etcd: Connection options (socket file, ipv6)

[aequitas]

I know some changes to the etcd code are upcoming. But these changes might be simple enough to already incorporate.

Changes:

• Allow unix domain socket to be used as client url
• Using ::1 as clienturl should not create default local ipv4 listener: http://[::1]:
• Adds no-network-standalone option which starts the server without any TCP ports open

The reason behind this is that open TCP ports make the mgmt daemon vulnerable as long as authentication is not implemented. Using unix:// sockets allows authorization using file system permissions and allows to run a isolated mgmt daemon to run safely. By default the sockets for standalone are created in the prefix directory which should be secured anyway.

This feature was originally posted as: #343

In that PR there where still issues with grpc. Those have been solved in the upstream.

[purpleidea]

Hey, I'm happy to review and merge what I can, I just can't promise which parts of this will get preserved in my upcoming re-write. (I'll try and incorporate as many as possible into the rebase, although my lack of understanding with parts of this might require that you re-submit anything I've missed in the future.)

Having said that, if you're okay with that, review is coming...

[purpleidea]

Here's the review! Thanks!

[aequitas]

Sound good to me. I'll jump in if you push the rewrite code to adapt where needed for this feature. But I don't expect much issues anyways as nothing fundamental is changed in this PR, only that more URL types (which etcd already supports) are allowed to be passed.

[purpleidea]

One small fix needed, and we need to move the chdir stuff out for now. Will this still work without the chdir part in?

[aequitas]

All chdir is removed. The feature is less convenient now but should still provide the core functionality needed.

[aequitas]

The build is currently failing on the ipv6-localhost tests. I guess this is due to TravisCI not having ipv6 enabled, but I'm still investigating.

[aequitas]

I disabled the test for hosts that don't have ipv6 localhost.

[purpleidea]

Patch looks perfect, thanks! I found a few nits to change. I'm only pointing them out because the missing newline was important, so you get them all.

Thanks again!

[aequitas]

That should be everything I think.

[purpleidea]

Looks perfect! Thank you again, Merged :)

[aequitas]

Thanks \o/

[purpleidea]

Thank you!

(If you feel like elaborating on where the chdir was needed-- (I'm guessing in etcd?) then you could open an upstream issue asking for absolute paths perhaps?)