//
// Copyright 2017 Ettus Research, National Instruments Company
//
// SPDX-License-Identifier: GPL-3.0-or-later
//

#include "mpmd_xport_ctrl_udp.hpp"
#include "mpmd_impl.hpp"
#include "mpmd_xport_mgr.hpp"
#include <uhd/transport/udp_constants.hpp>
#include <uhd/transport/udp_simple.hpp>
#include <uhd/transport/udp_zero_copy.hpp>


using namespace uhd;
using namespace uhd::mpmd::xport;

namespace {

#if defined(UHD_PLATFORM_MACOS) || defined(UHD_PLATFORM_BSD)
//! Size of the host-side socket buffer for RX
const size_t MPMD_RX_SW_BUFF_SIZE_ETH = 0x100000; // 1Mib
#elif defined(UHD_PLATFORM_LINUX) || defined(UHD_PLATFORM_WIN32)
//! Size of the host-side socket buffer for RX
// For an ~8k frame size any size >32MiB is just wasted buffer space
const size_t MPMD_RX_SW_BUFF_SIZE_ETH = 0x2000000; // 32 MiB
#endif

//! Maximum CHDR packet size in bytes
const size_t MPMD_10GE_DATA_FRAME_MAX_SIZE = 4000;

//! Maximum CHDR packet size in bytes
const size_t MPMD_10GE_ASYNCMSG_FRAME_MAX_SIZE = 1472;

//! Number of send/recv frames
const size_t MPMD_ETH_NUM_FRAMES = 32;

//!
const double MPMD_BUFFER_FILL_RATE = 20.0e-3; // s
//! For MTU discovery, the time we wait for a packet before calling it
// oversized (seconds).
const double MPMD_MTU_DISCOVERY_TIMEOUT = 0.02;

// TODO: move these to appropriate header file for all other devices
const size_t MAX_RATE_1GIGE  = 1e9 / 8; // byte/s
const size_t MAX_RATE_10GIGE = 10e9 / 8; // byte/s

std::vector<std::string> get_addrs_from_mb_args(const uhd::device_addr_t& mb_args)
{
    // mb_args must always include addr
    if (not mb_args.has_key(FIRST_ADDR_KEY)) {
        throw uhd::runtime_error(
            "The " + FIRST_ADDR_KEY
            + " key must be specified in "
              "device args to create an Ethernet transport to an RFNoC block");
    }
    std::vector<std::string> addrs{mb_args[FIRST_ADDR_KEY]};
    if (mb_args.has_key(SECOND_ADDR_KEY)) {
        addrs.push_back(mb_args[SECOND_ADDR_KEY]);
    }
    return addrs;
}

/*! Do a binary search to discover MTU
 *
 * Uses the MPM echo service to figure out MTU. We simply send a bunch of
 * packets and see if they come back until we converged on the path MTU.
 * The end result must lie between \p min_frame_size and \p max_frame_size.
 *
 * \param address IP address
 * \param port UDP port (yeah it's a string!)
 * \param min_frame_size Minimum frame size, initialize algorithm to start
 *                       with this value
 * \param max_frame_size Maximum frame size, initialize algorithm to start
 *                       with this value
 * \param echo_timeout Timeout value in seconds. For frame sizes that
 *                     exceed the MTU, we don't expect a response, and this
 *                     is the amount of time we'll wait before we assume
 *                     the frame size exceeds the MTU.
 */
size_t discover_mtu(const std::string& address,
    const std::string& port,
    size_t min_frame_size,
    size_t max_frame_size,
    const double echo_timeout = 0.020)
{
    const size_t echo_prefix_offset = uhd::mpmd::mpmd_impl::MPM_ECHO_CMD.size();
    const size_t mtu_hdr_len        = echo_prefix_offset + 10;
    UHD_ASSERT_THROW(min_frame_size < max_frame_size);
    UHD_ASSERT_THROW(min_frame_size % 4 == 0);
    UHD_ASSERT_THROW(max_frame_size % 4 == 0);
    UHD_ASSERT_THROW(min_frame_size >= echo_prefix_offset + mtu_hdr_len);
    using namespace uhd::transport;
    // The return port will probably differ from the discovery port, so we
    // need a "broadcast" UDP connection; using make_connected() would
    // drop packets
    udp_simple::sptr udp = udp_simple::make_broadcast(address, port);
    std::string send_buf(uhd::mpmd::mpmd_impl::MPM_ECHO_CMD);
    send_buf.resize(max_frame_size, '#');
    UHD_ASSERT_THROW(send_buf.size() == max_frame_size);
    std::vector<uint8_t> recv_buf;
    recv_buf.resize(max_frame_size, ' ');

    // Little helper to check returned packets match the sent ones
    auto require_bufs_match = [&recv_buf, &send_buf, mtu_hdr_len](const size_t len) {
        if (len < mtu_hdr_len
            or std::memcmp((void*)&recv_buf[0], (void*)&send_buf[0], mtu_hdr_len) != 0) {
            throw uhd::runtime_error("Unexpected content of MTU "
                                     "discovery return packet!");
        }
    };
    UHD_LOG_TRACE("MPMD", "Determining UDP MTU... ");
    size_t seq_no = 0;
    while (min_frame_size < max_frame_size) {
        // Only test multiples of 4 bytes!
        const size_t test_frame_size = (max_frame_size / 2 + min_frame_size / 2 + 3)
                                       & ~size_t(3);
        // Encode sequence number and current size in the string, makes it
        // easy to debug in code or Wireshark. Is also used for identifying
        // response packets.
        std::sprintf(
            &send_buf[echo_prefix_offset], ";%04lu,%04lu", seq_no++, test_frame_size);
        UHD_LOG_TRACE("MPMD", "Testing frame size " << test_frame_size);
        udp->send(boost::asio::buffer(&send_buf[0], test_frame_size));

        const size_t len = udp->recv(boost::asio::buffer(recv_buf), echo_timeout);
        if (len == 0) {
            // Nothing received, so this is probably too big
            max_frame_size = test_frame_size - 4;
        } else if (len >= test_frame_size) {
            // Size went through, so bump the minimum
            require_bufs_match(len);
            min_frame_size = test_frame_size;
        } else if (len < test_frame_size) {
            // This is an odd case. Something must have snipped the packet
            // on the way back. Still, we'll just back off and try
            // something smaller.
            UHD_LOG_DEBUG("MPMD", "Unexpected packet truncation during MTU discovery.");
            require_bufs_match(len);
            max_frame_size = len;
        }
    }
    UHD_LOG_DEBUG("MPMD", "Path MTU for address " << address << ": " << min_frame_size);
    return min_frame_size;
}

} // namespace


mpmd_xport_ctrl_udp::mpmd_xport_ctrl_udp(const uhd::device_addr_t& mb_args)
    : _mb_args(mb_args)
    , _recv_args(filter_args(mb_args, "recv"))
    , _send_args(filter_args(mb_args, "send"))
    , _available_addrs(get_addrs_from_mb_args(mb_args))
    , _mtu(MPMD_10GE_DATA_FRAME_MAX_SIZE)
{
    const std::string mpm_discovery_port = _mb_args.get(
        mpmd_impl::MPM_DISCOVERY_PORT_KEY, std::to_string(mpmd_impl::MPM_DISCOVERY_PORT));
    auto discover_mtu_for_ip = [mpm_discovery_port](const std::string& ip_addr) {
        return discover_mtu(ip_addr,
            mpm_discovery_port,
            IP_PROTOCOL_MIN_MTU_SIZE - IP_PROTOCOL_UDP_PLUS_IP_HEADER,
            MPMD_10GE_DATA_FRAME_MAX_SIZE,
            MPMD_MTU_DISCOVERY_TIMEOUT);
    };

    for (const auto& ip_addr : _available_addrs) {
        _mtu = std::min(_mtu, discover_mtu_for_ip(ip_addr));
    }
}

uhd::both_xports_t mpmd_xport_ctrl_udp::make_transport(
    mpmd_xport_mgr::xport_info_t& xport_info,
    const usrp::device3_impl::xport_type_t xport_type,
    const uhd::device_addr_t& xport_args_)
{
    auto xport_args = xport_args_;

    if (xport_type == usrp::device3_impl::RX_DATA
        and not xport_args.has_key("recv_buff_size")) {
        xport_args["recv_buff_size"] = std::to_string(MPMD_RX_SW_BUFF_SIZE_ETH);
    }
    size_t link_speed = MAX_RATE_1GIGE;
    if (xport_info.count("link_speed") == 0) {
        UHD_LOG_WARNING("MPMD",
            "Could not determine link speed; using 1GibE max speed of "
                << MAX_RATE_1GIGE);
    } else {
        link_speed = xport_info.at("link_speed") == "10000" ? MAX_RATE_10GIGE
                                                            : MAX_RATE_1GIGE;
    }
    transport::zero_copy_xport_params default_buff_args;
    // Create actual UDP transport
    default_buff_args.recv_frame_size =
        xport_args.cast<size_t>("recv_frame_size", get_mtu(uhd::RX_DIRECTION));
    default_buff_args.recv_buff_size = link_speed * MPMD_BUFFER_FILL_RATE;
    default_buff_args.send_buff_size = link_speed * MPMD_BUFFER_FILL_RATE;
    if (xport_type == usrp::device3_impl::ASYNC_MSG) {
        default_buff_args.send_frame_size = MPMD_10GE_ASYNCMSG_FRAME_MAX_SIZE;
    } else {
        default_buff_args.send_frame_size =
            xport_args.cast<size_t>("send_frame_size", get_mtu(uhd::TX_DIRECTION));
    }
    transport::udp_zero_copy::buff_params buff_params;
    auto recv                     = transport::udp_zero_copy::make(xport_info["ipv4"],
        xport_info["port"],
        default_buff_args,
        buff_params,
        xport_args);
    const uint16_t port           = recv->get_local_port();
    const std::string src_ip_addr = recv->get_local_addr();
    xport_info["src_port"]        = std::to_string(port);
    xport_info["src_ipv4"]        = src_ip_addr;

    // Create both_xports_t object and finish:
    both_xports_t xports;
    xports.endianness     = uhd::ENDIANNESS_BIG;
    xports.send_sid       = sid_t(xport_info["send_sid"]);
    xports.recv_sid       = xports.send_sid.reversed();
    xports.recv_buff_size = buff_params.recv_buff_size;
    xports.send_buff_size = buff_params.send_buff_size;
    xports.recv           = recv; // Note: This is a type cast!
    xports.send           = recv; // This too
    return xports;
}

bool mpmd_xport_ctrl_udp::is_valid(const mpmd_xport_mgr::xport_info_t& xport_info) const
{
    return std::find(
               _available_addrs.cbegin(), _available_addrs.cend(), xport_info.at("ipv4"))
           != _available_addrs.cend();
}

size_t mpmd_xport_ctrl_udp::get_mtu(const uhd::direction_t /*dir*/) const
{
    return _mtu;
}