netdev - Re: [PATCH net] net: sched: cls: Fix offloading when ingress dev is vxlan

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Date:   Wed, 6 Jun 2018 08:50:33 -0700
From:   Jakub Kicinski <kubakici@...pl>
To:     Or Gerlitz <gerlitz.or@...il.com>
Cc:     Paul Blakey <paulb@...lanox.com>, Jiri Pirko <jiri@...lanox.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        David Miller <davem@...emloft.net>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Yevgeny Kliteynik <kliteyn@...lanox.com>,
        Roi Dayan <roid@...lanox.com>,
        Shahar Klein <shahark@...lanox.com>,
        Mark Bloch <markb@...lanox.com>,
        Or Gerlitz <ogerlitz@...lanox.com>
Subject: Re: [PATCH net] net: sched: cls: Fix offloading when ingress dev is
 vxlan

On Wed, 6 Jun 2018 08:12:20 +0300, Or Gerlitz wrote:
> On Tue, Jun 5, 2018 at 9:59 PM, Jakub Kicinski <kubakici@...pl> wrote:
> > On Tue, 5 Jun 2018 11:57:47 -0700, Jakub Kicinski wrote:  
> >> On Tue,  5 Jun 2018 11:04:03 +0300, Paul Blakey wrote:  
> >> > When using a vxlan device as the ingress dev, we count it as a
> >> > "no offload dev", so when such a rule comes and err stop is true,
> >> > we fail early and don't try the egdev route which can offload it
> >> > through the egress device.
> >> >
> >> > Fix that by not calling the block offload if one of the devices
> >> > attached to it is not offload capable, but make sure egress on such case
> >> > is capable instead.
> >> >
> >> > Fixes: caa7260156eb ("net: sched: keep track of offloaded filters [..]")
> >> > Reviewed-by: Roi Dayan <roid@...lanox.com>
> >> > Acked-by: Jiri Pirko <jiri@...lanox.com>
> >> > Signed-off-by: Paul Blakey <paulb@...lanox.com>  
> >>
> >> Very poor commit message.  What you're doing is re-enabling skip_sw
> >> filters on tunnel devices which semantically make no sense and
> >> shouldn't have been allowed in the first place.
> >>
> >> This will breaks block sharing between tunnels and HW netdevs (because
> >> you skip the tcf_block_cb_call() completely).  The entire egdev idea
> >> remains badly broken accepting filters like this:
> >>
> >> # tc filter add dev vxlan0 ingress \
> >>       matchall action skip_sw \
> >>               mirred egress redirect dev lo \
> >>               mirred egress redirect dev sw1np0  
> >
> > For above we probably need something like this (untested):
> >
> > diff --git a/net/sched/act_api.c b/net/sched/act_api.c
> > index 3f4cf930f809..71e5eebec31a 100644
> > --- a/net/sched/act_api.c
> > +++ b/net/sched/act_api.c
> > @@ -1511,7 +1511,7 @@ int tc_setup_cb_egdev_call(const struct net_device *dev,
> >         struct tcf_action_egdev *egdev = tcf_action_egdev_lookup(dev);
> >
> >         if (!egdev)
> > -               return 0;
> > +               return err_stop ? -EOPNOTSUPP : 0;
> >         return tcf_action_egdev_cb_call(egdev, type, type_data, err_stop);
> >  }
> >  EXPORT_SYMBOL_GPL(tc_setup_cb_egdev_call);  
> 
> Jakub,
> 
> We will test it out and let you know

That's probably insufficient, because the second action should be
skipped completely.  But an improvement nonetheless :)

> > But the correct fix is to remove egdev crutch completely IMO.  
> 
> Not against it, sometimes designs should change and be replaced
> with better ones, happens

Cool, I'm not sure when we'll get to it, but perhaps we can go over 
the ideas I presented at netconf on switchdev call next week (if it's
still active)?