Try another ssh port if the current one is taken.

builder/qemu/step_forward_ssh.go

@@ -34,12 +34,17 @@ func (s *stepForwardSSH) Run(state multistep.StateBag) multistep.StepAction {
 
 	for {
 		sshHostPort = offset + config.SSHHostPortMin
+		if sshHostPort >= config.SSHHostPortMax {
+			offset = 0
+			sshHostPort = config.SSHHostPortMin
+		}
 		log.Printf("Trying port: %d", sshHostPort)
 		l, err := net.Listen("tcp", fmt.Sprintf(":%d", sshHostPort))
 		if err == nil {
 			defer l.Close()
 			break
 		}
+		offset++
 	}
 	ui.Say(fmt.Sprintf("Found port for SSH: %d.", sshHostPort))
 

builder/virtualbox/common/step_forward_ssh.go

@@ -42,12 +42,17 @@ func (s *StepForwardSSH) Run(state multistep.StateBag) multistep.StepAction {
 
 	for {
 		sshHostPort = offset + s.HostPortMin
+		if sshHostPort >= s.HostPortMax {
+			offset = 0
+			sshHostPort = s.HostPortMin
+		}
 		log.Printf("Trying port: %d", sshHostPort)
 		l, err := net.Listen("tcp", fmt.Sprintf("127.0.0.1:%d", sshHostPort))
 		if err == nil {
 			defer l.Close()
 			break
 		}
+		offset++
 	}
 
 	// Create a forwarded port mapping to the VM