// MaintainInstance checks that the container's host has the required iptables and routing
// rules to make the container visible to both the host and other machines on the same subnet.
func (broker *kvmBroker) MaintainInstance(args environs.StartInstanceParams) error {
	machineId := args.InstanceConfig.MachineId
	if !environs.AddressAllocationEnabled() {
		kvmLogger.Debugf("address allocation disabled: Not running maintenance for kvm with machineId: %s",
			machineId)
		return nil
	}

	kvmLogger.Debugf("running maintenance for kvm with machineId: %s", machineId)

	// Default to using the host network until we can configure.
	bridgeDevice := broker.agentConfig.Value(agent.LxcBridge)
	if bridgeDevice == "" {
		bridgeDevice = kvm.DefaultKvmBridge
	}
	_, err := configureContainerNetwork(
		machineId,
		bridgeDevice,
		broker.api,
		args.NetworkInfo,
		false, // don't allocate a new address.
		broker.enableNAT,
	)
	return err
}

func (p *ProvisionerAPI) legacyAddressAllocationSupported() (bool, error) {
	config, err := p.st.ModelConfig()
	if err != nil {
		return false, errors.Trace(err)
	}
	return environs.AddressAllocationEnabled(config.Type()), nil
}

func maybeReleaseContainerAddresses(
	api APICalls,
	instanceID instance.Id,
	namespace string,
	log loggo.Logger,
) {
	if environs.AddressAllocationEnabled() {
		// The addresser worker will take care of the addresses.
		return
	}
	// If we're not using addressable containers, we might still have used MAAS
	// 1.8+ device to register the container when provisioning. In that case we
	// need to attempt releasing the device, but ignore a NotSupported error
	// (when we're not using MAAS 1.8+).
	namespacePrefix := fmt.Sprintf("%s-", namespace)
	tagString := strings.TrimPrefix(string(instanceID), namespacePrefix)
	containerTag, err := names.ParseMachineTag(tagString)
	if err != nil {
		// Not a reason to cause StopInstances to fail though..
		log.Warningf("unexpected container tag %q: %v", instanceID, err)
		return
	}
	err = api.ReleaseContainerAddresses(containerTag)
	switch {
	case err == nil:
		log.Infof("released all addresses for container %q", containerTag.Id())
	case errors.IsNotSupported(err):
		log.Warningf("not releasing all addresses for container %q: %v", containerTag.Id(), err)
	default:
		log.Warningf(
			"unexpected error trying to release container %q addreses: %v",
			containerTag.Id(), err,
		)
	}
}

// AllocateAddress requests an address to be allocated for the
// given instance on the given subnet.
func (env *environ) AllocateAddress(instId instance.Id, subnetId network.Id, addr network.Address, macAddress, hostname string) error {
	if !environs.AddressAllocationEnabled() {
		return errors.NotSupportedf("address allocation")
	}

	if err := env.checkBroken("AllocateAddress"); err != nil {
		return err
	}

	estate, err := env.state()
	if err != nil {
		return err
	}
	estate.mu.Lock()
	defer estate.mu.Unlock()
	estate.maxAddr++
	estate.ops <- OpAllocateAddress{
		Env:        env.name,
		InstanceId: instId,
		SubnetId:   subnetId,
		Address:    addr,
		MACAddress: macAddress,
		HostName:   hostname,
	}
	return nil
}

// runInitialiser runs the container initialiser with the initialisation hook held.
func (cs *ContainerSetup) runInitialiser(containerType instance.ContainerType, initialiser container.Initialiser) error {
	logger.Debugf("running initialiser for %s containers", containerType)
	if err := cs.initLock.Lock(fmt.Sprintf("initialise-%s", containerType)); err != nil {
		return errors.Annotate(err, "failed to acquire initialization lock")
	}
	defer cs.initLock.Unlock()

	// Only tweak default LXC network config when address allocation
	// feature flag is enabled.
	if environs.AddressAllocationEnabled() {
		// In order to guarantee stable statically assigned IP addresses
		// for LXC containers, we need to install a custom version of
		// /etc/default/lxc-net before we install the lxc package. The
		// custom version of lxc-net is almost the same as the original,
		// but the defined LXC_DHCP_RANGE (used by dnsmasq to give away
		// 10.0.3.x addresses to containers bound to lxcbr0) has infinite
		// lease time. This is necessary, because with the default lease
		// time of 1h, dhclient running inside each container will request
		// a renewal from dnsmasq and replace our statically configured IP
		// address within an hour after starting the container.
		err := maybeOverrideDefaultLXCNet(containerType, cs.addressableContainers)
		if err != nil {
			return errors.Trace(err)
		}
	}

	if err := initialiser.Initialise(); err != nil {
		return errors.Trace(err)
	}

	return nil
}

// GetContainerInterfaceInfo returns information to configure networking
// for a container. It accepts container tags as arguments. If the address
// allocation feature flag is not enabled, it returns a NotSupported error.
func (p *ProvisionerAPI) GetContainerInterfaceInfo(args params.Entities) (
	params.MachineNetworkConfigResults, error) {
	if environs.AddressAllocationEnabled() {
		logger.Warningf("address allocation enabled - using legacyPrepareOrGetContainerInterfaceInfo(false)")
		return p.legacyPrepareOrGetContainerInterfaceInfo(args, false)
	}
	return p.prepareOrGetContainerInterfaceInfo(args, false)
}

// ContainerManagerConfig returns information from the environment config that is
// needed for configuring the container manager.
func (p *ProvisionerAPI) ContainerManagerConfig(args params.ContainerManagerConfigParams) (params.ContainerManagerConfig, error) {
	var result params.ContainerManagerConfig
	config, err := p.st.EnvironConfig()
	if err != nil {
		return result, err
	}
	cfg := make(map[string]string)
	cfg[container.ConfigName] = container.DefaultNamespace

	switch args.Type {
	case instance.LXC:
		if useLxcClone, ok := config.LXCUseClone(); ok {
			cfg["use-clone"] = fmt.Sprint(useLxcClone)
		}
		if useLxcCloneAufs, ok := config.LXCUseCloneAUFS(); ok {
			cfg["use-aufs"] = fmt.Sprint(useLxcCloneAufs)
		}
		if lxcDefaultMTU, ok := config.LXCDefaultMTU(); ok {
			logger.Debugf("using default MTU %v for all LXC containers NICs", lxcDefaultMTU)
			cfg[container.ConfigLXCDefaultMTU] = fmt.Sprintf("%d", lxcDefaultMTU)
		}
	}

	if !environs.AddressAllocationEnabled() {
		// No need to even try checking the environ for support.
		logger.Debugf("address allocation feature flag not enabled")
		result.ManagerConfig = cfg
		return result, nil
	}

	// Create an environment to verify networking support.
	env, err := environs.New(config)
	if err != nil {
		return result, err
	}
	if netEnv, ok := environs.SupportsNetworking(env); ok {
		// Passing network.AnySubnet below should be interpreted by
		// the provider as "does ANY subnet support this".
		supported, err := netEnv.SupportsAddressAllocation(network.AnySubnet)
		if err == nil && supported {
			cfg[container.ConfigIPForwarding] = "true"
		} else if err != nil {
			// We log the error, but it's safe to ignore as it's not
			// critical.
			logger.Debugf("address allocation not supported (%v)", err)
		}
		// AWS requires NAT in place in order for hosted containers to
		// reach outside.
		if config.Type() == provider.EC2 {
			cfg[container.ConfigEnableNAT] = "true"
		}
	}

	result.ManagerConfig = cfg
	return result, nil
}

// SupportsAddressAllocation is specified on environs.Networking.
func (env *environ) SupportsAddressAllocation(subnetId network.Id) (bool, error) {
	if !environs.AddressAllocationEnabled() {
		return false, errors.NotSupportedf("address allocation")
	}

	if err := env.checkBroken("SupportsAddressAllocation"); err != nil {
		return false, err
	}
	// Any subnetId starting with "noalloc-" will cause this to return
	// false, so it can be used in tests.
	if strings.HasPrefix(string(subnetId), "noalloc-") {
		return false, nil
	}
	return true, nil
}

// AllocateAddress requests an address to be allocated for the
// given instance on the given subnet.
func (env *environ) AllocateAddress(instId instance.Id, subnetId network.Id, addr *network.Address, macAddress, hostname string) error {
	if !environs.AddressAllocationEnabled("dummy") {
		// Any instId starting with "i-alloc-" when the feature flag is off will
		// still work, in order to be able to test MAAS 1.8+ environment where
		// we can use devices for containers.
		if !strings.HasPrefix(string(instId), "i-alloc-") {
			return errors.NotSupportedf("address allocation")
		}
		// Also, in this case we expect addr to be non-nil, but empty, so it can
		// be used as an output argument (same as in provider/maas).
		if addr == nil || addr.Value != "" {
			return errors.NewNotValid(nil, "invalid address: nil or non-empty")
		}
	}

	if err := env.checkBroken("AllocateAddress"); err != nil {
		return err
	}

	estate, err := env.state()
	if err != nil {
		return err
	}
	estate.mu.Lock()
	defer estate.mu.Unlock()
	estate.maxAddr++

	if addr.Value == "" {
		*addr = network.NewAddress(fmt.Sprintf("0.10.0.%v", estate.maxAddr))
	}

	estate.ops <- OpAllocateAddress{
		Env:        env.name,
		InstanceId: instId,
		SubnetId:   subnetId,
		Address:    *addr,
		MACAddress: macAddress,
		HostName:   hostname,
	}
	return nil
}

// ReleaseAddress releases a specific address previously allocated with
// AllocateAddress.
func (env *environ) ReleaseAddress(instId instance.Id, subnetId network.Id, addr network.Address) error {
	if !environs.AddressAllocationEnabled() {
		return errors.NotSupportedf("address allocation")
	}

	if err := env.checkBroken("ReleaseAddress"); err != nil {
		return err
	}
	estate, err := env.state()
	if err != nil {
		return err
	}
	estate.mu.Lock()
	defer estate.mu.Unlock()
	estate.maxAddr--
	estate.ops <- OpReleaseAddress{
		Env:        env.name,
		InstanceId: instId,
		SubnetId:   subnetId,
		Address:    addr,
	}
	return nil
}

// legacyPrepareOrGetContainerInterfaceInfo optionally allocates an address and
// returns information for configuring networking on a container. It accepts
// container tags as arguments.
func (p *ProvisionerAPI) legacyPrepareOrGetContainerInterfaceInfo(
	args params.Entities,
	provisionContainer bool,
) (
	params.MachineNetworkConfigResults,
	error,
) {
	result := params.MachineNetworkConfigResults{
		Results: make([]params.MachineNetworkConfigResult, len(args.Entities)),
	}

	// Some preparations first.
	environ, host, canAccess, err := p.prepareContainerAccessEnvironment()
	if err != nil {
		return result, errors.Trace(err)
	}
	instId, err := host.InstanceId()
	if err != nil && errors.IsNotProvisioned(err) {
		// If the host machine is not provisioned yet, we have nothing
		// to do. NotProvisionedf will append " not provisioned" to
		// the message.
		err = errors.NotProvisionedf("cannot allocate addresses: host machine %q", host)
		return result, err
	}
	var subnet *state.Subnet
	var subnetInfo network.SubnetInfo
	var interfaceInfo network.InterfaceInfo
	if environs.AddressAllocationEnabled() {
		// We don't need a subnet unless we need to allocate a static IP.
		subnet, subnetInfo, interfaceInfo, err = p.prepareAllocationNetwork(environ, instId)
		if err != nil {
			return result, errors.Annotate(err, "cannot allocate addresses")
		}
	} else {
		var allInterfaceInfos []network.InterfaceInfo
		allInterfaceInfos, err = environ.NetworkInterfaces(instId)
		if err != nil {
			return result, errors.Annotatef(err, "cannot instance %q interfaces", instId)
		} else if len(allInterfaceInfos) == 0 {
			return result, errors.New("no interfaces available")
		}
		// Currently we only support a single NIC per container, so we only need
		// the information from the host instance's first NIC.
		logger.Tracef("interfaces for instance %q: %v", instId, allInterfaceInfos)
		interfaceInfo = allInterfaceInfos[0]
	}

	// Loop over the passed container tags.
	for i, entity := range args.Entities {
		tag, err := names.ParseMachineTag(entity.Tag)
		if err != nil {
			result.Results[i].Error = common.ServerError(err)
			continue
		}

		// The auth function (canAccess) checks that the machine is a
		// top level machine (we filter those out next) or that the
		// machine has the host as a parent.
		container, err := p.getMachine(canAccess, tag)
		if err != nil {
			result.Results[i].Error = common.ServerError(err)
			continue
		} else if !container.IsContainer() {
			err = errors.Errorf("cannot allocate address for %q: not a container", tag)
			result.Results[i].Error = common.ServerError(err)
			continue
		} else if ciid, cerr := container.InstanceId(); provisionContainer == true && cerr == nil {
			// Since we want to configure and create NICs on the
			// container before it starts, it must also be not
			// provisioned yet.
			err = errors.Errorf("container %q already provisioned as %q", container, ciid)
			result.Results[i].Error = common.ServerError(err)
			continue
		} else if cerr != nil && !errors.IsNotProvisioned(cerr) {
			// Any other error needs to be reported.
			result.Results[i].Error = common.ServerError(cerr)
			continue
		}

		var macAddress string
		var address *state.IPAddress
		if provisionContainer {
			// Allocate and set an address.
			macAddress = generateMACAddress()
			address, err = p.allocateAddress(environ, subnet, host, container, instId, macAddress)
			if err != nil {
				err = errors.Annotatef(err, "failed to allocate an address for %q", container)
				result.Results[i].Error = common.ServerError(err)
				continue
			}
		} else {
			id := container.Id()
			addresses, err := p.st.AllocatedIPAddresses(id)
			if err != nil {
				logger.Warningf("failed to get Id for container %q: %v", tag, err)
				result.Results[i].Error = common.ServerError(err)
				continue
//.........这里部分代码省略.........

// allocateAddress tries to pick an address out of the given subnet and
// allocates it to the container.
func (p *ProvisionerAPI) allocateAddress(
	environ environs.NetworkingEnviron,
	subnet *state.Subnet,
	host, container *state.Machine,
	instId instance.Id,
	macAddress string,
) (*state.IPAddress, error) {
	hostname := containerHostname(container.Tag())

	if !environs.AddressAllocationEnabled() {
		// Even if the address allocation feature flag is not enabled, we might
		// be running on MAAS 1.8+ with devices support, which we can use to
		// register containers getting IPs via DHCP. However, most of the usual
		// allocation code can be bypassed, we just need the parent instance ID
		// and a MAC address (no subnet or IP address).
		allocatedAddress := network.Address{}
		err := environ.AllocateAddress(instId, network.AnySubnet, &allocatedAddress, macAddress, hostname)
		if err != nil {
			// Not using MAAS 1.8+ or some other error.
			return nil, errors.Trace(err)
		}

		logger.Infof(
			"allocated address %q on instance %q for container %q",
			allocatedAddress.String(), instId, hostname,
		)

		// Add the address to state, so we can look it up later by MAC address.
		stateAddr, err := p.st.AddIPAddress(allocatedAddress, string(network.AnySubnet))
		if err != nil {
			return nil, errors.Annotatef(err, "failed to save address %q", allocatedAddress)
		}

		err = p.setAllocatedOrRelease(stateAddr, environ, instId, container, network.AnySubnet, macAddress)
		if err != nil {
			return nil, errors.Trace(err)
		}

		return stateAddr, nil
	}

	subnetId := network.Id(subnet.ProviderId())
	for {
		addr, err := subnet.PickNewAddress()
		if err != nil {
			return nil, err
		}
		netAddr := addr.Address()
		logger.Tracef("picked new address %q on subnet %q", addr.String(), subnetId)
		// Attempt to allocate with environ.
		err = environ.AllocateAddress(instId, subnetId, &netAddr, macAddress, hostname)
		if err != nil {
			logger.Warningf(
				"allocating address %q on instance %q and subnet %q failed: %v (retrying)",
				addr.String(), instId, subnetId, err,
			)
			// It's as good as unavailable for us, so mark it as
			// such.
			err = setAddrState(addr, state.AddressStateUnavailable)
			if err != nil {
				logger.Warningf(
					"cannot set address %q to %q: %v (ignoring and retrying)",
					addr.String(), state.AddressStateUnavailable, err,
				)
				continue
			}
			logger.Tracef(
				"setting address %q to %q and retrying",
				addr.String(), state.AddressStateUnavailable,
			)
			continue
		}
		logger.Infof(
			"allocated address %q on instance %q and subnet %q",
			addr.String(), instId, subnetId,
		)
		err = p.setAllocatedOrRelease(addr, environ, instId, container, subnetId, macAddress)
		if err != nil {
			// Something went wrong - retry.
			continue
		}
		return addr, nil
	}
}

func prepareOrGetContainerInterfaceInfo(
	api APICalls,
	machineID string,
	bridgeDevice string,
	allocateOrMaintain bool,
	enableNAT bool,
	startingNetworkInfo []network.InterfaceInfo,
	log loggo.Logger,
	providerType string,
) ([]network.InterfaceInfo, error) {
	maintain := !allocateOrMaintain

	if environs.AddressAllocationEnabled(providerType) {
		if maintain {
			log.Debugf("running maintenance for container %q", machineID)
		} else {
			log.Debugf("trying to allocate static IP for container %q", machineID)
		}

		allocatedInfo, err := configureContainerNetwork(
			machineID,
			bridgeDevice,
			api,
			startingNetworkInfo,
			allocateOrMaintain,
			enableNAT,
		)
		if err != nil && !maintain {
			log.Infof("not allocating static IP for container %q: %v", machineID, err)
		}
		return allocatedInfo, err
	}

	if maintain {
		log.Debugf("address allocation disabled: Not running maintenance for machine %q", machineID)
		return nil, nil
	}

	log.Debugf("address allocation feature flag not enabled; using multi-bridge networking for container %q", machineID)

	// In case we're running on MAAS 1.8+ with devices support, we'll still
	// call PrepareContainerInterfaceInfo(), but we'll ignore a NotSupported
	// error if we get it (which means we're not using MAAS 1.8+).
	containerTag := names.NewMachineTag(machineID)
	preparedInfo, err := api.PrepareContainerInterfaceInfo(containerTag)
	if err != nil && errors.IsNotSupported(err) {
		log.Warningf("new container %q not registered as device: not running on MAAS 1.8+", machineID)
		return nil, nil
	} else if err != nil {
		return nil, errors.Trace(err)
	}
	log.Tracef("PrepareContainerInterfaceInfo returned %+v", preparedInfo)

	dnsServersFound := false
	for _, info := range preparedInfo {
		if len(info.DNSServers) > 0 {
			dnsServersFound = true
			break
		}
	}
	if !dnsServersFound {
		logger.Warningf("no DNS settings found, discovering the host settings")
		dnsServers, searchDomain, err := localDNSServers()
		if err != nil {
			return nil, errors.Trace(err)
		}

		// Since the result is sorted, the first entry is the primary NIC.
		preparedInfo[0].DNSServers = dnsServers
		preparedInfo[0].DNSSearchDomains = []string{searchDomain}
		logger.Debugf(
			"setting DNS servers %+v and domains %+v on container interface %q",
			preparedInfo[0].DNSServers, preparedInfo[0].DNSSearchDomains, preparedInfo[0].InterfaceName,
		)
	}

	return preparedInfo, nil
}

func prepareOrGetContainerInterfaceInfo(
	api APICalls,
	machineID string,
	bridgeDevice string,
	allocateOrMaintain bool,
	enableNAT bool,
	startingNetworkInfo []network.InterfaceInfo,
	log loggo.Logger,
) ([]network.InterfaceInfo, error) {
	maintain := !allocateOrMaintain

	if environs.AddressAllocationEnabled() {
		if maintain {
			log.Debugf("running maintenance for container %q", machineID)
		} else {
			log.Debugf("trying to allocate static IP for container %q", machineID)
		}

		allocatedInfo, err := configureContainerNetwork(
			machineID,
			bridgeDevice,
			api,
			startingNetworkInfo,
			allocateOrMaintain,
			enableNAT,
		)
		if err != nil && !maintain {
			log.Infof("not allocating static IP for container %q: %v", machineID, err)
		}
		return allocatedInfo, err
	}

	if maintain {
		log.Debugf("address allocation disabled: Not running maintenance for machine %q", machineID)
		return nil, nil
	}

	log.Debugf("address allocation feature flag not enabled; using DHCP for container %q", machineID)

	// In case we're running on MAAS 1.8+ with devices support, we'll still
	// call PrepareContainerInterfaceInfo(), but we'll ignore a NotSupported
	// error if we get it (which means we're not using MAAS 1.8+).
	containerTag := names.NewMachineTag(machineID)
	preparedInfo, err := api.PrepareContainerInterfaceInfo(containerTag)
	if err != nil && errors.IsNotSupported(err) {
		log.Warningf("new container %q not registered as device: not running on MAAS 1.8+", machineID)
		return nil, nil
	} else if err != nil {
		return nil, errors.Trace(err)
	}

	dnsServers, searchDomain, dnsErr := localDNSServers()

	if dnsErr != nil {
		return nil, errors.Trace(dnsErr)
	}

	for i, _ := range preparedInfo {
		preparedInfo[i].DNSServers = dnsServers
		preparedInfo[i].DNSSearch = searchDomain
	}

	log.Tracef("PrepareContainerInterfaceInfo returned %#v", preparedInfo)
	// Most likely there will be only one item in the list, but check
	// all of them for forward compatibility.
	macAddresses := set.NewStrings()
	for _, prepInfo := range preparedInfo {
		macAddresses.Add(prepInfo.MACAddress)
	}
	log.Infof(
		"new container %q registered as a MAAS device with MAC address(es) %v",
		machineID, macAddresses.SortedValues(),
	)
	return preparedInfo, nil
}

// ReleaseContainerAddresses finds addresses allocated to a container
// and marks them as Dead, to be released and removed. It accepts
// container tags as arguments. If address allocation feature flag is
// not enabled, it will return a NotSupported error.
func (p *ProvisionerAPI) ReleaseContainerAddresses(args params.Entities) (params.ErrorResults, error) {
	result := params.ErrorResults{
		Results: make([]params.ErrorResult, len(args.Entities)),
	}

	if !environs.AddressAllocationEnabled() {
		return result, errors.NotSupportedf("address allocation")
	}

	canAccess, err := p.getAuthFunc()
	if err != nil {
		logger.Errorf("failed to get an authorisation function: %v", err)
		return result, errors.Trace(err)
	}
	// Loop over the passed container tags.
	for i, entity := range args.Entities {
		tag, err := names.ParseMachineTag(entity.Tag)
		if err != nil {
			logger.Warningf("failed to parse machine tag %q: %v", entity.Tag, err)
			result.Results[i].Error = common.ServerError(common.ErrPerm)
			continue
		}

		// The auth function (canAccess) checks that the machine is a
		// top level machine (we filter those out next) or that the
		// machine has the host as a parent.
		container, err := p.getMachine(canAccess, tag)
		if err != nil {
			logger.Warningf("failed to get machine %q: %v", tag, err)
			result.Results[i].Error = common.ServerError(err)
			continue
		} else if !container.IsContainer() {
			err = errors.Errorf("cannot mark addresses for removal for %q: not a container", tag)
			result.Results[i].Error = common.ServerError(err)
			continue
		}

		id := container.Id()
		addresses, err := p.st.AllocatedIPAddresses(id)
		if err != nil {
			logger.Warningf("failed to get Id for container %q: %v", tag, err)
			result.Results[i].Error = common.ServerError(err)
			continue
		}

		deadErrors := []error{}
		logger.Debugf("for container %q found addresses %v", tag, addresses)
		for _, addr := range addresses {
			err = addr.EnsureDead()
			if err != nil {
				deadErrors = append(deadErrors, err)
				continue
			}
		}
		if len(deadErrors) != 0 {
			err = errors.Errorf("failed to mark all addresses for removal for %q: %v", tag, deadErrors)
			result.Results[i].Error = common.ServerError(err)
		}
	}

	return result, nil
}

// StartInstance is specified in the Broker interface.
func (broker *kvmBroker) StartInstance(args environs.StartInstanceParams) (*environs.StartInstanceResult, error) {
	if args.InstanceConfig.HasNetworks() {
		return nil, errors.New("starting kvm containers with networks is not supported yet")
	}
	// TODO: refactor common code out of the container brokers.
	machineId := args.InstanceConfig.MachineId
	kvmLogger.Infof("starting kvm container for machineId: %s", machineId)

	// TODO: Default to using the host network until we can configure.  Yes,
	// this is using the LxcBridge value, we should put it in the api call for
	// container config.
	bridgeDevice := broker.agentConfig.Value(agent.LxcBridge)
	if bridgeDevice == "" {
		bridgeDevice = kvm.DefaultKvmBridge
	}
	if !environs.AddressAllocationEnabled() {
		logger.Debugf(
			"address allocation feature flag not enabled; using DHCP for container %q",
			machineId,
		)
	} else {
		logger.Debugf("trying to allocate static IP for container %q", machineId)

		allocatedInfo, err := configureContainerNetwork(
			machineId,
			bridgeDevice,
			broker.api,
			args.NetworkInfo,
			true, // allocate a new address.
			broker.enableNAT,
		)
		if err != nil {
			// It's fine, just ignore it. The effect will be that the
			// container won't have a static address configured.
			logger.Infof("not allocating static IP for container %q: %v", machineId, err)
		} else {
			args.NetworkInfo = allocatedInfo
		}
	}

	// Unlike with LXC, we don't override the default MTU to use.
	network := container.BridgeNetworkConfig(bridgeDevice, 0, args.NetworkInfo)

	series := args.Tools.OneSeries()
	args.InstanceConfig.MachineContainerType = instance.KVM
	args.InstanceConfig.Tools = args.Tools[0]

	config, err := broker.api.ContainerConfig()
	if err != nil {
		kvmLogger.Errorf("failed to get container config: %v", err)
		return nil, err
	}

	if err := instancecfg.PopulateInstanceConfig(
		args.InstanceConfig,
		config.ProviderType,
		config.AuthorizedKeys,
		config.SSLHostnameVerification,
		config.Proxy,
		config.AptProxy,
		config.AptMirror,
		config.PreferIPv6,
		config.EnableOSRefreshUpdate,
		config.EnableOSUpgrade,
	); err != nil {
		kvmLogger.Errorf("failed to populate machine config: %v", err)
		return nil, err
	}

	storageConfig := &container.StorageConfig{
		AllowMount: true,
	}
	inst, hardware, err := broker.manager.CreateContainer(args.InstanceConfig, series, network, storageConfig)
	if err != nil {
		kvmLogger.Errorf("failed to start container: %v", err)
		return nil, err
	}
	kvmLogger.Infof("started kvm container for machineId: %s, %s, %s", machineId, inst.Id(), hardware.String())
	return &environs.StartInstanceResult{
		Instance:    inst,
		Hardware:    hardware,
		NetworkInfo: network.Interfaces,
	}, nil
}

func shutdownInitCommands(initSystem, series string) ([]string, error) {
	// These files are removed just before the template shuts down.
	cleanupOnShutdown := []string{
		// We remove any dhclient lease files so there's no chance a
		// clone to reuse a lease from the template it was cloned
		// from.
		"/var/lib/dhcp/dhclient*",
		// Both of these sets of files below are recreated on boot and
		// if we leave them in the template's rootfs boot logs coming
		// from cloned containers will be appended. It's better to
		// keep clean logs for diagnosing issues / debugging.
		"/var/log/cloud-init*.log",
	}

	// Using EOC below as the template shutdown script is itself
	// passed through cat > ... < EOF.
	replaceNetConfCmd := fmt.Sprintf(
		"/bin/cat > /etc/network/interfaces << EOC%sEOC\n  ",
		defaultEtcNetworkInterfaces,
	)
	paths := strings.Join(cleanupOnShutdown, " ")
	removeCmd := fmt.Sprintf("/bin/rm -fr %s\n  ", paths)
	shutdownCmd := "/sbin/shutdown -h now"
	name := "juju-template-restart"
	desc := "juju shutdown job"

	execStart := shutdownCmd
	if environs.AddressAllocationEnabled() {
		// Only do the cleanup and replacement of /e/n/i when address
		// allocation feature flag is enabled.
		execStart = replaceNetConfCmd + removeCmd + shutdownCmd
	}

	conf := common.Conf{
		Desc:         desc,
		Transient:    true,
		AfterStopped: "cloud-final",
		ExecStart:    execStart,
	}
	// systemd uses targets for synchronization of services
	if initSystem == service.InitSystemSystemd {
		conf.AfterStopped = "cloud-config.target"
	}

	svc, err := service.NewService(name, conf, series)
	if err != nil {
		return nil, errors.Trace(err)
	}

	cmds, err := svc.InstallCommands()
	if err != nil {
		return nil, errors.Trace(err)
	}

	startCommands, err := svc.StartCommands()
	if err != nil {
		return nil, errors.Trace(err)
	}
	cmds = append(cmds, startCommands...)

	return cmds, nil
}

// StartInstance is specified in the Broker interface.
func (broker *lxcBroker) StartInstance(args environs.StartInstanceParams) (*environs.StartInstanceResult, error) {
	if args.InstanceConfig.HasNetworks() {
		return nil, errors.New("starting lxc containers with networks is not supported yet")
	}
	// TODO: refactor common code out of the container brokers.
	machineId := args.InstanceConfig.MachineId
	lxcLogger.Infof("starting lxc container for machineId: %s", machineId)

	// Default to using the host network until we can configure.
	bridgeDevice := broker.agentConfig.Value(agent.LxcBridge)
	if bridgeDevice == "" {
		bridgeDevice = lxc.DefaultLxcBridge
	}

	if !environs.AddressAllocationEnabled() {
		logger.Debugf(
			"address allocation feature flag not enabled; using DHCP for container %q",
			machineId,
		)
	} else {
		logger.Debugf("trying to allocate static IP for container %q", machineId)
		allocatedInfo, err := configureContainerNetwork(
			machineId,
			bridgeDevice,
			broker.api,
			args.NetworkInfo,
			true, // allocate a new address.
			broker.enableNAT,
		)
		if err != nil {
			// It's fine, just ignore it. The effect will be that the
			// container won't have a static address configured.
			logger.Infof("not allocating static IP for container %q: %v", machineId, err)
		} else {
			args.NetworkInfo = allocatedInfo
		}
	}
	network := container.BridgeNetworkConfig(bridgeDevice, broker.defaultMTU, args.NetworkInfo)

	// The provisioner worker will provide all tools it knows about
	// (after applying explicitly specified constraints), which may
	// include tools for architectures other than the host's. We
	// must constrain to the host's architecture for LXC.
	archTools, err := args.Tools.Match(tools.Filter{
		Arch: version.Current.Arch,
	})
	if err == tools.ErrNoMatches {
		return nil, errors.Errorf(
			"need tools for arch %s, only found %s",
			version.Current.Arch,
			args.Tools.Arches(),
		)
	}

	series := archTools.OneSeries()
	args.InstanceConfig.MachineContainerType = instance.LXC
	args.InstanceConfig.Tools = archTools[0]

	config, err := broker.api.ContainerConfig()
	if err != nil {
		lxcLogger.Errorf("failed to get container config: %v", err)
		return nil, err
	}
	storageConfig := &container.StorageConfig{
		AllowMount: config.AllowLXCLoopMounts,
	}

	if err := instancecfg.PopulateInstanceConfig(
		args.InstanceConfig,
		config.ProviderType,
		config.AuthorizedKeys,
		config.SSLHostnameVerification,
		config.Proxy,
		config.AptProxy,
		config.AptMirror,
		config.PreferIPv6,
		config.EnableOSRefreshUpdate,
		config.EnableOSUpgrade,
	); err != nil {
		lxcLogger.Errorf("failed to populate machine config: %v", err)
		return nil, err
	}

	inst, hardware, err := broker.manager.CreateContainer(args.InstanceConfig, series, network, storageConfig)
	if err != nil {
		lxcLogger.Errorf("failed to start container: %v", err)
		return nil, err
	}
	lxcLogger.Infof("started lxc container for machineId: %s, %s, %s", machineId, inst.Id(), hardware.String())
	return &environs.StartInstanceResult{
		Instance:    inst,
		Hardware:    hardware,
		NetworkInfo: network.Interfaces,
	}, nil
}