Add plugin code

This adds basic plugins.
"main" types: veth, bridge, macvlan
"ipam" type: host-local

The code has been ported over from github.com/coreos/rkt project
and adapted to fit the CNI spec.

pkg/plugin/ipam.go

@@ -0,0 +1,136 @@
+// 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 plugin
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/appc/cni/Godeps/_workspace/src/github.com/vishvananda/netlink"
+	"github.com/appc/cni/pkg/ip"
+)
+
+// Find returns the full path of the plugin by searching in CNI_PATH
+func Find(plugin string) string {
+	paths := strings.Split(os.Getenv("CNI_PATH"), ":")
+
+	for _, p := range paths {
+		fullname := filepath.Join(p, plugin)
+		if fi, err := os.Stat(fullname); err == nil && fi.Mode().IsRegular() {
+			return fullname
+		}
+	}
+
+	return ""
+}
+
+// ExecAdd executes IPAM plugin, assuming CNI_COMMAND == ADD.
+// Parses and returns resulting IPConfig
+func ExecAdd(plugin string, netconf []byte) (*Result, error) {
+	if os.Getenv("CNI_COMMAND") != "ADD" {
+		return nil, fmt.Errorf("CNI_COMMAND is not ADD")
+	}
+
+	pluginPath := Find(plugin)
+	if pluginPath == "" {
+		return nil, fmt.Errorf("could not find %q plugin", plugin)
+	}
+
+	stdout := &bytes.Buffer{}
+
+	c := exec.Cmd{
+		Path:   pluginPath,
+		Args:   []string{pluginPath},
+		Stdin:  bytes.NewBuffer(netconf),
+		Stdout: stdout,
+		Stderr: os.Stderr,
+	}
+	if err := c.Run(); err != nil {
+		return nil, err
+	}
+
+	res := &Result{}
+	err := json.Unmarshal(stdout.Bytes(), res)
+	return res, err
+}
+
+// ExecDel executes IPAM plugin, assuming CNI_COMMAND == DEL.
+func ExecDel(plugin string, netconf []byte) error {
+	if os.Getenv("CNI_COMMAND") != "DEL" {
+		return fmt.Errorf("CNI_COMMAND is not DEL")
+	}
+
+	pluginPath := Find(plugin)
+	if pluginPath == "" {
+		return fmt.Errorf("could not find %q plugin", plugin)
+	}
+
+	c := exec.Cmd{
+		Path:   pluginPath,
+		Args:   []string{pluginPath},
+		Stdin:  bytes.NewBuffer(netconf),
+		Stderr: os.Stderr,
+	}
+	return c.Run()
+}
+
+// ConfigureIface takes the result of IPAM plugin and
+// applies to the ifName interface
+func ConfigureIface(ifName string, res *Result) error {
+	link, err := netlink.LinkByName(ifName)
+	if err != nil {
+		return fmt.Errorf("failed to lookup %q: %v", ifName, err)
+	}
+
+	if err := netlink.LinkSetUp(link); err != nil {
+		return fmt.Errorf("failed too set %q UP: %v", ifName, err)
+	}
+
+	// TODO(eyakubovich): IPv6
+	addr := &netlink.Addr{IPNet: &res.IP4.IP, Label: ""}
+	if err = netlink.AddrAdd(link, addr); err != nil {
+		return fmt.Errorf("failed to add IP addr to %q: %v", ifName, err)
+	}
+
+	for _, r := range res.IP4.Routes {
+		gw := r.GW
+		if gw == nil {
+			gw = res.IP4.Gateway
+		}
+		if err = ip.AddRoute(&r.Dst, gw, link); err != nil {
+			// we skip over duplicate routes as we assume the first one wins
+			if !os.IsExist(err) {
+				return fmt.Errorf("failed to add route '%v via %v dev %v': %v", r.Dst, gw, ifName, err)
+			}
+		}
+	}
+
+	return nil
+}
+
+// PrintResult writes out prettified Result to stdout
+func PrintResult(res *Result) error {
+	data, err := json.MarshalIndent(res, "", "    ")
+	if err != nil {
+		return err
+	}
+	_, err = os.Stdout.Write(data)
+	return err
+}