Re: [RFC, net-next] net: qos: introduce a frer action to implement 802.1CB

[Ferenc Fejes]

On 2021. 09. 28. 13:44, Xiaoliang Yang wrote:
> This patch introduce a frer action to implement frame replication and
> elimination for reliability, which is defined in IEEE P802.1CB.

HiXiaoliang!

thanks for your efforts to introduce afreraction to implement frame 
replication and elimination for reliability, which is defined in IEEE 
P802.1CB-2017. I would like to relay a small comment from our team, 
regarding to the FRER, not particularly to the code.

Support of RTAG format is very straightforward.

Since 2017, several maintenance items were opened regarding IEEE 
P802.1CB-2017 to fix some errors in the standard. Discussions results 
will be published soon e.g., in IEEE P802.1CBdb 
(https://1.ieee802.org/tsn/802-1cbdb/).

One of the maintenance items impacts the vector recovery algorithm itself.

Details on the problem and the solution are here:

-https://www.802-1.org/items/370

-https://www.ieee802.org/1/files/public/docs2020/maint-varga-257-FRER-recovery-window-0320-v01.pdf 
<https://www.ieee802.org/1/files/public/docs2020/maint-varga-257-FRER-recovery-window-0320-v01.pdf>

It is a small but important fix. There is an incorrect reference to the 
size of the recovery window, when a received packet is checked to be 
out-of-range or not. Without this fix the vector recovery algorithm do 
not work properly in some scenarios.

Please consider to update your patch to reflect the maintenance efforts 
of IEEE to correct .1CB-2017 related issues.

> There are two modes for frer action: generate and push the tag, recover
> and pop the tag. frer tag has three types: RTAG, HSR, and PRP. This
> patch only supports RTAG now.
>
> User can push the tag on egress port of the talker device, recover and
> pop the tag on ingress port of the listener device. When it's a relay
> system, push the tag on ingress port, or set individual recover on
> ingress port. Set the sequence recover on egress port.
>
> Use action "mirred" to do split function, and use "vlan-modify" to do
> active stream identification function on relay system.
>
All of our research in the topic based on a in-house userspace FRER 
implementation but we are looking forward to test your work in the future.

Thanks,

Ferenc