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103 lines
2.5 KiB
103 lines
2.5 KiB
package tcputil
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import (
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"net"
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"time"
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"github.com/xtaci/kcp-go/v5"
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"github.com/xtaci/smux"
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)
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// DtlsPacketConn wraps a net.Conn (DTLS) as a net.PacketConn for KCP.
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// Each DTLS Read/Write preserves message boundaries (datagram semantics).
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type DtlsPacketConn struct {
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conn net.Conn
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}
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func NewDtlsPacketConn(conn net.Conn) *DtlsPacketConn {
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return &DtlsPacketConn{conn: conn}
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}
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func (d *DtlsPacketConn) ReadFrom(b []byte) (int, net.Addr, error) {
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n, err := d.conn.Read(b)
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return n, d.conn.RemoteAddr(), err
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}
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func (d *DtlsPacketConn) WriteTo(b []byte, _ net.Addr) (int, error) {
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return d.conn.Write(b)
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}
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func (d *DtlsPacketConn) Close() error {
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return d.conn.Close()
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}
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func (d *DtlsPacketConn) LocalAddr() net.Addr {
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return d.conn.LocalAddr()
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}
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func (d *DtlsPacketConn) SetDeadline(t time.Time) error {
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return d.conn.SetDeadline(t)
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}
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func (d *DtlsPacketConn) SetReadDeadline(t time.Time) error {
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return d.conn.SetReadDeadline(t)
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}
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func (d *DtlsPacketConn) SetWriteDeadline(t time.Time) error {
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return d.conn.SetWriteDeadline(t)
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}
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// NewKCPOverDTLS creates a KCP session over a DTLS connection.
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// isServer: true for server-side (listener), false for client-side (dialer).
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func NewKCPOverDTLS(dtlsConn net.Conn, isServer bool) (*kcp.UDPSession, error) {
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pc := NewDtlsPacketConn(dtlsConn)
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block, err := kcp.NewNoneBlockCrypt(nil) // DTLS already encrypts
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if err != nil {
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return nil, err
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}
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var sess *kcp.UDPSession
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if isServer {
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// Server: listen on the PacketConn and accept one session
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var listener *kcp.Listener
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listener, err = kcp.ServeConn(block, 0, 0, pc)
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if err != nil {
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return nil, err
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}
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if err = listener.SetDeadline(time.Now().Add(30 * time.Second)); err != nil {
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return nil, err
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}
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sess, err = listener.AcceptKCP()
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if err != nil {
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return nil, err
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}
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} else {
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// Client: dial through the PacketConn
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sess, err = kcp.NewConn2(dtlsConn.RemoteAddr(), block, 0, 0, pc)
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if err != nil {
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return nil, err
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}
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}
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// Tune KCP for TURN tunnel:
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// - NoDelay mode for lower latency
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// - Window sizes suitable for ~5Mbit/s
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sess.SetNoDelay(1, 10, 2, 1) // nodelay, interval(ms), resend, nc
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sess.SetWindowSize(4096, 4096)
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sess.SetMtu(1280) // conservative MTU to fit inside DTLS+TURN
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sess.SetACKNoDelay(true)
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return sess, nil
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}
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// DefaultSmuxConfig returns smux config tuned for TURN tunnel.
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func DefaultSmuxConfig() *smux.Config {
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cfg := smux.DefaultConfig()
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cfg.MaxReceiveBuffer = 4 * 1024 * 1024
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cfg.MaxStreamBuffer = 1 * 1024 * 1024
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cfg.KeepAliveInterval = 10 * time.Second
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cfg.KeepAliveTimeout = 30 * time.Second
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return cfg
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}
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