Rename veth plugin to ptp and add docs.

ptp (point-to-point) better describes the nature of the plugin
as veth pairs are also used by the bridge plugin.

plugins/main/ptp/ptp.go

@@ -0,0 +1,160 @@
+// 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 (
+	"crypto/sha512"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net"
+	"os"
+	"runtime"
+
+	"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"
+)
+
+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()
+}
+
+type NetConf struct {
+	plugin.NetConf
+	IPMasq bool `json:"ipMasq"`
+	MTU    int  `json:"mtu"`
+}
+
+func setupContainerVeth(netns, ifName string, mtu int, pr *plugin.Result) (string, error) {
+	var hostVethName string
+	err := ns.WithNetNSPath(netns, false, func(hostNS *os.File) error {
+		hostVeth, _, err := ip.SetupVeth(ifName, mtu, hostNS)
+		if err != nil {
+			return err
+		}
+
+		err = plugin.ConfigureIface(ifName, pr)
+		if err != nil {
+			return err
+		}
+
+		hostVethName = hostVeth.Attrs().Name
+
+		return nil
+	})
+	return hostVethName, err
+}
+
+func setupHostVeth(vethName string, ipConf *plugin.IPConfig) error {
+	// hostVeth moved namespaces and may have a new ifindex
+	veth, err := netlink.LinkByName(vethName)
+	if err != nil {
+		return fmt.Errorf("failed to lookup %q: %v", vethName, err)
+	}
+
+	// TODO(eyakubovich): IPv6
+	ipn := &net.IPNet{
+		IP:   ipConf.Gateway,
+		Mask: net.CIDRMask(31, 32),
+	}
+	addr := &netlink.Addr{IPNet: ipn, Label: ""}
+	if err = netlink.AddrAdd(veth, addr); err != nil {
+		return fmt.Errorf("failed to add IP addr (%#v) to veth: %v", ipn, err)
+	}
+
+	// dst happens to be the same as IP/net of host veth
+	if err = ip.AddHostRoute(ipn, nil, veth); err != nil && !os.IsExist(err) {
+		return fmt.Errorf("failed to add route on host: %v", err)
+	}
+
+	return nil
+}
+
+func cmdAdd(args *skel.CmdArgs) error {
+	conf := NetConf{}
+	if err := json.Unmarshal(args.StdinData, &conf); err != nil {
+		return fmt.Errorf("failed to load netconf: %v", err)
+	}
+
+	if err := ip.EnableIP4Forward(); err != nil {
+		return fmt.Errorf("failed to enable forwarding: %v", err)
+	}
+
+	// run the IPAM plugin and get back the config to apply
+	result, err := plugin.ExecAdd(conf.IPAM.Type, args.StdinData)
+	if err != nil {
+		return err
+	}
+	if result.IP4 == nil {
+		return errors.New("IPAM plugin returned missing IPv4 config")
+	}
+
+	hostVethName, err := setupContainerVeth(args.Netns, args.IfName, conf.MTU, result)
+	if err != nil {
+		return err
+	}
+
+	if err = setupHostVeth(hostVethName, result.IP4); err != nil {
+		return err
+	}
+
+	if conf.IPMasq {
+		h := sha512.Sum512([]byte(args.ContainerID))
+		chain := fmt.Sprintf("CNI-%s-%x", conf.Name, h[:8])
+		if err = ip.SetupIPMasq(&result.IP4.IP, chain); err != nil {
+			return err
+		}
+	}
+
+	return result.Print()
+}
+
+func cmdDel(args *skel.CmdArgs) error {
+	conf := NetConf{}
+	if err := json.Unmarshal(args.StdinData, &conf); err != nil {
+		return fmt.Errorf("failed to load netconf: %v", err)
+	}
+
+	var ipn *net.IPNet
+	err := ns.WithNetNSPath(args.Netns, false, func(hostNS *os.File) error {
+		var err error
+		ipn, err = ip.DelLinkByNameAddr(args.IfName, netlink.FAMILY_V4)
+		return err
+	})
+	if err != nil {
+		return err
+	}
+
+	if conf.IPMasq {
+		h := sha512.Sum512([]byte(args.ContainerID))
+		chain := fmt.Sprintf("CNI-%s-%x", conf.Name, h[:8])
+		if err = ip.TeardownIPMasq(ipn, chain); err != nil {
+			return err
+		}
+	}
+
+	return plugin.ExecDel(conf.IPAM.Type, args.StdinData)
+}
+
+func main() {
+	skel.PluginMain(cmdAdd, cmdDel)
+}