Hello,
On Fri, 25 Oct 2013, Daniel Borkmann wrote:
> + /* Only update csum if we really have to */
> + if (sctph->source != cp->vport || payload_csum) {
> + sctph->source = cp->vport;
> + sctp_nat_csum(skb, sctph, sctphoff);
> + }
The 'if' check for snat_handler should be:
if (sctph->source != cp->vport || payload_csum ||
skb->ip_summed == CHECKSUM_PARTIAL) {
Because we can see CHECKSUM_PARTIAL from virtual devices,
not only from LOCAL_OUT. That is why I removed the '!skb->dev'
check.
The 'else' part should be:
} else {
skb->ip_summed = CHECKSUM_UNNECESSARY;
}
> + /* Only update csum if we really have to */
> + if (sctph->dest != cp->dport || payload_csum) {
> + sctph->dest = cp->dport;
> + sctp_nat_csum(skb, sctph, sctphoff);
> + }
The 'else' part for dnat_handler should be:
} else if (skb->ip_summed != CHECKSUM_PARTIAL) {
skb->ip_summed = CHECKSUM_UNNECESSARY;
}
Because:
- CHECKSUM_COMPLETE: we should not see it for SCTP, in fact
the small set of drivers that support SCTP offloading return
CHECKSUM_UNNECESSARY on correctly received SCTP csum
- CHECKSUM_PARTIAL: we can see it from local stack or
received from virtual drivers. Checks in the 'if' part
will decide whether it is ok to keep CHECKSUM_PARTIAL for
the output
- CHECKSUM_NONE: packet was with unknown checksum. As we
recalculate the sum for IP header in all cases, it should
be safe to use CHECKSUM_UNNECESSARY. We can forward
wrong checksum in this case (without cp->app).
- CHECKSUM_UNNECESSARY: csum was valid on receive
The 'if' part for dnat_handler can be:
if (sctph->dest != cp->dport || payload_csum ||
(skb->ip_summed == CHECKSUM_PARTIAL &&
!(skb_dst(skb)->dev->features & NETIF_F_SCTP_CSUM))) {
I.e. we keep CHECKSUM_PARTIAL only if the new device
supports offloading.
One thing to note: 'lo' does not seem to include
NETIF_F_SCTP_CSUM, so full checksum is calculated.
Regards
--
Julian Anastasov <ja@xxxxxx>
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