Hi Vladimir,

Hi Lukasz,

On Tue, Jan 09, 2024 at 01:32:34PM +0100, Lukasz Majewski wrote:

quoted

However, I'm wondering how the mainline Linux kernel could handle
HSR RedBox functionality (on document [1], Figure 2. we do have
"bridge" - OSI L2).

To be more interesting - br0 can be created between hsr0 and e.g.
lan3. But as expected communication breaks on both directions (to
SAN and to HSR ring).  

Yes, I suppose this is how a RedBox should be modeled. In principle
it's identical to how bridging with LAG ports (bond, team) works -
either in software or offloaded. 
The trouble is that the HSR driver
seems to only work with the DANH/DANP roles (as also mentioned in
Documentation/networking/dsa/dsa.rst). I don't remember what doesn't
work (or if I ever knew at all).

In the newest net-next only PRP_TLV_REDBOX_MAC is defined, which seems
to be REDBOX for DAN P (PRP).

It might be the address substitution
from hsr_xmit() that masks the MAC address of the SAN side device?

This needs to be further investigated.

quoted

Is there a similar functionality already present in the Linux kernel
(so this approach could be reused)?

My (very rough idea) would be to extend KSZ9477 bridge join
functions to check if HSR capable interface is "bridged" and then
handle frames in a special way.

However, I would like to first ask for as much input as possible -
to avoid any unnecessary work.  

First I'd figure out why the software data path isn't working, and if
it can be fixed. 

+1

Then, fix that if possible, and add a new selftest to
tools/testing/selftests/net/forwarding/, that should pass using veth
interfaces as lower ports.

Then, offloading something that has a clear model in software should
be relatively easy, though you might need to add some logic to DSA.
This is one place that needs to be edited, there may be others.

	/* dsa_port_pre_hsr_leave is not yet necessary since hsr
devices cannot
	 * meaningfully placed under a bridge yet
	 */

Ok, the LAG approach in /net/dsa/user.c can be used as an example.

Thanks for shedding some light on this issue :-)

quoted

Thanks in advance for help :-)

Link:

[1] -
https://ww1.microchip.com/downloads/en/Appnotes/AN3474-KSZ9477-High-Availability-Seamless-Redundancy-Application-Note-00003474A.pdf


Best regards,

Lukasz Majewski  

Best regards,

Lukasz Majewski

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