Add support for IP address changes

This commit improves upon the existing "Wait for IP step", by
continuously checking for changes to the IP address for the VM, even
after the IP address has been retrieved.

The implementation is using a simple goroutine which encapsulates the
existing method used to wait for the IP address. When an IP address has
been found, the goroutine will put the IP address directly in the state,
which will be queried when the IP address should be retrieved.

builder/xenserver/common/ssh.go

@@ -157,8 +157,7 @@ func forward(local_conn net.Conn, config *gossh.ClientConfig, server string, ser
 	return nil
 }
 
-func ssh_port_forward(local_listener net.Listener, remote_port int, remote_dest, host string, host_ssh_port int, username, password string) error {
-
+func ssh_port_forward(local_listener net.Listener, remote_port int, host string, host_ssh_port int, username, password string, remote_dest_func func() (string, error)) error {
 	config := &gossh.ClientConfig{
 		User: username,
 		Auth: []gossh.AuthMethod{
@@ -175,6 +174,12 @@ func ssh_port_forward(local_listener net.Listener, remote_port int, remote_dest,
 			return err
 		}
 
+		remote_dest, err := remote_dest_func()
+
+		if err != nil {
+			return err
+		}
+
 		// Forward to a remote port
 		go forward(local_connection, config, host, host_ssh_port, remote_dest, uint(remote_port))
 	}

builder/xenserver/common/step_forward_port_over_ssh.go

@@ -39,7 +39,7 @@ func (self *StepForwardPortOverSSH) Run(ctx context.Context, state multistep.Sta
 	remotePort, _ := self.RemotePort(state)
 	remoteDest, _ := self.RemoteDest(state)
 
-	go ssh_port_forward(l, remotePort, remoteDest, hostAddress, hostSshPort, config.Username, config.Password)
+	go ssh_port_forward(l, remotePort, hostAddress, hostSshPort, config.Username, config.Password, func() (string, error) { return self.RemoteDest(state) })
 	ui.Say(fmt.Sprintf("Port forward setup. %d ---> %s:%d on %s", sshHostPort, remoteDest, remotePort, hostAddress))
 
 	// Provide the local port to future steps.

builder/xenserver/common/step_wait_for_ip.go

@@ -29,47 +29,62 @@ func (self *StepWaitForIP) Run(ctx context.Context, state multistep.StateBag) mu
 		return multistep.ActionHalt
 	}
 
-	var ip string
-	err = InterruptibleWait{
-		Timeout:           self.Timeout,
-		PredicateInterval: 5 * time.Second,
-		Predicate: func() (result bool, err error) {
+	go func(c Connection, ui packer.Ui, config CommonConfig) {
+		state.Put("instance_ssh_address", "")
+		var ip string
 
+		for true {
+			time.Sleep(500 * time.Millisecond)
 			if config.IPGetter == "auto" || config.IPGetter == "http" {
-
 				// Snoop IP from HTTP fetch
 				select {
-				case ip = <-self.Chan:
-					ui.Message(fmt.Sprintf("Got IP '%s' from HTTP request", ip))
-					return true, nil
+				case temp_ip := <-self.Chan:
+					if ip != temp_ip {
+						ip = temp_ip
+						ui.Message(fmt.Sprintf("Got IP '%s' from HTTP request", ip))
+						state.Put("instance_ssh_address", ip)
+					}
 				default:
 				}
-
 			}
 
 			if config.IPGetter == "auto" || config.IPGetter == "tools" {
-
 				// Look for PV IP
 				m, err := c.client.VM.GetGuestMetrics(c.session, instance)
 				if err != nil {
-					return false, err
+					continue
 				}
 				if m != "" {
 					metrics, err := c.client.VMGuestMetrics.GetRecord(c.session, m)
 					if err != nil {
-						return false, err
+						continue
 					}
 					networks := metrics.Networks
-					var ok bool
-					if ip, ok = networks["0/ip"]; ok {
-						if ip != "" {
+					if temp_ip, ok := networks["0/ip"]; ok {
+						if temp_ip != "" && ip != temp_ip {
+							ip = temp_ip
 							ui.Message(fmt.Sprintf("Got IP '%s' from XenServer tools", ip))
-							return true, nil
+							state.Put("instance_ssh_address", ip)
 						}
 					}
 				}
 
 			}
+		}
+	}(*c, ui, config)
+
+	time.Sleep(500 * time.Millisecond)
+
+	var ip string
+
+	err = InterruptibleWait{
+		Timeout:           self.Timeout,
+		PredicateInterval: 5 * time.Second,
+		Predicate: func() (result bool, err error) {
+			var ok bool
+			if ip, ok = state.Get("instance_ssh_address").(string); ok && ip != "" {
+				return true, nil
+			}
 
 			return false, nil
 		},