src/network/network_stun.cpp

   1 /*
   2  * This file is part of OpenTTD.
   3  * 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.
   4  * 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.
   5  * 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/>.
   6  */
   7
   8 /** @file network_stun.cpp STUN sending/receiving part of the network protocol. */
   9
  10 #include "../stdafx.h"
  11 #include "../debug.h"
  12 #include "network.h"
  13 #include "network_coordinator.h"
  14 #include "network_stun.h"
  15
  16 #include "../safeguards.h"
  17
  18 /** Connect to the STUN server. */
  19 class NetworkStunConnecter : public TCPConnecter {
  20 private:
  21         ClientNetworkStunSocketHandler *stun_handler;
  22         std::string token;
  23         uint8 family;
  24
  25 public:
  26         /**
  27          * Initiate the connecting.
  28          * @param stun_handler The handler for this request.
  29          * @param connection_string The address of the server.
  30          */
  31         NetworkStunConnecter(ClientNetworkStunSocketHandler *stun_handler, const std::string &connection_string, const std::string &token, uint8 family) :
  32                 TCPConnecter(connection_string, NETWORK_STUN_SERVER_PORT, NetworkAddress(), family),
  33                 stun_handler(stun_handler),
  34                 token(token),
  35                 family(family)
  36         {
  37         }
  38
  39         void OnFailure() override
  40         {
  41                 this->stun_handler->connecter = nullptr;
  42
  43                 /* Connection to STUN server failed. For example, the client doesn't
  44                  * support IPv6, which means it will fail that attempt. */
  45
  46                 _network_coordinator_client.StunResult(this->token, this->family, false);
  47         }
  48
  49         void OnConnect(SOCKET s) override
  50         {
  51                 this->stun_handler->connecter = nullptr;
  52
  53                 assert(this->stun_handler->sock == INVALID_SOCKET);
  54                 this->stun_handler->sock = s;
  55
  56                 /* Store the local address; later connects will reuse it again.
  57                  * This is what makes STUN work for most NATs. */
  58                 this->stun_handler->local_addr = NetworkAddress::GetSockAddress(s);
  59
  60                 /* We leave the connection open till the real connection is setup later. */
  61         }
  62 };
  63
  64 /**
  65  * Connect to the STUN server over either IPv4 or IPv6.
  66  * @param token The token as received from the Game Coordinator.
  67  * @param family What IP family to use.
  68  */
  69 void ClientNetworkStunSocketHandler::Connect(const std::string &token, uint8 family)
  70 {
  71         this->token = token;
  72         this->family = family;
  73
  74         this->connecter = new NetworkStunConnecter(this, NetworkStunConnectionString(), token, family);
  75 }
  76
  77 /**
  78  * Send a STUN packet to the STUN server.
  79  * @param token The token as received from the Game Coordinator.
  80  * @param family What IP family this STUN request is for.
  81  * @return The handler for this STUN request.
  82  */
  83 std::unique_ptr<ClientNetworkStunSocketHandler> ClientNetworkStunSocketHandler::Stun(const std::string &token, uint8 family)
  84 {
  85         auto stun_handler = std::make_unique<ClientNetworkStunSocketHandler>();
  86
  87         stun_handler->Connect(token, family);
  88
  89         Packet *p = new Packet(PACKET_STUN_SERCLI_STUN);
  90         p->Send_uint8(NETWORK_COORDINATOR_VERSION);
  91         p->Send_string(token);
  92         p->Send_uint8(family);
  93
  94         stun_handler->SendPacket(p);
  95
  96         return stun_handler;
  97 }
  98
  99 NetworkRecvStatus ClientNetworkStunSocketHandler::CloseConnection(bool error)
 100 {
 101         NetworkStunSocketHandler::CloseConnection(error);
 102
 103         /* If our connecter is still pending, shut it down too. Otherwise the
 104          * callback of the connecter can call into us, and our object is most
 105          * likely about to be destroyed. */
 106         if (this->connecter != nullptr) {
 107                 this->connecter->Kill();
 108                 this->connecter = nullptr;
 109         }
 110
 111         return NETWORK_RECV_STATUS_OKAY;
 112 }
 113
 114 /**
 115  * Check whether we received/can send some data from/to the STUN server and
 116  * when that's the case handle it appropriately.
 117  */
 118 void ClientNetworkStunSocketHandler::SendReceive()
 119 {
 120         if (this->sock == INVALID_SOCKET) return;
 121
 122         /* We never attempt to receive anything on a STUN socket. After
 123          * connecting a STUN connection, the local address will be reused to
 124          * to establish the connection with the real server. If we would be to
 125          * read this socket, some OSes get confused and deliver us packets meant
 126          * for the real connection. It appears most OSes play best when we simply
 127          * never attempt to read it to start with (and the packets will remain
 128          * available on the other socket).
 129          * Protocol-wise, the STUN server will never send any packet back anyway. */
 130
 131         this->CanSendReceive();
 132         if (this->SendPackets() == SPS_ALL_SENT && !this->sent_result) {
 133                 /* We delay giving the GC the result this long, as to make sure we
 134                  * have sent the STUN packet first. This means the GC is more likely
 135                  * to have the result ready by the time our StunResult() packet
 136                  * arrives. */
 137                 this->sent_result = true;
 138                 _network_coordinator_client.StunResult(this->token, this->family, true);
 139         }
 140 }