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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
  30 u64 dccp_decode_value_var(const u8 *bf, const u8 len)
  31 {
  32         u64 value = 0;
  33
  34         if (len >= DCCP_OPTVAL_MAXLEN)
  35                 value += ((u64)*bf++) << 40;
  36         if (len > 4)
  37                 value += ((u64)*bf++) << 32;
  38         if (len > 3)
  39                 value += ((u64)*bf++) << 24;
  40         if (len > 2)
  41                 value += ((u64)*bf++) << 16;
  42         if (len > 1)
  43                 value += ((u64)*bf++) << 8;
  44         if (len > 0)
  45                 value += *bf;
  46
  47         return value;
  48 }
  49
  50 /**
  51  * dccp_parse_options  -  Parse DCCP options present in @skb
  52  * @sk: client|server|listening dccp socket (when @dreq != NULL)
  53  * @dreq: request socket to use during connection setup, or NULL
  54  */
  55 int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
  56                        struct sk_buff *skb)
  57 {
  58         struct dccp_sock *dp = dccp_sk(sk);
  59         const struct dccp_hdr *dh = dccp_hdr(skb);
  60         const u8 pkt_type = DCCP_SKB_CB(skb)->dccpd_type;
  61         u64 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
  62         unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
  63         unsigned char *opt_ptr = options;
  64         const unsigned char *opt_end = (unsigned char *)dh +
  65                                         (dh->dccph_doff * 4);
  66         struct dccp_options_received *opt_recv = &dp->dccps_options_received;
  67         unsigned char opt, len;
  68         unsigned char *uninitialized_var(value);
  69         u32 elapsed_time;
  70         __be32 opt_val;
  71         int rc;
  72         int mandatory = 0;
  73
  74         memset(opt_recv, 0, sizeof(*opt_recv));
  75
  76         opt = len = 0;
  77         while (opt_ptr != opt_end) {
  78                 opt   = *opt_ptr++;
  79                 len   = 0;
  80                 value = NULL;
  81
  82                 /* Check if this isn't a single byte option */
  83                 if (opt > DCCPO_MAX_RESERVED) {
  84                         if (opt_ptr == opt_end)
  85                                 goto out_nonsensical_length;
  86
  87                         len = *opt_ptr++;
  88                         if (len < 2)
  89                                 goto out_nonsensical_length;
  90                         /*
  91                          * Remove the type and len fields, leaving
  92                          * just the value size
  93                          */
  94                         len     -= 2;
  95                         value   = opt_ptr;
  96                         opt_ptr += len;
  97
  98                         if (opt_ptr > opt_end)
  99                                 goto out_nonsensical_length;
 100                 }
 101
 102                 /*
 103                  * CCID-Specific Options (from RFC 4340, sec. 10.3):
 104                  *
 105                  * Option numbers 128 through 191 are for options sent from the
 106                  * HC-Sender to the HC-Receiver; option numbers 192 through 255
 107                  * are for options sent from the HC-Receiver to the HC-Sender.
 108                  *
 109                  * CCID-specific options are ignored during connection setup, as
 110                  * negotiation may still be in progress (see RFC 4340, 10.3).
 111                  * The same applies to Ack Vectors, as these depend on the CCID.
 112                  *
 113                  */
 114                 if (dreq != NULL && (opt >= 128 ||
 115                     opt == DCCPO_ACK_VECTOR_0 || opt == DCCPO_ACK_VECTOR_1))
 116                         goto ignore_option;
 117
 118                 switch (opt) {
 119                 case DCCPO_PADDING:
 120                         break;
 121                 case DCCPO_MANDATORY:
 122                         if (mandatory)
 123                                 goto out_invalid_option;
 124                         if (pkt_type != DCCP_PKT_DATA)
 125                                 mandatory = 1;
 126                         break;
 127                 case DCCPO_NDP_COUNT:
 128                         if (len > 6)
 129                                 goto out_invalid_option;
 130
 131                         opt_recv->dccpor_ndp = dccp_decode_value_var(value, len);
 132                         dccp_pr_debug("%s opt: NDP count=%llu\n", dccp_role(sk),
 133                                       (unsigned long long)opt_recv->dccpor_ndp);
 134                         break;
 135                 case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R:
 136                         if (pkt_type == DCCP_PKT_DATA)      /* RFC 4340, 6 */
 137                                 break;
 138                         rc = dccp_feat_parse_options(sk, dreq, mandatory, opt,
 139                                                     *value, value + 1, len - 1);
 140                         if (rc)
 141                                 goto out_featneg_failed;
 142                         break;
 143                 case DCCPO_ACK_VECTOR_0:
 144                 case DCCPO_ACK_VECTOR_1:
 145                         if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
 146                                 break;
 147                         if (dp->dccps_hc_rx_ackvec != NULL &&
 148                             dccp_ackvec_parse(sk, skb, &ackno, opt, value, len))
 149                                 goto out_invalid_option;
 150                         break;
 151                 case DCCPO_TIMESTAMP:
 152                         if (len != 4)
 153                                 goto out_invalid_option;
 154                         /*
 155                          * RFC 4340 13.1: "The precise time corresponding to
 156                          * Timestamp Value zero is not specified". We use
 157                          * zero to indicate absence of a meaningful timestamp.
 158                          */
 159                         opt_val = get_unaligned((__be32 *)value);
 160                         if (unlikely(opt_val == 0)) {
 161                                 DCCP_WARN("Timestamp with zero value\n");
 162                                 break;
 163                         }
 164
 165                         if (dreq != NULL) {
 166                                 dreq->dreq_timestamp_echo = ntohl(opt_val);
 167                                 dreq->dreq_timestamp_time = dccp_timestamp();
 168                         } else {
 169                                 opt_recv->dccpor_timestamp =
 170                                         dp->dccps_timestamp_echo = ntohl(opt_val);
 171                                 dp->dccps_timestamp_time = dccp_timestamp();
 172                         }
 173                         dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n",
 174                                       dccp_role(sk), ntohl(opt_val),
 175                                       (unsigned long long)
 176                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
 177                         break;
 178                 case DCCPO_TIMESTAMP_ECHO:
 179                         if (len != 4 && len != 6 && len != 8)
 180                                 goto out_invalid_option;
 181
 182                         opt_val = get_unaligned((__be32 *)value);
 183                         opt_recv->dccpor_timestamp_echo = ntohl(opt_val);
 184
 185                         dccp_pr_debug("%s rx opt: TIMESTAMP_ECHO=%u, len=%d, "
 186                                       "ackno=%llu", dccp_role(sk),
 187                                       opt_recv->dccpor_timestamp_echo,
 188                                       len + 2,
 189                                       (unsigned long long)
 190                                       DCCP_SKB_CB(skb)->dccpd_ack_seq);
 191
 192                         value += 4;
 193
 194                         if (len == 4) {         /* no elapsed time included */
 195                                 dccp_pr_debug_cat("\n");
 196                                 break;
 197                         }
 198
 199                         if (len == 6) {         /* 2-byte elapsed time */
 200                                 __be16 opt_val2 = get_unaligned((__be16 *)value);
 201                                 elapsed_time = ntohs(opt_val2);
 202                         } else {                /* 4-byte elapsed time */
 203                                 opt_val = get_unaligned((__be32 *)value);
 204                                 elapsed_time = ntohl(opt_val);
 205                         }
 206
 207                         dccp_pr_debug_cat(", ELAPSED_TIME=%u\n", elapsed_time);
 208
 209                         /* Give precedence to the biggest ELAPSED_TIME */
 210                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
 211                                 opt_recv->dccpor_elapsed_time = elapsed_time;
 212                         break;
 213                 case DCCPO_ELAPSED_TIME:
 214                         if (dccp_packet_without_ack(skb))   /* RFC 4340, 13.2 */
 215                                 break;
 216
 217                         if (len == 2) {
 218                                 __be16 opt_val2 = get_unaligned((__be16 *)value);
 219                                 elapsed_time = ntohs(opt_val2);
 220                         } else if (len == 4) {
 221                                 opt_val = get_unaligned((__be32 *)value);
 222                                 elapsed_time = ntohl(opt_val);
 223                         } else {
 224                                 goto out_invalid_option;
 225                         }
 226
 227                         if (elapsed_time > opt_recv->dccpor_elapsed_time)
 228                                 opt_recv->dccpor_elapsed_time = elapsed_time;
 229
 230                         dccp_pr_debug("%s rx opt: ELAPSED_TIME=%d\n",
 231                                       dccp_role(sk), elapsed_time);
 232                         break;
 233                 case 128 ... 191: {
 234                         const u16 idx = value - options;
 235
 236                         if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk,
 237                                                      opt, len, idx,
 238                                                      value) != 0)
 239                                 goto out_invalid_option;
 240                 }
 241                         break;
 242                 case 192 ... 255: {
 243                         const u16 idx = value - options;
 244
 245                         if (ccid_hc_tx_parse_options(dp->dccps_hc_tx_ccid, sk,
 246                                                      opt, len, idx,
 247                                                      value) != 0)
 248                                 goto out_invalid_option;
 249                 }
 250                         break;
 251                 default:
 252                         DCCP_CRIT("DCCP(%p): option %d(len=%d) not "
 253                                   "implemented, ignoring", sk, opt, len);
 254                         break;
 255                 }
 256 ignore_option:
 257                 if (opt != DCCPO_MANDATORY)
 258                         mandatory = 0;
 259         }
 260
 261         /* mandatory was the last byte in option list -> reset connection */
 262         if (mandatory)
 263                 goto out_invalid_option;
 264
 265 out_nonsensical_length:
 266         /* RFC 4340, 5.8: ignore option and all remaining option space */
 267         return 0;
 268
 269 out_invalid_option:
 270         DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
 271         rc = DCCP_RESET_CODE_OPTION_ERROR;
 272 out_featneg_failed:
 273         DCCP_WARN("DCCP(%p): Option %d (len=%d) error=%u\n", sk, opt, len, rc);
 274         DCCP_SKB_CB(skb)->dccpd_reset_code = rc;
 275         DCCP_SKB_CB(skb)->dccpd_reset_data[0] = opt;
 276         DCCP_SKB_CB(skb)->dccpd_reset_data[1] = len > 0 ? value[0] : 0;
 277         DCCP_SKB_CB(skb)->dccpd_reset_data[2] = len > 1 ? value[1] : 0;
 278         return -1;
 279 }
 280
 281 EXPORT_SYMBOL_GPL(dccp_parse_options);
 282
 283 void dccp_encode_value_var(const u64 value, u8 *to, const u8 len)
 284 {
 285         if (len >= DCCP_OPTVAL_MAXLEN)
 286                 *to++ = (value & 0xFF0000000000ull) >> 40;
 287         if (len > 4)
 288                 *to++ = (value & 0xFF00000000ull) >> 32;
 289         if (len > 3)
 290                 *to++ = (value & 0xFF000000) >> 24;
 291         if (len > 2)
 292                 *to++ = (value & 0xFF0000) >> 16;
 293         if (len > 1)
 294                 *to++ = (value & 0xFF00) >> 8;
 295         if (len > 0)
 296                 *to++ = (value & 0xFF);
 297 }
 298
 299 static inline u8 dccp_ndp_len(const u64 ndp)
 300 {
 301         if (likely(ndp <= 0xFF))
 302                 return 1;
 303         return likely(ndp <= USHORT_MAX) ? 2 : (ndp <= UINT_MAX ? 4 : 6);
 304 }
 305
 306 int dccp_insert_option(struct sock *sk, struct sk_buff *skb,
 307                         const unsigned char option,
 308                         const void *value, const unsigned char len)
 309 {
 310         unsigned char *to;
 311
 312         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 2 > DCCP_MAX_OPT_LEN)
 313                 return -1;
 314
 315         DCCP_SKB_CB(skb)->dccpd_opt_len += len + 2;
 316
 317         to    = skb_push(skb, len + 2);
 318         *to++ = option;
 319         *to++ = len + 2;
 320
 321         memcpy(to, value, len);
 322         return 0;
 323 }
 324
 325 EXPORT_SYMBOL_GPL(dccp_insert_option);
 326
 327 static int dccp_insert_option_ndp(struct sock *sk, struct sk_buff *skb)
 328 {
 329         struct dccp_sock *dp = dccp_sk(sk);
 330         u64 ndp = dp->dccps_ndp_count;
 331
 332         if (dccp_non_data_packet(skb))
 333                 ++dp->dccps_ndp_count;
 334         else
 335                 dp->dccps_ndp_count = 0;
 336
 337         if (ndp > 0) {
 338                 unsigned char *ptr;
 339                 const int ndp_len = dccp_ndp_len(ndp);
 340                 const int len = ndp_len + 2;
 341
 342                 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
 343                         return -1;
 344
 345                 DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 346
 347                 ptr = skb_push(skb, len);
 348                 *ptr++ = DCCPO_NDP_COUNT;
 349                 *ptr++ = len;
 350                 dccp_encode_value_var(ndp, ptr, ndp_len);
 351         }
 352
 353         return 0;
 354 }
 355
 356 static inline int dccp_elapsed_time_len(const u32 elapsed_time)
 357 {
 358         return elapsed_time == 0 ? 0 : elapsed_time <= 0xFFFF ? 2 : 4;
 359 }
 360
 361 int dccp_insert_option_elapsed_time(struct sock *sk, struct sk_buff *skb,
 362                                     u32 elapsed_time)
 363 {
 364         const int elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
 365         const int len = 2 + elapsed_time_len;
 366         unsigned char *to;
 367
 368         if (elapsed_time_len == 0)
 369                 return 0;
 370
 371         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
 372                 return -1;
 373
 374         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 375
 376         to    = skb_push(skb, len);
 377         *to++ = DCCPO_ELAPSED_TIME;
 378         *to++ = len;
 379
 380         if (elapsed_time_len == 2) {
 381                 const __be16 var16 = htons((u16)elapsed_time);
 382                 memcpy(to, &var16, 2);
 383         } else {
 384                 const __be32 var32 = htonl(elapsed_time);
 385                 memcpy(to, &var32, 4);
 386         }
 387
 388         return 0;
 389 }
 390
 391 EXPORT_SYMBOL_GPL(dccp_insert_option_elapsed_time);
 392
 393 int dccp_insert_option_timestamp(struct sock *sk, struct sk_buff *skb)
 394 {
 395         __be32 now = htonl(dccp_timestamp());
 396         /* yes this will overflow but that is the point as we want a
 397          * 10 usec 32 bit timer which mean it wraps every 11.9 hours */
 398
 399         return dccp_insert_option(sk, skb, DCCPO_TIMESTAMP, &now, sizeof(now));
 400 }
 401
 402 EXPORT_SYMBOL_GPL(dccp_insert_option_timestamp);
 403
 404 static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
 405                                              struct dccp_request_sock *dreq,
 406                                              struct sk_buff *skb)
 407 {
 408         __be32 tstamp_echo;
 409         unsigned char *to;
 410         u32 elapsed_time, elapsed_time_len, len;
 411
 412         if (dreq != NULL) {
 413                 elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time;
 414                 tstamp_echo  = htonl(dreq->dreq_timestamp_echo);
 415                 dreq->dreq_timestamp_echo = 0;
 416         } else {
 417                 elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time;
 418                 tstamp_echo  = htonl(dp->dccps_timestamp_echo);
 419                 dp->dccps_timestamp_echo = 0;
 420         }
 421
 422         elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
 423         len = 6 + elapsed_time_len;
 424
 425         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
 426                 return -1;
 427
 428         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 429
 430         to    = skb_push(skb, len);
 431         *to++ = DCCPO_TIMESTAMP_ECHO;
 432         *to++ = len;
 433
 434         memcpy(to, &tstamp_echo, 4);
 435         to += 4;
 436
 437         if (elapsed_time_len == 2) {
 438                 const __be16 var16 = htons((u16)elapsed_time);
 439                 memcpy(to, &var16, 2);
 440         } else if (elapsed_time_len == 4) {
 441                 const __be32 var32 = htonl(elapsed_time);
 442                 memcpy(to, &var32, 4);
 443         }
 444
 445         return 0;
 446 }
 447
 448 /**
 449  * dccp_insert_option_mandatory  -  Mandatory option (5.8.2)
 450  * Note that since we are using skb_push, this function needs to be called
 451  * _after_ inserting the option it is supposed to influence (stack order).
 452  */
 453 int dccp_insert_option_mandatory(struct sk_buff *skb)
 454 {
 455         if (DCCP_SKB_CB(skb)->dccpd_opt_len >= DCCP_MAX_OPT_LEN)
 456                 return -1;
 457
 458         DCCP_SKB_CB(skb)->dccpd_opt_len++;
 459         *skb_push(skb, 1) = DCCPO_MANDATORY;
 460         return 0;
 461 }
 462
 463 /**
 464  * dccp_insert_fn_opt  -  Insert single Feature-Negotiation option into @skb
 465  * @type: %DCCPO_CHANGE_L, %DCCPO_CHANGE_R, %DCCPO_CONFIRM_L, %DCCPO_CONFIRM_R
 466  * @feat: one out of %dccp_feature_numbers
 467  * @val: NN value or SP array (preferred element first) to copy
 468  * @len: true length of @val in bytes (excluding first element repetition)
 469  * @repeat_first: whether to copy the first element of @val twice
 470  * The last argument is used to construct Confirm options, where the preferred
 471  * value and the preference list appear separately (RFC 4340, 6.3.1). Preference
 472  * lists are kept such that the preferred entry is always first, so we only need
 473  * to copy twice, and avoid the overhead of cloning into a bigger array.
 474  */
 475 int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
 476                        u8 *val, u8 len, bool repeat_first)
 477 {
 478         u8 tot_len, *to;
 479
 480         /* take the `Feature' field and possible repetition into account */
 481         if (len > (DCCP_SINGLE_OPT_MAXLEN - 2)) {
 482                 DCCP_WARN("length %u for feature %u too large\n", len, feat);
 483                 return -1;
 484         }
 485
 486         if (unlikely(val == NULL || len == 0))
 487                 len = repeat_first = 0;
 488         tot_len = 3 + repeat_first + len;
 489
 490         if (DCCP_SKB_CB(skb)->dccpd_opt_len + tot_len > DCCP_MAX_OPT_LEN) {
 491                 DCCP_WARN("packet too small for feature %d option!\n", feat);
 492                 return -1;
 493         }
 494         DCCP_SKB_CB(skb)->dccpd_opt_len += tot_len;
 495
 496         to    = skb_push(skb, tot_len);
 497         *to++ = type;
 498         *to++ = tot_len;
 499         *to++ = feat;
 500
 501         if (repeat_first)
 502                 *to++ = *val;
 503         if (len)
 504                 memcpy(to, val, len);
 505
 506         dccp_pr_debug("%s(%s (%d), ...), length %d\n",
 507                       dccp_feat_typename(type),
 508                       dccp_feat_name(feat), feat, len);
 509         return 0;
 510 }
 511
 512 /* The length of all options needs to be a multiple of 4 (5.8) */
 513 static void dccp_insert_option_padding(struct sk_buff *skb)
 514 {
 515         int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4;
 516
 517         if (padding != 0) {
 518                 padding = 4 - padding;
 519                 memset(skb_push(skb, padding), 0, padding);
 520                 DCCP_SKB_CB(skb)->dccpd_opt_len += padding;
 521         }
 522 }
 523
 524 int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
 525 {
 526         struct dccp_sock *dp = dccp_sk(sk);
 527
 528         DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
 529
 530         if (dp->dccps_send_ndp_count && dccp_insert_option_ndp(sk, skb))
 531                 return -1;
 532
 533         if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA) {
 534
 535                 /* Feature Negotiation */
 536                 if (dccp_feat_insert_opts(dp, NULL, skb))
 537                         return -1;
 538
 539                 if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST) {
 540                         /*
 541                          * Obtain RTT sample from Request/Response exchange.
 542                          * This is currently used in CCID 3 initialisation.
 543                          */
 544                         if (dccp_insert_option_timestamp(sk, skb))
 545                                 return -1;
 546
 547                 } else if (dp->dccps_hc_rx_ackvec != NULL &&
 548                            dccp_ackvec_pending(dp->dccps_hc_rx_ackvec) &&
 549                            dccp_insert_option_ackvec(sk, skb)) {
 550                                 return -1;
 551                 }
 552         }
 553
 554         if (dp->dccps_hc_rx_insert_options) {
 555                 if (ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb))
 556                         return -1;
 557                 dp->dccps_hc_rx_insert_options = 0;
 558         }
 559
 560         if (dp->dccps_timestamp_echo != 0 &&
 561             dccp_insert_option_timestamp_echo(dp, NULL, skb))
 562                 return -1;
 563
 564         dccp_insert_option_padding(skb);
 565         return 0;
 566 }
 567
 568 int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb)
 569 {
 570         DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
 571
 572         if (dccp_feat_insert_opts(NULL, dreq, skb))
 573                 return -1;
 574
 575         if (dreq->dreq_timestamp_echo != 0 &&
 576             dccp_insert_option_timestamp_echo(NULL, dreq, skb))
 577                 return -1;
 578
 579         dccp_insert_option_padding(skb);
 580         return 0;
 581 }