netdev - Re: [PATCH iproute2-next 7/7] bridge: mdb: Document the catchall MDB entries

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Message-ID: <5d4802d8-8853-dc95-efb6-3b840036675d@blackwall.org>
Date:   Thu, 23 Mar 2023 17:21:15 +0200
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     Ido Schimmel <idosch@...dia.com>, netdev@...r.kernel.org
Cc:     dsahern@...il.com, stephen@...workplumber.org, petrm@...dia.com,
        mlxsw@...dia.com
Subject: Re: [PATCH iproute2-next 7/7] bridge: mdb: Document the catchall MDB
 entries

On 21/03/2023 15:01, Ido Schimmel wrote:
> Document the catchall MDB entries used to transmit IPv4 and IPv6
> unregistered multicast packets.
> 
> In deployments where inter-subnet multicast forwarding is used, not all
> the VTEPs in a tenant domain are members in all the broadcast domains.
> It is therefore advantageous to transmit BULL (broadcast, unknown
> unicast and link-local multicast) and unregistered IP multicast traffic
> on different tunnels. If the same tunnel was used, a VTEP only
> interested in IP multicast traffic would also pull all the BULL traffic
> and drop it as it is not a member in the originating broadcast domain
> [1].
> 
> [1] https://datatracker.ietf.org/doc/html/draft-ietf-bess-evpn-irb-mcast#section-2.6
> 
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> ---
>  man/man8/bridge.8 | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/man/man8/bridge.8 b/man/man8/bridge.8
> index 9753ce9e92b4..4006ad23ea74 100644
> --- a/man/man8/bridge.8
> +++ b/man/man8/bridge.8
> @@ -1013,6 +1013,12 @@ device creation will be used.
>  device name of the outgoing interface for the VXLAN device to reach the remote
>  VXLAN tunnel endpoint.
>  
> +.in -8
> +The 0.0.0.0 and :: MDB entries are special catchall entries used to flood IPv4
> +and IPv6 unregistered multicast packets, respectively. Therefore, when these
> +entries are programmed, the catchall 00:00:00:00:00:00 FDB entry will only
> +flood broadcast, unknown unicast and link-local multicast.
> +
>  .in -8
>  .SS bridge mdb delete - delete a multicast group database entry
>  This command removes an existing mdb entry.

Reviewed-by: Nikolay Aleksandrov <razor@...ckwall.org>