Merge pull request #10451 from somerandomqaguy/fix-qemu-vnc_min_port

Fix for vnc_min_port set to value greater then 5900 potentially causing packer to be unable to connect to QEMU

builder/qemu/config.go

@@ -374,6 +374,8 @@ type Config struct {
 	// the initial boot_command. Because Packer generally runs in parallel,
 	// Packer uses a randomly chosen port in this range that appears available. By
 	// default this is 5900 to 6000. The minimum and maximum ports are inclusive.
+	// The minimum port cannot be set below 5900 due to a quirk in how QEMU parses
+	// vnc display address.
 	VNCPortMin int `mapstructure:"vnc_port_min" required:"false"`
 	VNCPortMax int `mapstructure:"vnc_port_max"`
 	// This is the name of the image (QCOW2 or IMG) file for
@@ -592,6 +594,16 @@ func (c *Config) Prepare(raws ...interface{}) ([]string, error) {
 		}
 	}
 
+	if c.VNCPortMin < 5900 {
+		errs = packersdk.MultiErrorAppend(
+			errs, fmt.Errorf("vnc_port_min cannot be below 5900"))
+	}
+
+	if c.VNCPortMin > 65535 || c.VNCPortMax > 65535 {
+		errs = packersdk.MultiErrorAppend(
+			errs, fmt.Errorf("vmc_port_min and vnc_port_max must both be below 65535 to be valid TCP ports"))
+	}
+
 	if c.VNCPortMin > c.VNCPortMax {
 		errs = packersdk.MultiErrorAppend(
 			errs, fmt.Errorf("vnc_port_min must be less than vnc_port_max"))

builder/qemu/step_run.go

@@ -120,17 +120,18 @@ func (s *stepRun) getDefaultArgs(config *Config, state multistep.StateBag) map[s
 	vncPort := state.Get("vnc_port").(int)
 	vncIP := config.VNCBindAddress
 
-	vncPort = vncPort - config.VNCPortMin
-	vnc := fmt.Sprintf("%s:%d", vncIP, vncPort)
+	vncRealAddress := fmt.Sprintf("%s:%d", vncIP, vncPort)
+	vncPort = vncPort - 5900
+	vncArgs := fmt.Sprintf("%s:%d", vncIP, vncPort)
 	if config.VNCUsePassword {
-		vnc = fmt.Sprintf("%s:%d,password", vncIP, vncPort)
+		vncArgs = fmt.Sprintf("%s:%d,password", vncIP, vncPort)
 	}
-	defaultArgs["-vnc"] = vnc
+	defaultArgs["-vnc"] = vncArgs
 
 	// Track the connection for the user
 	vncPass, _ := state.Get("vnc_password").(string)
 
-	message = getVncConnectionMessage(config.Headless, vnc, vncPass)
+	message = getVncConnectionMessage(config.Headless, vncRealAddress, vncPass)
 	if message != "" {
 		s.ui.Message(message)
 	}

builder/qemu/step_run_test.go

@@ -105,7 +105,7 @@ func Test_UserOverrides(t *testing.T) {
 			"-fda", "fake_floppy_path",
 			"-name", "myvm",
 			"-netdev", "user,id=user.0,hostfwd=tcp::5000-:0",
-			"-vnc", ":5905",
+			"-vnc", ":5",
 			"-machine", "type=,accel="},
 			tc.Expected...)
 
@@ -416,7 +416,7 @@ func Test_DriveAndDeviceArgs(t *testing.T) {
 			"-fda", "fake_floppy_path",
 			"-name", "",
 			"-netdev", "user,id=user.0,hostfwd=tcp::5000-:0",
-			"-vnc", ":5905",
+			"-vnc", ":5",
 			"-machine", "type=,accel=",
 			"-device", ",netdev=user.0"},
 			tc.Expected...)
@@ -453,7 +453,7 @@ func Test_OptionalConfigOptionsGetSet(t *testing.T) {
 		"-fda", "fake_floppy_path",
 		"-name", "MyFancyName",
 		"-netdev", "user,id=user.0,hostfwd=tcp::5000-:0",
-		"-vnc", ":5905,password",
+		"-vnc", ":5,password",
 		"-machine", "type=pc,accel=hvf",
 		"-device", ",netdev=user.0",
 		"-drive", "file=/path/to/test.iso,index=0,media=cdrom",
@@ -596,7 +596,7 @@ func Test_Defaults(t *testing.T) {
 				"vnc_port": 5959,
 			},
 			&stepRun{ui: packersdk.TestUi(t)},
-			[]string{"-vnc", "1.1.1.1:5959"},
+			[]string{"-vnc", "1.1.1.1:59"},
 			"no VNC password should be set",
 		},
 		{
@@ -608,7 +608,7 @@ func Test_Defaults(t *testing.T) {
 				"vnc_port": 5959,
 			},
 			&stepRun{ui: packersdk.TestUi(t)},
-			[]string{"-vnc", "1.1.1.1:5959,password"},
+			[]string{"-vnc", "1.1.1.1:59,password"},
 			"VNC password should be set",
 		},
 		{

website/content/partials/builder/qemu/Config-not-required.mdx

@@ -301,6 +301,8 @@
   the initial boot_command. Because Packer generally runs in parallel,
   Packer uses a randomly chosen port in this range that appears available. By
   default this is 5900 to 6000. The minimum and maximum ports are inclusive.
+  The minimum port cannot be set below 5900 due to a quirk in how QEMU parses
+  vnc display address.
 
 - `vnc_port_max` (int) - VNC Port Max