/* Copyright (C) 1996-1997 Id Software, Inc. This program 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; either version 2 of the License, or (at your option) any later version. This program 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 this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. $Id: net_chan.c 643 2007-07-20 13:09:29Z d3urk $ */ #include "qwsvdef.h" #define PACKET_HEADER 8 /* packet header ------------- 31 sequence 1 does this message contain a reliable payload 31 acknowledge sequence 1 acknowledge receipt of even/odd message 16 qport The remote connection never knows if it missed a reliable message, the local side detects that it has been dropped by seeing a sequence acknowledge higher than the last reliable sequence, but without the correct evon/odd bit for the reliable set. If the sender notices that a reliable message has been dropped, it will be retransmitted. It will not be retransmitted again until a message after the retransmit has been acknowledged and the reliable still failed to get there. If the sequence number is -1, the packet should be handled without a netcon. The reliable message can be added to at any time by doing MSG_Write* (&netchan->message, ). If the message buffer is overflowed, either by a single message, or by multiple frames worth piling up while the last reliable transmit goes unacknowledged, the netchan signals a fatal error. Reliable messages are always placed first in a packet, then the unreliable message is included if there is sufficient room. To the receiver, there is no distinction between the reliable and unreliable parts of the message, they are just processed out as a single larger message. Illogical packet sequence numbers cause the packet to be dropped, but do not kill the connection. This, combined with the tight window of valid reliable acknowledgement numbers provides protection against malicious address spoofing. The qport field is a workaround for bad address translating routers that sometimes remap the client's source port on a packet during gameplay. If the base part of the net address matches and the qport matches, then the channel matches even if the IP port differs. The IP port should be updated to the new value before sending out any replies. */ cvar_t showpackets = {"showpackets", "0"}; cvar_t showdrop = {"showdrop", "0"}; cvar_t qport = {"qport", "0"}; /* =============== Netchan_Init =============== */ void Netchan_Init (void) { int port = 0xffff; // pick a port value that should be nice and random srand((unsigned)time(NULL)); port &= rand(); /* #ifdef _WIN32 port = ((int)(timeGetTime()*1000) * time(NULL)) & 0xffff; #else port = ((int)(getpid()+getuid()*1000) * time(NULL)) & 0xffff; #endif */ Cvar_Register (&showpackets); Cvar_Register (&showdrop); Cvar_Register (&qport); Cvar_SetValue (&qport, port); } /* =============== Netchan_OutOfBand Sends an out-of-band datagram ================ */ void Netchan_OutOfBand (netadr_t adr, int length, byte *data) { sizebuf_t send1; byte send_buf[MAX_MSGLEN + PACKET_HEADER]; // write the packet header send1.data = send_buf; send1.maxsize = sizeof(send_buf); send1.cursize = 0; MSG_WriteLong (&send1, -1); // -1 sequence means out of band SZ_Write (&send1, data, length); // send the datagram NET_SendPacket (send1.cursize, send1.data, adr); } /* =============== Netchan_OutOfBandPrint Sends a text message in an out-of-band datagram ================ */ void Netchan_OutOfBandPrint (netadr_t adr, char *format, ...) { va_list argptr; static char string[8192]; // ??? why static? - make program look big :-D va_start (argptr, format); vsnprintf (string, sizeof(string), format, argptr); va_end (argptr); Netchan_OutOfBand (adr, strlen(string), (byte *)string); } /* ============== Netchan_Setup called to open a channel to a remote system ============== */ void Netchan_Setup (netchan_t *chan, netadr_t adr, int qport1) { memset (chan, 0, sizeof(*chan)); chan->remote_address = adr; chan->last_received = realtime; chan->message.data = chan->message_buf; chan->message.allowoverflow = true; chan->message.maxsize = sizeof(chan->message_buf); chan->qport = qport1; chan->rate = 1.0/2500; } /* =============== Netchan_CanPacket Returns true if the bandwidth choke isn't active ================ */ #define MAX_BACKUP 400 qbool Netchan_CanPacket (netchan_t *chan) { if (chan->cleartime < realtime + MAX_BACKUP*chan->rate) return true; return false; } /* =============== Netchan_CanReliable Returns true if the bandwidth choke isn't ================ */ qbool Netchan_CanReliable (netchan_t *chan) { if (chan->reliable_length) return false; // waiting for ack return Netchan_CanPacket (chan); } /* =============== Netchan_Transmit tries to send an unreliable message to a connection, and handles the transmition / retransmition of the reliable messages. A 0 length will still generate a packet and deal with the reliable messages. ================ */ void Netchan_Transmit (netchan_t *chan, int length, byte *data) { sizebuf_t send1; byte send_buf[MAX_MSGLEN + PACKET_HEADER]; qbool send_reliable; unsigned w1, w2; int i; static double last_error_time = 0; double current_time; // check for message overflow current_time = Sys_DoubleTime(); if (chan->message.overflowed) { chan->fatal_error = true; if (last_error_time - current_time > 5.0 || (int)developer.value) { Con_Printf ("%s:Outgoing message overflow\n" , NET_AdrToString (chan->remote_address)); last_error_time = current_time; } return; } // if the remote side dropped the last reliable message, resend it send_reliable = false; if (chan->incoming_acknowledged > chan->last_reliable_sequence && chan->incoming_reliable_acknowledged != chan->reliable_sequence) send_reliable = true; // if the reliable transmit buffer is empty, copy the current message out if (!chan->reliable_length && chan->message.cursize) { memcpy (chan->reliable_buf, chan->message_buf, chan->message.cursize); chan->reliable_length = chan->message.cursize; chan->message.cursize = 0; chan->reliable_sequence ^= 1; send_reliable = true; } // write the packet header send1.data = send_buf; send1.maxsize = sizeof(send_buf); send1.cursize = 0; w1 = chan->outgoing_sequence | (send_reliable<<31); w2 = chan->incoming_sequence | (chan->incoming_reliable_sequence<<31); chan->outgoing_sequence++; MSG_WriteLong (&send1, w1); MSG_WriteLong (&send1, w2); // copy the reliable message to the packet first if (send_reliable) { SZ_Write (&send1, chan->reliable_buf, chan->reliable_length); chan->last_reliable_sequence = chan->outgoing_sequence; } // add the unreliable part if space is available if (send1.maxsize - send1.cursize >= length) SZ_Write (&send1, data, length); // send the datagram i = chan->outgoing_sequence & (MAX_LATENT-1); chan->outgoing_size[i] = send1.cursize; chan->outgoing_time[i] = realtime; NET_SendPacket (send1.cursize, send1.data, chan->remote_address); if (chan->cleartime < realtime) chan->cleartime = realtime + send1.cursize*chan->rate; else chan->cleartime += send1.cursize*chan->rate; if (sv.paused) chan->cleartime = realtime; if ((int)showpackets.value) Con_Printf ("--> s=%i(%i) a=%i(%i) %i\n" , chan->outgoing_sequence , send_reliable , chan->incoming_sequence , chan->incoming_reliable_sequence , send1.cursize); } /* ================= Netchan_Process called when the current net_message is from remote_address modifies net_message so that it points to the packet payload ================= */ qbool Netchan_Process (netchan_t *chan) { unsigned sequence, sequence_ack; unsigned reliable_ack, reliable_message; int qport1; if (!NET_CompareAdr (net_from, chan->remote_address)) return false; // get sequence numbers MSG_BeginReading (); sequence = MSG_ReadLong (); sequence_ack = MSG_ReadLong (); // read the qport qport1 = MSG_ReadShort (); reliable_message = sequence >> 31; reliable_ack = sequence_ack >> 31; sequence &= ~(1<<31); sequence_ack &= ~(1<<31); if ((int)showpackets.value) Con_Printf ("<-- s=%i(%i) a=%i(%i) %i\n" , sequence , reliable_message , sequence_ack , reliable_ack , net_message.cursize); // get a rate estimation #if 0 if (chan->outgoing_sequence - sequence_ack < MAX_LATENT) { int i; double time, rate; i = sequence_ack & (MAX_LATENT - 1); time = realtime - chan->outgoing_time[i]; time -= 0.1; // subtract 100 ms if (time <= 0) { // gotta be a digital link for <100 ms ping if (chan->rate > 1.0/5000) chan->rate = 1.0/5000; } else { if (chan->outgoing_size[i] < 512) { // only deal with small messages rate = chan->outgoing_size[i]/time; if (rate > 5000) rate = 5000; rate = 1.0/rate; if (chan->rate > rate) chan->rate = rate; } } } #endif // // discard stale or duplicated packets // if (sequence <= (unsigned)chan->incoming_sequence) { if ((int)showdrop.value) Con_Printf ("%s:Out of order packet %i at %i\n" , NET_AdrToString (chan->remote_address) , sequence , chan->incoming_sequence); return false; } // // dropped packets don't keep the message from being used // chan->dropped = sequence - (chan->incoming_sequence+1); if (chan->dropped > 0) { chan->drop_count += 1; if ((int)showdrop.value) Con_Printf ("%s:Dropped %i packets at %i\n" , NET_AdrToString (chan->remote_address) , chan->dropped , sequence); } // // if the current outgoing reliable message has been acknowledged // clear the buffer to make way for the next // if (reliable_ack == (unsigned)chan->reliable_sequence) chan->reliable_length = 0; // it has been received // // if this message contains a reliable message, bump incoming_reliable_sequence // chan->incoming_sequence = sequence; chan->incoming_acknowledged = sequence_ack; chan->incoming_reliable_acknowledged = reliable_ack; if (reliable_message) chan->incoming_reliable_sequence ^= 1; // // the message can now be read from the current message pointer // update statistics counters // chan->frame_latency = chan->frame_latency*OLD_AVG + (chan->outgoing_sequence-sequence_ack)*(1.0-OLD_AVG); chan->frame_rate = chan->frame_rate*OLD_AVG + (realtime-chan->last_received)*(1.0-OLD_AVG); chan->good_count += 1; chan->last_received = realtime; return true; }