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

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Date:   Tue, 17 Apr 2018 14:05:36 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     lorenzo.bianconi@...hat.com
Cc:     netdev@...r.kernel.org, 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.

Thank you.