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