netdev - Re: [PATCH V2 net-next 2/6] sctp: Handle sctp packets with CHECKSUM

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Message-ID: <20180820145415.GA5310@localhost.localdomain>
Date:   Mon, 20 Aug 2018 11:54:15 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Vladislav Yasevich <vyasevich@...il.com>
Cc:     netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org, mst@...hat.com,
        jasowang@...hat.com, nhorman@...driver.com,
        Vladislav Yasevich <vyasevic@...hat.com>
Subject: Re: [PATCH V2 net-next 2/6] sctp: Handle sctp packets with
 CHECKSUM_PARTIAL

On Wed, May 02, 2018 at 11:38:24AM -0300, Marcelo Ricardo Leitner wrote:
> 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 <vyasevic@...hat.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 --^                     --^

Hi Vlad. Seems this patchset got stuck because of these.
The only other subthread that is left is actually about SCTP GSO,
which is not directly related to this.

  Marcelo