fix #20 report errors while executing arp command

command/command.go

@@ -41,7 +41,7 @@ func (c *cmd) call(showProgress bool, msg string) (string, error) {
 	cmd.Stderr = &stderr
 
 	if err := cmd.Start(); err != nil {
-		return "", errors.New(string(stderr.Bytes()))
+		return "", errors.New(err.Error() + " " + string(stderr.Bytes()))
 	}
 
 	if showProgress {
@@ -50,7 +50,7 @@ func (c *cmd) call(showProgress bool, msg string) (string, error) {
 	}
 
 	if err := cmd.Wait(); err != nil {
-		return "", errors.New(string(stderr.Bytes()))
+		return "", errors.New(err.Error() + " " + string(stderr.Bytes()))
 	}
 
 	return string(stdout.Bytes()), nil

ip/arp.go

@@ -7,11 +7,14 @@ import (
 	"strings"
 )
 
-func getArpTable() []addr {
+func getArpTable() ([]addr, error) {
 
 	addrs := make([]addr, 0)
 
-	out, _ := command.Arp("-an").Call()
+	out, err := command.Arp("-an").Call()
+	if err != nil {
+		return nil, err
+	}
 	entries := strings.Split(out, "\n")
 
 	for _, entry := range entries {
@@ -27,5 +30,5 @@ func getArpTable() []addr {
 		}
 	}
 
-	return addrs
+	return addrs, nil
 }

ip/arp_windows.go

@@ -5,11 +5,14 @@ import (
 	"strings"
 )
 
-func getArpTable() []addr {
+func getArpTable() ([]addr, error) {
 
 	addrs := make([]addr, 0)
 
-	s, _ := command.Arp("-a").Call()
+	s, err := command.Arp("-a").Call()
+	if err != nil {
+		return nil, err
+	}
 	ss := strings.Split(s, "\n\r")
 
 	for _, out := range ss {
@@ -25,5 +28,5 @@ func getArpTable() []addr {
 			}
 		}
 	}
-	return addrs
+	return addrs, nil
 }

ip/ip.go

@@ -31,7 +31,11 @@ func Find(vmName string, purge bool) (string, error) {
 	}
 
 	for {
-		arp := getArpTable()
+		arp, err := getArpTable()
+		if err != nil {
+			return "", err
+		}
+
 		for i := len(arp) - 1; i >= 0; i-- {
 			a := arp[i]
 			if a.mac == mac {