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[DCCP]: Initial feature negotiation implementation
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1 /*
2  *  net/dccp/options.c
3  *
4  *  An implementation of the DCCP protocol
5  *  Copyright (c) 2005 Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
6  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
7  *  Copyright (c) 2005 Ian McDonald <iam4@cs.waikato.ac.nz>
8  *
9  *      This program is free software; you can redistribute it and/or
10  *      modify it under the terms of the GNU General Public License
11  *      as published by the Free Software Foundation; either version
12  *      2 of the License, or (at your option) any later version.
13  */
14 #include <linux/config.h>
15 #include <linux/dccp.h>
16 #include <linux/module.h>
17 #include <linux/types.h>
18 #include <linux/kernel.h>
19 #include <linux/skbuff.h>
20
21 #include "ackvec.h"
22 #include "ccid.h"
23 #include "dccp.h"
24 #include "feat.h"
25
26 /* stores the default values for new connection. may be changed with sysctl */
27 static const struct dccp_options dccpo_default_values = {
28         .dccpo_sequence_window    = DCCPF_INITIAL_SEQUENCE_WINDOW,
29         .dccpo_rx_ccid            = DCCPF_INITIAL_CCID,
30         .dccpo_tx_ccid            = DCCPF_INITIAL_CCID,
31         .dccpo_ack_ratio          = DCCPF_INITIAL_ACK_RATIO,
32         .dccpo_send_ack_vector    = DCCPF_INITIAL_SEND_ACK_VECTOR,
33         .dccpo_send_ndp_count     = DCCPF_INITIAL_SEND_NDP_COUNT,
34 };
35
36 void dccp_options_init(struct dccp_options *dccpo)
37 {
38         memcpy(dccpo, &dccpo_default_values, sizeof(*dccpo));
39 }
40
41 static u32 dccp_decode_value_var(const unsigned char *bf, const u8 len)
42 {
43         u32 value = 0;
44
45         if (len > 3)
46                 value += *bf++ << 24;
47         if (len > 2)
48                 value += *bf++ << 16;
49         if (len > 1)
50                 value += *bf++ << 8;
51         if (len > 0)
52                 value += *bf;
53
54         return value;
55 }
56
57 int dccp_parse_options(struct sock *sk, struct sk_buff *skb)
58 {
59         struct dccp_sock *dp = dccp_sk(sk);
60 #ifdef CONFIG_IP_DCCP_DEBUG
61         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
62                                         "CLIENT rx opt: " : "server rx opt: ";
63 #endif
64         const struct dccp_hdr *dh = dccp_hdr(skb);
65         const u8 pkt_type = DCCP_SKB_CB(skb)->dccpd_type;
66         unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
67         unsigned char *opt_ptr = options;
68         const unsigned char *opt_end = (unsigned char *)dh +
69                                         (dh->dccph_doff * 4);
70         struct dccp_options_received *opt_recv = &dp->dccps_options_received;
71         unsigned char opt, len;
72         unsigned char *value;
73         u32 elapsed_time;
74         int rc;
75         int mandatory = 0;
76
77         memset(opt_recv, 0, sizeof(*opt_recv));
78
79         while (opt_ptr != opt_end) {
80                 opt   = *opt_ptr++;
81                 len   = 0;
82                 value = NULL;
83
84                 /* Check if this isn't a single byte option */
85                 if (opt > DCCPO_MAX_RESERVED) {
86                         if (opt_ptr == opt_end)
87                                 goto out_invalid_option;
88
89                         len = *opt_ptr++;
90                         if (len < 3)
91                                 goto out_invalid_option;
92                         /*
93                          * Remove the type and len fields, leaving
94                          * just the value size
95                          */
96                         len     -= 2;
97                         value   = opt_ptr;
98                         opt_ptr += len;
99
100                         if (opt_ptr > opt_end)
101                                 goto out_invalid_option;
102                 }
103
104                 switch (opt) {
105                 case DCCPO_PADDING:
106                         break;
107                 case DCCPO_MANDATORY:
108                         if (mandatory)
109                                 goto out_invalid_option;
110                         mandatory = 1;
111                         break;
112                 case DCCPO_NDP_COUNT:
113                         if (len > 3)
114                                 goto out_invalid_option;
115
116                         opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
117                         dccp_pr_debug("%sNDP count=%d\n", debug_prefix,
118                                       opt_recv->dccpor_ndp);
119                         break;
120                 case DCCPO_CHANGE_L:
121                         /* fall through */
122                 case DCCPO_CHANGE_R:
123                         if (len < 2)
124                                 goto out_invalid_option;
125                         rc = dccp_feat_change_recv(sk, opt, *value, value + 1,
126                                                    len - 1);
127                         /*
128                          * When there is a change error, change_recv is
129                          * responsible for dealing with it.  i.e. reply with an
130                          * empty confirm.
131                          * If the change was mandatory, then we need to die.
132                          */
133                         if (rc && mandatory)
134                                 goto out_invalid_option;
135                         break;
136                 case DCCPO_CONFIRM_L:
137                         /* fall through */
138                 case DCCPO_CONFIRM_R:
139                         if (len < 2)
140                                 goto out_invalid_option;
141                         if (dccp_feat_confirm_recv(sk, opt, *value,
142                                                    value + 1, len - 1))
143                                 goto out_invalid_option;
144                         break;
145                 case DCCPO_ACK_VECTOR_0:
146                 case DCCPO_ACK_VECTOR_1:
147                         if (pkt_type == DCCP_PKT_DATA)
148                                 continue;
149
150                         if (dp->dccps_options.dccpo_send_ack_vector &&
151                             dccp_ackvec_parse(sk, skb, opt, value, len))
152                                 goto out_invalid_option;
153                         break;
154                 case DCCPO_TIMESTAMP:
155                         if (len != 4)
156                                 goto out_invalid_option;
157
158                         opt_recv->dccpor_timestamp = ntohl(*(u32 *)value);
159
160                         dp->dccps_timestamp_echo = opt_recv->dccpor_timestamp;
161                         dccp_timestamp(sk, &dp->dccps_timestamp_time);
162
163                         dccp_pr_debug("%sTIMESTAMP=%u, ackno=%llu\n",
164                                       debug_prefix, opt_recv->dccpor_timestamp,
165                                       (unsigned long long)
166                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
167                         break;
168                 case DCCPO_TIMESTAMP_ECHO:
169                         if (len != 4 && len != 6 && len != 8)
170                                 goto out_invalid_option;
171
172                         opt_recv->dccpor_timestamp_echo = ntohl(*(u32 *)value);
173
174                         dccp_pr_debug("%sTIMESTAMP_ECHO=%u, len=%d, ackno=%llu, ",
175                                       debug_prefix,
176                                       opt_recv->dccpor_timestamp_echo,
177                                       len + 2,
178                                       (unsigned long long)
179                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
180
181
182                         if (len == 4)
183                                 break;
184
185                         if (len == 6)
186                                 elapsed_time = ntohs(*(u16 *)(value + 4));
187                         else
188                                 elapsed_time = ntohl(*(u32 *)(value + 4));
189
190                         /* Give precedence to the biggest ELAPSED_TIME */
191                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
192                                 opt_recv->dccpor_elapsed_time = elapsed_time;
193                         break;
194                 case DCCPO_ELAPSED_TIME:
195                         if (len != 2 && len != 4)
196                                 goto out_invalid_option;
197
198                         if (pkt_type == DCCP_PKT_DATA)
199                                 continue;
200
201                         if (len == 2)
202                                 elapsed_time = ntohs(*(u16 *)value);
203                         else
204                                 elapsed_time = ntohl(*(u32 *)value);
205
206                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
207                                 opt_recv->dccpor_elapsed_time = elapsed_time;
208
209                         dccp_pr_debug("%sELAPSED_TIME=%d\n", debug_prefix,
210                                       elapsed_time);
211                         break;
212                         /*
213                          * From draft-ietf-dccp-spec-11.txt:
214                          *
215                          *      Option numbers 128 through 191 are for
216                          *      options sent from the HC-Sender to the
217                          *      HC-Receiver; option numbers 192 through 255
218                          *      are for options sent from the HC-Receiver to
219                          *      the HC-Sender.
220                          */
221                 case 128 ... 191: {
222                         const u16 idx = value - options;
223
224                         if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
225                                                      opt, len, idx,
226                                                      value) != 0)
227                                 goto out_invalid_option;
228                 }
229                         break;
230                 case 192 ... 255: {
231                         const u16 idx = value - options;
232
233                         if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
234                                                      opt, len, idx,
235                                                      value) != 0)
236                                 goto out_invalid_option;
237                 }
238                         break;
239                 default:
240                         pr_info("DCCP(%p): option %d(len=%d) not "
241                                 "implemented, ignoring\n",
242                                 sk, opt, len);
243                         break;
244                 }
245
246                 if (opt != DCCPO_MANDATORY)
247                         mandatory = 0;
248         }
249
250         return 0;
251
252 out_invalid_option:
253         DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
254         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_OPTION_ERROR;
255         pr_info("DCCP(%p): invalid option %d, len=%d\n", sk, opt, len);
256         return -1;
257 }
258
259 static void dccp_encode_value_var(const u32 value, unsigned char *to,
260                                   const unsigned int len)
261 {
262         if (len > 3)
263                 *to++ = (value & 0xFF000000) >> 24;
264         if (len > 2)
265                 *to++ = (value & 0xFF0000) >> 16;
266         if (len > 1)
267                 *to++ = (value & 0xFF00) >> 8;
268         if (len > 0)
269                 *to++ = (value & 0xFF);
270 }
271
272 static inline int dccp_ndp_len(const int ndp)
273 {
274         return likely(ndp <= 0xFF) ? 1 : ndp <= 0xFFFF ? 2 : 3;
275 }
276
277 void dccp_insert_option(struct sock *sk, struct sk_buff *skb,
278                         const unsigned char option,
279                         const void *value, const unsigned char len)
280 {
281         unsigned char *to;
282
283         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 2 > DCCP_MAX_OPT_LEN) {
284                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small to insert "
285                                "%d option!\n", option);
286                 return;
287         }
288
289         DCCP_SKB_CB(skb)->dccpd_opt_len += len + 2;
290
291         to    = skb_push(skb, len + 2);
292         *to++ = option;
293         *to++ = len + 2;
294
295         memcpy(to, value, len);
296 }
297
298 EXPORT_SYMBOL_GPL(dccp_insert_option);
299
300 static void dccp_insert_option_ndp(struct sock *sk, struct sk_buff *skb)
301 {
302         struct dccp_sock *dp = dccp_sk(sk);
303         int ndp = dp->dccps_ndp_count;
304
305         if (dccp_non_data_packet(skb))
306                 ++dp->dccps_ndp_count;
307         else
308                 dp->dccps_ndp_count = 0;
309
310         if (ndp > 0) {
311                 unsigned char *ptr;
312                 const int ndp_len = dccp_ndp_len(ndp);
313                 const int len = ndp_len + 2;
314
315                 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
316                         return;
317
318                 DCCP_SKB_CB(skb)->dccpd_opt_len += len;
319
320                 ptr = skb_push(skb, len);
321                 *ptr++ = DCCPO_NDP_COUNT;
322                 *ptr++ = len;
323                 dccp_encode_value_var(ndp, ptr, ndp_len);
324         }
325 }
326
327 static inline int dccp_elapsed_time_len(const u32 elapsed_time)
328 {
329         return elapsed_time == 0 ? 0 : elapsed_time <= 0xFFFF ? 2 : 4;
330 }
331
332 void dccp_insert_option_elapsed_time(struct sock *sk,
333                                      struct sk_buff *skb,
334                                      u32 elapsed_time)
335 {
336 #ifdef CONFIG_IP_DCCP_DEBUG
337         struct dccp_sock *dp = dccp_sk(sk);
338         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
339                                         "CLIENT TX opt: " : "server TX opt: ";
340 #endif
341         const int elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
342         const int len = 2 + elapsed_time_len;
343         unsigned char *to;
344
345         if (elapsed_time_len == 0)
346                 return;
347
348         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
349                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small to "
350                                          "insert elapsed time!\n");
351                 return;
352         }
353
354         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
355
356         to    = skb_push(skb, len);
357         *to++ = DCCPO_ELAPSED_TIME;
358         *to++ = len;
359
360         if (elapsed_time_len == 2) {
361                 const u16 var16 = htons((u16)elapsed_time);
362                 memcpy(to, &var16, 2);
363         } else {
364                 const u32 var32 = htonl(elapsed_time);
365                 memcpy(to, &var32, 4);
366         }
367
368         dccp_pr_debug("%sELAPSED_TIME=%u, len=%d, seqno=%llu\n",
369                       debug_prefix, elapsed_time,
370                       len,
371                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
372 }
373
374 EXPORT_SYMBOL_GPL(dccp_insert_option_elapsed_time);
375
376 void dccp_timestamp(const struct sock *sk, struct timeval *tv)
377 {
378         const struct dccp_sock *dp = dccp_sk(sk);
379
380         do_gettimeofday(tv);
381         tv->tv_sec  -= dp->dccps_epoch.tv_sec;
382         tv->tv_usec -= dp->dccps_epoch.tv_usec;
383
384         while (tv->tv_usec < 0) {
385                 tv->tv_sec--;
386                 tv->tv_usec += USEC_PER_SEC;
387         }
388 }
389
390 EXPORT_SYMBOL_GPL(dccp_timestamp);
391
392 void dccp_insert_option_timestamp(struct sock *sk, struct sk_buff *skb)
393 {
394         struct timeval tv;
395         u32 now;
396
397         dccp_timestamp(sk, &tv);
398         now = timeval_usecs(&tv) / 10;
399         /* yes this will overflow but that is the point as we want a
400          * 10 usec 32 bit timer which mean it wraps every 11.9 hours */
401
402         now = htonl(now);
403         dccp_insert_option(sk, skb, DCCPO_TIMESTAMP, &now, sizeof(now));
404 }
405
406 EXPORT_SYMBOL_GPL(dccp_insert_option_timestamp);
407
408 static void dccp_insert_option_timestamp_echo(struct sock *sk,
409                                               struct sk_buff *skb)
410 {
411         struct dccp_sock *dp = dccp_sk(sk);
412 #ifdef CONFIG_IP_DCCP_DEBUG
413         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
414                                         "CLIENT TX opt: " : "server TX opt: ";
415 #endif
416         struct timeval now;
417         u32 tstamp_echo;
418         u32 elapsed_time;
419         int len, elapsed_time_len;
420         unsigned char *to;
421
422         dccp_timestamp(sk, &now);
423         elapsed_time = timeval_delta(&now, &dp->dccps_timestamp_time) / 10;
424         elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
425         len = 6 + elapsed_time_len;
426
427         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
428                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small to insert "
429                                          "timestamp echo!\n");
430                 return;
431         }
432
433         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
434
435         to    = skb_push(skb, len);
436         *to++ = DCCPO_TIMESTAMP_ECHO;
437         *to++ = len;
438
439         tstamp_echo = htonl(dp->dccps_timestamp_echo);
440         memcpy(to, &tstamp_echo, 4);
441         to += 4;
442
443         if (elapsed_time_len == 2) {
444                 const u16 var16 = htons((u16)elapsed_time);
445                 memcpy(to, &var16, 2);
446         } else if (elapsed_time_len == 4) {
447                 const u32 var32 = htonl(elapsed_time);
448                 memcpy(to, &var32, 4);
449         }
450
451         dccp_pr_debug("%sTIMESTAMP_ECHO=%u, len=%d, seqno=%llu\n",
452                       debug_prefix, dp->dccps_timestamp_echo,
453                       len,
454                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
455
456         dp->dccps_timestamp_echo = 0;
457         dp->dccps_timestamp_time.tv_sec = 0;
458         dp->dccps_timestamp_time.tv_usec = 0;
459 }
460
461 static int dccp_insert_feat_opt(struct sk_buff *skb, u8 type, u8 feat,
462                                 u8 *val, u8 len)
463 {
464         u8 *to;
465
466         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 3 > DCCP_MAX_OPT_LEN) {
467                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small"
468                                " to insert feature %d option!\n", feat);
469                 return -1;
470         }
471
472         DCCP_SKB_CB(skb)->dccpd_opt_len += len + 3;
473
474         to    = skb_push(skb, len + 3);
475         *to++ = type;
476         *to++ = len + 3;
477         *to++ = feat;
478
479         if (len)
480                 memcpy(to, val, len);
481         dccp_pr_debug("option %d feat %d len %d\n", type, feat, len);
482
483         return 0;
484 }
485
486 static void dccp_insert_feat(struct sock *sk, struct sk_buff *skb)
487 {
488         struct dccp_sock *dp = dccp_sk(sk);
489         struct dccp_opt_pend *opt, *next;
490         int change = 0;
491
492         /* confirm any options [NN opts] */
493         list_for_each_entry_safe(opt, next, &dp->dccps_options.dccpo_conf,
494                                  dccpop_node) {
495                 dccp_insert_feat_opt(skb, opt->dccpop_type,
496                                      opt->dccpop_feat, opt->dccpop_val,
497                                      opt->dccpop_len);
498                 /* fear empty confirms */
499                 if (opt->dccpop_val)
500                         kfree(opt->dccpop_val);
501                 kfree(opt);
502         }
503         INIT_LIST_HEAD(&dp->dccps_options.dccpo_conf);
504
505         /* see which features we need to send */
506         list_for_each_entry(opt, &dp->dccps_options.dccpo_pending,
507                             dccpop_node) {
508                 /* see if we need to send any confirm */
509                 if (opt->dccpop_sc) {
510                         dccp_insert_feat_opt(skb, opt->dccpop_type + 1,
511                                              opt->dccpop_feat,
512                                              opt->dccpop_sc->dccpoc_val,
513                                              opt->dccpop_sc->dccpoc_len);
514
515                         BUG_ON(!opt->dccpop_sc->dccpoc_val);
516                         kfree(opt->dccpop_sc->dccpoc_val);
517                         kfree(opt->dccpop_sc);
518                         opt->dccpop_sc = NULL;
519                 }
520
521                 /* any option not confirmed, re-send it */
522                 if (!opt->dccpop_conf) {
523                         dccp_insert_feat_opt(skb, opt->dccpop_type,
524                                              opt->dccpop_feat, opt->dccpop_val,
525                                              opt->dccpop_len);
526                         change++;
527                 }
528         }
529
530         /* Retransmit timer.
531          * If this is the master listening sock, we don't set a timer on it.  It
532          * should be fine because if the dude doesn't receive our RESPONSE
533          * [which will contain the CHANGE] he will send another REQUEST which
534          * will "retrnasmit" the change.
535          */
536         if (change && dp->dccps_role != DCCP_ROLE_LISTEN) {
537                 dccp_pr_debug("reset feat negotiation timer %p\n", sk);
538
539                 /* XXX don't reset the timer on re-transmissions.  I.e. reset it
540                  * only when sending new stuff i guess.  Currently the timer
541                  * never backs off because on re-transmission it just resets it!
542                  */
543                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
544                                           inet_csk(sk)->icsk_rto, DCCP_RTO_MAX);
545         }
546 }
547
548 void dccp_insert_options(struct sock *sk, struct sk_buff *skb)
549 {
550         struct dccp_sock *dp = dccp_sk(sk);
551
552         DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
553
554         if (dp->dccps_options.dccpo_send_ndp_count)
555                 dccp_insert_option_ndp(sk, skb);
556
557         if (!dccp_packet_without_ack(skb)) {
558                 if (dp->dccps_options.dccpo_send_ack_vector &&
559                     dccp_ackvec_pending(dp->dccps_hc_rx_ackvec))
560                         dccp_insert_option_ackvec(sk, skb);
561                 if (dp->dccps_timestamp_echo != 0)
562                         dccp_insert_option_timestamp_echo(sk, skb);
563         }
564
565         if (dp->dccps_hc_rx_insert_options) {
566                 ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb);
567                 dp->dccps_hc_rx_insert_options = 0;
568         }
569         if (dp->dccps_hc_tx_insert_options) {
570                 ccid_hc_tx_insert_options(dp->dccps_hc_tx_ccid, sk, skb);
571                 dp->dccps_hc_tx_insert_options = 0;
572         }
573
574         /* Feature negotiation */
575         switch(DCCP_SKB_CB(skb)->dccpd_type) {
576                 /* Data packets can't do feat negotiation */
577         case DCCP_PKT_DATA:
578         case DCCP_PKT_DATAACK:
579                 break;
580         default:
581                 dccp_insert_feat(sk, skb);
582                 break;
583         }
584
585         /* XXX: insert other options when appropriate */
586
587         if (DCCP_SKB_CB(skb)->dccpd_opt_len != 0) {
588                 /* The length of all options has to be a multiple of 4 */
589                 int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
590
591                 if (padding != 0) {
592                         padding = 4 - padding;
593                         memset(skb_push(skb, padding), 0, padding);
594                         DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
595                 }
596         }
597 }