netdev - Re: [PATCH net-next v2 5/5] net/sched: flower: Consider the number of tags for vlan filters

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Date:   Tue, 12 Apr 2022 16:16:10 +0300
From:   Boris Sukholitko <boris.sukholitko@...adcom.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Eric Dumazet <edumazet@...gle.com>,
        zhang kai <zhangkaiheb@....com>,
        Yoshiki Komachi <komachi.yoshiki@...il.com>,
        Ilya Lifshits <ilya.lifshits@...adcom.com>
Subject: Re: [PATCH net-next v2 5/5] net/sched: flower: Consider the number
 of tags for vlan filters

On Tue, Apr 12, 2022 at 02:12:15PM +0200, Jiri Pirko wrote:
> Tue, Apr 12, 2022 at 01:40:49PM CEST, boris.sukholitko@...adcom.com wrote:
> >On Tue, Apr 12, 2022 at 01:09:35PM +0200, Jiri Pirko wrote:
> >> Tue, Apr 12, 2022 at 12:02:36PM CEST, boris.sukholitko@...adcom.com wrote:
> >> >Currently the existence of vlan filters is conditional on the vlan
> >> >protocol being matched in the tc rule. I.e. the following rule:
> >> >
> >> >tc filter add dev eth1 ingress flower vlan_prio 5
> >> >
> >> >is illegal because we lack protocol 802.1q in the rule.
> >> >
> >> >Having the num_of_vlans filter configured removes this restriction. The
> >> >following rule becomes ok:
> >> >
> >> >tc filter add dev eth1 ingress flower num_of_vlans 1 vlan_prio 5
> >> >
> >> >because we know that the packet is single tagged.
> >> >
> >> >We achieve the above by having is_vlan_key helper look at the number of
> >> 
> >> Sorry to be a nitpicker, but who's "we"? When I read the patch
> >> description, I need to understand clearly what the patch is doing, which
> >> is not this case. You suppose to command the codebase what to do.
> >> I fail to see that :/
> >> 
> >> 
> >
> >What do you think of the following description? The description consists
> >of two parts: the first provides motivation for the patch, the second is
> >the way the motivation is implemented. I've judiciously edited out the
> >"we"-word. :)
> >
> ><description>
> >
> >Currently the existence of vlan filters is conditional on the vlan
> >protocol being matched in the tc rule. I.e. the following rule:
> >
> >tc filter add dev eth1 ingress flower vlan_prio 5
> >
> >is illegal because vlan protocol (e.g. 802.1q) does not appear in the rule.
> >
> >Having the num_of_vlans filter configured removes this restriction. The
> >following rule becomes ok:
> >
> >tc filter add dev eth1 ingress flower num_of_vlans 1 vlan_prio 5
> 
> So this is what this patch allows?

Yes.

> You are talking about it as it is
> already possible with the code before this patch being applied.
> 

Sorry for the confusion. In the updated description I try to make the
distinction much clearer.

> 
> >
> >because having num_of_vlans==1 implies that the packet is single tagged.
> >
> >To make the above possible, is_vlan_key helper is changed to look at the
> >number of vlans in addition to the vlan ethertype.
> 
> What "is changed"? You should tell the codebase what to do, what toadd,
> remove or change. If you did that, it would be very clear to the reader
> what the patch is supposed to do.
> 

The "changed" refers to the code of is_vlan_key function which is
changed by this patch. Please see the updated description.

> 
> >
> >Outer tag vlan filters (e.g.  vlan_prio) require the number of vlan tags
> >be greater than 0. Inner filters (e.g. cvlan_prio) require the number of
> >vlan tags be greater than 1.
> 
> Again, unclear what this describes, if the current code before the patch
> or the state after this patch.
> 

What about the following:

<description>

Before this commit the existence of vlan filters was conditional on the vlan
protocol being matched in the tc rule. For example, the following rule:

tc filter add dev eth1 ingress flower vlan_prio 5

was illegal because vlan protocol (e.g. 802.1q) does not appear in the rule.

This commit removes the above restriction. Having the num_of_vlans
filter configured allows further matching on vlan attributes. The
following rule is ok now:

tc filter add dev eth1 ingress flower num_of_vlans 1 vlan_prio 5

because having num_of_vlans==1 implies that the packet is single tagged.

To do this, this commit changes is_vlan_key helper to look at the number
of vlans in addition to the vlan ethertype. Outer (e.g. vlan_prio) and
inner (e.g. cvlan_prio) tag vlan filters require the number of vlan tags
to be greater then 0 and 1 accordingly.

As a result of this commit, the ethertype may be set to 0 when matching
on the number of vlans. This commit changes fl_set_key_vlan to avoid
setting key, mask vlan_tpid for the 0 ethertype.

</description>

Is this going into the right direction?

Thanks,
Boris.

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