raw?

> In any event this should allow you to say a lot more about this
> situation, I hear about it a lot and if I were a PPC or m68k developer
> I would not let it go for this long, especially if I could reproduce
> it on my own friggin' machine!

:-)

Well, it's not `reproducible on demand'. It happens from time to time.

> BTW, do all of the PPC's which exhibit the behavior use the same
> ethernet controller?

Yes, we all have Tulip boards (I think >95% of the PPC users have Tulip
boards). And the message on linux-kernel about checksum errors on ARM related
to Tulip made me suspicious at well...

If it may help: my Amiga has an Am79C960 (little endian LANCE with byte swapped
data bus).

Greetings,

						Geert

--
Geert Uytterhoeven                     Geert.Uytterhoeven at cs.kuleuven.ac.be
Wavelets, Linux/{m68k~Amiga,PPC~CHRP}  http://www.cs.kuleuven.ac.be/~geert/
Department of Computer Science -- Katholieke Universiteit Leuven -- Belgium


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