use netlink instead of ip commands to set address/mtu and bring up the tuntap device on linux

src/yggdrasil/tun_linux.go

@@ -3,12 +3,14 @@ package yggdrasil
 // The linux platform specific tun parts
 // It depends on iproute2 being installed to set things on the tun device
 
+import "errors"
 import "fmt"
-import "os/exec"
-import "strings"
+import "net"
 
 import water "github.com/neilalexander/water"
 
+import "github.com/docker/libcontainer/netlink"
+
 func getDefaults() tunDefaultParameters {
 	return tunDefaultParameters{
 		maximumIfMTU:     65535,
@@ -39,26 +41,33 @@ func (tun *tunDevice) setup(ifname string, iftapmode bool, addr string, mtu int)
 
 func (tun *tunDevice) setupAddress(addr string) error {
 	// Set address
-	cmd := exec.Command("ip", "-f", "inet6",
-		"addr", "add", addr,
-		"dev", tun.iface.Name())
-	tun.core.log.Printf("ip command: %v", strings.Join(cmd.Args, " "))
-	output, err := cmd.CombinedOutput()
+	var netIF *net.Interface
+	ifces, err := net.Interfaces()
 	if err != nil {
-		tun.core.log.Printf("Linux ip failed: %v.", err)
-		tun.core.log.Println(string(output))
 		return err
 	}
-	// Set MTU and bring device up
-	cmd = exec.Command("ip", "link", "set",
-		"dev", tun.iface.Name(),
-		"mtu", fmt.Sprintf("%d", tun.mtu),
-		"up")
-	tun.core.log.Printf("ip command: %v", strings.Join(cmd.Args, " "))
-	output, err = cmd.CombinedOutput()
+	for _, ifce := range ifces {
+		if ifce.Name == tun.iface.Name() {
+			netIF = &ifce
+		}
+	}
+	if netIF == nil {
+		return errors.New(fmt.Sprintf("Failed to find interface: %s", tun.iface.Name()))
+	}
+	ip, ipNet, err := net.ParseCIDR(addr)
+	if err != nil {
+		return err
+	}
+	err = netlink.NetworkLinkAddIp(netIF, ip, ipNet)
+	if err != nil {
+		return err
+	}
+	err = netlink.NetworkSetMTU(netIF, tun.mtu)
+	if err != nil {
+		return err
+	}
+	netlink.NetworkLinkUp(netIF)
 	if err != nil {
-		tun.core.log.Printf("Linux ip failed: %v.", err)
-		tun.core.log.Println(string(output))
 		return err
 	}
 	return nil