netdev - Re: [PATCH net-next] ipv6: send netlink notifications for manually configured addresses

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Message-ID: <CAJ0CqmUffJ+EjJavR_mCw+0FoYo+mLjvhxwrD8u1GDfbTT5gGA@mail.gmail.com>
Date:   Fri, 20 Apr 2018 00:23:17 +0200
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Thomas Haller <thaller@...hat.com>
Subject: Re: [PATCH net-next] ipv6: send netlink notifications for manually
 configured addresses

> From: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
> Date: Tue, 17 Apr 2018 11:54:39 +0200
>
>> Send a netlink notification when userspace adds a manually configured
>> address if DAD is enabled and optimistic flag isn't set.
>> Moreover send RTM_DELADDR notifications for tentative addresses.
>>
>> Some userspace applications (e.g. NetworkManager) are interested in
>> addr netlink events albeit the address is still in tentative state,
>> however events are not sent if DAD process is not completed.
>> If the address is added and immediately removed userspace listeners
>> are not notified. This behaviour can be easily reproduced by using
>> veth interfaces:
>>
>> $ ip -b - <<EOF
>>> link add dev vm1 type veth peer name vm2
>>> link set dev vm1 up
>>> link set dev vm2 up
>>> addr add 2001:db8:a:b:1:2:3:4/64 dev vm1
>>> addr del 2001:db8:a:b:1:2:3:4/64 dev vm1
>> EOF
>>
>> This patch reverts the behaviour introduced by the commit f784ad3d79e5
>> ("ipv6: do not send RTM_DELADDR for tentative addresses")
>>
>> Suggested-by: Thomas Haller <thaller@...hat.com>
>> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
>
> Ok, applied to net-next.
>
> It would be really nice if we clearly documented somewhere the exact
> situations where we desire ipv6 address netlink notifications to be
> sent out.
>
> Maybe even a common function that guards the event emission, where we
> encode the rules.  Or a comment somewhere prominent.  Something like
> that.
>
> Right now this isn't spelled out clearly anywhere, and that's probably
> why things keep being adjusted back and forth like this.

Sounds good, I will post a patch. Thanks

Regards,
Lorenzo

>
> Thank you.