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

[Nicolas Dichtel]

Le 05/11/2014 15:23, Nicolas Dichtel a Ãcrit :
> Le 31/10/2014 20:14, Eric W. Biederman a Ãcrit :
> > Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx> writes:
> >
> > > 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?
> >
> > We have that situtation with ifindex already.  Basically the thought is
> > to allow an id to be set, but also allow an id to be auto-generated if
> > we use an namespace without an id being set.
> If my understanding is correct, the difference is that we want to hide some
> netns.
> Do you think we can generate an id for each netns that does not have one and
> relying on the fact that this id has no meaning unless you have a netns file
> descriptor that allow you to get the id of this netns?
Any comment Eric ?


Thank you,
Nicolas
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/