Re: [PATCH net-next 0/3] net: handle the exp removal problem with ovs upcall properly

[Florian Westphal <fw@strlen.de>]

Florian Westphal <fw@strlen.de> wrote:
> Jakub Kicinski <kuba@kernel.org> wrote:
> > On Sun, 16 Jul 2023 17:09:16 -0400 Xin Long wrote:
> > > With the OVS upcall, the original ct in the skb will be dropped, and when
> > > the skb comes back from userspace it has to create a new ct again through
> > > nf_conntrack_in() in either OVS __ovs_ct_lookup() or TC tcf_ct_act().
> > > 
> > > However, the new ct will not be able to have the exp as the original ct
> > > has taken it away from the hash table in nf_ct_find_expectation(). This
> > > will cause some flow never to be matched, like:
> > > 
> > >   'ip,ct_state=-trk,in_port=1 actions=ct(zone=1)'
> > >   'ip,ct_state=+trk+new+rel,in_port=1 actions=ct(commit,zone=1)'
> > >   'ip,ct_state=+trk+new+rel,in_port=1 actions=ct(commit,zone=2),normal'
> > > 
> > > if the 2nd flow triggers the OVS upcall, the 3rd flow will never get
> > > matched.
> > > 
> > > OVS conntrack works around this by adding its own exp lookup function to
> > > not remove the exp from the hash table and saving the exp and its master
> > > info to the flow keys instead of create a real ct. But this way doesn't
> > > work for TC act_ct.
> > > 
> > > The patch 1/3 allows nf_ct_find_expectation() not to remove the exp from
> > > the hash table if tmpl is set with IPS_CONFIRMED when doing lookup. This
> > > allows both OVS conntrack and TC act_ct to have a simple and clear fix
> > > for this problem in the patch 2/3 and 3/3.
> > 
> > Florian, Pablo, any opinion on these?
> 
> Sorry for the silence.  I dislike moving tc/ovs artifacts into
> the conntrack core.

Can't find a better solution, feel free to take this though the net-next tree.

Acked-by: Florian Westphal <fw@strlen.de>