auto-relay: automatically make reservations on relays as we discover them

[thomaseizinger]

Description

Today, a user of rust-libp2p can make a reservation on a relay by instructing the Swarm to listen_on a relayed address, i.e. one with /p2p-circuit in it.

We should develop a module similar to go-libp2ps AutoRelay that does this automatically as we connect to relays:

• Upon a new connection, check the supported protocols on that connection for the relay "hop" protocol.
• Based on some configuration (to be decided), conclude that we should make a new reservation.
• Emit a ToSwarm::ListenOn command with a constructed /p2p-circuit address for the discovered relay.

Motivation

Give users a module they can drop into their Behaviour that automatically creates reservations as we connect to relays.

Requirements

1. The number of reservations we make must be bounded by something, i.e. maximum 10. Should probably be configurable.
2. We may want to make this conditional on our number of external addresses. If we don't have any external addresses, reservations will be useful because it means we are likely behind a NAT.

Open questions

No response

Are you planning to do it yourself in a pull request ?

No

[dariusc93]

If this is to be automatic, I wonder if we should check the external addresses for any public addresses that isnt a relay circuit (either reported by upnp, autonat or some behaviour emitting the external address event) and either disconnect from the relays (could be configurable to stay connected?), or if the behaviour havent made a reservation to cancel or block any attempts.

[thomaseizinger]

If this is to be automatic, I wonder if we should check the external addresses for any public addresses that isnt a relay circuit (either reported by upnp, autonat or some behaviour emitting the external address event) and either disconnect from the relays (could be configurable to stay connected?), or if the behaviour havent made a reservation to cancel or block any attempts.

Yeah, this is what I meant with:

2. We may want to make this conditional on our number of external addresses. If we don't have any external addresses, reservations will be useful because it means we are likely behind a NAT.

We can easily track how many external address we have using ExternalAddresses. I think it is a good default to free up resources on relays if they are not needed.

[dariusc93]

I may be interested in tackling this if nobody else does (also as time permits), but just as a question: Should this be apart of the current relay protocol or should this be its own crate?

[thomaseizinger]

should this be its own crate?

We can implement this as its own module which I think might be cleaner. There is a fair bit of state tracking involved and the relay code is already quite complex so I think it is best to be separate.

[Techno-Fox]

I just want to know. Has there been any updates on this?

[dariusc93]

Hey @Techno-Fox! I did start on it a bit last year but been busy. I may pick up on it in the next few weeks but if you (or anybody else) would like to start on it you are more than welcome :)

[Techno-Fox]

what did you want to change and or add to your version?

[silkroadnomad]

I'd need such right now.