netdev - Re: [Patch net] ipv6: restore the behavior of ipv6_sock_ac

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Date:	Sat, 06 Sep 2014 01:07:18 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Cong Wang <cwang@...pensource.com>
Cc:	Cong Wang <xiyou.wangcong@...il.com>,
	netdev <netdev@...r.kernel.org>,
	Sabrina Dubroca <sd@...asysnail.net>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [Patch net] ipv6: restore the behavior of ipv6_sock_ac_drop()

On Sat, Sep 6, 2014, at 00:41, Cong Wang wrote:
> On Fri, Sep 5, 2014 at 3:26 PM, Hannes Frederic Sowa
> <hannes@...essinduktion.org> wrote:
> > Hi Cong,
> >
> > Just doing normal review, really no bad intentions, just technical
> > follow-up. ;)
> 
> I believe you are not supposed to do it since definitely you
> said you don't want to work with me. You said it, not me,
> I respect any of your choice. :)

Oh no, you misunderstood me (maybe my bad). My only critique was that
you could have stated that you also saw a problem with the ENODEV return
before the patch was looked at by David.
Sure, let's forget that and work together.

> > On Fri, Sep 5, 2014, at 23:33, Cong Wang wrote:
> >> It is possible that the interface is already gone after joining
> >> the list of anycast on this interface as we don't hold a refcount
> >> for the device, in this case we are safe to ignore the error.
> >
> > anycast code actually inserts routes into the routing table and holds a
> > reference on the interface while that route is active.
> 
> But route could be deleted.

The routes are managed by the inet6_dev and it will drop the routes on
interface shutdown, correct. There is no strong reference from socket to
the routing entry. Only deleting a route should not work as it will
still be referenced by the anycast list in inet6_dev (though it won't
get used anymore).

> >> What's more important, for API compatibility we should not
> >> change this behavior for applications even if it were correct.
> >
> > IMHO adding new error codes never breaks existing applications because
> > there is no way they can explore all possible errno variables. Also we
> > already report ENODEV from multicast setsockopts. So I think it would be
> > ok to leave it as is, but I have no strong opinion on that and it would
> > be ok by me if the patch got accepted (maybe update the changelog).
> >
> 
> Again, too late to change, the code has been there since the beginning
> of git history. You should have a strong argument if you want to change
> it,
> otherwise restore old behavior, that is all. Obviously you don't even
> mention
> this when you accept that patch.

Let's settle this:
Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>

Bye,
Hannes
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