Re: [PATCH net-next] neighbour: add support for NUD_PERMANENT proxy entries

[Paolo Abeni <pabeni@redhat.com>]

On 6/13/25 3:46 PM, Nicolas Escande wrote:
> As discussesd in [0] proxy entries (which are more configuration than
> runtime data) should stay when the link goes does down (carrier wise).
> This is what happens for regular neighbour entries added manually.
> 
> So lets fix this by:
>   - storing in the proxy entries the mdn_state (only NUD_PERMANENT for now)
>   - not removing NUD_PERMANENT proxy entries on carrier down by adding a
>     skip_perm arg to pneigh_ifdown_and_unlock() (same as how it's done in
>     neigh_flush_dev() for regular non-proxy entries)
> 
> Link: https://lore.kernel.org/netdev/c584ef7e-6897-01f3-5b80-12b53f7b4bf4@kernel.org/ [0]
> Signed-off-by: Nicolas Escande <nico.escande@gmail.com>
> ---
>  include/net/neighbour.h |  1 +
>  net/core/neighbour.c    | 13 ++++++++++---
>  2 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/include/net/neighbour.h b/include/net/neighbour.h
> index 9a832cab5b1d..d1e05b39cbb1 100644
> --- a/include/net/neighbour.h
> +++ b/include/net/neighbour.h
> @@ -182,6 +182,7 @@ struct pneigh_entry {
>  	netdevice_tracker	dev_tracker;
>  	u32			flags;
>  	u8			protocol;
> +	u8			state;

I think it's better to be consistent: either store the full state (u16,
without masking) or a `permanent` boolean alike: !!(ndm->ndm_state &
NUD_PERMANENT).

The current choice could confuse who is going to touch this code in the
future.

Thanks,

Paolo