Re: [PATCH net-next 1/4] vxlan: Join / leave MC group after remote changes

[Petr Machata <petrm@nvidia.com>]

Paolo Abeni <pabeni@redhat.com> writes:

> On 2/11/25 3:56 PM, Petr Machata wrote:
>> Paolo Abeni <pabeni@redhat.com> writes:
>>> On 2/7/25 6:34 PM, Petr Machata wrote:
>>>> @@ -3899,6 +3904,11 @@ static void vxlan_config_apply(struct net_device *dev,
>>>>  			dev->mtu = conf->mtu;
>>>>  
>>>>  		vxlan->net = src_net;
>>>> +
>>>> +	} else if (vxlan->dev->flags & IFF_UP) {
>>>> +		if (vxlan_addr_multicast(&vxlan->default_dst.remote_ip) &&
>>>> +		    rem_changed)
>>>> +			vxlan_multicast_leave(vxlan);
>>>
>>> AFAICS vxlan_vni_update_group() is not completely ignore
>>> vxlan_multicast_{leave,join} errors. Instead is bailing out as soon as
>>> any error happens. For consistency's sake I think it would be better do
>>> the same here.
>>>
>>> Also I have the feeling that ending-up in an inconsistent status with no
>>> group joined would be less troublesome than the opposite.
>> 
>> This can already happen FWIW. If you currently want to change the remote
>> group address in a way that doesn't break things, you take the netdevice
>> down, then change it, then bring it back up. The leave during downing
>> can fail and will not be diagnosed. (Nor can it really be, you can't
>> veto downing.)
>
> I see.
>
>> I can add the bail-outs that you ask for, but I don't know that there is
>> a way to resolve these issues for real.
>
> The main point I made was about consistency: making the
> vxlan_config_apply() behavior as close as possible to
> vxlan_vni_update_group() as stated in the commit message.

No problem, I'll send a v2.