webrtc ~master

webrtc (D)

A WebRTC data-channel engine for D — the transport stack libp2p's webrtc-direct needs: ICE → DTLS → SCTP → DCEP, assembled into a single PeerConnection.

It is a faithful, AI-generated laundry of webrtc-rs's sans-io rewrite rtc: pure state machines, no async runtime baked in. You feed it inbound UDP datagrams and drain outbound ones; it never touches a socket or a clock. That means it drops into any I/O loop (vibe-core, in libp2p-dlang) without a competing reactor.

Everything below UDP and above the data channel is handled internally, so a caller deals only in datagrams and messages:

DataChannels (DCEP)      application messages
SCTP association         reliable, multiplexed streams — runs *inside* DTLS
DTLS 1.2                 encryption + certificate-fingerprint pinning
ICE agent                connectivity over UDP host candidates (STUN)
UDP                      the caller's socket

Crypto

Per the project rule libsodium → Deimos(OpenSSL) → hand-port:

• libsodium for the primitives it provides (SHA-256, HMAC building blocks, randomness) used by STUN and SCTP.
• OpenSSL via `deimos.openssl` for DTLS 1.2, the self-signed ECDSA P-256 certificate, and its X.509/SHA-256 fingerprint (the a=fingerprint / libp2p /certhash). DTLS is not laundered from rtc-dtls — where a Deimos binding exists, we use it.

Layout

Only the webrtc-direct path is ported. TURN, mDNS, srflx/relay candidates, ICE-TCP, media (RTP/RTCP/SRTP), ICE role-conflict switching and keepalive are deliberately dropped.

Usage sketch

import webrtc.connection;

// Roles follow libp2p webrtc-direct: dialer = ICE-controlling / DTLS-client /
// SCTP-client; listener is the mirror.
auto pc = new PeerConnection(Perspective.dialer, localIceCreds, tieBreaker,
    Certificate.generate());
pc.addLocalCandidate(host("1.2.3.4", 40000));
pc.setRemoteIce(remoteIceCreds, host("5.6.7.8", 50000));

// Sans-io: pump datagrams from/to your UDP socket.
foreach (dg; pc.gatherOutbound(nowMs)) socket.sendTo(dg.data, dg.dst);
pc.handleDatagram(received, from, to, nowMs);

// Once pc.isReady(), open and use a data channel.
auto sid = pc.channels.open(DataChannelConfig("chat", "proto"));
pc.channels.send(sid, cast(ubyte[]) "hello".dup, /*isString*/ true);

peerFingerprint() exposes the peer's certhash for multiaddr verification.

Status

The engine is complete and verified end to end — over an in-memory datagram pump, two PeerConnections bring up ICE + DTLS + SCTP, pin certificate fingerprints, and carry data-channel messages both ways across the whole stack.

Deferred (loss-recovery only — the loss-free path is complete): SCTP fast-retransmit, T3-rtx timer-driven retransmission, PR-SCTP forward-TSN, stream reset/reconfig, and shutdown.

Test

dub run -c ut     # unit-threaded + fluent-asserts (68 tests)

Ground truth for the laundry: the rtc-* crates at webrtc-rs/rtc. Every ported piece has a D parity test against its rust counterpart.

License

MIT — see LICENSE.