netdev - Re: [RFC net-next] ipv4: Don't promote secondaries when flushing addresses

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Date:   Thu, 7 Jun 2018 13:00:29 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     netdev@...r.kernel.org
Cc:     Jakub Sitnicki <jkbs@...hat.com>
Subject: Re: [RFC net-next] ipv4: Don't promote secondaries when flushing
 addresses

On Thu, Jun 07, 2018 at 12:13:01PM +0200, Jakub Sitnicki wrote:
> Promoting secondary addresses on address removal makes flushing all
> addresses from a device with 1000's of them slow. This is because we
> cannot take down the secondary addresses when we are removing the
> primary one, which would make it faster.
> 
> However, the userspace, when performing a flush, will in the end remove
> all the addresses regardless of secondary address promotion taking
> place. Unfortunately the kernel currently cannot distinguish between a
> single address removal and a flush of all addresses.
> 
> To help with this case introduce a IFA_F_FLUSH flag that can be used by
> userspace to signal that a removal operation is being done because of a
> flush. When the flag is set, don't bother with secondary address
> promotion as we expect that secondary addresses will be removed soon as
> well.

Unless you intend to use the flag to allow deleting a specific address
with its secondaries (overriding promote_secondaries), maybe it would
be more practical to go even further and delete all addresses on the
interface if IFA_F_FLUSH is set so that userspace could delete all
addresses with one request.

Michal Kubecek