grpc: close underlying transport when subConn is closed when in connecting state (#4751)

clientconn.go

@@ -1322,17 +1322,19 @@ func (ac *addrConn) createTransport(addr resolver.Address, copts transport.Conne
 	}
 
 	select {
-	case <-time.After(time.Until(connectDeadline)):
+	case <-connectCtx.Done():
 		// We didn't get the preface in time.
-		err := fmt.Errorf("failed to receive server preface within timeout")
-		newTr.Close(err)
-		channelz.Warningf(logger, ac.channelzID, "grpc: addrConn.createTransport failed to connect to %v: %v", addr, err)
-		return err
+		newTr.Close(transport.ErrConnClosing)
+		if connectCtx.Err() == context.DeadlineExceeded {
+			err := errors.New("failed to receive server preface within timeout")
+			channelz.Warningf(logger, ac.channelzID, "grpc: addrConn.createTransport failed to connect to %v: %v", addr, err)
+			return err
+		}
+		return nil
 	case <-prefaceReceived.Done():
 		// We got the preface - huzzah! things are good.
 		ac.mu.Lock()
 		defer ac.mu.Unlock()
-		defer prefaceReceived.Fire()
 		if connClosed.HasFired() {
 			// onClose called first; go idle but do nothing else.
 			if ac.state != connectivity.Shutdown {
@@ -1340,6 +1342,16 @@ func (ac *addrConn) createTransport(addr resolver.Address, copts transport.Conne
 			}
 			return nil
 		}
+		if ac.state == connectivity.Shutdown {
+			// This can happen if the subConn was removed while in `Connecting`
+			// state. tearDown() would have set the state to `Shutdown`, but
+			// would not have closed the transport since ac.transport would not
+			// been set at that point.
+			// We run this in a goroutine because newTr.Close() calls onClose()
+			// inline, which requires locking ac.mu.
+			go newTr.Close(transport.ErrConnClosing)
+			return nil
+		}
 		ac.curAddr = addr
 		ac.transport = newTr
 		hcStarted = true