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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 <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                         if (pkt_type != DCCP_PKT_DATA)
 113                                 mandatory = 1;
 114                         break;
 115                 case DCCPO_NDP_COUNT:
 116                         if (len > 3)
 117                                 goto out_invalid_option;
 118
 119                         opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
 120                         dccp_pr_debug("%sNDP count=%d\n", debug_prefix,
 121                                       opt_recv->dccpor_ndp);
 122                         break;
 123                 case DCCPO_CHANGE_L:
 124                         /* fall through */
 125                 case DCCPO_CHANGE_R:
 126                         if (len < 2)
 127                                 goto out_invalid_option;
 128                         rc = dccp_feat_change_recv(sk, opt, *value, value + 1,
 129                                                    len - 1);
 130                         /*
 131                          * When there is a change error, change_recv is
 132                          * responsible for dealing with it.  i.e. reply with an
 133                          * empty confirm.
 134                          * If the change was mandatory, then we need to die.
 135                          */
 136                         if (rc && mandatory)
 137                                 goto out_invalid_option;
 138                         break;
 139                 case DCCPO_CONFIRM_L:
 140                         /* fall through */
 141                 case DCCPO_CONFIRM_R:
 142                         if (len < 2)
 143                                 goto out_invalid_option;
 144                         if (dccp_feat_confirm_recv(sk, opt, *value,
 145                                                    value + 1, len - 1))
 146                                 goto out_invalid_option;
 147                         break;
 148                 case DCCPO_ACK_VECTOR_0:
 149                 case DCCPO_ACK_VECTOR_1:
 150                         if (pkt_type == DCCP_PKT_DATA)
 151                                 continue;
 152
 153                         if (dp->dccps_options.dccpo_send_ack_vector &&
 154                             dccp_ackvec_parse(sk, skb, opt, value, len))
 155                                 goto out_invalid_option;
 156                         break;
 157                 case DCCPO_TIMESTAMP:
 158                         if (len != 4)
 159                                 goto out_invalid_option;
 160
 161                         opt_recv->dccpor_timestamp = ntohl(*(__be32 *)value);
 162
 163                         dp->dccps_timestamp_echo = opt_recv->dccpor_timestamp;
 164                         dccp_timestamp(sk, &dp->dccps_timestamp_time);
 165
 166                         dccp_pr_debug("%sTIMESTAMP=%u, ackno=%llu\n",
 167                                       debug_prefix, opt_recv->dccpor_timestamp,
 168                                       (unsigned long long)
 169                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
 170                         break;
 171                 case DCCPO_TIMESTAMP_ECHO:
 172                         if (len != 4 && len != 6 && len != 8)
 173                                 goto out_invalid_option;
 174
 175                         opt_recv->dccpor_timestamp_echo = ntohl(*(__be32 *)value);
 176
 177                         dccp_pr_debug("%sTIMESTAMP_ECHO=%u, len=%d, ackno=%llu, ",
 178                                       debug_prefix,
 179                                       opt_recv->dccpor_timestamp_echo,
 180                                       len + 2,
 181                                       (unsigned long long)
 182                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
 183
 184
 185                         if (len == 4)
 186                                 break;
 187
 188                         if (len == 6)
 189                                 elapsed_time = ntohs(*(__be16 *)(value + 4));
 190                         else
 191                                 elapsed_time = ntohl(*(__be32 *)(value + 4));
 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 (len != 2 && len != 4)
 199                                 goto out_invalid_option;
 200
 201                         if (pkt_type == DCCP_PKT_DATA)
 202                                 continue;
 203
 204                         if (len == 2)
 205                                 elapsed_time = ntohs(*(__be16 *)value);
 206                         else
 207                                 elapsed_time = ntohl(*(__be32 *)value);
 208
 209                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
 210                                 opt_recv->dccpor_elapsed_time = elapsed_time;
 211
 212                         dccp_pr_debug("%sELAPSED_TIME=%d\n", debug_prefix,
 213                                       elapsed_time);
 214                         break;
 215                         /*
 216                          * From draft-ietf-dccp-spec-11.txt:
 217                          *
 218                          *      Option numbers 128 through 191 are for
 219                          *      options sent from the HC-Sender to the
 220                          *      HC-Receiver; option numbers 192 through 255
 221                          *      are for options sent from the HC-Receiver to
 222                          *      the HC-Sender.
 223                          */
 224                 case 128 ... 191: {
 225                         const u16 idx = value - options;
 226
 227                         if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
 228                                                      opt, len, idx,
 229                                                      value) != 0)
 230                                 goto out_invalid_option;
 231                 }
 232                         break;
 233                 case 192 ... 255: {
 234                         const u16 idx = value - options;
 235
 236                         if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
 237                                                      opt, len, idx,
 238                                                      value) != 0)
 239                                 goto out_invalid_option;
 240                 }
 241                         break;
 242                 default:
 243                         pr_info("DCCP(%p): option %d(len=%d) not "
 244                                 "implemented, ignoring\n",
 245                                 sk, opt, len);
 246                         break;
 247                 }
 248
 249                 if (opt != DCCPO_MANDATORY)
 250                         mandatory = 0;
 251         }
 252
 253         /* mandatory was the last byte in option list -> reset connection */
 254         if (mandatory)
 255                 goto out_invalid_option;
 256
 257         return 0;
 258
 259 out_invalid_option:
 260         DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
 261         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_OPTION_ERROR;
 262         pr_info("DCCP(%p): invalid option %d, len=%d\n", sk, opt, len);
 263         return -1;
 264 }
 265
 266 EXPORT_SYMBOL_GPL(dccp_parse_options);
 267
 268 static void dccp_encode_value_var(const u32 value, unsigned char *to,
 269                                   const unsigned int len)
 270 {
 271         if (len > 3)
 272                 *to++ = (value & 0xFF000000) >> 24;
 273         if (len > 2)
 274                 *to++ = (value & 0xFF0000) >> 16;
 275         if (len > 1)
 276                 *to++ = (value & 0xFF00) >> 8;
 277         if (len > 0)
 278                 *to++ = (value & 0xFF);
 279 }
 280
 281 static inline int dccp_ndp_len(const int ndp)
 282 {
 283         return likely(ndp <= 0xFF) ? 1 : ndp <= 0xFFFF ? 2 : 3;
 284 }
 285
 286 void dccp_insert_option(struct sock *sk, struct sk_buff *skb,
 287                         const unsigned char option,
 288                         const void *value, const unsigned char len)
 289 {
 290         unsigned char *to;
 291
 292         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 2 > DCCP_MAX_OPT_LEN) {
 293                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small to insert "
 294                                "%d option!\n", option);
 295                 return;
 296         }
 297
 298         DCCP_SKB_CB(skb)->dccpd_opt_len += len + 2;
 299
 300         to    = skb_push(skb, len + 2);
 301         *to++ = option;
 302         *to++ = len + 2;
 303
 304         memcpy(to, value, len);
 305 }
 306
 307 EXPORT_SYMBOL_GPL(dccp_insert_option);
 308
 309 static void dccp_insert_option_ndp(struct sock *sk, struct sk_buff *skb)
 310 {
 311         struct dccp_sock *dp = dccp_sk(sk);
 312         int ndp = dp->dccps_ndp_count;
 313
 314         if (dccp_non_data_packet(skb))
 315                 ++dp->dccps_ndp_count;
 316         else
 317                 dp->dccps_ndp_count = 0;
 318
 319         if (ndp > 0) {
 320                 unsigned char *ptr;
 321                 const int ndp_len = dccp_ndp_len(ndp);
 322                 const int len = ndp_len + 2;
 323
 324                 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
 325                         return;
 326
 327                 DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 328
 329                 ptr = skb_push(skb, len);
 330                 *ptr++ = DCCPO_NDP_COUNT;
 331                 *ptr++ = len;
 332                 dccp_encode_value_var(ndp, ptr, ndp_len);
 333         }
 334 }
 335
 336 static inline int dccp_elapsed_time_len(const u32 elapsed_time)
 337 {
 338         return elapsed_time == 0 ? 0 : elapsed_time <= 0xFFFF ? 2 : 4;
 339 }
 340
 341 void dccp_insert_option_elapsed_time(struct sock *sk,
 342                                      struct sk_buff *skb,
 343                                      u32 elapsed_time)
 344 {
 345 #ifdef CONFIG_IP_DCCP_DEBUG
 346         struct dccp_sock *dp = dccp_sk(sk);
 347         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
 348                                         "CLIENT TX opt: " : "server TX opt: ";
 349 #endif
 350         const int elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
 351         const int len = 2 + elapsed_time_len;
 352         unsigned char *to;
 353
 354         if (elapsed_time_len == 0)
 355                 return;
 356
 357         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
 358                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small to "
 359                                          "insert elapsed time!\n");
 360                 return;
 361         }
 362
 363         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 364
 365         to    = skb_push(skb, len);
 366         *to++ = DCCPO_ELAPSED_TIME;
 367         *to++ = len;
 368
 369         if (elapsed_time_len == 2) {
 370                 const __be16 var16 = htons((u16)elapsed_time);
 371                 memcpy(to, &var16, 2);
 372         } else {
 373                 const __be32 var32 = htonl(elapsed_time);
 374                 memcpy(to, &var32, 4);
 375         }
 376
 377         dccp_pr_debug("%sELAPSED_TIME=%u, len=%d, seqno=%llu\n",
 378                       debug_prefix, elapsed_time,
 379                       len,
 380                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 381 }
 382
 383 EXPORT_SYMBOL_GPL(dccp_insert_option_elapsed_time);
 384
 385 void dccp_timestamp(const struct sock *sk, struct timeval *tv)
 386 {
 387         const struct dccp_sock *dp = dccp_sk(sk);
 388
 389         do_gettimeofday(tv);
 390         tv->tv_sec  -= dp->dccps_epoch.tv_sec;
 391         tv->tv_usec -= dp->dccps_epoch.tv_usec;
 392
 393         while (tv->tv_usec < 0) {
 394                 tv->tv_sec--;
 395                 tv->tv_usec += USEC_PER_SEC;
 396         }
 397 }
 398
 399 EXPORT_SYMBOL_GPL(dccp_timestamp);
 400
 401 void dccp_insert_option_timestamp(struct sock *sk, struct sk_buff *skb)
 402 {
 403         struct timeval tv;
 404         __be32 now;
 405
 406         dccp_timestamp(sk, &tv);
 407         now = htonl(timeval_usecs(&tv) / 10);
 408         /* yes this will overflow but that is the point as we want a
 409          * 10 usec 32 bit timer which mean it wraps every 11.9 hours */
 410
 411         dccp_insert_option(sk, skb, DCCPO_TIMESTAMP, &now, sizeof(now));
 412 }
 413
 414 EXPORT_SYMBOL_GPL(dccp_insert_option_timestamp);
 415
 416 static void dccp_insert_option_timestamp_echo(struct sock *sk,
 417                                               struct sk_buff *skb)
 418 {
 419         struct dccp_sock *dp = dccp_sk(sk);
 420 #ifdef CONFIG_IP_DCCP_DEBUG
 421         const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
 422                                         "CLIENT TX opt: " : "server TX opt: ";
 423 #endif
 424         struct timeval now;
 425         __be32 tstamp_echo;
 426         u32 elapsed_time;
 427         int len, elapsed_time_len;
 428         unsigned char *to;
 429
 430         dccp_timestamp(sk, &now);
 431         elapsed_time = timeval_delta(&now, &dp->dccps_timestamp_time) / 10;
 432         elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
 433         len = 6 + elapsed_time_len;
 434
 435         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
 436                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small to insert "
 437                                          "timestamp echo!\n");
 438                 return;
 439         }
 440
 441         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 442
 443         to    = skb_push(skb, len);
 444         *to++ = DCCPO_TIMESTAMP_ECHO;
 445         *to++ = len;
 446
 447         tstamp_echo = htonl(dp->dccps_timestamp_echo);
 448         memcpy(to, &tstamp_echo, 4);
 449         to += 4;
 450
 451         if (elapsed_time_len == 2) {
 452                 const __be16 var16 = htons((u16)elapsed_time);
 453                 memcpy(to, &var16, 2);
 454         } else if (elapsed_time_len == 4) {
 455                 const __be32 var32 = htonl(elapsed_time);
 456                 memcpy(to, &var32, 4);
 457         }
 458
 459         dccp_pr_debug("%sTIMESTAMP_ECHO=%u, len=%d, seqno=%llu\n",
 460                       debug_prefix, dp->dccps_timestamp_echo,
 461                       len,
 462                       (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 463
 464         dp->dccps_timestamp_echo = 0;
 465         dp->dccps_timestamp_time.tv_sec = 0;
 466         dp->dccps_timestamp_time.tv_usec = 0;
 467 }
 468
 469 static int dccp_insert_feat_opt(struct sk_buff *skb, u8 type, u8 feat,
 470                                 u8 *val, u8 len)
 471 {
 472         u8 *to;
 473
 474         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 3 > DCCP_MAX_OPT_LEN) {
 475                 LIMIT_NETDEBUG(KERN_INFO "DCCP: packet too small"
 476                                " to insert feature %d option!\n", feat);
 477                 return -1;
 478         }
 479
 480         DCCP_SKB_CB(skb)->dccpd_opt_len += len + 3;
 481
 482         to    = skb_push(skb, len + 3);
 483         *to++ = type;
 484         *to++ = len + 3;
 485         *to++ = feat;
 486
 487         if (len)
 488                 memcpy(to, val, len);
 489         dccp_pr_debug("option %d feat %d len %d\n", type, feat, len);
 490
 491         return 0;
 492 }
 493
 494 static void dccp_insert_feat(struct sock *sk, struct sk_buff *skb)
 495 {
 496         struct dccp_sock *dp = dccp_sk(sk);
 497         struct dccp_opt_pend *opt, *next;
 498         int change = 0;
 499
 500         /* confirm any options [NN opts] */
 501         list_for_each_entry_safe(opt, next, &dp->dccps_options.dccpo_conf,
 502                                  dccpop_node) {
 503                 dccp_insert_feat_opt(skb, opt->dccpop_type,
 504                                      opt->dccpop_feat, opt->dccpop_val,
 505                                      opt->dccpop_len);
 506                 /* fear empty confirms */
 507                 if (opt->dccpop_val)
 508                         kfree(opt->dccpop_val);
 509                 kfree(opt);
 510         }
 511         INIT_LIST_HEAD(&dp->dccps_options.dccpo_conf);
 512
 513         /* see which features we need to send */
 514         list_for_each_entry(opt, &dp->dccps_options.dccpo_pending,
 515                             dccpop_node) {
 516                 /* see if we need to send any confirm */
 517                 if (opt->dccpop_sc) {
 518                         dccp_insert_feat_opt(skb, opt->dccpop_type + 1,
 519                                              opt->dccpop_feat,
 520                                              opt->dccpop_sc->dccpoc_val,
 521                                              opt->dccpop_sc->dccpoc_len);
 522
 523                         BUG_ON(!opt->dccpop_sc->dccpoc_val);
 524                         kfree(opt->dccpop_sc->dccpoc_val);
 525                         kfree(opt->dccpop_sc);
 526                         opt->dccpop_sc = NULL;
 527                 }
 528
 529                 /* any option not confirmed, re-send it */
 530                 if (!opt->dccpop_conf) {
 531                         dccp_insert_feat_opt(skb, opt->dccpop_type,
 532                                              opt->dccpop_feat, opt->dccpop_val,
 533                                              opt->dccpop_len);
 534                         change++;
 535                 }
 536         }
 537
 538         /* Retransmit timer.
 539          * If this is the master listening sock, we don't set a timer on it.  It
 540          * should be fine because if the dude doesn't receive our RESPONSE
 541          * [which will contain the CHANGE] he will send another REQUEST which
 542          * will "retrnasmit" the change.
 543          */
 544         if (change && dp->dccps_role != DCCP_ROLE_LISTEN) {
 545                 dccp_pr_debug("reset feat negotiation timer %p\n", sk);
 546
 547                 /* XXX don't reset the timer on re-transmissions.  I.e. reset it
 548                  * only when sending new stuff i guess.  Currently the timer
 549                  * never backs off because on re-transmission it just resets it!
 550                  */
 551                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 552                                           inet_csk(sk)->icsk_rto, DCCP_RTO_MAX);
 553         }
 554 }
 555
 556 void dccp_insert_options(struct sock *sk, struct sk_buff *skb)
 557 {
 558         struct dccp_sock *dp = dccp_sk(sk);
 559
 560         DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
 561
 562         if (dp->dccps_options.dccpo_send_ndp_count)
 563                 dccp_insert_option_ndp(sk, skb);
 564
 565         if (!dccp_packet_without_ack(skb)) {
 566                 if (dp->dccps_options.dccpo_send_ack_vector &&
 567                     dccp_ackvec_pending(dp->dccps_hc_rx_ackvec))
 568                         dccp_insert_option_ackvec(sk, skb);
 569                 if (dp->dccps_timestamp_echo != 0)
 570                         dccp_insert_option_timestamp_echo(sk, skb);
 571         }
 572
 573         if (dp->dccps_hc_rx_insert_options) {
 574                 ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb);
 575                 dp->dccps_hc_rx_insert_options = 0;
 576         }
 577         if (dp->dccps_hc_tx_insert_options) {
 578                 ccid_hc_tx_insert_options(dp->dccps_hc_tx_ccid, sk, skb);
 579                 dp->dccps_hc_tx_insert_options = 0;
 580         }
 581
 582         /* Feature negotiation */
 583         switch(DCCP_SKB_CB(skb)->dccpd_type) {
 584                 /* Data packets can't do feat negotiation */
 585         case DCCP_PKT_DATA:
 586         case DCCP_PKT_DATAACK:
 587                 break;
 588         default:
 589                 dccp_insert_feat(sk, skb);
 590                 break;
 591         }
 592
 593         /* XXX: insert other options when appropriate */
 594
 595         if (DCCP_SKB_CB(skb)->dccpd_opt_len != 0) {
 596                 /* The length of all options has to be a multiple of 4 */
 597                 int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
 598
 599                 if (padding != 0) {
 600                         padding = 4 - padding;
 601                         memset(skb_push(skb, padding), 0, padding);
 602                         DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
 603                 }
 604         }
 605 }