alias/alias_smedia.c

   1 /*
   2  * Copyright (c) 2000-2002 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * alias_smedia.c
  24  *
  25  * Copyright (c) 2000 Whistle Communications, Inc.
  26  * All rights reserved.
  27  *
  28  * Subject to the following obligations and disclaimer of warranty, use and
  29  * redistribution of this software, in source or object code forms, with or
  30  * without modifications are expressly permitted by Whistle Communications;
  31  * provided, however, that:
  32  * 1. Any and all reproductions of the source or object code must include the
  33  *    copyright notice above and the following disclaimer of warranties; and
  34  * 2. No rights are granted, in any manner or form, to use Whistle
  35  *    Communications, Inc. trademarks, including the mark "WHISTLE
  36  *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
  37  *    such appears in the above copyright notice or in the software.
  38  *
  39  * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
  40  * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
  41  * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
  42  * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
  43  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
  44  * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
  45  * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
  46  * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
  47  * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
  48  * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
  49  * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
  50  * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
  51  * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
  52  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  53  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  54  * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
  55  * OF SUCH DAMAGE.
  56  *
  57  * Copyright (c) 2000  Junichi SATOH <junichi@astec.co.jp>
  58  *                                   <junichi@junichi.org>
  59  * All rights reserved.
  60  *
  61  * Redistribution and use in source and binary forms, with or without
  62  * modification, are permitted provided that the following conditions
  63  * are met:
  64  * 1. Redistributions of source code must retain the above copyright
  65  *    notice, this list of conditions and the following disclaimer.
  66  * 2. Redistributions in binary form must reproduce the above copyright
  67  *    notice, this list of conditions and the following disclaimer in the
  68  *    documentation and/or other materials provided with the distribution.
  69  *
  70  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  71  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  72  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  73  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  74  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  75  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  76  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  77  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  78  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  79  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  80  * SUCH DAMAGE.
  81  *
  82  * Authors: Erik Salander <erik@whistle.com>
  83  *          Junichi SATOH <junichi@astec.co.jp>
  84  *                        <junichi@junichi.org>
  85  *
  86  * Based upon:
  87  * $FreeBSD: src/lib/libalias/alias_smedia.c,v 1.1.2.4 2001/03/05 03:48:00 kris Exp $
  88  */
  89
  90 /*
  91    Alias_smedia.c is meant to contain the aliasing code for streaming media
  92    protocols.  It performs special processing for RSTP sessions under TCP.
  93    Specifically, when a SETUP request is sent by a client, or a 200 reply
  94    is sent by a server, it is intercepted and modified.  The address is
  95    changed to the gateway machine and an aliasing port is used.
  96
  97    More specifically, the "client_port" configuration parameter is
  98    parsed for SETUP requests.  The "server_port" configuration parameter is
  99    parsed for 200 replies eminating from a server.  This is intended to handle
 100    the unicast case.
 101
 102    RTSP also allows a redirection of a stream to another client by using the
 103    "destination" configuration parameter.  The destination config parm would
 104    indicate a different IP address.  This function is NOT supported by the
 105    RTSP translation code below.
 106
 107    The RTSP multicast functions without any address translation intervention.
 108
 109    For this routine to work, the SETUP/200 must fit entirely
 110    into a single TCP packet.  This is typically the case, but exceptions
 111    can easily be envisioned under the actual specifications.
 112
 113    Probably the most troubling aspect of the approach taken here is
 114    that the new SETUP/200 will typically be a different length, and
 115    this causes a certain amount of bookkeeping to keep track of the
 116    changes of sequence and acknowledgment numbers, since the client
 117    machine is totally unaware of the modification to the TCP stream.
 118
 119    Initial version:  May, 2000 (eds)
 120 */
 121
 122
 123 #include <stdio.h>
 124 #include <string.h>
 125 #include <sys/types.h>
 126 #include <netinet/in_systm.h>
 127 #include <netinet/in.h>
 128 #include <netinet/ip.h>
 129 #include <netinet/tcp.h>
 130 #include <netinet/udp.h>
 131
 132 #include "alias_local.h"
 133
 134 #define RTSP_CONTROL_PORT_NUMBER_1 554
 135 #define RTSP_CONTROL_PORT_NUMBER_2 7070
 136 #define RTSP_PORT_GROUP            2
 137
 138 #define ISDIGIT(a) (((a) >= '0') && ((a) <= '9'))
 139
 140 static int
 141 search_string(char *data, int dlen, const char *search_str)
 142 {
 143     int i, j, k;
 144     int search_str_len;
 145
 146     search_str_len = strlen(search_str);
 147     for (i = 0; i < dlen - search_str_len; i++) {
 148         for (j = i, k = 0; j < dlen - search_str_len; j++, k++) {
 149             if (data[j] != search_str[k] &&
 150                 data[j] != search_str[k] - ('a' - 'A')) {
 151                 break;
 152             }
 153             if (k == search_str_len - 1) {
 154                 return j + 1;
 155             }
 156         }
 157     }
 158     return -1;
 159 }
 160
 161 static int
 162 alias_rtsp_out(struct ip *pip,
 163                    struct alias_link *link,
 164                    char *data,
 165                    const char *port_str)
 166 {
 167     int     hlen, tlen, dlen;
 168     struct tcphdr *tc;
 169     int     i, j, pos, state, port_dlen, new_dlen, delta;
 170     u_short p[2], new_len;
 171     u_short sport, eport, base_port;
 172     u_short salias = 0, ealias = 0, base_alias = 0;
 173     const char *transport_str = "transport:";
 174     char    newdata[2048], *port_data, *port_newdata, stemp[80];
 175     int     links_created = 0, pkt_updated = 0;
 176     struct alias_link *rtsp_link = NULL;
 177     struct in_addr null_addr;
 178
 179     /* Calculate data length of TCP packet */
 180     tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
 181     hlen = (pip->ip_hl + tc->th_off) << 2;
 182     tlen = ntohs(pip->ip_len);
 183     dlen = tlen - hlen;
 184
 185         if (dlen > sizeof(newdata)) {
 186 #if DEBUG
 187                 fprintf(stderr, "alias_rtsp_out: data len too big");
 188 #endif
 189                 return -1;
 190         }
 191     /* Find keyword, "Transport: " */
 192     pos = search_string(data, dlen, transport_str);
 193     if (pos < 0) {
 194 #if DEBUG
 195                 fprintf(stderr, "alias_rtsp_out: Transport not found");
 196 #endif
 197                 return -1;
 198     }
 199         if (pos >= sizeof(newdata)) {
 200 #if DEBUG
 201                 fprintf(stderr, "alias_rtsp_out: Transport too far");
 202 #endif
 203                 return -1;
 204         }
 205     port_data = data + pos;
 206     port_dlen = dlen - pos;
 207
 208     memcpy(newdata, data, pos);
 209     port_newdata = newdata + pos;
 210
 211     while (port_dlen > strlen(port_str)) {
 212                 /* Find keyword, appropriate port string */
 213                 pos = search_string(port_data, port_dlen, port_str);
 214                 if (pos < 0 || port_data + pos + 1 > newdata + sizeof(newdata)) {
 215 #if DEBUG
 216                         fprintf(stderr, "alias_rtsp_out: port_str too far\n");
 217 #endif
 218                         break;
 219                 }
 220
 221                 memcpy (port_newdata, port_data, pos + 1);
 222                 port_newdata += (pos + 1);
 223
 224                 p[0] = p[1] = 0;
 225                 sport = eport = 0;
 226                 state = 0;
 227                 for (i = pos; i < port_dlen; i++) {
 228                         switch(state) {
 229                         case 0:
 230                                 if (port_data[i] == '=') {
 231                                         state++;
 232                                 }
 233                                 break;
 234                         case 1:
 235                                 if (ISDIGIT(port_data[i])) {
 236                                         p[0] = p[0] * 10 + port_data[i] - '0';
 237                                 } else {
 238                                         if (port_data[i] == ';') {
 239                                                 state = 3;
 240                                         }
 241                                         if (port_data[i] == '-') {
 242                                                 state++;
 243                                         }
 244                                 }
 245                                 break;
 246                         case 2:
 247                                 if (ISDIGIT(port_data[i])) {
 248                                         p[1] = p[1] * 10 + port_data[i] - '0';
 249                                 } else {
 250                                         state++;
 251                                 }
 252                                 break;
 253                         case 3:
 254                                 base_port = p[0];
 255                                 sport = htons(p[0]);
 256                                 eport = htons(p[1]);
 257
 258                                 if (!links_created) {
 259
 260                                         links_created = 1;
 261                                         /* Find an even numbered port number base that
 262                                          satisfies the contiguous number of ports we need  */
 263                                         null_addr.s_addr = 0;
 264                                         if (0 == (salias = FindNewPortGroup(null_addr,
 265                                                                                                                 FindAliasAddress(pip->ip_src),
 266                                                                                                                 sport, 0,
 267                                                                                                                 RTSP_PORT_GROUP,
 268                                                                                                                 IPPROTO_UDP, 1))) {
 269 #ifdef DEBUG
 270                                                 fprintf(stderr,
 271                                                                 "PacketAlias/RTSP: Cannot find contiguous RTSP data ports\n");
 272 #endif
 273                                         } else {
 274
 275                                                 base_alias = ntohs(salias);
 276                                                 for (j = 0; j < RTSP_PORT_GROUP; j++) {
 277                                                         /* Establish link to port found in RTSP packet */
 278                                                         rtsp_link = FindRtspOut(GetOriginalAddress(link), null_addr,
 279                                                                                                         htons(base_port + j), htons(base_alias + j),
 280                                                                                                         IPPROTO_UDP);
 281                                                         if (rtsp_link != NULL) {
 282 #ifndef NO_FW_PUNCH
 283                                                                 /* Punch hole in firewall */
 284                                                                 PunchFWHole(rtsp_link);
 285 #endif
 286                                                         } else {
 287 #ifdef DEBUG
 288                                                                 fprintf(stderr,
 289                                                                                 "PacketAlias/RTSP: Cannot allocate RTSP data ports\n");
 290 #endif
 291                                                                 break;
 292                                                         }
 293                                                 }
 294                                         }
 295                                         ealias = htons(base_alias + (RTSP_PORT_GROUP - 1));
 296                                 }
 297
 298                                 if (salias && rtsp_link) {
 299                                         size_t lentmp;
 300
 301                                         /* Copy into IP packet */
 302                                         sprintf(stemp, "%d", ntohs(salias));
 303                                         lentmp = strlen(stemp);
 304                                         /* account for ending ';' */
 305                                         if (port_newdata + lentmp + 1 > newdata + sizeof(newdata)) {
 306 #if DEBUG
 307                                                 fprintf(stderr, "PacketAlias/RTSP: salias too far\n");
 308 #endif
 309                                                 break;
 310                                         }
 311                                         memcpy(port_newdata, stemp, lentmp);
 312                                         port_newdata += lentmp;
 313
 314                                         if (eport != 0) {
 315                                                 sprintf(stemp, "%d", ntohs(ealias));
 316                                                 lentmp = strlen(stemp);
 317
 318                                                 /* account for middle '-' and for ending ';' */
 319                                                 if (port_newdata + lentmp + 2 > newdata + sizeof(newdata)) {
 320 #if DEBUG
 321                                                         fprintf(stderr, "PacketAlias/RTSP: ealias too far\n");
 322 #endif
 323                                                         break;
 324                                                 }
 325                                                 *port_newdata = '-';
 326                                                 port_newdata++;
 327
 328                                                 /* Copy into IP packet */
 329                                                 memcpy(port_newdata, stemp, lentmp);
 330                                                 port_newdata += lentmp;
 331                                         }
 332                                         pkt_updated = 1;
 333
 334                                         *port_newdata = ';';
 335                                         port_newdata++;
 336                                 }
 337                                 state++;
 338                                 break;
 339                         }
 340                         if (state > 3) {
 341                                 break;
 342                         }
 343                 }
 344                 port_data += i;
 345                 port_dlen -= i;
 346     }
 347
 348     if (!pkt_updated) {
 349 #if DEBUG
 350                 fprintf(stderr, "PacketAlias/RTSP: Packet not updated\n");
 351 #endif
 352                 return -1;
 353         }
 354
 355     memcpy (port_newdata, port_data, port_dlen);
 356     port_newdata += port_dlen;
 357     *port_newdata = '\0';
 358
 359     /* Create new packet */
 360     new_dlen = port_newdata - newdata;
 361     memcpy (data, newdata, new_dlen);
 362
 363     SetAckModified(link);
 364     delta = GetDeltaSeqOut(pip, link);
 365     AddSeq(pip, link, delta + new_dlen - dlen);
 366
 367     new_len = htons(hlen + new_dlen);
 368     DifferentialChecksum(&pip->ip_sum,
 369                                                  &new_len,
 370                                                  &pip->ip_len,
 371                                                  1);
 372     pip->ip_len = new_len;
 373
 374     tc->th_sum = 0;
 375     tc->th_sum = TcpChecksum(pip);
 376
 377     return 0;
 378 }
 379
 380 /* Support the protocol used by early versions of RealPlayer */
 381
 382 static int
 383 alias_pna_out(struct ip *pip,
 384                   struct alias_link *link,
 385                   char *data,
 386                   int dlen)
 387 {
 388     struct alias_link *pna_links;
 389     u_short msg_id, msg_len;
 390     char    *work;
 391     u_short alias_port, port;
 392     struct  tcphdr *tc;
 393
 394     work = data;
 395     work += 5;
 396     while (work + 4 < data + dlen) {
 397         memcpy(&msg_id, work, 2);
 398         work += 2;
 399         memcpy(&msg_len, work, 2);
 400         work += 2;
 401         if (ntohs(msg_id) == 0) {
 402             /* end of options */
 403             return 0;
 404         }
 405         if ((ntohs(msg_id) == 1) || (ntohs(msg_id) == 7)) {
 406             memcpy(&port, work, 2);
 407             pna_links = FindUdpTcpOut(pip->ip_src, GetDestAddress(link),
 408                                       port, 0, IPPROTO_UDP, 1);
 409             if (pna_links != NULL) {
 410 #ifndef NO_FW_PUNCH
 411                 /* Punch hole in firewall */
 412                 PunchFWHole(pna_links);
 413 #endif
 414                 tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
 415                 alias_port = GetAliasPort(pna_links);
 416                 memcpy(work, &alias_port, 2);
 417
 418                 /* Compute TCP checksum for revised packet */
 419                 tc->th_sum = 0;
 420                 tc->th_sum = TcpChecksum(pip);
 421             }
 422         }
 423         work += ntohs(msg_len);
 424     }
 425
 426     return 0;
 427 }
 428
 429 void
 430 AliasHandleRtspOut(struct ip *pip, struct alias_link *link, int maxpacketsize)
 431 {
 432     int    hlen, tlen, dlen;
 433     struct tcphdr *tc;
 434     char   *data;
 435     const  char *setup = "SETUP", *pna = "PNA", *str200 = "200";
 436     const  char *okstr = "OK", *client_port_str = "client_port";
 437     const  char *server_port_str = "server_port";
 438     int    i, parseOk;
 439
 440     tc = (struct tcphdr *)((char *)pip + (pip->ip_hl << 2));
 441     hlen = (pip->ip_hl + tc->th_off) << 2;
 442     tlen = ntohs(pip->ip_len);
 443     dlen = tlen - hlen;
 444
 445     data = (char*)pip;
 446     data += hlen;
 447
 448     /* When aliasing a client, check for the SETUP request */
 449     if ((ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_1) ||
 450       (ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_2)) {
 451
 452       if (dlen >= strlen(setup)) {
 453         if (memcmp(data, setup, strlen(setup)) == 0) {
 454             alias_rtsp_out(pip, link, data, client_port_str);
 455             return;
 456         }
 457       }
 458       if (dlen >= strlen(pna)) {
 459         if (memcmp(data, pna, strlen(pna)) == 0) {
 460             alias_pna_out(pip, link, data, dlen);
 461         }
 462       }
 463
 464     } else {
 465
 466       /* When aliasing a server, check for the 200 reply
 467          Accomodate varying number of blanks between 200 & OK */
 468
 469       if (dlen >= strlen(str200)) {
 470
 471         for (parseOk = 0, i = 0;
 472              i <= dlen - strlen(str200);
 473              i++) {
 474           if (memcmp(&data[i], str200, strlen(str200)) == 0) {
 475             parseOk = 1;
 476             break;
 477           }
 478         }
 479         if (parseOk) {
 480
 481           i += strlen(str200);        /* skip string found */
 482           while(data[i] == ' ')       /* skip blank(s) */
 483             i++;
 484
 485           if ((dlen - i) >= strlen(okstr)) {
 486
 487             if (memcmp(&data[i], okstr, strlen(okstr)) == 0)
 488               alias_rtsp_out(pip, link, data, server_port_str);
 489
 490           }
 491         }
 492       }
 493     }
 494 }