linux-kernel - Re: [Patch net-next 0/3] Add support for mdb offload failure notification

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Message-ID: <039a0673-6254-45a0-b511-69d2a15aa96d@blackwall.org>
Date: Thu, 20 Mar 2025 08:17:22 +0200
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Joseph Huang <Joseph.Huang@...min.com>, netdev@...r.kernel.org
Cc: Joseph Huang <joseph.huang.2024@...il.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Roopa Prabhu <roopa@...dia.com>, Simon Horman <horms@...nel.org>,
 linux-kernel@...r.kernel.org, bridge@...ts.linux.dev
Subject: Re: [Patch net-next 0/3] Add support for mdb offload failure
 notification

On 3/19/25 00:42, Joseph Huang wrote:
> Currently the bridge does not provide real-time feedback to user space
> on whether or not an attempt to offload an mdb entry was successful.
> 
> This patch set adds support to notify user space about successful and
> failed offload attempts, and the behavior is controlled by a new knob
> mdb_notify_on_flag_change:
> 
> 0 - the bridge will not notify user space about MDB flag change
> 1 - the bridge will notify user space about flag change if either
>     MDB_PG_FLAGS_OFFLOAD or MDB_PG_FLAGS_OFFLOAD_FAILED has changed
> 2 - the bridge will notify user space about flag change only if
>     MDB_PG_FLAGS_OFFLOAD_FAILED has changed
> 
> The default value is 0.
> 
> A break-down of the patches in the series:
> 
> Patch 1 adds offload failed flag to indicate that the offload attempt
> has failed. The flag is reflected in netlink mdb entry flags.
> 
> Patch 2 adds the knob mdb_notify_on_flag_change, and notify user space
> accordingly in br_switchdev_mdb_complete() when the result is known.
> 
> Patch 3 adds netlink interface to manipulate mdb_notify_on_flag_change
> knob.
> 
> This patch set was inspired by the patch series "Add support for route
> offload failure notifications" discussed here:
> https://lore.kernel.org/all/20210207082258.3872086-1-idosch@idosch.org/
> 
> Joseph Huang (3):
>   net: bridge: mcast: Add offload failed mdb flag
>   net: bridge: mcast: Notify on offload flag change
>   net: bridge: Add notify on flag change netlink i/f
> 
>  include/uapi/linux/if_bridge.h |  9 +++++----
>  include/uapi/linux/if_link.h   | 14 ++++++++++++++
>  net/bridge/br_mdb.c            | 30 +++++++++++++++++++++++++-----
>  net/bridge/br_multicast.c      | 25 +++++++++++++++++++++++++
>  net/bridge/br_netlink.c        | 21 +++++++++++++++++++++
>  net/bridge/br_private.h        | 26 +++++++++++++++++++++-----
>  net/bridge/br_switchdev.c      | 31 ++++++++++++++++++++++++++-----
>  7 files changed, 137 insertions(+), 19 deletions(-)
> 

Hi,
Could you please share more about the motivation - why do you need this and
what will be using it? Also why do you need an option with 3 different modes
instead of just an on/off switch for these notifications?

Thanks,
 Nik