Add onlynet=onion config option

[gousasin]

Please add an onlynet=onion configuration option like in Bitcoin Core to exclusively allow connections to Bitmessage nodes behind a Tor Onion Service for enhanced privacy at the network layer.

[sgj3]

Implemented by PR #1545.

[g1itch]

Implemented by PR #1545.

Close but not exact implementation. In the future PR's consider to put closes # in the commit message.

[sgj3]

So, do you want this refactored to use literally "onlynet=onion"?

[gousasin]

I don't really care about the syntax if the functionality is implemented. "onlynet=onion" is used by Bitcoin so I just copied it from there. I leave it up to you.

[sgj3]

OK, understood.

@g1itch What do you think? You left it open and assigned the refactoring label. Is this is what you had in mind?

[sgj3]

@g1itch Bump

[g1itch]

Besides the refactoring there is a new complaint from chan:

If onionservicesonly is enabled and there are no available onion bootstrap servers PyBitmessage will never connect to the network without connecting to bootstrapXXXX.

When onionservicesonly is enabled, the user expects PyBitmessage not to connect non-onion nodes at all. So if onion bootstrap nodes are not to be connected, PyBitmessage should stop bootstrapping and show error message. The user then decides not to use PyBitmessage for a while or to change his policy to connet to non-onion nodes. Security policy is more important than connectivity. ...

If onionservicesonly is enabled and there are no available onion bootstrap servers PyBitmessage will never connect to the network without connecting to bootstrapXXXX. ...

PyBitmessage should not connect to bootstrapXXXX when:

• onionservicesonly is enabled, or
• trusted mode is used. Currently there are no guards for these cases.

Thought it cannot be implemented right now because quzwelsuziwqgpt2.onion (sole onion bootstrap server) is down.