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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 int sysctl_dccp_feat_sequence_window = DCCPF_INITIAL_SEQUENCE_WINDOW;
  27 int sysctl_dccp_feat_rx_ccid          = DCCPF_INITIAL_CCID;
  28 int sysctl_dccp_feat_tx_ccid          = DCCPF_INITIAL_CCID;
  29 int sysctl_dccp_feat_send_ack_vector = DCCPF_INITIAL_SEND_ACK_VECTOR;
  30
  31 u64 dccp_decode_value_var(const u8 *bf, const u8 len)
  32 {
  33         u64 value = 0;
  34
  35         if (len >= DCCP_OPTVAL_MAXLEN)
  36                 value += ((u64)*bf++) << 40;
  37         if (len > 4)
  38                 value += ((u64)*bf++) << 32;
  39         if (len > 3)
  40                 value += ((u64)*bf++) << 24;
  41         if (len > 2)
  42                 value += ((u64)*bf++) << 16;
  43         if (len > 1)
  44                 value += ((u64)*bf++) << 8;
  45         if (len > 0)
  46                 value += *bf;
  47
  48         return value;
  49 }
  50
  51 /**
  52  * dccp_parse_options  -  Parse DCCP options present in @skb
  53  * @sk: client|server|listening dccp socket (when @dreq != NULL)
  54  * @dreq: request socket to use during connection setup, or NULL
  55  */
  56 int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
  57                        struct sk_buff *skb)
  58 {
  59         struct dccp_sock *dp = dccp_sk(sk);
  60         const struct dccp_hdr *dh = dccp_hdr(skb);
  61         const u8 pkt_type = DCCP_SKB_CB(skb)->dccpd_type;
  62         u64 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
  63         unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
  64         unsigned char *opt_ptr = options;
  65         const unsigned char *opt_end = (unsigned char *)dh +
  66                                         (dh->dccph_doff * 4);
  67         struct dccp_options_received *opt_recv = &dp->dccps_options_received;
  68         unsigned char opt, len;
  69         unsigned char *uninitialized_var(value);
  70         u32 elapsed_time;
  71         __be32 opt_val;
  72         int rc;
  73         int mandatory = 0;
  74
  75         memset(opt_recv, 0, sizeof(*opt_recv));
  76
  77         opt = len = 0;
  78         while (opt_ptr != opt_end) {
  79                 opt   = *opt_ptr++;
  80                 len   = 0;
  81                 value = NULL;
  82
  83                 /* Check if this isn't a single byte option */
  84                 if (opt > DCCPO_MAX_RESERVED) {
  85                         if (opt_ptr == opt_end)
  86                                 goto out_nonsensical_length;
  87
  88                         len = *opt_ptr++;
  89                         if (len < 2)
  90                                 goto out_nonsensical_length;
  91                         /*
  92                          * Remove the type and len fields, leaving
  93                          * just the value size
  94                          */
  95                         len     -= 2;
  96                         value   = opt_ptr;
  97                         opt_ptr += len;
  98
  99                         if (opt_ptr > opt_end)
 100                                 goto out_nonsensical_length;
 101                 }
 102
 103                 /*
 104                  * CCID-Specific Options (from RFC 4340, sec. 10.3):
 105                  *
 106                  * Option numbers 128 through 191 are for options sent from the
 107                  * HC-Sender to the HC-Receiver; option numbers 192 through 255
 108                  * are for options sent from the HC-Receiver to the HC-Sender.
 109                  *
 110                  * CCID-specific options are ignored during connection setup, as
 111                  * negotiation may still be in progress (see RFC 4340, 10.3).
 112                  * The same applies to Ack Vectors, as these depend on the CCID.
 113                  *
 114                  */
 115                 if (dreq != NULL && (opt >= 128 ||
 116                     opt == DCCPO_ACK_VECTOR_0 || opt == DCCPO_ACK_VECTOR_1))
 117                         goto ignore_option;
 118
 119                 switch (opt) {
 120                 case DCCPO_PADDING:
 121                         break;
 122                 case DCCPO_MANDATORY:
 123                         if (mandatory)
 124                                 goto out_invalid_option;
 125                         if (pkt_type != DCCP_PKT_DATA)
 126                                 mandatory = 1;
 127                         break;
 128                 case DCCPO_NDP_COUNT:
 129                         if (len > 6)
 130                                 goto out_invalid_option;
 131
 132                         opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
 133                         dccp_pr_debug("%s opt: NDP count=%llu\n", dccp_role(sk),
 134                                       (unsigned long long)opt_recv->dccpor_ndp);
 135                         break;
 136                 case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R:
 137                         if (pkt_type == DCCP_PKT_DATA)      /* RFC 4340, 6 */
 138                                 break;
 139                         rc = dccp_feat_parse_options(sk, dreq, mandatory, opt,
 140                                                     *value, value + 1, len - 1);
 141                         if (rc)
 142                                 goto out_featneg_failed;
 143                         break;
 144                 case DCCPO_ACK_VECTOR_0:
 145                 case DCCPO_ACK_VECTOR_1:
 146                         if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
 147                                 break;
 148
 149                         if (dccp_msk(sk)->dccpms_send_ack_vector &&
 150                             dccp_ackvec_parse(sk, skb, &ackno, opt, value, len))
 151                                 goto out_invalid_option;
 152                         break;
 153                 case DCCPO_TIMESTAMP:
 154                         if (len != 4)
 155                                 goto out_invalid_option;
 156                         /*
 157                          * RFC 4340 13.1: "The precise time corresponding to
 158                          * Timestamp Value zero is not specified". We use
 159                          * zero to indicate absence of a meaningful timestamp.
 160                          */
 161                         opt_val = get_unaligned((__be32 *)value);
 162                         if (unlikely(opt_val == 0)) {
 163                                 DCCP_WARN("Timestamp with zero value\n");
 164                                 break;
 165                         }
 166
 167                         if (dreq != NULL) {
 168                                 dreq->dreq_timestamp_echo = ntohl(opt_val);
 169                                 dreq->dreq_timestamp_time = dccp_timestamp();
 170                         } else {
 171                                 opt_recv->dccpor_timestamp =
 172                                         dp->dccps_timestamp_echo = ntohl(opt_val);
 173                                 dp->dccps_timestamp_time = dccp_timestamp();
 174                         }
 175                         dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n",
 176                                       dccp_role(sk), ntohl(opt_val),
 177                                       (unsigned long long)
 178                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
 179                         break;
 180                 case DCCPO_TIMESTAMP_ECHO:
 181                         if (len != 4 && len != 6 && len != 8)
 182                                 goto out_invalid_option;
 183
 184                         opt_val = get_unaligned((__be32 *)value);
 185                         opt_recv->dccpor_timestamp_echo = ntohl(opt_val);
 186
 187                         dccp_pr_debug("%s rx opt: TIMESTAMP_ECHO=%u, len=%d, "
 188                                       "ackno=%llu", dccp_role(sk),
 189                                       opt_recv->dccpor_timestamp_echo,
 190                                       len + 2,
 191                                       (unsigned long long)
 192                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
 193
 194                         value += 4;
 195
 196                         if (len == 4) {         /* no elapsed time included */
 197                                 dccp_pr_debug_cat("\n");
 198                                 break;
 199                         }
 200
 201                         if (len == 6) {         /* 2-byte elapsed time */
 202                                 __be16 opt_val2 = get_unaligned((__be16 *)value);
 203                                 elapsed_time = ntohs(opt_val2);
 204                         } else {                /* 4-byte elapsed time */
 205                                 opt_val = get_unaligned((__be32 *)value);
 206                                 elapsed_time = ntohl(opt_val);
 207                         }
 208
 209                         dccp_pr_debug_cat(", ELAPSED_TIME=%u\n", elapsed_time);
 210
 211                         /* Give precedence to the biggest ELAPSED_TIME */
 212                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
 213                                 opt_recv->dccpor_elapsed_time = elapsed_time;
 214                         break;
 215                 case DCCPO_ELAPSED_TIME:
 216                         if (dccp_packet_without_ack(skb))   /* RFC 4340, 13.2 */
 217                                 break;
 218
 219                         if (len == 2) {
 220                                 __be16 opt_val2 = get_unaligned((__be16 *)value);
 221                                 elapsed_time = ntohs(opt_val2);
 222                         } else if (len == 4) {
 223                                 opt_val = get_unaligned((__be32 *)value);
 224                                 elapsed_time = ntohl(opt_val);
 225                         } else {
 226                                 goto out_invalid_option;
 227                         }
 228
 229                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
 230                                 opt_recv->dccpor_elapsed_time = elapsed_time;
 231
 232                         dccp_pr_debug("%s rx opt: ELAPSED_TIME=%d\n",
 233                                       dccp_role(sk), elapsed_time);
 234                         break;
 235                 case 128 ... 191: {
 236                         const u16 idx = value - options;
 237
 238                         if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
 239                                                      opt, len, idx,
 240                                                      value) != 0)
 241                                 goto out_invalid_option;
 242                 }
 243                         break;
 244                 case 192 ... 255: {
 245                         const u16 idx = value - options;
 246
 247                         if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
 248                                                      opt, len, idx,
 249                                                      value) != 0)
 250                                 goto out_invalid_option;
 251                 }
 252                         break;
 253                 default:
 254                         DCCP_CRIT("DCCP(%p): option %d(len=%d) not "
 255                                   "implemented, ignoring", sk, opt, len);
 256                         break;
 257                 }
 258 ignore_option:
 259                 if (opt != DCCPO_MANDATORY)
 260                         mandatory = 0;
 261         }
 262
 263         /* mandatory was the last byte in option list -> reset connection */
 264         if (mandatory)
 265                 goto out_invalid_option;
 266
 267 out_nonsensical_length:
 268         /* RFC 4340, 5.8: ignore option and all remaining option space */
 269         return 0;
 270
 271 out_invalid_option:
 272         DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
 273         rc = DCCP_RESET_CODE_OPTION_ERROR;
 274 out_featneg_failed:
 275         DCCP_WARN("DCCP(%p): Option %d (len=%d) error=%u\n", sk, opt, len, rc);
 276         DCCP_SKB_CB(skb)->dccpd_reset_code = rc;
 277         DCCP_SKB_CB(skb)->dccpd_reset_data[0] = opt;
 278         DCCP_SKB_CB(skb)->dccpd_reset_data[1] = len > 0 ? value[0] : 0;
 279         DCCP_SKB_CB(skb)->dccpd_reset_data[2] = len > 1 ? value[1] : 0;
 280         return -1;
 281 }
 282
 283 EXPORT_SYMBOL_GPL(dccp_parse_options);
 284
 285 void dccp_encode_value_var(const u64 value, u8 *to, const u8 len)
 286 {
 287         if (len >= DCCP_OPTVAL_MAXLEN)
 288                 *to++ = (value & 0xFF0000000000ull) >> 40;
 289         if (len > 4)
 290                 *to++ = (value & 0xFF00000000ull) >> 32;
 291         if (len > 3)
 292                 *to++ = (value & 0xFF000000) >> 24;
 293         if (len > 2)
 294                 *to++ = (value & 0xFF0000) >> 16;
 295         if (len > 1)
 296                 *to++ = (value & 0xFF00) >> 8;
 297         if (len > 0)
 298                 *to++ = (value & 0xFF);
 299 }
 300
 301 static inline u8 dccp_ndp_len(const u64 ndp)
 302 {
 303         if (likely(ndp <= 0xFF))
 304                 return 1;
 305         return likely(ndp <= USHORT_MAX) ? 2 : (ndp <= UINT_MAX ? 4 : 6);
 306 }
 307
 308 int dccp_insert_option(struct sock *sk, struct sk_buff *skb,
 309                         const unsigned char option,
 310                         const void *value, const unsigned char len)
 311 {
 312         unsigned char *to;
 313
 314         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 2 > DCCP_MAX_OPT_LEN)
 315                 return -1;
 316
 317         DCCP_SKB_CB(skb)->dccpd_opt_len += len + 2;
 318
 319         to    = skb_push(skb, len + 2);
 320         *to++ = option;
 321         *to++ = len + 2;
 322
 323         memcpy(to, value, len);
 324         return 0;
 325 }
 326
 327 EXPORT_SYMBOL_GPL(dccp_insert_option);
 328
 329 static int dccp_insert_option_ndp(struct sock *sk, struct sk_buff *skb)
 330 {
 331         struct dccp_sock *dp = dccp_sk(sk);
 332         u64 ndp = dp->dccps_ndp_count;
 333
 334         if (dccp_non_data_packet(skb))
 335                 ++dp->dccps_ndp_count;
 336         else
 337                 dp->dccps_ndp_count = 0;
 338
 339         if (ndp > 0) {
 340                 unsigned char *ptr;
 341                 const int ndp_len = dccp_ndp_len(ndp);
 342                 const int len = ndp_len + 2;
 343
 344                 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
 345                         return -1;
 346
 347                 DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 348
 349                 ptr = skb_push(skb, len);
 350                 *ptr++ = DCCPO_NDP_COUNT;
 351                 *ptr++ = len;
 352                 dccp_encode_value_var(ndp, ptr, ndp_len);
 353         }
 354
 355         return 0;
 356 }
 357
 358 static inline int dccp_elapsed_time_len(const u32 elapsed_time)
 359 {
 360         return elapsed_time == 0 ? 0 : elapsed_time <= 0xFFFF ? 2 : 4;
 361 }
 362
 363 int dccp_insert_option_elapsed_time(struct sock *sk, struct sk_buff *skb,
 364                                     u32 elapsed_time)
 365 {
 366         const int elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
 367         const int len = 2 + elapsed_time_len;
 368         unsigned char *to;
 369
 370         if (elapsed_time_len == 0)
 371                 return 0;
 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_ELAPSED_TIME;
 380         *to++ = len;
 381
 382         if (elapsed_time_len == 2) {
 383                 const __be16 var16 = htons((u16)elapsed_time);
 384                 memcpy(to, &var16, 2);
 385         } else {
 386                 const __be32 var32 = htonl(elapsed_time);
 387                 memcpy(to, &var32, 4);
 388         }
 389
 390         return 0;
 391 }
 392
 393 EXPORT_SYMBOL_GPL(dccp_insert_option_elapsed_time);
 394
 395 int dccp_insert_option_timestamp(struct sock *sk, struct sk_buff *skb)
 396 {
 397         __be32 now = htonl(dccp_timestamp());
 398         /* yes this will overflow but that is the point as we want a
 399          * 10 usec 32 bit timer which mean it wraps every 11.9 hours */
 400
 401         return dccp_insert_option(sk, skb, DCCPO_TIMESTAMP, &now, sizeof(now));
 402 }
 403
 404 EXPORT_SYMBOL_GPL(dccp_insert_option_timestamp);
 405
 406 static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
 407                                              struct dccp_request_sock *dreq,
 408                                              struct sk_buff *skb)
 409 {
 410         __be32 tstamp_echo;
 411         unsigned char *to;
 412         u32 elapsed_time, elapsed_time_len, len;
 413
 414         if (dreq != NULL) {
 415                 elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time;
 416                 tstamp_echo  = htonl(dreq->dreq_timestamp_echo);
 417                 dreq->dreq_timestamp_echo = 0;
 418         } else {
 419                 elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time;
 420                 tstamp_echo  = htonl(dp->dccps_timestamp_echo);
 421                 dp->dccps_timestamp_echo = 0;
 422         }
 423
 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                 return -1;
 429
 430         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 431
 432         to    = skb_push(skb, len);
 433         *to++ = DCCPO_TIMESTAMP_ECHO;
 434         *to++ = len;
 435
 436         memcpy(to, &tstamp_echo, 4);
 437         to += 4;
 438
 439         if (elapsed_time_len == 2) {
 440                 const __be16 var16 = htons((u16)elapsed_time);
 441                 memcpy(to, &var16, 2);
 442         } else if (elapsed_time_len == 4) {
 443                 const __be32 var32 = htonl(elapsed_time);
 444                 memcpy(to, &var32, 4);
 445         }
 446
 447         return 0;
 448 }
 449
 450 /**
 451  * dccp_insert_option_mandatory  -  Mandatory option (5.8.2)
 452  * Note that since we are using skb_push, this function needs to be called
 453  * _after_ inserting the option it is supposed to influence (stack order).
 454  */
 455 int dccp_insert_option_mandatory(struct sk_buff *skb)
 456 {
 457         if (DCCP_SKB_CB(skb)->dccpd_opt_len >= DCCP_MAX_OPT_LEN)
 458                 return -1;
 459
 460         DCCP_SKB_CB(skb)->dccpd_opt_len++;
 461         *skb_push(skb, 1) = DCCPO_MANDATORY;
 462         return 0;
 463 }
 464
 465 /**
 466  * dccp_insert_fn_opt  -  Insert single Feature-Negotiation option into @skb
 467  * @type: %DCCPO_CHANGE_L, %DCCPO_CHANGE_R, %DCCPO_CONFIRM_L, %DCCPO_CONFIRM_R
 468  * @feat: one out of %dccp_feature_numbers
 469  * @val: NN value or SP array (preferred element first) to copy
 470  * @len: true length of @val in bytes (excluding first element repetition)
 471  * @repeat_first: whether to copy the first element of @val twice
 472  * The last argument is used to construct Confirm options, where the preferred
 473  * value and the preference list appear separately (RFC 4340, 6.3.1). Preference
 474  * lists are kept such that the preferred entry is always first, so we only need
 475  * to copy twice, and avoid the overhead of cloning into a bigger array.
 476  */
 477 int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
 478                        u8 *val, u8 len, bool repeat_first)
 479 {
 480         u8 tot_len, *to;
 481
 482         /* take the `Feature' field and possible repetition into account */
 483         if (len > (DCCP_SINGLE_OPT_MAXLEN - 2)) {
 484                 DCCP_WARN("length %u for feature %u too large\n", len, feat);
 485                 return -1;
 486         }
 487
 488         if (unlikely(val == NULL || len == 0))
 489                 len = repeat_first = 0;
 490         tot_len = 3 + repeat_first + len;
 491
 492         if (DCCP_SKB_CB(skb)->dccpd_opt_len + tot_len > DCCP_MAX_OPT_LEN) {
 493                 DCCP_WARN("packet too small for feature %d option!\n", feat);
 494                 return -1;
 495         }
 496         DCCP_SKB_CB(skb)->dccpd_opt_len += tot_len;
 497
 498         to    = skb_push(skb, tot_len);
 499         *to++ = type;
 500         *to++ = tot_len;
 501         *to++ = feat;
 502
 503         if (repeat_first)
 504                 *to++ = *val;
 505         if (len)
 506                 memcpy(to, val, len);
 507
 508         dccp_pr_debug("%s(%s (%d), ...), length %d\n",
 509                       dccp_feat_typename(type),
 510                       dccp_feat_name(feat), feat, len);
 511         return 0;
 512 }
 513
 514 /* The length of all options needs to be a multiple of 4 (5.8) */
 515 static void dccp_insert_option_padding(struct sk_buff *skb)
 516 {
 517         int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
 518
 519         if (padding != 0) {
 520                 padding = 4 - padding;
 521                 memset(skb_push(skb, padding), 0, padding);
 522                 DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
 523         }
 524 }
 525
 526 int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
 527 {
 528         struct dccp_sock *dp = dccp_sk(sk);
 529         struct dccp_minisock *dmsk = dccp_msk(sk);
 530
 531         DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
 532
 533         if (dp->dccps_send_ndp_count && dccp_insert_option_ndp(sk, skb))
 534                 return -1;
 535
 536         if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA) {
 537
 538                 /* Feature Negotiation */
 539                 if (dccp_feat_insert_opts(dp, NULL, skb))
 540                         return -1;
 541
 542                 if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST) {
 543                         /*
 544                          * Obtain RTT sample from Request/Response exchange.
 545                          * This is currently used in CCID 3 initialisation.
 546                          */
 547                         if (dccp_insert_option_timestamp(sk, skb))
 548                                 return -1;
 549
 550                 } else if (dmsk->dccpms_send_ack_vector &&
 551                            dccp_ackvec_pending(dp->dccps_hc_rx_ackvec) &&
 552                            dccp_insert_option_ackvec(sk, skb)) {
 553                                 return -1;
 554                 }
 555         }
 556
 557         if (dp->dccps_hc_rx_insert_options) {
 558                 if (ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb))
 559                         return -1;
 560                 dp->dccps_hc_rx_insert_options = 0;
 561         }
 562
 563         if (dp->dccps_timestamp_echo != 0 &&
 564             dccp_insert_option_timestamp_echo(dp, NULL, skb))
 565                 return -1;
 566
 567         dccp_insert_option_padding(skb);
 568         return 0;
 569 }
 570
 571 int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb)
 572 {
 573         DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
 574
 575         if (dccp_feat_insert_opts(NULL, dreq, skb))
 576                 return -1;
 577
 578         if (dreq->dreq_timestamp_echo != 0 &&
 579             dccp_insert_option_timestamp_echo(NULL, dreq, skb))
 580                 return -1;
 581
 582         dccp_insert_option_padding(skb);
 583         return 0;
 584 }