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Subject: Re: [Bridge] [RFC net-next Patch 0/3] net: bridge: mrp: Add support
 for Media Redundancy Protocol(MRP)
To:     Stephen Hemminger <stephen@networkplumber.org>,
        Horatiu Vultur <horatiu.vultur@microchip.com>
Cc:     andrew@lunn.ch, jakub.kicinski@netronome.com,
        nikolay@cumulusnetworks.com, netdev@vger.kernel.org,
        roopa@cumulusnetworks.com, bridge@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, vivien.didelot@gmail.com,
        UNGLinuxDriver@microchip.com, anirudh.venkataramanan@intel.com,
        jiri@mellanox.com, jeffrey.t.kirsher@intel.com, dsahern@gmail.com,
        olteanv@gmail.com, davem@davemloft.net,
        Jesper Dangaard Brouer <brouer@redhat.com>
References: <20200109150640.532-1-horatiu.vultur@microchip.com>
 <20200109081907.06281c0f@hermes.lan>
From:   =?UTF-8?Q?Asbj=c3=b8rn_Sloth_T=c3=b8nnesen?= <ast@fiberby.net>
Message-ID: <da02006c-dc9d-ce1a-861e-4fc1c1dc2830@fiberby.net>
Date:   Thu, 9 Jan 2020 17:41:33 +0000
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Hi Horatiu and Stephen,

Horatiu, thanks for giving this a try. I am looking forward to maybe someday
be able to run ERPS on white box switches.

On 1/9/20 4:19 PM, Stephen Hemminger wrote:
> Can this be implemented in userspace?
> 
> Putting STP in the kernel was a mistake (even original author says so).
> Adding more control protocols in kernel is a security and stability risk.

Another case is VRRP, ERPS (ITU-T G.8032), VRRP group.

My use-case might not be common, but I have machines with about 10k net_dev (QinQ),
I would like to be able to do VRRP group on the outer VLANs, which are only a few
hundred instances without excessive context switching. I would then keep the the
normal keep-alive state machine in kernel, basically a BPF-based timed periodic
packet emitter facility and a XDP recieve hook. So only setup and event handling
has to context switched to user-space.

Unfortunately I haven't had time to explore this yet, but I think such an approach
could solve a few of the reasons that scalable bridge/ring/ha protocols have to wait
20 years before being implemented in Linux.

-- 
Best regards
Asbjørn Sloth Tønnesen
Network Engineer
Fiberby ApS - AS42541