Re: [PATCH net-next v4 0/4] netns: allow to identify peer netns

[Nicolas Dichtel]

Le 30/10/2014 19:41, Eric W. Biederman a Ãcrit :
> Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx> writes:
>
> > The goal of this serie is to be able to multicast netlink messages with an
> > attribute that identify a peer netns.
> > This is needed by the userland to interpret some informations contained in
> > netlink messages (like IFLA_LINK value, but also some other attributes in case
> > of x-netns netdevice (see also
> > http://thread.gmane.org/gmane.linux.network/315933/focus=316064 and
> > http://thread.gmane.org/gmane.linux.kernel.containers/28301/focus=4239)).
> >
> > Ids of peer netns are set by userland via a new genl messages. These ids are
> > stored per netns and are local (ie only valid in the netns where they are set).
> > To avoid allocating an int for each peer netns, I use idr_for_each() to retrieve
> > the id of a peer netns. Note that it will be possible to add a table (struct net
> > -> id) later to optimize this lookup if needed.
> >
> > Patch 1/4 introduces the netlink API mechanism to set and get these ids.
> > Patch 2/4 and 3/4 implements an example of how to use these ids in rtnetlink
> > messages. And patch 4/4 shows that the netlink messages can be symetric between
> > a GET and a SET.
> >
> > iproute2 patches are available, I can send them on demand.
>
> A quick reply.  I think this patchset is in the right general direction.
> There are some oddball details that seem odd/awkward to me such as using
> genetlink instead of rtnetlink to get and set the ids, and not having
> ids if they are not set (that feels like a maintenance/usability challenge).
No problem to use rtnetlink, in fact, I hesitated.

For the second point, I'm not sure to follow you: how to have an id, which will
not break migration, without asking the user to set it?
Note that if the user does not provide an id, you still have a magic value to
say "it's a peer netns but we don't know which one".

> I would like to give your patches a deep review, but I won't be able to
> do that for a couple of weeks.  I am deep in the process of moving,
> and will be mostly offline until about the Nov 11th.

No problem, I will wait.
I would be great to get a final version for the 3.19 ;-)


Thank you,
Nicolas
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