netdev - Re: [PATCH net-next 09/14] bridge: mcast: Add support for (*, G) with a source list and filter mode

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Message-ID: <Y5SKlVl6cuSp1Ib1@shredder>
Date:   Sat, 10 Dec 2022 15:33:09 +0200
From:   Ido Schimmel <idosch@...dia.com>
To:     Nikolay Aleksandrov <razor@...ckwall.org>
Cc:     netdev@...r.kernel.org, bridge@...ts.linux-foundation.org,
        davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        edumazet@...gle.com, roopa@...dia.com, mlxsw@...dia.com
Subject: Re: [PATCH net-next 09/14] bridge: mcast: Add support for (*, G)
 with a source list and filter mode

On Fri, Dec 09, 2022 at 09:41:05AM +0200, Nikolay Aleksandrov wrote:
> On 08/12/2022 17:28, Ido Schimmel wrote:
> > In preparation for allowing user space to add (*, G) entries with a
> > source list and associated filter mode, add the necessary plumbing to
> > handle such requests.
> > 
> > Extend the MDB configuration structure with a currently empty source
> > array and filter mode that is currently hard coded to EXCLUDE.
> > 
> > Add the source entries and the corresponding (S, G) entries before
> > making the new (*, G) port group entry visible to the data path.
> > 
> > Handle the creation of each source entry in a similar fashion to how it
> > is created from the data path in response to received Membership
> > Reports: Create the source entry, arm the source timer (if needed), add
> > a corresponding (S, G) forwarding entry and finally mark the source
> > entry as installed (by user space).
> > 
> > Add the (S, G) entry by populating an MDB configuration structure and
> > calling br_mdb_add_group_sg() as if a new entry is created by user
> > space, with the sole difference that the 'src_entry' field is set to
> > make sure that the group timer of such entries is never armed.
> > 
> > Note that it is not currently possible to add more than 32 source
> > entries to a port group entry. If this proves to be a problem we can
> > either increase 'PG_SRC_ENT_LIMIT' or avoid forcing a limit on entries
> > created by user space.
> > 
> 
> That can be tricky wrt EHT. If the limit is increased we have to consider the
> complexity and runtime, we might have to optimize it. In practice I think it's
> rare to have so many sources, but evpn might change that. :)

Yea, we don't currently have data as to whether this limit is OK or not.
Once we do we can make a more informed decision. Some options:

1. Slightly increase the current limit.
2. Remove the limit and move to an RB tree instead of a list.
3. Only install (*, G) EXCLUDE entries on the VXLAN port and let the
VXLAN MDB do more fine-grained filtering.

> 
> > Signed-off-by: Ido Schimmel <idosch@...dia.com>
> > ---
> > 
> > Notes:
> >     v1:
> >     * Use an array instead of a list to store source entries.
> > 
> >  net/bridge/br_mdb.c     | 128 +++++++++++++++++++++++++++++++++++++++-
> >  net/bridge/br_private.h |   7 +++
> >  2 files changed, 132 insertions(+), 3 deletions(-)
> > 
> 
> Acked-by: Nikolay Aleksandrov <razor@...ckwall.org>

Thanks!