net/dccp/options.c

   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 int dccp_feat_default_sequence_window = DCCPF_INITIAL_SEQUENCE_WINDOW;
  27 int dccp_feat_default_rx_ccid         = DCCPF_INITIAL_CCID;
  28 int dccp_feat_default_tx_ccid         = DCCPF_INITIAL_CCID;
  29 int dccp_feat_default_ack_ratio       = DCCPF_INITIAL_ACK_RATIO;
  30 int dccp_feat_default_send_ack_vector = DCCPF_INITIAL_SEND_ACK_VECTOR;
  31 int dccp_feat_default_send_ndp_count  = DCCPF_INITIAL_SEND_NDP_COUNT;
  32
  33 void dccp_options_init(struct dccp_options *dccpo)
  34 {
  35         dccpo->dccpo_sequence_window = dccp_feat_default_sequence_window;
  36         dccpo->dccpo_rx_ccid         = dccp_feat_default_rx_ccid;
  37         dccpo->dccpo_tx_ccid         = dccp_feat_default_tx_ccid;
  38         dccpo->dccpo_ack_ratio       = dccp_feat_default_ack_ratio;
  39         dccpo->dccpo_send_ack_vector = dccp_feat_default_send_ack_vector;
  40         dccpo->dccpo_send_ndp_count  = dccp_feat_default_send_ndp_count;
  41 }
  42
  43 static u32 dccp_decode_value_var(const unsigned char *bf, const u8 len)
  44 {
  45         u32 value = 0;
  46
  47         if (len > 3)
  48                 value += *bf++ << 24;
  49         if (len > 2)
  50                 value += *bf++ << 16;
  51         if (len > 1)
  52                 value += *bf++ << 8;
  53         if (len > 0)
  54                 value += *bf;
  55
  56         return value;
  57 }
  58
  59 int dccp_parse_options(struct sock *sk, struct sk_buff *skb)
  60 {
  61         struct dccp_sock *dp = dccp_sk(sk);
  62 #ifdef CONFIG_IP_DCCP_DEBUG
  63         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
  64                                         "CLIENT rx opt: " : "server rx opt: ";
  65 #endif
  66         const struct dccp_hdr *dh = dccp_hdr(skb);
  67         const u8 pkt_type = DCCP_SKB_CB(skb)->dccpd_type;
  68         unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
  69         unsigned char *opt_ptr = options;
  70         const unsigned char *opt_end = (unsigned char *)dh +
  71                                         (dh->dccph_doff * 4);
  72         struct dccp_options_received *opt_recv = &dp->dccps_options_received;
  73         unsigned char opt, len;
  74         unsigned char *value;
  75         u32 elapsed_time;
  76         int rc;
  77         int mandatory = 0;
  78
  79         memset(opt_recv, 0, sizeof(*opt_recv));
  80
  81         while (opt_ptr != opt_end) {
  82                 opt   = *opt_ptr++;
  83                 len   = 0;
  84                 value = NULL;
  85
  86                 /* Check if this isn't a single byte option */
  87                 if (opt > DCCPO_MAX_RESERVED) {
  88                         if (opt_ptr == opt_end)
  89                                 goto out_invalid_option;
  90
  91                         len = *opt_ptr++;
  92                         if (len < 3)
  93                                 goto out_invalid_option;
  94                         /*
  95                          * Remove the type and len fields, leaving
  96                          * just the value size
  97                          */
  98                         len     -= 2;
  99                         value   = opt_ptr;
 100                         opt_ptr += len;
 101
 102                         if (opt_ptr > opt_end)
 103                                 goto out_invalid_option;
 104                 }
 105
 106                 switch (opt) {
 107                 case DCCPO_PADDING:
 108                         break;
 109                 case DCCPO_MANDATORY:
 110                         if (mandatory)
 111                                 goto out_invalid_option;
 112                         mandatory = 1;
 113                         break;
 114                 case DCCPO_NDP_COUNT:
 115                         if (len > 3)
 116                                 goto out_invalid_option;
 117
 118                         opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
 119                         dccp_pr_debug("%sNDP count=%d\n", debug_prefix,
 120                                       opt_recv->dccpor_ndp);
 121                         break;
 122                 case DCCPO_CHANGE_L:
 123                         /* fall through */
 124                 case DCCPO_CHANGE_R:
 125                         if (len < 2)
 126                                 goto out_invalid_option;
 127                         rc = dccp_feat_change_recv(sk, opt, *value, value + 1,
 128                                                    len - 1);
 129                         /*
 130                          * When there is a change error, change_recv is
 131                          * responsible for dealing with it.  i.e. reply with an
 132                          * empty confirm.
 133                          * If the change was mandatory, then we need to die.
 134                          */
 135                         if (rc && mandatory)
 136                                 goto out_invalid_option;
 137                         break;
 138                 case DCCPO_CONFIRM_L:
 139                         /* fall through */
 140                 case DCCPO_CONFIRM_R:
 141                         if (len < 2)
 142                                 goto out_invalid_option;
 143                         if (dccp_feat_confirm_recv(sk, opt, *value,
 144                                                    value + 1, len - 1))
 145                                 goto out_invalid_option;
 146                         break;
 147                 case DCCPO_ACK_VECTOR_0:
 148                 case DCCPO_ACK_VECTOR_1:
 149                         if (pkt_type == DCCP_PKT_DATA)
 150                                 continue;
 151
 152                         if (dp->dccps_options.dccpo_send_ack_vector &&
 153                             dccp_ackvec_parse(sk, skb, opt, value, len))
 154                                 goto out_invalid_option;
 155                         break;
 156                 case DCCPO_TIMESTAMP:
 157                         if (len != 4)
 158                                 goto out_invalid_option;
 159
 160                         opt_recv->dccpor_timestamp = ntohl(*(__be32 *)value);
 161
 162                         dp->dccps_timestamp_echo = opt_recv->dccpor_timestamp;
 163                         dccp_timestamp(sk, &dp->dccps_timestamp_time);
 164
 165                         dccp_pr_debug("%sTIMESTAMP=%u, ackno=%llu\n",
 166                                       debug_prefix, opt_recv->dccpor_timestamp,
 167                                       (unsigned long long)
 168                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
 169                         break;
 170                 case DCCPO_TIMESTAMP_ECHO:
 171                         if (len != 4 && len != 6 && len != 8)
 172                                 goto out_invalid_option;
 173
 174                         opt_recv->dccpor_timestamp_echo = ntohl(*(__be32 *)value);
 175
 176                         dccp_pr_debug("%sTIMESTAMP_ECHO=%u, len=%d, ackno=%llu, ",
 177                                       debug_prefix,
 178                                       opt_recv->dccpor_timestamp_echo,
 179                                       len + 2,
 180                                       (unsigned long long)
 181                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
 182
 183
 184                         if (len == 4)
 185                                 break;
 186
 187                         if (len == 6)
 188                                 elapsed_time = ntohs(*(__be16 *)(value + 4));
 189                         else
 190                                 elapsed_time = ntohl(*(__be32 *)(value + 4));
 191
 192                         /* Give precedence to the biggest ELAPSED_TIME */
 193                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
 194                                 opt_recv->dccpor_elapsed_time = elapsed_time;
 195                         break;
 196                 case DCCPO_ELAPSED_TIME:
 197                         if (len != 2 && len != 4)
 198                                 goto out_invalid_option;
 199
 200                         if (pkt_type == DCCP_PKT_DATA)
 201                                 continue;
 202
 203                         if (len == 2)
 204                                 elapsed_time = ntohs(*(__be16 *)value);
 205                         else
 206                                 elapsed_time = ntohl(*(__be32 *)value);
 207
 208                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
 209                                 opt_recv->dccpor_elapsed_time = elapsed_time;
 210
 211                         dccp_pr_debug("%sELAPSED_TIME=%d\n", debug_prefix,
 212                                       elapsed_time);
 213                         break;
 214                         /*
 215                          * From draft-ietf-dccp-spec-11.txt:
 216                          *
 217                          *      Option numbers 128 through 191 are for
 218                          *      options sent from the HC-Sender to the
 219                          *      HC-Receiver; option numbers 192 through 255
 220                          *      are for options sent from the HC-Receiver to
 221                          *      the HC-Sender.
 222                          */
 223                 case 128 ... 191: {
 224                         const u16 idx = value - options;
 225
 226                         if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
 227                                                      opt, len, idx,
 228                                                      value) != 0)
 229                                 goto out_invalid_option;
 230                 }
 231                         break;
 232                 case 192 ... 255: {
 233                         const u16 idx = value - options;
 234
 235                         if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
 236                                                      opt, len, idx,
 237                                                      value) != 0)
 238                                 goto out_invalid_option;
 239                 }
 240                         break;
 241                 default:
 242                         pr_info("DCCP(%p): option %d(len=%d) not "
 243                                 "implemented, ignoring\n",
 244                                 sk, opt, len);
 245                         break;
 246                 }
 247
 248                 if (opt != DCCPO_MANDATORY)
 249                         mandatory = 0;
 250         }
 251
 252         return 0;
 253
 254 out_invalid_option:
 255         DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
 256         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_OPTION_ERROR;
 257         pr_info("DCCP(%p): invalid option %d, len=%d\n", sk, opt, len);
 258         return -1;
 259 }
 260
 261 static void dccp_encode_value_var(const u32 value, unsigned char *to,
 262                                   const unsigned int len)
 263 {
 264         if (len > 3)
 265                 *to++ = (value & 0xFF000000) >> 24;
 266         if (len > 2)
 267                 *to++ = (value & 0xFF0000) >> 16;
 268         if (len > 1)
 269                 *to++ = (value & 0xFF00) >> 8;
 270         if (len > 0)
 271                 *to++ = (value & 0xFF);
 272 }
 273
 274 static inline int dccp_ndp_len(const int ndp)
 275 {
 276         return likely(ndp <= 0xFF) ? 1 : ndp <= 0xFFFF ? 2 : 3;
 277 }
 278
 279 void dccp_insert_option(struct sock *sk, struct sk_buff *skb,
 280                         const unsigned char option,
 281                         const void *value, const unsigned char len)
 282 {
 283         unsigned char *to;
 284
 285         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 2 > DCCP_MAX_OPT_LEN) {
 286                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small to insert "
 287                                "%d option!\n", option);
 288                 return;
 289         }
 290
 291         DCCP_SKB_CB(skb)->dccpd_opt_len += len + 2;
 292
 293         to    = skb_push(skb, len + 2);
 294         *to++ = option;
 295         *to++ = len + 2;
 296
 297         memcpy(to, value, len);
 298 }
 299
 300 EXPORT_SYMBOL_GPL(dccp_insert_option);
 301
 302 static void dccp_insert_option_ndp(struct sock *sk, struct sk_buff *skb)
 303 {
 304         struct dccp_sock *dp = dccp_sk(sk);
 305         int ndp = dp->dccps_ndp_count;
 306
 307         if (dccp_non_data_packet(skb))
 308                 ++dp->dccps_ndp_count;
 309         else
 310                 dp->dccps_ndp_count = 0;
 311
 312         if (ndp > 0) {
 313                 unsigned char *ptr;
 314                 const int ndp_len = dccp_ndp_len(ndp);
 315                 const int len = ndp_len + 2;
 316
 317                 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
 318                         return;
 319
 320                 DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 321
 322                 ptr = skb_push(skb, len);
 323                 *ptr++ = DCCPO_NDP_COUNT;
 324                 *ptr++ = len;
 325                 dccp_encode_value_var(ndp, ptr, ndp_len);
 326         }
 327 }
 328
 329 static inline int dccp_elapsed_time_len(const u32 elapsed_time)
 330 {
 331         return elapsed_time == 0 ? 0 : elapsed_time <= 0xFFFF ? 2 : 4;
 332 }
 333
 334 void dccp_insert_option_elapsed_time(struct sock *sk,
 335                                      struct sk_buff *skb,
 336                                      u32 elapsed_time)
 337 {
 338 #ifdef CONFIG_IP_DCCP_DEBUG
 339         struct dccp_sock *dp = dccp_sk(sk);
 340         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
 341                                         "CLIENT TX opt: " : "server TX opt: ";
 342 #endif
 343         const int elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
 344         const int len = 2 + elapsed_time_len;
 345         unsigned char *to;
 346
 347         if (elapsed_time_len == 0)
 348                 return;
 349
 350         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
 351                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small to "
 352                                          "insert elapsed time!\n");
 353                 return;
 354         }
 355
 356         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 357
 358         to    = skb_push(skb, len);
 359         *to++ = DCCPO_ELAPSED_TIME;
 360         *to++ = len;
 361
 362         if (elapsed_time_len == 2) {
 363                 const __be16 var16 = htons((u16)elapsed_time);
 364                 memcpy(to, &var16, 2);
 365         } else {
 366                 const __be32 var32 = htonl(elapsed_time);
 367                 memcpy(to, &var32, 4);
 368         }
 369
 370         dccp_pr_debug("%sELAPSED_TIME=%u, len=%d, seqno=%llu\n",
 371                       debug_prefix, elapsed_time,
 372                       len,
 373                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 374 }
 375
 376 EXPORT_SYMBOL_GPL(dccp_insert_option_elapsed_time);
 377
 378 void dccp_timestamp(const struct sock *sk, struct timeval *tv)
 379 {
 380         const struct dccp_sock *dp = dccp_sk(sk);
 381
 382         do_gettimeofday(tv);
 383         tv->tv_sec  -= dp->dccps_epoch.tv_sec;
 384         tv->tv_usec -= dp->dccps_epoch.tv_usec;
 385
 386         while (tv->tv_usec < 0) {
 387                 tv->tv_sec--;
 388                 tv->tv_usec += USEC_PER_SEC;
 389         }
 390 }
 391
 392 EXPORT_SYMBOL_GPL(dccp_timestamp);
 393
 394 void dccp_insert_option_timestamp(struct sock *sk, struct sk_buff *skb)
 395 {
 396         struct timeval tv;
 397         __be32 now;
 398
 399         dccp_timestamp(sk, &tv);
 400         now = htonl(timeval_usecs(&tv) / 10);
 401         /* yes this will overflow but that is the point as we want a
 402          * 10 usec 32 bit timer which mean it wraps every 11.9 hours */
 403
 404         dccp_insert_option(sk, skb, DCCPO_TIMESTAMP, &now, sizeof(now));
 405 }
 406
 407 EXPORT_SYMBOL_GPL(dccp_insert_option_timestamp);
 408
 409 static void dccp_insert_option_timestamp_echo(struct sock *sk,
 410                                               struct sk_buff *skb)
 411 {
 412         struct dccp_sock *dp = dccp_sk(sk);
 413 #ifdef CONFIG_IP_DCCP_DEBUG
 414         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
 415                                         "CLIENT TX opt: " : "server TX opt: ";
 416 #endif
 417         struct timeval now;
 418         __be32 tstamp_echo;
 419         u32 elapsed_time;
 420         int len, elapsed_time_len;
 421         unsigned char *to;
 422
 423         dccp_timestamp(sk, &now);
 424         elapsed_time = timeval_delta(&now, &dp->dccps_timestamp_time) / 10;
 425         elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
 426         len = 6 + elapsed_time_len;
 427
 428         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
 429                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small to insert "
 430                                          "timestamp echo!\n");
 431                 return;
 432         }
 433
 434         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 435
 436         to    = skb_push(skb, len);
 437         *to++ = DCCPO_TIMESTAMP_ECHO;
 438         *to++ = len;
 439
 440         tstamp_echo = htonl(dp->dccps_timestamp_echo);
 441         memcpy(to, &tstamp_echo, 4);
 442         to += 4;
 443
 444         if (elapsed_time_len == 2) {
 445                 const __be16 var16 = htons((u16)elapsed_time);
 446                 memcpy(to, &var16, 2);
 447         } else if (elapsed_time_len == 4) {
 448                 const __be32 var32 = htonl(elapsed_time);
 449                 memcpy(to, &var32, 4);
 450         }
 451
 452         dccp_pr_debug("%sTIMESTAMP_ECHO=%u, len=%d, seqno=%llu\n",
 453                       debug_prefix, dp->dccps_timestamp_echo,
 454                       len,
 455                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 456
 457         dp->dccps_timestamp_echo = 0;
 458         dp->dccps_timestamp_time.tv_sec = 0;
 459         dp->dccps_timestamp_time.tv_usec = 0;
 460 }
 461
 462 static int dccp_insert_feat_opt(struct sk_buff *skb, u8 type, u8 feat,
 463                                 u8 *val, u8 len)
 464 {
 465         u8 *to;
 466
 467         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 3 > DCCP_MAX_OPT_LEN) {
 468                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small"
 469                                " to insert feature %d option!\n", feat);
 470                 return -1;
 471         }
 472
 473         DCCP_SKB_CB(skb)->dccpd_opt_len += len + 3;
 474
 475         to    = skb_push(skb, len + 3);
 476         *to++ = type;
 477         *to++ = len + 3;
 478         *to++ = feat;
 479
 480         if (len)
 481                 memcpy(to, val, len);
 482         dccp_pr_debug("option %d feat %d len %d\n", type, feat, len);
 483
 484         return 0;
 485 }
 486
 487 static void dccp_insert_feat(struct sock *sk, struct sk_buff *skb)
 488 {
 489         struct dccp_sock *dp = dccp_sk(sk);
 490         struct dccp_opt_pend *opt, *next;
 491         int change = 0;
 492
 493         /* confirm any options [NN opts] */
 494         list_for_each_entry_safe(opt, next, &dp->dccps_options.dccpo_conf,
 495                                  dccpop_node) {
 496                 dccp_insert_feat_opt(skb, opt->dccpop_type,
 497                                      opt->dccpop_feat, opt->dccpop_val,
 498                                      opt->dccpop_len);
 499                 /* fear empty confirms */
 500                 if (opt->dccpop_val)
 501                         kfree(opt->dccpop_val);
 502                 kfree(opt);
 503         }
 504         INIT_LIST_HEAD(&dp->dccps_options.dccpo_conf);
 505
 506         /* see which features we need to send */
 507         list_for_each_entry(opt, &dp->dccps_options.dccpo_pending,
 508                             dccpop_node) {
 509                 /* see if we need to send any confirm */
 510                 if (opt->dccpop_sc) {
 511                         dccp_insert_feat_opt(skb, opt->dccpop_type + 1,
 512                                              opt->dccpop_feat,
 513                                              opt->dccpop_sc->dccpoc_val,
 514                                              opt->dccpop_sc->dccpoc_len);
 515
 516                         BUG_ON(!opt->dccpop_sc->dccpoc_val);
 517                         kfree(opt->dccpop_sc->dccpoc_val);
 518                         kfree(opt->dccpop_sc);
 519                         opt->dccpop_sc = NULL;
 520                 }
 521
 522                 /* any option not confirmed, re-send it */
 523                 if (!opt->dccpop_conf) {
 524                         dccp_insert_feat_opt(skb, opt->dccpop_type,
 525                                              opt->dccpop_feat, opt->dccpop_val,
 526                                              opt->dccpop_len);
 527                         change++;
 528                 }
 529         }
 530
 531         /* Retransmit timer.
 532          * If this is the master listening sock, we don't set a timer on it.  It
 533          * should be fine because if the dude doesn't receive our RESPONSE
 534          * [which will contain the CHANGE] he will send another REQUEST which
 535          * will "retrnasmit" the change.
 536          */
 537         if (change && dp->dccps_role != DCCP_ROLE_LISTEN) {
 538                 dccp_pr_debug("reset feat negotiation timer %p\n", sk);
 539
 540                 /* XXX don't reset the timer on re-transmissions.  I.e. reset it
 541                  * only when sending new stuff i guess.  Currently the timer
 542                  * never backs off because on re-transmission it just resets it!
 543                  */
 544                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 545                                           inet_csk(sk)->icsk_rto, DCCP_RTO_MAX);
 546         }
 547 }
 548
 549 void 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_options.dccpo_send_ndp_count)
 556                 dccp_insert_option_ndp(sk, skb);
 557
 558         if (!dccp_packet_without_ack(skb)) {
 559                 if (dp->dccps_options.dccpo_send_ack_vector &&
 560                     dccp_ackvec_pending(dp->dccps_hc_rx_ackvec))
 561                         dccp_insert_option_ackvec(sk, skb);
 562                 if (dp->dccps_timestamp_echo != 0)
 563                         dccp_insert_option_timestamp_echo(sk, skb);
 564         }
 565
 566         if (dp->dccps_hc_rx_insert_options) {
 567                 ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb);
 568                 dp->dccps_hc_rx_insert_options = 0;
 569         }
 570         if (dp->dccps_hc_tx_insert_options) {
 571                 ccid_hc_tx_insert_options(dp->dccps_hc_tx_ccid, sk, skb);
 572                 dp->dccps_hc_tx_insert_options = 0;
 573         }
 574
 575         /* Feature negotiation */
 576         switch(DCCP_SKB_CB(skb)->dccpd_type) {
 577                 /* Data packets can't do feat negotiation */
 578         case DCCP_PKT_DATA:
 579         case DCCP_PKT_DATAACK:
 580                 break;
 581         default:
 582                 dccp_insert_feat(sk, skb);
 583                 break;
 584         }
 585
 586         /* XXX: insert other options when appropriate */
 587
 588         if (DCCP_SKB_CB(skb)->dccpd_opt_len != 0) {
 589                 /* The length of all options has to be a multiple of 4 */
 590                 int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
 591
 592                 if (padding != 0) {
 593                         padding = 4 - padding;
 594                         memset(skb_push(skb, padding), 0, padding);
 595                         DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
 596                 }
 597         }
 598 }