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

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]>
---
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]>