Re: [PATCH stable-5.9.y] net: dsa: b53: Correct learning for standalone ports

On Wed, Feb 24, 2021 at 05:09:54PM -0800, Florian Fainelli wrote:

Standalone ports should not have learning enabled since all the frames
are always copied to the CPU port. This is particularly important in
case an user-facing port intentionally spoofs the CPU port's MAC
address. With learning enabled we would end up with the switch having
incorrectly learned the address of the CPU port which typically results
in a complete break down of network connectivity until the address
learned ages out and gets re-learned, from the correct port this time.

There was no control of the BR_LEARNING flag until upstream commit
4098ced4680a485c5953f60ac63dff19f3fb3d42 ("Merge branch 'brport-flags'")
which is why we default to enabling learning when the ports gets added
as a bridge member.

Fixes: 967dd82ffc52 ("net: dsa: b53: Add support for Broadcom RoboSwitch")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 drivers/net/dsa/b53/b53_common.c | 18 ++++++++++++++++++
 drivers/net/dsa/b53/b53_regs.h   |  1 +
 drivers/net/dsa/bcm_sf2.c        | 15 +--------------
 3 files changed, 20 insertions(+), 14 deletions(-)

Note, 5.9.y and 5.8.y are long end-of-life.  You can see that at the
front page of www.kernel.org if you ever are curious about it.

thanks,

greg k-h