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

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
 }