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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         u64 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
  58         unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
  59         unsigned char *opt_ptr = options;
  60         const unsigned char *opt_end = (unsigned char *)dh +
  61                                         (dh->dccph_doff * 4);
  62         struct dccp_options_received *opt_recv = &dp->dccps_options_received;
  63         unsigned char opt, len;
  64         unsigned char *uninitialized_var(value);
  65         u32 elapsed_time;
  66         __be32 opt_val;
  67         int rc;
  68         int mandatory = 0;
  69
  70         memset(opt_recv, 0, sizeof(*opt_recv));
  71
  72         opt = len = 0;
  73         while (opt_ptr != opt_end) {
  74                 opt   = *opt_ptr++;
  75                 len   = 0;
  76                 value = NULL;
  77
  78                 /* Check if this isn't a single byte option */
  79                 if (opt > DCCPO_MAX_RESERVED) {
  80                         if (opt_ptr == opt_end)
  81                                 goto out_nonsensical_length;
  82
  83                         len = *opt_ptr++;
  84                         if (len < 2)
  85                                 goto out_nonsensical_length;
  86                         /*
  87                          * Remove the type and len fields, leaving
  88                          * just the value size
  89                          */
  90                         len     -= 2;
  91                         value   = opt_ptr;
  92                         opt_ptr += len;
  93
  94                         if (opt_ptr > opt_end)
  95                                 goto out_nonsensical_length;
  96                 }
  97
  98                 /*
  99                  * CCID-Specific Options (from RFC 4340, sec. 10.3):
 100                  *
 101                  * Option numbers 128 through 191 are for options sent from the
 102                  * HC-Sender to the HC-Receiver; option numbers 192 through 255
 103                  * are for options sent from the HC-Receiver to the HC-Sender.
 104                  *
 105                  * CCID-specific options are ignored during connection setup, as
 106                  * negotiation may still be in progress (see RFC 4340, 10.3).
 107                  * The same applies to Ack Vectors, as these depend on the CCID.
 108                  *
 109                  */
 110                 if (dreq != NULL && (opt >= 128 ||
 111                     opt == DCCPO_ACK_VECTOR_0 || opt == DCCPO_ACK_VECTOR_1))
 112                         goto ignore_option;
 113
 114                 switch (opt) {
 115                 case DCCPO_PADDING:
 116                         break;
 117                 case DCCPO_MANDATORY:
 118                         if (mandatory)
 119                                 goto out_invalid_option;
 120                         if (pkt_type != DCCP_PKT_DATA)
 121                                 mandatory = 1;
 122                         break;
 123                 case DCCPO_NDP_COUNT:
 124                         if (len > 6)
 125                                 goto out_invalid_option;
 126
 127                         opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
 128                         dccp_pr_debug("%s opt: NDP count=%llu\n", dccp_role(sk),
 129                                       (unsigned long long)opt_recv->dccpor_ndp);
 130                         break;
 131                 case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R:
 132                         if (pkt_type == DCCP_PKT_DATA)      /* RFC 4340, 6 */
 133                                 break;
 134                         rc = dccp_feat_parse_options(sk, dreq, mandatory, opt,
 135                                                     *value, value + 1, len - 1);
 136                         if (rc)
 137                                 goto out_featneg_failed;
 138                         break;
 139                 case DCCPO_ACK_VECTOR_0:
 140                 case DCCPO_ACK_VECTOR_1:
 141                         if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
 142                                 break;
 143                         if (dp->dccps_hc_rx_ackvec != NULL &&
 144                             dccp_ackvec_parse(sk, skb, &ackno, opt, value, len))
 145                                 goto out_invalid_option;
 146                         break;
 147                 case DCCPO_TIMESTAMP:
 148                         if (len != 4)
 149                                 goto out_invalid_option;
 150                         /*
 151                          * RFC 4340 13.1: "The precise time corresponding to
 152                          * Timestamp Value zero is not specified". We use
 153                          * zero to indicate absence of a meaningful timestamp.
 154                          */
 155                         opt_val = get_unaligned((__be32 *)value);
 156                         if (unlikely(opt_val == 0)) {
 157                                 DCCP_WARN("Timestamp with zero value\n");
 158                                 break;
 159                         }
 160
 161                         if (dreq != NULL) {
 162                                 dreq->dreq_timestamp_echo = ntohl(opt_val);
 163                                 dreq->dreq_timestamp_time = dccp_timestamp();
 164                         } else {
 165                                 opt_recv->dccpor_timestamp =
 166                                         dp->dccps_timestamp_echo = ntohl(opt_val);
 167                                 dp->dccps_timestamp_time = dccp_timestamp();
 168                         }
 169                         dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n",
 170                                       dccp_role(sk), ntohl(opt_val),
 171                                       (unsigned long long)
 172                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
 173                         break;
 174                 case DCCPO_TIMESTAMP_ECHO:
 175                         if (len != 4 && len != 6 && len != 8)
 176                                 goto out_invalid_option;
 177
 178                         opt_val = get_unaligned((__be32 *)value);
 179                         opt_recv->dccpor_timestamp_echo = ntohl(opt_val);
 180
 181                         dccp_pr_debug("%s rx opt: TIMESTAMP_ECHO=%u, len=%d, "
 182                                       "ackno=%llu", dccp_role(sk),
 183                                       opt_recv->dccpor_timestamp_echo,
 184                                       len + 2,
 185                                       (unsigned long long)
 186                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
 187
 188                         value += 4;
 189
 190                         if (len == 4) {         /* no elapsed time included */
 191                                 dccp_pr_debug_cat("\n");
 192                                 break;
 193                         }
 194
 195                         if (len == 6) {         /* 2-byte elapsed time */
 196                                 __be16 opt_val2 = get_unaligned((__be16 *)value);
 197                                 elapsed_time = ntohs(opt_val2);
 198                         } else {                /* 4-byte elapsed time */
 199                                 opt_val = get_unaligned((__be32 *)value);
 200                                 elapsed_time = ntohl(opt_val);
 201                         }
 202
 203                         dccp_pr_debug_cat(", ELAPSED_TIME=%u\n", elapsed_time);
 204
 205                         /* Give precedence to the biggest ELAPSED_TIME */
 206                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
 207                                 opt_recv->dccpor_elapsed_time = elapsed_time;
 208                         break;
 209                 case DCCPO_ELAPSED_TIME:
 210                         if (dccp_packet_without_ack(skb))   /* RFC 4340, 13.2 */
 211                                 break;
 212
 213                         if (len == 2) {
 214                                 __be16 opt_val2 = get_unaligned((__be16 *)value);
 215                                 elapsed_time = ntohs(opt_val2);
 216                         } else if (len == 4) {
 217                                 opt_val = get_unaligned((__be32 *)value);
 218                                 elapsed_time = ntohl(opt_val);
 219                         } else {
 220                                 goto out_invalid_option;
 221                         }
 222
 223                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
 224                                 opt_recv->dccpor_elapsed_time = elapsed_time;
 225
 226                         dccp_pr_debug("%s rx opt: ELAPSED_TIME=%d\n",
 227                                       dccp_role(sk), elapsed_time);
 228                         break;
 229                 case 128 ... 191: {
 230                         const u16 idx = value - options;
 231
 232                         if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
 233                                                      opt, len, idx,
 234                                                      value) != 0)
 235                                 goto out_invalid_option;
 236                 }
 237                         break;
 238                 case 192 ... 255: {
 239                         const u16 idx = value - options;
 240
 241                         if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
 242                                                      opt, len, idx,
 243                                                      value) != 0)
 244                                 goto out_invalid_option;
 245                 }
 246                         break;
 247                 default:
 248                         DCCP_CRIT("DCCP(%p): option %d(len=%d) not "
 249                                   "implemented, ignoring", sk, opt, len);
 250                         break;
 251                 }
 252 ignore_option:
 253                 if (opt != DCCPO_MANDATORY)
 254                         mandatory = 0;
 255         }
 256
 257         /* mandatory was the last byte in option list -> reset connection */
 258         if (mandatory)
 259                 goto out_invalid_option;
 260
 261 out_nonsensical_length:
 262         /* RFC 4340, 5.8: ignore option and all remaining option space */
 263         return 0;
 264
 265 out_invalid_option:
 266         DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
 267         rc = DCCP_RESET_CODE_OPTION_ERROR;
 268 out_featneg_failed:
 269         DCCP_WARN("DCCP(%p): Option %d (len=%d) error=%u\n", sk, opt, len, rc);
 270         DCCP_SKB_CB(skb)->dccpd_reset_code = rc;
 271         DCCP_SKB_CB(skb)->dccpd_reset_data[0] = opt;
 272         DCCP_SKB_CB(skb)->dccpd_reset_data[1] = len > 0 ? value[0] : 0;
 273         DCCP_SKB_CB(skb)->dccpd_reset_data[2] = len > 1 ? value[1] : 0;
 274         return -1;
 275 }
 276
 277 EXPORT_SYMBOL_GPL(dccp_parse_options);
 278
 279 void dccp_encode_value_var(const u64 value, u8 *to, const u8 len)
 280 {
 281         if (len >= DCCP_OPTVAL_MAXLEN)
 282                 *to++ = (value & 0xFF0000000000ull) >> 40;
 283         if (len > 4)
 284                 *to++ = (value & 0xFF00000000ull) >> 32;
 285         if (len > 3)
 286                 *to++ = (value & 0xFF000000) >> 24;
 287         if (len > 2)
 288                 *to++ = (value & 0xFF0000) >> 16;
 289         if (len > 1)
 290                 *to++ = (value & 0xFF00) >> 8;
 291         if (len > 0)
 292                 *to++ = (value & 0xFF);
 293 }
 294
 295 static inline u8 dccp_ndp_len(const u64 ndp)
 296 {
 297         if (likely(ndp <= 0xFF))
 298                 return 1;
 299         return likely(ndp <= USHORT_MAX) ? 2 : (ndp <= UINT_MAX ? 4 : 6);
 300 }
 301
 302 int dccp_insert_option(struct sock *sk, struct sk_buff *skb,
 303                         const unsigned char option,
 304                         const void *value, const unsigned char len)
 305 {
 306         unsigned char *to;
 307
 308         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 2 > DCCP_MAX_OPT_LEN)
 309                 return -1;
 310
 311         DCCP_SKB_CB(skb)->dccpd_opt_len += len + 2;
 312
 313         to    = skb_push(skb, len + 2);
 314         *to++ = option;
 315         *to++ = len + 2;
 316
 317         memcpy(to, value, len);
 318         return 0;
 319 }
 320
 321 EXPORT_SYMBOL_GPL(dccp_insert_option);
 322
 323 static int dccp_insert_option_ndp(struct sock *sk, struct sk_buff *skb)
 324 {
 325         struct dccp_sock *dp = dccp_sk(sk);
 326         u64 ndp = dp->dccps_ndp_count;
 327
 328         if (dccp_non_data_packet(skb))
 329                 ++dp->dccps_ndp_count;
 330         else
 331                 dp->dccps_ndp_count = 0;
 332
 333         if (ndp > 0) {
 334                 unsigned char *ptr;
 335                 const int ndp_len = dccp_ndp_len(ndp);
 336                 const int len = ndp_len + 2;
 337
 338                 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
 339                         return -1;
 340
 341                 DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 342
 343                 ptr = skb_push(skb, len);
 344                 *ptr++ = DCCPO_NDP_COUNT;
 345                 *ptr++ = len;
 346                 dccp_encode_value_var(ndp, ptr, ndp_len);
 347         }
 348
 349         return 0;
 350 }
 351
 352 static inline int dccp_elapsed_time_len(const u32 elapsed_time)
 353 {
 354         return elapsed_time == 0 ? 0 : elapsed_time <= 0xFFFF ? 2 : 4;
 355 }
 356
 357 int dccp_insert_option_elapsed_time(struct sock *sk, struct sk_buff *skb,
 358                                     u32 elapsed_time)
 359 {
 360         const int elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
 361         const int len = 2 + elapsed_time_len;
 362         unsigned char *to;
 363
 364         if (elapsed_time_len == 0)
 365                 return 0;
 366
 367         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
 368                 return -1;
 369
 370         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 371
 372         to    = skb_push(skb, len);
 373         *to++ = DCCPO_ELAPSED_TIME;
 374         *to++ = len;
 375
 376         if (elapsed_time_len == 2) {
 377                 const __be16 var16 = htons((u16)elapsed_time);
 378                 memcpy(to, &var16, 2);
 379         } else {
 380                 const __be32 var32 = htonl(elapsed_time);
 381                 memcpy(to, &var32, 4);
 382         }
 383
 384         return 0;
 385 }
 386
 387 EXPORT_SYMBOL_GPL(dccp_insert_option_elapsed_time);
 388
 389 int dccp_insert_option_timestamp(struct sock *sk, struct sk_buff *skb)
 390 {
 391         __be32 now = htonl(dccp_timestamp());
 392         /* yes this will overflow but that is the point as we want a
 393          * 10 usec 32 bit timer which mean it wraps every 11.9 hours */
 394
 395         return dccp_insert_option(sk, skb, DCCPO_TIMESTAMP, &now, sizeof(now));
 396 }
 397
 398 EXPORT_SYMBOL_GPL(dccp_insert_option_timestamp);
 399
 400 static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
 401                                              struct dccp_request_sock *dreq,
 402                                              struct sk_buff *skb)
 403 {
 404         __be32 tstamp_echo;
 405         unsigned char *to;
 406         u32 elapsed_time, elapsed_time_len, len;
 407
 408         if (dreq != NULL) {
 409                 elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time;
 410                 tstamp_echo  = htonl(dreq->dreq_timestamp_echo);
 411                 dreq->dreq_timestamp_echo = 0;
 412         } else {
 413                 elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time;
 414                 tstamp_echo  = htonl(dp->dccps_timestamp_echo);
 415                 dp->dccps_timestamp_echo = 0;
 416         }
 417
 418         elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
 419         len = 6 + elapsed_time_len;
 420
 421         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
 422                 return -1;
 423
 424         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 425
 426         to    = skb_push(skb, len);
 427         *to++ = DCCPO_TIMESTAMP_ECHO;
 428         *to++ = len;
 429
 430         memcpy(to, &tstamp_echo, 4);
 431         to += 4;
 432
 433         if (elapsed_time_len == 2) {
 434                 const __be16 var16 = htons((u16)elapsed_time);
 435                 memcpy(to, &var16, 2);
 436         } else if (elapsed_time_len == 4) {
 437                 const __be32 var32 = htonl(elapsed_time);
 438                 memcpy(to, &var32, 4);
 439         }
 440
 441         return 0;
 442 }
 443
 444 /**
 445  * dccp_insert_option_mandatory  -  Mandatory option (5.8.2)
 446  * Note that since we are using skb_push, this function needs to be called
 447  * _after_ inserting the option it is supposed to influence (stack order).
 448  */
 449 int dccp_insert_option_mandatory(struct sk_buff *skb)
 450 {
 451         if (DCCP_SKB_CB(skb)->dccpd_opt_len >= DCCP_MAX_OPT_LEN)
 452                 return -1;
 453
 454         DCCP_SKB_CB(skb)->dccpd_opt_len++;
 455         *skb_push(skb, 1) = DCCPO_MANDATORY;
 456         return 0;
 457 }
 458
 459 /**
 460  * dccp_insert_fn_opt  -  Insert single Feature-Negotiation option into @skb
 461  * @type: %DCCPO_CHANGE_L, %DCCPO_CHANGE_R, %DCCPO_CONFIRM_L, %DCCPO_CONFIRM_R
 462  * @feat: one out of %dccp_feature_numbers
 463  * @val: NN value or SP array (preferred element first) to copy
 464  * @len: true length of @val in bytes (excluding first element repetition)
 465  * @repeat_first: whether to copy the first element of @val twice
 466  * The last argument is used to construct Confirm options, where the preferred
 467  * value and the preference list appear separately (RFC 4340, 6.3.1). Preference
 468  * lists are kept such that the preferred entry is always first, so we only need
 469  * to copy twice, and avoid the overhead of cloning into a bigger array.
 470  */
 471 int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
 472                        u8 *val, u8 len, bool repeat_first)
 473 {
 474         u8 tot_len, *to;
 475
 476         /* take the `Feature' field and possible repetition into account */
 477         if (len > (DCCP_SINGLE_OPT_MAXLEN - 2)) {
 478                 DCCP_WARN("length %u for feature %u too large\n", len, feat);
 479                 return -1;
 480         }
 481
 482         if (unlikely(val == NULL || len == 0))
 483                 len = repeat_first = 0;
 484         tot_len = 3 + repeat_first + len;
 485
 486         if (DCCP_SKB_CB(skb)->dccpd_opt_len + tot_len > DCCP_MAX_OPT_LEN) {
 487                 DCCP_WARN("packet too small for feature %d option!\n", feat);
 488                 return -1;
 489         }
 490         DCCP_SKB_CB(skb)->dccpd_opt_len += tot_len;
 491
 492         to    = skb_push(skb, tot_len);
 493         *to++ = type;
 494         *to++ = tot_len;
 495         *to++ = feat;
 496
 497         if (repeat_first)
 498                 *to++ = *val;
 499         if (len)
 500                 memcpy(to, val, len);
 501         return 0;
 502 }
 503
 504 /* The length of all options needs to be a multiple of 4 (5.8) */
 505 static void dccp_insert_option_padding(struct sk_buff *skb)
 506 {
 507         int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
 508
 509         if (padding != 0) {
 510                 padding = 4 - padding;
 511                 memset(skb_push(skb, padding), 0, padding);
 512                 DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
 513         }
 514 }
 515
 516 int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
 517 {
 518         struct dccp_sock *dp = dccp_sk(sk);
 519
 520         DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
 521
 522         if (dp->dccps_send_ndp_count && dccp_insert_option_ndp(sk, skb))
 523                 return -1;
 524
 525         if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA) {
 526
 527                 /* Feature Negotiation */
 528                 if (dccp_feat_insert_opts(dp, NULL, skb))
 529                         return -1;
 530
 531                 if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST) {
 532                         /*
 533                          * Obtain RTT sample from Request/Response exchange.
 534                          * This is currently used in CCID 3 initialisation.
 535                          */
 536                         if (dccp_insert_option_timestamp(sk, skb))
 537                                 return -1;
 538
 539                 } else if (dp->dccps_hc_rx_ackvec != NULL &&
 540                            dccp_ackvec_pending(dp->dccps_hc_rx_ackvec) &&
 541                            dccp_insert_option_ackvec(sk, skb)) {
 542                                 return -1;
 543                 }
 544         }
 545
 546         if (dp->dccps_hc_rx_insert_options) {
 547                 if (ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb))
 548                         return -1;
 549                 dp->dccps_hc_rx_insert_options = 0;
 550         }
 551
 552         if (dp->dccps_timestamp_echo != 0 &&
 553             dccp_insert_option_timestamp_echo(dp, NULL, skb))
 554                 return -1;
 555
 556         dccp_insert_option_padding(skb);
 557         return 0;
 558 }
 559
 560 int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb)
 561 {
 562         DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
 563
 564         if (dccp_feat_insert_opts(NULL, dreq, skb))
 565                 return -1;
 566
 567         if (dreq->dreq_timestamp_echo != 0 &&
 568             dccp_insert_option_timestamp_echo(NULL, dreq, skb))
 569                 return -1;
 570
 571         dccp_insert_option_padding(skb);
 572         return 0;
 573 }