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Linux/net/dccp/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 <aris@cathedrallabs.org>
  6  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
  7  *  Copyright (c) 2005 Ian McDonald <ian.mcdonald@jandi.co.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/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 
 46 /**
 47  * dccp_parse_options  -  Parse DCCP options present in @skb
 48  * @sk: client|server|listening dccp socket (when @dreq != NULL)
 49  * @dreq: request socket to use during connection setup, or NULL
 50  */
 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;
123                 case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R:
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);
149                                 dreq->dreq_timestamp_time = dccp_timestamp();
150                         } else {
151                                 opt_recv->dccpor_timestamp =
152                                         dp->dccps_timestamp_echo = ntohl(opt_val);
153                                 dp->dccps_timestamp_time = dccp_timestamp();
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;
162                 case DCCPO_TIMESTAMP_ECHO:
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;
217                 case DCCPO_MIN_RX_CCID_SPECIFIC ... DCCPO_MAX_RX_CCID_SPECIFIC:
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                          */
232                 case DCCPO_MIN_TX_CCID_SPECIFIC ... DCCPO_MAX_TX_CCID_SPECIFIC:
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:
256         DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
257         rc = DCCP_RESET_CODE_OPTION_ERROR;
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 
267 EXPORT_SYMBOL_GPL(dccp_parse_options);
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 
310 EXPORT_SYMBOL_GPL(dccp_insert_option);
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 static int dccp_insert_option_timestamp(struct sk_buff *skb)
347 {
348         __be32 now = htonl(dccp_timestamp());
349         /* yes this will overflow but that is the point as we want a
350          * 10 usec 32 bit timer which mean it wraps every 11.9 hours */
351 
352         return dccp_insert_option(skb, DCCPO_TIMESTAMP, &now, sizeof(now));
353 }
354 
355 static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
356                                              struct dccp_request_sock *dreq,
357                                              struct sk_buff *skb)
358 {
359         __be32 tstamp_echo;
360         unsigned char *to;
361         u32 elapsed_time, elapsed_time_len, len;
362 
363         if (dreq != NULL) {
364                 elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time;
365                 tstamp_echo  = htonl(dreq->dreq_timestamp_echo);
366                 dreq->dreq_timestamp_echo = 0;
367         } else {
368                 elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time;
369                 tstamp_echo  = htonl(dp->dccps_timestamp_echo);
370                 dp->dccps_timestamp_echo = 0;
371         }
372 
373         elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
374         len = 6 + elapsed_time_len;
375 
376         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
377                 return -1;
378 
379         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
380 
381         to    = skb_push(skb, len);
382         *to++ = DCCPO_TIMESTAMP_ECHO;
383         *to++ = len;
384 
385         memcpy(to, &tstamp_echo, 4);
386         to += 4;
387 
388         if (elapsed_time_len == 2) {
389                 const __be16 var16 = htons((u16)elapsed_time);
390                 memcpy(to, &var16, 2);
391         } else if (elapsed_time_len == 4) {
392                 const __be32 var32 = htonl(elapsed_time);
393                 memcpy(to, &var32, 4);
394         }
395 
396         return 0;
397 }
398 
399 static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
400 {
401         struct dccp_sock *dp = dccp_sk(sk);
402         struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
403         struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
404         const u16 buflen = dccp_ackvec_buflen(av);
405         /* Figure out how many options do we need to represent the ackvec */
406         const u8 nr_opts = DIV_ROUND_UP(buflen, DCCP_SINGLE_OPT_MAXLEN);
407         u16 len = buflen + 2 * nr_opts;
408         u8 i, nonce = 0;
409         const unsigned char *tail, *from;
410         unsigned char *to;
411 
412         if (dcb->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
413                 DCCP_WARN("Lacking space for %u bytes on %s packet\n", len,
414                           dccp_packet_name(dcb->dccpd_type));
415                 return -1;
416         }
417         /*
418          * Since Ack Vectors are variable-length, we can not always predict
419          * their size. To catch exception cases where the space is running out
420          * on the skb, a separate Sync is scheduled to carry the Ack Vector.
421          */
422         if (len > DCCPAV_MIN_OPTLEN &&
423             len + dcb->dccpd_opt_len + skb->len > dp->dccps_mss_cache) {
424                 DCCP_WARN("No space left for Ack Vector (%u) on skb (%u+%u), "
425                           "MPS=%u ==> reduce payload size?\n", len, skb->len,
426                           dcb->dccpd_opt_len, dp->dccps_mss_cache);
427                 dp->dccps_sync_scheduled = 1;
428                 return 0;
429         }
430         dcb->dccpd_opt_len += len;
431 
432         to   = skb_push(skb, len);
433         len  = buflen;
434         from = av->av_buf + av->av_buf_head;
435         tail = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
436 
437         for (i = 0; i < nr_opts; ++i) {
438                 int copylen = len;
439 
440                 if (len > DCCP_SINGLE_OPT_MAXLEN)
441                         copylen = DCCP_SINGLE_OPT_MAXLEN;
442 
443                 /*
444                  * RFC 4340, 12.2: Encode the Nonce Echo for this Ack Vector via
445                  * its type; ack_nonce is the sum of all individual buf_nonce's.
446                  */
447                 nonce ^= av->av_buf_nonce[i];
448 
449                 *to++ = DCCPO_ACK_VECTOR_0 + av->av_buf_nonce[i];
450                 *to++ = copylen + 2;
451 
452                 /* Check if buf_head wraps */
453                 if (from + copylen > tail) {
454                         const u16 tailsize = tail - from;
455 
456                         memcpy(to, from, tailsize);
457                         to      += tailsize;
458                         len     -= tailsize;
459                         copylen -= tailsize;
460                         from    = av->av_buf;
461                 }
462 
463                 memcpy(to, from, copylen);
464                 from += copylen;
465                 to   += copylen;
466                 len  -= copylen;
467         }
468         /*
469          * Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340.
470          */
471         if (dccp_ackvec_update_records(av, dcb->dccpd_seq, nonce))
472                 return -ENOBUFS;
473         return 0;
474 }
475 
476 /**
477  * dccp_insert_option_mandatory  -  Mandatory option (5.8.2)
478  * Note that since we are using skb_push, this function needs to be called
479  * _after_ inserting the option it is supposed to influence (stack order).
480  */
481 int dccp_insert_option_mandatory(struct sk_buff *skb)
482 {
483         if (DCCP_SKB_CB(skb)->dccpd_opt_len >= DCCP_MAX_OPT_LEN)
484                 return -1;
485 
486         DCCP_SKB_CB(skb)->dccpd_opt_len++;
487         *skb_push(skb, 1) = DCCPO_MANDATORY;
488         return 0;
489 }
490 
491 /**
492  * dccp_insert_fn_opt  -  Insert single Feature-Negotiation option into @skb
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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