Re: [PATCH net 0/2] bridge/vxlan: fix reading neigh ha without synchronization

[Nikolay Aleksandrov <razor@blackwall.org>]

On 17/08/2026 17:36, Nikolay Aleksandrov wrote:
> Hi,
> Neigh ha address must be read using the seqlock to get a stable snapshot.
> Both the bridge and vxlan read it directly and can see partial updates.
> I reproduced both issues with running neigh updates and exercising these
> paths in parallel and saw partial addresses, e.g. updating between
> neigh A: 02:00:00:00:00:00 neigh B: fe:ff:ff:ff:ff:ff was able to observe
> 02:00:ff:ff:ff:ff and fe:ff:00:00:00:00 in packets. Noticed this initially
> in the bridge, then checked vxlan and its arp/neigh_reduce functions have
> the same bug, route_shortcircuit is doing the right thing already.
> 
> Cheers,
>   Nik
> 
> Nikolay Aleksandrov (2):
>    net: bridge: arp/nd proxy: fix reading neigh ha
>    vxlan: fix reading neigh ha
> 
>   drivers/net/vxlan/vxlan_core.c | 20 +++++++++++++-------
>   net/bridge/br_arp_nd_proxy.c   | 24 ++++++++++++++----------
>   2 files changed, 27 insertions(+), 17 deletions(-)
> 

(-CC bouncing emails)

Hmm perhaps it's better to use ETH_ALEN instead of MAX_ADDR_LEN to explicitly
show the expected len everywhere, it cannot be different anyway.
I'll do it for v2 after 24h.

Cheers,
  Nik