syncthing/lib/connections/kcp_dial.go

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// Copyright (C) 2016 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.
package connections
import (
"crypto/tls"
"net/url"
"time"
"github.com/syncthing/syncthing/lib/config"
"github.com/syncthing/syncthing/lib/protocol"
"github.com/xtaci/kcp-go"
"github.com/xtaci/smux"
)
func init() {
factory := &kcpDialerFactory{}
for _, scheme := range []string{"kcp", "kcp4", "kcp6"} {
dialers[scheme] = factory
}
}
type kcpDialer struct {
cfg *config.Wrapper
tlsCfg *tls.Config
}
func (d *kcpDialer) Dial(id protocol.DeviceID, uri *url.URL) (internalConn, error) {
uri = fixupPort(uri, config.DefaultKCPPort)
var conn *kcp.UDPSession
var err error
// Try to dial via an existing listening connection
// giving better changes punching through NAT.
if f := getDialingFilter(); f != nil {
conn, err = kcp.NewConn(uri.Host, nil, 0, 0, f.NewConn(kcpConversationFilterPriority, &kcpConversationFilter{}))
l.Debugf("dial %s using existing conn on %s", uri.String(), conn.LocalAddr())
} else {
conn, err = kcp.DialWithOptions(uri.Host, nil, 0, 0)
}
if err != nil {
l.Debugln(err)
conn.Close()
return internalConn{}, err
}
opts := d.cfg.Options()
conn.SetStreamMode(true)
conn.SetACKNoDelay(false)
conn.SetWindowSize(opts.KCPSendWindowSize, opts.KCPReceiveWindowSize)
conn.SetNoDelay(boolInt(opts.KCPNoDelay), opts.KCPUpdateIntervalMs, boolInt(opts.KCPFastResend), boolInt(!opts.KCPCongestionControl))
ses, err := smux.Client(conn, smuxConfig)
if err != nil {
conn.Close()
return internalConn{}, err
}
stream, err := ses.OpenStream()
if err != nil {
ses.Close()
return internalConn{}, err
}
tc := tls.Client(&sessionClosingStream{stream, ses}, d.tlsCfg)
tc.SetDeadline(time.Now().Add(time.Second * 10))
err = tc.Handshake()
if err != nil {
tc.Close()
return internalConn{}, err
}
tc.SetDeadline(time.Time{})
return internalConn{tc, connTypeKCPClient, kcpPriority}, nil
}
func (d *kcpDialer) RedialFrequency() time.Duration {
// For restricted NATs, the UDP mapping will potentially only be open for 20-30 seconds
// hence try dialing just as often.
return time.Duration(d.cfg.Options().StunKeepaliveS) * time.Second
}
type kcpDialerFactory struct{}
func (kcpDialerFactory) New(cfg *config.Wrapper, tlsCfg *tls.Config) genericDialer {
return &kcpDialer{
cfg: cfg,
tlsCfg: tlsCfg,
}
}
func (kcpDialerFactory) Priority() int {
return kcpPriority
}
func (kcpDialerFactory) Enabled(cfg config.Configuration) bool {
return true
}
func (kcpDialerFactory) String() string {
return "KCP Dialer"
}