455 lines
16 KiB
Go
455 lines
16 KiB
Go
package webrtc
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import (
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"fmt"
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"io"
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"net/http"
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"strings"
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"sync"
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"sync/atomic"
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"time"
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"github.com/labstack/echo/v4"
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"github.com/pion/webrtc/v4"
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corewebrtc "github.com/datarhei/core/v16/core/webrtc"
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)
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// Default per-stream peer cap when the caller passes 0. The total cap
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// (passed to NewHandler) is enforced separately and takes precedence.
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const defaultMaxPeersPerStream = 8
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// Handler exposes the subsystem's WHEP Echo handlers. Wire them into
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// the /api/v3 group (or a sibling group) via Handler.Register.
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//
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// Lifecycle: peers are tracked in a streamID→resourceID→Peer index.
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// On every Subscribe we spin a tiny goroutine watching the new peer's
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// Done() channel; when ICE fails or Close() runs the index entry is
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// removed and the counters tick back down — no leaks if the browser
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// rage-quits.
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type Handler struct {
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sub *Subsystem
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mu sync.Mutex
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peersByStream map[string]map[string]*corewebrtc.Peer // streamID -> resource -> peer
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peerStream map[string]string // resource -> streamID (reverse index)
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count int64 // atomic
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maxCapTotal int64
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maxCapPerStrm int64
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met *webrtcMetrics
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}
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// NewHandler wraps the subsystem in an Echo-compatible HTTP handler.
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// The maxPeers argument caps concurrent subscribers across all streams;
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// pass 0 to use a generous default (matches corewebrtc.DefaultConfig).
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// The per-stream cap is taken from the corewebrtc default; pass a
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// non-zero value to override via NewHandlerWithCaps.
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func NewHandler(s *Subsystem, maxPeers int) *Handler {
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return NewHandlerWithCaps(s, maxPeers, 0)
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}
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// NewHandlerWithCaps is NewHandler plus an explicit per-stream cap.
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// maxPeersPerStream <= 0 falls back to defaultMaxPeersPerStream.
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func NewHandlerWithCaps(s *Subsystem, maxPeers, maxPeersPerStream int) *Handler {
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total := int64(maxPeers)
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if total <= 0 {
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total = int64(corewebrtc.DefaultConfig().MaxPeersTotal)
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}
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perStream := int64(maxPeersPerStream)
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if perStream <= 0 {
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perStream = defaultMaxPeersPerStream
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}
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h := &Handler{
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sub: s,
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peersByStream: make(map[string]map[string]*corewebrtc.Peer),
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peerStream: make(map[string]string),
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maxCapTotal: total,
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maxCapPerStrm: perStream,
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}
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// Subsystem broadcasts process-stop via this hook so the handler
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// can yank stale peer entries before their Sources close out
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// from underneath them.
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if s != nil {
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s.SetTeardownHook(h.tearDownStreamPeers)
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}
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return h
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}
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// Register mounts the WHEP routes on the provided Echo group.
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//
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// CORS preflights are answered on every WHEP path; regular WHEP
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// responses also carry the Access-Control-* headers so browser-side
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// players living on a different origin can subscribe.
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func (h *Handler) Register(g *echo.Group) {
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g.OPTIONS("/whep/:id", h.preflight)
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g.OPTIONS("/whep/:id/:resource", h.preflight)
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g.POST("/whep/:id", h.Subscribe)
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g.DELETE("/whep/:id/:resource", h.Unsubscribe)
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g.PATCH("/whep/:id/:resource", h.Trickle)
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}
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// Subscribe handles POST /whep/:id. Request body is an SDP offer,
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// response is an SDP answer with a Location header pointing at the
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// DELETE/PATCH resource.
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//
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// @Summary Subscribe to a WebRTC stream via WHEP
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// @Description Subscribe to a process's WebRTC egress stream. Body is the SDP offer (Content-Type: application/sdp). Response is the SDP answer; the Location header points at the DELETE/PATCH resource for teardown and trickle ICE.
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// @Tags v16.16.0
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// @ID webrtc-3-whep-subscribe
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// @Accept application/sdp
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// @Produce application/sdp
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// @Param id path string true "Process ID with config.webrtc.enabled=true"
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// @Success 201 {string} string "SDP answer"
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// @Failure 400 {string} string "missing stream id, malformed body, or invalid SDP"
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// @Failure 404 {string} string "no stream registered for this process id"
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// @Failure 406 {string} string "offer SDP missing required H264 / Opus rtpmap"
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// @Failure 503 {string} string "peer cap reached (per-stream or total)"
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// @Failure 504 {string} string "ICE gathering timeout"
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// @Security ApiKeyAuth
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// @Router /api/v3/whep/{id} [post]
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func (h *Handler) Subscribe(c echo.Context) error {
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addCORS(c)
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t0 := time.Now()
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id := c.Param("id")
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if id == "" {
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h.recordRequest("subscribe", "", http.StatusBadRequest, t0)
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return c.String(http.StatusBadRequest, "missing stream id")
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}
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// Total cap: cheap atomic check before doing real work.
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if atomic.LoadInt64(&h.count) >= h.maxCapTotal {
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if h.met != nil {
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h.met.capRejections.WithLabelValues("", "global").Inc()
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}
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h.recordRequest("subscribe", id, http.StatusServiceUnavailable, t0)
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return c.String(http.StatusServiceUnavailable, corewebrtc.ErrPeerCapReached.Error())
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}
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stream, ok := h.sub.lookup(id)
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if !ok {
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h.recordRequest("subscribe", id, http.StatusNotFound, t0)
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return c.String(http.StatusNotFound, corewebrtc.ErrStreamNotFound.Error())
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}
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// Per-stream cap: needs the lock since we're indexing per stream.
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h.mu.Lock()
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if int64(len(h.peersByStream[id])) >= h.maxCapPerStrm {
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h.mu.Unlock()
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if h.met != nil {
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h.met.capRejections.WithLabelValues(id, "stream").Inc()
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}
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h.recordRequest("subscribe", id, http.StatusServiceUnavailable, t0)
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return c.String(http.StatusServiceUnavailable, "webrtc: per-stream peer cap reached")
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}
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h.mu.Unlock()
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body, err := io.ReadAll(c.Request().Body)
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if err != nil {
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h.recordRequest("subscribe", id, http.StatusBadRequest, t0)
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return c.String(http.StatusBadRequest, "read body: "+err.Error())
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}
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if len(body) == 0 || !strings.HasPrefix(string(body), "v=") {
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h.recordRequest("subscribe", id, http.StatusBadRequest, t0)
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return c.String(http.StatusBadRequest, corewebrtc.ErrInvalidSDP.Error())
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}
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if err := requireH264AndOpus(string(body)); err != nil {
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if h.met != nil {
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if cme, ok2 := err.(*codecMismatchError); ok2 {
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for _, kind := range cme.missing {
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h.met.codecMismatches.WithLabelValues(id, strings.ToLower(kind)).Inc()
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}
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}
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}
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h.recordRequest("subscribe", id, http.StatusNotAcceptable, t0)
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return c.String(http.StatusNotAcceptable, err.Error())
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}
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offer := webrtc.SessionDescription{Type: webrtc.SDPTypeOffer, SDP: string(body)}
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peer, err := h.sub.factory.CreatePeerFromSources(c.Request().Context(), stream.video, stream.audio, offer)
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if err != nil {
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// Surface the design's error matrix.
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switch err {
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case corewebrtc.ErrICETimeout:
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h.recordRequest("subscribe", id, http.StatusGatewayTimeout, t0)
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return c.String(http.StatusGatewayTimeout, err.Error())
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case corewebrtc.ErrCodecMismatch:
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h.recordRequest("subscribe", id, http.StatusNotAcceptable, t0)
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return c.String(http.StatusNotAcceptable, err.Error())
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default:
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h.recordRequest("subscribe", id, http.StatusInternalServerError, t0)
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return c.String(http.StatusInternalServerError, "create peer: "+err.Error())
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}
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}
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rid := peer.ResourceID()
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h.mu.Lock()
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if h.peersByStream[id] == nil {
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h.peersByStream[id] = make(map[string]*corewebrtc.Peer)
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}
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h.peersByStream[id][rid] = peer
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h.peerStream[rid] = id
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h.mu.Unlock()
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atomic.AddInt64(&h.count, 1)
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// Auto-cleanup: when Pion's OnConnectionStateChange triggers
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// peer.Close() (ICE failed/disconnected), the Done channel
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// closes and we yank the index entry. Without this the map
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// leaks for the lifetime of the handler.
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go h.awaitPeerClose(rid, peer)
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// Track ICE establishment duration asynchronously.
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go h.trackICE(id, peer, time.Now())
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h.recordRequest("subscribe", id, http.StatusCreated, t0)
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// RFC 9429 §4.3: emit one Link header per configured ICE server so
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// that the browser can discover STUN/TURN without a separate
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// signalling round-trip.
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for _, uri := range h.sub.ICEServerURIs() {
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c.Response().Header().Add("Link", "<"+uri+">; rel=\"ice-server\"")
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}
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c.Response().Header().Set("Content-Type", "application/sdp")
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c.Response().Header().Set("Location", "/whep/"+id+"/"+rid)
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c.Response().Header().Set("ETag", `"`+rid+`"`)
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return c.String(http.StatusCreated, peer.Answer().SDP)
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}
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// Unsubscribe handles DELETE /whep/:id/:resource. Per WHEP spec we
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// return 204 even when the resource is unknown — DELETE is idempotent
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// and a re-issued tear-down should never error out.
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//
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// @Summary Tear down a WHEP subscription
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// @Description Idempotent peer teardown by resource id (returned in the Location header by Subscribe). Returns 204 even when the resource is unknown, per the WHEP spec.
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// @Tags v16.16.0
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// @ID webrtc-3-whep-unsubscribe
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// @Param id path string true "Process ID"
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// @Param resource path string true "Resource ID from the Subscribe Location header"
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// @Success 204 "no content"
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// @Failure 400 {string} string "missing resource id"
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// @Security ApiKeyAuth
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// @Router /api/v3/whep/{id}/{resource} [delete]
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func (h *Handler) Unsubscribe(c echo.Context) error {
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addCORS(c)
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t0 := time.Now()
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resource := c.Param("resource")
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if resource == "" {
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h.recordRequest("unsubscribe", "", http.StatusBadRequest, t0)
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return c.String(http.StatusBadRequest, "missing resource id")
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}
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h.mu.Lock()
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streamID := h.peerStream[resource]
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var peer *corewebrtc.Peer
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if streamID != "" {
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peer = h.peersByStream[streamID][resource]
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delete(h.peersByStream[streamID], resource)
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if len(h.peersByStream[streamID]) == 0 {
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delete(h.peersByStream, streamID)
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}
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delete(h.peerStream, resource)
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}
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h.mu.Unlock()
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if peer != nil {
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_ = peer.Close()
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}
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if streamID != "" {
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atomic.AddInt64(&h.count, -1)
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}
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h.recordRequest("unsubscribe", streamID, http.StatusNoContent, t0)
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return c.NoContent(http.StatusNoContent)
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}
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// Trickle handles PATCH /whep/:id/:resource — adds ICE candidates
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// from a trickle-ice-sdpfrag body. Empty body is a no-op (clients
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// signal end-of-candidates via an a=end-of-candidates line, which
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// AddICECandidate accepts).
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//
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// @Summary Trickle ICE candidates for a WHEP subscription
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// @Description Add ICE candidates to an existing WebRTC peer. Body is application/trickle-ice-sdpfrag.
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// @Tags v16.16.0
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// @ID webrtc-3-whep-trickle
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// @Accept application/trickle-ice-sdpfrag
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// @Param id path string true "Process ID"
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// @Param resource path string true "Resource ID from the Subscribe Location header"
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// @Success 204 "no content"
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// @Failure 400 {string} string "missing resource id or unreadable body"
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// @Failure 404 {string} string "peer not found"
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// @Security ApiKeyAuth
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// @Router /api/v3/whep/{id}/{resource} [patch]
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func (h *Handler) Trickle(c echo.Context) error {
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addCORS(c)
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t0 := time.Now()
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resource := c.Param("resource")
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if resource == "" {
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h.recordRequest("trickle", "", http.StatusBadRequest, t0)
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return c.String(http.StatusBadRequest, "missing resource id")
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}
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h.mu.Lock()
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streamID := h.peerStream[resource]
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var peer *corewebrtc.Peer
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if streamID != "" {
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peer = h.peersByStream[streamID][resource]
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}
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h.mu.Unlock()
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if peer == nil {
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h.recordRequest("trickle", streamID, http.StatusNotFound, t0)
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return c.NoContent(http.StatusNotFound)
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}
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body, err := io.ReadAll(c.Request().Body)
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if err != nil {
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h.recordRequest("trickle", streamID, http.StatusBadRequest, t0)
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return c.String(http.StatusBadRequest, "read body: "+err.Error())
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}
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for _, line := range strings.Split(string(body), "\n") {
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line = strings.TrimSpace(line)
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if !strings.HasPrefix(line, "a=candidate:") {
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continue
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}
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cand := strings.TrimPrefix(line, "a=")
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_ = peer.AddICECandidate(webrtc.ICECandidateInit{Candidate: cand})
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}
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h.recordRequest("trickle", streamID, http.StatusNoContent, t0)
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return c.NoContent(http.StatusNoContent)
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}
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// recordRequest records whepRequests counter and whepRequestDuration histogram
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// for any WHEP route outcome. Silently no-ops if metrics are not initialised.
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func (h *Handler) recordRequest(route, streamID string, code int, t0 time.Time) {
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if h.met == nil {
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return
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}
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codeStr := fmt.Sprintf("%d", code)
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h.met.whepRequests.WithLabelValues(route, codeStr, streamID).Inc()
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h.met.whepRequestDuration.WithLabelValues(route, streamID).Observe(time.Since(t0).Seconds())
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}
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// preflight answers a CORS OPTIONS request; the headers are also
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// echoed on every other response.
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func (h *Handler) preflight(c echo.Context) error {
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addCORS(c)
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return c.NoContent(http.StatusNoContent)
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}
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// Close tears down every active peer (e.g., during Core shutdown).
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func (h *Handler) Close() {
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h.mu.Lock()
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peers := make([]*corewebrtc.Peer, 0)
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for _, m := range h.peersByStream {
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for _, p := range m {
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peers = append(peers, p)
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}
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}
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h.peersByStream = make(map[string]map[string]*corewebrtc.Peer)
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h.peerStream = make(map[string]string)
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h.mu.Unlock()
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for _, p := range peers {
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if p != nil {
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_ = p.Close()
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}
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}
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atomic.StoreInt64(&h.count, 0)
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}
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// awaitPeerClose blocks on peer.Done() and yanks the index entry when
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// the peer self-closes (ICE failed/disconnected). Idempotent with
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// the Unsubscribe path: if Unsubscribe ran first the index is already
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// empty and we just decrement the counter once on first arrival.
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func (h *Handler) awaitPeerClose(resource string, peer *corewebrtc.Peer) {
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<-peer.Done()
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h.mu.Lock()
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streamID := h.peerStream[resource]
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_, present := h.peerStream[resource]
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if present {
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delete(h.peerStream, resource)
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if streamID != "" {
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delete(h.peersByStream[streamID], resource)
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if len(h.peersByStream[streamID]) == 0 {
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delete(h.peersByStream, streamID)
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}
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}
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}
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h.mu.Unlock()
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if present {
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atomic.AddInt64(&h.count, -1)
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}
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}
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// tearDownStreamPeers is the callback the Subsystem runs in its
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// onProcessStop hook. It closes every peer subscribed to that
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// stream and records FFmpeg leg failures if any peers were active,
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// which indicates the process died unexpectedly.
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func (h *Handler) tearDownStreamPeers(streamID string) {
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h.mu.Lock()
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bucket := h.peersByStream[streamID]
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hadPeers := len(bucket) > 0
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peers := make([]*corewebrtc.Peer, 0, len(bucket))
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for _, p := range bucket {
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peers = append(peers, p)
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}
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h.mu.Unlock()
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for _, p := range peers {
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if p != nil {
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_ = p.Close()
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}
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}
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if hadPeers && h.met != nil {
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h.met.ffmpegLegFailures.WithLabelValues(streamID, "video").Inc()
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h.met.ffmpegLegFailures.WithLabelValues(streamID, "audio").Inc()
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}
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}
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// addCORS emits the response headers a browser-side WHEP player
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// expects. WHEP's Location, ETag, and Link headers must be exposed
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// for fetch() to read them across origins. Link carries the ICE
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// server URIs per RFC 9429 §4.3.
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func addCORS(c echo.Context) {
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hh := c.Response().Header()
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hh.Set("Access-Control-Allow-Origin", "*")
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hh.Set("Access-Control-Allow-Methods", "POST, DELETE, PATCH, OPTIONS")
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hh.Set("Access-Control-Allow-Headers", "Content-Type, Authorization, If-Match, If-None-Match")
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hh.Set("Access-Control-Expose-Headers", "Location, ETag, Link")
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}
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// requireH264AndOpus does a coarse SDP scan to confirm the offer
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// includes both an H.264 video rtpmap and an Opus audio rtpmap. The
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// design treats codec mismatch as a 406, never a silent black frame.
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//
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// This is intentionally a string scan rather than a full SDP parse:
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// every modern browser advertises H.264 and Opus by name, and a
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// dependency on a real SDP parser for one validation step is
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// disproportionate. M4 may swap this for pion/sdp.v3 when other
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// surfaces also need parsing.
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func requireH264AndOpus(sdp string) error {
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lower := strings.ToLower(sdp)
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hasH264 := strings.Contains(lower, "h264/90000") || strings.Contains(lower, " h264/")
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hasOpus := strings.Contains(lower, "opus/48000") || strings.Contains(lower, " opus/")
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if hasH264 && hasOpus {
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return nil
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}
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missing := []string{}
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if !hasH264 {
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missing = append(missing, "H264")
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}
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if !hasOpus {
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missing = append(missing, "Opus")
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}
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return &codecMismatchError{missing: missing}
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}
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type codecMismatchError struct{ missing []string }
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func (e *codecMismatchError) Error() string {
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return "webrtc: codec mismatch — offer is missing: " + strings.Join(e.missing, ", ")
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}
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