fix: fix the udpConns map does not release new conns when its length …

…is over 100 (jpillora#515)

share/tunnel/tunnel_out_ssh_udp.go

@@ -28,6 +28,7 @@ func (t *Tunnel) handleUDP(l *cio.Logger, rwc io.ReadWriteCloser, hostPort strin
 		},
 		udpConns: conns,
 		maxMTU:   settings.EnvInt("UDP_MAX_SIZE", 9012),
+		maxConns: settings.EnvInt("UDP_MAX_CONNS", 100),
 	}
 	h.Debugf("UDP max size: %d bytes", h.maxMTU)
 	for {
@@ -43,7 +44,8 @@ type udpHandler struct {
 	hostPort string
 	*udpChannel
 	*udpConns
-	maxMTU int
+	maxMTU   int
+	maxConns int
 }
 
 func (h *udpHandler) handleWrite(p *udpPacket) error {
@@ -62,12 +64,14 @@ func (h *udpHandler) handleWrite(p *udpPacket) error {
 	//TODO++ dont use go-routines, switch to pollable
 	//  array of listeners where all listeners are
 	//  sweeped periodically, removing the idle ones
-	const maxConns = 100
+
 	if !exists {
-		if h.udpConns.len() <= maxConns {
+		if h.udpConns.len() <= h.maxConns {
 			go h.handleRead(p, conn)
 		} else {
-			h.Debugf("exceeded max udp connections (%d)", maxConns)
+			//write only
+			h.udpConns.setCleanUpTimer(conn.id)
+			h.Debugf("exceeded max udp connections (%d)", h.maxConns)
 		}
 	}
 	_, err = conn.Write(p.Payload)
@@ -79,7 +83,14 @@ func (h *udpHandler) handleWrite(p *udpPacket) error {
 
 func (h *udpHandler) handleRead(p *udpPacket, conn *udpConn) {
 	//ensure connection is cleaned up
-	defer h.udpConns.remove(conn.id)
+	defer func() {
+		h.udpConns.remove(conn.id)
+		conn.Close()
+	}()
+	if h.udpConns.len() > h.maxConns {
+		h.Debugf("exceeded max udp connections (%d)", h.maxConns)
+		return
+	}
 	buff := make([]byte, h.maxMTU)
 	for {
 		//response must arrive within 15 seconds
@@ -149,7 +160,35 @@ func (cs *udpConns) closeAll() {
 	cs.Unlock()
 }
 
+func (cs *udpConns) setCleanUpTimer(id string) {
+	cs.Lock()
+	defer cs.Unlock()
+	conn, ok := cs.m[id]
+	if ok {
+		conn.writeTimer = time.AfterFunc(settings.EnvDuration("UDP_DEADLINE", 15*time.Second), func() {
+			cs.remove(conn.id)
+			conn.Close()
+		})
+	}
+}
+
 type udpConn struct {
 	id string
 	net.Conn
+	writeTimer *time.Timer
+}
+
+func (w *udpConn) Write(b []byte) (int, error) {
+	if w.writeTimer != nil {
+		w.writeTimer.Stop()
+		w.writeTimer.Reset(settings.EnvDuration("UDP_DEADLINE", 15*time.Second))
+	}
+	return w.Conn.Write(b)
+}
+
+func (w *udpConn) Close() error {
+	if w.writeTimer != nil {
+		w.writeTimer.Stop()
+	}
+	return w.Conn.Close()
 }