Merge plugin into weaver

This simplifies the following:

- plugin-v2 does not need to start "plugin" as a separate process, thus
  Docker is able to properly restart plugin-v2 in a case of any child
  process failing.
- No need for weaveplugin container.

plugin is enabled by default when running "weave launch". when starting
only the router, you should pass "--plugin" parameter to enable it.

The env var WEAVE_NO_PLUGIN is no more.

plugin/plugin.go

@@ -0,0 +1,116 @@
+package plugin
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"os"
+	"path"
+	"strings"
+
+	"github.com/docker/libnetwork/ipamapi"
+	weaveapi "github.com/weaveworks/weave/api"
+	"github.com/weaveworks/weave/common"
+	"github.com/weaveworks/weave/common/docker"
+	weavenet "github.com/weaveworks/weave/net"
+	ipamplugin "github.com/weaveworks/weave/plugin/ipam"
+	netplugin "github.com/weaveworks/weave/plugin/net"
+	"github.com/weaveworks/weave/plugin/skel"
+)
+
+var Log = common.Log
+
+func Start(weaveAPIAddr string, dockerAPIAddr string, address string, meshAddress string, noMulticastRoute bool) {
+	weave := weaveapi.NewClient(weaveAPIAddr, Log)
+
+	var dockerClient *docker.Client
+	var err error
+	if dockerAPIAddr != "" {
+		// API 1.21 is the first version that supports docker network commands
+		dockerClient, err = docker.NewVersionedClient(dockerAPIAddr, "1.21")
+		if err != nil {
+			Log.Fatalf("unable to connect to docker: %s", err)
+		}
+	}
+
+	if noMulticastRoute {
+		Log.Warning("--no-multicast-route option has been removed; multicast is off by default")
+	}
+	if dockerClient == nil {
+		Log.Info("Running without Docker API connection")
+	} else {
+		Log.Info(dockerClient.Info())
+	}
+
+	Log.Info("Waiting for Weave API Server...")
+	weave.WaitAPIServer(30)
+	Log.Info("Finished waiting for Weave API Server")
+
+	err = run(dockerClient, weave, address, meshAddress)
+	if err != nil {
+		Log.Fatal(err)
+	}
+}
+
+func run(dockerClient *docker.Client, weave *weaveapi.Client, address, meshAddress string) error {
+	endChan := make(chan error, 1)
+
+	if address != "" {
+		globalListener, err := listenAndServe(dockerClient, weave, address, endChan, "global", false)
+		if err != nil {
+			return err
+		}
+		defer os.Remove(address)
+		defer globalListener.Close()
+	}
+	if meshAddress != "" {
+		meshListener, err := listenAndServe(dockerClient, weave, meshAddress, endChan, "local", true)
+		if err != nil {
+			return err
+		}
+		defer os.Remove(meshAddress)
+		defer meshListener.Close()
+	}
+
+	statusListener, err := weavenet.ListenUnixSocket("/home/weave/plugin-status.sock")
+	if err != nil {
+		return err
+	}
+	go serveStatus(statusListener)
+
+	return <-endChan
+}
+
+func listenAndServe(dockerClient *docker.Client, weave *weaveapi.Client, address string, endChan chan<- error, scope string, withIpam bool) (net.Listener, error) {
+	name := strings.TrimSuffix(path.Base(address), ".sock")
+	d, err := netplugin.New(dockerClient, weave, name, scope)
+	if err != nil {
+		return nil, err
+	}
+
+	var i ipamapi.Ipam
+	if withIpam {
+		i = ipamplugin.NewIpam(weave)
+	}
+
+	listener, err := weavenet.ListenUnixSocket(address)
+	if err != nil {
+		return nil, err
+	}
+	Log.Printf("Listening on %s for %s scope", address, scope)
+
+	go func() {
+		endChan <- skel.Listen(listener, d, i)
+	}()
+
+	return listener, nil
+}
+
+func serveStatus(listener net.Listener) {
+	server := &http.Server{Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintln(w, "ok")
+	})}
+	if err := server.Serve(listener); err != nil {
+		Log.Fatalf("ListenAndServeStatus failed: %s", err)
+	}
+}