Set interfaces routes after the interface is up

Fixes #485

The code previously relied on an uninteded side effect. When the
interface name was set, this causes the interface to come up
prematurely. Once that side effect was removed, routes could
no longer be set.

This change ensures that routes are only set after the interface
is brought up.

Signed-off-by: Tom Denham <tom@tomdee.co.uk>

osl/interface_linux.go

@@ -271,6 +271,11 @@ func (n *networkNamespace) AddInterface(srcName, dstPrefix string, options ...If
 			return fmt.Errorf("failed to set link up: %v", err)
 		}
 
+		// Set the routes on the interface. This can only be done when the interface is up.
+		if err := setInterfaceRoutes(iface, i); err != nil {
+			return fmt.Errorf("error setting interface %q routes to %q: %v", iface.Attrs().Name, i.Routes(), err)
+		}
+
 		n.Lock()
 		n.iFaces = append(n.iFaces, i)
 		n.Unlock()
@@ -288,7 +293,6 @@ func configureInterface(iface netlink.Link, i *nwIface) error {
 		{setInterfaceName, fmt.Sprintf("error renaming interface %q to %q", ifaceName, i.DstName())},
 		{setInterfaceIP, fmt.Sprintf("error setting interface %q IP to %q", ifaceName, i.Address())},
 		{setInterfaceIPv6, fmt.Sprintf("error setting interface %q IPv6 to %q", ifaceName, i.AddressIPv6())},
-		{setInterfaceRoutes, fmt.Sprintf("error setting interface %q routes to %q", ifaceName, i.Routes())},
 		{setInterfaceMaster, fmt.Sprintf("error setting interface %q master to %q", ifaceName, i.DstMaster())},
 	}
 
@@ -346,7 +350,7 @@ func setInterfaceRoutes(iface netlink.Link, i *nwIface) error {
 
 // In older kernels (like the one in Centos 6.6 distro) sysctl does not have netns support. Therefore
 // we cannot gather the statistics from /sys/class/net/<dev>/statistics/<counter> files. Per-netns stats
-// are naturally found in /proc/net/dev in kernels which support netns (ifconfig relyes on that).
+// are naturally found in /proc/net/dev in kernels which support netns (ifconfig relies on that).
 const (
 	netStatsFile = "/proc/net/dev"
 	base         = "[ ]*%s:([ ]+[0-9]+){16}"