docs: add v0.4.0-dragonfork CHANGELOG entry (issues #18–#21)

CHANGELOG.md

@@ -1,5 +1,55 @@
 # Datarhei — Dragon Fork
 
+## v0.4.0-dragonfork (2026-05-10)
+
+Protocol polish milestone. Resolves issues #18, #19, #20, #21.
+
+### Added
+
+- **STAP-A IDR detection** (`core/webrtc/keyframecache.go`). The keyframe
+  cache's `isH264IDRStart` now handles all three H.264 RTP packetisation
+  modes: single-NAL (type 5), FU-A start fragment (type 28, start bit +
+  inner type 5), and STAP-A aggregate (type 24, first NAL header at byte 3,
+  inner type 5). Before this fix, an IDR delivered via STAP-A (common from
+  some encoders and relay chains) was not detected, so the cache was never
+  seeded and late-joining WHEP peers still waited a full GOP. Four new tests
+  cover STAP-A with and without truncated payloads. Closes #18.
+
+- **WHEP Link header — RFC 9429 §4.3** (`app/webrtc/handler.go`).
+  `POST /api/v3/whep/{id}` 201 responses now include one
+  `Link: <stun:uri>; rel="ice-server"` header per configured ICE server.
+  `Access-Control-Expose-Headers` updated to include `Link` so browser
+  fetch() can read the header cross-origin. `ICEServerURIs()` accessor added
+  to `Subsystem`. Two new tests verify the header and CORS exposure. Closes
+  #19.
+
+- **WHIP Link header — RFC 9261 §5.2** (`app/webrtc/whip_handler.go`).
+  `POST /api/v3/whip/{id}` 201 responses emit the same ICE server Link
+  headers as WHEP, allowing OBS, GStreamer, and browser-based publishers
+  to discover STUN/TURN without a separate signalling round-trip. Symmetric
+  implementation using the same `ICEServerURIs()` accessor. Closes #21
+  (partial — see also trickle-ICE tests below).
+
+- **Multi-IP NAT1To1** (`core/webrtc/config.go`, `core/webrtc/ice.go`,
+  `app/webrtc/subsystem.go`). `Config` now carries `NAT1To1IPs []string`
+  alongside the legacy `PublicIP string`. `BuildICEConfig` passes the full
+  list to Pion's `SetNAT1To1IPs` when non-empty, falling back to
+  `[]string{PublicIP}` for backward compatibility. `Subsystem.New` builds
+  the merged list: `PublicIP` is prepended (deduplicated) then
+  `NAT1To1IPs` entries follow — enabling dual-homed servers (LAN + public
+  IP) to advertise host candidates on all interfaces simultaneously. Five
+  new tests cover multi-IP, fallback, precedence, and STUN-only mode.
+  Removes the old first-entry-only workaround comment. Closes #20.
+
+- **WHIP handler test suite** (`app/webrtc/whip_handler_test.go`).
+  Nine tests covering: `Publish` 404 on missing ingest, 400 on empty and
+  non-SDP body; `Unpublish` 204 idempotency, 400 on missing resource;
+  `TrickleIngest` 404 on unknown peer, 400 on missing resource; CORS
+  preflight Link/Location/ETag exposure; CORS headers present on error
+  responses. Closes #21 (trickle-ICE test coverage).
+
+---
+
 ## v0.3.0-dragonfork (2026-05-10)
 
 WebRTC ingest (WHIP) milestone. Browsers and OBS can now push a
@@ -107,8 +157,7 @@ Resolves issues #11, #12, #13, #14.
   `ffmpeg_leg_failures_total`, `active_streams`, `active_peers`,
   `udp_ports_in_use`. Closes #11.
 
-- **Grafana observability stack** in `deploy/truenas/core/`:
-  Prometheus v2.55 and Grafana OSS 11.3 containers on a `dragonfork-mon`
+- **Grafana observability stack** in `deploy/truenas/core/`:\n  Prometheus v2.55 and Grafana OSS 11.3 containers on a `dragonfork-mon`
   bridge network reaching Core via `host.docker.internal`. Pre-loaded
   WebRTC Health dashboard (5 rows: WHEP API, ICE, streams/peers, capacity,
   silent-degradation canary). Four pre-loaded Prometheus alert rules.