Use simple 16-bit integer for persistent keepalive

Races for this aren't a huge problem.

peer.go

@@ -13,13 +13,14 @@ const (
 )
 
 type Peer struct {
-	persistentKeepaliveInterval uint64
 	isRunning                   AtomicBool
 	mutex                       sync.RWMutex
 	keyPairs                    KeyPairs
 	handshake                   Handshake
 	device                      *Device
 	endpoint                    Endpoint
+	persistentKeepaliveInterval uint16
+	_                           uint32 // padding for alignment
 
 	stats struct {
 		txBytes           uint64 // bytes send to peer (endpoint)

timers.go

@@ -105,7 +105,7 @@ func (peer *Peer) TimerAnyAuthenticatedPacketReceived() {
  * Push persistent keep-alive into the future
  */
 func (peer *Peer) TimerAnyAuthenticatedPacketTraversal() {
-	interval := atomic.LoadUint64(&peer.persistentKeepaliveInterval)
+	interval := peer.persistentKeepaliveInterval
 	if interval > 0 {
 		duration := time.Duration(interval) * time.Second
 		peer.timer.keepalivePersistent.Reset(duration)
@@ -199,7 +199,7 @@ func (peer *Peer) RoutineTimerHandler() {
 	peer.timer.handshakeNew.Stop()
 	peer.timer.zeroAllKeys.Stop()
 
-	interval := atomic.LoadUint64(&peer.persistentKeepaliveInterval)
+	interval := peer.persistentKeepaliveInterval
 	if interval > 0 {
 		duration := time.Duration(interval) * time.Second
 		peer.timer.keepalivePersistent.Reset(duration)
@@ -225,7 +225,7 @@ func (peer *Peer) RoutineTimerHandler() {
 
 		case <-peer.timer.keepalivePersistent.Wait():
 
-			interval := atomic.LoadUint64(&peer.persistentKeepaliveInterval)
+			interval := peer.persistentKeepaliveInterval
 			if interval > 0 {
 				logDebug.Println(peer.String(), ": Send keep-alive (persistent)")
 				peer.timer.keepalivePassive.Stop()

uapi.go

@@ -84,9 +84,7 @@ func ipcGetOperation(device *Device, socket *bufio.ReadWriter) *IPCError {
 			send(fmt.Sprintf("last_handshake_time_nsec=%d", nano))
 			send(fmt.Sprintf("tx_bytes=%d", peer.stats.txBytes))
 			send(fmt.Sprintf("rx_bytes=%d", peer.stats.rxBytes))
-			send(fmt.Sprintf("persistent_keepalive_interval=%d",
-				atomic.LoadUint64(&peer.persistentKeepaliveInterval),
-			))
+			send(fmt.Sprintf("persistent_keepalive_interval=%d", peer.persistentKeepaliveInterval))
 
 			for _, ip := range device.routing.table.AllowedIPs(peer) {
 				send("allowed_ip=" + ip.String())
@@ -322,10 +320,8 @@ func ipcSetOperation(device *Device, socket *bufio.ReadWriter) *IPCError {
 					return &IPCError{Code: ipcErrorInvalid}
 				}
 
-				old := atomic.SwapUint64(
-					&peer.persistentKeepaliveInterval,
-					secs,
-				)
+				old := peer.persistentKeepaliveInterval
+				peer.persistentKeepaliveInterval = uint16(secs)
 
 				// send immediate keep-alive