Merge pull request #1724 from weaveworks/1674-move-plugin

Move Weave docker plugin into this repo

.gitignore

@@ -42,12 +42,14 @@ prog/weavewait/weavewait
 prog/weavewait/weavewait_noop
 prog/netcheck/netcheck
 prog/docker_tls_args/docker_tls_args
+prog/plugin/plugin
 testing/cover/cover
 testing/runner/runner
 releases
 .weaver.uptodate
 .weavedns.uptodate
 .weaveexec.uptodate
+.dockerplugin.uptodate
 weave.tar.gz
 prog/weaveexec/weave
 prog/weaveexec/weavehosts

Makefile

@@ -16,19 +16,22 @@ WEAVEWAIT_EXE=prog/weavewait/weavewait
 WEAVEWAIT_NOOP_EXE=prog/weavewait/weavewait_noop
 NETCHECK_EXE=prog/netcheck/netcheck
 DOCKERTLSARGS_EXE=prog/docker_tls_args/docker_tls_args
+DOCKERPLUGIN_EXE=prog/plugin/plugin
 RUNNER_EXE=tools/runner/runner
 
-EXES=$(WEAVER_EXE) $(SIGPROXY_EXE) $(WEAVEPROXY_EXE) $(WEAVEWAIT_EXE) $(WEAVEWAIT_NOOP_EXE) $(NETCHECK_EXE) $(DOCKERTLSARGS_EXE)
+EXES=$(WEAVER_EXE) $(SIGPROXY_EXE) $(WEAVEPROXY_EXE) $(WEAVEWAIT_EXE) $(WEAVEWAIT_NOOP_EXE) $(NETCHECK_EXE) $(DOCKERTLSARGS_EXE) $(DOCKERPLUGIN_EXE)
 
 WEAVER_UPTODATE=.weaver.uptodate
 WEAVEEXEC_UPTODATE=.weaveexec.uptodate
+DOCKERPLUGIN_UPTODATE=.dockerplugin.uptodate
 
-IMAGES_UPTODATE=$(WEAVER_UPTODATE) $(WEAVEEXEC_UPTODATE)
+IMAGES_UPTODATE=$(WEAVER_UPTODATE) $(WEAVEEXEC_UPTODATE) $(DOCKERPLUGIN_UPTODATE)
 
 WEAVER_IMAGE=$(DOCKERHUB_USER)/weave
 WEAVEEXEC_IMAGE=$(DOCKERHUB_USER)/weaveexec
+DOCKERPLUGIN_IMAGE=$(DOCKERHUB_USER)/plugin
 
-IMAGES=$(WEAVER_IMAGE) $(WEAVEEXEC_IMAGE)
+IMAGES=$(WEAVER_IMAGE) $(WEAVEEXEC_IMAGE) $(DOCKERPLUGIN_IMAGE)
 
 WEAVE_EXPORT=weave.tar.gz
 
@@ -74,13 +77,14 @@ $(WEAVER_EXE): router/*.go mesh/*.go ipam/*.go ipam/*/*.go nameserver/*.go prog/
 $(WEAVEPROXY_EXE): proxy/*.go prog/weaveproxy/main.go
 $(NETCHECK_EXE): prog/netcheck/netcheck.go
 
-# Sigproxy and weavewait need separate rules as they fail the netgo check in
+# These next programs need separate rules as they fail the netgo check in
 # the main build stanza due to not importing net package
 $(SIGPROXY_EXE): prog/sigproxy/main.go
 $(WEAVEWAIT_EXE): prog/weavewait/*.go net/*.go
 $(DOCKERTLSARGS_EXE): prog/docker_tls_args/*.go
+$(DOCKERPLUGIN_EXE): prog/plugin/*.go plugin/*.go plugin/skel/*.go
 
-$(WEAVEWAIT_EXE) $(SIGPROXY_EXE) $(DOCKERTLSARGS_EXE):
+$(WEAVEWAIT_EXE) $(SIGPROXY_EXE) $(DOCKERTLSARGS_EXE) $(DOCKERPLUGIN_EXE):
 	go get -tags netgo ./$(@D)
 	go build $(BUILD_FLAGS) -o $@ ./$(@D)
 
@@ -104,6 +108,10 @@ $(WEAVEEXEC_UPTODATE): prog/weaveexec/Dockerfile $(DOCKER_DISTRIB) weave $(SIGPR
 	$(SUDO) docker build -t $(WEAVEEXEC_IMAGE) prog/weaveexec
 	touch $@
 
+$(DOCKERPLUGIN_UPTODATE): prog/plugin/Dockerfile $(DOCKERPLUGIN_EXE)
+	$(SUDO) docker build -t $(DOCKERPLUGIN_IMAGE) prog/plugin
+	touch $@
+
 $(WEAVE_EXPORT): $(IMAGES_UPTODATE)
 	$(SUDO) docker save $(addsuffix :latest,$(IMAGES)) | gzip > $@
 

plugin/dns.go

@@ -0,0 +1,55 @@
+package plugin
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+func (d *dockerer) registerWithDNS(ID string, fqdn string, ip string) error {
+	dnsip, err := d.getContainerBridgeIP(WeaveDNSContainer)
+	if err != nil {
+		return fmt.Errorf("nameserver not available: %s", err)
+	}
+	data := url.Values{}
+	data.Add("fqdn", fqdn)
+
+	req, err := http.NewRequest("PUT", fmt.Sprintf("http://%s:6785/name/%s/%s", dnsip, ID, ip), strings.NewReader(data.Encode()))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+
+	cl := &http.Client{}
+	res, err := cl.Do(req)
+	if err != nil {
+		return err
+	}
+	if res.StatusCode != http.StatusOK {
+		return fmt.Errorf("non-OK status from nameserver: %d", res.StatusCode)
+	}
+	return nil
+}
+
+func (d *dockerer) deregisterWithDNS(ID string, ip string) error {
+	dnsip, err := d.getContainerBridgeIP(WeaveDNSContainer)
+	if err != nil {
+		return fmt.Errorf("nameserver not available: %s", err)
+	}
+
+	req, err := http.NewRequest("DELETE", fmt.Sprintf("http://%s:6785/name/%s/%s", dnsip, ID, ip), nil)
+	if err != nil {
+		return err
+	}
+
+	cl := &http.Client{}
+	res, err := cl.Do(req)
+	if err != nil {
+		return err
+	}
+	if res.StatusCode != http.StatusOK {
+		return fmt.Errorf("non-OK status from nameserver: %d", res.StatusCode)
+	}
+	return nil
+}

plugin/docker.go

@@ -0,0 +1,23 @@
+package plugin
+
+import (
+	"github.com/fsouza/go-dockerclient"
+	. "github.com/weaveworks/weave/common"
+)
+
+type dockerer struct {
+	client *docker.Client
+}
+
+func (d *dockerer) getContainerBridgeIP(nameOrID string) (string, error) {
+	Log.Debugf("Getting IP for container %s", nameOrID)
+	info, err := d.InspectContainer(nameOrID)
+	if err != nil {
+		return "", err
+	}
+	return info.NetworkSettings.IPAddress, nil
+}
+
+func (d *dockerer) InspectContainer(nameOrId string) (*docker.Container, error) {
+	return d.client.InspectContainer(nameOrId)
+}

plugin/driver.go

@@ -0,0 +1,183 @@
+package plugin
+
+import (
+	"fmt"
+
+	"github.com/docker/libnetwork/drivers/remote/api"
+	"github.com/docker/libnetwork/types"
+
+	. "github.com/weaveworks/weave/common"
+	"github.com/weaveworks/weave/common/odp"
+	"github.com/weaveworks/weave/plugin/skel"
+
+	docker "github.com/fsouza/go-dockerclient"
+	"github.com/vishvananda/netlink"
+)
+
+const (
+	WeaveContainer = "weave"
+	WeaveBridge    = "weave"
+)
+
+type driver struct {
+	version    string
+	nameserver string
+}
+
+func New(version string, nameserver string) (skel.Driver, error) {
+	client, err := docker.NewClient("unix:///var/run/docker.sock")
+	if err != nil {
+		return nil, errorf("could not connect to docker: %s", err)
+	}
+
+	_, err = NewWatcher(client)
+	if err != nil {
+		return nil, err
+	}
+
+	return &driver{
+		nameserver: nameserver,
+		version:    version,
+	}, nil
+}
+
+func errorf(format string, a ...interface{}) error {
+	Log.Errorf(format, a...)
+	return fmt.Errorf(format, a...)
+}
+
+// === protocol handlers
+
+var caps = &api.GetCapabilityResponse{
+	Scope: "global",
+}
+
+func (driver *driver) GetCapabilities() (*api.GetCapabilityResponse, error) {
+	Log.Debugf("Get capabilities: responded with %+v", caps)
+	return caps, nil
+}
+
+func (driver *driver) CreateNetwork(create *api.CreateNetworkRequest) error {
+	Log.Debugf("Create network request %+v", create)
+	Log.Infof("Create network %s", create.NetworkID)
+	return nil
+}
+
+func (driver *driver) DeleteNetwork(delete *api.DeleteNetworkRequest) error {
+	Log.Debugf("Delete network request: %+v", delete)
+	Log.Infof("Destroy network %s", delete.NetworkID)
+	return nil
+}
+
+func (driver *driver) CreateEndpoint(create *api.CreateEndpointRequest) (*api.CreateEndpointResponse, error) {
+	Log.Debugf("Create endpoint request %+v", create)
+	endID := create.EndpointID
+
+	if create.Interface == nil {
+		return nil, fmt.Errorf("Not supported: creating an interface from within CreateEndpoint")
+	}
+	resp := &api.CreateEndpointResponse{}
+
+	Log.Infof("Create endpoint %s %+v", endID, resp)
+	return resp, nil
+}
+
+func (driver *driver) DeleteEndpoint(delete *api.DeleteEndpointRequest) error {
+	Log.Debugf("Delete endpoint request: %+v", delete)
+	Log.Infof("Delete endpoint %s", delete.EndpointID)
+	return nil
+}
+
+func (driver *driver) EndpointInfo(req *api.EndpointInfoRequest) (*api.EndpointInfoResponse, error) {
+	Log.Debugf("Endpoint info request: %+v", req)
+	Log.Infof("Endpoint info %s", req.EndpointID)
+	return &api.EndpointInfoResponse{Value: map[string]interface{}{}}, nil
+}
+
+func (driver *driver) JoinEndpoint(j *api.JoinRequest) (*api.JoinResponse, error) {
+	endID := j.EndpointID
+
+	maybeBridge, err := netlink.LinkByName(WeaveBridge)
+	if err != nil {
+		return nil, errorf(`bridge "%s" not present; did you launch weave?`, WeaveBridge)
+	}
+
+	// create and attach local name to the bridge
+	local := vethPair(endID[:5])
+	local.Attrs().MTU = maybeBridge.Attrs().MTU
+	if err := netlink.LinkAdd(local); err != nil {
+		return nil, errorf("could not create veth pair: %s", err)
+	}
+
+	switch maybeBridge.(type) {
+	case *netlink.Bridge:
+		if err := netlink.LinkSetMasterByIndex(local, maybeBridge.Attrs().Index); err != nil {
+			return nil, errorf(`unable to set master: %s`, err)
+		}
+	case *netlink.GenericLink:
+		if maybeBridge.Type() != "openvswitch" {
+			Log.Errorf("device %s is %+v", WeaveBridge, maybeBridge)
+			return nil, errorf(`device "%s" is of type "%s"`, WeaveBridge, maybeBridge.Type())
+		}
+		odp.AddDatapathInterface(WeaveBridge, local.Name)
+	case *netlink.Device:
+		Log.Warnf("kernel does not report what kind of device %s is, just %+v", WeaveBridge, maybeBridge)
+		// Assume it's our openvswitch device, and the kernel has not been updated to report the kind.
+		odp.AddDatapathInterface(WeaveBridge, local.Name)
+	default:
+		Log.Errorf("device %s is %+v", WeaveBridge, maybeBridge)
+		return nil, errorf(`device "%s" not a bridge`, WeaveBridge)
+	}
+	if err := netlink.LinkSetUp(local); err != nil {
+		return nil, errorf(`unable to bring veth up: %s`, err)
+	}
+
+	ifname := &api.InterfaceName{
+		SrcName:   local.PeerName,
+		DstPrefix: "ethwe",
+	}
+
+	response := &api.JoinResponse{
+		InterfaceName: ifname,
+	}
+	if driver.nameserver != "" {
+		routeToDNS := api.StaticRoute{
+			Destination: driver.nameserver + "/32",
+			RouteType:   types.CONNECTED,
+			NextHop:     "",
+		}
+		response.StaticRoutes = []api.StaticRoute{routeToDNS}
+	}
+	Log.Infof("Join endpoint %s:%s to %s", j.NetworkID, j.EndpointID, j.SandboxKey)
+	return response, nil
+}
+
+func (driver *driver) LeaveEndpoint(leave *api.LeaveRequest) error {
+	Log.Debugf("Leave request: %+v", leave)
+
+	local := vethPair(leave.EndpointID[:5])
+	if err := netlink.LinkDel(local); err != nil {
+		Log.Warningf("unable to delete veth on leave: %s", err)
+	}
+	Log.Infof("Leave %s:%s", leave.NetworkID, leave.EndpointID)
+	return nil
+}
+
+func (driver *driver) DiscoverNew(disco *api.DiscoveryNotification) error {
+	Log.Debugf("Dicovery new notification: %+v", disco)
+	return nil
+}
+
+func (driver *driver) DiscoverDelete(disco *api.DiscoveryNotification) error {
+	Log.Debugf("Dicovery delete notification: %+v", disco)
+	return nil
+}
+
+// ===
+
+func vethPair(suffix string) *netlink.Veth {
+	return &netlink.Veth{
+		LinkAttrs: netlink.LinkAttrs{Name: "vethwl" + suffix},
+		PeerName:  "vethwg" + suffix,
+	}
+}

plugin/ipam.go

@@ -0,0 +1,89 @@
+package plugin
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+
+	. "github.com/weaveworks/weave/common"
+)
+
+func (d *dockerer) ipamOp(ID string, op string) (*net.IPNet, error) {
+	weaveip, err := d.getContainerBridgeIP(WeaveContainer)
+	Log.Debugf("IPAM operation %s for %s", op, ID)
+	if err != nil {
+		return nil, err
+	}
+
+	var res *http.Response
+
+	url := fmt.Sprintf("http://%s:6784/ip/%s", weaveip, ipamID(ID))
+	Log.Debugf("Attempting to %s to %s", op, url)
+	if op == "POST" {
+		res, err = http.Post(url, "", nil)
+	} else if op == "GET" {
+		res, err = http.Get(url)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+	if res.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("received status %d from IPAM", res.StatusCode)
+	}
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return nil, err
+	}
+	return parseIP(string(body))
+}
+
+// returns an IP for the ID given, allocating a fresh one if necessary
+func (d *dockerer) allocateIP(ID string) (*net.IPNet, error) {
+	return d.ipamOp(ID, "POST")
+}
+
+// returns an IP for the ID given, or nil if one has not been
+// allocated
+func (d *dockerer) lookupIP(ID string) (*net.IPNet, error) {
+	return d.ipamOp(ID, "GET")
+}
+
+// release an IP which is no longer needed
+func (d *dockerer) releaseIP(ID string) error {
+	weaveip, err := d.getContainerBridgeIP(WeaveContainer)
+	if err != nil {
+		return err
+	}
+	req, err := http.NewRequest("DELETE", fmt.Sprintf("http://%s:6784/ip/%s", weaveip, ipamID(ID)), nil)
+	if err != nil {
+		return err
+	}
+	cl := &http.Client{}
+	res, err := cl.Do(req)
+	if err != nil {
+		return err
+	}
+	if res.StatusCode != http.StatusOK && res.StatusCode != http.StatusNoContent {
+		return fmt.Errorf("unexpected HTTP status code from IP release: %d", res.StatusCode)
+	}
+	return nil
+}
+
+func parseIP(body string) (*net.IPNet, error) {
+	ip, ipnet, err := net.ParseCIDR(string(body))
+	if err != nil {
+		return nil, err
+	}
+	ipnet.IP = ip
+	return ipnet, nil
+}
+
+// If something looking like a container ID is supplied to IPAM, it
+// will try to check that it's running, and return nothing (and empty
+// string) if it's not. So I make sure it doesn't look like a
+// container ID by including non-hex characters.
+func ipamID(ID string) string {
+	return "endpoint:" + ID
+}

plugin/skel/listener.go

@@ -0,0 +1,206 @@
+package skel
+
+import (
+	"encoding/json"
+	"fmt"
+	"net"
+	"net/http"
+
+	"github.com/gorilla/mux"
+
+	"github.com/docker/libnetwork/drivers/remote/api"
+)
+
+const (
+	MethodReceiver = "NetworkDriver"
+)
+
+type Driver interface {
+	GetCapabilities() (*api.GetCapabilityResponse, error)
+	CreateNetwork(create *api.CreateNetworkRequest) error
+	DeleteNetwork(delete *api.DeleteNetworkRequest) error
+	CreateEndpoint(create *api.CreateEndpointRequest) (*api.CreateEndpointResponse, error)
+	DeleteEndpoint(delete *api.DeleteEndpointRequest) error
+	EndpointInfo(req *api.EndpointInfoRequest) (*api.EndpointInfoResponse, error)
+	JoinEndpoint(j *api.JoinRequest) (response *api.JoinResponse, error error)
+	LeaveEndpoint(leave *api.LeaveRequest) error
+	DiscoverNew(discover *api.DiscoveryNotification) error
+	DiscoverDelete(delete *api.DiscoveryNotification) error
+}
+
+type listener struct {
+	d Driver
+}
+
+func Listen(socket net.Listener, driver Driver) error {
+	router := mux.NewRouter()
+	router.NotFoundHandler = http.HandlerFunc(notFound)
+
+	router.Methods("POST").Path("/Plugin.Activate").HandlerFunc(handshake)
+
+	handleMethod := func(method string, h http.HandlerFunc) {
+		router.Methods("POST").Path(fmt.Sprintf("/%s.%s", MethodReceiver, method)).HandlerFunc(h)
+	}
+
+	listener := &listener{driver}
+
+	handleMethod("GetCapabilities", listener.getCapabilities)
+	handleMethod("CreateNetwork", listener.createNetwork)
+	handleMethod("DeleteNetwork", listener.deleteNetwork)
+	handleMethod("CreateEndpoint", listener.createEndpoint)
+	handleMethod("DeleteEndpoint", listener.deleteEndpoint)
+	handleMethod("EndpointOperInfo", listener.infoEndpoint)
+	handleMethod("Join", listener.joinEndpoint)
+	handleMethod("Leave", listener.leaveEndpoint)
+
+	return http.Serve(socket, router)
+}
+
+// === protocol handlers
+
+type handshakeResp struct {
+	Implements []string
+}
+
+func handshake(w http.ResponseWriter, r *http.Request) {
+	err := json.NewEncoder(w).Encode(&handshakeResp{
+		[]string{"NetworkDriver"},
+	})
+	if err != nil {
+		sendError(w, "encode error", http.StatusInternalServerError)
+		return
+	}
+}
+
+func (listener *listener) getCapabilities(w http.ResponseWriter, r *http.Request) {
+	caps, err := listener.d.GetCapabilities()
+	objectOrErrorResponse(w, caps, err)
+}
+
+func (listener *listener) createNetwork(w http.ResponseWriter, r *http.Request) {
+	var create api.CreateNetworkRequest
+	err := json.NewDecoder(r.Body).Decode(&create)
+	if err != nil {
+		sendError(w, "Unable to decode JSON payload: "+err.Error(), http.StatusBadRequest)
+		return
+	}
+	emptyOrErrorResponse(w, listener.d.CreateNetwork(&create))
+}
+
+func (listener *listener) deleteNetwork(w http.ResponseWriter, r *http.Request) {
+	var delete api.DeleteNetworkRequest
+	if err := json.NewDecoder(r.Body).Decode(&delete); err != nil {
+		sendError(w, "Unable to decode JSON payload: "+err.Error(), http.StatusBadRequest)
+		return
+	}
+	emptyOrErrorResponse(w, listener.d.DeleteNetwork(&delete))
+}
+
+func (listener *listener) createEndpoint(w http.ResponseWriter, r *http.Request) {
+	var create api.CreateEndpointRequest
+	if err := json.NewDecoder(r.Body).Decode(&create); err != nil {
+		sendError(w, "unable to decode JSON payload: "+err.Error(), http.StatusBadRequest)
+		return
+	}
+	res, err := listener.d.CreateEndpoint(&create)
+	objectOrErrorResponse(w, res, err)
+}
+
+func (listener *listener) deleteEndpoint(w http.ResponseWriter, r *http.Request) {
+	var delete api.DeleteEndpointRequest
+	if err := json.NewDecoder(r.Body).Decode(&delete); err != nil {
+		sendError(w, "Could not decode JSON encode payload", http.StatusBadRequest)
+		return
+	}
+	emptyOrErrorResponse(w, listener.d.DeleteEndpoint(&delete))
+}
+
+func (listener *listener) infoEndpoint(w http.ResponseWriter, r *http.Request) {
+	var req api.EndpointInfoRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		sendError(w, "Could not decode JSON encode payload", http.StatusBadRequest)
+		return
+	}
+	info, err := listener.d.EndpointInfo(&req)
+	objectOrErrorResponse(w, info, err)
+}
+
+func (listener *listener) joinEndpoint(w http.ResponseWriter, r *http.Request) {
+	var join api.JoinRequest
+	if err := json.NewDecoder(r.Body).Decode(&join); err != nil {
+		sendError(w, "Could not decode JSON encode payload", http.StatusBadRequest)
+		return
+	}
+	res, err := listener.d.JoinEndpoint(&join)
+	objectOrErrorResponse(w, res, err)
+}
+
+func (listener *listener) leaveEndpoint(w http.ResponseWriter, r *http.Request) {
+	var l api.LeaveRequest
+	if err := json.NewDecoder(r.Body).Decode(&l); err != nil {
+		sendError(w, "Could not decode JSON encode payload", http.StatusBadRequest)
+		return
+	}
+	emptyOrErrorResponse(w, listener.d.LeaveEndpoint(&l))
+}
+
+func (listener *listener) discoverNew(w http.ResponseWriter, r *http.Request) {
+	var disco api.DiscoveryNotification
+	if err := json.NewDecoder(r.Body).Decode(&disco); err != nil {
+		sendError(w, "Could not decode JSON encode payload", http.StatusBadRequest)
+		return
+	}
+	emptyOrErrorResponse(w, listener.d.DiscoverNew(&disco))
+}
+
+func (listener *listener) discoverDelete(w http.ResponseWriter, r *http.Request) {
+	var disco api.DiscoveryNotification
+	if err := json.NewDecoder(r.Body).Decode(&disco); err != nil {
+		sendError(w, "Could not decode JSON encode payload", http.StatusBadRequest)
+		return
+	}
+	emptyOrErrorResponse(w, listener.d.DiscoverDelete(&disco))
+}
+
+// ===
+
+func notFound(w http.ResponseWriter, r *http.Request) {
+	http.NotFound(w, r)
+}
+
+func sendError(w http.ResponseWriter, msg string, code int) {
+	http.Error(w, msg, code)
+}
+
+func errorResponse(w http.ResponseWriter, fmtString string, item ...interface{}) {
+	json.NewEncoder(w).Encode(map[string]string{
+		"Err": fmt.Sprintf(fmtString, item...),
+	})
+}
+
+func objectResponse(w http.ResponseWriter, obj interface{}) {
+	if err := json.NewEncoder(w).Encode(obj); err != nil {
+		sendError(w, "Could not JSON encode response", http.StatusInternalServerError)
+		return
+	}
+}
+
+func emptyResponse(w http.ResponseWriter) {
+	json.NewEncoder(w).Encode(map[string]string{})
+}
+
+func objectOrErrorResponse(w http.ResponseWriter, obj interface{}, err error) {
+	if err != nil {
+		errorResponse(w, err.Error())
+		return
+	}
+	objectResponse(w, obj)
+}
+
+func emptyOrErrorResponse(w http.ResponseWriter, err error) {
+	if err != nil {
+		errorResponse(w, err.Error())
+		return
+	}
+	emptyResponse(w)
+}

plugin/watcher.go

@@ -0,0 +1,89 @@
+package plugin
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/fsouza/go-dockerclient"
+	. "github.com/weaveworks/weave/common"
+)
+
+const (
+	WeaveDNSContainer = "weavedns"
+	WeaveDomain       = "weave.local"
+)
+
+type watcher struct {
+	dockerer
+	networks map[string]bool
+	events   chan *docker.APIEvents
+}
+
+type Watcher interface {
+}
+
+func NewWatcher(client *docker.Client) (Watcher, error) {
+	w := &watcher{
+		dockerer: dockerer{
+			client: client,
+		},
+		networks: make(map[string]bool),
+		events:   make(chan *docker.APIEvents),
+	}
+	err := client.AddEventListener(w.events)
+	if err != nil {
+		return nil, err
+	}
+
+	go func() {
+		for event := range w.events {
+			switch event.Status {
+			case "start":
+				w.ContainerStart(event.ID)
+			case "die":
+				w.ContainerDied(event.ID)
+			}
+		}
+	}()
+
+	return w, nil
+}
+
+func (w *watcher) ContainerStart(id string) {
+	Log.Debugf("Container started %s", id)
+	info, err := w.InspectContainer(id)
+	if err != nil {
+		Log.Warningf("error inspecting container: %s", err)
+		return
+	}
+	// FIXME: check that it's on our network; but, the docker client lib doesn't know about .NetworkID
+	if isSubdomain(info.Config.Domainname, WeaveDomain) {
+		// one of ours
+		ip := info.NetworkSettings.IPAddress
+		fqdn := fmt.Sprintf("%s.%s", info.Config.Hostname, info.Config.Domainname)
+		if err := w.registerWithDNS(id, fqdn, ip); err != nil {
+			Log.Warningf("unable to register with weaveDNS: %s", err)
+		}
+	}
+}
+
+func (w *watcher) ContainerDied(id string) {
+	Log.Debugf("Container died %s", id)
+	info, err := w.InspectContainer(id)
+	if err != nil {
+		Log.Warningf("error inspecting container: %s", err)
+		return
+	}
+	if isSubdomain(info.Config.Domainname, WeaveDomain) {
+		ip := info.NetworkSettings.IPAddress
+		if err := w.deregisterWithDNS(id, ip); err != nil {
+			Log.Warningf("unable to deregister with weaveDNS: %s", err)
+		}
+	}
+}
+
+// Cheap and cheerful way to check x is, or is a subdomain, of
+// y. Neither are expected to start with a '.'.
+func isSubdomain(x string, y string) bool {
+	return x == y || strings.HasSuffix(x, "."+y)
+}

prog/plugin/Dockerfile

@@ -0,0 +1,3 @@
+FROM weaveworks/weaveexec
+ADD ./plugin /home/weave/
+ENTRYPOINT ["/home/weave/plugin"]

prog/plugin/main.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"net"
+	"os"
+	"os/signal"
+	"syscall"
+
+	. "github.com/weaveworks/weave/common"
+	"github.com/weaveworks/weave/plugin"
+	"github.com/weaveworks/weave/plugin/skel"
+)
+
+var version = "(unreleased version)"
+
+func main() {
+	var (
+		justVersion bool
+		address     string
+		nameserver  string
+		logLevel    string
+	)
+
+	flag.BoolVar(&justVersion, "version", false, "print version and exit")
+	flag.StringVar(&logLevel, "log-level", "info", "logging level (debug, info, warning, error)")
+	flag.StringVar(&address, "socket", "/run/docker/plugins/weave.sock", "socket on which to listen")
+	flag.StringVar(&nameserver, "nameserver", "", "nameserver to provide to containers")
+
+	flag.Parse()
+
+	if justVersion {
+		fmt.Printf("weave plugin %s\n", version)
+		os.Exit(0)
+	}
+
+	SetLogLevel(logLevel)
+
+	Log.Println("Weave plugin", version, "Command line options:", os.Args)
+
+	var d skel.Driver
+	d, err := plugin.New(version, nameserver)
+	if err != nil {
+		Log.Fatalf("unable to create driver: %s", err)
+	}
+
+	var listener net.Listener
+
+	// remove socket from last invocation
+	if err := os.Remove(address); err != nil && !os.IsNotExist(err) {
+		Log.Fatal(err)
+	}
+	listener, err = net.Listen("unix", address)
+	if err != nil {
+		Log.Fatal(err)
+	}
+	defer listener.Close()
+
+	sigChan := make(chan os.Signal, 1)
+	signal.Notify(sigChan, os.Interrupt, os.Kill, syscall.SIGTERM)
+
+	endChan := make(chan error, 1)
+	go func() {
+		endChan <- skel.Listen(listener, d)
+	}()
+
+	select {
+	case sig := <-sigChan:
+		Log.Debugf("Caught signal %s; shutting down", sig)
+	case err := <-endChan:
+		if err != nil {
+			Log.Errorf("Error from listener: %s", err)
+			listener.Close()
+			os.Exit(1)
+		}
+	}
+}