func (r *DrvRegistry) registerIpamDriver(name string, driver ipamapi.Ipam, caps *ipamapi.Capability) error {
	if strings.TrimSpace(name) == "" {
		return fmt.Errorf("ipam driver name string cannot be empty")
	}

	r.Lock()
	_, ok := r.ipamDrivers[name]
	r.Unlock()
	if ok {
		return types.ForbiddenErrorf("ipam driver %q already registered", name)
	}

	locAS, glbAS, err := driver.GetDefaultAddressSpaces()
	if err != nil {
		return types.InternalErrorf("ipam driver %q failed to return default address spaces: %v", name, err)
	}

	if r.ifn != nil {
		if err := r.ifn(name, driver, caps); err != nil {
			return err
		}
	}

	r.Lock()
	r.ipamDrivers[name] = &ipamData{driver: driver, defaultLocalAddressSpace: locAS, defaultGlobalAddressSpace: glbAS, capability: caps}
	r.Unlock()

	return nil
}

func (ep *endpoint) assignAddress() error {
	var (
		ipam ipamapi.Ipam
		err  error
	)
	n := ep.getNetwork()
	if n.Type() == "host" || n.Type() == "null" || n.Type() == "bridge" {
		return nil
	}
	ipam, err = n.getController().getIpamDriver(n.ipamType)
	if err != nil {
		return err
	}
	for _, d := range n.getIPInfo() {
		var addr *net.IPNet
		addr, _, err = ipam.RequestAddress(d.PoolID, nil, nil)
		if err == nil {
			ep.Lock()
			ep.iface.addr = addr
			ep.iface.poolID = d.PoolID
			ep.Unlock()
			return nil
		}
		if err != ipamapi.ErrNoAvailableIPs {
			return err
		}
	}
	return fmt.Errorf("no available ip addresses on this network address pools: %s (%s)", n.Name(), n.ID())
}

func (ep *endpoint) assignAddressVersion(ipVer int, ipam ipamapi.Ipam) error {
	var (
		poolID  *string
		address **net.IPNet
		prefAdd net.IP
		progAdd net.IP
	)

	n := ep.getNetwork()
	switch ipVer {
	case 4:
		poolID = &ep.iface.v4PoolID
		address = &ep.iface.addr
		prefAdd = ep.prefAddress
	case 6:
		poolID = &ep.iface.v6PoolID
		address = &ep.iface.addrv6
		prefAdd = ep.prefAddressV6
	default:
		return types.InternalErrorf("incorrect ip version number passed: %d", ipVer)
	}

	ipInfo := n.getIPInfo(ipVer)

	// ipv6 address is not mandatory
	if len(ipInfo) == 0 && ipVer == 6 {
		return nil
	}

	// The address to program may be chosen by the user or by the network driver in one specific
	// case to support backward compatibility with `docker daemon --fixed-cidrv6` use case
	if prefAdd != nil {
		progAdd = prefAdd
	} else if *address != nil {
		progAdd = (*address).IP
	}

	for _, d := range ipInfo {
		if progAdd != nil && !d.Pool.Contains(progAdd) {
			continue
		}
		addr, _, err := ipam.RequestAddress(d.PoolID, progAdd, ep.ipamOptions)
		if err == nil {
			ep.Lock()
			*address = addr
			*poolID = d.PoolID
			ep.Unlock()
			return nil
		}
		if err != ipamapi.ErrNoAvailableIPs || progAdd != nil {
			return err
		}
	}
	if progAdd != nil {
		return types.BadRequestErrorf("Invalid address %s: It does not belong to any of this network's subnets", prefAdd)
	}
	return fmt.Errorf("no available IPv%d addresses on this network's address pools: %s (%s)", ipVer, n.Name(), n.ID())
}

func releasePools(ipam ipamapi.Ipam, icList []*api.IPAMConfig, pools map[string]string) {
	for _, ic := range icList {
		if err := ipam.ReleaseAddress(pools[ic.Subnet], net.ParseIP(ic.Gateway)); err != nil {
			log.G(context.TODO()).Errorf("Failed to release address %s: %v", ic.Subnet, err)
		}
	}

	for k, p := range pools {
		if err := ipam.ReleasePool(p); err != nil {
			log.G(context.TODO()).Errorf("Failed to release pool %s: %v", k, err)
		}
	}
}

func (ep *endpoint) assignAddressVersion(ipVer int, ipam ipamapi.Ipam) error {
	var (
		poolID  *string
		address **net.IPNet
	)

	n := ep.getNetwork()
	switch ipVer {
	case 4:
		poolID = &ep.iface.v4PoolID
		address = &ep.iface.addr
	case 6:
		poolID = &ep.iface.v6PoolID
		address = &ep.iface.addrv6
	default:
		return types.InternalErrorf("incorrect ip version number passed: %d", ipVer)
	}

	ipInfo := n.getIPInfo(ipVer)

	// ipv6 address is not mandatory
	if len(ipInfo) == 0 && ipVer == 6 {
		return nil
	}

	for _, d := range ipInfo {
		var prefIP net.IP
		if *address != nil {
			prefIP = (*address).IP
		}
		addr, _, err := ipam.RequestAddress(d.PoolID, prefIP, nil)
		if err == nil {
			ep.Lock()
			*address = addr
			*poolID = d.PoolID
			ep.Unlock()
			return nil
		}
		if err != ipamapi.ErrNoAvailableIPs {
			return err
		}
	}
	return fmt.Errorf("no available IPv%d addresses on this network's address pools: %s (%s)", ipVer, n.Name(), n.ID())
}

func (n *network) requestPoolHelper(ipam ipamapi.Ipam, addressSpace, preferredPool, subPool string, options map[string]string, v6 bool) (string, *net.IPNet, map[string]string, error) {
	for {
		poolID, pool, meta, err := ipam.RequestPool(addressSpace, preferredPool, subPool, options, v6)
		if err != nil {
			return "", nil, nil, err
		}

		// If the network belongs to global scope or the pool was
		// explicitely chosen or it is invalid, do not perform the overlap check.
		if n.Scope() == datastore.GlobalScope || preferredPool != "" || !types.IsIPNetValid(pool) {
			return poolID, pool, meta, nil
		}

		// Check for overlap and if none found, we have found the right pool.
		if _, err := netutils.FindAvailableNetwork([]*net.IPNet{pool}); err == nil {
			return poolID, pool, meta, nil
		}

		// Pool obtained in this iteration is
		// overlapping. Hold onto the pool and don't release
		// it yet, because we don't want ipam to give us back
		// the same pool over again. But make sure we still do
		// a deferred release when we have either obtained a
		// non-overlapping pool or ran out of pre-defined
		// pools.
		defer func() {
			if err := ipam.ReleasePool(poolID); err != nil {
				log.Warnf("Failed to release overlapping pool %s while returning from pool request helper for network %s", pool, n.Name())
			}
		}()

		// If this is a preferred pool request and the network
		// is local scope and there is a overlap, we fail the
		// network creation right here. The pool will be
		// released in the defer.
		if preferredPool != "" {
			return "", nil, nil, fmt.Errorf("requested subnet %s overlaps in the host", preferredPool)
		}
	}
}

func (c *controller) RegisterIpamDriver(name string, driver ipamapi.Ipam) error {
	if !config.IsValidName(name) {
		return ErrInvalidName(name)
	}

	c.Lock()
	_, ok := c.ipamDrivers[name]
	c.Unlock()
	if ok {
		return driverapi.ErrActiveRegistration(name)
	}
	locAS, glbAS, err := driver.GetDefaultAddressSpaces()
	if err != nil {
		return fmt.Errorf("ipam driver %s failed to return default address spaces: %v", name, err)
	}
	c.Lock()
	c.ipamDrivers[name] = &ipamData{driver: driver, defaultLocalAddressSpace: locAS, defaultGlobalAddressSpace: glbAS}
	c.Unlock()

	log.Debugf("Registering ipam provider: %s", name)

	return nil
}

func (c *controller) registerIpamDriver(name string, driver ipamapi.Ipam, caps *ipamapi.Capability) error {
	if !config.IsValidName(name) {
		return ErrInvalidName(name)
	}

	c.Lock()
	_, ok := c.ipamDrivers[name]
	c.Unlock()
	if ok {
		return types.ForbiddenErrorf("ipam driver %q already registered", name)
	}
	locAS, glbAS, err := driver.GetDefaultAddressSpaces()
	if err != nil {
		return types.InternalErrorf("ipam driver %q failed to return default address spaces: %v", name, err)
	}
	c.Lock()
	c.ipamDrivers[name] = &ipamData{driver: driver, defaultLocalAddressSpace: locAS, defaultGlobalAddressSpace: glbAS, capability: caps}
	c.Unlock()

	log.Debugf("Registering ipam driver: %q", name)

	return nil
}

func (n *network) ipamReleaseVersion(ipVer int, ipam ipamapi.Ipam) {
	var infoList *[]*IpamInfo

	switch ipVer {
	case 4:
		infoList = &n.ipamV4Info
	case 6:
		infoList = &n.ipamV6Info
	default:
		log.Warnf("incorrect ip version passed to ipam release: %d", ipVer)
		return
	}

	if len(*infoList) == 0 {
		return
	}

	log.Debugf("releasing IPv%d pools from network %s (%s)", ipVer, n.Name(), n.ID())

	for _, d := range *infoList {
		if d.Gateway != nil {
			if err := ipam.ReleaseAddress(d.PoolID, d.Gateway.IP); err != nil {
				log.Warnf("Failed to release gateway ip address %s on delete of network %s (%s): %v", d.Gateway.IP, n.Name(), n.ID(), err)
			}
		}
		if d.IPAMData.AuxAddresses != nil {
			for k, nw := range d.IPAMData.AuxAddresses {
				if d.Pool.Contains(nw.IP) {
					if err := ipam.ReleaseAddress(d.PoolID, nw.IP); err != nil && err != ipamapi.ErrIPOutOfRange {
						log.Warnf("Failed to release secondary ip address %s (%v) on delete of network %s (%s): %v", k, nw.IP, n.Name(), n.ID(), err)
					}
				}
			}
		}
		if err := ipam.ReleasePool(d.PoolID); err != nil {
			log.Warnf("Failed to release address pool %s on delete of network %s (%s): %v", d.PoolID, n.Name(), n.ID(), err)
		}
	}

	*infoList = nil
}

func (n *network) ipamAllocateVersion(ipVer int, ipam ipamapi.Ipam) error {
	var (
		cfgList  *[]*IpamConf
		infoList *[]*IpamInfo
		err      error
	)

	switch ipVer {
	case 4:
		cfgList = &n.ipamV4Config
		infoList = &n.ipamV4Info
	case 6:
		cfgList = &n.ipamV6Config
		infoList = &n.ipamV6Info
	default:
		return types.InternalErrorf("incorrect ip version passed to ipam allocate: %d", ipVer)
	}

	if len(*cfgList) == 0 {
		if ipVer == 6 {
			return nil
		}
		*cfgList = []*IpamConf{{}}
	}

	*infoList = make([]*IpamInfo, len(*cfgList))

	log.Debugf("Allocating IPv%d pools for network %s (%s)", ipVer, n.Name(), n.ID())

	for i, cfg := range *cfgList {
		if err = cfg.Validate(); err != nil {
			return err
		}
		d := &IpamInfo{}
		(*infoList)[i] = d

		d.AddressSpace = n.addrSpace
		d.PoolID, d.Pool, d.Meta, err = n.requestPoolHelper(ipam, n.addrSpace, cfg.PreferredPool, cfg.SubPool, n.ipamOptions, ipVer == 6)
		if err != nil {
			return err
		}

		defer func() {
			if err != nil {
				if err := ipam.ReleasePool(d.PoolID); err != nil {
					log.Warnf("Failed to release address pool %s after failure to create network %s (%s)", d.PoolID, n.Name(), n.ID())
				}
			}
		}()

		if gws, ok := d.Meta[netlabel.Gateway]; ok {
			if d.Gateway, err = types.ParseCIDR(gws); err != nil {
				return types.BadRequestErrorf("failed to parse gateway address (%v) returned by ipam driver: %v", gws, err)
			}
		}

		// If user requested a specific gateway, libnetwork will allocate it
		// irrespective of whether ipam driver returned a gateway already.
		// If none of the above is true, libnetwork will allocate one.
		if cfg.Gateway != "" || d.Gateway == nil {
			var gatewayOpts = map[string]string{
				ipamapi.RequestAddressType: netlabel.Gateway,
			}
			if d.Gateway, _, err = ipam.RequestAddress(d.PoolID, net.ParseIP(cfg.Gateway), gatewayOpts); err != nil {
				return types.InternalErrorf("failed to allocate gateway (%v): %v", cfg.Gateway, err)
			}
		}

		// Auxiliary addresses must be part of the master address pool
		// If they fall into the container addressable pool, libnetwork will reserve them
		if cfg.AuxAddresses != nil {
			var ip net.IP
			d.IPAMData.AuxAddresses = make(map[string]*net.IPNet, len(cfg.AuxAddresses))
			for k, v := range cfg.AuxAddresses {
				if ip = net.ParseIP(v); ip == nil {
					return types.BadRequestErrorf("non parsable secondary ip address (%s:%s) passed for network %s", k, v, n.Name())
				}
				if !d.Pool.Contains(ip) {
					return types.ForbiddenErrorf("auxilairy address: (%s:%s) must belong to the master pool: %s", k, v, d.Pool)
				}
				// Attempt reservation in the container addressable pool, silent the error if address does not belong to that pool
				if d.IPAMData.AuxAddresses[k], _, err = ipam.RequestAddress(d.PoolID, ip, nil); err != nil && err != ipamapi.ErrIPOutOfRange {
					return types.InternalErrorf("failed to allocate secondary ip address (%s:%s): %v", k, v, err)
				}
			}
		}
	}

	return nil
}