netdev - Re: [PATCH v2 net-next] Ipvlan should return an error when an address is already in use.

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Message-ID: <20170609172501.GB2766@templeofstupid.com>
Date:   Fri, 9 Jun 2017 10:25:01 -0700
From:   Krister Johansen <kjlx@...pleofstupid.com>
To:     David Miller <davem@...emloft.net>
Cc:     kjlx@...pleofstupid.com, maheshb@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next] Ipvlan should return an error when an
 address is already in use.

On Fri, Jun 09, 2017 at 01:15:10PM -0400, David Miller wrote:
> From: Krister Johansen <kjlx@...pleofstupid.com>
> Date: Fri, 9 Jun 2017 10:13:10 -0700
> 
> > On Fri, Jun 09, 2017 at 12:26:46PM -0400, David Miller wrote:
> >> From: Krister Johansen <kjlx@...pleofstupid.com>
> >> Date: Thu, 8 Jun 2017 13:12:14 -0700
> >> 
> >> > The ipvlan code already knows how to detect when a duplicate address is
> >> > about to be assigned to an ipvlan device.  However, that failure is not
> >> > propogated outward and leads to a silent failure.
> >> > 
> >> > Introduce a validation step at ip address creation time and allow device
> >> > drivers to register to validate the incoming ip addresses.  The ipvlan
> >> > code is the first consumer.  If it detects an address in use, we can
> >> > return an error to the user before beginning to commit the new ifa in
> >> > the networking code.
> >> > 
> >> > This can be especially useful if it is necessary to provision many
> >> > ipvlans in containers.  The provisioning software (or operator) can use
> >> > this to detect situations where an ip address is unexpectedly in use.
> >> > 
> >> > Signed-off-by: Krister Johansen <kjlx@...pleofstupid.com>
> >> 
> >> Ok, applied, thank you.
> > 
> > Thanks, did this look otherwise alright?
> 
> Yes, I was mildly unsatisfied with the ipv6 addrconf situation but I know
> very well about that, and those kinds of addresses aren't of interest
> for what you are trying to achieve right?

That's correct.  I'm basically trying to catch the case where 'ip addr'
or its equivalent rtnetlink invocation manually configure an ip address
on a ipvlan.

-K