Re: [PATCH net v3 1/1] net: bridge: use option bits for CFM/MRP frame handlers

[Nikolay Aleksandrov <razor@blackwall.org>]

On 03/09/2026 09:56, Zhiling Zou wrote:
> CFM and MRP register a global br_frame_type whose hlist_node is linked
> into the per-bridge frame_type_list when the first MEP/MRP instance is
> created. Enabling the protocol on multiple bridges therefore inserts the
> same node into multiple lists. Unregistering it on one bridge then
> corrupts list state belonging to another.
> 
> These handlers can only be installed once per bridge, and they are
> uncommon. Track their per-bridge enable state with net_bridge option
> bits, which already live on the Rx hot cache line, and dispatch the
> matching handler directly from the receive path. Check both bits
> together first as an unlikely case.
> 
> Remove the generic frame_type_list and br_frame_type helpers, which
> have had no other users since CFM and MRP were added. That shrinks
> struct net_bridge by 8 bytes and drops the list walk from the fast
> path. When neither protocol is compiled in, BR_CFM_MRP_OPTS is 0 and
> the compiler prunes the branch.
> 
> Fixes: 90c628dd47ff ("net: bridge: extend the process of special frames")
> Fixes: dc32cbb3dbd7 ("bridge: cfm: Kernel space implementation of CFM. CCM frame RX added.")
> Cc: stable@vger.kernel.org
> Reported-by: Vega <vega@nebusec.ai>
> Suggested-by: Nikolay Aleksandrov <razor@blackwall.org>
> Co-developed-by: Yilin Zhu <zylzyl2333@gmail.com>
> Signed-off-by: Yilin Zhu <zylzyl2333@gmail.com>
> Signed-off-by: Zhiling Zou <zhilinz@nebusec.ai>
> ---
> changes in v3:
> - Always define BR_CFM_MRP_OPTS and keep the fast-path check
>    unconditional. Read br->options with READ_ONCE().
> - Drop CONFIG ifdefs around CFM/MRP dispatch. Provide header no-ops when
>    the protocols are not compiled in so the compiler can prune them.
> - v2 Link: https://lore.kernel.org/all/a43fdd12ad2fbb708c090dc4ead60f3e4aa8c0ac.1788159904.git.zhilinz@nebusec.ai/
> 
> changes in v2:
>    - Replace the per-bridge br_frame_type object with net_bridge option
>      bits.
>    - Dispatch CFM/MRP handlers from the receive path. Check both option
>      bits together first as an unlikely case.
>    - Cover MRP, which has the same shared hlist_node bug.
>    - Remove frame_type_list so CFM/MRP do not affect the fast path when
>      they are disabled in .config.
>    - v1 Link: https://lore.kernel.org/all/7198fe2845c30c60c6b3833dd78cead8c5966931.1778378864.git.zylzyl2333@gmail.com/
> 
>   net/bridge/br_cfm.c     | 11 +++--------
>   net/bridge/br_device.c  |  1 -
>   net/bridge/br_input.c   | 35 ++++++++++++++---------------------
>   net/bridge/br_mrp.c     | 13 +++----------
>   net/bridge/br_private.h | 26 +++++++++++++++-----------
>   5 files changed, 35 insertions(+), 51 deletions(-)
> 

Thank you for following up on this, the patch looks good to me.
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>