Re: [PATCH batadv v2] batman-adv: gw: don't deselect gateway with active hardif

On 10/06/2026 20:35, Sven Eckelmann wrote:
> The batadv_hardif_cnt() was previously checking if there is an
> batadv_hard_iface->mesh_iface which is has the same mesh_iface. And since
> batadv_hardif_disable_interface() was resetting the
> batadv_hard_iface->mesh_iface after this check, it had to verify whether
> *1* interface was still part of the mesh_iface before it started the
> gateway deselection.
> 
> But after batadv_hardif_cnt() is now checking the lower interfaces of
> mesh_iface and batadv_hardif_disable_interface() already removed the
> interface via netdev_upper_dev_unlink() earlier in this function, the check
> must now make sure that *0* interfaces can be found by batadv_hardif_cnt()
> before selected gateway must be deselected. Otherwise the deselection would
> already happen one batadv_hard_iface too early.
> 
> Because a 0 hardif count from batadv_hardif_cnt() is equal to an empty
> list, it is possible to replace the counting with a simple list_empty().
> 
> Fixes: 702c52a87eab ("batman-adv: store hard_iface as iflink private data")
> Signed-off-by: Sven Eckelmann <[email protected]>

Reviewed-by: Nora Schiffer <[email protected]>

> ---
> Changes in v2:
> - dropped batadv_hardif_cnt, thanks Nora Schiffer
> - Link to v1: https://patch.msgid.link/[email protected]
> ---
>   net/batman-adv/hard-interface.c | 28 ++--------------------------
>   1 file changed, 2 insertions(+), 26 deletions(-)
> 
> diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
> index 60cee2c2..03d01c20 100644
> --- a/net/batman-adv/hard-interface.c
> +++ b/net/batman-adv/hard-interface.c
> @@ -814,30 +814,6 @@ int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface,
>   	return ret;
>   }
>   
> -/**
> - * batadv_hardif_cnt() - get number of interfaces enslaved to mesh interface
> - * @mesh_iface: mesh interface to check
> - *
> - * This function is only using RCU for locking - the result can therefore be
> - * off when another function is modifying the list at the same time. The
> - * caller can use the rtnl_lock to make sure that the count is accurate.
> - *
> - * Return: number of connected/enslaved hard interfaces
> - */
> -static size_t batadv_hardif_cnt(struct net_device *mesh_iface)
> -{
> -	struct batadv_hard_iface *hard_iface;
> -	struct list_head *iter;
> -	size_t count = 0;
> -
> -	rcu_read_lock();
> -	netdev_for_each_lower_private_rcu(mesh_iface, hard_iface, iter)
> -		count++;
> -	rcu_read_unlock();
> -
> -	return count;
> -}
> -
>   /**
>    * batadv_hardif_disable_interface() - Remove hard interface from mesh interface
>    * @hard_iface: hard interface to be removed
> @@ -878,8 +854,8 @@ void batadv_hardif_disable_interface(struct batadv_hard_iface *hard_iface)
>   	netdev_upper_dev_unlink(hard_iface->net_dev, hard_iface->mesh_iface);
>   	batadv_hardif_recalc_extra_skbroom(hard_iface->mesh_iface);
>   
> -	/* nobody uses this interface anymore */
> -	if (batadv_hardif_cnt(hard_iface->mesh_iface) <= 1)
> +	/* nobody uses this mesh interface anymore */
> +	if (list_empty(&hard_iface->mesh_iface->adj_list.lower))
>   		batadv_gw_check_client_stop(bat_priv);
>   
>   	hard_iface->mesh_iface = NULL;
> 
> ---
> base-commit: 385b248dd4e46c4ce022adeb1b13e547d1954901
> change-id: 20260607-gw-disable-check-f3393c3a4989
> 
> Best regards,
> --
> Sven Eckelmann <[email protected]>
>