linux-kernel - Re: [RFC net-next v3 06/10] net: bridge: mrp: switchdev: Extend switchdev API to offload MRP

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Message-ID: <20200126132213.fmxl5mgol5qauwym@soft-dev3.microsemi.net>
Date:   Sun, 26 Jan 2020 14:22:13 +0100
From:   Horatiu Vultur <horatiu.vultur@...rochip.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        <bridge@...ts.linux-foundation.org>, <jiri@...nulli.us>,
        <ivecera@...hat.com>, <davem@...emloft.net>,
        <roopa@...ulusnetworks.com>, <nikolay@...ulusnetworks.com>,
        <anirudh.venkataramanan@...el.com>, <olteanv@...il.com>,
        <jeffrey.t.kirsher@...el.com>, <UNGLinuxDriver@...rochip.com>
Subject: Re: [RFC net-next v3 06/10] net: bridge: mrp: switchdev: Extend
 switchdev API to offload MRP

The 01/25/2020 17:35, Andrew Lunn wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> > SWITCHDEV_OBJ_ID_RING_TEST_MRP: This is used when to start/stop sending
> >   MRP_Test frames on the mrp ring ports. This is called only on nodes that have
> >   the role Media Redundancy Manager.
> 
> How do you handle the 'headless chicken' scenario? User space tells
> the port to start sending MRP_Test frames. It then dies. The hardware
> continues sending these messages, and the neighbours thinks everything
> is O.K, but in reality the state machine is dead, and when the ring
> breaks, the daemon is not there to fix it?
> 
> And it is not just the daemon that could die. The kernel could opps or
> deadlock, etc.
> 
> For a robust design, it seems like SWITCHDEV_OBJ_ID_RING_TEST_MRP
> should mean: start sending MRP_Test frames for the next X seconds, and
> then stop. And the request is repeated every X-1 seconds.

I totally missed this case, I will update this as you suggest.

> 
>      Andrew

-- 
/Horatiu