Nicolas Dichtel [off-list ref] 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)).

Each network namespaces allocates its own ids for other netns (including
itself). The user can retrieve these ids via a new netlink messages, but only
if he has a FD which points to this netns. Dump is not implemented so that a
user cannot get the whole netns list.

The goal of this RFC is mainly to validate the principle, ie patch 1/5 and 2/5.
Patch 3/5 and 4/5 shows an example of how to use these ids in rtnetlink
messages. And patch 5/5 shows that the netlink messages can be symetric between
a GET and a SET.

This approach fundamentally breaks process migration, and calls for a
namespace of namespaces.

Which means this is a major mess that really isn't going to work because
it generates more problems than it solves.

Eric