webrtc/: Add libp2p WebRTC browser-to-server spec

[mxinden]

This pull requests summarizes the status quo of the ongoing WebRTC in libp2p work. In other words, it represents the summary of all past discussions like #220.

While describing both the browser-to-server and browser-to-browser use-case, priority is on the former. Once the browser-to-server use-case is sufficiently specified, I will remove the browser-to-browser use-case, merge this pull request, and start iteration two, namely to sufficiently specify the browser-to-browser use-case.

Remaining work items for browser-to-server:

• Specification
  • Server to start Noise handshake webrtc/: Add libp2p WebRTC browser-to-server spec #412 (comment)
  • Head of line blocking webrtc/: Add libp2p WebRTC browser-to-server spec #412 (comment)
  • RTCDataChannel ID negotiation webrtc/: Add libp2p WebRTC browser-to-server spec #412 (comment)
  • RTCDataChannel ID reuse webrtc/: Add libp2p WebRTC browser-to-server spec #412 (comment)
  • Fixing fingerprint hash algorithm to sha-256 webrtc/: Add libp2p WebRTC browser-to-server spec #412 (comment)
  • Document potential deprecation of WebRTC Star and WebRTC Direct once browser-to-browser support is specified
  • Fingerprint sorting webrtc/: Add libp2p WebRTC browser-to-server spec #412 (comment)
  • Document label on RTCConnection.createDataChannel. https://github.com/libp2p/specs/pull/412/files#r995877508
  • Communicate message size limit in SDP webrtc/: Add libp2p WebRTC browser-to-server spec #412 (comment)
• Implementations of this specification
  • JS WebRTC: Browser to Server js-libp2p#1478
  • Go webrtc: add WebRTC transport go-libp2p#1655
  • Rust feat: Add WebRTC transport rust-libp2p#2622
    • Message framing transports/webrtc: Implement message framing melekes/rust-libp2p#10
    • Use Noise prologue libp2p/rust-libp2p@7e630a6
• Testing via Testground
  • EPIC: implement Javascript & Browser support in Testground testground/testground#1386
  • Feat/1386 browser hello world test testground/testground#1474

[ckousik]

Perhaps we should also say that a=max-message-size:16384 SDP attribute should be set to the maximum frame size (16kB). By default, it's 64kB (see https://datatracker.ietf.org/doc/rfc8841/), but it might be a good idea to align these two variables. Wdyt? The alternative is to not include attribute in SDP and allow messages up to 64kB.

That sounds good to me @melekes. @ckousik @John-LittleBearLabs any objections?

No objections from my end.

[mxinden]

@marten-seemann thank you for your review. I addressed all your comments.

I followed both of your major suggestions.

1. Inferring hash algorithm from multiaddr for easier role out of new hash algorithm. [webrtc/: Add libp2p WebRTC browser-to-server spec #412 (comment)](https://github.com/libp2p/specs/pull/412#discussion_r999745879)

2. Prefixing ufrag to ease general future upgrade mechanism via ufrag. [webrtc/: Add libp2p WebRTC browser-to-server spec #412 (comment)](https://github.com/libp2p/specs/pull/412#discussion_r999768836)

Would you mind taking another look?

Friendly ping @marten-seemann. Does this look good to you?

[tomaka]

I understand that you're being over cautious with clicking the merge button, but can we now consider that this version of the spec is "final", in the sense that the logic isn't going to change before merging, and the only things that could change are possible clarifications of the language?
I'd like to start releasing versions that "officially" support this spec.

[mxinden]

Quite a long journey. 475 (+1) comments and 135 commits, 14 reviewers, ...

I am merging here as a Working Draft. We can promote it once we have a released implementation.

A couple of shoutouts:

• @ckousik and the Little Bear Labs folks providing all your WebRTC knowledge.
• @melekes for all your input from the Rust side. Thanks for bearing with us throughout the process.
• @Menduist and @s1fr0 for your input on the Noise handshake, especially proposing the Noise prologue mechanism!
• @thomaseizinger filling the many gaps, thinking deep into the stream semantics introduced here.
• @marten-seemann for the high-quality comments across the specification.
• ...

Up next: browser-to-browser use-case.

[tomaka]

Shoutout to me for having started the whole thing before it was aggressively taken over and not receiving a shoutout

[marcus-pousette]

I am working a project that heavily relies on the libp2p-js impl. I am currently working towards enabling a huge amount of dapps that benefit greatly from WebRTC. What I am missing (?) currently is a way for having js WebRTC listeners. Now it seems to only be supported/to-be-supported for the the Go and Rust impl. Correct me if I have understood the spec. incorrectly, but is this something that is planned for? Or not?

[MarcoPolo]

Follow #497