/* Copyright (C) 1997-2001 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. */ #include "qcommon.h" /* 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 even/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. If there is no information that needs to be transfered on a given frame, such as during the connection stage while waiting for the client to load, then a packet only needs to be delivered if there is something in the unacknowledged reliable */ cvar_t *showpackets; cvar_t *showdrop; cvar_t *qport; netadr_t net_from; sizebuf_t net_message; byte net_message_buffer[MAX_MSGLEN]; /* =============== Netchan_Init =============== */ void Netchan_Init (void) { int port; // pick a port value that should be nice and random port = Sys_Milliseconds() & 0xffff; showpackets = Cvar_Get ("showpackets", "0", 0); showdrop = Cvar_Get ("showdrop", "0", 0); qport = Cvar_Get ("qport", va("%i", port), CVAR_NOSET); } /* =============== Netchan_OutOfBand Sends an out-of-band datagram ================ */ void Netchan_OutOfBand (int net_socket, netadr_t adr, int length, byte *data) { sizebuf_t send; byte send_buf[MAX_MSGLEN]; // write the packet header SZ_Init (&send, send_buf, sizeof(send_buf)); MSG_WriteLong (&send, -1); // -1 sequence means out of band SZ_Write (&send, data, length); // send the datagram NET_SendPacket (net_socket, send.cursize, send.data, adr); } /* =============== Netchan_OutOfBandPrint Sends a text message in an out-of-band datagram ================ */ void Netchan_OutOfBandPrint (int net_socket, netadr_t adr, char *format, ...) { va_list argptr; static char string[MAX_MSGLEN - 4]; va_start (argptr, format); vsnprintf (string, MAX_MSGLEN - 4, format, argptr); va_end (argptr); Netchan_OutOfBand (net_socket, adr, strlen(string), (byte *)string); } /* ============== Netchan_Setup called to open a channel to a remote system ============== */ void Netchan_Setup (netsrc_t sock, netchan_t *chan, netadr_t adr, int qport) { memset (chan, 0, sizeof(*chan)); chan->sock = sock; chan->remote_address = adr; chan->qport = qport; chan->last_received = curtime; chan->incoming_sequence = 0; chan->outgoing_sequence = 1; SZ_Init (&chan->message, chan->message_buf, sizeof(chan->message_buf)); chan->message.allowoverflow = true; } /* =============== Netchan_CanReliable Returns true if the last reliable message has acked ================ */ qboolean Netchan_CanReliable (netchan_t *chan) { if (chan->reliable_length) return false; // waiting for ack return true; } qboolean Netchan_NeedReliable (netchan_t *chan) { qboolean send_reliable; // 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) { send_reliable = true; } return send_reliable; } /* =============== 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 send; byte send_buf[MAX_MSGLEN]; qboolean send_reliable; unsigned w1, w2; // check for message overflow if (chan->message.overflowed) { chan->fatal_error = true; Com_Printf ("%s:Outgoing message overflow\n" , NET_AdrToString (chan->remote_address)); return; } send_reliable = Netchan_NeedReliable (chan); 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; } // write the packet header SZ_Init (&send, send_buf, sizeof(send_buf)); w1 = ( chan->outgoing_sequence & ~(1<<31) ) | (send_reliable<<31); w2 = ( chan->incoming_sequence & ~(1<<31) ) | (chan->incoming_reliable_sequence<<31); chan->outgoing_sequence++; chan->last_sent = curtime; MSG_WriteLong (&send, w1); MSG_WriteLong (&send, w2); // send the qport if we are a client if (chan->sock == NS_CLIENT) MSG_WriteShort (&send, qport->value); // copy the reliable message to the packet first if (send_reliable) { SZ_Write (&send, chan->reliable_buf, chan->reliable_length); chan->last_reliable_sequence = chan->outgoing_sequence; } // add the unreliable part if space is available if (send.maxsize - send.cursize >= length) SZ_Write (&send, data, length); else Com_Printf ("Netchan_Transmit: dumped unreliable\n"); // send the datagram NET_SendPacket (chan->sock, send.cursize, send.data, chan->remote_address); if (showpackets->value) { if (send_reliable) Com_Printf ("send %4i : s=%i reliable=%i ack=%i rack=%i\n" , send.cursize , chan->outgoing_sequence - 1 , chan->reliable_sequence , chan->incoming_sequence , chan->incoming_reliable_sequence); else Com_Printf ("send %4i : s=%i ack=%i rack=%i\n" , send.cursize , chan->outgoing_sequence - 1 , chan->incoming_sequence , chan->incoming_reliable_sequence); } } /* ================= Netchan_Process called when the current net_message is from remote_address modifies net_message so that it points to the packet payload ================= */ qboolean Netchan_Process (netchan_t *chan, sizebuf_t *msg) { unsigned sequence, sequence_ack; unsigned reliable_ack, reliable_message; int qport; // get sequence numbers MSG_BeginReading (msg); sequence = MSG_ReadLong (msg); sequence_ack = MSG_ReadLong (msg); // read the qport if we are a server if (chan->sock == NS_SERVER) qport = MSG_ReadShort (msg); reliable_message = sequence >> 31; reliable_ack = sequence_ack >> 31; sequence &= ~(1<<31); sequence_ack &= ~(1<<31); if (showpackets->value) { if (reliable_message) Com_Printf ("recv %4i : s=%i reliable=%i ack=%i rack=%i\n" , msg->cursize , sequence , chan->incoming_reliable_sequence ^ 1 , sequence_ack , reliable_ack); else Com_Printf ("recv %4i : s=%i ack=%i rack=%i\n" , msg->cursize , sequence , sequence_ack , reliable_ack); } // // discard stale or duplicated packets // if (sequence <= chan->incoming_sequence) { if (showdrop->value) Com_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) { if (showdrop->value) Com_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 == 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 // chan->last_received = curtime; return true; }