Re: [PATCH] act_nat: the checksum of ICMP doesn't have pseudoheader

From: David Miller
Date: Sun Aug 01 2010 - 01:05:14 EST

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date: Fri, 30 Jul 2010 22:30:16 +0800

> On Fri, Jul 30, 2010 at 10:16:05PM +0800, Changli Gao wrote:
>> I know we need to update the ICMP checksum if we alter the payload(the
>> inner IP header here) of ICMP. But I doubt if the update is really
>> necessary if the checksum is partial, as the checksum will be done
>> later(by ether skb_checksum_help() or NIC hardware). In fact, as there
>> isn't any pseudo header, the icmph->checksum should be always ZERO,
>> otherwise skb_checksum_help() or NIC will give the wrong checksums,
>> when the checksum is partial.
> Actually you are right. I suppose the only reason this has never
> shown up is because CHEKSUM_PARTIAL doesn't usually occur with
> forwarded packets.
> Acked-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

Also applied, thanks.

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