From: ebiederm@xmission•com (Eric W. Biederman)
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: Pavel Emelyanov <xemul@parallels•com>,
Linux Netdev List <netdev@vger•kernel.org>,
David Miller <davem@davemloft•net>
Subject: Re: [PATCH 1/2] net: Allow to create links with given ifindex
Date: Mon, 30 Jul 2012 05:33:05 -0700 [thread overview]
Message-ID: <87k3xlfmym.fsf@xmission.com> (raw)
In-Reply-To: <1343649062.21269.23.camel@edumazet-glaptop> (Eric Dumazet's message of "Mon, 30 Jul 2012 13:51:02 +0200")
Eric Dumazet <eric.dumazet@gmail•com> writes:
> On Mon, 2012-07-30 at 03:49 -0700, Eric W. Biederman wrote:
>> Pavel Emelyanov <xemul@parallels•com> writes:
>>
>> > Currently the RTM_NEWLINK results in -EOPNOTSUPP if the ifinfomsg->ifi_index
>> > is not zero. I propose to allow requesting ifindices on link creation. This
>> > is required by the checkpoint-restore to correctly restore a net namespace
>> > (i.e. -- a container). The question what to do with pre-created devices such
>> > as lo or sit fbdev is open, but for manually created devices this can be
>> > solved by this patch.
>>
>> Have you walked through and found the locations where we still rely on
>> ifindex being globally unique?
>>
>> Last time I was working in this area there were serveral places where
>> things were indexed by just the interface index.
>
> Really ? This would be very strange.
There at least were places that used oif or iff without being pernet
last time I was working on this.
It was never code that I understood particularly well so my memory of
what that code is, is unfortunately fuzzy.
> AFAIK dev_new_index() is always called, even in the
> dev_change_net_namespace() case if there is a conflict.
Except we never have a conflict because it takes an absurd number of
network devices to cause a 32bit counter to wrap.
> And dev_new_index() could use a pernet net->ifindex instead of a
> shared/static one.
Yes. I made all of the core changes, and held back on making
dev_new_index() use a pernet net->ifindex because of a couple of problem
cases.
It has been a long time and those cases might have been fixed.
I'm not seeing anything obvious in the network stack with a quick skim,
but before we start relying on the property that interface indicies are
not globally unique I expect an good hard look at the networking stack
to see if any of those cases where there were problems still exist.
Eric
next prev parent reply other threads:[~2012-07-30 12:33 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-30 4:34 [PATCH 1/2] net: Allow to create links with given ifindex Pavel Emelyanov
2012-07-30 4:36 ` [PATCH 2/2] veth: Allow to create peer link " Pavel Emelyanov
2012-07-30 10:49 ` [PATCH 1/2] net: Allow to create links " Eric W. Biederman
2012-07-30 10:56 ` Eric W. Biederman
2012-07-31 9:03 ` Pavel Emelyanov
2012-07-31 11:58 ` Eric W. Biederman
2012-07-31 13:30 ` Pavel Emelyanov
2012-08-02 10:28 ` Eric Dumazet
2012-08-02 11:09 ` Eric W. Biederman
2012-08-02 23:37 ` David Miller
2012-08-02 23:26 ` David Miller
2012-08-03 5:45 ` Eric Dumazet
2012-08-03 5:51 ` Eric Dumazet
2012-08-03 23:56 ` David Miller
2012-08-04 7:10 ` Eric Dumazet
2012-08-04 8:25 ` David Miller
2012-07-30 11:51 ` Eric Dumazet
2012-07-30 12:33 ` Eric W. Biederman [this message]
2012-07-31 9:06 ` Pavel Emelyanov
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