On Tue, May 01, 2018 at 10:07:35PM -0400, Vladislav Yasevich wrote:
> With SCTP checksum offload available in virtio, it is now
> possible for virtio to receive a sctp packet with CHECKSUM_PARTIAL
> set (guest-to-guest traffic). SCTP doesn't really have a
> partial checksum like TCP does, because CRC32c can't do partial
> additive checksumming. It's all or nothing. So an SCTP packet
> with CHECKSUM_PARTIAL will have checksum set to 0. Let SCTP
> treat this as a valid checksum if CHECKSUM_PARTIAL is set.
>
> Signed-off-by: Vladislav Yasevich <vyase...@redhat.com>
> ---
> net/sctp/input.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/net/sctp/input.c b/net/sctp/input.c
> index ba8a6e6..055b8ffa 100644
> --- a/net/sctp/input.c
> +++ b/net/sctp/input.c
> @@ -80,8 +80,17 @@ static inline int sctp_rcv_checksum(struct net *net,
> struct sk_buff *skb)
> {
> struct sctphdr *sh = sctp_hdr(skb);
> __le32 cmp = sh->checksum;
> - __le32 val = sctp_compute_cksum(skb, 0);
> + __le32 val = 0;
>
> + /* In sctp PARTIAL checksum is always 0. This is a case of
> + * a packet received from guest that supports checksum offload.
> + * Assume it's correct as there is really no way to verify,
> + * and we want to avaoid computing it unnecesarily.
nit, typos --^ --^
> + */
> + if (skb->ip_summed == CHECKSUM_PARTIAL)
> + return 0;
> +
> + val = sctp_compute_cksum(skb, 0);
> if (val != cmp) {
> /* CRC failure, dump it. */
> __SCTP_INC_STATS(net, SCTP_MIB_CHECKSUMERRORS);
> --
> 2.9.5
>
> --
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