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Cloak/internal/multiplex/switchboard.go

162 lines
3.6 KiB
Go

package multiplex
import (
"errors"
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"log"
"net"
"sync"
"sync/atomic"
)
// switchboard is responsible for keeping the reference of TLS connections between client and server
type switchboard struct {
session *Session
*Valve
// optimum is the connEnclave with the smallest sendQueue
optimum atomic.Value // *connEnclave
cesM sync.RWMutex
ces []*connEnclave
}
func (sb *switchboard) getOptimum() *connEnclave {
if i := sb.optimum.Load(); i == nil {
return nil
} else {
return i.(*connEnclave)
}
}
// Some data comes from a Stream to be sent through one of the many
// remoteConn, but which remoteConn should we use to send the data?
//
// In this case, we pick the remoteConn that has about the smallest sendQueue.
type connEnclave struct {
remoteConn net.Conn
sendQueue uint32
}
func makeSwitchboard(sesh *Session, valve *Valve) *switchboard {
// rates are uint64 because in the usermanager we want the bandwidth to be atomically
// operated (so that the bandwidth can change on the fly).
sb := &switchboard{
session: sesh,
Valve: valve,
ces: []*connEnclave{},
}
return sb
}
var errNilOptimum error = errors.New("The optimal connection is nil")
var ErrNoRxCredit error = errors.New("No Rx credit is left")
var ErrNoTxCredit error = errors.New("No Tx credit is left")
func (sb *switchboard) send(data []byte) (int, error) {
ce := sb.getOptimum()
if ce == nil {
return 0, errNilOptimum
}
atomic.AddUint32(&ce.sendQueue, uint32(len(data)))
go sb.updateOptimum()
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n, err := ce.remoteConn.Write(data)
if err != nil {
return n, err
}
sb.txWait(n)
if sb.AddTxCredit(-int64(n)) < 0 {
log.Println(ErrNoTxCredit)
go sb.session.Close()
return n, ErrNoTxCredit
}
atomic.AddUint32(&ce.sendQueue, ^uint32(n-1))
go sb.updateOptimum()
return n, nil
}
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func (sb *switchboard) updateOptimum() {
currentOpti := sb.getOptimum()
currentOptiQ := atomic.LoadUint32(&currentOpti.sendQueue)
sb.cesM.RLock()
for _, ce := range sb.ces {
ceQ := atomic.LoadUint32(&ce.sendQueue)
if ceQ < currentOptiQ {
currentOpti = ce
currentOptiQ = ceQ
}
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}
sb.cesM.RUnlock()
sb.optimum.Store(currentOpti)
}
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func (sb *switchboard) addConn(conn net.Conn) {
var sendQueue uint32
newCe := &connEnclave{
remoteConn: conn,
sendQueue: sendQueue,
}
sb.cesM.Lock()
sb.ces = append(sb.ces, newCe)
sb.cesM.Unlock()
sb.optimum.Store(newCe)
go sb.deplex(newCe)
}
func (sb *switchboard) removeConn(closing *connEnclave) {
sb.cesM.Lock()
for i, ce := range sb.ces {
if closing == ce {
sb.ces = append(sb.ces[:i], sb.ces[i+1:]...)
break
}
}
if len(sb.ces) == 0 {
sb.session.Close()
}
sb.cesM.Unlock()
}
// actively triggered by session.Close()
func (sb *switchboard) closeAll() {
sb.cesM.RLock()
for _, ce := range sb.ces {
ce.remoteConn.Close()
}
sb.cesM.RUnlock()
}
// deplex function costantly reads from a TCP connection, call deobfs and distribute it
// to the corresponding stream
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func (sb *switchboard) deplex(ce *connEnclave) {
buf := make([]byte, 20480)
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for {
n, err := sb.session.obfsedRead(ce.remoteConn, buf)
sb.rxWait(n)
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if err != nil {
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//log.Println(err)
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go ce.remoteConn.Close()
sb.removeConn(ce)
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return
}
if sb.AddRxCredit(-int64(n)) < 0 {
log.Println(ErrNoRxCredit)
sb.session.Close()
return
}
frame, err := sb.session.deobfs(buf[:n])
if err != nil {
log.Println(err)
continue
}
stream := sb.session.getStream(frame.StreamID, frame.Closing == 1)
// if the frame is telling us to close a closed stream
// (this happens when ss-server and ss-local closes the stream
// simutaneously), we don't do anything
if stream != nil {
stream.writeNewFrame(frame)
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}
}
}