* SCTP over GRE (w csum)
@ 2019-12-23 17:45 Lorenzo Bianconi
2019-12-23 17:49 ` Marcelo Ricardo Leitner
0 siblings, 1 reply; 2+ messages in thread
From: Lorenzo Bianconi @ 2019-12-23 17:45 UTC (permalink / raw)
To: netdev; +Cc: dcaratti, lucien.xin, marcelo.leitner
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Hi all,
I am currently working on the following scenario:
sctp --> ipv4 --> gretap --> ipv6 --> eth
If NETIF_F_SCTP_CRC is not supported by the network device (it is the
case for gre), sctp will fallback computing the crc32 in sw with
sctp_gso_make_checksum(), where SKB_GSO_CB(skb)->csum is set to ~0 by
gso_reset_checksum(). After the gso segmentation, gre_gso_segment()
will try to compute gre csum with gso_make_checksum() even if skb->ip_summed
is set to CHECKSUM_NONE (and so using ~0 as partial).
One possible (trivial and not tested) solution would be to recompute the
gre checksum, doing in gre_gso_segment() something like:
if (skb->ip_summed == CHECKSUM_NONE) {
...
err = skb_checksum_help(skb);
if (err < 0)
return return ERR_PTR(err);
} else {
*pcsum = gso_make_checksum(skb, 0);
}
One possible improvement would be offload the GRE checksum computation if the
hw exports this capability in netdev_features and fall back to the sw
implementation if not.
Am I missing something? Is there a better approach?
Regards,
Lorenzo
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: SCTP over GRE (w csum)
2019-12-23 17:45 SCTP over GRE (w csum) Lorenzo Bianconi
@ 2019-12-23 17:49 ` Marcelo Ricardo Leitner
0 siblings, 0 replies; 2+ messages in thread
From: Marcelo Ricardo Leitner @ 2019-12-23 17:49 UTC (permalink / raw)
To: Lorenzo Bianconi; +Cc: netdev, dcaratti, lucien.xin, linux-sctp
[ Just Cc-ing linux-sctp@ ]
On Mon, Dec 23, 2019 at 06:45:35PM +0100, Lorenzo Bianconi wrote:
> Hi all,
>
> I am currently working on the following scenario:
>
> sctp --> ipv4 --> gretap --> ipv6 --> eth
>
> If NETIF_F_SCTP_CRC is not supported by the network device (it is the
> case for gre), sctp will fallback computing the crc32 in sw with
> sctp_gso_make_checksum(), where SKB_GSO_CB(skb)->csum is set to ~0 by
> gso_reset_checksum(). After the gso segmentation, gre_gso_segment()
> will try to compute gre csum with gso_make_checksum() even if skb->ip_summed
> is set to CHECKSUM_NONE (and so using ~0 as partial).
> One possible (trivial and not tested) solution would be to recompute the
> gre checksum, doing in gre_gso_segment() something like:
>
> if (skb->ip_summed == CHECKSUM_NONE) {
> ...
> err = skb_checksum_help(skb);
> if (err < 0)
> return return ERR_PTR(err);
> } else {
> *pcsum = gso_make_checksum(skb, 0);
> }
>
> One possible improvement would be offload the GRE checksum computation if the
> hw exports this capability in netdev_features and fall back to the sw
> implementation if not.
> Am I missing something? Is there a better approach?
>
> Regards,
> Lorenzo
^ permalink raw reply [flat|nested] 2+ messages in thread
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2019-12-23 17:45 SCTP over GRE (w csum) Lorenzo Bianconi
2019-12-23 17:49 ` Marcelo Ricardo Leitner
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