syncthing/lib/connections/kcp_misc.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 (
"bytes"
"encoding/binary"
"net"
"sort"
"sync"
"sync/atomic"
"time"
"github.com/AudriusButkevicius/kcp-go"
"github.com/AudriusButkevicius/pfilter"
"github.com/xtaci/smux"
)
var (
mut sync.Mutex
filters filterList
)
func init() {
kcp.BlacklistDuration = 10 * time.Minute
}
type filterList []*pfilter.PacketFilter
// Sort connections by whether they are unspecified or not, as connections
// listening on all addresses are more useful.
func (f filterList) Len() int { return len(f) }
func (f filterList) Swap(i, j int) { f[i], f[j] = f[j], f[i] }
func (f filterList) Less(i, j int) bool {
iIsUnspecified := false
jIsUnspecified := false
if host, _, err := net.SplitHostPort(f[i].LocalAddr().String()); err == nil {
iIsUnspecified = net.ParseIP(host).IsUnspecified()
}
if host, _, err := net.SplitHostPort(f[j].LocalAddr().String()); err == nil {
jIsUnspecified = net.ParseIP(host).IsUnspecified()
}
return (iIsUnspecified && !jIsUnspecified) || (iIsUnspecified && jIsUnspecified)
}
// As we open listen KCP connections, we register them here, so that Dial calls through
// KCP could reuse them. This way we will hopefully work around restricted NATs by
// dialing via the same connection we are listening on, creating a mapping on our NAT
// to that IP, and hoping that the other end will try to dial our listen address and
// using the mapping we've established when we dialed.
func getDialingFilter() *pfilter.PacketFilter {
mut.Lock()
defer mut.Unlock()
if len(filters) == 0 {
return nil
}
return filters[0]
}
func registerFilter(filter *pfilter.PacketFilter) {
mut.Lock()
defer mut.Unlock()
filters = append(filters, filter)
sort.Sort(filterList(filters))
}
func deregisterFilter(filter *pfilter.PacketFilter) {
mut.Lock()
defer mut.Unlock()
for i, f := range filters {
if f == filter {
copy(filters[i:], filters[i+1:])
filters[len(filters)-1] = nil
filters = filters[:len(filters)-1]
break
}
}
sort.Sort(filterList(filters))
}
// Filters
type kcpConversationFilter struct {
convID uint32
}
func (f *kcpConversationFilter) Outgoing(out []byte, addr net.Addr) {
if !f.isKCPConv(out) {
panic("not a kcp conversation")
}
atomic.StoreUint32(&f.convID, binary.LittleEndian.Uint32(out[:4]))
}
func (kcpConversationFilter) isKCPConv(data []byte) bool {
// Need at least 5 bytes
if len(data) < 5 {
return false
}
// First 4 bytes convID
// 5th byte is cmd
// IKCP_CMD_PUSH = 81 // cmd: push data
// IKCP_CMD_ACK = 82 // cmd: ack
// IKCP_CMD_WASK = 83 // cmd: window probe (ask)
// IKCP_CMD_WINS = 84 // cmd: window size (tell)
return 80 < data[4] && data[4] < 85
}
func (f *kcpConversationFilter) ClaimIncoming(in []byte, addr net.Addr) bool {
if f.isKCPConv(in) {
convID := atomic.LoadUint32(&f.convID)
return convID != 0 && binary.LittleEndian.Uint32(in[:4]) == convID
}
return false
}
type stunFilter struct {
ids map[string]time.Time
mut sync.Mutex
}
func (f *stunFilter) Outgoing(out []byte, addr net.Addr) {
if !f.isStunPayload(out) {
panic("not a stun payload")
}
id := string(out[8:20])
f.mut.Lock()
f.ids[id] = time.Now().Add(time.Minute)
f.reap()
f.mut.Unlock()
}
func (f *stunFilter) ClaimIncoming(in []byte, addr net.Addr) bool {
if f.isStunPayload(in) {
id := string(in[8:20])
f.mut.Lock()
_, ok := f.ids[id]
f.reap()
f.mut.Unlock()
return ok
}
return false
}
func (f *stunFilter) isStunPayload(data []byte) bool {
// Need at least 20 bytes
if len(data) < 20 {
return false
}
// First two bits always unset, and should always send magic cookie.
return data[0]&0xc0 == 0 && bytes.Equal(data[4:8], []byte{0x21, 0x12, 0xA4, 0x42})
}
func (f *stunFilter) reap() {
now := time.Now()
for id, timeout := range f.ids {
if timeout.Before(now) {
delete(f.ids, id)
}
}
}
type sessionClosingStream struct {
*smux.Stream
session *smux.Session
}
func (w *sessionClosingStream) Close() error {
err1 := w.Stream.Close()
deadline := time.Now().Add(5 * time.Second)
for w.session.NumStreams() > 0 && time.Now().Before(deadline) {
time.Sleep(200 * time.Millisecond)
}
err2 := w.session.Close()
if err1 != nil {
return err1
}
return err2
}
func boolInt(b bool) int {
if b {
return 1
}
return 0
}