plugins: add ipvlan main plugin

Add the ipvlan main plugin which is heavily based on the macvlan plugin.
Availabile modes for this plugin are l2 and l3, wheres l2 has the higher
compatibility due to support for multicast and broadcasts. L2 has therefore been
chosen as the default mode.
See the official docs at
https://www.kernel.org/doc/Documentation/networking/ipvlan.txt
for more information.

Fixes #6.

plugins/main/ipvlan/ipvlan.go

@@ -0,0 +1,173 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"runtime"
+
+	"github.com/appc/cni/Godeps/_workspace/src/github.com/vishvananda/netlink"
+	"github.com/appc/cni/pkg/ip"
+	"github.com/appc/cni/pkg/ns"
+	"github.com/appc/cni/pkg/plugin"
+	"github.com/appc/cni/pkg/skel"
+)
+
+type NetConf struct {
+	plugin.NetConf
+	Master string `json:"master"`
+	Mode   string `json:"mode"`
+	IPMasq bool   `json:"ipMasq"`
+	MTU    int    `json:"mtu"`
+}
+
+func init() {
+	// this ensures that main runs only on main thread (thread group leader).
+	// since namespace ops (unshare, setns) are done for a single thread, we
+	// must ensure that the goroutine does not jump from OS thread to thread
+	runtime.LockOSThread()
+}
+
+func loadConf(bytes []byte) (*NetConf, error) {
+	n := &NetConf{}
+	if err := json.Unmarshal(bytes, n); err != nil {
+		return nil, fmt.Errorf("failed to load netconf: %v", err)
+	}
+	if n.Master == "" {
+		return nil, fmt.Errorf(`"master" field is required. It specifies the host interface name to virtualize`)
+	}
+	return n, nil
+}
+
+func modeFromString(s string) (netlink.IPVlanMode, error) {
+	switch s {
+	case "":
+		return netlink.IPVLAN_MODE_L2, nil
+	case "l2":
+		return netlink.IPVLAN_MODE_L2, nil
+	case "l3":
+		return netlink.IPVLAN_MODE_L3, nil
+	default:
+		return 0, fmt.Errorf("unknown ipvlan mode: %q", s)
+	}
+}
+
+func createIpvlan(conf *NetConf, ifName string, netns *os.File) error {
+	mode, err := modeFromString(conf.Mode)
+	if err != nil {
+		return err
+	}
+
+	m, err := netlink.LinkByName(conf.Master)
+	if err != nil {
+		return fmt.Errorf("failed to lookup master %q: %v", conf.Master, err)
+	}
+
+	mv := &netlink.IPVlan{
+		LinkAttrs: netlink.LinkAttrs{
+			MTU:         conf.MTU,
+			Name:        ifName,
+			ParentIndex: m.Attrs().Index,
+			Namespace:   netlink.NsFd(int(netns.Fd())),
+		},
+		Mode: mode,
+	}
+
+	if err := netlink.LinkAdd(mv); err != nil {
+		return fmt.Errorf("failed to create ipvlan: %v", err)
+	}
+
+	return err
+}
+
+func cmdAdd(args *skel.CmdArgs) error {
+	n, err := loadConf(args.StdinData)
+	if err != nil {
+		return err
+	}
+
+	netns, err := os.Open(args.Netns)
+	if err != nil {
+		return fmt.Errorf("failed to open netns %q: %v", netns, err)
+	}
+	defer netns.Close()
+
+	tmpName := ip.RandomVethName(args.Netns)
+	if err = createIpvlan(n, tmpName, netns); err != nil {
+		return err
+	}
+
+	// run the IPAM plugin and get back the config to apply
+	result, err := plugin.ExecAdd(n.IPAM.Type, args.StdinData)
+	if err != nil {
+		return err
+	}
+	if result.IP4 == nil {
+		return errors.New("IPAM plugin returned missing IPv4 config")
+	}
+
+	err = ns.WithNetNS(netns, func(_ *os.File) error {
+		err := renameLink(tmpName, args.IfName)
+		if err != nil {
+			return fmt.Errorf("failed to rename ipvlan to %q: %v", args.IfName, err)
+		}
+
+		return plugin.ConfigureIface(args.IfName, result)
+	})
+	if err != nil {
+		return err
+	}
+
+	if n.IPMasq {
+		chain := "CNI-" + n.Name
+		if err = ip.SetupIPMasq(ip.Network(&result.IP4.IP), chain); err != nil {
+			return err
+		}
+	}
+
+	return plugin.PrintResult(result)
+}
+
+func cmdDel(args *skel.CmdArgs) error {
+	n, err := loadConf(args.StdinData)
+	if err != nil {
+		return err
+	}
+
+	err = plugin.ExecDel(n.IPAM.Type, args.StdinData)
+	if err != nil {
+		return err
+	}
+
+	return ns.WithNetNSPath(args.Netns, func(hostNS *os.File) error {
+		return ip.DelLinkByName(args.IfName)
+	})
+}
+
+func renameLink(curName, newName string) error {
+	link, err := netlink.LinkByName(curName)
+	if err != nil {
+		return err
+	}
+
+	return netlink.LinkSetName(link, newName)
+}
+
+func main() {
+	skel.PluginMain(cmdAdd, cmdDel)
+}