Re: [PATCH v2 net] vxlan: Fix regression when dropping packets due to invalid src addresses

[Ido Schimmel <idosch@nvidia.com>]

On Mon, Jun 03, 2024 at 10:59:26AM +0200, Daniel Borkmann wrote:
> Commit f58f45c1e5b9 ("vxlan: drop packets from invalid src-address")
> has recently been added to vxlan mainly in the context of source
> address snooping/learning so that when it is enabled, an entry in the
> FDB is not being created for an invalid address for the corresponding
> tunnel endpoint.
> 
> Before commit f58f45c1e5b9 vxlan was similarly behaving as geneve in
> that it passed through whichever macs were set in the L2 header. It
> turns out that this change in behavior breaks setups, for example,
> Cilium with netkit in L3 mode for Pods as well as tunnel mode has been
> passing before the change in f58f45c1e5b9 for both vxlan and geneve.
> After mentioned change it is only passing for geneve as in case of
> vxlan packets are dropped due to vxlan_set_mac() returning false as
> source and destination macs are zero which for E/W traffic via tunnel
> is totally fine.
> 
> Fix it by only opting into the is_valid_ether_addr() check in
> vxlan_set_mac() when in fact source address snooping/learning is
> actually enabled in vxlan. This is done by moving the check into
> vxlan_snoop(). With this change, the Cilium connectivity test suite
> passes again for both tunnel flavors.
> 
> Fixes: f58f45c1e5b9 ("vxlan: drop packets from invalid src-address")
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> Cc: David Bauer <mail@david-bauer.net>
> Cc: Ido Schimmel <idosch@nvidia.com>
> Cc: Nikolay Aleksandrov <razor@blackwall.org>
> Cc: Martin KaFai Lau <martin.lau@kernel.org>

Reviewed-by: Ido Schimmel <idosch@nvidia.com>

Thanks!