core: add useful logs to OrTransport when trying addresses

[thomaseizinger]

Description

Currently, there are no logs when OrTransport tries an address on several transports:

rust-libp2p/core/src/transport/choice.rs

Lines 49 to 89 in 14530af

	fn listen_on(
	&mut self,
	id: ListenerId,
	addr: Multiaddr,
	) -> Result<(), TransportError<Self::Error>> {
	let addr = match self.0.listen_on(id, addr) {
	Err(TransportError::MultiaddrNotSupported(addr)) => addr,
	res => return res.map_err(|err| err.map(Either::Left)),
	};
	let addr = match self.1.listen_on(id, addr) {
	Err(TransportError::MultiaddrNotSupported(addr)) => addr,
	res => return res.map_err(|err| err.map(Either::Right)),
	};
	Err(TransportError::MultiaddrNotSupported(addr))
	}
	fn remove_listener(&mut self, id: ListenerId) -> bool {
	self.0.remove_listener(id) || self.1.remove_listener(id)
	}
	fn dial(&mut self, addr: Multiaddr) -> Result<Self::Dial, TransportError<Self::Error>> {
	let addr = match self.0.dial(addr) {
	Ok(connec) => return Ok(EitherFuture::First(connec)),
	Err(TransportError::MultiaddrNotSupported(addr)) => addr,
	Err(TransportError::Other(err)) => {
	return Err(TransportError::Other(Either::Left(err)))
	}
	};
	let addr = match self.1.dial(addr) {
	Ok(connec) => return Ok(EitherFuture::Second(connec)),
	Err(TransportError::MultiaddrNotSupported(addr)) => addr,
	Err(TransportError::Other(err)) => {
	return Err(TransportError::Other(Either::Right(err)))
	}
	};
	Err(TransportError::MultiaddrNotSupported(addr))
	}

We should change that to make these cases easier to debug.

Open questions

• How to best log the name of the transport? Could use https://doc.rust-lang.org/std/any/fn.type_name.html but that can get very verbose.

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

No.