a couple race fixes and use timer.AfterFunc instead of sleeping goroutines or ticker in a few places

src/tuntap/conn.go

@@ -23,7 +23,7 @@ type tunConn struct {
 	addr  address.Address
 	snet  address.Subnet
 	stop  chan struct{}
-	alive chan struct{}
+	alive *time.Timer // From calling time.AfterFunc
 }
 
 func (s *tunConn) close() {
@@ -40,10 +40,6 @@ func (s *tunConn) _close_nomutex() {
 		defer func() { recover() }()
 		close(s.stop) // Closes reader/writer goroutines
 	}()
-	func() {
-		defer func() { recover() }()
-		close(s.alive) // Closes timeout goroutine
-	}()
 }
 
 func (s *tunConn) _read(bs []byte) (err error) {
@@ -228,27 +224,8 @@ func (s *tunConn) _write(bs []byte) (err error) {
 }
 
 func (s *tunConn) stillAlive() {
-	defer func() { recover() }()
-	select {
-	case s.alive <- struct{}{}:
-	default:
-	}
-}
-
-func (s *tunConn) checkForTimeouts() error {
-	timer := time.NewTimer(tunConnTimeout)
-	defer util.TimerStop(timer)
-	defer s.close()
-	for {
-		select {
-		case _, ok := <-s.alive:
-			if !ok {
-				return errors.New("connection closed")
-			}
-			util.TimerStop(timer)
-			timer.Reset(tunConnTimeout)
-		case <-timer.C:
-			return errors.New("timed out")
-		}
+	if s.alive != nil {
+		s.alive.Stop()
 	}
+	s.alive = time.AfterFunc(tunConnTimeout, s.close)
 }

src/tuntap/tun.go

@@ -227,10 +227,9 @@ func (tun *TunAdapter) handler() error {
 func (tun *TunAdapter) wrap(conn *yggdrasil.Conn) (c *tunConn, err error) {
 	// Prepare a session wrapper for the given connection
 	s := tunConn{
-		tun:   tun,
-		conn:  conn,
-		stop:  make(chan struct{}),
-		alive: make(chan struct{}, 1),
+		tun:  tun,
+		conn: conn,
+		stop: make(chan struct{}),
 	}
 	c = &s
 	// Get the remote address and subnet of the other side
@@ -255,13 +254,13 @@ func (tun *TunAdapter) wrap(conn *yggdrasil.Conn) (c *tunConn, err error) {
 	// we receive a packet through the interface for this address
 	tun.addrToConn[s.addr] = &s
 	tun.subnetToConn[s.snet] = &s
-	// Set the read callback and start the timeout goroutine
+	// Set the read callback and start the timeout
 	conn.SetReadCallback(func(bs []byte) {
 		s.RecvFrom(conn, func() {
 			s._read(bs)
 		})
 	})
-	go s.checkForTimeouts()
+	s.RecvFrom(nil, s.stillAlive)
 	// Return
 	return c, err
 }