Could high-bandwidth ORPort-only relays be fallbacks?
In 0.2.8, relays automatically support begindir over ORPort, even if they don't have a DirPort.
I wonder if we're missing out on (m)any high-bandwidth relays by excluding relays without a DirPort. That said, we wouldn't want too many, because relays still use the DirPort to bootstrap off fallbacks. (But if the fallback only has an ORPort, the relay will use that.)
We'd need to make the following changes for this to happen:
- modify the DirPort requirement during fallback selection to check for either a DirPort, or declared begindir support in the descriptor
- make a DirPort optional for configured FallbackDirs in Tor
- this may be as simple as setting the DirPort to 0, and disabling the validation. The rest of the code might just work, because it ignores 0 DirPorts
- test, test, test