provider/maas: Setup networks/VLANs in cloudinit

provider/maas: Setup networks/VLANs in cloudinit

This is possibly the final server-side task to
do in order to have VLANs/networks support in MAAS
as an MVP. Using the discovered networks and interfaces,
we prepare a few scripts to run at cloudinit time:
 * install the "vlan" package (so we can configure VLANs);
 * load the 8021q module for VLAN support;
 * skipping eth0 (part of br0 already), for each NIC
   discovered on the machine, add /etc/network/interfaces
   config and bring it up. For VLANs a few extra steps
   are done after their "parent" NIC is brought up

As this is an MVP, we assume the user has configured
their MAAS, nodes, and networks correctly, and also
has DHCP enabled on all networks (we lack the info
to configure the IPs statically from MAAS alone).

Live tested on MAAS (works if properly configured).

Next step will be to list machine networks in Status
and polish up some tech debt stuff (better unit tests,
more sanity checks in the CLI, etc.)

https://code.launchpad.net/~dimitern/juju-core/395-maas-setup-networks-cloudinit/+merge/215266

Requires: https://code.launchpad.net/~dimitern/juju-core/394-network-name-to-id-and-add-tags/+merge/214962

(do not edit description out of merge proposal)

[dimitern, 2014-04-10 17:58:30]

Please take a look.

[fwereade, 2014-04-11 08:05:58]

LGTM with a couple of matters of opinion to consider.

https://codereview.appspot.com/86600043/diff/1/provider/maas/environ.go
File provider/maas/environ.go (right):

https://codereview.appspot.com/86600043/diff/1/provider/maas/environ.go#newco...
provider/maas/environ.go:475: for _, script := range
setupNetworksOnBoot(networkInfo) {
This seems like a bit of an odd construction. setupNetworksOnBoot(cloudcfg,
networkInfo) might read more naturally?

https://codereview.appspot.com/86600043/diff/1/provider/maas/environ.go#newco...
provider/maas/environ.go:482: // networks on boot.
How maas-specific is this? I'd really like it if we could put this code
somewhere generic, but I'll leave it to your judgment; I'm just afraid of us
ending up with multiple subtly-differing versions of this code as we add
networks for other providers.

https://codereview.appspot.com/86600043/diff/1/provider/maas/environ.go#newco...
provider/maas/environ.go:485: 
d?

[dimitern, 2014-04-11 15:23:49]

Please take a look.

https://codereview.appspot.com/86600043/diff/1/provider/maas/environ.go
File provider/maas/environ.go (right):

https://codereview.appspot.com/86600043/diff/1/provider/maas/environ.go#newco...
provider/maas/environ.go:475: for _, script := range
setupNetworksOnBoot(networkInfo) {
On 2014/04/11 08:05:58, fwereade wrote:
> This seems like a bit of an odd construction. setupNetworksOnBoot(cloudcfg,
> networkInfo) might read more naturally?

Done.

https://codereview.appspot.com/86600043/diff/1/provider/maas/environ.go#newco...
provider/maas/environ.go:482: // networks on boot.
On 2014/04/11 08:05:58, fwereade wrote:
> How maas-specific is this? I'd really like it if we could put this code
> somewhere generic, but I'll leave it to your judgment; I'm just afraid of us
> ending up with multiple subtly-differing versions of this code as we add
> networks for other providers.

It's specific to MAAS only because we get []NetworkInfo from there (and because
we skip configuring eth0 due to the br0 bridge, but eventually as more providers
support container networking this will be the common case). Theoretically, it's
generic enough to put it in a common place, but make sure it doesn't get called
when it shouldn't. Also, we're going to get rid of this as soon as we have the
networker worker working :)
So think leaving it like that for now is OK.

https://codereview.appspot.com/86600043/diff/1/provider/maas/environ.go#newco...
provider/maas/environ.go:485: 
On 2014/04/11 08:05:58, fwereade wrote:
> d?

I left this to better separate NIC definitions when multiple entries are added.
If you don't mind I prefer to leave it.