// Copyright (C) 2014-2019 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#include <config.h>
#include <dhcp/iface_mgr.h>
#include <dhcp/option_custom.h>
#include <dhcpsrv/cfg_subnets4.h>
#include <dhcpsrv/dhcpsrv_log.h>
#include <dhcpsrv/lease_mgr_factory.h>
#include <dhcpsrv/shared_network.h>
#include <dhcpsrv/subnet_id.h>
#include <asiolink/io_address.h>
#include <asiolink/addr_utilities.h>
#include <stats/stats_mgr.h>
#include <sstream>

using namespace isc::asiolink;
using namespace isc::data;

namespace isc {
namespace dhcp {

void
CfgSubnets4::add(const Subnet4Ptr& subnet) {
    if (getBySubnetId(subnet->getID())) {
        isc_throw(isc::dhcp::DuplicateSubnetID, "ID of the new IPv4 subnet '"
                  << subnet->getID() << "' is already in use");

    } else if (getByPrefix(subnet->toText())) {
        /// @todo: Check that this new subnet does not cross boundaries of any
        /// other already defined subnet.
        isc_throw(isc::dhcp::DuplicateSubnetID, "subnet with the prefix of '"
                  << subnet->toText() << "' already exists");
    }

    LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE, DHCPSRV_CFGMGR_ADD_SUBNET4)
              .arg(subnet->toText());
    subnets_.push_back(subnet);
}

void
CfgSubnets4::del(const ConstSubnet4Ptr& subnet) {
    auto& index = subnets_.get<SubnetSubnetIdIndexTag>();
    auto subnet_it = index.find(subnet->getID());
    if (subnet_it == index.end()) {
        isc_throw(BadValue, "no subnet with ID of '" << subnet->getID()
                  << "' found");
    }
    index.erase(subnet_it);

    LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE, DHCPSRV_CFGMGR_DEL_SUBNET4)
        .arg(subnet->toText());
}

void
CfgSubnets4::merge(CfgSharedNetworks4Ptr networks,
                   const CfgSubnets4& other) {
    auto& index = subnets_.get<SubnetSubnetIdIndexTag>();

    // Iterate over the subnets to be merged. They will replace the existing
    // subnets with the same id. All new subnets will be inserted into the
    // configuration into which we're merging.
    auto other_subnets = other.getAll();
    for (auto other_subnet = other_subnets->begin(); other_subnet != other_subnets->end();
         ++other_subnet) {

        // Check if there is a subnet with the same ID.
        auto subnet_it = index.find((*other_subnet)->getID());
        if (subnet_it != index.end()) {

            // Subnet found.
            auto existing_subnet = *subnet_it;

            // Continue if the existing subnet and other subnet
            // are the same instance skip it.
            if (existing_subnet == *other_subnet) {
                continue;
            }

            // We're going to replace the existing subnet with the other
            // version. If it belongs to a shared network, we need
            // remove it from that network.
            SharedNetwork4Ptr network;
            existing_subnet->getSharedNetwork(network);
            if (network) {
                network->del(existing_subnet->getID());
            }

            // Now we remove the existing subnet.
            index.erase(subnet_it);
        }

        // Add the "other" subnet to the our collection of subnets.
        subnets_.push_back(*other_subnet);

        // If it belongs to a shared network, find the network and
        // add the subnet to it
        std::string network_name = (*other_subnet)->getSharedNetworkName();
        if (!network_name.empty()) {
            SharedNetwork4Ptr network = networks->getByName(network_name);
            if (network) {
                network->add(*other_subnet);
            } else {
                // This implies the shared-network collection we were given
                // is out of sync with the subnets we were given.
                isc_throw(InvalidOperation, "Cannot assign subnet ID of '"
                          << (*other_subnet)->getID()
                          << " to shared network: " << network_name
                          << ", network does not exist");
            }
        }
    }
}

ConstSubnet4Ptr
CfgSubnets4::getBySubnetId(const SubnetID& subnet_id) const {
    const auto& index = subnets_.get<SubnetSubnetIdIndexTag>();
    auto subnet_it = index.find(subnet_id);
    return ((subnet_it != index.cend()) ? (*subnet_it) : ConstSubnet4Ptr());
}

ConstSubnet4Ptr
CfgSubnets4::getByPrefix(const std::string& subnet_text) const {
    const auto& index = subnets_.get<SubnetPrefixIndexTag>();
    auto subnet_it = index.find(subnet_text);
    return ((subnet_it != index.cend()) ? (*subnet_it) : ConstSubnet4Ptr());
}

bool
CfgSubnets4::hasSubnetWithServerId(const asiolink::IOAddress& server_id) const {
    const auto& index = subnets_.get<SubnetServerIdIndexTag>();
    auto subnet_it = index.find(server_id);
    return (subnet_it != index.cend());
}

SubnetSelector
CfgSubnets4::initSelector(const Pkt4Ptr& query) {
    SubnetSelector selector;
    selector.ciaddr_ = query->getCiaddr();
    selector.giaddr_ = query->getGiaddr();
    selector.local_address_ = query->getLocalAddr();
    selector.remote_address_ = query->getRemoteAddr();
    selector.client_classes_ = query->classes_;
    selector.iface_name_ = query->getIface();

    // If the link-selection sub-option is present, extract its value.
    // "The link-selection sub-option is used by any DHCP relay agent
    // that desires to specify a subnet/link for a DHCP client request
    // that it is relaying but needs the subnet/link specification to
    // be different from the IP address the DHCP server should use
    // when communicating with the relay agent." (RFC 3527)
    //
    // Try first Relay Agent Link Selection sub-option
    OptionPtr rai = query->getOption(DHO_DHCP_AGENT_OPTIONS);
    if (rai) {
        OptionCustomPtr rai_custom =
            boost::dynamic_pointer_cast<OptionCustom>(rai);
        if (rai_custom) {
            OptionPtr link_select =
                rai_custom->getOption(RAI_OPTION_LINK_SELECTION);
            if (link_select) {
                OptionBuffer link_select_buf = link_select->getData();
                if (link_select_buf.size() == sizeof(uint32_t)) {
                    selector.option_select_ =
                        IOAddress::fromBytes(AF_INET, &link_select_buf[0]);
                }
            }
        }
    } else {
        // Or Subnet Selection option
        OptionPtr sbnsel = query->getOption(DHO_SUBNET_SELECTION);
        if (sbnsel) {
            OptionCustomPtr oc =
                boost::dynamic_pointer_cast<OptionCustom>(sbnsel);
            if (oc) {
                selector.option_select_ = oc->readAddress();
            }
        }
    }

    return (selector);
}

Subnet4Ptr
CfgSubnets4::selectSubnet4o6(const SubnetSelector& selector) const {

    for (Subnet4Collection::const_iterator subnet = subnets_.begin();
         subnet != subnets_.end(); ++subnet) {
        Cfg4o6& cfg4o6 = (*subnet)->get4o6();

        // Is this an 4o6 subnet at all?
        if (!cfg4o6.enabled()) {
            continue; // No? Let's try the next one.
        }

        // First match criteria: check if we have a prefix/len defined.
        std::pair<asiolink::IOAddress, uint8_t> pref = cfg4o6.getSubnet4o6();
        if (!pref.first.isV6Zero()) {

            // Let's check if the IPv6 address is in range
            IOAddress first = firstAddrInPrefix(pref.first, pref.second);
            IOAddress last = lastAddrInPrefix(pref.first, pref.second);
            if ((first <= selector.remote_address_) &&
                (selector.remote_address_ <= last)) {
                return (*subnet);
            }
        }

        // Second match criteria: check if the interface-id matches
        if (cfg4o6.getInterfaceId() && selector.interface_id_ &&
            cfg4o6.getInterfaceId()->equals(selector.interface_id_)) {
            return (*subnet);
        }

        // Third match criteria: check if the interface name matches
        if (!cfg4o6.getIface4o6().empty() && !selector.iface_name_.empty()
            && cfg4o6.getIface4o6() == selector.iface_name_) {
            return (*subnet);
        }
    }

    // Ok, wasn't able to find any matching subnet.
    return (Subnet4Ptr());
}

Subnet4Ptr
CfgSubnets4::selectSubnet(const SubnetSelector& selector) const {

    // First use RAI link select sub-option or subnet select option
    if (!selector.option_select_.isV4Zero()) {
        return (selectSubnet(selector.option_select_,
                             selector.client_classes_));
    }

    // If relayed message has been received, try to match the giaddr with the
    // relay address specified for a subnet and/or shared network. It is also
    // possible that the relay address will not match with any of the relay
    // addresses across all subnets, but we need to verify that for all subnets
    // before we can try to use the giaddr to match with the subnet prefix.
    if (!selector.giaddr_.isV4Zero()) {
        for (Subnet4Collection::const_iterator subnet = subnets_.begin();
             subnet != subnets_.end(); ++subnet) {

            // If relay information is specified for this subnet, it must match.
            // Otherwise, we ignore this subnet.
            if ((*subnet)->hasRelays()) {
                if (!(*subnet)->hasRelayAddress(selector.giaddr_)) {
                    continue;
                }
            } else {
                // Relay information is not specified on the subnet level,
                // so let's try matching on the shared network level.
                SharedNetwork4Ptr network;
                (*subnet)->getSharedNetwork(network);
                if (!network || !(network->hasRelayAddress(selector.giaddr_))) {
                    continue;
                }
            }

            // If a subnet meets the client class criteria return it.
            if ((*subnet)->clientSupported(selector.client_classes_)) {
                return (*subnet);
            }
        }
    }

    // If we got to this point it means that we were not able to match the
    // giaddr with any of the addresses specified for subnets. Let's determine
    // what address from the client's packet to use to match with the
    // subnets' prefixes.

    IOAddress address = IOAddress::IPV4_ZERO_ADDRESS();
    // If there is a giaddr, use it for subnet selection.
    if (!selector.giaddr_.isV4Zero()) {
        address = selector.giaddr_;

    // If it is a Renew or Rebind, use the ciaddr.
    } else if (!selector.ciaddr_.isV4Zero() &&
               !selector.local_address_.isV4Bcast()) {
        address = selector.ciaddr_;

    // If ciaddr is not specified, use the source address.
    } else if (!selector.remote_address_.isV4Zero() &&
               !selector.local_address_.isV4Bcast()) {
        address = selector.remote_address_;

    // If local interface name is known, use the local address on this
    // interface.
    } else if (!selector.iface_name_.empty()) {
        IfacePtr iface = IfaceMgr::instance().getIface(selector.iface_name_);
        // This should never happen in the real life. Hence we throw an
        // exception.
        if (iface == NULL) {
            isc_throw(isc::BadValue, "interface " << selector.iface_name_
                      << " doesn't exist and therefore it is impossible"
                      " to find a suitable subnet for its IPv4 address");
        }

        // Attempt to select subnet based on the interface name.
        Subnet4Ptr subnet = selectSubnet(selector.iface_name_,
                                         selector.client_classes_);

        // If it matches - great. If not, we'll try to use a different
        // selection criteria below.
        if (subnet) {
            return (subnet);
        } else {
            // Let's try to get an address from the local interface and
            // try to match it to defined subnet.
            iface->getAddress4(address);
        }
    }

    // Unable to find a suitable address to use for subnet selection.
    if (address.isV4Zero()) {
        return (Subnet4Ptr());
    }

    // We have identified an address in the client's packet that can be
    // used for subnet selection. Match this packet with the subnets.
    return (selectSubnet(address, selector.client_classes_));
}

Subnet4Ptr
CfgSubnets4::selectSubnet(const std::string& iface,
                          const ClientClasses& client_classes) const {
    for (Subnet4Collection::const_iterator subnet = subnets_.begin();
         subnet != subnets_.end(); ++subnet) {

        Subnet4Ptr subnet_selected;

        // First, try subnet specific interface name.
        if (!(*subnet)->getIface().empty()) {
            if ((*subnet)->getIface() == iface) {
                subnet_selected = (*subnet);
            }

        } else {
            // Interface not specified for a subnet, so let's try if
            // we can match with shared network specific setting of
            // the interface.
            SharedNetwork4Ptr network;
            (*subnet)->getSharedNetwork(network);
            if (network && !network->getIface().empty() &&
                (network->getIface() == iface)) {
                subnet_selected = (*subnet);
            }
        }

        if (subnet_selected) {

            // If a subnet meets the client class criteria return it.
            if (subnet_selected->clientSupported(client_classes)) {
                LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE,
                          DHCPSRV_CFGMGR_SUBNET4_IFACE)
                    .arg((*subnet)->toText())
                    .arg(iface);
                return (subnet_selected);
            }
        }
    }

    // Failed to find a subnet.
    return (Subnet4Ptr());
}

Subnet4Ptr
CfgSubnets4::getSubnet(const SubnetID id) const {

    /// @todo: Once this code is migrated to multi-index container, use
    /// an index rather than full scan.
    for (auto subnet = subnets_.begin(); subnet != subnets_.end(); ++subnet) {
        if ((*subnet)->getID() == id) {
            return (*subnet);
        }
    }
    return (Subnet4Ptr());
}

Subnet4Ptr
CfgSubnets4::selectSubnet(const IOAddress& address,
                 const ClientClasses& client_classes) const {
    for (Subnet4Collection::const_iterator subnet = subnets_.begin();
         subnet != subnets_.end(); ++subnet) {

        // Address is in range for the subnet prefix, so return it.
        if (!(*subnet)->inRange(address)) {
            continue;
        }

        // If a subnet meets the client class criteria return it.
        if ((*subnet)->clientSupported(client_classes)) {
            LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE, DHCPSRV_CFGMGR_SUBNET4_ADDR)
                .arg((*subnet)->toText())
                .arg(address.toText());
            return (*subnet);
        }
    }

    // Failed to find a subnet.
    return (Subnet4Ptr());
}

void
CfgSubnets4::removeStatistics() {
    using namespace isc::stats;

    // For each v4 subnet currently configured, remove the statistic.
    StatsMgr& stats_mgr = StatsMgr::instance();
    for (Subnet4Collection::const_iterator subnet4 = subnets_.begin();
         subnet4 != subnets_.end(); ++subnet4) {
        SubnetID subnet_id = (*subnet4)->getID();
        stats_mgr.del(StatsMgr::generateName("subnet", subnet_id,
                                             "total-addresses"));

        stats_mgr.del(StatsMgr::generateName("subnet", subnet_id,
                                             "assigned-addresses"));

        stats_mgr.del(StatsMgr::generateName("subnet", subnet_id,
                                             "declined-addresses"));

        stats_mgr.del(StatsMgr::generateName("subnet", subnet_id,
                                             "declined-reclaimed-addresses"));

        stats_mgr.del(StatsMgr::generateName("subnet", subnet_id,
                                             "reclaimed-leases"));
    }
}

void
CfgSubnets4::updateStatistics() {
    using namespace isc::stats;

    StatsMgr& stats_mgr = StatsMgr::instance();
    for (Subnet4Collection::const_iterator subnet4 = subnets_.begin();
         subnet4 != subnets_.end(); ++subnet4) {
        SubnetID subnet_id = (*subnet4)->getID();

        stats_mgr.setValue(StatsMgr::
                           generateName("subnet", subnet_id, "total-addresses"),
                                        static_cast<int64_t>
                                        ((*subnet4)->getPoolCapacity(Lease::
                                                                     TYPE_V4)));
    }

    // Only recount the stats if we have subnets.
    if (subnets_.begin() != subnets_.end()) {
            LeaseMgrFactory::instance().recountLeaseStats4();
    }
}

ElementPtr
CfgSubnets4::toElement() const {
    ElementPtr result = Element::createList();
    // Iterate subnets
    for (Subnet4Collection::const_iterator subnet = subnets_.cbegin();
         subnet != subnets_.cend(); ++subnet) {
        result->add((*subnet)->toElement());
    }
    return (result);
}

} // end of namespace isc::dhcp
} // end of namespace isc