bridge: disable IPv6 router advertisements

Signed-off-by: Samuel Karp <skarp@amazon.com>
(cherry picked from commit 153d076)
Signed-off-by: Shane Jarych <sjarych@mirantis.com>

drivers/bridge/bridge.go

@@ -679,6 +679,12 @@ func (d *driver) createNetwork(config *networkConfiguration) (err error) {
 	bridgeAlreadyExists := bridgeIface.exists()
 	if !bridgeAlreadyExists {
 		bridgeSetup.queueStep(setupDevice)
+		bridgeSetup.queueStep(setupDefaultSysctl)
+	}
+
+	// For the default bridge, set expected sysctls
+	if config.DefaultBridge {
+		bridgeSetup.queueStep(setupDefaultSysctl)
 	}
 
 	// Even if a bridge exists try to setup IPv4.

drivers/bridge/setup_device.go

@@ -2,6 +2,9 @@ package bridge
 
 import (
 	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
 
 	"github.com/docker/docker/pkg/parsers/kernel"
 	"github.com/docker/libnetwork/netutils"
@@ -50,6 +53,22 @@ func setupDevice(config *networkConfiguration, i *bridgeInterface) error {
 	return err
 }
 
+func setupDefaultSysctl(config *networkConfiguration, i *bridgeInterface) error {
+	// Disable IPv6 router advertisements originating on the bridge
+	sysPath := filepath.Join("/proc/sys/net/ipv6/conf/", config.BridgeName, "accept_ra")
+	if _, err := os.Stat(sysPath); err != nil {
+		logrus.
+			WithField("bridge", config.BridgeName).
+			WithField("syspath", sysPath).
+			Info("failed to read ipv6 net.ipv6.conf.<bridge>.accept_ra")
+		return nil
+	}
+	if err := ioutil.WriteFile(sysPath, []byte{'0', '\n'}, 0644); err != nil {
+		return fmt.Errorf("libnetwork: Unable to disable IPv6 router advertisement: %v", err)
+	}
+	return nil
+}
+
 // SetupDeviceUp ups the given bridge interface.
 func setupDeviceUp(config *networkConfiguration, i *bridgeInterface) error {
 	err := i.nlh.LinkSetUp(i.Link)