Wait for ethwe via netlink, not via polling or signals

('docker kill' breaks restart policy)

Makefile

@@ -74,7 +74,8 @@ $(NETCHECK_EXE): prog/netcheck/netcheck.go
 # Sigproxy and weavewait 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/main.go
+$(WEAVEWAIT_EXE): prog/weavewait/main.go net/*.go
+$(WEAVEHOSTS_EXE): prog/weavehosts/weavehosts.go
 $(COVER_EXE): testing/cover/cover.go
 $(RUNNER_EXE): testing/runner/runner.go
 

net/if.go

@@ -2,30 +2,24 @@ package net
 
 import (
 	"fmt"
-	"math"
 	"net"
-	"time"
+	"syscall"
+
+	"github.com/vishvananda/netlink/nl"
 )
 
-const (
-	sleepTime = 100 * time.Millisecond
-)
-
-// Wait `wait` seconds for an interface to come up. Pass zero to check once
-// and return immediately, or a negative value to wait indefinitely.
-func EnsureInterface(ifaceName string, wait int) (iface *net.Interface, err error) {
-	if iface, err = findInterface(ifaceName); err == nil || wait == 0 {
-		return
+// Wait for an interface to come up.
+func EnsureInterface(ifaceName string) (*net.Interface, error) {
+	s, err := nl.Subscribe(syscall.NETLINK_ROUTE, syscall.RTNLGRP_LINK)
+	if err != nil {
+		return nil, err
 	}
-	i := int64(math.MaxInt64)
-	if wait > 0 {
-		i = int64(time.Duration(wait) * time.Second / sleepTime)
+	defer s.Close()
+	if iface, err := findInterface(ifaceName); err == nil {
+		return iface, nil
 	}
-	for ; err != nil && i > 0; i-- {
-		time.Sleep(sleepTime)
-		iface, err = findInterface(ifaceName)
-	}
-	return
+	waitForIfUp(s, ifaceName)
+	return findInterface(ifaceName)
 }
 
 func findInterface(ifaceName string) (iface *net.Interface, err error) {
@@ -37,3 +31,31 @@ func findInterface(ifaceName string) (iface *net.Interface, err error) {
 	}
 	return
 }
+
+func waitForIfUp(s *nl.NetlinkSocket, ifaceName string) error {
+	for {
+		msgs, err := s.Receive()
+		if err != nil {
+			return err
+		}
+		for _, m := range msgs {
+			switch m.Header.Type {
+			case syscall.RTM_NEWLINK: // receive this type for link 'up'
+				ifmsg := nl.DeserializeIfInfomsg(m.Data)
+				attrs, err := syscall.ParseNetlinkRouteAttr(&m)
+				if err != nil {
+					return err
+				}
+				name := ""
+				for _, attr := range attrs {
+					if attr.Attr.Type == syscall.IFA_LABEL {
+						name = string(attr.Value[:len(attr.Value)-1])
+					}
+				}
+				if ifaceName == name && ifmsg.Flags&syscall.IFF_UP != 0 {
+					return nil
+				}
+			}
+		}
+	}
+}

prog/weaver/main.go

@@ -43,7 +43,6 @@ func main() {
 		routerName         string
 		nickName           string
 		password           string
-		wait               int
 		pktdebug           bool
 		logLevel           string
 		prof               string
@@ -71,7 +70,6 @@ func main() {
 	mflag.StringVar(&routerName, []string{"#name", "-name"}, "", "name of router (defaults to MAC of interface)")
 	mflag.StringVar(&nickName, []string{"#nickname", "-nickname"}, "", "nickname of peer (defaults to hostname)")
 	mflag.StringVar(&password, []string{"#password", "-password"}, "", "network password")
-	mflag.IntVar(&wait, []string{"#wait", "-wait"}, -1, "number of seconds to wait for interface to come up (0=don't wait, -1=wait forever)")
 	mflag.StringVar(&logLevel, []string{"-log-level"}, "info", "logging level (debug, info, warning, error)")
 	mflag.BoolVar(&pktdebug, []string{"#pktdebug", "#-pktdebug", "-pkt-debug"}, false, "enable per-packet debug logging")
 	mflag.StringVar(&prof, []string{"#profile", "-profile"}, "", "enable profiling and write profiles to given path")
@@ -118,7 +116,7 @@ func main() {
 	var err error
 
 	if ifaceName != "" {
-		config.Iface, err = weavenet.EnsureInterface(ifaceName, wait)
+		config.Iface, err = weavenet.EnsureInterface(ifaceName)
 		if err != nil {
 			Log.Fatal(err)
 		}

prog/weavewait/main.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
-	"os/signal"
 	"syscall"
 
 	weavenet "github.com/weaveworks/weave/net"
@@ -17,22 +16,10 @@ var (
 
 func main() {
 	var (
-		args      = os.Args[1:]
-		notInExec = true
+		args = os.Args[1:]
 	)
 
-	if len(args) > 0 && args[0] == "-s" {
-		notInExec = false
-		args = args[1:]
-	}
-
-	if notInExec {
-		usr2 := make(chan os.Signal)
-		signal.Notify(usr2, syscall.SIGUSR2)
-		<-usr2
-	}
-
-	_, err := weavenet.EnsureInterface("ethwe", -1)
+	_, err := weavenet.EnsureInterface("ethwe")
 	checkErr(err)
 
 	if len(args) == 0 {

proxy/create_exec_interceptor.go

@@ -35,7 +35,7 @@ func (i *createExecInterceptor) InterceptRequest(r *http.Request) error {
 		Log.Infof("Leaving container %s alone because %s", container.ID, err)
 	} else if hasWeaveWait {
 		Log.Infof("Exec in container %s with WEAVE_CIDR \"%s\"", container.ID, strings.Join(cidrs, " "))
-		cmd := append(weaveWaitEntrypoint, "-s")
+		cmd := weaveWaitEntrypoint
 		options.Cmd = append(cmd, options.Cmd...)
 	}