Subject: Re: BUG: warning at net/core/dev.c:1171/skb_checksum_help() 2.6.18-rc3

From: Patrick McHardy <[email-masked]>
Date: Mon, 31 Jul 2006 06:24:31 +0200

David Coulson wrote:
> This machine has four NICs running the e1000 kernel module. Other than
> the BUG() messages, it seems to be running fine. I was running 2.6.15.4
> without any issues on the same hardware, although I noticed the e1000
> has been updated (and I went for rc3 since I was hitting the panic in -rc2)
> 
> Now, I'm not sure if it also has anything to do with this message:
> 
> NAT: no longer support implicit source local NAT
> NAT: packet src 10.1.1.1 -> dst 207.166.203.131

No, this in unrelated. This message tries to tell you that the old
behaviour of changing the source address implicitly to the source
address routing would use for a DNATed connection is no longer done.
This behaviour changed in 2.6.11, so if everything worked in 2.6.15,
you should be fine.

> Any suggestions as to how to go about debugging this?
> 
> BUG: warning at net/core/dev.c:1171/skb_checksum_help()
>  [<c02e0412>] skb_checksum_help+0x4d/0xf0
>  [<c034e4d3>] ip_nat_fn+0x4e/0x19e

This is a known problem with NAT and HW checksum and will probably get
fixed in 2.6.19. The message is just a warning, everything should work
fine.