net: introduce ndo_set_rx_mode_async and netdev_rx_mode_work

Add ndo_set_rx_mode_async callback that drivers can implement instead
of the legacy ndo_set_rx_mode. The legacy callback runs under the
netif_addr_lock spinlock with BHs disabled, preventing drivers from
sleeping. The async variant runs from a work queue with rtnl_lock and
netdev_lock_ops held, in fully sleepable context.

When __dev_set_rx_mode() sees ndo_set_rx_mode_async, it schedules
netdev_rx_mode_work instead of calling the driver inline. The work
function takes two snapshots of each address list (uc/mc) under
the addr_lock, then drops the lock and calls the driver with the
work copies. After the driver returns, it reconciles the snapshots
back to the real lists under the lock.

Add netif_rx_mode_sync() to opportunistically execute the pending
workqueue update inline, so that rx mode changes are committed
before returning to userspace:
  - dev_change_flags (SIOCSIFFLAGS / RTM_NEWLINK)
  - dev_set_promiscuity
  - dev_set_allmulti
  - dev_ifsioc SIOCADDMULTI / SIOCDELMULTI
  - do_setlink (RTM_SETLINK)

Note that some deep hierarchies still do skip the lower updates via:
  - dev_uc_sync
  - dev_mc_sync

If we do end up hitting user-visible issues, we can add more calls to
netif_rx_mode_sync in specific places. But hopefully we should not,
the actual user-visible lists are still synced, it's that just HW state
that might be lagging.

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20260416185712.2155425-3-sdf@fomichev.me
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a84c55488b8c..6ed97f4c3bc6 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1119,6 +1119,16 @@ struct netdev_net_notifier {
  *	This function is called device changes address list filtering.
  *	If driver handles unicast address filtering, it should set
  *	IFF_UNICAST_FLT in its priv_flags.
+ *	Cannot sleep, called with netif_addr_lock_bh held.
+ *	Deprecated in favor of ndo_set_rx_mode_async.
+ *
+ * void (*ndo_set_rx_mode_async)(struct net_device *dev,
+ *				 struct netdev_hw_addr_list *uc,
+ *				 struct netdev_hw_addr_list *mc);
+ *	Async version of ndo_set_rx_mode which runs in process context
+ *	with rtnl_lock and netdev_lock_ops(dev) held. The uc/mc parameters
+ *	are snapshots of the address lists - iterate with
+ *	netdev_hw_addr_list_for_each(ha, uc).
  *
  * int (*ndo_set_mac_address)(struct net_device *dev, void *addr);
  *	This function  is called when the Media Access Control address
@@ -1439,6 +1449,10 @@ struct net_device_ops {
 	void			(*ndo_change_rx_flags)(struct net_device *dev,
 						       int flags);
 	void			(*ndo_set_rx_mode)(struct net_device *dev);
+	void			(*ndo_set_rx_mode_async)(
+					struct net_device *dev,
+					struct netdev_hw_addr_list *uc,
+					struct netdev_hw_addr_list *mc);
 	int			(*ndo_set_mac_address)(struct net_device *dev,
 						       void *addr);
 	int			(*ndo_validate_addr)(struct net_device *dev);
@@ -1903,6 +1917,8 @@ enum netdev_reg_state {
  *				has been enabled due to the need to listen to
  *				additional unicast addresses in a device that
  *				does not implement ndo_set_rx_mode()
+ *	@rx_mode_node:		List entry for rx_mode work processing
+ *	@rx_mode_tracker:	Refcount tracker for rx_mode work
  *	@uc:			unicast mac addresses
  *	@mc:			multicast mac addresses
  *	@dev_addrs:		list of device hw addresses
@@ -2294,6 +2310,8 @@ struct net_device {
 	unsigned int		promiscuity;
 	unsigned int		allmulti;
 	bool			uc_promisc;
+	struct list_head	rx_mode_node;
+	netdevice_tracker	rx_mode_tracker;
 #ifdef CONFIG_LOCKDEP
 	unsigned char		nested_level;
 #endif