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From:   Oleksandr Mazur <oleksandr.mazur@plvision.eu>
To:     Jiri Pirko <jiri@resnulli.us>, Jakub Kicinski <kuba@kernel.org>
CC:     Ido Schimmel <idosch@idosch.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "jiri@nvidia.com" <jiri@nvidia.com>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next] net: core: devlink: add new trap action
 HARD_DROP
Thread-Topic: [PATCH net-next] net: core: devlink: add new trap action
 HARD_DROP
Thread-Index: AQHW7+i5SANyTFamkUKbFKKw5ahdBKoyAC0AgABXy4CABe7wAIAAAiAa
Date:   Mon, 25 Jan 2021 12:24:27 +0000
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References: <20210121112937.30989-1-oleksandr.mazur@plvision.eu>
 <20210121122152.GA2647590@shredder.lan>
 <20210121093605.49ba26ba@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>,<20210125121234.GJ3565223@nanopsycho.orion>
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Thu, Jan 21, 2021 at 06:36:05PM CET, kuba@kernel.org wrote:=0A=
>On Thu, 21 Jan 2021 14:21:52 +0200 Ido Schimmel wrote:=0A=
>> On Thu, Jan 21, 2021 at 01:29:37PM +0200, Oleksandr Mazur wrote:=0A=
>> > Add new trap action HARD_DROP, which can be used by the=0A=
>> > drivers to register traps, where it's impossible to get=0A=
>> > packet reported to the devlink subsystem by the device=0A=
>> > driver, because it's impossible to retrieve dropped packet=0A=
>> > from the device itself.=0A=
>> > In order to use this action, driver must also register=0A=
>> > additional devlink operation - callback that is used=0A=
>> > to retrieve number of packets that have been dropped by=0A=
>> > the device.=A0 =0A=
>> =0A=
>> Are these global statistics about number of packets the hardware dropped=
=0A=
>> for a specific reason or are these per-port statistics?=0A=
>> =0A=
>> It's a creative use of devlink-trap interface, but I think it makes=0A=
>> sense. Better to re-use an existing interface than creating yet another=
=0A=
>> one.=0A=
>=0A=
>Not sure if I agree, if we can't trap why is it a trap?=0A=
>It's just a counter.=0A=
=0A=
>+1=0A=
Device might be unable to trap only the 'DROP' packets, and this informatio=
n should be transparent for the user.=0A=
=0A=
I agree on the statement, that new action might be an overhead.=0A=
I could continue on with the solution Ido Schimmel proposed: since no new a=
ction would be needed and no UAPI changes are required, i could simply do t=
he dropped statistics (additional field) output added upon trap stats queir=
ing.=0A=
(In case if driver registerd callback, of course; and do so only for DROP a=
ctions)=