Re: [PATCH v3 0/2] netfilter: nfqueue: incorrect sctp checksum

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Mon, May 20, 2024 at 08:33:39PM +0200, Pablo Neira Ayuso wrote:
> On Mon, May 20, 2024 at 05:44:35PM +0200, Pablo Neira Ayuso wrote:
> > On Mon, May 20, 2024 at 01:27:22PM +0200, Pablo Neira Ayuso wrote:
> > > On Mon, May 13, 2024 at 10:00:31PM +0000, Antonio Ojea wrote:
> > > > Fixes the bug described in
> > > > https://bugzilla.netfilter.org/show_bug.cgi?id=1742
> > > > causing netfilter to drop SCTP packets when using
> > > > nfqueue and GSO due to incorrect checksum.
> > > > 
> > > > Patch 1 adds a new helper to process the sctp checksum
> > > > correctly.
> > > > 
> > > > Patch 2 adds a selftest regression test.
> > > 
> > > I am inclined to integrated this into nf.git, I will pick a Fixes: tag
> > > sufficiently old so -stable picks up.
> > 
> > I have to collapse this chunk, otherwise I hit one issue with missing
> > exported symbol. No need to resend, I will amend here. Just for the
> > record.
> 
> Hm. SCTP GSO support is different too, because it keeps a list of segments.
> 
> static int
> nfqnl_enqueue_packet(struct nf_queue_entry *entry, unsigned int queuenum)
> {
> [...]
>         if ((queue->flags & NFQA_CFG_F_GSO) || !skb_is_gso(skb))
>                 return __nfqnl_enqueue_packet(net, queue, entry);
> 
> I think this needs to be:
> 
>         if ((queue->flags & NFQA_CFG_F_GSO) || !skb_is_gso(skb) || !skb_is_gso_sctp(skb))

This is not correct either:

        if (queue->flags & NFQA_CFG_F_GSO) is true, this also needs !skb_is_gso_sctp(skb)

I can see the current selftest disables the NFQA_CFG_F_GSO flag (-G
option in nf_queue test program), I suspect that's why this is working.

>                 return __nfqnl_enqueue_packet(net, queue, entry);
> 
> so SCTP GSO packets enters this path below:
> 
>         nf_bridge_adjust_skb_data(skb);
>         segs = skb_gso_segment(skb, 0);
> 
> to deliver separated segments to userspace.
> 
> Otherwise, I don't see yet how userspace can deal with several SCTP
> segments, from nf_reinject() there is a list of segments no more.