1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * net/dccp/options.c
4 *
5 * An implementation of the DCCP protocol
6 * Copyright (c) 2005 Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
7 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
8 * Copyright (c) 2005 Ian McDonald <ian.mcdonald@jandi.co.nz>
9 */
10 #include <linux/dccp.h>
11 #include <linux/module.h>
12 #include <linux/types.h>
13 #include <asm/unaligned.h>
14 #include <linux/kernel.h>
15 #include <linux/skbuff.h>
16
17 #include "ackvec.h"
18 #include "ccid.h"
19 #include "dccp.h"
20 #include "feat.h"
21
22 u64 dccp_decode_value_var(const u8 *bf, const u8 len)
23 {
24 u64 value = 0;
25
26 if (len >= DCCP_OPTVAL_MAXLEN)
27 value += ((u64)*bf++) << 40;
28 if (len > 4)
29 value += ((u64)*bf++) << 32;
30 if (len > 3)
31 value += ((u64)*bf++) << 24;
32 if (len > 2)
33 value += ((u64)*bf++) << 16;
34 if (len > 1)
35 value += ((u64)*bf++) << 8;
36 if (len > 0)
37 value += *bf;
38
39 return value;
40 }
41
42 /**
43 * dccp_parse_options - Parse DCCP options present in @skb
44 * @sk: client|server|listening dccp socket (when @dreq != NULL)
45 * @dreq: request socket to use during connection setup, or NULL
46 * @skb: frame to parse
47 */
48 int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
49 struct sk_buff *skb)
50 {
51 struct dccp_sock *dp = dccp_sk(sk);
52 const struct dccp_hdr *dh = dccp_hdr(skb);
53 const u8 pkt_type = DCCP_SKB_CB(skb)->dccpd_type;
54 unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
55 unsigned char *opt_ptr = options;
56 const unsigned char *opt_end = (unsigned char *)dh +
57 (dh->dccph_doff * 4);
58 struct dccp_options_received *opt_recv = &dp->dccps_options_received;
59 unsigned char opt, len;
60 unsigned char *value;
61 u32 elapsed_time;
62 __be32 opt_val;
63 int rc;
64 int mandatory = 0;
65
66 memset(opt_recv, 0, sizeof(*opt_recv));
67
68 opt = len = 0;
69 while (opt_ptr != opt_end) {
70 opt = *opt_ptr++;
71 len = 0;
72 value = NULL;
73
74 /* Check if this isn't a single byte option */
75 if (opt > DCCPO_MAX_RESERVED) {
76 if (opt_ptr == opt_end)
77 goto out_nonsensical_length;
78
79 len = *opt_ptr++;
80 if (len < 2)
81 goto out_nonsensical_length;
82 /*
83 * Remove the type and len fields, leaving
84 * just the value size
85 */
86 len -= 2;
87 value = opt_ptr;
88 opt_ptr += len;
89
90 if (opt_ptr > opt_end)
91 goto out_nonsensical_length;
92 }
93
94 /*
95 * CCID-specific options are ignored during connection setup, as
96 * negotiation may still be in progress (see RFC 4340, 10.3).
97 * The same applies to Ack Vectors, as these depend on the CCID.
98 */
99 if (dreq != NULL && (opt >= DCCPO_MIN_RX_CCID_SPECIFIC ||
100 opt == DCCPO_ACK_VECTOR_0 || opt == DCCPO_ACK_VECTOR_1))
101 goto ignore_option;
102
103 switch (opt) {
104 case DCCPO_PADDING:
105 break;
106 case DCCPO_MANDATORY:
107 if (mandatory)
108 goto out_invalid_option;
109 if (pkt_type != DCCP_PKT_DATA)
110 mandatory = 1;
111 break;
112 case DCCPO_NDP_COUNT:
113 if (len > 6)
114 goto out_invalid_option;
115
116 opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
117 dccp_pr_debug("%s opt: NDP count=%llu\n", dccp_role(sk),
118 (unsigned long long)opt_recv->dccpor_ndp);
119 break;
120 case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R:
121 if (pkt_type == DCCP_PKT_DATA) /* RFC 4340, 6 */
122 break;
123 if (len == 0)
124 goto out_invalid_option;
125 rc = dccp_feat_parse_options(sk, dreq, mandatory, opt,
126 *value, value + 1, len - 1);
127 if (rc)
128 goto out_featneg_failed;
129 break;
130 case DCCPO_TIMESTAMP:
131 if (len != 4)
132 goto out_invalid_option;
133 /*
134 * RFC 4340 13.1: "The precise time corresponding to
135 * Timestamp Value zero is not specified". We use
136 * zero to indicate absence of a meaningful timestamp.
137 */
138 opt_val = get_unaligned((__be32 *)value);
139 if (unlikely(opt_val == 0)) {
140 DCCP_WARN("Timestamp with zero value\n");
141 break;
142 }
143
144 if (dreq != NULL) {
145 dreq->dreq_timestamp_echo = ntohl(opt_val);
146 dreq->dreq_timestamp_time = dccp_timestamp();
147 } else {
148 opt_recv->dccpor_timestamp =
149 dp->dccps_timestamp_echo = ntohl(opt_val);
150 dp->dccps_timestamp_time = dccp_timestamp();
151 }
152 dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n",
153 dccp_role(sk), ntohl(opt_val),
154 (unsigned long long)
155 DCCP_SKB_CB(skb)->dccpd_ack_seq);
156 /* schedule an Ack in case this sender is quiescent */
157 inet_csk_schedule_ack(sk);
158 break;
159 case DCCPO_TIMESTAMP_ECHO:
160 if (len != 4 && len != 6 && len != 8)
161 goto out_invalid_option;
162
163 opt_val = get_unaligned((__be32 *)value);
164 opt_recv->dccpor_timestamp_echo = ntohl(opt_val);
165
166 dccp_pr_debug("%s rx opt: TIMESTAMP_ECHO=%u, len=%d, "
167 "ackno=%llu", dccp_role(sk),
168 opt_recv->dccpor_timestamp_echo,
169 len + 2,
170 (unsigned long long)
171 DCCP_SKB_CB(skb)->dccpd_ack_seq);
172
173 value += 4;
174
175 if (len == 4) { /* no elapsed time included */
176 dccp_pr_debug_cat("\n");
177 break;
178 }
179
180 if (len == 6) { /* 2-byte elapsed time */
181 __be16 opt_val2 = get_unaligned((__be16 *)value);
182 elapsed_time = ntohs(opt_val2);
183 } else { /* 4-byte elapsed time */
184 opt_val = get_unaligned((__be32 *)value);
185 elapsed_time = ntohl(opt_val);
186 }
187
188 dccp_pr_debug_cat(", ELAPSED_TIME=%u\n", elapsed_time);
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 (dccp_packet_without_ack(skb)) /* RFC 4340, 13.2 */
196 break;
197
198 if (len == 2) {
199 __be16 opt_val2 = get_unaligned((__be16 *)value);
200 elapsed_time = ntohs(opt_val2);
201 } else if (len == 4) {
202 opt_val = get_unaligned((__be32 *)value);
203 elapsed_time = ntohl(opt_val);
204 } else {
205 goto out_invalid_option;
206 }
207
208 if (elapsed_time > opt_recv->dccpor_elapsed_time)
209 opt_recv->dccpor_elapsed_time = elapsed_time;
210
211 dccp_pr_debug("%s rx opt: ELAPSED_TIME=%d\n",
212 dccp_role(sk), elapsed_time);
213 break;
214 case DCCPO_MIN_RX_CCID_SPECIFIC ... DCCPO_MAX_RX_CCID_SPECIFIC:
215 if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
216 pkt_type, opt, value, len))
217 goto out_invalid_option;
218 break;
219 case DCCPO_ACK_VECTOR_0:
220 case DCCPO_ACK_VECTOR_1:
221 if (dccp_packet_without_ack(skb)) /* RFC 4340, 11.4 */
222 break;
223 /*
224 * Ack vectors are processed by the TX CCID if it is
225 * interested. The RX CCID need not parse Ack Vectors,
226 * since it is only interested in clearing old state.
227 */
228 fallthrough;
229 case DCCPO_MIN_TX_CCID_SPECIFIC ... DCCPO_MAX_TX_CCID_SPECIFIC:
230 if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
231 pkt_type, opt, value, len))
232 goto out_invalid_option;
233 break;
234 default:
235 DCCP_CRIT("DCCP(%p): option %d(len=%d) not "
236 "implemented, ignoring", sk, opt, len);
237 break;
238 }
239 ignore_option:
240 if (opt != DCCPO_MANDATORY)
241 mandatory = 0;
242 }
243
244 /* mandatory was the last byte in option list -> reset connection */
245 if (mandatory)
246 goto out_invalid_option;
247
248 out_nonsensical_length:
249 /* RFC 4340, 5.8: ignore option and all remaining option space */
250 return 0;
251
252 out_invalid_option:
253 DCCP_INC_STATS(DCCP_MIB_INVALIDOPT);
254 rc = DCCP_RESET_CODE_OPTION_ERROR;
255 out_featneg_failed:
256 DCCP_WARN("DCCP(%p): Option %d (len=%d) error=%u\n", sk, opt, len, rc);
257 DCCP_SKB_CB(skb)->dccpd_reset_code = rc;
258 DCCP_SKB_CB(skb)->dccpd_reset_data[0] = opt;
259 DCCP_SKB_CB(skb)->dccpd_reset_data[1] = len > 0 ? value[0] : 0;
260 DCCP_SKB_CB(skb)->dccpd_reset_data[2] = len > 1 ? value[1] : 0;
261 return -1;
262 }
263
264 EXPORT_SYMBOL_GPL(dccp_parse_options);
265
266 void dccp_encode_value_var(const u64 value, u8 *to, const u8 len)
267 {
268 if (len >= DCCP_OPTVAL_MAXLEN)
269 *to++ = (value & 0xFF0000000000ull) >> 40;
270 if (len > 4)
271 *to++ = (value & 0xFF00000000ull) >> 32;
272 if (len > 3)
273 *to++ = (value & 0xFF000000) >> 24;
274 if (len > 2)
275 *to++ = (value & 0xFF0000) >> 16;
276 if (len > 1)
277 *to++ = (value & 0xFF00) >> 8;
278 if (len > 0)
279 *to++ = (value & 0xFF);
280 }
281
282 static inline u8 dccp_ndp_len(const u64 ndp)
283 {
284 if (likely(ndp <= 0xFF))
285 return 1;
286 return likely(ndp <= USHRT_MAX) ? 2 : (ndp <= UINT_MAX ? 4 : 6);
287 }
288
289 int dccp_insert_option(struct sk_buff *skb, const unsigned char option,
290 const void *value, const unsigned char len)
291 {
292 unsigned char *to;
293
294 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 2 > DCCP_MAX_OPT_LEN)
295 return -1;
296
297 DCCP_SKB_CB(skb)->dccpd_opt_len += len + 2;
298
299 to = skb_push(skb, len + 2);
300 *to++ = option;
301 *to++ = len + 2;
302
303 memcpy(to, value, len);
304 return 0;
305 }
306
307 EXPORT_SYMBOL_GPL(dccp_insert_option);
308
309 static int dccp_insert_option_ndp(struct sock *sk, struct sk_buff *skb)
310 {
311 struct dccp_sock *dp = dccp_sk(sk);
312 u64 ndp = dp->dccps_ndp_count;
313
314 if (dccp_non_data_packet(skb))
315 ++dp->dccps_ndp_count;
316 else
317 dp->dccps_ndp_count = 0;
318
319 if (ndp > 0) {
320 unsigned char *ptr;
321 const int ndp_len = dccp_ndp_len(ndp);
322 const int len = ndp_len + 2;
323
324 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
325 return -1;
326
327 DCCP_SKB_CB(skb)->dccpd_opt_len += len;
328
329 ptr = skb_push(skb, len);
330 *ptr++ = DCCPO_NDP_COUNT;
331 *ptr++ = len;
332 dccp_encode_value_var(ndp, ptr, ndp_len);
333 }
334
335 return 0;
336 }
337
338 static inline int dccp_elapsed_time_len(const u32 elapsed_time)
339 {
340 return elapsed_time == 0 ? 0 : elapsed_time <= 0xFFFF ? 2 : 4;
341 }
342
343 static int dccp_insert_option_timestamp(struct sk_buff *skb)
344 {
345 __be32 now = htonl(dccp_timestamp());
346 /* yes this will overflow but that is the point as we want a
347 * 10 usec 32 bit timer which mean it wraps every 11.9 hours */
348
349 return dccp_insert_option(skb, DCCPO_TIMESTAMP, &now, sizeof(now));
350 }
351
352 static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
353 struct dccp_request_sock *dreq,
354 struct sk_buff *skb)
355 {
356 __be32 tstamp_echo;
357 unsigned char *to;
358 u32 elapsed_time, elapsed_time_len, len;
359
360 if (dreq != NULL) {
361 elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time;
362 tstamp_echo = htonl(dreq->dreq_timestamp_echo);
363 dreq->dreq_timestamp_echo = 0;
364 } else {
365 elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time;
366 tstamp_echo = htonl(dp->dccps_timestamp_echo);
367 dp->dccps_timestamp_echo = 0;
368 }
369
370 elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
371 len = 6 + elapsed_time_len;
372
373 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
374 return -1;
375
376 DCCP_SKB_CB(skb)->dccpd_opt_len += len;
377
378 to = skb_push(skb, len);
379 *to++ = DCCPO_TIMESTAMP_ECHO;
380 *to++ = len;
381
382 memcpy(to, &tstamp_echo, 4);
383 to += 4;
384
385 if (elapsed_time_len == 2) {
386 const __be16 var16 = htons((u16)elapsed_time);
387 memcpy(to, &var16, 2);
388 } else if (elapsed_time_len == 4) {
389 const __be32 var32 = htonl(elapsed_time);
390 memcpy(to, &var32, 4);
391 }
392
393 return 0;
394 }
395
396 static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
397 {
398 struct dccp_sock *dp = dccp_sk(sk);
399 struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
400 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
401 const u16 buflen = dccp_ackvec_buflen(av);
402 /* Figure out how many options do we need to represent the ackvec */
403 const u8 nr_opts = DIV_ROUND_UP(buflen, DCCP_SINGLE_OPT_MAXLEN);
404 u16 len = buflen + 2 * nr_opts;
405 u8 i, nonce = 0;
406 const unsigned char *tail, *from;
407 unsigned char *to;
408
409 if (dcb->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
410 DCCP_WARN("Lacking space for %u bytes on %s packet\n", len,
411 dccp_packet_name(dcb->dccpd_type));
412 return -1;
413 }
414 /*
415 * Since Ack Vectors are variable-length, we can not always predict
416 * their size. To catch exception cases where the space is running out
417 * on the skb, a separate Sync is scheduled to carry the Ack Vector.
418 */
419 if (len > DCCPAV_MIN_OPTLEN &&
420 len + dcb->dccpd_opt_len + skb->len > dp->dccps_mss_cache) {
421 DCCP_WARN("No space left for Ack Vector (%u) on skb (%u+%u), "
422 "MPS=%u ==> reduce payload size?\n", len, skb->len,
423 dcb->dccpd_opt_len, dp->dccps_mss_cache);
424 dp->dccps_sync_scheduled = 1;
425 return 0;
426 }
427 dcb->dccpd_opt_len += len;
428
429 to = skb_push(skb, len);
430 len = buflen;
431 from = av->av_buf + av->av_buf_head;
432 tail = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
433
434 for (i = 0; i < nr_opts; ++i) {
435 int copylen = len;
436
437 if (len > DCCP_SINGLE_OPT_MAXLEN)
438 copylen = DCCP_SINGLE_OPT_MAXLEN;
439
440 /*
441 * RFC 4340, 12.2: Encode the Nonce Echo for this Ack Vector via
442 * its type; ack_nonce is the sum of all individual buf_nonce's.
443 */
444 nonce ^= av->av_buf_nonce[i];
445
446 *to++ = DCCPO_ACK_VECTOR_0 + av->av_buf_nonce[i];
447 *to++ = copylen + 2;
448
449 /* Check if buf_head wraps */
450 if (from + copylen > tail) {
451 const u16 tailsize = tail - from;
452
453 memcpy(to, from, tailsize);
454 to += tailsize;
455 len -= tailsize;
456 copylen -= tailsize;
457 from = av->av_buf;
458 }
459
460 memcpy(to, from, copylen);
461 from += copylen;
462 to += copylen;
463 len -= copylen;
464 }
465 /*
466 * Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340.
467 */
468 if (dccp_ackvec_update_records(av, dcb->dccpd_seq, nonce))
469 return -ENOBUFS;
470 return 0;
471 }
472
473 /**
474 * dccp_insert_option_mandatory - Mandatory option (5.8.2)
475 * @skb: frame into which to insert option
476 *
477 * Note that since we are using skb_push, this function needs to be called
478 * _after_ inserting the option it is supposed to influence (stack order).
479 */
480 int dccp_insert_option_mandatory(struct sk_buff *skb)
481 {
482 if (DCCP_SKB_CB(skb)->dccpd_opt_len >= DCCP_MAX_OPT_LEN)
483 return -1;
484
485 DCCP_SKB_CB(skb)->dccpd_opt_len++;
486 *(u8 *)skb_push(skb, 1) = DCCPO_MANDATORY;
487 return 0;
488 }
489
490 /**
491 * dccp_insert_fn_opt - Insert single Feature-Negotiation option into @skb
492 * @skb: frame to insert feature negotiation option into
493 * @type: %DCCPO_CHANGE_L, %DCCPO_CHANGE_R, %DCCPO_CONFIRM_L, %DCCPO_CONFIRM_R
494 * @feat: one out of %dccp_feature_numbers
495 * @val: NN value or SP array (preferred element first) to copy
496 * @len: true length of @val in bytes (excluding first element repetition)
497 * @repeat_first: whether to copy the first element of @val twice
498 *
499 * The last argument is used to construct Confirm options, where the preferred
500 * value and the preference list appear separately (RFC 4340, 6.3.1). Preference
501 * lists are kept such that the preferred entry is always first, so we only need
502 * to copy twice, and avoid the overhead of cloning into a bigger array.
503 */
504 int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
505 u8 *val, u8 len, bool repeat_first)
506 {
507 u8 tot_len, *to;
508
509 /* take the `Feature' field and possible repetition into account */
510 if (len > (DCCP_SINGLE_OPT_MAXLEN - 2)) {
511 DCCP_WARN("length %u for feature %u too large\n", len, feat);
512 return -1;
513 }
514
515 if (unlikely(val == NULL || len == 0))
516 len = repeat_first = false;
517 tot_len = 3 + repeat_first + len;
518
519 if (DCCP_SKB_CB(skb)->dccpd_opt_len + tot_len > DCCP_MAX_OPT_LEN) {
520 DCCP_WARN("packet too small for feature %d option!\n", feat);
521 return -1;
522 }
523 DCCP_SKB_CB(skb)->dccpd_opt_len += tot_len;
524
525 to = skb_push(skb, tot_len);
526 *to++ = type;
527 *to++ = tot_len;
528 *to++ = feat;
529
530 if (repeat_first)
531 *to++ = *val;
532 if (len)
533 memcpy(to, val, len);
534 return 0;
535 }
536
537 /* The length of all options needs to be a multiple of 4 (5.8) */
538 static void dccp_insert_option_padding(struct sk_buff *skb)
539 {
540 int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
541
542 if (padding != 0) {
543 padding = 4 - padding;
544 memset(skb_push(skb, padding), 0, padding);
545 DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
546 }
547 }
548
549 int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
550 {
551 struct dccp_sock *dp = dccp_sk(sk);
552
553 DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
554
555 if (dp->dccps_send_ndp_count && dccp_insert_option_ndp(sk, skb))
556 return -1;
557
558 if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA) {
559
560 /* Feature Negotiation */
561 if (dccp_feat_insert_opts(dp, NULL, skb))
562 return -1;
563
564 if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST) {
565 /*
566 * Obtain RTT sample from Request/Response exchange.
567 * This is currently used for TFRC initialisation.
568 */
569 if (dccp_insert_option_timestamp(skb))
570 return -1;
571
572 } else if (dccp_ackvec_pending(sk) &&
573 dccp_insert_option_ackvec(sk, skb)) {
574 return -1;
575 }
576 }
577
578 if (dp->dccps_hc_rx_insert_options) {
579 if (ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb))
580 return -1;
581 dp->dccps_hc_rx_insert_options = 0;
582 }
583
584 if (dp->dccps_timestamp_echo != 0 &&
585 dccp_insert_option_timestamp_echo(dp, NULL, skb))
586 return -1;
587
588 dccp_insert_option_padding(skb);
589 return 0;
590 }
591
592 int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb)
593 {
594 DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
595
596 if (dccp_feat_insert_opts(NULL, dreq, skb))
597 return -1;
598
599 /* Obtain RTT sample from Response/Ack exchange (used by TFRC). */
600 if (dccp_insert_option_timestamp(skb))
601 return -1;
602
603 if (dreq->dreq_timestamp_echo != 0 &&
604 dccp_insert_option_timestamp_echo(NULL, dreq, skb))
605 return -1;
606
607 dccp_insert_option_padding(skb);
608 return 0;
609 }
610
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