why Listen "/p2p-circuit"?

[zeigo]

I know Listen returns a listener, and when a relay peer sends STOP to my peer, listener.Accept() gets a conn. So, when will the conn open a stream or accept a stream? Why construct such a conn?

[Stebalien]

Could you expand on that? I'm not sure what you're trying to ask.

[zeigo]

Listening "/p2p-circuit" makes RelayListener.Accept() called. If a relay hop opens a stream for circuit relay to peer B, then sends STOP, B will call handleStopStream, and write a conn to chan incoming. RelayListener.Accept() will read this conn from chan incoming, send a SUCCESS back, and return the conn.
So, why doesn't handleStopStream send SUCCESS directly? What's the conn used for? It seems this issue #28 is about it, but I can't understand it.

[Stebalien]

Ah. The "swarm" calls Accept here. At that point, the swarm will start accepting multiplexed streams off the connection here.

The circuit transport doesn't use the connections directly, it gives them to go-libp2p-swarm.

Note: #28 is a unrelated.

[Stebalien]

FYI, we don't send "SUCCESS" in handleStopStream because we haven't really succeeded until the connection is actually accepted by the swarm.