Re: [PATCH 0/7] Network namespace manipulation with file descriptors

Eric,

--On 7 May 2011 07:18:44 -0700 "Eric W. Biederman" [off-list ref] 
wrote:

You are essentially describing my setns system call.

Great - thanks.

quoted

As a secondary issue, ever without your patch, it would be really
useful to be able to read from userspace the current network namespace.
(i.e. the pid concerned, or 1 if not unshared). I would like to
simply modify a routing daemon's init script so it doesn't start
if in the host, e.g. at the top:
 [ `cat /proc/.../networknamespace` eq 1 ] && exit 0

You can read the processes network namespace by opening
/proc/<pid>/ns/net.  Unfortunately comparing the network
namespaces for identity is another matter.  You will probably
be better off simply forcing the routing daemon to start
in the desired network namespace in it's initscript.

It's solely a minor convenience issue. The network namespace is
unshared by the filing system namespace isn't. So there's an
/etc/init.d/bird, which I would like to remain there so I
can call it from the network namespace concerned (which
doesn't exist at boot time). But I'd also like it not to run
at boot time. So it would be useful to me if the script could
check whether it is running in the default namespace and
refuse to launch if so.

I note the /proc/ file you mention is not present in the main tree at
the moment.

For purposes of clarity please have a look at my work in
progress patch for iproute2.  This demonstrates how I expect
userspace to work in a multi-network namespace world.

Will do

-- 
Alex Bligh