install go2rtc on bob

installs_on_host/go2rtc/pkg/srtp/server.go

@@ -0,0 +1,102 @@
+package srtp
+
+import (
+	"encoding/binary"
+	"net"
+	"strconv"
+	"sync"
+)
+
+type Server struct {
+	address  string
+	conn     net.PacketConn
+	sessions map[uint32]*Session
+	mu       sync.Mutex
+}
+
+func NewServer(address string) *Server {
+	return &Server{
+		address:  address,
+		sessions: map[uint32]*Session{},
+	}
+}
+
+func (s *Server) Port() int {
+	if s.conn != nil {
+		return s.conn.LocalAddr().(*net.UDPAddr).Port
+	}
+
+	_, a, _ := net.SplitHostPort(s.address)
+	i, _ := strconv.Atoi(a)
+	return i
+}
+
+func (s *Server) AddSession(session *Session) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if err := session.init(); err != nil {
+		return
+	}
+
+	if len(s.sessions) == 0 {
+		var err error
+		if s.conn, err = net.ListenPacket("udp", s.address); err != nil {
+			return
+		}
+		go s.handle()
+	}
+
+	session.conn = s.conn
+
+	s.sessions[session.Remote.SSRC] = session
+}
+
+func (s *Server) DelSession(session *Session) {
+	s.mu.Lock()
+
+	delete(s.sessions, session.Remote.SSRC)
+
+	// check s.conn for https://github.com/AlexxIT/go2rtc/issues/734
+	if len(s.sessions) == 0 && s.conn != nil {
+		_ = s.conn.Close()
+	}
+
+	s.mu.Unlock()
+}
+
+func (s *Server) GetSession(ssrc uint32) (session *Session) {
+	s.mu.Lock()
+	session = s.sessions[ssrc]
+	s.mu.Unlock()
+	return
+}
+
+func (s *Server) handle() error {
+	b := make([]byte, 2048)
+	for {
+		n, _, err := s.conn.ReadFrom(b)
+		if err != nil {
+			return err
+		}
+
+		// Multiplexing RTP Data and Control Packets on a Single Port
+		// https://datatracker.ietf.org/doc/html/rfc5761
+
+		switch packetType := b[1]; packetType {
+		case 99, 110, 0x80 | 99, 0x80 | 110:
+			// this is default position for SSRC in RTP packet
+			ssrc := binary.BigEndian.Uint32(b[8:])
+			if session := s.GetSession(ssrc); session != nil {
+				session.ReadRTP(b[:n])
+			}
+
+		case 200, 201, 202, 203, 204, 205, 206, 207:
+			// this is default position for SSRC in RTCP packet
+			ssrc := binary.BigEndian.Uint32(b[4:])
+			if session := s.GetSession(ssrc); session != nil {
+				session.ReadRTCP(b[:n])
+			}
+		}
+	}
+}