added host-device plugin which adds a specified link to the container network namespace;

plugins/host-device/host-device.go

@@ -0,0 +1,106 @@
+// Copyright 2015 CNI authors
+//
+// 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"
+	"fmt"
+	"runtime"
+
+	"github.com/containernetworking/cni/pkg/ns"
+	"github.com/containernetworking/cni/pkg/skel"
+	"github.com/containernetworking/cni/pkg/version"
+	"github.com/vishvananda/netlink"
+)
+
+type NetConf struct {
+	Device string `json:"device"`
+}
+
+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.Device == "" {
+		return nil, fmt.Errorf(`"device" field is required. It specifies the host device to put into the pod`)
+	}
+	return n, nil
+}
+
+func cmdAdd(args *skel.CmdArgs) error {
+	cfg, err := loadConf(args.StdinData)
+	if err != nil {
+		return err
+	}
+	containerNs, err := ns.GetNS(args.Netns)
+	if err != nil {
+		return fmt.Errorf("failed to open netns %q: %v", args.Netns, err)
+	}
+	defer containerNs.Close()
+	return addLink(cfg.Device, containerNs)
+}
+
+func cmdDel(args *skel.CmdArgs) error {
+	cfg, err := loadConf(args.StdinData)
+	if err != nil {
+		return err
+	}
+	containerNs, err := ns.GetNS(args.Netns)
+	if err != nil {
+		return fmt.Errorf("failed to open netns %q: %v", args.Netns, err)
+	}
+	defer containerNs.Close()
+	return removeLink(cfg.Device, containerNs)
+}
+
+func addLink(name string, containerNs ns.NetNS) error {
+	dev, err := netlink.LinkByName(name)
+	if err != nil {
+		return fmt.Errorf("failed to lookup %v: %v", name, err)
+	}
+	return netlink.LinkSetNsFd(dev, int(containerNs.Fd()))
+}
+
+func removeLink(name string, containerNs ns.NetNS) error {
+	var dev netlink.Link
+	err := containerNs.Do(func(_ ns.NetNS) error {
+		d, err := netlink.LinkByName(name)
+		if err != nil {
+			return err
+		}
+		dev = d
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	defaultNs, err := ns.GetCurrentNS()
+	if err != nil {
+		return err
+	}
+	return netlink.LinkSetNsFd(dev, int(defaultNs.Fd()))
+}
+
+func main() {
+	skel.PluginMain(cmdAdd, cmdDel, version.All)
+}