// ConfigureNetworking is called once during host startup and passed the
// strategy and identifier of the networking coordinatior job. Currently the
// only strategy implemented uses flannel.
func (l *LibvirtLXCBackend) ConfigureNetworking(config *host.NetworkConfig) error {
	var err error
	l.bridgeAddr, l.bridgeNet, err = net.ParseCIDR(config.Subnet)
	if err != nil {
		return err
	}
	l.ipalloc.RequestIP(l.bridgeNet, l.bridgeAddr)

	err = netlink.CreateBridge(bridgeName, false)
	bridgeExists := os.IsExist(err)
	if err != nil && !bridgeExists {
		return err
	}

	bridge, err := net.InterfaceByName(bridgeName)
	if err != nil {
		return err
	}
	if !bridgeExists {
		// We need to explicitly assign the MAC address to avoid it changing to a lower value
		// See: https://github.com/flynn/flynn/issues/223
		b := random.Bytes(5)
		bridgeMAC := fmt.Sprintf("fe:%02x:%02x:%02x:%02x:%02x", b[0], b[1], b[2], b[3], b[4])
		if err := netlink.NetworkSetMacAddress(bridge, bridgeMAC); err != nil {
			return err
		}
	}
	currAddrs, err := bridge.Addrs()
	if err != nil {
		return err
	}
	setIP := true
	for _, addr := range currAddrs {
		ip, net, _ := net.ParseCIDR(addr.String())
		if ip.Equal(l.bridgeAddr) && net.String() == l.bridgeNet.String() {
			setIP = false
		} else {
			if err := netlink.NetworkLinkDelIp(bridge, ip, net); err != nil {
				return err
			}
		}
	}
	if setIP {
		if err := netlink.NetworkLinkAddIp(bridge, l.bridgeAddr, l.bridgeNet); err != nil {
			return err
		}
	}
	if err := netlink.NetworkLinkUp(bridge); err != nil {
		return err
	}

	network, err := l.libvirt.LookupNetworkByName(libvirtNetName)
	if err != nil {
		// network doesn't exist
		networkConfig := &lt.Network{
			Name:    libvirtNetName,
			Bridge:  lt.Bridge{Name: bridgeName},
			Forward: lt.Forward{Mode: "bridge"},
		}
		network, err = l.libvirt.NetworkDefineXML(string(networkConfig.XML()))
		if err != nil {
			return err
		}
	}
	active, err := network.IsActive()
	if err != nil {
		return err
	}
	if !active {
		if err := network.Create(); err != nil {
			return err
		}
	}
	if defaultNet, err := l.libvirt.LookupNetworkByName("default"); err == nil {
		// The default network causes dnsmasq to run and bind to all interfaces,
		// including ours. This prevents discoverd from binding its DNS server.
		// We don't use it, so destroy it if it exists.
		defaultNet.Destroy()
	}

	// enable IP forwarding
	if err := ioutil.WriteFile("/proc/sys/net/ipv4/ip_forward", []byte("1\n"), 0644); err != nil {
		return err
	}

	// Set up iptables for outbound traffic masquerading from containers to the
	// rest of the network.
	if err := iptables.EnableOutboundNAT(bridgeName, l.bridgeNet.String()); err != nil {
		return err
	}

	// Read DNS config, discoverd uses the nameservers
	dnsConf, err := dns.ClientConfigFromFile("/etc/resolv.conf")
	if err != nil {
		return err
	}
	config.Resolvers = dnsConf.Servers

	// Write a resolv.conf to be bind-mounted into containers pointing at the
	// future discoverd DNS listener
	if err := os.MkdirAll("/etc/flynn", 0755); err != nil {
		return err
	}
	var resolvSearch string
	if len(dnsConf.Search) > 0 {
		resolvSearch = fmt.Sprintf("search %s\n", strings.Join(dnsConf.Search, " "))
	}
	if err := ioutil.WriteFile("/etc/flynn/resolv.conf", []byte(fmt.Sprintf("%snameserver %s\n", resolvSearch, l.bridgeAddr.String())), 0644); err != nil {
		return err
	}
	l.resolvConf = "/etc/flynn/resolv.conf"

	// Allocate IPs for running jobs
	for i, container := range l.containers {
		if !container.job.Config.HostNetwork {
			var err error
			l.containers[i].IP, err = l.ipalloc.RequestIP(l.bridgeNet, container.IP)
			if err != nil {
				grohl.Log(grohl.Data{"fn": "ConfigureNetworking", "at": "request_ip", "status": "error", "err": err})
			}
		}
	}

	close(l.networkConfigured)

	return nil
}
// ConfigureNetworking is called once during host startup and sets up the local
// bridge and forwarding rules for containers.
func (l *LibcontainerBackend) ConfigureNetworking(config *host.NetworkConfig) error {
	log := l.logger.New("fn", "ConfigureNetworking")
	var err error
	l.bridgeAddr, l.bridgeNet, err = net.ParseCIDR(config.Subnet)
	if err != nil {
		return err
	}
	l.ipalloc.RequestIP(l.bridgeNet, l.bridgeAddr)

	err = netlink.CreateBridge(l.bridgeName, false)
	bridgeExists := os.IsExist(err)
	if err != nil && !bridgeExists {
		return err
	}

	bridge, err := net.InterfaceByName(l.bridgeName)
	if err != nil {
		return err
	}
	if !bridgeExists {
		// We need to explicitly assign the MAC address to avoid it changing to a lower value
		// See: https://github.com/flynn/flynn/issues/223
		b := random.Bytes(5)
		bridgeMAC := fmt.Sprintf("fe:%02x:%02x:%02x:%02x:%02x", b[0], b[1], b[2], b[3], b[4])
		if err := netlink.NetworkSetMacAddress(bridge, bridgeMAC); err != nil {
			return err
		}
	}
	currAddrs, err := bridge.Addrs()
	if err != nil {
		return err
	}
	setIP := true
	for _, addr := range currAddrs {
		ip, net, _ := net.ParseCIDR(addr.String())
		if ip.Equal(l.bridgeAddr) && net.String() == l.bridgeNet.String() {
			setIP = false
		} else {
			if err := netlink.NetworkLinkDelIp(bridge, ip, net); err != nil {
				return err
			}
		}
	}
	if setIP {
		if err := netlink.NetworkLinkAddIp(bridge, l.bridgeAddr, l.bridgeNet); err != nil {
			return err
		}
	}
	if err := netlink.NetworkLinkUp(bridge); err != nil {
		return err
	}

	// enable IP forwarding
	if err := ioutil.WriteFile("/proc/sys/net/ipv4/ip_forward", []byte("1\n"), 0644); err != nil {
		return err
	}

	// Set up iptables for outbound traffic masquerading from containers to the
	// rest of the network.
	if err := iptables.EnableOutboundNAT(l.bridgeName, l.bridgeNet.String()); err != nil {
		return err
	}

	// Read DNS config, discoverd uses the nameservers
	dnsConf, err := dns.ClientConfigFromFile("/etc/resolv.conf")
	if err != nil {
		return err
	}
	config.Resolvers = dnsConf.Servers

	// Write a resolv.conf to be bind-mounted into containers pointing at the
	// future discoverd DNS listener
	if err := os.MkdirAll("/etc/flynn", 0755); err != nil {
		return err
	}
	var resolvSearch string
	if len(dnsConf.Search) > 0 {
		resolvSearch = fmt.Sprintf("search %s\n", strings.Join(dnsConf.Search, " "))
	}
	if err := ioutil.WriteFile("/etc/flynn/resolv.conf", []byte(fmt.Sprintf("%snameserver %s\n", resolvSearch, l.bridgeAddr.String())), 0644); err != nil {
		return err
	}
	l.resolvConf = "/etc/flynn/resolv.conf"

	// Allocate IPs for running jobs
	l.containersMtx.Lock()
	defer l.containersMtx.Unlock()
	for _, container := range l.containers {
		if !container.job.Config.HostNetwork {
			if _, err := l.ipalloc.RequestIP(l.bridgeNet, container.IP); err != nil {
				log.Error("error requesting ip", "job.id", container.job.ID, "err", err)
			}
		}
	}

	close(l.networkConfigured)

	return nil
}