Add tunneldigger to the default and backbone images

[pmelange]

This addresses issue #690 where a node which has been set up to
use the bbbdigger package cannot connect to the bbb-vpn server after
a firmware upgrade.

Additionally, this has been agreed upon at the firmware planning meeting 12.06.2019 https://pad.freifunk.net/p/berlin-2019

[pmelange]

This commit has been cherry-picked into Gonzo-1.1.0-rc1. It would be great if these changes were merged into the master branch.

[pmelange]

This PR is dependant on freifunk-berlin/firmware-packages#189 being merged as well.

[SvenRoederer]

I personally don't like this idea.
Beside this it looks like this change will enable the bbbdigger link on all these nodes (https://github.com/freifunk-berlin/firmware-packages/blob/master/addons/freifunk-berlin-bbbdigger/files/postinst.sh#L46). I don't think this is intended

[pmelange]

But the package freifunk-berlin-bbbdigger is not installed on any of the images.

[SvenRoederer]

Ah, got it ...
But does adding it to the "backbone"-image really makes sense? As backbone implies it's a node with real backbone-connectivity, so a backbone-tunnel might not be useful there.

[pmelange]

I feel that the name 'backbone' is an inadequate name for the image. It should be something more like 'expert mode' or 'manual configuration'. I personally have used it for a core router where using the wizard didn't make sense. That same router also connects to the bbbvpn.

[pmelange]

Also, there is at least one node on the backbone which also has a link to the bbb-vpn (mod77uplink.olsr). This could be useful for situations where the link to the real backbone goes down and then the only way to access the node would be through the bbbvpn.

[SvenRoederer]

Using a unique single example of mod77uplink seems not a strong argument.

regarding the naming: I think there is an issue dealing with naming changes. I think now it the right time to change the naming.

[SvenRoederer]

Please check #713 regarding the naming-change. I had a change ready in my branch already.

[SvenRoederer]

can you note like "# Tunneldigger to resume VPN after flashing"

[SvenRoederer]

see my comment for the backbone-image