Daniel Lezcano [off-list ref] writes:

Eric W. Biederman wrote:

quoted

From: Eric W. Biederman <redacted> - unquoted

This patch introduces NETIF_F_NETNS_LOCAL a flag to indicate
a network device is local to a single network namespace and
should never be moved.  Useful for pseudo devices that we
need an instance in each network namespace (like the loopback
device) and for any device we find that cannot handle multiple
network namespaces so we may trap them in the initial network
namespace.

This patch introduces the function dev_change_net_namespace
a function used to move a network device from one network
namespace to another.  To the network device nothing
special appears to happen, to the components of the network
stack it appears as if the network device was unregistered
in the network namespace it is in, and a new device
was registered in the network namespace the device
was moved to.

This patch sets up a namespace device destructor that
upon the exit of a network namespace moves all of the
movable network devices  to the initial network namespace
so they are not lost.

If you:
* create etun0/etun1
* create a namespace
* move etun1 to this namespace
*  rename the etun1 to eth0
*  kill the namespace

the former network device etun1 will be lost if you have in your parent
namespace an interface eth0 because it will conflict.
Perhaps, the first name should be restored before moving the device back to the
initial network namespace ?

Restoration of a previous name is no guarantee of anything.  Someone may have
renamed the some other interface etun1 in the original network namespace.

However if you look closely at the code.  You will discover that if it can't
keep the same name it will rename the device as it switches namespaces.
In particular it will become devN where N is replaced by some unused number.

That is what the pat parameter to dev_change_net_namespace is about.

I'm not exactly thrilled about the generic name but the code should work,
and I don't know if there is a name that makes better sense.

 -- Daniel

ps : nice patchset

Thanks.

Eric