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Date:   Mon, 12 Dec 2022 15:20:50 +0100
From:   Horatiu Vultur <horatiu.vultur@microchip.com>
To:     Vladimir Oltean <olteanv@gmail.com>
CC:     Michael Walle <michael@walle.cc>, <Steen.Hegelund@microchip.com>,
        <UNGLinuxDriver@microchip.com>, <daniel.machon@microchip.com>,
        <davem@davemloft.net>, <edumazet@google.com>, <kuba@kernel.org>,
        <lars.povlsen@microchip.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
        <pabeni@redhat.com>, <richardcochran@gmail.com>
Subject: Re: [PATCH net-next v3 4/4] net: lan966x: Add ptp trap rules
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The 12/09/2022 17:27, Vladimir Oltean wrote:
> 
Sorry for late reply!

> On Fri, Dec 09, 2022 at 04:30:10PM +0100, Horatiu Vultur wrote:
> > For example this rule:
> > tc filter add dev eth0 ingress chain 8000000 prio 1 handle 1 protocol all
> > flower skip_sw dst_mac 00:11:22:33:44:55/ff:ff:ff:ff:ff:ff action trap
> > action goto chain 8100000
> >
> > This will not be hit until you add this rule:
> > tc filter add dev eth0 ingress prio 1 handle 2 matchall skip_sw action goto chain 8000000
> >
> > Because this rule will enable the HW. Just to aligned to a SW
> > implementation of the tc, we don't enable the vcap until there is a rule
> > in chain 0 that has an action to go to chain 8000000 were it resides
> > IS2 rules.
> >
> > So for example, on a fresh started lan966x the user will add the following
> > rule:
> > tc filter add dev eth0 ingress chain 8000000 prio 1 handle 1 protocol
> > all flower skip_sw dst_mac 00:11:22:33:44:55/ff:ff:ff:ff:ff:ff action
> > trap action goto chain 8100000
> >
> > He expects this rule not to be hit as there is no rule in chain 0. Now if
> > PTP is started and it would enable vcap, then suddenly this rule may be
> > hit.
> 
> Is it too restrictive to only allow adding offloaded filters to a chain
> that has a valid goto towards it, coming (perhaps indirectly) from chain 0?

We were thinking to do something like this. With a small difference, to
allow the user to add filters to a chain, but offload them in HW only when
there is a valid goto towards. Instead of checking if there is a goto to
that chain. But I think we need to spend a little bit more time on this.
Any suggestion is more than welcome.

-- 
/Horatiu