dolphin/Source/Core/Core/NetPlayClient.cpp

// Copyright 2010 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

#include "Core/NetPlayClient.h"
#include <algorithm>
#include <fstream>
#include <mbedtls/md5.h>
#include <memory>
#include <thread>
#include "Common/Common.h"
#include "Common/CommonPaths.h"
#include "Common/CommonTypes.h"
#include "Common/ENetUtil.h"
#include "Common/MD5.h"
#include "Common/MsgHandler.h"
#include "Common/StringUtil.h"
#include "Common/Timer.h"
#include "Core/ConfigManager.h"
#include "Core/HW/EXI/EXI_DeviceIPL.h"
#include "Core/HW/SI/SI.h"
#include "Core/HW/SI/SI_DeviceGCController.h"
#include "Core/HW/Sram.h"
#include "Core/HW/WiimoteEmu/WiimoteEmu.h"
#include "Core/HW/WiimoteReal/WiimoteReal.h"
#include "Core/IOS/USB/Bluetooth/BTEmu.h"
#include "Core/Movie.h"
#include "InputCommon/GCAdapter.h"
#include "VideoCommon/OnScreenDisplay.h"
#include "VideoCommon/VideoConfig.h"

static std::mutex crit_netplay_client;
static NetPlayClient* netplay_client = nullptr;
NetSettings g_NetPlaySettings;

// called from ---GUI--- thread
NetPlayClient::~NetPlayClient()
{
  // not perfect
  if (m_is_running.IsSet())
    StopGame();

  if (m_is_connected)
  {
    m_do_loop.Clear();
    m_thread.join();
  }

  if (m_server)
  {
    Disconnect();
  }

  if (g_MainNetHost.get() == m_client)
  {
    g_MainNetHost.release();
  }
  if (m_client)
  {
    enet_host_destroy(m_client);
    m_client = nullptr;
  }

  if (m_traversal_client)
  {
    ReleaseTraversalClient();
  }
}

// called from ---GUI--- thread
NetPlayClient::NetPlayClient(const std::string& address, const u16 port, NetPlayUI* dialog,
                             const std::string& name, bool traversal,
                             const std::string& centralServer, u16 centralPort)
    : m_dialog(dialog), m_player_name(name)
{
  ClearBuffers();

  if (!traversal)
  {
    // Direct Connection
    m_client = enet_host_create(nullptr, 1, 3, 0, 0);

    if (m_client == nullptr)
    {
      PanicAlertT("Couldn't Create Client");
    }

    ENetAddress addr;
    enet_address_set_host(&addr, address.c_str());
    addr.port = port;

    m_server = enet_host_connect(m_client, &addr, 3, 0);

    if (m_server == nullptr)
    {
      PanicAlertT("Couldn't create peer.");
    }

    ENetEvent netEvent;
    int net = enet_host_service(m_client, &netEvent, 5000);
    if (net > 0 && netEvent.type == ENET_EVENT_TYPE_CONNECT)
    {
      if (Connect())
      {
        m_client->intercept = ENetUtil::InterceptCallback;
        m_thread = std::thread(&NetPlayClient::ThreadFunc, this);
      }
    }
    else
    {
      PanicAlertT("Failed to Connect!");
    }
  }
  else
  {
    if (address.size() > NETPLAY_CODE_SIZE)
    {
      PanicAlertT("Host code size is to large.\nPlease recheck that you have the correct code");
      return;
    }

    if (!EnsureTraversalClient(centralServer, centralPort))
      return;
    m_client = g_MainNetHost.get();

    m_traversal_client = g_TraversalClient.get();

    // If we were disconnected in the background, reconnect.
    if (m_traversal_client->m_State == TraversalClient::Failure)
      m_traversal_client->ReconnectToServer();
    m_traversal_client->m_Client = this;
    m_host_spec = address;
    m_connection_state = ConnectionState::WaitingForTraversalClientConnection;
    OnTraversalStateChanged();
    m_connecting = true;

    Common::Timer connect_timer;
    connect_timer.Start();

    while (m_connecting)
    {
      ENetEvent netEvent;
      if (m_traversal_client)
        m_traversal_client->HandleResends();

      while (enet_host_service(m_client, &netEvent, 4) > 0)
      {
        sf::Packet rpac;
        switch (netEvent.type)
        {
        case ENET_EVENT_TYPE_CONNECT:
          m_server = netEvent.peer;
          if (Connect())
          {
            m_connection_state = ConnectionState::Connected;
            m_thread = std::thread(&NetPlayClient::ThreadFunc, this);
          }
          return;
        default:
          break;
        }
      }
      if (connect_timer.GetTimeElapsed() > 5000)
        break;
    }
    PanicAlertT("Failed To Connect!");
  }
}

bool NetPlayClient::Connect()
{
  // send connect message
  sf::Packet packet;
  packet << scm_rev_git_str;
  packet << netplay_dolphin_ver;
  packet << m_player_name;
  Send(packet);
  enet_host_flush(m_client);
  sf::Packet rpac;
  // TODO: make this not hang
  ENetEvent netEvent;
  if (enet_host_service(m_client, &netEvent, 5000) > 0 && netEvent.type == ENET_EVENT_TYPE_RECEIVE)
  {
    rpac.append(netEvent.packet->data, netEvent.packet->dataLength);
    enet_packet_destroy(netEvent.packet);
  }
  else
  {
    return false;
  }

  MessageId error;
  rpac >> error;

  // got error message
  if (error)
  {
    switch (error)
    {
    case CON_ERR_SERVER_FULL:
      PanicAlertT("The server is full!");
      break;
    case CON_ERR_VERSION_MISMATCH:
      PanicAlertT("The server and client's NetPlay versions are incompatible!");
      break;
    case CON_ERR_GAME_RUNNING:
      PanicAlertT("The server responded: the game is currently running!");
      break;
    default:
      PanicAlertT("The server sent an unknown error message!");
      break;
    }

    Disconnect();
    return false;
  }
  else
  {
    rpac >> m_pid;

    Player player;
    player.name = m_player_name;
    player.pid = m_pid;
    player.revision = netplay_dolphin_ver;

    // add self to player list
    m_players[m_pid] = player;
    m_local_player = &m_players[m_pid];

    m_dialog->Update();

    m_is_connected = true;

    return true;
  }
}

// called from ---NETPLAY--- thread
unsigned int NetPlayClient::OnData(sf::Packet& packet)
{
  MessageId mid;
  packet >> mid;

  switch (mid)
  {
  case NP_MSG_PLAYER_JOIN:
  {
    Player player;
    packet >> player.pid;
    packet >> player.name;
    packet >> player.revision;

    {
      std::lock_guard<std::recursive_mutex> lkp(m_crit.players);
      m_players[player.pid] = player;
    }

    m_dialog->Update();
  }
  break;

  case NP_MSG_PLAYER_LEAVE:
  {
    PlayerId pid;
    packet >> pid;

    {
      std::lock_guard<std::recursive_mutex> lkp(m_crit.players);
      m_players.erase(m_players.find(pid));
    }

    m_dialog->Update();
  }
  break;

  case NP_MSG_CHAT_MESSAGE:
  {
    PlayerId pid;
    packet >> pid;
    std::string msg;
    packet >> msg;

    // don't need lock to read in this thread
    const Player& player = m_players[pid];

    // add to gui
    std::ostringstream ss;
    ss << player.name << '[' << (char)(pid + '0') << "]: " << msg;

    m_dialog->AppendChat(ss.str());
  }
  break;

  case NP_MSG_PAD_MAPPING:
  {
    for (PadMapping& mapping : m_pad_map)
    {
      packet >> mapping;
    }

    UpdateDevices();

    m_dialog->Update();
  }
  break;

  case NP_MSG_WIIMOTE_MAPPING:
  {
    for (PadMapping& mapping : m_wiimote_map)
    {
      packet >> mapping;
    }

    m_dialog->Update();
  }
  break;

  case NP_MSG_PAD_DATA:
  {
    PadMapping map = 0;
    GCPadStatus pad;
    packet >> map >> pad.button >> pad.analogA >> pad.analogB >> pad.stickX >> pad.stickY >>
        pad.substickX >> pad.substickY >> pad.triggerLeft >> pad.triggerRight;

    // Trusting server for good map value (>=0 && <4)
    // add to pad buffer
    m_pad_buffer.at(map).Push(pad);
    m_gc_pad_event.Set();
  }
  break;

  case NP_MSG_WIIMOTE_DATA:
  {
    PadMapping map = 0;
    NetWiimote nw;
    u8 size;
    packet >> map >> size;

    nw.resize(size);

    for (unsigned int i = 0; i < size; ++i)
      packet >> nw[i];

    // Trusting server for good map value (>=0 && <4)
    // add to Wiimote buffer
    m_wiimote_buffer.at(map).Push(nw);
    m_wii_pad_event.Set();
  }
  break;

  case NP_MSG_PAD_BUFFER:
  {
    u32 size = 0;
    packet >> size;

    m_target_buffer_size = size;
    m_dialog->OnPadBufferChanged(size);
  }
  break;

  case NP_MSG_CHANGE_GAME:
  {
    {
      std::lock_guard<std::recursive_mutex> lkg(m_crit.game);
      packet >> m_selected_game;
    }

    // update gui
    m_dialog->OnMsgChangeGame(m_selected_game);

    sf::Packet game_status_packet;
    game_status_packet << static_cast<MessageId>(NP_MSG_GAME_STATUS);

    PlayerGameStatus status = m_dialog->FindGame(m_selected_game).empty() ?
                                  PlayerGameStatus::NotFound :
                                  PlayerGameStatus::Ok;

    game_status_packet << static_cast<u32>(status);
    Send(game_status_packet);
  }
  break;

  case NP_MSG_GAME_STATUS:
  {
    PlayerId pid;
    packet >> pid;

    {
      std::lock_guard<std::recursive_mutex> lkp(m_crit.players);
      Player& player = m_players[pid];
      u32 status;
      packet >> status;
      player.game_status = static_cast<PlayerGameStatus>(status);
    }

    m_dialog->Update();
  }
  break;

  case NP_MSG_START_GAME:
  {
    {
      std::lock_guard<std::recursive_mutex> lkg(m_crit.game);
      packet >> m_current_game;
      packet >> g_NetPlaySettings.m_CPUthread;
      packet >> g_NetPlaySettings.m_CPUcore;
      packet >> g_NetPlaySettings.m_EnableCheats;
      packet >> g_NetPlaySettings.m_SelectedLanguage;
      packet >> g_NetPlaySettings.m_OverrideGCLanguage;
      packet >> g_NetPlaySettings.m_ProgressiveScan;
      packet >> g_NetPlaySettings.m_PAL60;
      packet >> g_NetPlaySettings.m_DSPEnableJIT;
      packet >> g_NetPlaySettings.m_DSPHLE;
      packet >> g_NetPlaySettings.m_WriteToMemcard;
      packet >> g_NetPlaySettings.m_CopyWiiSave;
      packet >> g_NetPlaySettings.m_OCEnable;
      packet >> g_NetPlaySettings.m_OCFactor;

      int tmp;
      packet >> tmp;
      g_NetPlaySettings.m_EXIDevice[0] = static_cast<ExpansionInterface::TEXIDevices>(tmp);
      packet >> tmp;
      g_NetPlaySettings.m_EXIDevice[1] = static_cast<ExpansionInterface::TEXIDevices>(tmp);

      u32 time_low, time_high;
      packet >> time_low;
      packet >> time_high;
      g_netplay_initial_rtc = time_low | ((u64)time_high << 32);
    }

    m_dialog->OnMsgStartGame();
  }
  break;

  case NP_MSG_STOP_GAME:
  case NP_MSG_DISABLE_GAME:
  {
    StopGame();
    m_dialog->OnMsgStopGame();
  }
  break;

  case NP_MSG_PING:
  {
    u32 ping_key = 0;
    packet >> ping_key;

    sf::Packet response_packet;
    response_packet << static_cast<MessageId>(NP_MSG_PONG);
    response_packet << ping_key;

    Send(response_packet);
  }
  break;

  case NP_MSG_PLAYER_PING_DATA:
  {
    PlayerId pid;
    packet >> pid;

    {
      std::lock_guard<std::recursive_mutex> lkp(m_crit.players);
      Player& player = m_players[pid];
      packet >> player.ping;
    }

    DisplayPlayersPing();
    m_dialog->Update();
  }
  break;

  case NP_MSG_DESYNC_DETECTED:
  {
    int pid_to_blame;
    u32 frame;
    packet >> pid_to_blame;
    packet >> frame;

    std::string player = "??";
    std::lock_guard<std::recursive_mutex> lkp(m_crit.players);
    {
      auto it = m_players.find(pid_to_blame);
      if (it != m_players.end())
        player = it->second.name;
    }
    m_dialog->OnDesync(frame, player);
  }
  break;

  case NP_MSG_SYNC_GC_SRAM:
  {
    u8 sram[sizeof(g_SRAM.p_SRAM)];
    for (size_t i = 0; i < sizeof(g_SRAM.p_SRAM); ++i)
    {
      packet >> sram[i];
    }

    {
      std::lock_guard<std::recursive_mutex> lkg(m_crit.game);
      memcpy(g_SRAM.p_SRAM, sram, sizeof(g_SRAM.p_SRAM));
      g_SRAM_netplay_initialized = true;
    }
  }
  break;

  case NP_MSG_COMPUTE_MD5:
  {
    std::string file_identifier;
    packet >> file_identifier;

    ComputeMD5(file_identifier);
  }
  break;

  case NP_MSG_MD5_PROGRESS:
  {
    PlayerId pid;
    int progress;
    packet >> pid;
    packet >> progress;

    m_dialog->SetMD5Progress(pid, progress);
  }
  break;

  case NP_MSG_MD5_RESULT:
  {
    PlayerId pid;
    std::string result;
    packet >> pid;
    packet >> result;

    m_dialog->SetMD5Result(pid, result);
  }
  break;

  case NP_MSG_MD5_ERROR:
  {
    PlayerId pid;
    std::string error;
    packet >> pid;
    packet >> error;

    m_dialog->SetMD5Result(pid, error);
  }
  break;

  case NP_MSG_MD5_ABORT:
  {
    m_should_compute_MD5 = false;
    m_dialog->AbortMD5();
  }
  break;

  default:
    PanicAlertT("Unknown message received with id : %d", mid);
    break;
  }

  return 0;
}

void NetPlayClient::Send(const sf::Packet& packet)
{
  ENetPacket* epac =
      enet_packet_create(packet.getData(), packet.getDataSize(), ENET_PACKET_FLAG_RELIABLE);
  enet_peer_send(m_server, 0, epac);
}

void NetPlayClient::DisplayPlayersPing()
{
  if (!g_ActiveConfig.bShowNetPlayPing)
    return;

  OSD::AddTypedMessage(OSD::MessageType::NetPlayPing,
                       StringFromFormat("Ping: %u", GetPlayersMaxPing()), OSD::Duration::SHORT,
                       OSD::Color::CYAN);
}

u32 NetPlayClient::GetPlayersMaxPing() const
{
  return std::max_element(
             m_players.begin(), m_players.end(),
             [](const auto& a, const auto& b) { return a.second.ping < b.second.ping; })
      ->second.ping;
}

void NetPlayClient::Disconnect()
{
  ENetEvent netEvent;
  m_connecting = false;
  m_connection_state = ConnectionState::Failure;
  if (m_server)
    enet_peer_disconnect(m_server, 0);
  else
    return;

  while (enet_host_service(m_client, &netEvent, 3000) > 0)
  {
    switch (netEvent.type)
    {
    case ENET_EVENT_TYPE_RECEIVE:
      enet_packet_destroy(netEvent.packet);
      break;
    case ENET_EVENT_TYPE_DISCONNECT:
      m_server = nullptr;
      return;
    default:
      break;
    }
  }
  // didn't disconnect gracefully force disconnect
  enet_peer_reset(m_server);
  m_server = nullptr;
}

void NetPlayClient::SendAsync(sf::Packet&& packet)
{
  {
    std::lock_guard<std::recursive_mutex> lkq(m_crit.async_queue_write);
    m_async_queue.Push(std::move(packet));
  }
  ENetUtil::WakeupThread(m_client);
}

// called from ---NETPLAY--- thread
void NetPlayClient::ThreadFunc()
{
  while (m_do_loop.IsSet())
  {
    ENetEvent netEvent;
    int net;
    if (m_traversal_client)
      m_traversal_client->HandleResends();
    net = enet_host_service(m_client, &netEvent, 250);
    while (!m_async_queue.Empty())
    {
      Send(m_async_queue.Front());
      m_async_queue.Pop();
    }
    if (net > 0)
    {
      sf::Packet rpac;
      switch (netEvent.type)
      {
      case ENET_EVENT_TYPE_RECEIVE:
        rpac.append(netEvent.packet->data, netEvent.packet->dataLength);
        OnData(rpac);

        enet_packet_destroy(netEvent.packet);
        break;
      case ENET_EVENT_TYPE_DISCONNECT:
        m_dialog->OnConnectionLost();

        if (m_is_running.IsSet())
          StopGame();

        break;
      default:
        break;
      }
    }
  }

  Disconnect();
  return;
}

// called from ---GUI--- thread
void NetPlayClient::GetPlayerList(std::string& list, std::vector<int>& pid_list)
{
  std::lock_guard<std::recursive_mutex> lkp(m_crit.players);

  std::ostringstream ss;

  const auto enumerate_player_controller_mappings = [&ss](const PadMappingArray& mappings,
                                                          const Player& player) {
    for (size_t i = 0; i < mappings.size(); i++)
    {
      if (mappings[i] == player.pid)
        ss << i + 1;
      else
        ss << '-';
    }
  };

  for (const auto& entry : m_players)
  {
    const Player& player = entry.second;
    ss << player.name << "[" << static_cast<int>(player.pid) << "] : " << player.revision << " | ";

    enumerate_player_controller_mappings(m_pad_map, player);
    enumerate_player_controller_mappings(m_wiimote_map, player);

    ss << " |\nPing: " << player.ping << "ms\n";
    ss << "Status: ";

    switch (player.game_status)
    {
    case PlayerGameStatus::Ok:
      ss << "ready";
      break;

    case PlayerGameStatus::NotFound:
      ss << "game missing";
      break;

    default:
      ss << "unknown";
      break;
    }

    ss << "\n\n";

    pid_list.push_back(player.pid);
  }

  list = ss.str();
}

// called from ---GUI--- thread
std::vector<const Player*> NetPlayClient::GetPlayers()
{
  std::lock_guard<std::recursive_mutex> lkp(m_crit.players);
  std::vector<const Player*> players;

  for (const auto& pair : m_players)
    players.push_back(&pair.second);

  return players;
}

// called from ---GUI--- thread
void NetPlayClient::SendChatMessage(const std::string& msg)
{
  sf::Packet packet;
  packet << static_cast<MessageId>(NP_MSG_CHAT_MESSAGE);
  packet << msg;

  SendAsync(std::move(packet));
}

// called from ---CPU--- thread
void NetPlayClient::SendPadState(const int in_game_pad, const GCPadStatus& pad)
{
  sf::Packet packet;
  packet << static_cast<MessageId>(NP_MSG_PAD_DATA);
  packet << static_cast<PadMapping>(in_game_pad);
  packet << pad.button << pad.analogA << pad.analogB << pad.stickX << pad.stickY << pad.substickX
         << pad.substickY << pad.triggerLeft << pad.triggerRight;

  SendAsync(std::move(packet));
}

// called from ---CPU--- thread
void NetPlayClient::SendWiimoteState(const int in_game_pad, const NetWiimote& nw)
{
  sf::Packet packet;
  packet << static_cast<MessageId>(NP_MSG_WIIMOTE_DATA);
  packet << static_cast<PadMapping>(in_game_pad);
  packet << static_cast<u8>(nw.size());
  for (auto it : nw)
  {
    packet << it;
  }

  SendAsync(std::move(packet));
}

// called from ---GUI--- thread
void NetPlayClient::SendStartGamePacket()
{
  sf::Packet packet;
  packet << static_cast<MessageId>(NP_MSG_START_GAME);
  packet << m_current_game;

  SendAsync(std::move(packet));
}

// called from ---GUI--- thread
void NetPlayClient::SendStopGamePacket()
{
  sf::Packet packet;
  packet << static_cast<MessageId>(NP_MSG_STOP_GAME);

  SendAsync(std::move(packet));
}

// called from ---GUI--- thread
bool NetPlayClient::StartGame(const std::string& path)
{
  std::lock_guard<std::recursive_mutex> lkg(m_crit.game);
  SendStartGamePacket();

  if (m_is_running.IsSet())
  {
    PanicAlertT("Game is already running!");
    return false;
  }

  m_timebase_frame = 0;

  m_is_running.Set();
  NetPlay_Enable(this);

  ClearBuffers();

  if (m_dialog->IsRecording())
  {
    if (Movie::IsReadOnly())
      Movie::SetReadOnly(false);

    u8 controllers_mask = 0;
    for (unsigned int i = 0; i < 4; ++i)
    {
      if (m_pad_map[i] > 0)
        controllers_mask |= (1 << i);
      if (m_wiimote_map[i] > 0)
        controllers_mask |= (1 << (i + 4));
    }
    Movie::BeginRecordingInput(controllers_mask);
  }

  for (unsigned int i = 0; i < 4; ++i)
    WiimoteReal::ChangeWiimoteSource(i, m_wiimote_map[i] > 0 ? WIIMOTE_SRC_EMU : WIIMOTE_SRC_NONE);

  // boot game
  m_dialog->BootGame(path);

  UpdateDevices();

  return true;
}

// called from ---GUI--- thread
bool NetPlayClient::ChangeGame(const std::string&)
{
  return true;
}

// called from ---NETPLAY--- thread
void NetPlayClient::UpdateDevices()
{
  u8 local_pad = 0;
  u8 pad = 0;

  for (auto player_id : m_pad_map)
  {
    // Use local controller types for local controllers if they are compatible
    // Only GCController-like controllers are supported, GBA and similar
    // exotic devices are not supported on netplay.
    if (player_id == m_local_player->pid)
    {
      if (SerialInterface::SIDevice_IsGCController(SConfig::GetInstance().m_SIDevice[local_pad]))
      {
        SerialInterface::AddDevice(SConfig::GetInstance().m_SIDevice[local_pad], pad);
      }
      else
      {
        SerialInterface::AddDevice(SerialInterface::SIDEVICE_GC_CONTROLLER, pad);
      }
      local_pad++;
    }
    else if (player_id > 0)
    {
      SerialInterface::AddDevice(SerialInterface::SIDEVICE_GC_CONTROLLER, pad);
    }
    else
    {
      SerialInterface::AddDevice(SerialInterface::SIDEVICE_NONE, pad);
    }
    pad++;
  }
}

// called from ---NETPLAY--- thread
void NetPlayClient::ClearBuffers()
{
  // clear pad buffers, Clear method isn't thread safe
  for (unsigned int i = 0; i < 4; ++i)
  {
    while (m_pad_buffer[i].Size())
      m_pad_buffer[i].Pop();

    while (m_wiimote_buffer[i].Size())
      m_wiimote_buffer[i].Pop();
  }
}

// called from ---NETPLAY--- thread
void NetPlayClient::OnTraversalStateChanged()
{
  if (m_connection_state == ConnectionState::WaitingForTraversalClientConnection &&
      m_traversal_client->m_State == TraversalClient::Connected)
  {
    m_connection_state = ConnectionState::WaitingForTraversalClientConnectReady;
    m_traversal_client->ConnectToClient(m_host_spec);
  }
  else if (m_connection_state != ConnectionState::Failure &&
           m_traversal_client->m_State == TraversalClient::Failure)
  {
    Disconnect();
    m_dialog->OnTraversalError(m_traversal_client->m_FailureReason);
  }
}

// called from ---NETPLAY--- thread
void NetPlayClient::OnConnectReady(ENetAddress addr)
{
  if (m_connection_state == ConnectionState::WaitingForTraversalClientConnectReady)
  {
    m_connection_state = ConnectionState::Connecting;
    enet_host_connect(m_client, &addr, 0, 0);
  }
}

// called from ---NETPLAY--- thread
void NetPlayClient::OnConnectFailed(u8 reason)
{
  m_connecting = false;
  m_connection_state = ConnectionState::Failure;
  switch (reason)
  {
  case TraversalConnectFailedClientDidntRespond:
    PanicAlertT("Traversal server timed out connecting to the host");
    break;
  case TraversalConnectFailedClientFailure:
    PanicAlertT("Server rejected traversal attempt");
    break;
  case TraversalConnectFailedNoSuchClient:
    PanicAlertT("Invalid host");
    break;
  default:
    PanicAlertT("Unknown error %x", reason);
    break;
  }
}

// called from ---CPU--- thread
bool NetPlayClient::GetNetPads(const int pad_nb, GCPadStatus* pad_status)
{
  // The interface for this is extremely silly.
  //
  // Imagine a physical device that links three GameCubes together
  // and emulates NetPlay that way. Which GameCube controls which
  // in-game controllers can be configured on the device (m_pad_map)
  // but which sockets on each individual GameCube should be used
  // to control which players? The solution that Dolphin uses is
  // that we hardcode the knowledge that they go in order, so if
  // you have a 3P game with three GameCubes, then every single
  // controller should be plugged into slot 1.
  //
  // If you have a 4P game, then one of the GameCubes will have
  // a controller plugged into slot 1, and another in slot 2.
  //
  // The slot number is the "local" pad number, and what player
  // it actually means is the "in-game" pad number.

  // When the 1st in-game pad is polled, we assume the others will
  // will be polled as well. To reduce latency, we poll all local
  // controllers at once and then send the status to the other
  // clients.
  if (IsFirstInGamePad(pad_nb))
  {
    const int num_local_pads = NumLocalPads();
    for (int local_pad = 0; local_pad < num_local_pads; local_pad++)
    {
      switch (SConfig::GetInstance().m_SIDevice[local_pad])
      {
      case SerialInterface::SIDEVICE_WIIU_ADAPTER:
        *pad_status = GCAdapter::Input(local_pad);
        break;
      case SerialInterface::SIDEVICE_GC_CONTROLLER:
      default:
        *pad_status = Pad::GetStatus(local_pad);
        break;
      }

      int ingame_pad = LocalPadToInGamePad(local_pad);

      // adjust the buffer either up or down
      // inserting multiple padstates or dropping states
      while (m_pad_buffer[ingame_pad].Size() <= m_target_buffer_size)
      {
        // add to buffer
        m_pad_buffer[ingame_pad].Push(*pad_status);

        // send
        SendPadState(ingame_pad, *pad_status);
      }
    }
  }

  // Now, we either use the data pushed earlier, or wait for the
  // other clients to send it to us
  while (m_pad_buffer[pad_nb].Size() == 0)
  {
    if (!m_is_running.IsSet())
    {
      return false;
    }

    m_gc_pad_event.Wait();
  }

  m_pad_buffer[pad_nb].Pop(*pad_status);

  if (Movie::IsRecordingInput())
  {
    Movie::RecordInput(pad_status, pad_nb);
    Movie::InputUpdate();
  }
  else
  {
    Movie::CheckPadStatus(pad_status, pad_nb);
  }

  return true;
}

// called from ---CPU--- thread
bool NetPlayClient::WiimoteUpdate(int _number, u8* data, const u8 size, u8 reporting_mode)
{
  NetWiimote nw;
  {
    std::lock_guard<std::recursive_mutex> lkp(m_crit.players);

    // Only send data, if this Wiimote is mapped to this player
    if (m_wiimote_map[_number] == m_local_player->pid)
    {
      nw.assign(data, data + size);
      do
      {
        // add to buffer
        m_wiimote_buffer[_number].Push(nw);

        SendWiimoteState(_number, nw);
      } while (m_wiimote_buffer[_number].Size() <=
               m_target_buffer_size * 200 /
                   120);  // TODO: add a seperate setting for wiimote buffer?
    }

  }  // unlock players

  while (m_wiimote_buffer[_number].Size() == 0)
  {
    if (!m_is_running.IsSet())
    {
      return false;
    }

    // wait for receiving thread to push some data
    m_wii_pad_event.Wait();
  }

  m_wiimote_buffer[_number].Pop(nw);

  // If the reporting mode has changed, we just need to pop through the buffer,
  // until we reach a good input
  if (nw[1] != reporting_mode)
  {
    u32 tries = 0;
    while (nw[1] != reporting_mode)
    {
      while (m_wiimote_buffer[_number].Size() == 0)
      {
        if (!m_is_running.IsSet())
        {
          return false;
        }

        // wait for receiving thread to push some data
        m_wii_pad_event.Wait();
      }

      m_wiimote_buffer[_number].Pop(nw);

      ++tries;
      if (tries > m_target_buffer_size * 200 / 120)
        break;
    }

    // If it still mismatches, it surely desynced
    if (nw[1] != reporting_mode)
    {
      PanicAlertT("Netplay has desynced. There is no way to recover from this.");
      return false;
    }
  }

  memcpy(data, nw.data(), size);
  return true;
}

// called from ---GUI--- thread and ---NETPLAY--- thread (client side)
bool NetPlayClient::StopGame()
{
  m_is_running.Clear();

  // stop waiting for input
  m_gc_pad_event.Set();
  m_wii_pad_event.Set();

  NetPlay_Disable();

  // stop game
  m_dialog->StopGame();

  return true;
}

// called from ---GUI--- thread
void NetPlayClient::Stop()
{
  if (!m_is_running.IsSet())
    return;

  m_is_running.Clear();

  // stop waiting for input
  m_gc_pad_event.Set();
  m_wii_pad_event.Set();

  // Tell the server to stop if we have a pad mapped in game.
  if (LocalPlayerHasControllerMapped())
    SendStopGamePacket();
}

// called from ---GUI--- thread
bool NetPlayClient::LocalPlayerHasControllerMapped() const
{
  const auto mapping_matches_player_id = [this](const PadMapping& mapping) {
    return mapping == m_local_player->pid;
  };

  return std::any_of(m_pad_map.begin(), m_pad_map.end(), mapping_matches_player_id) ||
         std::any_of(m_wiimote_map.begin(), m_wiimote_map.end(), mapping_matches_player_id);
}

bool NetPlayClient::IsFirstInGamePad(int ingame_pad) const
{
  return std::none_of(m_pad_map.begin(), m_pad_map.begin() + ingame_pad,
                      [](auto mapping) { return mapping > 0; });
}

int NetPlayClient::NumLocalPads() const
{
  return static_cast<int>(std::count_if(m_pad_map.begin(), m_pad_map.end(), [this](auto mapping) {
    return mapping == m_local_player->pid;
  }));
}

int NetPlayClient::InGamePadToLocalPad(int ingame_pad) const
{
  // not our pad
  if (m_pad_map[ingame_pad] != m_local_player->pid)
    return 4;

  int local_pad = 0;
  int pad = 0;

  for (; pad < ingame_pad; pad++)
  {
    if (m_pad_map[pad] == m_local_player->pid)
      local_pad++;
  }

  return local_pad;
}

int NetPlayClient::LocalPadToInGamePad(int local_pad) const
{
  // Figure out which in-game pad maps to which local pad.
  // The logic we have here is that the local slots always
  // go in order.
  int local_pad_count = -1;
  int ingame_pad = 0;
  for (; ingame_pad < 4; ingame_pad++)
  {
    if (m_pad_map[ingame_pad] == m_local_player->pid)
      local_pad_count++;

    if (local_pad_count == local_pad)
      break;
  }

  return ingame_pad;
}

void NetPlayClient::SendTimeBase()
{
  std::lock_guard<std::mutex> lk(crit_netplay_client);

  u64 timebase = SystemTimers::GetFakeTimeBase();

  sf::Packet packet;
  packet << static_cast<MessageId>(NP_MSG_TIMEBASE);
  packet << static_cast<u32>(timebase);
  packet << static_cast<u32>(timebase << 32);
  packet << netplay_client->m_timebase_frame++;

  netplay_client->SendAsync(std::move(packet));
}

bool NetPlayClient::DoAllPlayersHaveGame()
{
  std::lock_guard<std::recursive_mutex> lkp(m_crit.players);

  return std::all_of(std::begin(m_players), std::end(m_players),
                     [](auto entry) { return entry.second.game_status == PlayerGameStatus::Ok; });
}

void NetPlayClient::ComputeMD5(const std::string& file_identifier)
{
  if (m_should_compute_MD5)
    return;

  m_dialog->ShowMD5Dialog(file_identifier);
  m_should_compute_MD5 = true;

  std::string file;
  if (file_identifier == WII_SDCARD)
    file = File::GetUserPath(F_WIISDCARD_IDX);
  else
    file = m_dialog->FindGame(file_identifier);

  if (file.empty() || !File::Exists(file))
  {
    sf::Packet packet;
    packet << static_cast<MessageId>(NP_MSG_MD5_ERROR);
    packet << "file not found";
    Send(packet);
    return;
  }

  m_MD5_thread = std::thread([this, file]() {
    std::string sum = MD5::MD5Sum(file, [&](int progress) {
      sf::Packet packet;
      packet << static_cast<MessageId>(NP_MSG_MD5_PROGRESS);
      packet << progress;
      Send(packet);

      return m_should_compute_MD5;
    });

    sf::Packet packet;
    packet << static_cast<MessageId>(NP_MSG_MD5_RESULT);
    packet << sum;
    Send(packet);
  });
  m_MD5_thread.detach();
}

// stuff hacked into dolphin

// called from ---CPU--- thread
// Actual Core function which is called on every frame
bool SerialInterface::CSIDevice_GCController::NetPlay_GetInput(int numPAD, GCPadStatus* PadStatus)
{
  std::lock_guard<std::mutex> lk(crit_netplay_client);

  if (netplay_client)
    return netplay_client->GetNetPads(numPAD, PadStatus);
  else
    return false;
}

bool WiimoteEmu::Wiimote::NetPlay_GetWiimoteData(int wiimote, u8* data, u8 size, u8 reporting_mode)
{
  std::lock_guard<std::mutex> lk(crit_netplay_client);

  if (netplay_client)
    return netplay_client->WiimoteUpdate(wiimote, data, size, reporting_mode);
  else
    return false;
}

// called from ---CPU--- thread
// so all players' games get the same time
//
// also called from ---GUI--- thread when starting input recording
u64 ExpansionInterface::CEXIIPL::NetPlay_GetEmulatedTime()
{
  std::lock_guard<std::mutex> lk(crit_netplay_client);

  if (netplay_client)
    return g_netplay_initial_rtc;
  else
    return 0;
}

// called from ---CPU--- thread
// return the local pad num that should rumble given a ingame pad num
int SerialInterface::CSIDevice_GCController::NetPlay_InGamePadToLocalPad(int numPAD)
{
  std::lock_guard<std::mutex> lk(crit_netplay_client);

  if (netplay_client)
    return netplay_client->InGamePadToLocalPad(numPAD);
  else
    return numPAD;
}

bool NetPlay::IsNetPlayRunning()
{
  return netplay_client != nullptr;
}

void NetPlay_Enable(NetPlayClient* const np)
{
  std::lock_guard<std::mutex> lk(crit_netplay_client);
  netplay_client = np;
}

void NetPlay_Disable()
{
  std::lock_guard<std::mutex> lk(crit_netplay_client);
  netplay_client = nullptr;
}