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Linux/net/netfilter/nf_conntrack_sip.c

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  1 /* SIP extension for IP connection tracking.
  2  *
  3  * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
  4  * based on RR's ip_conntrack_ftp.c and other modules.
  5  * (C) 2007 United Security Providers
  6  * (C) 2007, 2008 Patrick McHardy <kaber@trash.net>
  7  *
  8  * This program is free software; you can redistribute it and/or modify
  9  * it under the terms of the GNU General Public License version 2 as
 10  * published by the Free Software Foundation.
 11  */
 12 
 13 #include <linux/module.h>
 14 #include <linux/ctype.h>
 15 #include <linux/skbuff.h>
 16 #include <linux/inet.h>
 17 #include <linux/in.h>
 18 #include <linux/udp.h>
 19 #include <linux/tcp.h>
 20 #include <linux/netfilter.h>
 21 
 22 #include <net/netfilter/nf_conntrack.h>
 23 #include <net/netfilter/nf_conntrack_core.h>
 24 #include <net/netfilter/nf_conntrack_expect.h>
 25 #include <net/netfilter/nf_conntrack_helper.h>
 26 #include <net/netfilter/nf_conntrack_zones.h>
 27 #include <linux/netfilter/nf_conntrack_sip.h>
 28 
 29 MODULE_LICENSE("GPL");
 30 MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
 31 MODULE_DESCRIPTION("SIP connection tracking helper");
 32 MODULE_ALIAS("ip_conntrack_sip");
 33 MODULE_ALIAS_NFCT_HELPER("sip");
 34 
 35 #define MAX_PORTS       8
 36 static unsigned short ports[MAX_PORTS];
 37 static unsigned int ports_c;
 38 module_param_array(ports, ushort, &ports_c, 0400);
 39 MODULE_PARM_DESC(ports, "port numbers of SIP servers");
 40 
 41 static unsigned int sip_timeout __read_mostly = SIP_TIMEOUT;
 42 module_param(sip_timeout, uint, 0600);
 43 MODULE_PARM_DESC(sip_timeout, "timeout for the master SIP session");
 44 
 45 static int sip_direct_signalling __read_mostly = 1;
 46 module_param(sip_direct_signalling, int, 0600);
 47 MODULE_PARM_DESC(sip_direct_signalling, "expect incoming calls from registrar "
 48                                         "only (default 1)");
 49 
 50 static int sip_direct_media __read_mostly = 1;
 51 module_param(sip_direct_media, int, 0600);
 52 MODULE_PARM_DESC(sip_direct_media, "Expect Media streams between signalling "
 53                                    "endpoints only (default 1)");
 54 
 55 const struct nf_nat_sip_hooks *nf_nat_sip_hooks;
 56 EXPORT_SYMBOL_GPL(nf_nat_sip_hooks);
 57 
 58 static int string_len(const struct nf_conn *ct, const char *dptr,
 59                       const char *limit, int *shift)
 60 {
 61         int len = 0;
 62 
 63         while (dptr < limit && isalpha(*dptr)) {
 64                 dptr++;
 65                 len++;
 66         }
 67         return len;
 68 }
 69 
 70 static int digits_len(const struct nf_conn *ct, const char *dptr,
 71                       const char *limit, int *shift)
 72 {
 73         int len = 0;
 74         while (dptr < limit && isdigit(*dptr)) {
 75                 dptr++;
 76                 len++;
 77         }
 78         return len;
 79 }
 80 
 81 static int iswordc(const char c)
 82 {
 83         if (isalnum(c) || c == '!' || c == '"' || c == '%' ||
 84             (c >= '(' && c <= '/') || c == ':' || c == '<' || c == '>' ||
 85             c == '?' || (c >= '[' && c <= ']') || c == '_' || c == '`' ||
 86             c == '{' || c == '}' || c == '~')
 87                 return 1;
 88         return 0;
 89 }
 90 
 91 static int word_len(const char *dptr, const char *limit)
 92 {
 93         int len = 0;
 94         while (dptr < limit && iswordc(*dptr)) {
 95                 dptr++;
 96                 len++;
 97         }
 98         return len;
 99 }
100 
101 static int callid_len(const struct nf_conn *ct, const char *dptr,
102                       const char *limit, int *shift)
103 {
104         int len, domain_len;
105 
106         len = word_len(dptr, limit);
107         dptr += len;
108         if (!len || dptr == limit || *dptr != '@')
109                 return len;
110         dptr++;
111         len++;
112 
113         domain_len = word_len(dptr, limit);
114         if (!domain_len)
115                 return 0;
116         return len + domain_len;
117 }
118 
119 /* get media type + port length */
120 static int media_len(const struct nf_conn *ct, const char *dptr,
121                      const char *limit, int *shift)
122 {
123         int len = string_len(ct, dptr, limit, shift);
124 
125         dptr += len;
126         if (dptr >= limit || *dptr != ' ')
127                 return 0;
128         len++;
129         dptr++;
130 
131         return len + digits_len(ct, dptr, limit, shift);
132 }
133 
134 static int sip_parse_addr(const struct nf_conn *ct, const char *cp,
135                           const char **endp, union nf_inet_addr *addr,
136                           const char *limit, bool delim)
137 {
138         const char *end;
139         int ret;
140 
141         if (!ct)
142                 return 0;
143 
144         memset(addr, 0, sizeof(*addr));
145         switch (nf_ct_l3num(ct)) {
146         case AF_INET:
147                 ret = in4_pton(cp, limit - cp, (u8 *)&addr->ip, -1, &end);
148                 if (ret == 0)
149                         return 0;
150                 break;
151         case AF_INET6:
152                 if (cp < limit && *cp == '[')
153                         cp++;
154                 else if (delim)
155                         return 0;
156 
157                 ret = in6_pton(cp, limit - cp, (u8 *)&addr->ip6, -1, &end);
158                 if (ret == 0)
159                         return 0;
160 
161                 if (end < limit && *end == ']')
162                         end++;
163                 else if (delim)
164                         return 0;
165                 break;
166         default:
167                 BUG();
168         }
169 
170         if (endp)
171                 *endp = end;
172         return 1;
173 }
174 
175 /* skip ip address. returns its length. */
176 static int epaddr_len(const struct nf_conn *ct, const char *dptr,
177                       const char *limit, int *shift)
178 {
179         union nf_inet_addr addr;
180         const char *aux = dptr;
181 
182         if (!sip_parse_addr(ct, dptr, &dptr, &addr, limit, true)) {
183                 pr_debug("ip: %s parse failed.!\n", dptr);
184                 return 0;
185         }
186 
187         /* Port number */
188         if (*dptr == ':') {
189                 dptr++;
190                 dptr += digits_len(ct, dptr, limit, shift);
191         }
192         return dptr - aux;
193 }
194 
195 /* get address length, skiping user info. */
196 static int skp_epaddr_len(const struct nf_conn *ct, const char *dptr,
197                           const char *limit, int *shift)
198 {
199         const char *start = dptr;
200         int s = *shift;
201 
202         /* Search for @, but stop at the end of the line.
203          * We are inside a sip: URI, so we don't need to worry about
204          * continuation lines. */
205         while (dptr < limit &&
206                *dptr != '@' && *dptr != '\r' && *dptr != '\n') {
207                 (*shift)++;
208                 dptr++;
209         }
210 
211         if (dptr < limit && *dptr == '@') {
212                 dptr++;
213                 (*shift)++;
214         } else {
215                 dptr = start;
216                 *shift = s;
217         }
218 
219         return epaddr_len(ct, dptr, limit, shift);
220 }
221 
222 /* Parse a SIP request line of the form:
223  *
224  * Request-Line = Method SP Request-URI SP SIP-Version CRLF
225  *
226  * and return the offset and length of the address contained in the Request-URI.
227  */
228 int ct_sip_parse_request(const struct nf_conn *ct,
229                          const char *dptr, unsigned int datalen,
230                          unsigned int *matchoff, unsigned int *matchlen,
231                          union nf_inet_addr *addr, __be16 *port)
232 {
233         const char *start = dptr, *limit = dptr + datalen, *end;
234         unsigned int mlen;
235         unsigned int p;
236         int shift = 0;
237 
238         /* Skip method and following whitespace */
239         mlen = string_len(ct, dptr, limit, NULL);
240         if (!mlen)
241                 return 0;
242         dptr += mlen;
243         if (++dptr >= limit)
244                 return 0;
245 
246         /* Find SIP URI */
247         for (; dptr < limit - strlen("sip:"); dptr++) {
248                 if (*dptr == '\r' || *dptr == '\n')
249                         return -1;
250                 if (strncasecmp(dptr, "sip:", strlen("sip:")) == 0) {
251                         dptr += strlen("sip:");
252                         break;
253                 }
254         }
255         if (!skp_epaddr_len(ct, dptr, limit, &shift))
256                 return 0;
257         dptr += shift;
258 
259         if (!sip_parse_addr(ct, dptr, &end, addr, limit, true))
260                 return -1;
261         if (end < limit && *end == ':') {
262                 end++;
263                 p = simple_strtoul(end, (char **)&end, 10);
264                 if (p < 1024 || p > 65535)
265                         return -1;
266                 *port = htons(p);
267         } else
268                 *port = htons(SIP_PORT);
269 
270         if (end == dptr)
271                 return 0;
272         *matchoff = dptr - start;
273         *matchlen = end - dptr;
274         return 1;
275 }
276 EXPORT_SYMBOL_GPL(ct_sip_parse_request);
277 
278 /* SIP header parsing: SIP headers are located at the beginning of a line, but
279  * may span several lines, in which case the continuation lines begin with a
280  * whitespace character. RFC 2543 allows lines to be terminated with CR, LF or
281  * CRLF, RFC 3261 allows only CRLF, we support both.
282  *
283  * Headers are followed by (optionally) whitespace, a colon, again (optionally)
284  * whitespace and the values. Whitespace in this context means any amount of
285  * tabs, spaces and continuation lines, which are treated as a single whitespace
286  * character.
287  *
288  * Some headers may appear multiple times. A comma separated list of values is
289  * equivalent to multiple headers.
290  */
291 static const struct sip_header ct_sip_hdrs[] = {
292         [SIP_HDR_CSEQ]                  = SIP_HDR("CSeq", NULL, NULL, digits_len),
293         [SIP_HDR_FROM]                  = SIP_HDR("From", "f", "sip:", skp_epaddr_len),
294         [SIP_HDR_TO]                    = SIP_HDR("To", "t", "sip:", skp_epaddr_len),
295         [SIP_HDR_CONTACT]               = SIP_HDR("Contact", "m", "sip:", skp_epaddr_len),
296         [SIP_HDR_VIA_UDP]               = SIP_HDR("Via", "v", "UDP ", epaddr_len),
297         [SIP_HDR_VIA_TCP]               = SIP_HDR("Via", "v", "TCP ", epaddr_len),
298         [SIP_HDR_EXPIRES]               = SIP_HDR("Expires", NULL, NULL, digits_len),
299         [SIP_HDR_CONTENT_LENGTH]        = SIP_HDR("Content-Length", "l", NULL, digits_len),
300         [SIP_HDR_CALL_ID]               = SIP_HDR("Call-Id", "i", NULL, callid_len),
301 };
302 
303 static const char *sip_follow_continuation(const char *dptr, const char *limit)
304 {
305         /* Walk past newline */
306         if (++dptr >= limit)
307                 return NULL;
308 
309         /* Skip '\n' in CR LF */
310         if (*(dptr - 1) == '\r' && *dptr == '\n') {
311                 if (++dptr >= limit)
312                         return NULL;
313         }
314 
315         /* Continuation line? */
316         if (*dptr != ' ' && *dptr != '\t')
317                 return NULL;
318 
319         /* skip leading whitespace */
320         for (; dptr < limit; dptr++) {
321                 if (*dptr != ' ' && *dptr != '\t')
322                         break;
323         }
324         return dptr;
325 }
326 
327 static const char *sip_skip_whitespace(const char *dptr, const char *limit)
328 {
329         for (; dptr < limit; dptr++) {
330                 if (*dptr == ' ')
331                         continue;
332                 if (*dptr != '\r' && *dptr != '\n')
333                         break;
334                 dptr = sip_follow_continuation(dptr, limit);
335                 if (dptr == NULL)
336                         return NULL;
337         }
338         return dptr;
339 }
340 
341 /* Search within a SIP header value, dealing with continuation lines */
342 static const char *ct_sip_header_search(const char *dptr, const char *limit,
343                                         const char *needle, unsigned int len)
344 {
345         for (limit -= len; dptr < limit; dptr++) {
346                 if (*dptr == '\r' || *dptr == '\n') {
347                         dptr = sip_follow_continuation(dptr, limit);
348                         if (dptr == NULL)
349                                 break;
350                         continue;
351                 }
352 
353                 if (strncasecmp(dptr, needle, len) == 0)
354                         return dptr;
355         }
356         return NULL;
357 }
358 
359 int ct_sip_get_header(const struct nf_conn *ct, const char *dptr,
360                       unsigned int dataoff, unsigned int datalen,
361                       enum sip_header_types type,
362                       unsigned int *matchoff, unsigned int *matchlen)
363 {
364         const struct sip_header *hdr = &ct_sip_hdrs[type];
365         const char *start = dptr, *limit = dptr + datalen;
366         int shift = 0;
367 
368         for (dptr += dataoff; dptr < limit; dptr++) {
369                 /* Find beginning of line */
370                 if (*dptr != '\r' && *dptr != '\n')
371                         continue;
372                 if (++dptr >= limit)
373                         break;
374                 if (*(dptr - 1) == '\r' && *dptr == '\n') {
375                         if (++dptr >= limit)
376                                 break;
377                 }
378 
379                 /* Skip continuation lines */
380                 if (*dptr == ' ' || *dptr == '\t')
381                         continue;
382 
383                 /* Find header. Compact headers must be followed by a
384                  * non-alphabetic character to avoid mismatches. */
385                 if (limit - dptr >= hdr->len &&
386                     strncasecmp(dptr, hdr->name, hdr->len) == 0)
387                         dptr += hdr->len;
388                 else if (hdr->cname && limit - dptr >= hdr->clen + 1 &&
389                          strncasecmp(dptr, hdr->cname, hdr->clen) == 0 &&
390                          !isalpha(*(dptr + hdr->clen)))
391                         dptr += hdr->clen;
392                 else
393                         continue;
394 
395                 /* Find and skip colon */
396                 dptr = sip_skip_whitespace(dptr, limit);
397                 if (dptr == NULL)
398                         break;
399                 if (*dptr != ':' || ++dptr >= limit)
400                         break;
401 
402                 /* Skip whitespace after colon */
403                 dptr = sip_skip_whitespace(dptr, limit);
404                 if (dptr == NULL)
405                         break;
406 
407                 *matchoff = dptr - start;
408                 if (hdr->search) {
409                         dptr = ct_sip_header_search(dptr, limit, hdr->search,
410                                                     hdr->slen);
411                         if (!dptr)
412                                 return -1;
413                         dptr += hdr->slen;
414                 }
415 
416                 *matchlen = hdr->match_len(ct, dptr, limit, &shift);
417                 if (!*matchlen)
418                         return -1;
419                 *matchoff = dptr - start + shift;
420                 return 1;
421         }
422         return 0;
423 }
424 EXPORT_SYMBOL_GPL(ct_sip_get_header);
425 
426 /* Get next header field in a list of comma separated values */
427 static int ct_sip_next_header(const struct nf_conn *ct, const char *dptr,
428                               unsigned int dataoff, unsigned int datalen,
429                               enum sip_header_types type,
430                               unsigned int *matchoff, unsigned int *matchlen)
431 {
432         const struct sip_header *hdr = &ct_sip_hdrs[type];
433         const char *start = dptr, *limit = dptr + datalen;
434         int shift = 0;
435 
436         dptr += dataoff;
437 
438         dptr = ct_sip_header_search(dptr, limit, ",", strlen(","));
439         if (!dptr)
440                 return 0;
441 
442         dptr = ct_sip_header_search(dptr, limit, hdr->search, hdr->slen);
443         if (!dptr)
444                 return 0;
445         dptr += hdr->slen;
446 
447         *matchoff = dptr - start;
448         *matchlen = hdr->match_len(ct, dptr, limit, &shift);
449         if (!*matchlen)
450                 return -1;
451         *matchoff += shift;
452         return 1;
453 }
454 
455 /* Walk through headers until a parsable one is found or no header of the
456  * given type is left. */
457 static int ct_sip_walk_headers(const struct nf_conn *ct, const char *dptr,
458                                unsigned int dataoff, unsigned int datalen,
459                                enum sip_header_types type, int *in_header,
460                                unsigned int *matchoff, unsigned int *matchlen)
461 {
462         int ret;
463 
464         if (in_header && *in_header) {
465                 while (1) {
466                         ret = ct_sip_next_header(ct, dptr, dataoff, datalen,
467                                                  type, matchoff, matchlen);
468                         if (ret > 0)
469                                 return ret;
470                         if (ret == 0)
471                                 break;
472                         dataoff += *matchoff;
473                 }
474                 *in_header = 0;
475         }
476 
477         while (1) {
478                 ret = ct_sip_get_header(ct, dptr, dataoff, datalen,
479                                         type, matchoff, matchlen);
480                 if (ret > 0)
481                         break;
482                 if (ret == 0)
483                         return ret;
484                 dataoff += *matchoff;
485         }
486 
487         if (in_header)
488                 *in_header = 1;
489         return 1;
490 }
491 
492 /* Locate a SIP header, parse the URI and return the offset and length of
493  * the address as well as the address and port themselves. A stream of
494  * headers can be parsed by handing in a non-NULL datalen and in_header
495  * pointer.
496  */
497 int ct_sip_parse_header_uri(const struct nf_conn *ct, const char *dptr,
498                             unsigned int *dataoff, unsigned int datalen,
499                             enum sip_header_types type, int *in_header,
500                             unsigned int *matchoff, unsigned int *matchlen,
501                             union nf_inet_addr *addr, __be16 *port)
502 {
503         const char *c, *limit = dptr + datalen;
504         unsigned int p;
505         int ret;
506 
507         ret = ct_sip_walk_headers(ct, dptr, dataoff ? *dataoff : 0, datalen,
508                                   type, in_header, matchoff, matchlen);
509         WARN_ON(ret < 0);
510         if (ret == 0)
511                 return ret;
512 
513         if (!sip_parse_addr(ct, dptr + *matchoff, &c, addr, limit, true))
514                 return -1;
515         if (*c == ':') {
516                 c++;
517                 p = simple_strtoul(c, (char **)&c, 10);
518                 if (p < 1024 || p > 65535)
519                         return -1;
520                 *port = htons(p);
521         } else
522                 *port = htons(SIP_PORT);
523 
524         if (dataoff)
525                 *dataoff = c - dptr;
526         return 1;
527 }
528 EXPORT_SYMBOL_GPL(ct_sip_parse_header_uri);
529 
530 static int ct_sip_parse_param(const struct nf_conn *ct, const char *dptr,
531                               unsigned int dataoff, unsigned int datalen,
532                               const char *name,
533                               unsigned int *matchoff, unsigned int *matchlen)
534 {
535         const char *limit = dptr + datalen;
536         const char *start;
537         const char *end;
538 
539         limit = ct_sip_header_search(dptr + dataoff, limit, ",", strlen(","));
540         if (!limit)
541                 limit = dptr + datalen;
542 
543         start = ct_sip_header_search(dptr + dataoff, limit, name, strlen(name));
544         if (!start)
545                 return 0;
546         start += strlen(name);
547 
548         end = ct_sip_header_search(start, limit, ";", strlen(";"));
549         if (!end)
550                 end = limit;
551 
552         *matchoff = start - dptr;
553         *matchlen = end - start;
554         return 1;
555 }
556 
557 /* Parse address from header parameter and return address, offset and length */
558 int ct_sip_parse_address_param(const struct nf_conn *ct, const char *dptr,
559                                unsigned int dataoff, unsigned int datalen,
560                                const char *name,
561                                unsigned int *matchoff, unsigned int *matchlen,
562                                union nf_inet_addr *addr, bool delim)
563 {
564         const char *limit = dptr + datalen;
565         const char *start, *end;
566 
567         limit = ct_sip_header_search(dptr + dataoff, limit, ",", strlen(","));
568         if (!limit)
569                 limit = dptr + datalen;
570 
571         start = ct_sip_header_search(dptr + dataoff, limit, name, strlen(name));
572         if (!start)
573                 return 0;
574 
575         start += strlen(name);
576         if (!sip_parse_addr(ct, start, &end, addr, limit, delim))
577                 return 0;
578         *matchoff = start - dptr;
579         *matchlen = end - start;
580         return 1;
581 }
582 EXPORT_SYMBOL_GPL(ct_sip_parse_address_param);
583 
584 /* Parse numerical header parameter and return value, offset and length */
585 int ct_sip_parse_numerical_param(const struct nf_conn *ct, const char *dptr,
586                                  unsigned int dataoff, unsigned int datalen,
587                                  const char *name,
588                                  unsigned int *matchoff, unsigned int *matchlen,
589                                  unsigned int *val)
590 {
591         const char *limit = dptr + datalen;
592         const char *start;
593         char *end;
594 
595         limit = ct_sip_header_search(dptr + dataoff, limit, ",", strlen(","));
596         if (!limit)
597                 limit = dptr + datalen;
598 
599         start = ct_sip_header_search(dptr + dataoff, limit, name, strlen(name));
600         if (!start)
601                 return 0;
602 
603         start += strlen(name);
604         *val = simple_strtoul(start, &end, 0);
605         if (start == end)
606                 return 0;
607         if (matchoff && matchlen) {
608                 *matchoff = start - dptr;
609                 *matchlen = end - start;
610         }
611         return 1;
612 }
613 EXPORT_SYMBOL_GPL(ct_sip_parse_numerical_param);
614 
615 static int ct_sip_parse_transport(struct nf_conn *ct, const char *dptr,
616                                   unsigned int dataoff, unsigned int datalen,
617                                   u8 *proto)
618 {
619         unsigned int matchoff, matchlen;
620 
621         if (ct_sip_parse_param(ct, dptr, dataoff, datalen, "transport=",
622                                &matchoff, &matchlen)) {
623                 if (!strncasecmp(dptr + matchoff, "TCP", strlen("TCP")))
624                         *proto = IPPROTO_TCP;
625                 else if (!strncasecmp(dptr + matchoff, "UDP", strlen("UDP")))
626                         *proto = IPPROTO_UDP;
627                 else
628                         return 0;
629 
630                 if (*proto != nf_ct_protonum(ct))
631                         return 0;
632         } else
633                 *proto = nf_ct_protonum(ct);
634 
635         return 1;
636 }
637 
638 static int sdp_parse_addr(const struct nf_conn *ct, const char *cp,
639                           const char **endp, union nf_inet_addr *addr,
640                           const char *limit)
641 {
642         const char *end;
643         int ret;
644 
645         memset(addr, 0, sizeof(*addr));
646         switch (nf_ct_l3num(ct)) {
647         case AF_INET:
648                 ret = in4_pton(cp, limit - cp, (u8 *)&addr->ip, -1, &end);
649                 break;
650         case AF_INET6:
651                 ret = in6_pton(cp, limit - cp, (u8 *)&addr->ip6, -1, &end);
652                 break;
653         default:
654                 BUG();
655         }
656 
657         if (ret == 0)
658                 return 0;
659         if (endp)
660                 *endp = end;
661         return 1;
662 }
663 
664 /* skip ip address. returns its length. */
665 static int sdp_addr_len(const struct nf_conn *ct, const char *dptr,
666                         const char *limit, int *shift)
667 {
668         union nf_inet_addr addr;
669         const char *aux = dptr;
670 
671         if (!sdp_parse_addr(ct, dptr, &dptr, &addr, limit)) {
672                 pr_debug("ip: %s parse failed.!\n", dptr);
673                 return 0;
674         }
675 
676         return dptr - aux;
677 }
678 
679 /* SDP header parsing: a SDP session description contains an ordered set of
680  * headers, starting with a section containing general session parameters,
681  * optionally followed by multiple media descriptions.
682  *
683  * SDP headers always start at the beginning of a line. According to RFC 2327:
684  * "The sequence CRLF (0x0d0a) is used to end a record, although parsers should
685  * be tolerant and also accept records terminated with a single newline
686  * character". We handle both cases.
687  */
688 static const struct sip_header ct_sdp_hdrs_v4[] = {
689         [SDP_HDR_VERSION]       = SDP_HDR("v=", NULL, digits_len),
690         [SDP_HDR_OWNER]         = SDP_HDR("o=", "IN IP4 ", sdp_addr_len),
691         [SDP_HDR_CONNECTION]    = SDP_HDR("c=", "IN IP4 ", sdp_addr_len),
692         [SDP_HDR_MEDIA]         = SDP_HDR("m=", NULL, media_len),
693 };
694 
695 static const struct sip_header ct_sdp_hdrs_v6[] = {
696         [SDP_HDR_VERSION]       = SDP_HDR("v=", NULL, digits_len),
697         [SDP_HDR_OWNER]         = SDP_HDR("o=", "IN IP6 ", sdp_addr_len),
698         [SDP_HDR_CONNECTION]    = SDP_HDR("c=", "IN IP6 ", sdp_addr_len),
699         [SDP_HDR_MEDIA]         = SDP_HDR("m=", NULL, media_len),
700 };
701 
702 /* Linear string search within SDP header values */
703 static const char *ct_sdp_header_search(const char *dptr, const char *limit,
704                                         const char *needle, unsigned int len)
705 {
706         for (limit -= len; dptr < limit; dptr++) {
707                 if (*dptr == '\r' || *dptr == '\n')
708                         break;
709                 if (strncmp(dptr, needle, len) == 0)
710                         return dptr;
711         }
712         return NULL;
713 }
714 
715 /* Locate a SDP header (optionally a substring within the header value),
716  * optionally stopping at the first occurrence of the term header, parse
717  * it and return the offset and length of the data we're interested in.
718  */
719 int ct_sip_get_sdp_header(const struct nf_conn *ct, const char *dptr,
720                           unsigned int dataoff, unsigned int datalen,
721                           enum sdp_header_types type,
722                           enum sdp_header_types term,
723                           unsigned int *matchoff, unsigned int *matchlen)
724 {
725         const struct sip_header *hdrs, *hdr, *thdr;
726         const char *start = dptr, *limit = dptr + datalen;
727         int shift = 0;
728 
729         hdrs = nf_ct_l3num(ct) == NFPROTO_IPV4 ? ct_sdp_hdrs_v4 : ct_sdp_hdrs_v6;
730         hdr = &hdrs[type];
731         thdr = &hdrs[term];
732 
733         for (dptr += dataoff; dptr < limit; dptr++) {
734                 /* Find beginning of line */
735                 if (*dptr != '\r' && *dptr != '\n')
736                         continue;
737                 if (++dptr >= limit)
738                         break;
739                 if (*(dptr - 1) == '\r' && *dptr == '\n') {
740                         if (++dptr >= limit)
741                                 break;
742                 }
743 
744                 if (term != SDP_HDR_UNSPEC &&
745                     limit - dptr >= thdr->len &&
746                     strncasecmp(dptr, thdr->name, thdr->len) == 0)
747                         break;
748                 else if (limit - dptr >= hdr->len &&
749                          strncasecmp(dptr, hdr->name, hdr->len) == 0)
750                         dptr += hdr->len;
751                 else
752                         continue;
753 
754                 *matchoff = dptr - start;
755                 if (hdr->search) {
756                         dptr = ct_sdp_header_search(dptr, limit, hdr->search,
757                                                     hdr->slen);
758                         if (!dptr)
759                                 return -1;
760                         dptr += hdr->slen;
761                 }
762 
763                 *matchlen = hdr->match_len(ct, dptr, limit, &shift);
764                 if (!*matchlen)
765                         return -1;
766                 *matchoff = dptr - start + shift;
767                 return 1;
768         }
769         return 0;
770 }
771 EXPORT_SYMBOL_GPL(ct_sip_get_sdp_header);
772 
773 static int ct_sip_parse_sdp_addr(const struct nf_conn *ct, const char *dptr,
774                                  unsigned int dataoff, unsigned int datalen,
775                                  enum sdp_header_types type,
776                                  enum sdp_header_types term,
777                                  unsigned int *matchoff, unsigned int *matchlen,
778                                  union nf_inet_addr *addr)
779 {
780         int ret;
781 
782         ret = ct_sip_get_sdp_header(ct, dptr, dataoff, datalen, type, term,
783                                     matchoff, matchlen);
784         if (ret <= 0)
785                 return ret;
786 
787         if (!sdp_parse_addr(ct, dptr + *matchoff, NULL, addr,
788                             dptr + *matchoff + *matchlen))
789                 return -1;
790         return 1;
791 }
792 
793 static int refresh_signalling_expectation(struct nf_conn *ct,
794                                           union nf_inet_addr *addr,
795                                           u8 proto, __be16 port,
796                                           unsigned int expires)
797 {
798         struct nf_conn_help *help = nfct_help(ct);
799         struct nf_conntrack_expect *exp;
800         struct hlist_node *next;
801         int found = 0;
802 
803         spin_lock_bh(&nf_conntrack_expect_lock);
804         hlist_for_each_entry_safe(exp, next, &help->expectations, lnode) {
805                 if (exp->class != SIP_EXPECT_SIGNALLING ||
806                     !nf_inet_addr_cmp(&exp->tuple.dst.u3, addr) ||
807                     exp->tuple.dst.protonum != proto ||
808                     exp->tuple.dst.u.udp.port != port)
809                         continue;
810                 if (!del_timer(&exp->timeout))
811                         continue;
812                 exp->flags &= ~NF_CT_EXPECT_INACTIVE;
813                 exp->timeout.expires = jiffies + expires * HZ;
814                 add_timer(&exp->timeout);
815                 found = 1;
816                 break;
817         }
818         spin_unlock_bh(&nf_conntrack_expect_lock);
819         return found;
820 }
821 
822 static void flush_expectations(struct nf_conn *ct, bool media)
823 {
824         struct nf_conn_help *help = nfct_help(ct);
825         struct nf_conntrack_expect *exp;
826         struct hlist_node *next;
827 
828         spin_lock_bh(&nf_conntrack_expect_lock);
829         hlist_for_each_entry_safe(exp, next, &help->expectations, lnode) {
830                 if ((exp->class != SIP_EXPECT_SIGNALLING) ^ media)
831                         continue;
832                 if (!del_timer(&exp->timeout))
833                         continue;
834                 nf_ct_unlink_expect(exp);
835                 nf_ct_expect_put(exp);
836                 if (!media)
837                         break;
838         }
839         spin_unlock_bh(&nf_conntrack_expect_lock);
840 }
841 
842 static int set_expected_rtp_rtcp(struct sk_buff *skb, unsigned int protoff,
843                                  unsigned int dataoff,
844                                  const char **dptr, unsigned int *datalen,
845                                  union nf_inet_addr *daddr, __be16 port,
846                                  enum sip_expectation_classes class,
847                                  unsigned int mediaoff, unsigned int medialen)
848 {
849         struct nf_conntrack_expect *exp, *rtp_exp, *rtcp_exp;
850         enum ip_conntrack_info ctinfo;
851         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
852         struct net *net = nf_ct_net(ct);
853         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
854         union nf_inet_addr *saddr;
855         struct nf_conntrack_tuple tuple;
856         int direct_rtp = 0, skip_expect = 0, ret = NF_DROP;
857         u_int16_t base_port;
858         __be16 rtp_port, rtcp_port;
859         const struct nf_nat_sip_hooks *hooks;
860 
861         saddr = NULL;
862         if (sip_direct_media) {
863                 if (!nf_inet_addr_cmp(daddr, &ct->tuplehash[dir].tuple.src.u3))
864                         return NF_ACCEPT;
865                 saddr = &ct->tuplehash[!dir].tuple.src.u3;
866         }
867 
868         /* We need to check whether the registration exists before attempting
869          * to register it since we can see the same media description multiple
870          * times on different connections in case multiple endpoints receive
871          * the same call.
872          *
873          * RTP optimization: if we find a matching media channel expectation
874          * and both the expectation and this connection are SNATed, we assume
875          * both sides can reach each other directly and use the final
876          * destination address from the expectation. We still need to keep
877          * the NATed expectations for media that might arrive from the
878          * outside, and additionally need to expect the direct RTP stream
879          * in case it passes through us even without NAT.
880          */
881         memset(&tuple, 0, sizeof(tuple));
882         if (saddr)
883                 tuple.src.u3 = *saddr;
884         tuple.src.l3num         = nf_ct_l3num(ct);
885         tuple.dst.protonum      = IPPROTO_UDP;
886         tuple.dst.u3            = *daddr;
887         tuple.dst.u.udp.port    = port;
888 
889         rcu_read_lock();
890         do {
891                 exp = __nf_ct_expect_find(net, nf_ct_zone(ct), &tuple);
892 
893                 if (!exp || exp->master == ct ||
894                     nfct_help(exp->master)->helper != nfct_help(ct)->helper ||
895                     exp->class != class)
896                         break;
897 #ifdef CONFIG_NF_NAT_NEEDED
898                 if (!direct_rtp &&
899                     (!nf_inet_addr_cmp(&exp->saved_addr, &exp->tuple.dst.u3) ||
900                      exp->saved_proto.udp.port != exp->tuple.dst.u.udp.port) &&
901                     ct->status & IPS_NAT_MASK) {
902                         *daddr                  = exp->saved_addr;
903                         tuple.dst.u3            = exp->saved_addr;
904                         tuple.dst.u.udp.port    = exp->saved_proto.udp.port;
905                         direct_rtp = 1;
906                 } else
907 #endif
908                         skip_expect = 1;
909         } while (!skip_expect);
910 
911         base_port = ntohs(tuple.dst.u.udp.port) & ~1;
912         rtp_port = htons(base_port);
913         rtcp_port = htons(base_port + 1);
914 
915         if (direct_rtp) {
916                 hooks = rcu_dereference(nf_nat_sip_hooks);
917                 if (hooks &&
918                     !hooks->sdp_port(skb, protoff, dataoff, dptr, datalen,
919                                      mediaoff, medialen, ntohs(rtp_port)))
920                         goto err1;
921         }
922 
923         if (skip_expect) {
924                 rcu_read_unlock();
925                 return NF_ACCEPT;
926         }
927 
928         rtp_exp = nf_ct_expect_alloc(ct);
929         if (rtp_exp == NULL)
930                 goto err1;
931         nf_ct_expect_init(rtp_exp, class, nf_ct_l3num(ct), saddr, daddr,
932                           IPPROTO_UDP, NULL, &rtp_port);
933 
934         rtcp_exp = nf_ct_expect_alloc(ct);
935         if (rtcp_exp == NULL)
936                 goto err2;
937         nf_ct_expect_init(rtcp_exp, class, nf_ct_l3num(ct), saddr, daddr,
938                           IPPROTO_UDP, NULL, &rtcp_port);
939 
940         hooks = rcu_dereference(nf_nat_sip_hooks);
941         if (hooks && ct->status & IPS_NAT_MASK && !direct_rtp)
942                 ret = hooks->sdp_media(skb, protoff, dataoff, dptr,
943                                        datalen, rtp_exp, rtcp_exp,
944                                        mediaoff, medialen, daddr);
945         else {
946                 if (nf_ct_expect_related(rtp_exp) == 0) {
947                         if (nf_ct_expect_related(rtcp_exp) != 0)
948                                 nf_ct_unexpect_related(rtp_exp);
949                         else
950                                 ret = NF_ACCEPT;
951                 }
952         }
953         nf_ct_expect_put(rtcp_exp);
954 err2:
955         nf_ct_expect_put(rtp_exp);
956 err1:
957         rcu_read_unlock();
958         return ret;
959 }
960 
961 static const struct sdp_media_type sdp_media_types[] = {
962         SDP_MEDIA_TYPE("audio ", SIP_EXPECT_AUDIO),
963         SDP_MEDIA_TYPE("video ", SIP_EXPECT_VIDEO),
964         SDP_MEDIA_TYPE("image ", SIP_EXPECT_IMAGE),
965 };
966 
967 static const struct sdp_media_type *sdp_media_type(const char *dptr,
968                                                    unsigned int matchoff,
969                                                    unsigned int matchlen)
970 {
971         const struct sdp_media_type *t;
972         unsigned int i;
973 
974         for (i = 0; i < ARRAY_SIZE(sdp_media_types); i++) {
975                 t = &sdp_media_types[i];
976                 if (matchlen < t->len ||
977                     strncmp(dptr + matchoff, t->name, t->len))
978                         continue;
979                 return t;
980         }
981         return NULL;
982 }
983 
984 static int process_sdp(struct sk_buff *skb, unsigned int protoff,
985                        unsigned int dataoff,
986                        const char **dptr, unsigned int *datalen,
987                        unsigned int cseq)
988 {
989         enum ip_conntrack_info ctinfo;
990         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
991         unsigned int matchoff, matchlen;
992         unsigned int mediaoff, medialen;
993         unsigned int sdpoff;
994         unsigned int caddr_len, maddr_len;
995         unsigned int i;
996         union nf_inet_addr caddr, maddr, rtp_addr;
997         const struct nf_nat_sip_hooks *hooks;
998         unsigned int port;
999         const struct sdp_media_type *t;
1000         int ret = NF_ACCEPT;
1001 
1002         hooks = rcu_dereference(nf_nat_sip_hooks);
1003 
1004         /* Find beginning of session description */
1005         if (ct_sip_get_sdp_header(ct, *dptr, 0, *datalen,
1006                                   SDP_HDR_VERSION, SDP_HDR_UNSPEC,
1007                                   &matchoff, &matchlen) <= 0)
1008                 return NF_ACCEPT;
1009         sdpoff = matchoff;
1010 
1011         /* The connection information is contained in the session description
1012          * and/or once per media description. The first media description marks
1013          * the end of the session description. */
1014         caddr_len = 0;
1015         if (ct_sip_parse_sdp_addr(ct, *dptr, sdpoff, *datalen,
1016                                   SDP_HDR_CONNECTION, SDP_HDR_MEDIA,
1017                                   &matchoff, &matchlen, &caddr) > 0)
1018                 caddr_len = matchlen;
1019 
1020         mediaoff = sdpoff;
1021         for (i = 0; i < ARRAY_SIZE(sdp_media_types); ) {
1022                 if (ct_sip_get_sdp_header(ct, *dptr, mediaoff, *datalen,
1023                                           SDP_HDR_MEDIA, SDP_HDR_UNSPEC,
1024                                           &mediaoff, &medialen) <= 0)
1025                         break;
1026 
1027                 /* Get media type and port number. A media port value of zero
1028                  * indicates an inactive stream. */
1029                 t = sdp_media_type(*dptr, mediaoff, medialen);
1030                 if (!t) {
1031                         mediaoff += medialen;
1032                         continue;
1033                 }
1034                 mediaoff += t->len;
1035                 medialen -= t->len;
1036 
1037                 port = simple_strtoul(*dptr + mediaoff, NULL, 10);
1038                 if (port == 0)
1039                         continue;
1040                 if (port < 1024 || port > 65535) {
1041                         nf_ct_helper_log(skb, ct, "wrong port %u", port);
1042                         return NF_DROP;
1043                 }
1044 
1045                 /* The media description overrides the session description. */
1046                 maddr_len = 0;
1047                 if (ct_sip_parse_sdp_addr(ct, *dptr, mediaoff, *datalen,
1048                                           SDP_HDR_CONNECTION, SDP_HDR_MEDIA,
1049                                           &matchoff, &matchlen, &maddr) > 0) {
1050                         maddr_len = matchlen;
1051                         memcpy(&rtp_addr, &maddr, sizeof(rtp_addr));
1052                 } else if (caddr_len)
1053                         memcpy(&rtp_addr, &caddr, sizeof(rtp_addr));
1054                 else {
1055                         nf_ct_helper_log(skb, ct, "cannot parse SDP message");
1056                         return NF_DROP;
1057                 }
1058 
1059                 ret = set_expected_rtp_rtcp(skb, protoff, dataoff,
1060                                             dptr, datalen,
1061                                             &rtp_addr, htons(port), t->class,
1062                                             mediaoff, medialen);
1063                 if (ret != NF_ACCEPT) {
1064                         nf_ct_helper_log(skb, ct,
1065                                          "cannot add expectation for voice");
1066                         return ret;
1067                 }
1068 
1069                 /* Update media connection address if present */
1070                 if (maddr_len && hooks && ct->status & IPS_NAT_MASK) {
1071                         ret = hooks->sdp_addr(skb, protoff, dataoff,
1072                                               dptr, datalen, mediaoff,
1073                                               SDP_HDR_CONNECTION,
1074                                               SDP_HDR_MEDIA,
1075                                               &rtp_addr);
1076                         if (ret != NF_ACCEPT) {
1077                                 nf_ct_helper_log(skb, ct, "cannot mangle SDP");
1078                                 return ret;
1079                         }
1080                 }
1081                 i++;
1082         }
1083 
1084         /* Update session connection and owner addresses */
1085         hooks = rcu_dereference(nf_nat_sip_hooks);
1086         if (hooks && ct->status & IPS_NAT_MASK)
1087                 ret = hooks->sdp_session(skb, protoff, dataoff,
1088                                          dptr, datalen, sdpoff,
1089                                          &rtp_addr);
1090 
1091         return ret;
1092 }
1093 static int process_invite_response(struct sk_buff *skb, unsigned int protoff,
1094                                    unsigned int dataoff,
1095                                    const char **dptr, unsigned int *datalen,
1096                                    unsigned int cseq, unsigned int code)
1097 {
1098         enum ip_conntrack_info ctinfo;
1099         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1100         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
1101 
1102         if ((code >= 100 && code <= 199) ||
1103             (code >= 200 && code <= 299))
1104                 return process_sdp(skb, protoff, dataoff, dptr, datalen, cseq);
1105         else if (ct_sip_info->invite_cseq == cseq)
1106                 flush_expectations(ct, true);
1107         return NF_ACCEPT;
1108 }
1109 
1110 static int process_update_response(struct sk_buff *skb, unsigned int protoff,
1111                                    unsigned int dataoff,
1112                                    const char **dptr, unsigned int *datalen,
1113                                    unsigned int cseq, unsigned int code)
1114 {
1115         enum ip_conntrack_info ctinfo;
1116         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1117         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
1118 
1119         if ((code >= 100 && code <= 199) ||
1120             (code >= 200 && code <= 299))
1121                 return process_sdp(skb, protoff, dataoff, dptr, datalen, cseq);
1122         else if (ct_sip_info->invite_cseq == cseq)
1123                 flush_expectations(ct, true);
1124         return NF_ACCEPT;
1125 }
1126 
1127 static int process_prack_response(struct sk_buff *skb, unsigned int protoff,
1128                                   unsigned int dataoff,
1129                                   const char **dptr, unsigned int *datalen,
1130                                   unsigned int cseq, unsigned int code)
1131 {
1132         enum ip_conntrack_info ctinfo;
1133         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1134         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
1135 
1136         if ((code >= 100 && code <= 199) ||
1137             (code >= 200 && code <= 299))
1138                 return process_sdp(skb, protoff, dataoff, dptr, datalen, cseq);
1139         else if (ct_sip_info->invite_cseq == cseq)
1140                 flush_expectations(ct, true);
1141         return NF_ACCEPT;
1142 }
1143 
1144 static int process_invite_request(struct sk_buff *skb, unsigned int protoff,
1145                                   unsigned int dataoff,
1146                                   const char **dptr, unsigned int *datalen,
1147                                   unsigned int cseq)
1148 {
1149         enum ip_conntrack_info ctinfo;
1150         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1151         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
1152         unsigned int ret;
1153 
1154         flush_expectations(ct, true);
1155         ret = process_sdp(skb, protoff, dataoff, dptr, datalen, cseq);
1156         if (ret == NF_ACCEPT)
1157                 ct_sip_info->invite_cseq = cseq;
1158         return ret;
1159 }
1160 
1161 static int process_bye_request(struct sk_buff *skb, unsigned int protoff,
1162                                unsigned int dataoff,
1163                                const char **dptr, unsigned int *datalen,
1164                                unsigned int cseq)
1165 {
1166         enum ip_conntrack_info ctinfo;
1167         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1168 
1169         flush_expectations(ct, true);
1170         return NF_ACCEPT;
1171 }
1172 
1173 /* Parse a REGISTER request and create a permanent expectation for incoming
1174  * signalling connections. The expectation is marked inactive and is activated
1175  * when receiving a response indicating success from the registrar.
1176  */
1177 static int process_register_request(struct sk_buff *skb, unsigned int protoff,
1178                                     unsigned int dataoff,
1179                                     const char **dptr, unsigned int *datalen,
1180                                     unsigned int cseq)
1181 {
1182         enum ip_conntrack_info ctinfo;
1183         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1184         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
1185         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
1186         unsigned int matchoff, matchlen;
1187         struct nf_conntrack_expect *exp;
1188         union nf_inet_addr *saddr, daddr;
1189         const struct nf_nat_sip_hooks *hooks;
1190         __be16 port;
1191         u8 proto;
1192         unsigned int expires = 0;
1193         int ret;
1194 
1195         /* Expected connections can not register again. */
1196         if (ct->status & IPS_EXPECTED)
1197                 return NF_ACCEPT;
1198 
1199         /* We must check the expiration time: a value of zero signals the
1200          * registrar to release the binding. We'll remove our expectation
1201          * when receiving the new bindings in the response, but we don't
1202          * want to create new ones.
1203          *
1204          * The expiration time may be contained in Expires: header, the
1205          * Contact: header parameters or the URI parameters.
1206          */
1207         if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_EXPIRES,
1208                               &matchoff, &matchlen) > 0)
1209                 expires = simple_strtoul(*dptr + matchoff, NULL, 10);
1210 
1211         ret = ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen,
1212                                       SIP_HDR_CONTACT, NULL,
1213                                       &matchoff, &matchlen, &daddr, &port);
1214         if (ret < 0) {
1215                 nf_ct_helper_log(skb, ct, "cannot parse contact");
1216                 return NF_DROP;
1217         } else if (ret == 0)
1218                 return NF_ACCEPT;
1219 
1220         /* We don't support third-party registrations */
1221         if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3, &daddr))
1222                 return NF_ACCEPT;
1223 
1224         if (ct_sip_parse_transport(ct, *dptr, matchoff + matchlen, *datalen,
1225                                    &proto) == 0)
1226                 return NF_ACCEPT;
1227 
1228         if (ct_sip_parse_numerical_param(ct, *dptr,
1229                                          matchoff + matchlen, *datalen,
1230                                          "expires=", NULL, NULL, &expires) < 0) {
1231                 nf_ct_helper_log(skb, ct, "cannot parse expires");
1232                 return NF_DROP;
1233         }
1234 
1235         if (expires == 0) {
1236                 ret = NF_ACCEPT;
1237                 goto store_cseq;
1238         }
1239 
1240         exp = nf_ct_expect_alloc(ct);
1241         if (!exp) {
1242                 nf_ct_helper_log(skb, ct, "cannot alloc expectation");
1243                 return NF_DROP;
1244         }
1245 
1246         saddr = NULL;
1247         if (sip_direct_signalling)
1248                 saddr = &ct->tuplehash[!dir].tuple.src.u3;
1249 
1250         nf_ct_expect_init(exp, SIP_EXPECT_SIGNALLING, nf_ct_l3num(ct),
1251                           saddr, &daddr, proto, NULL, &port);
1252         exp->timeout.expires = sip_timeout * HZ;
1253         exp->helper = nfct_help(ct)->helper;
1254         exp->flags = NF_CT_EXPECT_PERMANENT | NF_CT_EXPECT_INACTIVE;
1255 
1256         hooks = rcu_dereference(nf_nat_sip_hooks);
1257         if (hooks && ct->status & IPS_NAT_MASK)
1258                 ret = hooks->expect(skb, protoff, dataoff, dptr, datalen,
1259                                     exp, matchoff, matchlen);
1260         else {
1261                 if (nf_ct_expect_related(exp) != 0) {
1262                         nf_ct_helper_log(skb, ct, "cannot add expectation");
1263                         ret = NF_DROP;
1264                 } else
1265                         ret = NF_ACCEPT;
1266         }
1267         nf_ct_expect_put(exp);
1268 
1269 store_cseq:
1270         if (ret == NF_ACCEPT)
1271                 ct_sip_info->register_cseq = cseq;
1272         return ret;
1273 }
1274 
1275 static int process_register_response(struct sk_buff *skb, unsigned int protoff,
1276                                      unsigned int dataoff,
1277                                      const char **dptr, unsigned int *datalen,
1278                                      unsigned int cseq, unsigned int code)
1279 {
1280         enum ip_conntrack_info ctinfo;
1281         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1282         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
1283         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
1284         union nf_inet_addr addr;
1285         __be16 port;
1286         u8 proto;
1287         unsigned int matchoff, matchlen, coff = 0;
1288         unsigned int expires = 0;
1289         int in_contact = 0, ret;
1290 
1291         /* According to RFC 3261, "UAs MUST NOT send a new registration until
1292          * they have received a final response from the registrar for the
1293          * previous one or the previous REGISTER request has timed out".
1294          *
1295          * However, some servers fail to detect retransmissions and send late
1296          * responses, so we store the sequence number of the last valid
1297          * request and compare it here.
1298          */
1299         if (ct_sip_info->register_cseq != cseq)
1300                 return NF_ACCEPT;
1301 
1302         if (code >= 100 && code <= 199)
1303                 return NF_ACCEPT;
1304         if (code < 200 || code > 299)
1305                 goto flush;
1306 
1307         if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_EXPIRES,
1308                               &matchoff, &matchlen) > 0)
1309                 expires = simple_strtoul(*dptr + matchoff, NULL, 10);
1310 
1311         while (1) {
1312                 unsigned int c_expires = expires;
1313 
1314                 ret = ct_sip_parse_header_uri(ct, *dptr, &coff, *datalen,
1315                                               SIP_HDR_CONTACT, &in_contact,
1316                                               &matchoff, &matchlen,
1317                                               &addr, &port);
1318                 if (ret < 0) {
1319                         nf_ct_helper_log(skb, ct, "cannot parse contact");
1320                         return NF_DROP;
1321                 } else if (ret == 0)
1322                         break;
1323 
1324                 /* We don't support third-party registrations */
1325                 if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3, &addr))
1326                         continue;
1327 
1328                 if (ct_sip_parse_transport(ct, *dptr, matchoff + matchlen,
1329                                            *datalen, &proto) == 0)
1330                         continue;
1331 
1332                 ret = ct_sip_parse_numerical_param(ct, *dptr,
1333                                                    matchoff + matchlen,
1334                                                    *datalen, "expires=",
1335                                                    NULL, NULL, &c_expires);
1336                 if (ret < 0) {
1337                         nf_ct_helper_log(skb, ct, "cannot parse expires");
1338                         return NF_DROP;
1339                 }
1340                 if (c_expires == 0)
1341                         break;
1342                 if (refresh_signalling_expectation(ct, &addr, proto, port,
1343                                                    c_expires))
1344                         return NF_ACCEPT;
1345         }
1346 
1347 flush:
1348         flush_expectations(ct, false);
1349         return NF_ACCEPT;
1350 }
1351 
1352 static const struct sip_handler sip_handlers[] = {
1353         SIP_HANDLER("INVITE", process_invite_request, process_invite_response),
1354         SIP_HANDLER("UPDATE", process_sdp, process_update_response),
1355         SIP_HANDLER("ACK", process_sdp, NULL),
1356         SIP_HANDLER("PRACK", process_sdp, process_prack_response),
1357         SIP_HANDLER("BYE", process_bye_request, NULL),
1358         SIP_HANDLER("REGISTER", process_register_request, process_register_response),
1359 };
1360 
1361 static int process_sip_response(struct sk_buff *skb, unsigned int protoff,
1362                                 unsigned int dataoff,
1363                                 const char **dptr, unsigned int *datalen)
1364 {
1365         enum ip_conntrack_info ctinfo;
1366         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1367         unsigned int matchoff, matchlen, matchend;
1368         unsigned int code, cseq, i;
1369 
1370         if (*datalen < strlen("SIP/2.0 200"))
1371                 return NF_ACCEPT;
1372         code = simple_strtoul(*dptr + strlen("SIP/2.0 "), NULL, 10);
1373         if (!code) {
1374                 nf_ct_helper_log(skb, ct, "cannot get code");
1375                 return NF_DROP;
1376         }
1377 
1378         if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CSEQ,
1379                               &matchoff, &matchlen) <= 0) {
1380                 nf_ct_helper_log(skb, ct, "cannot parse cseq");
1381                 return NF_DROP;
1382         }
1383         cseq = simple_strtoul(*dptr + matchoff, NULL, 10);
1384         if (!cseq) {
1385                 nf_ct_helper_log(skb, ct, "cannot get cseq");
1386                 return NF_DROP;
1387         }
1388         matchend = matchoff + matchlen + 1;
1389 
1390         for (i = 0; i < ARRAY_SIZE(sip_handlers); i++) {
1391                 const struct sip_handler *handler;
1392 
1393                 handler = &sip_handlers[i];
1394                 if (handler->response == NULL)
1395                         continue;
1396                 if (*datalen < matchend + handler->len ||
1397                     strncasecmp(*dptr + matchend, handler->method, handler->len))
1398                         continue;
1399                 return handler->response(skb, protoff, dataoff, dptr, datalen,
1400                                          cseq, code);
1401         }
1402         return NF_ACCEPT;
1403 }
1404 
1405 static int process_sip_request(struct sk_buff *skb, unsigned int protoff,
1406                                unsigned int dataoff,
1407                                const char **dptr, unsigned int *datalen)
1408 {
1409         enum ip_conntrack_info ctinfo;
1410         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1411         struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
1412         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
1413         unsigned int matchoff, matchlen;
1414         unsigned int cseq, i;
1415         union nf_inet_addr addr;
1416         __be16 port;
1417 
1418         /* Many Cisco IP phones use a high source port for SIP requests, but
1419          * listen for the response on port 5060.  If we are the local
1420          * router for one of these phones, save the port number from the
1421          * Via: header so that nf_nat_sip can redirect the responses to
1422          * the correct port.
1423          */
1424         if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen,
1425                                     SIP_HDR_VIA_UDP, NULL, &matchoff,
1426                                     &matchlen, &addr, &port) > 0 &&
1427             port != ct->tuplehash[dir].tuple.src.u.udp.port &&
1428             nf_inet_addr_cmp(&addr, &ct->tuplehash[dir].tuple.src.u3))
1429                 ct_sip_info->forced_dport = port;
1430 
1431         for (i = 0; i < ARRAY_SIZE(sip_handlers); i++) {
1432                 const struct sip_handler *handler;
1433 
1434                 handler = &sip_handlers[i];
1435                 if (handler->request == NULL)
1436                         continue;
1437                 if (*datalen < handler->len + 2 ||
1438                     strncasecmp(*dptr, handler->method, handler->len))
1439                         continue;
1440                 if ((*dptr)[handler->len] != ' ' ||
1441                     !isalpha((*dptr)[handler->len+1]))
1442                         continue;
1443 
1444                 if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CSEQ,
1445                                       &matchoff, &matchlen) <= 0) {
1446                         nf_ct_helper_log(skb, ct, "cannot parse cseq");
1447                         return NF_DROP;
1448                 }
1449                 cseq = simple_strtoul(*dptr + matchoff, NULL, 10);
1450                 if (!cseq) {
1451                         nf_ct_helper_log(skb, ct, "cannot get cseq");
1452                         return NF_DROP;
1453                 }
1454 
1455                 return handler->request(skb, protoff, dataoff, dptr, datalen,
1456                                         cseq);
1457         }
1458         return NF_ACCEPT;
1459 }
1460 
1461 static int process_sip_msg(struct sk_buff *skb, struct nf_conn *ct,
1462                            unsigned int protoff, unsigned int dataoff,
1463                            const char **dptr, unsigned int *datalen)
1464 {
1465         const struct nf_nat_sip_hooks *hooks;
1466         int ret;
1467 
1468         if (strncasecmp(*dptr, "SIP/2.0 ", strlen("SIP/2.0 ")) != 0)
1469                 ret = process_sip_request(skb, protoff, dataoff, dptr, datalen);
1470         else
1471                 ret = process_sip_response(skb, protoff, dataoff, dptr, datalen);
1472 
1473         if (ret == NF_ACCEPT && ct->status & IPS_NAT_MASK) {
1474                 hooks = rcu_dereference(nf_nat_sip_hooks);
1475                 if (hooks && !hooks->msg(skb, protoff, dataoff,
1476                                          dptr, datalen)) {
1477                         nf_ct_helper_log(skb, ct, "cannot NAT SIP message");
1478                         ret = NF_DROP;
1479                 }
1480         }
1481 
1482         return ret;
1483 }
1484 
1485 static int sip_help_tcp(struct sk_buff *skb, unsigned int protoff,
1486                         struct nf_conn *ct, enum ip_conntrack_info ctinfo)
1487 {
1488         struct tcphdr *th, _tcph;
1489         unsigned int dataoff, datalen;
1490         unsigned int matchoff, matchlen, clen;
1491         unsigned int msglen, origlen;
1492         const char *dptr, *end;
1493         s16 diff, tdiff = 0;
1494         int ret = NF_ACCEPT;
1495         bool term;
1496 
1497         if (ctinfo != IP_CT_ESTABLISHED &&
1498             ctinfo != IP_CT_ESTABLISHED_REPLY)
1499                 return NF_ACCEPT;
1500 
1501         /* No Data ? */
1502         th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
1503         if (th == NULL)
1504                 return NF_ACCEPT;
1505         dataoff = protoff + th->doff * 4;
1506         if (dataoff >= skb->len)
1507                 return NF_ACCEPT;
1508 
1509         nf_ct_refresh(ct, skb, sip_timeout * HZ);
1510 
1511         if (unlikely(skb_linearize(skb)))
1512                 return NF_DROP;
1513 
1514         dptr = skb->data + dataoff;
1515         datalen = skb->len - dataoff;
1516         if (datalen < strlen("SIP/2.0 200"))
1517                 return NF_ACCEPT;
1518 
1519         while (1) {
1520                 if (ct_sip_get_header(ct, dptr, 0, datalen,
1521                                       SIP_HDR_CONTENT_LENGTH,
1522                                       &matchoff, &matchlen) <= 0)
1523                         break;
1524 
1525                 clen = simple_strtoul(dptr + matchoff, (char **)&end, 10);
1526                 if (dptr + matchoff == end)
1527                         break;
1528 
1529                 term = false;
1530                 for (; end + strlen("\r\n\r\n") <= dptr + datalen; end++) {
1531                         if (end[0] == '\r' && end[1] == '\n' &&
1532                             end[2] == '\r' && end[3] == '\n') {
1533                                 term = true;
1534                                 break;
1535                         }
1536                 }
1537                 if (!term)
1538                         break;
1539                 end += strlen("\r\n\r\n") + clen;
1540 
1541                 msglen = origlen = end - dptr;
1542                 if (msglen > datalen)
1543                         return NF_ACCEPT;
1544 
1545                 ret = process_sip_msg(skb, ct, protoff, dataoff,
1546                                       &dptr, &msglen);
1547                 /* process_sip_* functions report why this packet is dropped */
1548                 if (ret != NF_ACCEPT)
1549                         break;
1550                 diff     = msglen - origlen;
1551                 tdiff   += diff;
1552 
1553                 dataoff += msglen;
1554                 dptr    += msglen;
1555                 datalen  = datalen + diff - msglen;
1556         }
1557 
1558         if (ret == NF_ACCEPT && ct->status & IPS_NAT_MASK) {
1559                 const struct nf_nat_sip_hooks *hooks;
1560 
1561                 hooks = rcu_dereference(nf_nat_sip_hooks);
1562                 if (hooks)
1563                         hooks->seq_adjust(skb, protoff, tdiff);
1564         }
1565 
1566         return ret;
1567 }
1568 
1569 static int sip_help_udp(struct sk_buff *skb, unsigned int protoff,
1570                         struct nf_conn *ct, enum ip_conntrack_info ctinfo)
1571 {
1572         unsigned int dataoff, datalen;
1573         const char *dptr;
1574 
1575         /* No Data ? */
1576         dataoff = protoff + sizeof(struct udphdr);
1577         if (dataoff >= skb->len)
1578                 return NF_ACCEPT;
1579 
1580         nf_ct_refresh(ct, skb, sip_timeout * HZ);
1581 
1582         if (unlikely(skb_linearize(skb)))
1583                 return NF_DROP;
1584 
1585         dptr = skb->data + dataoff;
1586         datalen = skb->len - dataoff;
1587         if (datalen < strlen("SIP/2.0 200"))
1588                 return NF_ACCEPT;
1589 
1590         return process_sip_msg(skb, ct, protoff, dataoff, &dptr, &datalen);
1591 }
1592 
1593 static struct nf_conntrack_helper sip[MAX_PORTS][4] __read_mostly;
1594 
1595 static const struct nf_conntrack_expect_policy sip_exp_policy[SIP_EXPECT_MAX + 1] = {
1596         [SIP_EXPECT_SIGNALLING] = {
1597                 .name           = "signalling",
1598                 .max_expected   = 1,
1599                 .timeout        = 3 * 60,
1600         },
1601         [SIP_EXPECT_AUDIO] = {
1602                 .name           = "audio",
1603                 .max_expected   = 2 * IP_CT_DIR_MAX,
1604                 .timeout        = 3 * 60,
1605         },
1606         [SIP_EXPECT_VIDEO] = {
1607                 .name           = "video",
1608                 .max_expected   = 2 * IP_CT_DIR_MAX,
1609                 .timeout        = 3 * 60,
1610         },
1611         [SIP_EXPECT_IMAGE] = {
1612                 .name           = "image",
1613                 .max_expected   = IP_CT_DIR_MAX,
1614                 .timeout        = 3 * 60,
1615         },
1616 };
1617 
1618 static void nf_conntrack_sip_fini(void)
1619 {
1620         int i, j;
1621 
1622         for (i = 0; i < ports_c; i++) {
1623                 for (j = 0; j < ARRAY_SIZE(sip[i]); j++) {
1624                         if (sip[i][j].me == NULL)
1625                                 continue;
1626                         nf_conntrack_helper_unregister(&sip[i][j]);
1627                 }
1628         }
1629 }
1630 
1631 static int __init nf_conntrack_sip_init(void)
1632 {
1633         int i, j, ret;
1634 
1635         if (ports_c == 0)
1636                 ports[ports_c++] = SIP_PORT;
1637 
1638         for (i = 0; i < ports_c; i++) {
1639                 memset(&sip[i], 0, sizeof(sip[i]));
1640 
1641                 sip[i][0].tuple.src.l3num = AF_INET;
1642                 sip[i][0].tuple.dst.protonum = IPPROTO_UDP;
1643                 sip[i][0].help = sip_help_udp;
1644                 sip[i][1].tuple.src.l3num = AF_INET;
1645                 sip[i][1].tuple.dst.protonum = IPPROTO_TCP;
1646                 sip[i][1].help = sip_help_tcp;
1647 
1648                 sip[i][2].tuple.src.l3num = AF_INET6;
1649                 sip[i][2].tuple.dst.protonum = IPPROTO_UDP;
1650                 sip[i][2].help = sip_help_udp;
1651                 sip[i][3].tuple.src.l3num = AF_INET6;
1652                 sip[i][3].tuple.dst.protonum = IPPROTO_TCP;
1653                 sip[i][3].help = sip_help_tcp;
1654 
1655                 for (j = 0; j < ARRAY_SIZE(sip[i]); j++) {
1656                         sip[i][j].data_len = sizeof(struct nf_ct_sip_master);
1657                         sip[i][j].tuple.src.u.udp.port = htons(ports[i]);
1658                         sip[i][j].expect_policy = sip_exp_policy;
1659                         sip[i][j].expect_class_max = SIP_EXPECT_MAX;
1660                         sip[i][j].me = THIS_MODULE;
1661 
1662                         if (ports[i] == SIP_PORT)
1663                                 sprintf(sip[i][j].name, "sip");
1664                         else
1665                                 sprintf(sip[i][j].name, "sip-%u", i);
1666 
1667                         pr_debug("port #%u: %u\n", i, ports[i]);
1668 
1669                         ret = nf_conntrack_helper_register(&sip[i][j]);
1670                         if (ret) {
1671                                 printk(KERN_ERR "nf_ct_sip: failed to register"
1672                                        " helper for pf: %u port: %u\n",
1673                                        sip[i][j].tuple.src.l3num, ports[i]);
1674                                 nf_conntrack_sip_fini();
1675                                 return ret;
1676                         }
1677                 }
1678         }
1679         return 0;
1680 }
1681 
1682 module_init(nf_conntrack_sip_init);
1683 module_exit(nf_conntrack_sip_fini);
1684 

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