tcp_listen.h

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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 <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */
 
#ifndef NETWORK_CORE_TCP_LISTEN_H
#define NETWORK_CORE_TCP_LISTEN_H
 
#include "tcp.h"
#include "../network.h"
#include "../network_func.h"
#include "../network_internal.h"
#include "../../debug.h"
 
#include "table/strings.h"
 
template <class Tsocket, PacketType Tfull_packet, PacketType Tban_packet>
class TCPListenHandler {
  static SocketList sockets;
 
public:
  static bool ValidateClient(SOCKET s, NetworkAddress &address)
  {
    /* Check if the client is banned. */
    for (const auto &entry : _network_ban_list) {
      if (address.IsInNetmask(entry)) {
        Packet p(nullptr, Tban_packet);
        p.PrepareToSend();
 
        Debug(net, 2, "[{}] Banned ip tried to join ({}), refused", Tsocket::GetName(), entry);
 
        if (p.TransferOut(SocketSender{s}) < 0) {
          Debug(net, 0, "[{}] send failed: {}", Tsocket::GetName(), NetworkError::GetLast().AsString());
        }
        closesocket(s);
        return false;
      }
    }
 
    /* Can we handle a new client? */
    if (!Tsocket::AllowConnection()) {
      /* No more clients allowed?
       * Send to the client that we are full! */
      Packet p(nullptr, Tfull_packet);
      p.PrepareToSend();
 
      if (p.TransferOut(SocketSender{s}) < 0) {
        Debug(net, 0, "[{}] send failed: {}", Tsocket::GetName(), NetworkError::GetLast().AsString());
      }
      closesocket(s);
 
      return false;
    }
 
    return true;
  }
 
  static void AcceptClient(SOCKET ls)
  {
    for (;;) {
      struct sockaddr_storage sin{};
      socklen_t sin_len = sizeof(sin);
      SOCKET s = accept(ls, (struct sockaddr*)&sin, &sin_len);
      if (s == INVALID_SOCKET) return;
#ifdef __EMSCRIPTEN__
      sin_len = FixAddrLenForEmscripten(sin);
#endif
 
      SetNonBlocking(s); // XXX error handling?
 
      NetworkAddress address(sin, sin_len);
      Debug(net, 3, "[{}] Client connected from {} on frame {}", Tsocket::GetName(), address.GetHostname(), _frame_counter);
 
      SetNoDelay(s); // XXX error handling?
 
      if (!Tsocket::ValidateClient(s, address)) continue;
      Tsocket::AcceptConnection(s, address);
    }
  }
 
  static bool Receive()
  {
    fd_set read_fd, write_fd;
    struct timeval tv;
 
    FD_ZERO(&read_fd);
    FD_ZERO(&write_fd);
 
 
    for (Tsocket *cs : Tsocket::Iterate()) {
      FD_SET(cs->sock, &read_fd);
      FD_SET(cs->sock, &write_fd);
    }
 
    /* take care of listener port */
    for (auto &s : sockets) {
      FD_SET(s.first, &read_fd);
    }
 
    tv.tv_sec = tv.tv_usec = 0; // don't block at all.
    if (select(FD_SETSIZE, &read_fd, &write_fd, nullptr, &tv) < 0) return false;
 
    /* accept clients.. */
    for (auto &s : sockets) {
      if (FD_ISSET(s.first, &read_fd)) AcceptClient(s.first);
    }
 
    /* read stuff from clients */
    for (Tsocket *cs : Tsocket::Iterate()) {
      cs->writable = !!FD_ISSET(cs->sock, &write_fd);
      if (FD_ISSET(cs->sock, &read_fd)) {
        cs->ReceivePackets();
      }
    }
    return _networking;
  }
 
  static bool Listen(uint16_t port)
  {
    assert(sockets.empty());
 
    NetworkAddressList addresses;
    GetBindAddresses(&addresses, port);
 
    for (NetworkAddress &address : addresses) {
      address.Listen(SOCK_STREAM, &sockets);
    }
 
    if (sockets.empty()) {
      Debug(net, 0, "Could not start network: could not create listening socket");
      ShowNetworkError(STR_NETWORK_ERROR_SERVER_START);
      return false;
    }
 
    return true;
  }
 
  static void CloseListeners()
  {
    for (auto &s : sockets) {
      closesocket(s.first);
    }
    sockets.clear();
    Debug(net, 5, "[{}] Closed listeners", Tsocket::GetName());
  }
};
 
template <class Tsocket, PacketType Tfull_packet, PacketType Tban_packet> SocketList TCPListenHandler<Tsocket, Tfull_packet, Tban_packet>::sockets;
 
#endif /* NETWORK_CORE_TCP_LISTEN_H */