builder/vmware: Try to use `ip address` to find host IP

Closes #4406

builder/vmware/common/host_ip_ifconfig.go

@@ -8,12 +8,59 @@ import (
 	"regexp"
 )
 
-// IfconfigIPFinder finds the host IP based on the output of `ifconfig`.
+// IfconfigIPFinder finds the host IP based on the output of `ip address` or `ifconfig`.
 type IfconfigIPFinder struct {
 	Device string
 }
 
 func (f *IfconfigIPFinder) HostIP() (string, error) {
+	ip, err := ipaddress(f.Device)
+	if err != nil || ip == "" {
+		return ifconfig(f.Device)
+	}
+	return ip, err
+}
+
+func ipaddress(device string) (string, error) {
+	var ipPath string
+
+	// On some systems, ip is in /sbin which is generally not
+	// on the PATH for a standard user, so we just check that first.
+	if _, err := os.Stat("/sbin/ip"); err == nil {
+		ipPath = "/sbin/ip"
+	}
+
+	if ipPath == "" {
+		var err error
+		ipPath, err = exec.LookPath("ip")
+		if err != nil {
+			return "", err
+		}
+	}
+
+	stdout := new(bytes.Buffer)
+	cmd := exec.Command(ipPath, "address", "show", "dev", device)
+	// Force LANG=C so that the output is what we expect it to be
+	// despite the locale.
+	cmd.Env = append(cmd.Env, "LANG=C")
+	cmd.Env = append(cmd.Env, os.Environ()...)
+
+	cmd.Stdout = stdout
+	cmd.Stderr = new(bytes.Buffer)
+	if err := cmd.Run(); err != nil {
+		return "", err
+	}
+
+	re := regexp.MustCompile(`inet[^\d]+([\d\.]+)/`)
+	matches := re.FindStringSubmatch(stdout.String())
+	if matches == nil {
+		return "", errors.New("IP not found in ip a output...")
+	}
+
+	return matches[1], nil
+}
+
+func ifconfig(device string) (string, error) {
 	var ifconfigPath string
 
 	// On some systems, ifconfig is in /sbin which is generally not
@@ -32,7 +79,7 @@ func (f *IfconfigIPFinder) HostIP() (string, error) {
 
 	stdout := new(bytes.Buffer)
 
-	cmd := exec.Command(ifconfigPath, f.Device)
+	cmd := exec.Command(ifconfigPath, device)
 	// Force LANG=C so that the output is what we expect it to be
 	// despite the locale.
 	cmd.Env = append(cmd.Env, "LANG=C")