Unable to open subsequent data channels if the WebRTC Direct initial handshake channel has been closed

Summary

The WebRTC Direct spec says:

On success of the authentication handshake, the used datachannel is closed and the plain WebRTC connection is used with its multiplexing capabilities via datachannels.

https://github.com/libp2p/specs/blob/master/webrtc/webrtc-direct.md#connection-security

At the moment the js-libp2p implementation does not close the handshake datachannel, leaving it open for the duration of the connection.

Given that the final data read from the channel during the noise handshake is done by the client, it would be the one to close the connection.

I am trying to update the js-libp2p implementation to close the handshake datachannel as per the spec but if I do, the transport interop tests start to fail against rust-libp2p with Chrome/Firefox/WebKit being the diallers (go & Node.js work fine).

From what I can see, after the handshake channel has been closed, opening the subsequent outbound channel to send the ping message never completes.

Inbound datachannels are still opened correctly as I can see from the logs that rust-libp2p pings js-libp2p during the test.

I believe @sukunrt observed something similar with rust-libp2p while working on go-libp2p, though he elected to just not close the handshake datachannel.

rust-libp2p logs from the test run in Docker are pasted below.

Expected behavior

Outbound datachannels should open correctly after the initial handshake datachannel has been closed.

Actual behavior

Outbound datachannels fail to open after the initial handshake datachannel has been closed.

Relevant log output

Logs from the Docker test run are below (GitHub complains it's too long to be pasted here).

Possible Solution

No response

Version

0.54

Would you like to work on fixing this bug?

I'd like some help resolving it

Start with the transport interop tests and the Rust WebRTC Direct handshake/datachannel lifecycle described in the issue, comparing behavior with js-libp2p. Reproduce the Chrome, Firefox, and WebKit dialler cases with the initial handshake channel closed; done means subsequent outbound datachannels open and the interop tests pass.