//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012- OpenVPN Inc.
//    Copyright (C) 2020-2022 Lev Stipakov <lev@openvpn.net>
//
//    SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//


// tun/transport client for ovpn-dco

#include <openvpn/dco/dcocli.hpp>
#include <openvpn/tun/client/tunconfigflags.hpp>

class OvpnDcoClient : public Client,
                      public KoRekey::Receiver,
                      public TransportClientParent,
                      public SessionStats::DCOTransportSource
{
    friend class ClientConfig;
    friend class GeNL;

    OPENVPN_EXCEPTION(dcocli_error);

    typedef RCPtr<OvpnDcoClient> Ptr;
    typedef GeNL<OvpnDcoClient *> GeNLImpl;

    struct PacketFrom
    {
        typedef std::unique_ptr<PacketFrom> SPtr;
        BufferAllocated buf;
    };

  public:
    static bool available(TunBuilderBase *tb)
    {
        if (tb)
            return tb->tun_builder_dco_available();
        else
            return GeNLImpl::available();
    }

    void tun_start(const OptionList &opt,
                   TransportClient &transcli,
                   CryptoDCSettings &dc_settings) override
    {
        // extract peer ID from pushed options
        try
        {
            const Option *o = opt.get_ptr("peer-id");
            if (o)
            {
                bool status = parse_number_validate<uint32_t>(
                    o->get(1, 16), 16, 0, OVPN_PEER_ID_UNDEF - 1, &peer_id);
                if (!status)
                    OPENVPN_THROW(dcocli_error, "Parse/range issue with pushed peer-id");
            }
            else
            {
                OPENVPN_THROW(dcocli_error, "No peer-id pushed by server");
            }
        }
        catch (const std::exception &e)
        {
            OPENVPN_THROW(dcocli_error, "Cannot extract peer-id: " << e.what());
        }

        tun_setup(opt);

        // Add a hook so ProtoContext will call back to
        // rekey() on rekey ops.
        dc_settings.set_factory(CryptoDCFactory::Ptr(new KoRekey::Factory(
            dc_settings.factory(), this, config->transport.frame)));

        // add peer in ovpn-dco
        add_peer(peer_id,
                 state->vpn_ip4_gw.to_ipv4_zero(),
                 state->vpn_ip6_gw.to_ipv6_zero());
        // signal that we are connected
        tun_parent->tun_connected();
    }

    std::string tun_name() const override
    {
        return "ovpn-dco";
    }

    IP::Addr server_endpoint_addr() const override
    {
        if (transport)
            return transport->server_endpoint_addr();
        else
            return IP::Addr();
    }

    unsigned short server_endpoint_port() const override
    {
        if (transport)
            return transport->server_endpoint_port();
        else
            return 0;
    }

    Protocol transport_protocol() const override
    {
        return transport->transport_protocol();
    }

    void transport_start() override
    {
        TransportClientFactory::Ptr transport_factory;

        if (!config->transport.protocol.is_tcp())
        {
            UDPTransport::ClientConfig::Ptr udpconf = UDPTransport::ClientConfig::new_obj();
            udpconf->remote_list = config->transport.remote_list;
            udpconf->frame = config->transport.frame;
            udpconf->stats = config->transport.stats;
            udpconf->socket_protect = config->transport.socket_protect;
            udpconf->server_addr_float = config->transport.server_addr_float;
            transport_factory = udpconf;
        }
        else
        {
            TCPTransport::ClientConfig::Ptr tcpconf = TCPTransport::ClientConfig::new_obj();
            tcpconf->remote_list = config->transport.remote_list;
            tcpconf->frame = config->transport.frame;
            tcpconf->stats = config->transport.stats;
            tcpconf->socket_protect = config->transport.socket_protect;
            transport_factory = tcpconf;
        }

        config->transport.stats->dco_configure(this);

        transport = transport_factory->new_transport_client_obj(io_context, this);
        transport->transport_start();
    }

    bool transport_send_const(const Buffer &buf) override
    {
        return transport->transport_send_const(buf);
    }

    bool transport_send(BufferAllocated &buf) override
    {
        OPENVPN_THROW(dcocli_error,
                      "Non-const send expected for data channel only, but "
                      "ovpndcocli is not expected to handle data packets");
    }

    void get_remote_sockaddr(struct sockaddr_storage &sa, socklen_t &salen)
    {
        memset(&sa, 0, sizeof(sa));

        struct sockaddr_in *sa4 = (struct sockaddr_in *)&sa;
        struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *)&sa;

        IP::Addr remote_addr = transport->server_endpoint_addr();
        if (remote_addr.version() == IP::Addr::V4)
        {
            salen = sizeof(*sa4);
            *sa4 = remote_addr.to_ipv4().to_sockaddr(transport->server_endpoint_port());
        }
        else
        {
            salen = sizeof(*sa6);
            *sa6 = remote_addr.to_ipv6().to_sockaddr(transport->server_endpoint_port());
        }
    }

    void del_peer(uint32_t peer_id)
    {
        TunBuilderBase *tb = config->builder;
        if (tb)
        {
            tb->tun_builder_dco_del_peer(peer_id);
            return;
        }

        genl->del_peer(peer_id);
    }

    void add_peer(uint32_t peer_id, IPv4::Addr ipv4, IPv6::Addr ipv6)
    {
        struct sockaddr_storage sa;
        socklen_t salen;

        get_remote_sockaddr(sa, salen);

        TunBuilderBase *tb = config->builder;
        if (tb)
        {
            tb->tun_builder_dco_new_peer(peer_id,
                                         transport->native_handle(),
                                         (struct sockaddr *)&sa,
                                         salen,
                                         ipv4,
                                         ipv6);
            return;
        }

        genl->new_peer(peer_id,
                       transport->native_handle(),
                       (struct sockaddr *)&sa,
                       salen,
                       ipv4,
                       ipv6);
    }

    void update_peer_stats(uint32_t peer_id, bool sync)
    {
        const SessionStats::DCOTransportSource::Data old_stats = last_stats;

        if (peer_id == OVPN_PEER_ID_UNDEF)
            return;

        TunBuilderBase *tb = config->builder;
        if (tb)
        {
            tb->tun_builder_dco_get_peer(peer_id, sync);
        }
        else
        {
            genl->get_peer(peer_id, sync);
        }

        last_delta = last_stats - old_stats;
    }

    void resolve_callback(const openvpn_io::error_code &error,
                          results_type results) override
    {
    }

    void stop_() override
    {
        if (!halt)
        {
            /* update stats before deleting peer in kernelspace */
            update_peer_stats(peer_id, true);

            halt = true;

            if (config->builder)
            {
                config->builder->tun_builder_teardown(true);
                if (pipe)
                    pipe->close();
            }
            else
            {
                std::ostringstream os;
                if (genl)
                    genl->stop();

                int res = TunNetlink::iface_del(os, config->dev_name);
                if (res != 0)
                {
                    OPENVPN_LOG("ovpndcocli: error deleting iface ovpn:" << os.str());
                }
            }

            if (transport)
                transport->stop();
        }
    }

    void apply_push_update(const OptionList &opt, TransportClient & /* transcli */) override
    {
        tun_setup(opt);
        tun_parent->tun_connected();
    }

    void rekey(const CryptoDCInstance::RekeyType rktype,
               const KoRekey::Info &rkinfo) override
    {
        if (halt)
            return;

        if (config->builder)
            rekey_impl_tb(rktype, rkinfo);
        else
            rekey_impl(rktype, rkinfo);
    }

    void rekey_impl(const CryptoDCInstance::RekeyType rktype,
                    const KoRekey::Info &rkinfo)
    {
        KoRekey::OvpnDcoKey key(rktype, rkinfo);
        auto kc = key();

        switch (rktype)
        {
        case CryptoDCInstance::ACTIVATE_PRIMARY:
            genl->new_key(OVPN_KEY_SLOT_PRIMARY, kc);

            handle_keepalive();
            break;

        case CryptoDCInstance::NEW_SECONDARY:

            genl->new_key(OVPN_KEY_SLOT_SECONDARY, kc);
            break;

        case CryptoDCInstance::PRIMARY_SECONDARY_SWAP:

            genl->swap_keys(peer_id);
            break;

        case CryptoDCInstance::DEACTIVATE_SECONDARY:

            genl->del_key(peer_id, OVPN_KEY_SLOT_SECONDARY);
            break;

        case CryptoDCInstance::DEACTIVATE_ALL:
            // TODO: deactivate all keys
            OPENVPN_LOG("ovpndcocli: deactivate all keys");
            break;

        default:
            OPENVPN_LOG("ovpndcocli: unknown rekey type: " << rktype);
            break;
        }
    }

    void rekey_impl_tb(const CryptoDCInstance::RekeyType rktype,
                       const KoRekey::Info &rkinfo)
    {
        KoRekey::OvpnDcoKey key(rktype, rkinfo);
        auto kc = key();

        TunBuilderBase *tb = config->builder;

        switch (rktype)
        {
        case CryptoDCInstance::ACTIVATE_PRIMARY:
            tb->tun_builder_dco_new_key(OVPN_KEY_SLOT_PRIMARY, kc);

            handle_keepalive();
            break;

        case CryptoDCInstance::NEW_SECONDARY:
            tb->tun_builder_dco_new_key(OVPN_KEY_SLOT_SECONDARY, kc);
            break;

        case CryptoDCInstance::PRIMARY_SECONDARY_SWAP:
            tb->tun_builder_dco_swap_keys(peer_id);
            break;

        case CryptoDCInstance::DEACTIVATE_SECONDARY:
            tb->tun_builder_dco_del_key(peer_id, OVPN_KEY_SLOT_SECONDARY);
            break;

        case CryptoDCInstance::DEACTIVATE_ALL:
            // TODO: deactivate all keys
            OPENVPN_LOG("ovpndcocli: deactivate all keys");
            break;

        default:
            OPENVPN_LOG("ovpndcocli: unknown rekey type: " << rktype);
            break;
        }
    }

    void transport_recv(BufferAllocated &buf) override
    {
        transport_parent->transport_recv(buf);
    }

    bool tun_read_handler(BufferAllocated &buf)
    {
        if (halt)
            return false;

        int8_t cmd = -1;
        buf.read(&cmd, sizeof(cmd));

        switch (cmd)
        {
        case OVPN_CMD_DEL_PEER:
            {
                uint32_t peer_id;
                buf.read(&peer_id, sizeof(peer_id));
                uint8_t reason;
                buf.read(&reason, sizeof(reason));

                std::ostringstream os;
                Error::Type err;

                if (peer_id != this->peer_id)
                {
                    OPENVPN_LOG("received DEL_PEER for " << peer_id << " while expecting " << this->peer_id);
                    break;
                }

                switch (reason)
                {
                case OVPN_DEL_PEER_REASON_EXPIRED:
                    err = Error::TRANSPORT_ERROR;
                    os << "keepalive timeout";
                    break;

                case OVPN_DEL_PEER_REASON_TRANSPORT_ERROR:
                    err = Error::TRANSPORT_ERROR;
                    os << "transport error";
                    break;

                case OVPN_DEL_PEER_REASON_TEARDOWN:
                    err = Error::TRANSPORT_ERROR;
                    os << "peer deleted, id=" << peer_id << ", teardown";
                    break;

                case OVPN_DEL_PEER_REASON_USERSPACE:
                    OPENVPN_LOG("peer deleted, id=" << peer_id
                                                    << ", requested by userspace");
                    return true;

                default:
                    err = Error::TUN_HALT;
                    os << "peer deleted, id=" << peer_id << ", reason=" << reason;
                    break;
                }

                // peer is gone - avoid any other netlink call for it
                this->peer_id = OVPN_PEER_ID_UNDEF;

                stop_();
                transport_parent->transport_error(err, os.str());
                break;
            }

        case OVPN_CMD_GET_PEER:
            {
                struct OvpnDcoPeer peer;
                buf.read(&peer, sizeof(peer));

                last_stats = SessionStats::DCOTransportSource::Data(peer.transport.rx_bytes,
                                                                    peer.transport.tx_bytes,
                                                                    peer.vpn.rx_bytes,
                                                                    peer.vpn.tx_bytes,
                                                                    peer.transport.rx_pkts,
                                                                    peer.transport.tx_pkts,
                                                                    peer.vpn.rx_pkts,
                                                                    peer.vpn.tx_pkts);

                break;
            }

        case -1:
            // consider all errors as fatal
            stop_();
            transport_parent->transport_error(Error::TUN_HALT, buf_to_string(buf));
            return false;
            break;

        default:
            OPENVPN_LOG("Unknown ovpn-dco cmd " << cmd);
            break;
        }

        return true;
    }

    void transport_needs_send() override
    {
        transport_parent->transport_needs_send();
    }

    void transport_error(const Error::Type fatal_err,
                         const std::string &err_text) override
    {
        transport_parent->transport_error(fatal_err, err_text);
    }

    void proxy_error(const Error::Type fatal_err,
                     const std::string &err_text) override
    {
        transport_parent->proxy_error(fatal_err, err_text);
    }

    bool transport_is_openvpn_protocol() override
    {
        return transport_parent->transport_is_openvpn_protocol();
    }

    void transport_pre_resolve() override
    {
        transport_parent->transport_pre_resolve();
    }

    void transport_wait_proxy() override
    {
        transport_parent->transport_wait_proxy();
    }

    void transport_wait() override
    {
        transport_parent->transport_wait();
    }

    void transport_connecting() override
    {
        transport_parent->transport_connecting();
    }

    bool is_keepalive_enabled() const override
    {
        return transport_parent->is_keepalive_enabled();
    }

    void disable_keepalive(unsigned int &keepalive_ping,
                           unsigned int &keepalive_timeout) override
    {
        transport_parent->disable_keepalive(keepalive_ping, keepalive_timeout);
    }

  private:
    OvpnDcoClient(openvpn_io::io_context &io_context_arg,
                  ClientConfig *config_arg,
                  TransportClientParent *parent_arg)
        : Client(io_context_arg, config_arg, parent_arg)
    {
        TunBuilderBase *tb = config->builder;
        if (tb)
        {
            tb->tun_builder_new();
            // pipe fd which is used to communicate to kernel
            int fd = tb->tun_builder_dco_enable(config->dev_name);
            if (fd == -1)
            {
                stop_();
                transport_parent->transport_error(Error::TUN_IFACE_CREATE,
                                                  "error creating ovpn-dco device");
                return;
            }

            pipe.reset(new openvpn_io::posix::stream_descriptor(io_context, fd));
            queue_read_pipe(nullptr);
            return;
        }

        int res = -ENOENT;
        const int max_units = 256;
        // attempt creating the device using the provided name, in case
        // of error append a counter starting at 1 and try again until 256.
        for (int unit = 0; unit < max_units; ++unit)
        {
            std::string n = config->dev_name;
            if (unit)
                n += openvpn::to_string(unit);
            if (n.length() >= IFNAMSIZ)
            {
                stop_();
                transport_parent->transport_error(Error::TUN_IFACE_CREATE,
                                                  "DCO: ifname name too long: " + n);
                return;
            }


            OPENVPN_LOG("DCO: attempting to open iface " + n);

            std::ostringstream os;
            res = TunNetlink::iface_new(os, n, "ovpn-dco");
            if (res)
            {
                OPENVPN_LOG("DCO: couldn't open iface " + n + ": " << os.str());
                continue;
            }

            // iface creation was successful
            config->dev_name = n;
            break;
        }

        // no successful creation. bail out
        if (res)
        {
            stop_();
            transport_parent->transport_error(Error::TUN_IFACE_CREATE,
                                              "DCO: failed to open iface " + config->dev_name
                                                  + " after trying " + openvpn::to_string(max_units)
                                                  + " units");
            return;
        }

        genl.reset(new GeNLImpl(
            io_context_arg, if_nametoindex(config_arg->dev_name.c_str()), this));
    }

    void tun_setup(const OptionList &opt)
    {
        // notify parent
        tun_parent->tun_pre_tun_config();

        // parse pushed options
        TunBuilderCapture::Ptr po;
        TunBuilderBase *builder;

        if (config->builder)
        {
            builder = config->builder;

            // Reset any addresses/routes captured during a previous tun
            // setup so that a reconfiguration -- e.g. triggered by a
            // PUSH_UPDATE -- starts from a clean snapshot instead of
            // accumulating duplicate entries (which break the re-establish
            // and leave the interface unconfigured). For an active DCO
            // session the builder keeps the ovpn-dco device, peer and keys
            // intact across this reset.
            builder->tun_builder_new();
        }
        else
        {
            po.reset(new TunBuilderCapture());
            builder = po.get();
        }

        TunProp::configure_builder(builder,
                                   state.get(),
                                   config->transport.stats.get(),
                                   server_endpoint_addr(),
                                   config->tun.tun_prop,
                                   opt,
                                   nullptr,
                                   false);

        if (po)
            OPENVPN_LOG("CAPTURED OPTIONS:" << std::endl
                                            << po->to_string());

        if (config->builder)
        {
            config->builder->tun_builder_dco_establish();
        }
        else
        {
            if (remove_cmds)
                remove_cmds->execute_log();

            ActionList::Ptr add_cmds = new ActionList();
            remove_cmds.reset(new ActionListReversed());

            std::vector<IP::Route> rtvec;

            TUN_LINUX::tun_config(config->dev_name,
                                  *po,
                                  &rtvec,
                                  *add_cmds,
                                  *remove_cmds,
                                  TunConfigFlags::ADD_BYPASS_ROUTES);

            // execute commands to bring up interface
            add_cmds->execute_log();
        }
    }

    void handle_keepalive()
    {
        // since userspace doesn't know anything about presense or
        // absense of data channel traffic, ping should be handled in kernel
        if (transport_parent->is_keepalive_enabled())
        {
            unsigned int keepalive_interval = 0;
            unsigned int keepalive_timeout = 0;

            // In addition to disabling userspace keepalive,
            // this call also assigns keepalive values to provided arguments
            // default keepalive values could be overwritten by config values,
            // which in turn could be overwritten by pushed options
            transport_parent->disable_keepalive(keepalive_interval,
                                                keepalive_timeout);

            // Allow overide of keepalive timeout
            if (config->ping_restart_override)
                keepalive_timeout = config->ping_restart_override;

            if (config->builder)
            {
                config->builder->tun_builder_dco_set_peer(peer_id, keepalive_interval, keepalive_timeout);
            }
            else
            {
                // enable keepalive in kernel
                genl->set_peer(peer_id, keepalive_interval, keepalive_timeout);
            }
        }
    }

    void queue_read_pipe(PacketFrom *pkt)
    {
        if (!pkt)
        {
            pkt = new PacketFrom();
        }
        // good enough values for control channel packets
        pkt->buf.reset(512,
                       3072,
                       BufAllocFlags::GROW | BufAllocFlags::CONSTRUCT_ZERO | BufAllocFlags::DESTRUCT_ZERO);
        pipe->async_read_some(
            pkt->buf.mutable_buffer(),
            [self = Ptr(this),
             pkt = PacketFrom::SPtr(pkt)](const openvpn_io::error_code &error,
                                          const size_t bytes_recvd) mutable
            {
                if (!error)
                {
                    pkt->buf.set_size(bytes_recvd);
                    if (self->tun_read_handler(pkt->buf))
                        self->queue_read_pipe(pkt.release());
                }
                else
                {
                    if (!self->halt)
                    {
                        OPENVPN_LOG("ovpn-dco pipe read error: " << error.message());
                        self->stop_();
                        self->transport_parent->transport_error(Error::TUN_HALT,
                                                                error.message());
                    }
                }
            });
    }

    SessionStats::DCOTransportSource::Data dco_transport_stats_delta() override
    {
        if (halt)
        {
            /* retrieve the last stats update and erase it to avoid race conditions with other queries */
            SessionStats::DCOTransportSource::Data delta = last_delta;
            last_delta = SessionStats::DCOTransportSource::Data(0, 0);
            return delta;
        }

        update_peer_stats(peer_id, true);
        return last_delta;
    }

    // used to communicate to kernel via privileged process
    std::unique_ptr<openvpn_io::posix::stream_descriptor> pipe;

    GeNLImpl::Ptr genl;
    TransportClient::Ptr transport;
    SessionStats::DCOTransportSource::Data last_stats;
    SessionStats::DCOTransportSource::Data last_delta;
};
