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package sctp
import (
"sync"
"time"
)
const (
ackInterval time.Duration = 200 * time.Millisecond
)
// ackTimerObserver is the inteface to an ack timer observer.
type ackTimerObserver interface {
onAckTimeout()
}
// ackTimer provides the retnransmission timer conforms with RFC 4960 Sec 6.3.1
type ackTimer struct {
observer ackTimerObserver
interval time.Duration
stopFunc stopAckTimerLoop
closed bool
mutex sync.RWMutex
}
type stopAckTimerLoop func()
// newAckTimer creates a new acknowledgement timer used to enable delayed ack.
func newAckTimer(observer ackTimerObserver) *ackTimer {
return &ackTimer{
observer: observer,
interval: ackInterval,
}
}
// start starts the timer.
func (t *ackTimer) start() bool {
t.mutex.Lock()
defer t.mutex.Unlock()
// this timer is already closed
if t.closed {
return false
}
// this is a noop if the timer is already running
if t.stopFunc != nil {
return false
}
cancelCh := make(chan struct{})
go func() {
timer := time.NewTimer(t.interval)
select {
case <-timer.C:
t.stop()
t.observer.onAckTimeout()
case <-cancelCh:
timer.Stop()
}
}()
t.stopFunc = func() {
close(cancelCh)
}
return true
}
// stops the timer. this is similar to stop() but subsequent start() call
// will fail (the timer is no longer usable)
func (t *ackTimer) stop() {
t.mutex.Lock()
defer t.mutex.Unlock()
if t.stopFunc != nil {
t.stopFunc()
t.stopFunc = nil
}
}
// closes the timer. this is similar to stop() but subsequent start() call
// will fail (the timer is no longer usable)
func (t *ackTimer) close() {
t.mutex.Lock()
defer t.mutex.Unlock()
if t.stopFunc != nil {
t.stopFunc()
t.stopFunc = nil
}
t.closed = true
}
// isRunning tests if the timer is running.
// Debug purpose only
func (t *ackTimer) isRunning() bool {
t.mutex.RLock()
defer t.mutex.RUnlock()
return (t.stopFunc != nil)
}
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