Add gnt-network mode ext

[atta]

this patch allow the user to use the mode=ext within ganeti.
So if a vm is starting, the script "/usr/share/ganeti/extnetwork//up" given by the gnt-network-tag "ext_provider" is triggerd.

We use this to create a vxlan on the node wehn ever it is needed, but a lot of other things are imaginationable.

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for the commit author(s). If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.

[atta]

i have signed the CLA some time ago but it did not show up
Google Individual CLA Ansgar Jazdzewski Dec 03, 2012 21:57 PST

[googlebot]

CLAs look good, thanks!

[Morgawr]

Should I be closing this as duplicate of #42 or are you still working on this? If you're planning to submit a future PR with everything implemented, I'll take a look at that and close this one as duplicate of #42, otherwise I can independently review and merge this while waiting for the next one.

[iustin]

Ping, what's the status on this? And repeating the question on the disk io patch, should this rather be against master?

[atta]

hi can we bing this back up for ganeti 3.0? i will update the PR

[apoikos]

@atta, sure!

[rbott]

@atta could you try to re-implement this against the current master?

Also it needs documentation (it should be mentioned as an option in the instance parameter list but I think it also deserves some example code. Currently there is some network-related content in the installation tutorial. Maybe we should in general cover all network modes in the administrator's guide, but that is for another PR to address :-)

Update: it also needs to be covered in the up/downgrade code. In this case probably only the downgrade scenario is relevant, removing the then-illegal values from the config database.