network_command.cpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */
 
#include "../stdafx.h"
#include "network_admin.h"
#include "network_client.h"
#include "network_server.h"
#include "../command_func.h"
#include "../company_func.h"
#include "../settings_type.h"
#include "../airport_cmd.h"
#include "../aircraft_cmd.h"
#include "../autoreplace_cmd.h"
#include "../company_cmd.h"
#include "../depot_cmd.h"
#include "../dock_cmd.h"
#include "../economy_cmd.h"
#include "../engine_cmd.h"
#include "../error_func.h"
#include "../goal_cmd.h"
#include "../group_cmd.h"
#include "../industry_cmd.h"
#include "../landscape_cmd.h"
#include "../league_cmd.h"
#include "../misc_cmd.h"
#include "../news_cmd.h"
#include "../object_cmd.h"
#include "../order_cmd.h"
#include "../rail_cmd.h"
#include "../road_cmd.h"
#include "../roadveh_cmd.h"
#include "../settings_cmd.h"
#include "../signs_cmd.h"
#include "../station_cmd.h"
#include "../story_cmd.h"
#include "../subsidy_cmd.h"
#include "../terraform_cmd.h"
#include "../timetable_cmd.h"
#include "../town_cmd.h"
#include "../train_cmd.h"
#include "../tree_cmd.h"
#include "../tunnelbridge_cmd.h"
#include "../vehicle_cmd.h"
#include "../viewport_cmd.h"
#include "../water_cmd.h"
#include "../waypoint_cmd.h"
#include "../script/script_cmd.h"
 
#include "../safeguards.h"
 
static constexpr auto _callback_tuple = std::make_tuple(
  (CommandCallback *)nullptr, // Make sure this is actually a pointer-to-function.
  &CcBuildPrimaryVehicle,
  &CcBuildAirport,
  &CcBuildBridge,
  &CcPlaySound_CONSTRUCTION_WATER,
  &CcBuildDocks,
  &CcFoundTown,
  &CcBuildRoadTunnel,
  &CcBuildRailTunnel,
  &CcBuildWagon,
  &CcRoadDepot,
  &CcRailDepot,
  &CcPlaceSign,
  &CcPlaySound_EXPLOSION,
  &CcPlaySound_CONSTRUCTION_OTHER,
  &CcPlaySound_CONSTRUCTION_RAIL,
  &CcStation,
  &CcTerraform,
  &CcAI,
  &CcCloneVehicle,
  &CcCreateGroup,
  &CcFoundRandomTown,
  &CcRoadStop,
  &CcBuildIndustry,
  &CcStartStopVehicle,
  &CcGame,
  &CcAddVehicleNewGroup
);
 
#ifdef SILENCE_GCC_FUNCTION_POINTER_CAST
/*
 * We cast specialized function pointers to a generic one, but don't use the
 * converted value to call the function, which is safe, except that GCC
 * helpfully thinks it is not.
 *
 * "Any pointer to function can be converted to a pointer to a different function type.
 * Calling the function through a pointer to a different function type is undefined,
 * but converting such pointer back to pointer to the original function type yields
 * the pointer to the original function." */
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wcast-function-type"
#endif
 
/* Helpers to generate the callback table from the callback list. */
 
inline constexpr size_t _callback_tuple_size = std::tuple_size_v<decltype(_callback_tuple)>;
 
template <size_t... i>
inline auto MakeCallbackTable(std::index_sequence<i...>) noexcept
{
  return std::array<CommandCallback *, sizeof...(i)>{{ reinterpret_cast<CommandCallback *>(reinterpret_cast<void(*)()>(std::get<i>(_callback_tuple)))... }}; // MingW64 fails linking when casting a pointer to its own type. To work around, cast it to some other type first.
}
 
static auto _callback_table = MakeCallbackTable(std::make_index_sequence<_callback_tuple_size>{});
 
template <typename T> struct CallbackArgsHelper;
template <typename... Targs>
struct CallbackArgsHelper<void(*const)(Commands, const CommandCost &, Targs...)> {
  using Args = std::tuple<std::decay_t<Targs>...>;
};
 
 
/* Helpers to generate the command dispatch table from the command traits. */
 
template <Commands Tcmd> static CommandDataBuffer SanitizeCmdStrings(const CommandDataBuffer &data);
template <Commands Tcmd, size_t cb> static void UnpackNetworkCommand(const CommandPacket &cp);
template <Commands Tcmd> static void NetworkReplaceCommandClientId(CommandPacket &cp, ClientID client_id);
using UnpackNetworkCommandProc = void (*)(const CommandPacket &);
using UnpackDispatchT = std::array<UnpackNetworkCommandProc, _callback_tuple_size>;
struct CommandDispatch {
  CommandDataBuffer(*Sanitize)(const CommandDataBuffer &);
  void (*ReplaceClientId)(CommandPacket &, ClientID);
  UnpackDispatchT Unpack;
};
 
template <Commands Tcmd, size_t Tcb>
constexpr UnpackNetworkCommandProc MakeUnpackNetworkCommandCallback() noexcept
{
  /* Check if the callback matches with the command arguments. If not, don't generate an Unpack proc. */
  using Tcallback = std::tuple_element_t<Tcb, decltype(_callback_tuple)>;
  if constexpr (std::is_same_v<Tcallback, CommandCallback * const> || // Callback type is CommandCallback.
      std::is_same_v<Tcallback, CommandCallbackData * const> || // Callback type is CommandCallbackData.
      std::is_same_v<typename CommandTraits<Tcmd>::CbArgs, typename CallbackArgsHelper<Tcallback>::Args> || // Callback proc takes all command return values and parameters.
      (!std::is_void_v<typename CommandTraits<Tcmd>::RetTypes> && std::is_same_v<typename CallbackArgsHelper<typename CommandTraits<Tcmd>::RetCallbackProc const>::Args, typename CallbackArgsHelper<Tcallback>::Args>)) { // Callback return is more than CommandCost and the proc takes all return values.
    return &UnpackNetworkCommand<Tcmd, Tcb>;
  } else {
    return nullptr;
  }
}
 
template <Commands Tcmd, size_t... i>
constexpr UnpackDispatchT MakeUnpackNetworkCommand(std::index_sequence<i...>) noexcept
{
  return UnpackDispatchT{{ MakeUnpackNetworkCommandCallback<Tcmd, i>()...}};
}
 
template <typename T, T... i, size_t... j>
inline constexpr auto MakeDispatchTable(std::integer_sequence<T, i...>, std::index_sequence<j...>) noexcept
{
  return std::array<CommandDispatch, sizeof...(i)>{{ { &SanitizeCmdStrings<static_cast<Commands>(i)>, &NetworkReplaceCommandClientId<static_cast<Commands>(i)>, MakeUnpackNetworkCommand<static_cast<Commands>(i)>(std::make_index_sequence<_callback_tuple_size>{}) }... }};
}
static constexpr auto _cmd_dispatch = MakeDispatchTable(std::make_integer_sequence<std::underlying_type_t<Commands>, CMD_END>{}, std::make_index_sequence<_callback_tuple_size>{});
 
#ifdef SILENCE_GCC_FUNCTION_POINTER_CAST
# pragma GCC diagnostic pop
#endif
 
static CommandQueue _local_wait_queue;
static CommandQueue _local_execution_queue;
 
 
static size_t FindCallbackIndex(CommandCallback *callback)
{
  if (auto it = std::ranges::find(_callback_table, callback); it != std::end(_callback_table)) {
    return static_cast<size_t>(std::distance(std::begin(_callback_table), it));
  }
 
  return std::numeric_limits<size_t>::max();
}
 
void NetworkSendCommand(Commands cmd, StringID err_message, CommandCallback *callback, CompanyID company, const CommandDataBuffer &cmd_data)
{
  CommandPacket c;
  c.company  = company;
  c.cmd      = cmd;
  c.err_msg  = err_message;
  c.callback = callback;
  c.data     = cmd_data;
 
  if (_network_server) {
    /* If we are the server, we queue the command in our 'special' queue.
     *   In theory, we could execute the command right away, but then the
     *   client on the server can do everything 1 tick faster than others.
     *   So to keep the game fair, we delay the command with 1 tick
     *   which gives about the same speed as most clients.
     */
    c.frame = _frame_counter_max + 1;
    c.my_cmd = true;
 
    _local_wait_queue.push_back(c);
    return;
  }
 
  c.frame = 0; // The client can't tell which frame, so just make it 0
 
  /* Clients send their command to the server and forget all about the packet */
  MyClient::SendCommand(c);
}
 
void NetworkSyncCommandQueue(NetworkClientSocket *cs)
{
  for (auto &p : _local_execution_queue) {
    CommandPacket &c = cs->outgoing_queue.emplace_back(p);
    c.callback = nullptr;
  }
}
 
void NetworkExecuteLocalCommandQueue()
{
  assert(IsLocalCompany());
 
  CommandQueue &queue = (_network_server ? _local_execution_queue : ClientNetworkGameSocketHandler::my_client->incoming_queue);
 
  auto cp = queue.begin();
  for (; cp != queue.end(); cp++) {
    /* The queue is always in order, which means
     * that the first element will be executed first. */
    if (_frame_counter < cp->frame) break;
 
    if (_frame_counter > cp->frame) {
      /* If we reach here, it means for whatever reason, we've already executed
       * past the command we need to execute. */
      FatalError("[net] Trying to execute a packet in the past!");
    }
 
    /* We can execute this command */
    _current_company = cp->company;
    size_t cb_index = FindCallbackIndex(cp->callback);
    assert(cb_index < _callback_tuple_size);
    assert(_cmd_dispatch[cp->cmd].Unpack[cb_index] != nullptr);
    _cmd_dispatch[cp->cmd].Unpack[cb_index](*cp);
  }
  queue.erase(queue.begin(), cp);
 
  /* Local company may have changed, so we should not restore the old value */
  _current_company = _local_company;
}
 
void NetworkFreeLocalCommandQueue()
{
  _local_wait_queue.clear();
  _local_execution_queue.clear();
}
 
static void DistributeCommandPacket(CommandPacket &cp, const NetworkClientSocket *owner)
{
  CommandCallback *callback = cp.callback;
  cp.frame = _frame_counter_max + 1;
 
  for (NetworkClientSocket *cs : NetworkClientSocket::Iterate()) {
    if (cs->status >= NetworkClientSocket::STATUS_MAP) {
      /* Callbacks are only send back to the client who sent them in the
       *  first place. This filters that out. */
      cp.callback = (cs != owner) ? nullptr : callback;
      cp.my_cmd = (cs == owner);
      cs->outgoing_queue.push_back(cp);
    }
  }
 
  cp.callback = (nullptr != owner) ? nullptr : callback;
  cp.my_cmd = (nullptr == owner);
  _local_execution_queue.push_back(cp);
}
 
static void DistributeQueue(CommandQueue &queue, const NetworkClientSocket *owner)
{
#ifdef DEBUG_DUMP_COMMANDS
  /* When replaying we do not want this limitation. */
  int to_go = UINT16_MAX;
#else
  int to_go = _settings_client.network.commands_per_frame;
  if (owner == nullptr) {
    /* This is the server, use the commands_per_frame_server setting if higher */
    to_go = std::max<int>(to_go, _settings_client.network.commands_per_frame_server);
  }
#endif
 
  /* Not technically the most performant way, but consider clients rarely click more than once per tick. */
  for (auto cp = queue.begin(); cp != queue.end(); /* removing some items */) {
    /* Do not distribute commands when paused and the command is not allowed while paused. */
    if (_pause_mode != PM_UNPAUSED && !IsCommandAllowedWhilePaused(cp->cmd)) {
      ++cp;
      continue;
    }
 
    /* Limit the number of commands per client per tick. */
    if (--to_go < 0) break;
 
    DistributeCommandPacket(*cp, owner);
    NetworkAdminCmdLogging(owner, *cp);
    cp = queue.erase(cp);
  }
}
 
void NetworkDistributeCommands()
{
  /* First send the server's commands. */
  DistributeQueue(_local_wait_queue, nullptr);
 
  /* Then send the queues of the others. */
  for (NetworkClientSocket *cs : NetworkClientSocket::Iterate()) {
    DistributeQueue(cs->incoming_queue, cs);
  }
}
 
const char *NetworkGameSocketHandler::ReceiveCommand(Packet &p, CommandPacket &cp)
{
  cp.company = (CompanyID)p.Recv_uint8();
  cp.cmd     = static_cast<Commands>(p.Recv_uint16());
  if (!IsValidCommand(cp.cmd))               return "invalid command";
  if (GetCommandFlags(cp.cmd) & CMD_OFFLINE) return "single-player only command";
  cp.err_msg = p.Recv_uint16();
  cp.data    = _cmd_dispatch[cp.cmd].Sanitize(p.Recv_buffer());
 
  uint8_t callback = p.Recv_uint8();
  if (callback >= _callback_table.size() || _cmd_dispatch[cp.cmd].Unpack[callback] == nullptr)  return "invalid callback";
 
  cp.callback = _callback_table[callback];
  return nullptr;
}
 
void NetworkGameSocketHandler::SendCommand(Packet &p, const CommandPacket &cp)
{
  p.Send_uint8(cp.company);
  p.Send_uint16(cp.cmd);
  p.Send_uint16(cp.err_msg);
  p.Send_buffer(cp.data);
 
  size_t callback = FindCallbackIndex(cp.callback);
  if (callback > UINT8_MAX || _cmd_dispatch[cp.cmd].Unpack[callback] == nullptr) {
    Debug(net, 0, "Unknown callback for command; no callback sent (command: {})", cp.cmd);
    callback = 0; // _callback_table[0] == nullptr
  }
  p.Send_uint8 ((uint8_t)callback);
}
 
template <class T>
static inline void SetClientIdHelper(T &data, [[maybe_unused]] ClientID client_id)
{
  if constexpr (std::is_same_v<ClientID, T>) {
    data = client_id;
  }
}
 
template<class Ttuple, size_t... Tindices>
static inline void SetClientIds(Ttuple &values, ClientID client_id, std::index_sequence<Tindices...>)
{
  ((SetClientIdHelper(std::get<Tindices>(values), client_id)), ...);
}
 
template <Commands Tcmd>
static void NetworkReplaceCommandClientId(CommandPacket &cp, ClientID client_id)
{
  /* Unpack command parameters. */
  auto params = EndianBufferReader::ToValue<typename CommandTraits<Tcmd>::Args>(cp.data);
 
  /* Insert client id. */
  SetClientIds(params, client_id, std::make_index_sequence<std::tuple_size_v<decltype(params)>>{});
 
  /* Repack command parameters. */
  cp.data = EndianBufferWriter<CommandDataBuffer>::FromValue(params);
}
 
void NetworkReplaceCommandClientId(CommandPacket &cp, ClientID client_id)
{
  _cmd_dispatch[cp.cmd].ReplaceClientId(cp, client_id);
}
 
 
template <class T>
static inline void SanitizeSingleStringHelper([[maybe_unused]] CommandFlags cmd_flags, T &data)
{
  if constexpr (std::is_same_v<std::string, T>) {
    data = StrMakeValid(data, (!_network_server && HasFlag(cmd_flags, CMD_STR_CTRL)) ? SVS_ALLOW_CONTROL_CODE | SVS_REPLACE_WITH_QUESTION_MARK : SVS_REPLACE_WITH_QUESTION_MARK);
  }
}
 
template<class Ttuple, size_t... Tindices>
static inline void SanitizeStringsHelper(CommandFlags cmd_flags, Ttuple &values, std::index_sequence<Tindices...>)
{
  ((SanitizeSingleStringHelper(cmd_flags, std::get<Tindices>(values))), ...);
}
 
template <Commands Tcmd>
CommandDataBuffer SanitizeCmdStrings(const CommandDataBuffer &data)
{
  auto args = EndianBufferReader::ToValue<typename CommandTraits<Tcmd>::Args>(data);
  SanitizeStringsHelper(CommandTraits<Tcmd>::flags, args, std::make_index_sequence<std::tuple_size_v<typename CommandTraits<Tcmd>::Args>>{});
  return EndianBufferWriter<CommandDataBuffer>::FromValue(args);
}
 
template <Commands Tcmd, size_t Tcb>
void UnpackNetworkCommand(const CommandPacket &cp)
{
  auto args = EndianBufferReader::ToValue<typename CommandTraits<Tcmd>::Args>(cp.data);
  Command<Tcmd>::PostFromNet(cp.err_msg, std::get<Tcb>(_callback_tuple), cp.my_cmd, args);
}