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

From: Eric W. Biederman
Date: Tue May 17 2011 - 10:33:32 EST

David Lamparter <equinox@xxxxxxxxxx> writes:

> On Sat, May 07, 2011 at 07:18:44AM -0700, Eric W. Biederman wrote:
>> 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.
>> 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.
> [...]
>> Subject: [PATCH] iproute2: Add processless netnwork namespace support.
> [...]
>> Configuration specific to a network namespace that
>> would ordinarily be stored under /etc/ is stored under
>> /etc/netns/<name>. For example if the dns server
>> configuration is different for your vpn you would
>> create a file /etc/netns/myvpn/resolv.conf.
>> File descriptors that can be used to manipulate a
>> network namespace can be created by opening
>> /var/run/netns/<NAME>.
>> This adds the following commands to iproute.
>> ip netns add NAME
>> ip netns delete NAME
>> ip netns monitor
>> ip netns list
>> ip netns exec NAME cmd ....
>> ip link set DEV netns NAME
> funny, this is almost exactly what my code does - though you're probably
> doing it better and have more features ;)

Well if it has more features it is only because I have managed to keep
everything simple enough that adding features was easy. I ignored all
of the hard bits.

> git://
> It currently forks off a daemon to keep the namespace open; attaching is
> not possible yet, but opening a socket in a different namespace is.

I went the round of keeping a daemon open, saw how much code that
takes and how fragile that can be in the corner cases and decided to
patch the kernel to make the interfaces better.

> Most of the actual management (mounting things & co.) I offloaded to
> some shell scripts; I use it together with GNU screen (which makes it
> very nice to grab one of the namespaces and start/stop/manage/...
> things).

That does sound like a nice way of doing the management.

> I also have patches for OpenVPN and pptpd floating around that make it
> possible to 'cross' namespace boundaries, i.e. the VPN servers listen in
> one namespace and have their devices in another.

For openvpn I have managed to get away with simply using an up script.
Mostly the script is:

ip netns add $NSNAME || true
ip netns exec $NSNAME ip link set lo up
ip link set $dev netns $NSNAME
ip netns exec $NSNAME ip link set $dev up
ip netns exec $NSNAME ifconfig $dev $ifconfig_local netmask $ifconfig_netmask broadcast $ifconfig_broadcast

With a few extra bits for dns options and routes. If I had an openvpn
built with the iproute option I expect I could get away by just wrapping
iproute. Not that I would mind a patched openvpn.

Personally I think using a vpn in a network namespace seems like a
killer feature.

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