From 8bb8f70bb6c10f4551bbf4c97c80b9d5dd31fcaf Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Tue, 14 Jun 2016 17:53:34 +0100
Subject: [PATCH] Perform arp configuration for plugin-connected containers

---
 common/utils.go       | 19 +++++++++++++++++++
 plugin/net/watcher.go |  5 +++++
 weave                 |  1 +
 3 files changed, 25 insertions(+)

diff --git a/common/utils.go b/common/utils.go
index 666eb4f7..7086cd9f 100644
--- a/common/utils.go
+++ b/common/utils.go
@@ -6,6 +6,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/j-keck/arping"
 	"github.com/vishvananda/netlink"
 	"github.com/vishvananda/netns"
 
@@ -34,6 +35,7 @@ type NetDev struct {
 }
 
 // Search the network namespace of a process for interfaces matching a predicate
+// Note that the predicate is called while the goroutine is inside the process' netns
 func FindNetDevs(processID int, match func(link netlink.Link) bool) ([]NetDev, error) {
 	var netDevs []NetDev
 
@@ -137,3 +139,20 @@ func GetBridgeNetDev(bridgeName string) ([]NetDev, error) {
 		return link.Attrs().Name == bridgeName
 	})
 }
+
+// Do post-attach configuration of all veths we have created
+func ConfigureARPforVeths(processID int, prefix string) error {
+	_, err := FindNetDevs(processID, func(link netlink.Link) bool {
+		ifName := link.Attrs().Name
+		if strings.HasPrefix(ifName, prefix) {
+			weavenet.ConfigureARPCache(ifName)
+			if addrs, err := netlink.AddrList(link, netlink.FAMILY_V4); err == nil {
+				for _, addr := range addrs {
+					arping.GratuitousArpOverIfaceByName(addr.IPNet.IP, ifName)
+				}
+			}
+		}
+		return false
+	})
+	return err
+}
diff --git a/plugin/net/watcher.go b/plugin/net/watcher.go
index e72ba570..3217b646 100644
--- a/plugin/net/watcher.go
+++ b/plugin/net/watcher.go
@@ -4,7 +4,9 @@ import (
 	"fmt"
 
 	weaveapi "github.com/weaveworks/weave/api"
+	"github.com/weaveworks/weave/common"
 	"github.com/weaveworks/weave/common/docker"
+	weavenet "github.com/weaveworks/weave/net"
 )
 
 const (
@@ -44,6 +46,9 @@ func (w *watcher) ContainerStarted(id string) {
 			if err := w.weave.RegisterWithDNS(id, fqdn, net.IPAddress); err != nil {
 				w.driver.warn("ContainerStarted", "unable to register %s with weaveDNS: %s", id, err)
 			}
+			if err := common.ConfigureARPforVeths(info.State.Pid, weavenet.VethName); err != nil {
+				w.driver.warn("ContainerStarted", "unable to configure interfaces: %s", err)
+			}
 		}
 	}
 }
diff --git a/weave b/weave
index 9bc0340f..1709d910 100755
--- a/weave
+++ b/weave
@@ -1747,6 +1747,7 @@ launch_plugin_if_not_running() {
     if ! PLUGIN_CONTAINER=$(docker run -d --name=$PLUGIN_CONTAINER_NAME \
         $(docker_run_options) \
         $RESTART_POLICY \
+        --pid=host \
         -v /run/docker/plugins:/run/docker/plugins \
         -e WEAVE_HTTP_ADDR \
         $WEAVEPLUGIN_DOCKER_ARGS $PLUGIN_IMAGE $COVERAGE_ARGS \