Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
> > @@ -449,9 +464,6 @@ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
> > if (skb->ip_summed != CHECKSUM_PARTIAL) {
> > *sum = csum_fold(csum_partial(diff, sizeof(diff),
> > ~csum_unfold(*sum)));
> > - if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
> > - skb->csum = ~csum_partial(diff, sizeof(diff),
> > - ~skb->csum);
>
> What is the technical rationale in removing this here but not in any of the
> other inet_proto_csum_replace*() functions? You changelog has zero analysis
> on why here but not elsewhere this change would be needed?
Right, I think it could be dropped everywhere BUT there is a major caveat:
At least for the nf_nat case ipv4 header manipulation (which uses the other
helpers froum utils.c) will eventually also update iph->checksum field
to account for the changed ip addresses.
And that update doesn't touch skb->csum.
So in a way the update of skb->csum in the other helpers indirectly account
for later ip header checksum update.
At least that was my conclusion when reviewing the earlier incarnation
of the patch.
