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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/>.
*/
/**
* @file core/udp.cpp Basic functions to receive and send UDP packets.
*/
#include "../../stdafx.h"
#include "../../date_func.h"
#include "../../debug.h"
#include "game_info.h"
#include "udp.h"
#include "../../safeguards.h"
/**
* Create an UDP socket but don't listen yet.
* @param bind the addresses to bind to.
*/
NetworkUDPSocketHandler::NetworkUDPSocketHandler(NetworkAddressList *bind)
{
if (bind != nullptr) {
for (NetworkAddress &addr : *bind) {
this->bind.push_back(addr);
}
} else {
/* As an empty hostname and port 0 don't go well when
* resolving it we need to add an address for each of
* the address families we support. */
this->bind.emplace_back("", 0, AF_INET);
this->bind.emplace_back("", 0, AF_INET6);
}
}
/**
* Start listening on the given host and port.
* @return true if at least one port is listening
*/
bool NetworkUDPSocketHandler::Listen()
{
/* Make sure socket is closed */
this->CloseSocket();
for (NetworkAddress &addr : this->bind) {
addr.Listen(SOCK_DGRAM, &this->sockets);
}
return this->sockets.size() != 0;
}
/**
* Close the actual UDP socket.
*/
void NetworkUDPSocketHandler::CloseSocket()
{
for (auto &s : this->sockets) {
closesocket(s.second);
}
this->sockets.clear();
}
/**
* Send a packet over UDP
* @param p the packet to send
* @param recv the receiver (target) of the packet
* @param all send the packet using all sockets that can send it
* @param broadcast whether to send a broadcast message
*/
void NetworkUDPSocketHandler::SendPacket(Packet *p, NetworkAddress *recv, bool all, bool broadcast)
{
if (this->sockets.size() == 0) this->Listen();
for (auto &s : this->sockets) {
/* Make a local copy because if we resolve it we cannot
* easily unresolve it so we can resolve it later again. */
NetworkAddress send(*recv);
/* Not the same type */
if (!send.IsFamily(s.first.GetAddress()->ss_family)) continue;
p->PrepareToSend();
if (broadcast) {
/* Enable broadcast */
unsigned long val = 1;
if (setsockopt(s.second, SOL_SOCKET, SO_BROADCAST, (char *) &val, sizeof(val)) < 0) {
Debug(net, 1, "Setting broadcast mode failed: {}", NetworkError::GetLast().AsString());
}
}
/* Send the buffer */
ssize_t res = p->TransferOut<int>(sendto, s.second, 0, (const struct sockaddr *)send.GetAddress(), send.GetAddressLength());
Debug(net, 7, "sendto({})", send.GetAddressAsString());
/* Check for any errors, but ignore it otherwise */
if (res == -1) Debug(net, 1, "sendto({}) failed: {}", send.GetAddressAsString(), NetworkError::GetLast().AsString());
if (!all) break;
}
}
/**
* Receive a packet at UDP level
*/
void NetworkUDPSocketHandler::ReceivePackets()
{
for (auto &s : this->sockets) {
for (int i = 0; i < 1000; i++) { // Do not infinitely loop when DoSing with UDP
struct sockaddr_storage client_addr;
memset(&client_addr, 0, sizeof(client_addr));
/* The limit is UDP_MTU, but also allocate that much as we need to read the whole packet in one go. */
Packet p(this, UDP_MTU, UDP_MTU);
socklen_t client_len = sizeof(client_addr);
/* Try to receive anything */
SetNonBlocking(s.second); // Some OSes seem to lose the non-blocking status of the socket
ssize_t nbytes = p.TransferIn<int>(recvfrom, s.second, 0, (struct sockaddr *)&client_addr, &client_len);
/* Did we get the bytes for the base header of the packet? */
if (nbytes <= 0) break; // No data, i.e. no packet
if (nbytes <= 2) continue; // Invalid data; try next packet
#ifdef __EMSCRIPTEN__
client_len = FixAddrLenForEmscripten(client_addr);
#endif
NetworkAddress address(client_addr, client_len);
/* If the size does not match the packet must be corrupted.
* Otherwise it will be marked as corrupted later on. */
if (!p.ParsePacketSize() || (size_t)nbytes != p.Size()) {
Debug(net, 1, "Received a packet with mismatching size from {}", address.GetAddressAsString());
continue;
}
p.PrepareToRead();
/* Handle the packet */
this->HandleUDPPacket(&p, &address);
}
}
}
/**
* Handle an incoming packets by sending it to the correct function.
* @param p the received packet
* @param client_addr the sender of the packet
*/
void NetworkUDPSocketHandler::HandleUDPPacket(Packet *p, NetworkAddress *client_addr)
{
PacketUDPType type;
/* New packet == new client, which has not quit yet */
this->Reopen();
type = (PacketUDPType)p->Recv_uint8();
switch (this->HasClientQuit() ? PACKET_UDP_END : type) {
case PACKET_UDP_CLIENT_FIND_SERVER: this->Receive_CLIENT_FIND_SERVER(p, client_addr); break;
case PACKET_UDP_SERVER_RESPONSE: this->Receive_SERVER_RESPONSE(p, client_addr); break;
default:
if (this->HasClientQuit()) {
Debug(net, 0, "[udp] Received invalid packet type {} from {}", type, client_addr->GetAddressAsString());
} else {
Debug(net, 0, "[udp] Received illegal packet from {}", client_addr->GetAddressAsString());
}
break;
}
}
/**
* Helper for logging receiving invalid packets.
* @param type The received packet type.
* @param client_addr The address we received the packet from.
*/
void NetworkUDPSocketHandler::ReceiveInvalidPacket(PacketUDPType type, NetworkAddress *client_addr)
{
Debug(net, 0, "[udp] Received packet type {} on wrong port from {}", type, client_addr->GetAddressAsString());
}
void NetworkUDPSocketHandler::Receive_CLIENT_FIND_SERVER(Packet *p, NetworkAddress *client_addr) { this->ReceiveInvalidPacket(PACKET_UDP_CLIENT_FIND_SERVER, client_addr); }
void NetworkUDPSocketHandler::Receive_SERVER_RESPONSE(Packet *p, NetworkAddress *client_addr) { this->ReceiveInvalidPacket(PACKET_UDP_SERVER_RESPONSE, client_addr); }
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