text: /*
   *
   * Copyright 2018 gRPC authors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *
   */
  
  // Package service manages connections between the VM application and the ALTS
  // handshaker service.
  package service
  
  import (
  	"sync"
  
  	grpc "google.golang.org/grpc"
  )
  
  var (
  	// hsConn represents a connection to hypervisor handshaker service.
  	hsConn *grpc.ClientConn
  	mu     sync.Mutex
  	// hsDialer will be reassigned in tests.
  	hsDialer = grpc.Dial
  )
  
  // Dial dials the handshake service in the hypervisor. If a connection has
  // already been established, this function returns it. Otherwise, a new
  // connection is created.
  func Dial(hsAddress string) (*grpc.ClientConn, error) {
  	mu.Lock()
  	defer mu.Unlock()
  
  	if hsConn == nil {
  		// Create a new connection to the handshaker service. Note that
  		// this connection stays open until the application is closed.
  		var err error
  		hsConn, err = hsDialer(hsAddress, grpc.WithInsecure())
  		if err != nil {
  			return nil, err
  		}
  	}
  	return hsConn, nil
  }
  