Re: [PATCH net] bonding: add ns target multicast address to slave device

[Hangbin Liu <liuhangbin@gmail.com>]

On Mon, Oct 21, 2024 at 06:05:11PM +0200, Jay Vosburgh wrote:
> Hangbin Liu <liuhangbin@gmail.com> wrote:
> 
> >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.
> >
> >Fixes: 4e24be018eb9 ("bonding: add new parameter ns_targets")
> >Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
> 
> 	This seems fairly involved; would it be simpler to have
> bond_hw_addr_swap() and/or bond_change_active_slave() insure that the
> MAC multicast list is configured in the backup interface if arp_validate
> is set appropriately and there's a NS target configured?  That will make
> the MAC multicast list more inclusive than necessary, but I think the
> implementation will be much less involved.

You are right. Limit the mcast list only on backup salve would be less
involved.

So I will do:

1. Add mcast list to all backup salves when setting NS targets.
2. Add mcast to new backup slave, remove the list on new active slave on
   bond_hw_addr_swap()
3. Remove all mcast list when release slave
4. All the changed need to be with arp_validate and NS targets configured.

Thanks
Hangbin