go2rtc/cmd/webrtc/webrtc.go

package webrtc

import (
	"encoding/json"
	"errors"
	"github.com/AlexxIT/go2rtc/cmd/api"
	"github.com/AlexxIT/go2rtc/cmd/app"
	"github.com/AlexxIT/go2rtc/cmd/streams"
	"github.com/AlexxIT/go2rtc/pkg/webrtc"
	pion "github.com/pion/webrtc/v3"
	"github.com/rs/zerolog"
	"io"
	"mime"
	"net"
	"net/http"
)

func Init() {
	var cfg struct {
		Mod struct {
			Listen     string           `yaml:"listen"`
			Candidates []string         `yaml:"candidates"`
			IceServers []pion.ICEServer `yaml:"ice_servers"`
		} `yaml:"webrtc"`
	}

	cfg.Mod.Listen = ":8555"
	cfg.Mod.IceServers = []pion.ICEServer{
		{URLs: []string{"stun:stun.l.google.com:19302"}},
	}

	app.LoadConfig(&cfg)

	log = app.GetLogger("webrtc")

	address := cfg.Mod.Listen

	// create pionAPI with custom codecs list and custom network settings
	pionAPI, err := webrtc.NewAPI(address)
	if pionAPI == nil {
		log.Error().Err(err).Caller().Send()
		return
	}

	if err != nil {
		log.Warn().Err(err).Caller().Send()
	} else if address != "" {
		log.Info().Str("addr", address).Msg("[webrtc] listen")
		_, Port, _ = net.SplitHostPort(address)
	}

	pionConf := pion.Configuration{
		ICEServers:   cfg.Mod.IceServers,
		SDPSemantics: pion.SDPSemanticsUnifiedPlanWithFallback,
	}

	newPeerConnection = func() (*pion.PeerConnection, error) {
		return pionAPI.NewPeerConnection(pionConf)
	}

	for _, candidate := range cfg.Mod.Candidates {
		AddCandidate(candidate)
	}

	api.HandleWS("webrtc", asyncHandler)
	api.HandleWS("webrtc/offer", asyncHandler)
	api.HandleWS("webrtc/candidate", candidateHandler)

	api.HandleFunc("api/webrtc", syncHandler)
}

var Port string
var log zerolog.Logger

var newPeerConnection func() (*pion.PeerConnection, error)

func asyncHandler(tr *api.Transport, msg *api.Message) error {
	src := tr.Request.URL.Query().Get("src")
	stream := streams.GetOrNew(src)
	if stream == nil {
		return errors.New(api.StreamNotFound)
	}

	log.Debug().Str("url", src).Msg("[webrtc] new consumer")

	// create new PeerConnection instance
	pc, err := newPeerConnection()
	if err != nil {
		log.Error().Err(err).Caller().Send()
		return err
	}

	// apiV2 - json/object exchange, V2 - raw SDP and raw Candidates exchange
	apiV2 := msg.Type == "webrtc"

	cons := webrtc.NewServer(pc)
	cons.UserAgent = tr.Request.UserAgent()
	cons.Listen(func(msg any) {
		switch msg := msg.(type) {
		case pion.PeerConnectionState:
			if msg == pion.PeerConnectionStateClosed {
				stream.RemoveConsumer(cons)
			}
		case *pion.ICECandidate:
			if msg != nil {
				s := msg.ToJSON().Candidate
				log.Trace().Str("candidate", s).Msg("[webrtc] local")
				tr.Write(&api.Message{Type: "webrtc/candidate", Value: s})
			}
		}
	})

	// 1. SetOffer, so we can get remote client codecs
	var offer string
	if apiV2 {
		offer = msg.GetString("sdp")
	} else {
		offer = msg.String()
	}

	log.Trace().Msgf("[webrtc] offer:\n%s", offer)

	if err = cons.SetOffer(offer); err != nil {
		log.Warn().Err(err).Caller().Send()
		return err
	}

	// 2. AddConsumer, so we get new tracks
	if err = stream.AddConsumer(cons); err != nil {
		log.Debug().Err(err).Msg("[webrtc] add consumer")
		_ = cons.Close()
		return err
	}

	// 3. Exchange SDP without waiting all candidates
	answer, err := cons.GetAnswer()
	log.Trace().Msgf("[webrtc] answer\n%s", answer)

	if err != nil {
		log.Error().Err(err).Caller().Send()
		return err
	}

	tr.Consumer = cons

	tr.Write(&api.Message{Type: "webrtc/answer", Value: answer})

	asyncCandidates(tr)

	return nil
}

// syncHandler
func syncHandler(w http.ResponseWriter, r *http.Request) {
	url := r.URL.Query().Get("src")
	stream := streams.Get(url)
	if stream == nil {
		return
	}

	ct := r.Header.Get("Content-Type")
	if ct != "" {
		ct, _, _ = mime.ParseMediaType(ct)
	}

	// apiV2 - json/object exchange, V1 - raw SDP exchange
	apiV2 := ct == "application/json"

	var offer string
	if apiV2 {
		var sd pion.SessionDescription
		if err := json.NewDecoder(r.Body).Decode(&sd); err != nil {
			log.Error().Err(err).Caller().Send()
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		offer = sd.SDP
	} else {
		body, err := io.ReadAll(r.Body)
		if err != nil {
			log.Error().Err(err).Caller().Send()
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		offer = string(body)
	}

	answer, err := ExchangeSDP(stream, offer, r.UserAgent())
	if err != nil {
		log.Error().Err(err).Caller().Send()
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// send SDP to client
	if apiV2 {
		w.Header().Set("Content-Type", ct)

		v := pion.SessionDescription{
			Type: pion.SDPTypeAnswer, SDP: answer,
		}
		if err = json.NewEncoder(w).Encode(v); err != nil {
			log.Error().Err(err).Caller().Send()
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}
	} else {
		if _, err = w.Write([]byte(answer)); err != nil {
			log.Error().Err(err).Caller().Send()
		}
	}
}

func ExchangeSDP(stream *streams.Stream, offer string, userAgent string) (answer string, err error) {
	pc, err := newPeerConnection()
	if err != nil {
		log.Error().Err(err).Caller().Msg("NewPConn")
		return
	}

	// create new webrtc instance
	conn := webrtc.NewServer(pc)
	conn.UserAgent = userAgent
	conn.Listen(func(msg interface{}) {
		switch msg := msg.(type) {
		case pion.PeerConnectionState:
			if msg == pion.PeerConnectionStateClosed {
				stream.RemoveConsumer(conn)
			}
		}
	})

	// 1. SetOffer, so we can get remote client codecs
	log.Trace().Msgf("[webrtc] offer:\n%s", offer)

	if err = conn.SetOffer(offer); err != nil {
		log.Warn().Err(err).Caller().Msg("conn.SetOffer")
		return
	}

	// 2. AddConsumer, so we get new tracks
	if err = stream.AddConsumer(conn); err != nil {
		log.Warn().Err(err).Caller().Msg("stream.AddConsumer")
		_ = conn.Close()
		return
	}

	// exchange sdp without waiting all candidates
	//answer, err := conn.ExchangeSDP(offer, false)
	answer, err = conn.GetCompleteAnswer()
	if err == nil {
		answer, err = syncCanditates(answer)
	}
	log.Trace().Msgf("[webrtc] answer\n%s", answer)

	if err != nil {
		log.Error().Err(err).Caller().Msg("conn.GetCompleteAnswer")
	}

	return
}