package udp import ( "bytes" "encoding/binary" "io" "net" "time" "github.com/pkg/errors" "golang.org/x/crypto/nacl/secretbox" ) type Connection struct { GatewayIP string GatewayPort uint16 ssrc uint32 sequence uint16 timestamp uint32 nonce [24]byte conn *net.UDPConn close chan struct{} closed chan struct{} send chan []byte reply chan error } func DialConnection(addr string, ssrc uint32) (*Connection, error) { // Resolve the host. a, err := net.ResolveUDPAddr("udp", addr) if err != nil { return nil, errors.Wrap(err, "failed to resolve host") } // Create a new UDP connection. conn, err := net.DialUDP("udp", nil, a) if err != nil { return nil, errors.Wrap(err, "failed to dial host") } // https://discordapp.com/developers/docs/topics/voice-connections#ip-discovery ssrcBuffer := [70]byte{ 0x1, 0x2, } binary.BigEndian.PutUint16(ssrcBuffer[2:4], 70) binary.BigEndian.PutUint32(ssrcBuffer[4:8], ssrc) _, err = conn.Write(ssrcBuffer[:]) if err != nil { return nil, errors.Wrap(err, "failed to write SSRC buffer") } var ipBuffer [70]byte // ReadFull makes sure to read all 70 bytes. _, err = io.ReadFull(conn, ipBuffer[:]) if err != nil { return nil, errors.Wrap(err, "failed to read IP buffer") } ipbody := ipBuffer[4:68] nullPos := bytes.Index(ipbody, []byte{'\x00'}) if nullPos < 0 { return nil, errors.New("UDP IP discovery did not contain a null terminator") } ip := ipbody[:nullPos] port := binary.LittleEndian.Uint16(ipBuffer[68:70]) return &Connection{ GatewayIP: string(ip), GatewayPort: port, ssrc: ssrc, conn: conn, send: make(chan []byte), reply: make(chan error), close: make(chan struct{}), closed: make(chan struct{}), }, nil } func (c *Connection) Start(secret *[32]byte) { // https://discordapp.com/developers/docs/topics/voice-connections#encrypting-and-sending-voice packet := [12]byte{ 0: 0x80, // Version + Flags 1: 0x78, // Payload Type // [2:4] // Sequence // [4:8] // Timestamp } // Write SSRC to the header. binary.BigEndian.PutUint32(packet[8:12], c.ssrc) // SSRC // 50 sends per second, 960 samples each at 48kHz frequency := time.NewTicker(time.Millisecond * 20) defer frequency.Stop() var b []byte var ok bool // Close these channels at the end so Write() doesn't block. defer func() { close(c.send) close(c.closed) }() for { select { case b, ok = <-c.send: if !ok { return } case <-c.close: return } // Write a new sequence. binary.BigEndian.PutUint16(packet[2:4], c.sequence) c.sequence++ binary.BigEndian.PutUint32(packet[4:8], c.timestamp) c.timestamp += 960 // Samples copy(c.nonce[:], packet[:]) toSend := secretbox.Seal(packet[:], b, &c.nonce, secret) select { case <-frequency.C: case <-c.close: return } _, err := c.conn.Write(toSend) c.reply <- err } } func (c *Connection) Close() error { close(c.close) <-c.closed return c.conn.Close() } // Write sends bytes into the voice UDP connection. func (c *Connection) Write(b []byte) (int, error) { c.send <- b if err := <-c.reply; err != nil { return 0, err } return len(b), nil }