Re: RFC Hanging clean-up of a namespace

On Thu, Jan 19, 2012 at 02:06:21PM -0500, David Miller wrote:

From: David Lamparter <redacted>

quoted

On Thu, Jan 19, 2012 at 12:40:02PM -0500, David Miller wrote:

quoted

From: Hans Schillstrom <redacted>

quoted

Closing of a namespace (container) can be delayed by ~ 2 minutes 
due to tcp timers ex tcp time wait (and of cource other things too).

I think there should be some kind of "forced close" of the Network stack
in ex free_nsproxy() 

I think this is unwise.

Keeping the timewait sockets around is necessary to absorb any lingering
packets in the network meant for those sockets.

If you truncate this activity, and then try to create another socket with
the same ID you'll run into the very problems time-wait is meant to
solve.

A network namespace is for practical matters a separate host on the
network. Killing the namespace therefore is akin to shutting down that
host, which on a real metal host doesn't wait for timewait sockets
either.

Creating a socket with the same parameters would actually require
installing a network environment similar to the closed namespace first;
if an user really does that he can reasonably anticipate the same issues
as arise from removing a host from the network and giving its address to
another host.

The assumption is that the address is moving, which might not be true.

I don't understand what you mean, what address may not be moving?

We're talking about dropping a netns. All of its addresses disappear,
all of its soft devices disappear. Its hard devices fall back into the
init namespace, is that what you're referring to?

Or are you referring to the case where the network namespace is
recreated immediately after? That would be akin to a reboot, and again a
physical box wouldn't wait for timewait sockets...