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options.c
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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 <[email protected]>
6  * Copyright (c) 2005 Arnaldo Carvalho de Melo <[email protected]>
7  * Copyright (c) 2005 Ian McDonald <[email protected]>
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/dccp.h>
15 #include <linux/module.h>
16 #include <linux/types.h>
17 #include <asm/unaligned.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 u64 dccp_decode_value_var(const u8 *bf, const u8 len)
27 {
28  u64 value = 0;
29 
30  if (len >= DCCP_OPTVAL_MAXLEN)
31  value += ((u64)*bf++) << 40;
32  if (len > 4)
33  value += ((u64)*bf++) << 32;
34  if (len > 3)
35  value += ((u64)*bf++) << 24;
36  if (len > 2)
37  value += ((u64)*bf++) << 16;
38  if (len > 1)
39  value += ((u64)*bf++) << 8;
40  if (len > 0)
41  value += *bf;
42 
43  return value;
44 }
45 
51 int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
52  struct sk_buff *skb)
53 {
54  struct dccp_sock *dp = dccp_sk(sk);
55  const struct dccp_hdr *dh = dccp_hdr(skb);
56  const u8 pkt_type = DCCP_SKB_CB(skb)->dccpd_type;
57  unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
58  unsigned char *opt_ptr = options;
59  const unsigned char *opt_end = (unsigned char *)dh +
60  (dh->dccph_doff * 4);
61  struct dccp_options_received *opt_recv = &dp->dccps_options_received;
62  unsigned char opt, len;
63  unsigned char *uninitialized_var(value);
64  u32 elapsed_time;
65  __be32 opt_val;
66  int rc;
67  int mandatory = 0;
68 
69  memset(opt_recv, 0, sizeof(*opt_recv));
70 
71  opt = len = 0;
72  while (opt_ptr != opt_end) {
73  opt = *opt_ptr++;
74  len = 0;
75  value = NULL;
76 
77  /* Check if this isn't a single byte option */
78  if (opt > DCCPO_MAX_RESERVED) {
79  if (opt_ptr == opt_end)
80  goto out_nonsensical_length;
81 
82  len = *opt_ptr++;
83  if (len < 2)
84  goto out_nonsensical_length;
85  /*
86  * Remove the type and len fields, leaving
87  * just the value size
88  */
89  len -= 2;
90  value = opt_ptr;
91  opt_ptr += len;
92 
93  if (opt_ptr > opt_end)
94  goto out_nonsensical_length;
95  }
96 
97  /*
98  * CCID-specific options are ignored during connection setup, as
99  * negotiation may still be in progress (see RFC 4340, 10.3).
100  * The same applies to Ack Vectors, as these depend on the CCID.
101  */
102  if (dreq != NULL && (opt >= DCCPO_MIN_RX_CCID_SPECIFIC ||
103  opt == DCCPO_ACK_VECTOR_0 || opt == DCCPO_ACK_VECTOR_1))
104  goto ignore_option;
105 
106  switch (opt) {
107  case DCCPO_PADDING:
108  break;
109  case DCCPO_MANDATORY:
110  if (mandatory)
111  goto out_invalid_option;
112  if (pkt_type != DCCP_PKT_DATA)
113  mandatory = 1;
114  break;
115  case DCCPO_NDP_COUNT:
116  if (len > 6)
117  goto out_invalid_option;
118 
119  opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
120  dccp_pr_debug("%s opt: NDP count=%llu\n", dccp_role(sk),
121  (unsigned long long)opt_recv->dccpor_ndp);
122  break;
124  if (pkt_type == DCCP_PKT_DATA) /* RFC 4340, 6 */
125  break;
126  if (len == 0)
127  goto out_invalid_option;
128  rc = dccp_feat_parse_options(sk, dreq, mandatory, opt,
129  *value, value + 1, len - 1);
130  if (rc)
131  goto out_featneg_failed;
132  break;
133  case DCCPO_TIMESTAMP:
134  if (len != 4)
135  goto out_invalid_option;
136  /*
137  * RFC 4340 13.1: "The precise time corresponding to
138  * Timestamp Value zero is not specified". We use
139  * zero to indicate absence of a meaningful timestamp.
140  */
141  opt_val = get_unaligned((__be32 *)value);
142  if (unlikely(opt_val == 0)) {
143  DCCP_WARN("Timestamp with zero value\n");
144  break;
145  }
146 
147  if (dreq != NULL) {
148  dreq->dreq_timestamp_echo = ntohl(opt_val);
150  } else {
151  opt_recv->dccpor_timestamp =
152  dp->dccps_timestamp_echo = ntohl(opt_val);
154  }
155  dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n",
156  dccp_role(sk), ntohl(opt_val),
157  (unsigned long long)
158  DCCP_SKB_CB(skb)->dccpd_ack_seq);
159  /* schedule an Ack in case this sender is quiescent */
160  inet_csk_schedule_ack(sk);
161  break;
163  if (len != 4 && len != 6 && len != 8)
164  goto out_invalid_option;
165 
166  opt_val = get_unaligned((__be32 *)value);
167  opt_recv->dccpor_timestamp_echo = ntohl(opt_val);
168 
169  dccp_pr_debug("%s rx opt: TIMESTAMP_ECHO=%u, len=%d, "
170  "ackno=%llu", dccp_role(sk),
171  opt_recv->dccpor_timestamp_echo,
172  len + 2,
173  (unsigned long long)
174  DCCP_SKB_CB(skb)->dccpd_ack_seq);
175 
176  value += 4;
177 
178  if (len == 4) { /* no elapsed time included */
179  dccp_pr_debug_cat("\n");
180  break;
181  }
182 
183  if (len == 6) { /* 2-byte elapsed time */
184  __be16 opt_val2 = get_unaligned((__be16 *)value);
185  elapsed_time = ntohs(opt_val2);
186  } else { /* 4-byte elapsed time */
187  opt_val = get_unaligned((__be32 *)value);
188  elapsed_time = ntohl(opt_val);
189  }
190 
191  dccp_pr_debug_cat(", ELAPSED_TIME=%u\n", elapsed_time);
192 
193  /* Give precedence to the biggest ELAPSED_TIME */
194  if (elapsed_time > opt_recv->dccpor_elapsed_time)
195  opt_recv->dccpor_elapsed_time = elapsed_time;
196  break;
197  case DCCPO_ELAPSED_TIME:
198  if (dccp_packet_without_ack(skb)) /* RFC 4340, 13.2 */
199  break;
200 
201  if (len == 2) {
202  __be16 opt_val2 = get_unaligned((__be16 *)value);
203  elapsed_time = ntohs(opt_val2);
204  } else if (len == 4) {
205  opt_val = get_unaligned((__be32 *)value);
206  elapsed_time = ntohl(opt_val);
207  } else {
208  goto out_invalid_option;
209  }
210 
211  if (elapsed_time > opt_recv->dccpor_elapsed_time)
212  opt_recv->dccpor_elapsed_time = elapsed_time;
213 
214  dccp_pr_debug("%s rx opt: ELAPSED_TIME=%d\n",
215  dccp_role(sk), elapsed_time);
216  break;
218  if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
219  pkt_type, opt, value, len))
220  goto out_invalid_option;
221  break;
222  case DCCPO_ACK_VECTOR_0:
223  case DCCPO_ACK_VECTOR_1:
224  if (dccp_packet_without_ack(skb)) /* RFC 4340, 11.4 */
225  break;
226  /*
227  * Ack vectors are processed by the TX CCID if it is
228  * interested. The RX CCID need not parse Ack Vectors,
229  * since it is only interested in clearing old state.
230  * Fall through.
231  */
233  if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
234  pkt_type, opt, value, len))
235  goto out_invalid_option;
236  break;
237  default:
238  DCCP_CRIT("DCCP(%p): option %d(len=%d) not "
239  "implemented, ignoring", sk, opt, len);
240  break;
241  }
242 ignore_option:
243  if (opt != DCCPO_MANDATORY)
244  mandatory = 0;
245  }
246 
247  /* mandatory was the last byte in option list -> reset connection */
248  if (mandatory)
249  goto out_invalid_option;
250 
251 out_nonsensical_length:
252  /* RFC 4340, 5.8: ignore option and all remaining option space */
253  return 0;
254 
255 out_invalid_option:
258 out_featneg_failed:
259  DCCP_WARN("DCCP(%p): Option %d (len=%d) error=%u\n", sk, opt, len, rc);
260  DCCP_SKB_CB(skb)->dccpd_reset_code = rc;
261  DCCP_SKB_CB(skb)->dccpd_reset_data[0] = opt;
262  DCCP_SKB_CB(skb)->dccpd_reset_data[1] = len > 0 ? value[0] : 0;
263  DCCP_SKB_CB(skb)->dccpd_reset_data[2] = len > 1 ? value[1] : 0;
264  return -1;
265 }
266 
268 
269 void dccp_encode_value_var(const u64 value, u8 *to, const u8 len)
270 {
271  if (len >= DCCP_OPTVAL_MAXLEN)
272  *to++ = (value & 0xFF0000000000ull) >> 40;
273  if (len > 4)
274  *to++ = (value & 0xFF00000000ull) >> 32;
275  if (len > 3)
276  *to++ = (value & 0xFF000000) >> 24;
277  if (len > 2)
278  *to++ = (value & 0xFF0000) >> 16;
279  if (len > 1)
280  *to++ = (value & 0xFF00) >> 8;
281  if (len > 0)
282  *to++ = (value & 0xFF);
283 }
284 
285 static inline u8 dccp_ndp_len(const u64 ndp)
286 {
287  if (likely(ndp <= 0xFF))
288  return 1;
289  return likely(ndp <= USHRT_MAX) ? 2 : (ndp <= UINT_MAX ? 4 : 6);
290 }
291 
292 int dccp_insert_option(struct sk_buff *skb, const unsigned char option,
293  const void *value, const unsigned char len)
294 {
295  unsigned char *to;
296 
297  if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 2 > DCCP_MAX_OPT_LEN)
298  return -1;
299 
300  DCCP_SKB_CB(skb)->dccpd_opt_len += len + 2;
301 
302  to = skb_push(skb, len + 2);
303  *to++ = option;
304  *to++ = len + 2;
305 
306  memcpy(to, value, len);
307  return 0;
308 }
309 
311 
312 static int dccp_insert_option_ndp(struct sock *sk, struct sk_buff *skb)
313 {
314  struct dccp_sock *dp = dccp_sk(sk);
315  u64 ndp = dp->dccps_ndp_count;
316 
317  if (dccp_non_data_packet(skb))
318  ++dp->dccps_ndp_count;
319  else
320  dp->dccps_ndp_count = 0;
321 
322  if (ndp > 0) {
323  unsigned char *ptr;
324  const int ndp_len = dccp_ndp_len(ndp);
325  const int len = ndp_len + 2;
326 
327  if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
328  return -1;
329 
330  DCCP_SKB_CB(skb)->dccpd_opt_len += len;
331 
332  ptr = skb_push(skb, len);
333  *ptr++ = DCCPO_NDP_COUNT;
334  *ptr++ = len;
335  dccp_encode_value_var(ndp, ptr, ndp_len);
336  }
337 
338  return 0;
339 }
340 
341 static inline int dccp_elapsed_time_len(const u32 elapsed_time)
342 {
343  return elapsed_time == 0 ? 0 : elapsed_time <= 0xFFFF ? 2 : 4;
344 }
345 
346 /* FIXME: This function is currently not used anywhere */
347 int dccp_insert_option_elapsed_time(struct sk_buff *skb, u32 elapsed_time)
348 {
349  const int elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
350  const int len = 2 + elapsed_time_len;
351  unsigned char *to;
352 
353  if (elapsed_time_len == 0)
354  return 0;
355 
356  if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
357  return -1;
358 
359  DCCP_SKB_CB(skb)->dccpd_opt_len += len;
360 
361  to = skb_push(skb, len);
362  *to++ = DCCPO_ELAPSED_TIME;
363  *to++ = len;
364 
365  if (elapsed_time_len == 2) {
366  const __be16 var16 = htons((u16)elapsed_time);
367  memcpy(to, &var16, 2);
368  } else {
369  const __be32 var32 = htonl(elapsed_time);
370  memcpy(to, &var32, 4);
371  }
372 
373  return 0;
374 }
375 
377 
378 static int dccp_insert_option_timestamp(struct sk_buff *skb)
379 {
380  __be32 now = htonl(dccp_timestamp());
381  /* yes this will overflow but that is the point as we want a
382  * 10 usec 32 bit timer which mean it wraps every 11.9 hours */
383 
384  return dccp_insert_option(skb, DCCPO_TIMESTAMP, &now, sizeof(now));
385 }
386 
387 static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
388  struct dccp_request_sock *dreq,
389  struct sk_buff *skb)
390 {
391  __be32 tstamp_echo;
392  unsigned char *to;
393  u32 elapsed_time, elapsed_time_len, len;
394 
395  if (dreq != NULL) {
396  elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time;
397  tstamp_echo = htonl(dreq->dreq_timestamp_echo);
398  dreq->dreq_timestamp_echo = 0;
399  } else {
400  elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time;
401  tstamp_echo = htonl(dp->dccps_timestamp_echo);
402  dp->dccps_timestamp_echo = 0;
403  }
404 
405  elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
406  len = 6 + elapsed_time_len;
407 
408  if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
409  return -1;
410 
411  DCCP_SKB_CB(skb)->dccpd_opt_len += len;
412 
413  to = skb_push(skb, len);
414  *to++ = DCCPO_TIMESTAMP_ECHO;
415  *to++ = len;
416 
417  memcpy(to, &tstamp_echo, 4);
418  to += 4;
419 
420  if (elapsed_time_len == 2) {
421  const __be16 var16 = htons((u16)elapsed_time);
422  memcpy(to, &var16, 2);
423  } else if (elapsed_time_len == 4) {
424  const __be32 var32 = htonl(elapsed_time);
425  memcpy(to, &var32, 4);
426  }
427 
428  return 0;
429 }
430 
431 static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
432 {
433  struct dccp_sock *dp = dccp_sk(sk);
434  struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
435  struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
436  const u16 buflen = dccp_ackvec_buflen(av);
437  /* Figure out how many options do we need to represent the ackvec */
438  const u8 nr_opts = DIV_ROUND_UP(buflen, DCCP_SINGLE_OPT_MAXLEN);
439  u16 len = buflen + 2 * nr_opts;
440  u8 i, nonce = 0;
441  const unsigned char *tail, *from;
442  unsigned char *to;
443 
444  if (dcb->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
445  DCCP_WARN("Lacking space for %u bytes on %s packet\n", len,
447  return -1;
448  }
449  /*
450  * Since Ack Vectors are variable-length, we can not always predict
451  * their size. To catch exception cases where the space is running out
452  * on the skb, a separate Sync is scheduled to carry the Ack Vector.
453  */
454  if (len > DCCPAV_MIN_OPTLEN &&
455  len + dcb->dccpd_opt_len + skb->len > dp->dccps_mss_cache) {
456  DCCP_WARN("No space left for Ack Vector (%u) on skb (%u+%u), "
457  "MPS=%u ==> reduce payload size?\n", len, skb->len,
458  dcb->dccpd_opt_len, dp->dccps_mss_cache);
459  dp->dccps_sync_scheduled = 1;
460  return 0;
461  }
462  dcb->dccpd_opt_len += len;
463 
464  to = skb_push(skb, len);
465  len = buflen;
466  from = av->av_buf + av->av_buf_head;
467  tail = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
468 
469  for (i = 0; i < nr_opts; ++i) {
470  int copylen = len;
471 
472  if (len > DCCP_SINGLE_OPT_MAXLEN)
473  copylen = DCCP_SINGLE_OPT_MAXLEN;
474 
475  /*
476  * RFC 4340, 12.2: Encode the Nonce Echo for this Ack Vector via
477  * its type; ack_nonce is the sum of all individual buf_nonce's.
478  */
479  nonce ^= av->av_buf_nonce[i];
480 
481  *to++ = DCCPO_ACK_VECTOR_0 + av->av_buf_nonce[i];
482  *to++ = copylen + 2;
483 
484  /* Check if buf_head wraps */
485  if (from + copylen > tail) {
486  const u16 tailsize = tail - from;
487 
488  memcpy(to, from, tailsize);
489  to += tailsize;
490  len -= tailsize;
491  copylen -= tailsize;
492  from = av->av_buf;
493  }
494 
495  memcpy(to, from, copylen);
496  from += copylen;
497  to += copylen;
498  len -= copylen;
499  }
500  /*
501  * Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340.
502  */
503  if (dccp_ackvec_update_records(av, dcb->dccpd_seq, nonce))
504  return -ENOBUFS;
505  return 0;
506 }
507 
514 {
516  return -1;
517 
518  DCCP_SKB_CB(skb)->dccpd_opt_len++;
519  *skb_push(skb, 1) = DCCPO_MANDATORY;
520  return 0;
521 }
522 
537  u8 *val, u8 len, bool repeat_first)
538 {
539  u8 tot_len, *to;
540 
541  /* take the `Feature' field and possible repetition into account */
542  if (len > (DCCP_SINGLE_OPT_MAXLEN - 2)) {
543  DCCP_WARN("length %u for feature %u too large\n", len, feat);
544  return -1;
545  }
546 
547  if (unlikely(val == NULL || len == 0))
548  len = repeat_first = false;
549  tot_len = 3 + repeat_first + len;
550 
551  if (DCCP_SKB_CB(skb)->dccpd_opt_len + tot_len > DCCP_MAX_OPT_LEN) {
552  DCCP_WARN("packet too small for feature %d option!\n", feat);
553  return -1;
554  }
555  DCCP_SKB_CB(skb)->dccpd_opt_len += tot_len;
556 
557  to = skb_push(skb, tot_len);
558  *to++ = type;
559  *to++ = tot_len;
560  *to++ = feat;
561 
562  if (repeat_first)
563  *to++ = *val;
564  if (len)
565  memcpy(to, val, len);
566  return 0;
567 }
568 
569 /* The length of all options needs to be a multiple of 4 (5.8) */
570 static void dccp_insert_option_padding(struct sk_buff *skb)
571 {
572  int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
573 
574  if (padding != 0) {
575  padding = 4 - padding;
576  memset(skb_push(skb, padding), 0, padding);
577  DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
578  }
579 }
580 
581 int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
582 {
583  struct dccp_sock *dp = dccp_sk(sk);
584 
585  DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
586 
587  if (dp->dccps_send_ndp_count && dccp_insert_option_ndp(sk, skb))
588  return -1;
589 
590  if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA) {
591 
592  /* Feature Negotiation */
593  if (dccp_feat_insert_opts(dp, NULL, skb))
594  return -1;
595 
596  if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST) {
597  /*
598  * Obtain RTT sample from Request/Response exchange.
599  * This is currently used for TFRC initialisation.
600  */
601  if (dccp_insert_option_timestamp(skb))
602  return -1;
603 
604  } else if (dccp_ackvec_pending(sk) &&
605  dccp_insert_option_ackvec(sk, skb)) {
606  return -1;
607  }
608  }
609 
610  if (dp->dccps_hc_rx_insert_options) {
611  if (ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb))
612  return -1;
614  }
615 
616  if (dp->dccps_timestamp_echo != 0 &&
617  dccp_insert_option_timestamp_echo(dp, NULL, skb))
618  return -1;
619 
620  dccp_insert_option_padding(skb);
621  return 0;
622 }
623 
624 int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb)
625 {
626  DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
627 
628  if (dccp_feat_insert_opts(NULL, dreq, skb))
629  return -1;
630 
631  /* Obtain RTT sample from Response/Ack exchange (used by TFRC). */
632  if (dccp_insert_option_timestamp(skb))
633  return -1;
634 
635  if (dreq->dreq_timestamp_echo != 0 &&
636  dccp_insert_option_timestamp_echo(NULL, dreq, skb))
637  return -1;
638 
639  dccp_insert_option_padding(skb);
640  return 0;
641 }