netdev - Re: [PATCH net-next 3/3] openvswitch: set IPS_CONFIRMED in tmpl status only when commit is set in conntrack

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Message-ID: <CADvbK_fqi=m99e5+5pkHZTuRz7kKWFLZ8CFG3q=mUEtaaKm2hQ@mail.gmail.com>
Date: Mon, 8 Jul 2024 18:03:30 -0400
From: Xin Long <lucien.xin@...il.com>
To: Florian Westphal <fw@...len.de>
Cc: Ilya Maximets <i.maximets@....org>, network dev <netdev@...r.kernel.org>, dev@...nvswitch.org, 
	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>, Jiri Pirko <jiri@...nulli.us>, 
	Davide Caratti <dcaratti@...hat.com>, Jamal Hadi Salim <jhs@...atatu.com>, 
	Eric Dumazet <edumazet@...gle.com>, Cong Wang <xiyou.wangcong@...il.com>, kuba@...nel.org, 
	Paolo Abeni <pabeni@...hat.com>, davem@...emloft.net, 
	Pablo Neira Ayuso <pablo@...filter.org>, Aaron Conole <aconole@...hat.com>
Subject: Re: [PATCH net-next 3/3] openvswitch: set IPS_CONFIRMED in tmpl
 status only when commit is set in conntrack

On Wed, Jun 19, 2024 at 6:10 PM Xin Long <lucien.xin@...il.com> wrote:
>
> On Wed, Jun 19, 2024 at 5:20 PM Florian Westphal <fw@...len.de> wrote:
> >
> > Xin Long <lucien.xin@...il.com> wrote:
> > > Got it, I will fix this in ovs.
> >
> > Thanks!
> >
> > I don't want to throw more work at you, but since you are
> > already working on ovs+conntrack:
> >
> > ovs_ct_init() is bad, as this runs unconditionally.
> >
> > modprobe openvswitch -> conntrack becomes active in all
> > existing and future namespaces.
> >
> > Conntrack is slow, we should avoid this behaviour.
> >
> > ovs_ct_limit_init() should be called only when the feature is
> > configured (the problematic call is nf_conncount_init, as that
> > turns on connection tracking, the kmalloc etc is fine).
> understand.
>
> >
> > Likewise, nf_connlabels_get() should only be called when
> > labels are added/configured, not at the start.
> >
> > I resolved this for tc in 70f06c115bcc but it seems i never
> > got around to fix it for ovs.
Hi, Florian,

I noticed the warning in nf_ct_ext_add() while I'm making this change:

   WARN_ON(nf_ct_is_confirmed(ct));

It can be triggered by these ovs flows from ovs selftests:

  table=0,priority=30,in_port=1,ip,nw_dst=172.1.1.2,actions=ct(commit,nat(dst=10.1.1.2:80),table=1)
  table=1,ip,actions=ct(commit,nat(src=10.1.1.240),exec(set_field:0xac->ct_mark,set_field:0xac->ct_label),table=2)

The 1st flow creates the ct and commits/confirms it, then the 2nd flow is
setting ct_label on a confirmed ct. With this change, the connlabels ext
is not yet allocated at the time, and then the warning is triggered when
allocating it in nf_ct_ext_add().

tc act_ct action doesn't have this issue, as it returns an error if the
connlabels is not found in tcf_ct_act_set_labels(), instead of allocating it.

I can avoid this warning by not allocating ext for commit ct in ovs:

@@ -426,7 +426,7 @@ static int ovs_ct_set_labels(struct nf_conn *ct,
struct sw_flow_key *key,
        struct nf_conn_labels *cl;
        int err;

-       cl = ovs_ct_get_conn_labels(ct);
+       cl = nf_ct_labels_find(ct);
        if (!cl)
                return -ENOSPC;

However, the test case would fail, although the failure can be worked around
by setting ct_label in the 1st rule:

  table=0,priority=30,in_port=1,ip,nw_dst=172.1.1.2,actions=ct(commit,nat(dst=10.1.1.2:80),exec(set_field:0x01->ct_label),table=1)

So I'm worrying our change may break some existing OVS user cases.