netdev - Re: [PATCH net-next v2 09/11] vxlan: Add MDB data path support

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Message-ID: <4e6c9f88-d241-1e5f-78c2-cf4f592750b9@blackwall.org>
Date:   Thu, 16 Mar 2023 10:55:38 +0200
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     Ido Schimmel <idosch@...dia.com>, netdev@...r.kernel.org,
        bridge@...ts.linux-foundation.org
Cc:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        edumazet@...gle.com, roopa@...dia.com, petrm@...dia.com,
        mlxsw@...dia.com
Subject: Re: [PATCH net-next v2 09/11] vxlan: Add MDB data path support

On 15/03/2023 15:11, Ido Schimmel wrote:
> Integrate MDB support into the Tx path of the VXLAN driver, allowing it
> to selectively forward IP multicast traffic according to the matched MDB
> entry.
> 
> If MDB entries are configured (i.e., 'VXLAN_F_MDB' is set) and the
> packet is an IP multicast packet, perform up to three different lookups
> according to the following priority:
> 
> 1. For an (S, G) entry, using {Source VNI, Source IP, Destination IP}.
> 2. For a (*, G) entry, using {Source VNI, Destination IP}.
> 3. For the catchall MDB entry (0.0.0.0 or ::), using the source VNI.
> 
> The catchall MDB entry is similar to the catchall FDB entry
> (00:00:00:00:00:00) that is currently used to transmit BUM (broadcast,
> unknown unicast and multicast) traffic. However, unlike the catchall FDB
> entry, this entry is only used to transmit unregistered IP multicast
> traffic that is not link-local. Therefore, when configured, the catchall
> FDB entry will only transmit BULL (broadcast, unknown unicast,
> link-local multicast) traffic.
> 
> The catchall MDB entry is useful in deployments where inter-subnet
> multicast forwarding is used and not all the VTEPs in a tenant domain
> are members in all the broadcast domains. In such deployments it is
> 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].
> 
> If the packet did not match an MDB entry (or if the packet is not an IP
> multicast packet), return it to the Tx path, allowing it to be forwarded
> according to the FDB.
> 
> If the packet did match an MDB entry, forward it to the associated
> remote VTEPs. However, if the entry is a (*, G) entry and the associated
> remote is in INCLUDE mode, then skip over it as the source IP is not in
> its source list (otherwise the packet would have matched on an (S, G)
> entry). Similarly, if the associated remote is marked as BLOCKED (can
> only be set on (S, G) entries), then skip over it as well as the remote
> is in EXCLUDE mode and the source IP is in its source list.
> 
> [1] https://datatracker.ietf.org/doc/html/draft-ietf-bess-evpn-irb-mcast#section-2.6
> 
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> ---
> 
> Notes:
>     v2:
>     * Use htons() in 'case' instead of ntohs() in 'switch'.
> 
>  drivers/net/vxlan/vxlan_core.c    |  15 ++++
>  drivers/net/vxlan/vxlan_mdb.c     | 114 ++++++++++++++++++++++++++++++
>  drivers/net/vxlan/vxlan_private.h |   6 ++
>  3 files changed, 135 insertions(+)
> 

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