linux-kernel - Re: [PATCH RFC 0/7] net: bridge: cfm: Add support for Connectivity Fault Management(CFM)

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Date:   Tue, 8 Sep 2020 13:35:09 +0200
From:   "Allan W. Nielsen" <allan.nielsen@...rochip.com>
To:     Henrik Bjoernlund - M31679 <Henrik.Bjoernlund@...rochip.com>
CC:     Nikolay Aleksandrov <nikolay@...dia.com>,
        "stephen@...workplumber.org" <stephen@...workplumber.org>,
        Horatiu Vultur - M31836 <Horatiu.Vultur@...rochip.com>,
        "bridge@...ts.linux-foundation.org" 
        <bridge@...ts.linux-foundation.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jiri@...lanox.com" <jiri@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Roopa Prabhu <roopa@...dia.com>,
        "idosch@...lanox.com" <idosch@...lanox.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        UNGLinuxDriver <UNGLinuxDriver@...rochip.com>
Subject: Re: [PATCH RFC 0/7] net: bridge: cfm: Add support for Connectivity
 Fault Management(CFM)

Hi,

On 08.09.2020 11:04, Henrik Bjoernlund - M31679 wrote:
>>On Sun, 2020-09-06 at 20:21 +0200, Horatiu Vultur wrote:
>>> The 09/04/2020 15:44, Stephen Hemminger wrote:
>>> > On Fri, 4 Sep 2020 09:15:20 +0000 Henrik Bjoernlund
>>> > <henrik.bjoernlund@...rochip.com> wrote:
>>Hi, I also had the same initial thought - this really doesn't seem to
>>affect the bridge in any way, it's only collecting and transmitting
>>information. I get that you'd like to use the bridge as a passthrough
>>device to switchdev to program your hw, could you share what would be
>>offloaded more specifically ?
>Yes.
>
>The HW will offload the periodic sending of CCM frames, and the
>reception.
>
>If CCM frames are not received as expected, it will raise an interrupt.
>
>This means that all the functionality provided in this series will be
>offloaded to HW.
>
>The offloading is very important on our HW where we have a small CPU,
>serving many ports, with a high frequency of CFM frames.
>
>The HW also support Link-Trace and Loop-back, which we may come back to
>later.
>
>>All you do - snooping and blocking these packets can easily be done
>>from user- space with the help of ebtables, but since we need to have
>>a software implementation/fallback of anything being offloaded via
>>switchdev we might need this after all, I'd just prefer to push as
>>much as possible to user-space.
In addition to Henriks comment, it is worth mentioning that we are
trying to push as much of the functionallity to user-space (learnings
from the MRP discussions).

This is why there are currently no in-kernel users of the CCM-lose
singnal. When a CCM-defect is happening the network typically needs to
be re-configured. This we are trying to keep in user-space.

>>I plan to review the individual patches tomorrow.
Thanks.

/Allan