// Copyright (C) 2014-2022 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 <dhcpsrv/dhcpsrv_log.h>
#include <dhcpsrv/cfg_iface.h>
#include <dhcpsrv/timer_mgr.h>
#include <util/reconnect_ctl.h>
#include <util/multi_threading_mgr.h>
#include <util/strutil.h>
#include <algorithm>
#include <functional>

using namespace isc::asiolink;
using namespace isc::data;
using namespace isc::util;
namespace ph = std::placeholders;

namespace isc {
namespace dhcp {

const char* CfgIface::ALL_IFACES_KEYWORD = "*";

CfgIface::OpenSocketsFailedCallback CfgIface::open_sockets_failed_callback_ = 0;

CfgIface::CfgIface()
    : wildcard_used_(false), socket_type_(SOCKET_RAW), re_detect_(false),
      service_socket_require_all_(false), service_sockets_retry_wait_time_(5000),
      service_sockets_max_retries_(0),
      outbound_iface_(SAME_AS_INBOUND) {
}

void
CfgIface::closeSockets() const {
    IfaceMgr::instance().closeSockets();
}

bool
CfgIface::equals(const CfgIface& other) const {
    return (iface_set_ == other.iface_set_ &&
            address_map_ == other.address_map_ &&
            wildcard_used_ == other.wildcard_used_ &&
            socket_type_ == other.socket_type_);
}

bool
CfgIface::multipleAddressesPerInterfaceActive() {
    for (IfacePtr iface : IfaceMgr::instance().getIfaces()) {
        if (iface->countActive4() > 1) {
            return (true);
        }
    }
    return (false);
}

void
CfgIface::openSockets(const uint16_t family, const uint16_t port,
                      const bool use_bcast) {
    // Close any open sockets because we're going to modify some properties
    // of the IfaceMgr. Those modifications require that sockets are closed.
    closeSockets();
    // The loopback interface can be used only when:
    //  - UDP socket will be used, i.e. not IPv4 and RAW socket
    //  - the loopback interface is in the interface set or the address map.
    bool loopback_used_ = false;
    if ((family == AF_INET6) || (socket_type_ == SOCKET_UDP)) {
        // Check interface set
        for (IfaceSet::const_iterator iface_name = iface_set_.begin();
             iface_name != iface_set_.end(); ++iface_name) {
            IfacePtr iface = IfaceMgr::instance().getIface(*iface_name);
            if (iface && iface->flag_loopback_) {
                loopback_used_ = true;
            }
        }
        // Check address map
        for (ExplicitAddressMap::const_iterator unicast = address_map_.begin();
             unicast != address_map_.end(); ++unicast) {
            IfacePtr iface = IfaceMgr::instance().getIface(unicast->first);
            if (iface && iface->flag_loopback_) {
                loopback_used_ = true;
            }
        }
    }
    // If wildcard interface '*' was not specified, set all interfaces to
    // inactive state. We will later enable them selectively using the
    // interface names specified by the user. If wildcard interface was
    // specified, mark all interfaces active. Mark loopback inactive when
    // not explicitly allowed.
    setState(family, !wildcard_used_, !loopback_used_);
    IfaceMgr& iface_mgr = IfaceMgr::instance();
    // Remove selection of unicast addresses from all interfaces.
    iface_mgr.clearUnicasts();
    // Allow the loopback interface when required.
    iface_mgr.setAllowLoopBack(loopback_used_);
    // For the DHCPv4 server, if the user has selected that raw sockets
    // should be used, we will try to configure the Interface Manager to
    // support the direct responses to the clients that don't have the
    // IP address. This should effectively turn on the use of raw
    // sockets. However, this may be unsupported on some operating
    // systems, so there is no guarantee.
    if ((family == AF_INET) && (!IfaceMgr::instance().isTestMode())) {
        iface_mgr.setMatchingPacketFilter(socket_type_ == SOCKET_RAW);
        if ((socket_type_ == SOCKET_RAW) &&
            !iface_mgr.isDirectResponseSupported()) {
            LOG_WARN(dhcpsrv_logger, DHCPSRV_CFGMGR_SOCKET_RAW_UNSUPPORTED);
        }
    }
    // If there is no wildcard interface specified, we will have to iterate
    // over the names specified by the caller and enable them.
    if (!wildcard_used_) {
        for (IfaceSet::const_iterator iface_name = iface_set_.begin();
             iface_name != iface_set_.end(); ++iface_name) {
            IfacePtr iface = IfaceMgr::instance().getIface(*iface_name);
            // This shouldn't really happen because we are checking the
            // names of interfaces when they are being added (use()
            // function). But, if someone has triggered detection of
            // interfaces since then, some interfaces may have disappeared.
            if (iface == NULL) {
                isc_throw(Unexpected,
                          "fail to open socket on interface '"
                          << *iface_name << "' as this interface doesn't"
                          " exist");

            } else if (family == AF_INET) {
                iface->inactive4_ = false;
                setIfaceAddrsState(family, true, *iface);

            } else {
                iface->inactive6_ = false;
            }
        }
    }

    // Select unicast sockets for DHCPv6 or activate specific IPv4 addresses
    // for DHCPv4.
    for (ExplicitAddressMap::const_iterator unicast = address_map_.begin();
         unicast != address_map_.end(); ++unicast) {
        IfacePtr iface = IfaceMgr::instance().getIface(unicast->first);
        if (iface == NULL) {
            isc_throw(Unexpected,
                      "fail to open unicast socket on interface '"
                      << unicast->first << "' as this interface doesn't"
                      " exist");
        }
        if (family == AF_INET6) {
            iface->addUnicast(unicast->second);
            iface->inactive6_ = false;

        } else {
            iface->setActive(unicast->second, true);
            iface->inactive4_ = false;
        }
    }

    // Use broadcast only if we're using raw sockets. For the UDP sockets,
    // we only handle the relayed (unicast) traffic.
    const bool can_use_bcast = use_bcast && (socket_type_ == SOCKET_RAW);

    // Opening multiple raw sockets handling brodcast traffic on the single
    // interface may lead to processing the same message multiple times.
    // We don't prohibit such configuration because raw sockets can as well
    // handle the relayed traffic. We have to issue a warning, however, to
    // draw administrator's attention.
    if (family == AF_INET && can_use_bcast && multipleAddressesPerInterfaceActive()) {
        LOG_WARN(dhcpsrv_logger, DHCPSRV_MULTIPLE_RAW_SOCKETS_PER_IFACE);
    }

    reconnect_ctl_ = makeReconnectCtl();
    auto sopen = openSocketsWithRetry(reconnect_ctl_, family, port, can_use_bcast);

    if (!sopen) {
        // If no socket were opened, log a warning because the server will
        // not respond to any queries.
        LOG_WARN(dhcpsrv_logger, DHCPSRV_NO_SOCKETS_OPEN);
    }
}

std::pair<bool, bool>
CfgIface::openSocketsForFamily(const uint16_t family, const uint16_t port,
                               const bool can_use_bcast, const bool skip_opened) {
    bool no_errors = true;

    // Set the callbacks which are called when the socket fails to open
    // for some specific interface.
    auto error_callback = [&no_errors](const std::string& errmsg) {
        socketOpenErrorHandler(errmsg);
        no_errors = false;
    };

    IfaceMgr::instance().detectIfaces(true);

    bool sopen = false;
    if (family == AF_INET) {
        sopen = IfaceMgr::instance().openSockets4(port, can_use_bcast,
                                                  error_callback, skip_opened);
    } else {
        // use_bcast is ignored for V6.
        sopen = IfaceMgr::instance().openSockets6(port, error_callback,
                                                  skip_opened);
    }

    return (std::make_pair(sopen, no_errors));
}

ReconnectCtlPtr CfgIface::makeReconnectCtl() const {
    // Create unique timer name per instance.
    std::string timer_name = "SocketReopenTimer";

    auto on_fail_action = OnFailAction::SERVE_RETRY_CONTINUE;
    if (CfgIface::getServiceSocketsRequireAll()) {
        on_fail_action = OnFailAction::SERVE_RETRY_EXIT;
    }

    // Add one attempt for an initial call.
    auto reconnect_ctl = boost::make_shared<ReconnectCtl>("Socket", timer_name,
                                                          CfgIface::getServiceSocketsMaxRetries(),
                                                          CfgIface::getServiceSocketsRetryWaitTime(),
                                                          on_fail_action);

    return (reconnect_ctl);
}

bool
CfgIface::openSocketsWithRetry(ReconnectCtlPtr reconnect_ctl,
                               const uint16_t family, const uint16_t port,
                               const bool can_use_bcast) {
    MultiThreadingCriticalSection cs;

    // Skip opened sockets in the retry calls.
    bool is_initial_call = (reconnect_ctl->retriesLeft() == reconnect_ctl->maxRetries());
    auto result_pair = openSocketsForFamily(family, port, can_use_bcast, !is_initial_call);
    bool sopen = result_pair.first;
    bool has_errors = !result_pair.second;

    auto timer_name = reconnect_ctl->timerName();

    // On the initial call, unregister the previous, pending timer.
    if (is_initial_call && TimerMgr::instance()->isTimerRegistered(timer_name)) {
        TimerMgr::instance()->unregisterTimer(timer_name);
    }

    // Has errors and can retry
    if (has_errors && reconnect_ctl->retriesLeft() > 0) {
        // Initial call is excluded from retries counter.
        reconnect_ctl->checkRetries();
        // Start the timer.
        if (!TimerMgr::instance()->isTimerRegistered(timer_name)) {
            TimerMgr::instance()->registerTimer(timer_name,
                                                std::bind(&CfgIface::openSocketsWithRetry,
                                                          reconnect_ctl, family,
                                                          port, can_use_bcast),
                                                reconnect_ctl->retryInterval(),
                                                asiolink::IntervalTimer::ONE_SHOT);
        }
        TimerMgr::instance()->setup(timer_name);
    } else {
        // Cancel the timer.
        if (TimerMgr::instance()->isTimerRegistered(timer_name)) {
            TimerMgr::instance()->unregisterTimer(timer_name);
        }
        // Has errors but retries exceed
        if (has_errors) {
            if (open_sockets_failed_callback_) {
                open_sockets_failed_callback_(reconnect_ctl);
            }
        }
    }

    return (sopen);
}

void
CfgIface::reset() {
    wildcard_used_ = false;
    iface_set_.clear();
    address_map_.clear();
    useSocketType(AF_INET, SOCKET_RAW);
}

void
CfgIface::setState(const uint16_t family, const bool inactive,
                   const bool loopback_inactive) const {
    for (IfacePtr iface : IfaceMgr::instance().getIfaces()) {
        bool iface_inactive = iface->flag_loopback_ ? loopback_inactive : inactive;
        if (family == AF_INET) {
            iface->inactive4_ = iface_inactive;
        } else {
            iface->inactive6_ = iface_inactive;
        }

        // Activate/deactivate all addresses.
        setIfaceAddrsState(family, !inactive, *iface);
    }
}

void
CfgIface::setIfaceAddrsState(const uint16_t family, const bool active,
                             Iface& iface) const {
    // Activate/deactivate all addresses.
    for (Iface::Address addr : iface.getAddresses()) {
        if (addr.get().getFamily() == family) {
            iface.setActive(addr.get(), active);
        }
    }
}

void
CfgIface::socketOpenErrorHandler(const std::string& errmsg) {
    LOG_WARN(dhcpsrv_logger, DHCPSRV_OPEN_SOCKET_FAIL).arg(errmsg);
}

std::string
CfgIface::socketTypeToText() const {
    switch (socket_type_) {
    case SOCKET_RAW:
        return ("raw");

    case SOCKET_UDP:
        return ("udp");

    default:
        ;
    }

    isc_throw(Unexpected, "unsupported socket type " << socket_type_);
}

CfgIface::SocketType
CfgIface::textToSocketType(const std::string& socket_type_name) const {
    if (socket_type_name == "udp") {
        return (SOCKET_UDP);

    } else if (socket_type_name == "raw") {
        return (SOCKET_RAW);

    } else {
        isc_throw(InvalidSocketType, "unsupported socket type '"
                  << socket_type_name << "'");
    }
}

CfgIface::OutboundIface
CfgIface::getOutboundIface() const {
    return (outbound_iface_);
}

std::string
CfgIface::outboundTypeToText() const {
    switch (outbound_iface_) {
    case SAME_AS_INBOUND:
        return ("same-as-inbound");
    case USE_ROUTING:
        return ("use-routing");
    default:
        isc_throw(Unexpected, "unsupported outbound-type " << socket_type_);
    }

}

CfgIface::OutboundIface
CfgIface::textToOutboundIface(const std::string& txt) {
    if (txt == "same-as-inbound") {
        return (SAME_AS_INBOUND);

    } else if (txt == "use-routing") {
        return (USE_ROUTING);

    } else {
        isc_throw(BadValue, "unsupported outbound interface type '"
                  << txt << "'");
    }
}

void
CfgIface::setOutboundIface(const OutboundIface& outbound_iface) {
    outbound_iface_ = outbound_iface;
}

void
CfgIface::use(const uint16_t family, const std::string& iface_name) {
    // The interface name specified may have two formats:
    // - "interface-name", e.g. eth0
    // - "interface-name/address", e.g. eth0/10.0.0.1 or eth/2001:db8:1::1
    // The latter format is used to open unicast socket on the specified
    // interface. Here we are detecting which format was used and we strip
    // all extraneous spaces.
    size_t pos = iface_name.find("/");
    std::string name;
    std::string addr_str;
    // There is no unicast address so the whole string is an interface name.
    if (pos == std::string::npos) {
        name = util::str::trim(iface_name);
        if (name.empty()) {
            isc_throw(InvalidIfaceName,
                      "empty interface name used in configuration");

        } else if (name != ALL_IFACES_KEYWORD) {
            if (IfaceMgr::instance().getIface(name) == NULL) {
                isc_throw(NoSuchIface, "interface '" << name
                          << "' doesn't exist in the system");
            }

        } else if (wildcard_used_) {
            isc_throw(DuplicateIfaceName, "the wildcard interface '"
                      << ALL_IFACES_KEYWORD << "' can only be specified once");

        } else {
            LOG_DEBUG(dhcpsrv_logger, DHCPSRV_DBG_TRACE,
                      DHCPSRV_CFGMGR_ALL_IFACES_ACTIVE);
            wildcard_used_ = true;

        }

    } else {
        // The interface name includes the address on which the socket should
        // be opened, and we need to split interface name and the address to
        // two variables.
        name = util::str::trim(iface_name.substr(0, pos));
        addr_str = util::str::trim(iface_name.substr(pos + 1));

        // Interface name must not be empty.
        if (name.empty()) {
            isc_throw(InvalidIfaceName,
                      "empty interface name specified in the"
                      " interface configuration");

        }
        // An address following the interface name must not be empty.
        if (addr_str.empty()) {
            isc_throw(InvalidIfaceName,
                      "empty address specified in the interface"
                      << " configuration");

        }

        // Interface name must not be the wildcard name.
        if (name == ALL_IFACES_KEYWORD) {
            isc_throw(InvalidIfaceName,
                      "wildcard interface name '" << ALL_IFACES_KEYWORD
                      << "' must not be used in conjunction with an"
                      " address");

        }

        // Interface must exist.
        IfacePtr iface = IfaceMgr::instance().getIface(name);
        if (!iface) {
            isc_throw(NoSuchIface, "interface '" << name
                      << "' doesn't exist in the system");

        }

        // Convert address string. This may throw an exception if the address
        // is invalid.
        IOAddress addr(addr_str);

        // Validate V6 address.
        if (family == AF_INET6) {
            // Check that the address is a valid unicast address.
            if (!addr.isV6() || addr.isV6Multicast()) {
                isc_throw(InvalidIfaceName, "address '" << addr << "' is not"
                          " a valid IPv6 unicast address");
            }

            // There are valid cases where link local address can be specified to
            // receive unicast traffic, e.g. sent by relay agent.
            if (addr.isV6LinkLocal()) {
                LOG_WARN(dhcpsrv_logger, DHCPSRV_CFGMGR_UNICAST_LINK_LOCAL)
                    .arg(addr.toText()).arg(name);
            }

        } else {
            if (!addr.isV4()) {
                isc_throw(InvalidIfaceName, "address '" << addr << "' is not"
                          " a valid IPv4 address");
            }
        }

        // Interface must have this address assigned.
        if (!iface->hasAddress(addr)) {
            isc_throw(NoSuchAddress,
                      "interface '" << name << "' doesn't have address '"
                      << addr << "' assigned");
        }

        // For the IPv4, if the interface name was specified (instead of the interface-
        // address tuple) all addresses are already activated. Adding an explicit address
        // for the interface should result in error.
        if ((family == AF_INET) && (iface_set_.find(iface->getName()) != iface_set_.end())) {
            isc_throw(DuplicateIfaceName, "interface '" << iface->getName()
                      << "' has already been selected");
        }

        // Check if the address hasn't been selected already.
        std::pair<const std::string, IOAddress> iface_address_tuple(name, addr);
        if (std::find(address_map_.begin(), address_map_.end(),
                      iface_address_tuple) != address_map_.end()) {
            isc_throw(DuplicateAddress, "must not select address '"
                      << addr << "' for interface '" << name << "' "
                      "because this address is already selected");
        }

        if (family == AF_INET6) {
            LOG_INFO(dhcpsrv_logger, DHCPSRV_CFGMGR_USE_UNICAST)
                .arg(addr.toText()).arg(name);

        } else {
            LOG_INFO(dhcpsrv_logger, DHCPSRV_CFGMGR_USE_ADDRESS)
                .arg(addr.toText()).arg(name);
        }
        address_map_.insert(std::pair<std::string, IOAddress>(name, addr));
    }

    // If interface name was explicitly specified without an address, we will
    // insert the interface name to the set of enabled interfaces.
    if ((name != ALL_IFACES_KEYWORD) && addr_str.empty()) {
        // An interface has been selected or an IPv4 address on this interface
        // has been selected it is not allowed to select the whole interface.
        if ((iface_set_.find(name) != iface_set_.end()) ||
            ((family == AF_INET) && address_map_.count(name) > 0)) {
            isc_throw(DuplicateIfaceName, "interface '" << name
                      << "' has already been specified");
        }

        // Log that we're listening on the specific interface and that the
        // address is not explicitly specified.
        if (addr_str.empty()) {
            LOG_INFO(dhcpsrv_logger, DHCPSRV_CFGMGR_ADD_IFACE).arg(name);
        }
        iface_set_.insert(name);
    }
}

void
CfgIface::useSocketType(const uint16_t family,
                        const SocketType& socket_type) {
    if (family != AF_INET) {
        isc_throw(InvalidSocketType, "socket type must not be specified for"
                  " the DHCPv6 server");
    }
    socket_type_ = socket_type;
    LOG_INFO(dhcpsrv_logger, DHCPSRV_CFGMGR_SOCKET_TYPE_SELECT)
        .arg(socketTypeToText());
}

void
CfgIface::useSocketType(const uint16_t family,
                        const std::string& socket_type_name) {
    useSocketType(family, textToSocketType(socket_type_name));
}

ElementPtr
CfgIface::toElement() const {
    ElementPtr result = Element::createMap();

    // Set user context
    contextToElement(result);

    // Set interfaces
    ElementPtr ifaces = Element::createList();
    if (wildcard_used_) {
        ifaces->add(Element::create(std::string(ALL_IFACES_KEYWORD)));
    }
    for (IfaceSet::const_iterator iface = iface_set_.cbegin();
         iface != iface_set_.cend(); ++iface) {
        ifaces->add(Element::create(*iface));
    }
    for (ExplicitAddressMap::const_iterator address = address_map_.cbegin();
         address != address_map_.cend(); ++address) {
        std::string spec = address->first + "/" + address->second.toText();
        ifaces->add(Element::create(spec));
    }
    result->set("interfaces", ifaces);

    // Set dhcp-socket-type (no default because it is DHCPv4 specific)
    // @todo emit raw if and only if DHCPv4
    if (socket_type_ != SOCKET_RAW) {
        result->set("dhcp-socket-type", Element::create(std::string("udp")));
    }

    if (outbound_iface_ != SAME_AS_INBOUND) {
        result->set("outbound-interface", Element::create(outboundTypeToText()));
    }

    // Set re-detect
    result->set("re-detect", Element::create(re_detect_));

    // Set server socket binding
    if (service_socket_require_all_) {
        result->set("service-sockets-require-all", Element::create(service_socket_require_all_));
    }

    if (service_sockets_max_retries_ != 0) {
        result->set("service-sockets-max-retries", Element::create(static_cast<int>(service_sockets_max_retries_)));
        // If the max retries parameter is zero, the wait time is not used.
        result->set("service-sockets-retry-wait-time", Element::create(static_cast<int>(service_sockets_retry_wait_time_)));
    }

    return (result);
}

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