bugfix: heartbeat span wrap round

main.go

@@ -16,6 +16,7 @@ import (
 	"github.com/xjdrew/gotunnel/tunnel"
 )
 
+// Service .
 type Service interface {
 	Start() error
 	Status()

tunnel/client.go

@@ -13,25 +13,26 @@ import (
 	"time"
 )
 
-// client hub
+// ClientHub manages client links
 type ClientHub struct {
 	*Hub
 	sent uint16
 	rcvd uint16
 }
 
 func (h *ClientHub) heartbeat() {
-	ticker := time.NewTicker(time.Duration(Heartbeat) * time.Second)
+	heartbeat := getHeartbeat()
+	ticker := time.NewTicker(heartbeat)
 	defer ticker.Stop()
 
-	maxSpan := Timeout / Heartbeat
-	if maxSpan <= TunnelMinSpan {
-		maxSpan = TunnelMinSpan
+	maxSpan := int(getTimeout() / heartbeat)
+	if maxSpan <= tunnelMinSpan {
+		maxSpan = tunnelMinSpan
 	}
-
+	Debug("maxspan: %d", maxSpan)
 	for range ticker.C {
 		// id overflow
-		span := h.sent - h.rcvd
+		span := 0xffff - h.rcvd + h.sent + 1
 		if int(span) >= maxSpan {
 			Error("tunnel(%v) timeout, sent:%d, rcvd:%d", h.Hub.tunnel, h.sent, h.rcvd)
 			h.Hub.Close()

tunnel/tunnel.go

@@ -10,15 +10,34 @@ import (
 )
 
 const (
-	TunnelMaxId           = ^uint16(0)
-	TunnelMinSpan         = 3 // 3次心跳无回应则断开
+	TunnelMaxId = ^uint16(0)
+
 	TunnelPacketSize      = 8192
 	TunnelKeepAlivePeriod = time.Second * 180
+
+	defaultHeartbeat = 1
+	tunnelMinSpan    = 3 // 3次心跳无回应则断开
 )
 
 var (
-	Heartbeat int  = 1
-	Timeout   int  = 0
-	LogLevel  uint = 1
-	mpool          = NewMPool(TunnelPacketSize)
+	// Heartbeat interval for tunnel heartbeat, seconds.
+	Heartbeat int = 1 // seconds
+
+	// Timeout for tunnel write/read, seconds
+	Timeout int = 0 //
+
+	// LogLevel .
+	LogLevel uint = 1
+	mpool         = NewMPool(TunnelPacketSize)
 )
+
+func getHeartbeat() time.Duration {
+	if Heartbeat <= 0 {
+		Heartbeat = defaultHeartbeat
+	}
+	return time.Duration(Heartbeat) * time.Second
+}
+
+func getTimeout() time.Duration {
+	return time.Duration(Timeout) * time.Second
+}