bonding: add ns target multicast address to slave device

Commit 4598380f9c54 ("bonding: fix ns validation on backup slaves")
tried to resolve the issue where backup slaves couldn't be brought up when
receiving IPv6 Neighbor Solicitation (NS) messages. However, this fix only
worked for drivers that receive all multicast messages, such as the veth
interface.

For standard drivers, the NS multicast message is silently dropped because
the slave device is not a member of the NS target multicast group.

To address this, we need to make the slave device join the NS target
multicast group, ensuring it can receive these IPv6 NS messages to validate
the slave’s status properly.

There are three policies before joining the multicast group:
1. All settings must be under active-backup mode (alb and tlb do not support
   arp_validate), with backup slaves and slaves supporting multicast.
2. We can add or remove multicast groups when arp_validate changes.
3. Other operations, such as enslaving, releasing, or setting NS targets,
   need to be guarded by arp_validate.

Fixes: 4e24be018eb9 ("bonding: add new parameter ns_targets")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index b1bffd8e9a95..15e0f14d0d49 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1008,6 +1008,8 @@ static void bond_hw_addr_swap(struct bonding *bond, struct slave *new_active,
 
 		if (bond->dev->flags & IFF_UP)
 			bond_hw_addr_flush(bond->dev, old_active->dev);
+
+		bond_slave_ns_maddrs_add(bond, old_active);
 	}
 
 	if (new_active) {
@@ -1024,6 +1026,8 @@ static void bond_hw_addr_swap(struct bonding *bond, struct slave *new_active,
 			dev_mc_sync(new_active->dev, bond->dev);
 			netif_addr_unlock_bh(bond->dev);
 		}
+
+		bond_slave_ns_maddrs_del(bond, new_active);
 	}
 }
 
@@ -2341,6 +2345,11 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
 	bond_compute_features(bond);
 	bond_set_carrier(bond);
 
+	/* Needs to be called before bond_select_active_slave(), which will
+	 * remove the maddrs if the slave is selected as active slave.
+	 */
+	bond_slave_ns_maddrs_add(bond, new_slave);
+
 	if (bond_uses_primary(bond)) {
 		block_netpoll_tx();
 		bond_select_active_slave(bond);
@@ -2350,7 +2359,6 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
 	if (bond_mode_can_use_xmit_hash(bond))
 		bond_update_slave_arr(bond, NULL);
 
-
 	if (!slave_dev->netdev_ops->ndo_bpf ||
 	    !slave_dev->netdev_ops->ndo_xdp_xmit) {
 		if (bond->xdp_prog) {
@@ -2548,6 +2556,12 @@ static int __bond_release_one(struct net_device *bond_dev,
 	if (oldcurrent == slave)
 		bond_change_active_slave(bond, NULL);
 
+	/* Must be called after bond_change_active_slave () as the slave
+	 * might change from an active slave to a backup slave. Then it is
+	 * necessary to clear the maddrs on the backup slave.
+	 */
+	bond_slave_ns_maddrs_del(bond, slave);
+
 	if (bond_is_lb(bond)) {
 		/* Must be called only after the slave has been
 		 * detached from the list and the curr_active_slave