Update (#2)

* Refactoring and better error checking

* Add the possibility to specify the nsPath

Author: PouuleT

main.go

@@ -17,7 +17,7 @@ import (
 	"github.com/vishvananda/netns"
 )
 
-var ip, command, gateway, intf, logLevel string
+var ip, command, gateway, intf, logLevel, nsPath string
 var log = logrus.New()
 
 func init() {
@@ -26,6 +26,12 @@ func init() {
 	flag.StringVar(&command, "command", "ip route", "command to be executed")
 	flag.StringVar(&gateway, "gw", "", "gateway of the request")
 	flag.StringVar(&logLevel, "log-level", "info", "min level of logs to print")
+	flag.StringVar(
+		&nsPath,
+		"ns-path",
+		fmt.Sprintf("/var/run/netns/w000t%d", os.Getpid()),
+		"path of the temporary namespace to be created, default will be /var/run/netns/w000t$PID",
+	)
 	flag.Parse()
 }
 
@@ -58,18 +64,17 @@ func main() {
 	// Check the /run/netns mount
 	err = setupNetnsDir()
 	if err != nil {
-		log.Warn("Error setting up netns", err)
+		log.Warn("Error setting up netns: ", err)
 		return
 	}
 
 	eth, err := netlink.LinkByName(intf)
 	if err != nil {
-		log.Warnf("error while getting %s : %s", intf, err)
+		log.Warnf("Error while getting %s : %s", intf, err)
 		return
 	}
 	log.Debugf("%s : %+v", intf, eth.Attrs().Flags)
 
-	// askAndPrint()
 	// ============================== Create the macVLAN
 
 	log.Debug("Create a new macVlan")
@@ -96,26 +101,27 @@ func main() {
 
 	link, err := netlink.LinkByName("peth0")
 	if err != nil {
-		log.Warn("error while getting macVlan :", err)
+		log.Warn("Error while getting macVlan: ", err)
 		return
 	}
 	log.Debugf("MacVlan created : %+v", link)
 
-	// askAndPrint()
 	// ============================== Create the new Namespace
 
 	newns, err := newNS()
 	if err != nil {
-		log.Warn("error while creating new NS :", err)
+		log.Warn("error while creating new NS: ", err)
 		return
 	}
-	defer delNS(newns)
+	defer deleteNS(newns)
 
 	log.Debug("Go back to original NS")
 
-	netns.Set(origns)
-
-	// askAndPrint()
+	err = netns.Set(origns)
+	if err != nil {
+		log.Warn("Failed to change the namespace: ", err)
+		return
+	}
 
 	// ============================== Add the MacVlan in the new Namespace
 
@@ -129,46 +135,62 @@ func main() {
 
 	log.Debug("Enter the namespace")
 
-	netns.Set(*newns)
+	err = netns.Set(*newns)
+	if err != nil {
+		log.Warn("Failed to enter the namespace: ", err)
+		return
+	}
 
 	// ============================= Configure the new namespace to configure it
 
 	addr, err := netlink.ParseAddr(ip)
 	if err != nil {
-		log.Warn("Failed to parse ip", err)
+		log.Warn("Failed to parse the given IP: ", err)
 		return
 	}
 
 	log.Debugf("Add the addr to the macVlan: %+v", addr)
-	netlink.AddrAdd(link, addr)
+	// ============================= Set the address in the namespace
+	err = netlink.AddrAdd(link, addr)
+	if err != nil {
+		log.Warn("Failed to add the IP to the macVlan: ", err)
+		return
+	}
 	gwaddr := net.ParseIP(gateway)
 
 	log.Debug("Set the macVlan interface UP")
+	// ============================= Set the link up in the namespace
 	err = netlink.LinkSetUp(link)
 	if err != nil {
-		log.Warn("Error while setting up the interface peth0", err)
+		log.Warn("Error while setting up the interface peth0: ", err)
 		return
 	}
 
 	log.Debugf("Set %s as the route", gwaddr)
+	// ============================= Set the default route in the namespace
 	err = netlink.RouteAdd(&netlink.Route{
 		Scope:     netlink.SCOPE_UNIVERSE,
 		LinkIndex: link.Attrs().Index,
 		Gw:        gwaddr,
 	})
 	if err != nil {
-		log.Warn("Error while setting up route on interface peth0", err)
+		log.Warn("Error while setting up route on interface peth0 :", err)
 		return
 	}
 
+	// ============================= Execute the command in the namespace
 	err = execCmd(command)
 	if err != nil {
-		log.Warn("error while checking IP", err)
+		log.Warn("Error while running command : ", err)
 	}
 
 	log.Debug("Go back to orignal namspace")
 
-	netns.Set(origns)
+	err = netns.Set(origns)
+	if err != nil {
+		log.Warn("Error while going back to the original namespace: ", err)
+		return
+	}
 
 	log.Debug("Cleaning ...")
 }
@@ -238,7 +260,7 @@ func newNS() (*netns.NsHandle, error) {
 	}
 
 	src := fmt.Sprintf("/proc/%d/ns/net", pid)
-	target := getNsName()
+	target := nsPath
 
 	log.Debugf("Create file %s", target)
 	// Create an empty file
@@ -248,9 +270,14 @@ func newNS() (*netns.NsHandle, error) {
 		return nil, err
 	}
 	// And close it
-	file.Close()
+	err = file.Close()
+	if err != nil {
+		log.Warn(err)
+		return nil, err
+	}
 
 	log.Debugf("Mount %s", target)
+
 	// Mount the namespace in /var/run/netns so it becomes a named namespace
 	if err := syscall.Mount(src, target, "proc", syscall.MS_BIND|syscall.MS_NOEXEC|syscall.MS_NOSUID|syscall.MS_NODEV, ""); err != nil {
 		return nil, err
@@ -259,33 +286,28 @@ func newNS() (*netns.NsHandle, error) {
 	return &newns, nil
 }
 
-// getNsName gets the default namespace name : w000t$PID$
-func getNsName() string {
-	pid := os.Getpid()
-	return fmt.Sprintf("/var/run/netns/w000t%d", pid)
-}
-
-func delNS(ns *netns.NsHandle) error {
+// deleteNS will delete the given namespace
+func deleteNS(ns *netns.NsHandle) error {
 	// Close the nsHandler
 	err := ns.Close()
 	if err != nil {
-		log.Warn("Error while closing", err)
+		log.Warn("Error while closing the namespace: ", err)
 		return err
 	}
 
 	// Unmount the named namespace
-	target := getNsName()
+	target := nsPath
 
 	log.Debugf("Unmounting %s", target)
 	if err := syscall.Unmount(target, 0); err != nil {
-		log.Warn("Error while unmounting", err)
+		log.Warnf("Error while unmounting %s : %s", target, err)
 		return err
 	}
 
 	// Delete the namespace file
 	log.Debugf("Deleting %s", target)
 	if err := os.Remove(target); err != nil {
-		log.Warn(err)
+		log.Warn("Error while deleting %s : %s", target, err)
 		return err
 	}