func configureIface(ifname string, ipn ip.IP4Net, mtu int) error { iface, err := net.InterfaceByName(ifname) if err != nil { log.Error("Failed to lookup interface ", ifname) return err } n := ipn.ToIPNet() err = netlink.NetworkLinkAddIp(iface, n.IP, n) if err != nil { log.Errorf("Failed to add IP address %s to %s: %s", n.IP, ifname, err) return err } err = netlink.NetworkSetMTU(iface, mtu) if err != nil { log.Errorf("Failed to set MTU for %s: %v", ifname, err) return err } err = netlink.NetworkLinkUp(iface) if err != nil { log.Errorf("Failed to set interface %s to UP state: %s", ifname, err) return err } // explicitly add a route since there might be a route for a subnet already // installed by Docker and then it won't get auto added err = netlink.AddRoute(ipn.Network().String(), "", "", ifname) if err != nil && err != syscall.EEXIST { log.Errorf("Failed to add route (%s -> %s): %v", ipn.Network().String(), ifname, err) return err } return nil }