1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * net/dccp/options.c 4 * 5 * An implementation of the DCCP protocol 6 * Copyright (c) 2005 Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org> 7 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net> 8 * Copyright (c) 2005 Ian McDonald <ian.mcdonald@jandi.co.nz> 9 */ 10 #include <linux/dccp.h> 11 #include <linux/module.h> 12 #include <linux/types.h> 13 #include <asm/unaligned.h> 14 #include <linux/kernel.h> 15 #include <linux/skbuff.h> 16 17 #include "ackvec.h" 18 #include "ccid.h" 19 #include "dccp.h" 20 #include "feat.h" 21 22 u64 dccp_decode_value_var(const u8 *bf, const u8 len) 23 { 24 u64 value = 0; 25 26 if (len >= DCCP_OPTVAL_MAXLEN) 27 value += ((u64)*bf++) << 40; 28 if (len > 4) 29 value += ((u64)*bf++) << 32; 30 if (len > 3) 31 value += ((u64)*bf++) << 24; 32 if (len > 2) 33 value += ((u64)*bf++) << 16; 34 if (len > 1) 35 value += ((u64)*bf++) << 8; 36 if (len > 0) 37 value += *bf; 38 39 return value; 40 } 41 42 /** 43 * dccp_parse_options - Parse DCCP options present in @skb 44 * @sk: client|server|listening dccp socket (when @dreq != NULL) 45 * @dreq: request socket to use during connection setup, or NULL 46 * @skb: frame to parse 47 */ 48 int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq, 49 struct sk_buff *skb) 50 { 51 struct dccp_sock *dp = dccp_sk(sk); 52 const struct dccp_hdr *dh = dccp_hdr(skb); 53 const u8 pkt_type = DCCP_SKB_CB(skb)->dccpd_type; 54 unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb); 55 unsigned char *opt_ptr = options; 56 const unsigned char *opt_end = (unsigned char *)dh + 57 (dh->dccph_doff * 4); 58 struct dccp_options_received *opt_recv = &dp->dccps_options_received; 59 unsigned char opt, len; 60 unsigned char *value; 61 u32 elapsed_time; 62 __be32 opt_val; 63 int rc; 64 int mandatory = 0; 65 66 memset(opt_recv, 0, sizeof(*opt_recv)); 67 68 opt = len = 0; 69 while (opt_ptr != opt_end) { 70 opt = *opt_ptr++; 71 len = 0; 72 value = NULL; 73 74 /* Check if this isn't a single byte option */ 75 if (opt > DCCPO_MAX_RESERVED) { 76 if (opt_ptr == opt_end) 77 goto out_nonsensical_length; 78 79 len = *opt_ptr++; 80 if (len < 2) 81 goto out_nonsensical_length; 82 /* 83 * Remove the type and len fields, leaving 84 * just the value size 85 */ 86 len -= 2; 87 value = opt_ptr; 88 opt_ptr += len; 89 90 if (opt_ptr > opt_end) 91 goto out_nonsensical_length; 92 } 93 94 /* 95 * CCID-specific options are ignored during connection setup, as 96 * negotiation may still be in progress (see RFC 4340, 10.3). 97 * The same applies to Ack Vectors, as these depend on the CCID. 98 */ 99 if (dreq != NULL && (opt >= DCCPO_MIN_RX_CCID_SPECIFIC || 100 opt == DCCPO_ACK_VECTOR_0 || opt == DCCPO_ACK_VECTOR_1)) 101 goto ignore_option; 102 103 switch (opt) { 104 case DCCPO_PADDING: 105 break; 106 case DCCPO_MANDATORY: 107 if (mandatory) 108 goto out_invalid_option; 109 if (pkt_type != DCCP_PKT_DATA) 110 mandatory = 1; 111 break; 112 case DCCPO_NDP_COUNT: 113 if (len > 6) 114 goto out_invalid_option; 115 116 opt_recv->dccpor_ndp = dccp_decode_value_var(value, len); 117 dccp_pr_debug("%s opt: NDP count=%llu\n", dccp_role(sk), 118 (unsigned long long)opt_recv->dccpor_ndp); 119 break; 120 case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R: 121 if (pkt_type == DCCP_PKT_DATA) /* RFC 4340, 6 */ 122 break; 123 if (len == 0) 124 goto out_invalid_option; 125 rc = dccp_feat_parse_options(sk, dreq, mandatory, opt, 126 *value, value + 1, len - 1); 127 if (rc) 128 goto out_featneg_failed; 129 break; 130 case DCCPO_TIMESTAMP: 131 if (len != 4) 132 goto out_invalid_option; 133 /* 134 * RFC 4340 13.1: "The precise time corresponding to 135 * Timestamp Value zero is not specified". We use 136 * zero to indicate absence of a meaningful timestamp. 137 */ 138 opt_val = get_unaligned((__be32 *)value); 139 if (unlikely(opt_val == 0)) { 140 DCCP_WARN("Timestamp with zero value\n"); 141 break; 142 } 143 144 if (dreq != NULL) { 145 dreq->dreq_timestamp_echo = ntohl(opt_val); 146 dreq->dreq_timestamp_time = dccp_timestamp(); 147 } else { 148 opt_recv->dccpor_timestamp = 149 dp->dccps_timestamp_echo = ntohl(opt_val); 150 dp->dccps_timestamp_time = dccp_timestamp(); 151 } 152 dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n", 153 dccp_role(sk), ntohl(opt_val), 154 (unsigned long long) 155 DCCP_SKB_CB(skb)->dccpd_ack_seq); 156 /* schedule an Ack in case this sender is quiescent */ 157 inet_csk_schedule_ack(sk); 158 break; 159 case DCCPO_TIMESTAMP_ECHO: 160 if (len != 4 && len != 6 && len != 8) 161 goto out_invalid_option; 162 163 opt_val = get_unaligned((__be32 *)value); 164 opt_recv->dccpor_timestamp_echo = ntohl(opt_val); 165 166 dccp_pr_debug("%s rx opt: TIMESTAMP_ECHO=%u, len=%d, " 167 "ackno=%llu", dccp_role(sk), 168 opt_recv->dccpor_timestamp_echo, 169 len + 2, 170 (unsigned long long) 171 DCCP_SKB_CB(skb)->dccpd_ack_seq); 172 173 value += 4; 174 175 if (len == 4) { /* no elapsed time included */ 176 dccp_pr_debug_cat("\n"); 177 break; 178 } 179 180 if (len == 6) { /* 2-byte elapsed time */ 181 __be16 opt_val2 = get_unaligned((__be16 *)value); 182 elapsed_time = ntohs(opt_val2); 183 } else { /* 4-byte elapsed time */ 184 opt_val = get_unaligned((__be32 *)value); 185 elapsed_time = ntohl(opt_val); 186 } 187 188 dccp_pr_debug_cat(", ELAPSED_TIME=%u\n", elapsed_time); 189 190 /* Give precedence to the biggest ELAPSED_TIME */ 191 if (elapsed_time > opt_recv->dccpor_elapsed_time) 192 opt_recv->dccpor_elapsed_time = elapsed_time; 193 break; 194 case DCCPO_ELAPSED_TIME: 195 if (dccp_packet_without_ack(skb)) /* RFC 4340, 13.2 */ 196 break; 197 198 if (len == 2) { 199 __be16 opt_val2 = get_unaligned((__be16 *)value); 200 elapsed_time = ntohs(opt_val2); 201 } else if (len == 4) { 202 opt_val = get_unaligned((__be32 *)value); 203 elapsed_time = ntohl(opt_val); 204 } else { 205 goto out_invalid_option; 206 } 207 208 if (elapsed_time > opt_recv->dccpor_elapsed_time) 209 opt_recv->dccpor_elapsed_time = elapsed_time; 210 211 dccp_pr_debug("%s rx opt: ELAPSED_TIME=%d\n", 212 dccp_role(sk), elapsed_time); 213 break; 214 case DCCPO_MIN_RX_CCID_SPECIFIC ... DCCPO_MAX_RX_CCID_SPECIFIC: 215 if (ccid_hc_rx_parse_options(dp->dccps_hc_rx_ccid, sk, 216 pkt_type, opt, value, len)) 217 goto out_invalid_option; 218 break; 219 case DCCPO_ACK_VECTOR_0: 220 case DCCPO_ACK_VECTOR_1: 221 if (dccp_packet_without_ack(skb)) /* RFC 4340, 11.4 */ 222 break; 223 /* 224 * Ack vectors are processed by the TX CCID if it is 225 * interested. The RX CCID need not parse Ack Vectors, 226 * since it is only interested in clearing old state. 227 */ 228 /* fall through */ 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(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 static int dccp_insert_option_timestamp(struct sk_buff *skb) 344 { 345 __be32 now = htonl(dccp_timestamp()); 346 /* yes this will overflow but that is the point as we want a 347 * 10 usec 32 bit timer which mean it wraps every 11.9 hours */ 348 349 return dccp_insert_option(skb, DCCPO_TIMESTAMP, &now, sizeof(now)); 350 } 351 352 static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp, 353 struct dccp_request_sock *dreq, 354 struct sk_buff *skb) 355 { 356 __be32 tstamp_echo; 357 unsigned char *to; 358 u32 elapsed_time, elapsed_time_len, len; 359 360 if (dreq != NULL) { 361 elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time; 362 tstamp_echo = htonl(dreq->dreq_timestamp_echo); 363 dreq->dreq_timestamp_echo = 0; 364 } else { 365 elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time; 366 tstamp_echo = htonl(dp->dccps_timestamp_echo); 367 dp->dccps_timestamp_echo = 0; 368 } 369 370 elapsed_time_len = dccp_elapsed_time_len(elapsed_time); 371 len = 6 + elapsed_time_len; 372 373 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) 374 return -1; 375 376 DCCP_SKB_CB(skb)->dccpd_opt_len += len; 377 378 to = skb_push(skb, len); 379 *to++ = DCCPO_TIMESTAMP_ECHO; 380 *to++ = len; 381 382 memcpy(to, &tstamp_echo, 4); 383 to += 4; 384 385 if (elapsed_time_len == 2) { 386 const __be16 var16 = htons((u16)elapsed_time); 387 memcpy(to, &var16, 2); 388 } else if (elapsed_time_len == 4) { 389 const __be32 var32 = htonl(elapsed_time); 390 memcpy(to, &var32, 4); 391 } 392 393 return 0; 394 } 395 396 static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb) 397 { 398 struct dccp_sock *dp = dccp_sk(sk); 399 struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec; 400 struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb); 401 const u16 buflen = dccp_ackvec_buflen(av); 402 /* Figure out how many options do we need to represent the ackvec */ 403 const u8 nr_opts = DIV_ROUND_UP(buflen, DCCP_SINGLE_OPT_MAXLEN); 404 u16 len = buflen + 2 * nr_opts; 405 u8 i, nonce = 0; 406 const unsigned char *tail, *from; 407 unsigned char *to; 408 409 if (dcb->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) { 410 DCCP_WARN("Lacking space for %u bytes on %s packet\n", len, 411 dccp_packet_name(dcb->dccpd_type)); 412 return -1; 413 } 414 /* 415 * Since Ack Vectors are variable-length, we can not always predict 416 * their size. To catch exception cases where the space is running out 417 * on the skb, a separate Sync is scheduled to carry the Ack Vector. 418 */ 419 if (len > DCCPAV_MIN_OPTLEN && 420 len + dcb->dccpd_opt_len + skb->len > dp->dccps_mss_cache) { 421 DCCP_WARN("No space left for Ack Vector (%u) on skb (%u+%u), " 422 "MPS=%u ==> reduce payload size?\n", len, skb->len, 423 dcb->dccpd_opt_len, dp->dccps_mss_cache); 424 dp->dccps_sync_scheduled = 1; 425 return 0; 426 } 427 dcb->dccpd_opt_len += len; 428 429 to = skb_push(skb, len); 430 len = buflen; 431 from = av->av_buf + av->av_buf_head; 432 tail = av->av_buf + DCCPAV_MAX_ACKVEC_LEN; 433 434 for (i = 0; i < nr_opts; ++i) { 435 int copylen = len; 436 437 if (len > DCCP_SINGLE_OPT_MAXLEN) 438 copylen = DCCP_SINGLE_OPT_MAXLEN; 439 440 /* 441 * RFC 4340, 12.2: Encode the Nonce Echo for this Ack Vector via 442 * its type; ack_nonce is the sum of all individual buf_nonce's. 443 */ 444 nonce ^= av->av_buf_nonce[i]; 445 446 *to++ = DCCPO_ACK_VECTOR_0 + av->av_buf_nonce[i]; 447 *to++ = copylen + 2; 448 449 /* Check if buf_head wraps */ 450 if (from + copylen > tail) { 451 const u16 tailsize = tail - from; 452 453 memcpy(to, from, tailsize); 454 to += tailsize; 455 len -= tailsize; 456 copylen -= tailsize; 457 from = av->av_buf; 458 } 459 460 memcpy(to, from, copylen); 461 from += copylen; 462 to += copylen; 463 len -= copylen; 464 } 465 /* 466 * Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340. 467 */ 468 if (dccp_ackvec_update_records(av, dcb->dccpd_seq, nonce)) 469 return -ENOBUFS; 470 return 0; 471 } 472 473 /** 474 * dccp_insert_option_mandatory - Mandatory option (5.8.2) 475 * @skb: frame into which to insert option 476 * 477 * Note that since we are using skb_push, this function needs to be called 478 * _after_ inserting the option it is supposed to influence (stack order). 479 */ 480 int dccp_insert_option_mandatory(struct sk_buff *skb) 481 { 482 if (DCCP_SKB_CB(skb)->dccpd_opt_len >= DCCP_MAX_OPT_LEN) 483 return -1; 484 485 DCCP_SKB_CB(skb)->dccpd_opt_len++; 486 *(u8 *)skb_push(skb, 1) = DCCPO_MANDATORY; 487 return 0; 488 } 489 490 /** 491 * dccp_insert_fn_opt - Insert single Feature-Negotiation option into @skb 492 * @skb: frame to insert feature negotiation option into 493 * @type: %DCCPO_CHANGE_L, %DCCPO_CHANGE_R, %DCCPO_CONFIRM_L, %DCCPO_CONFIRM_R 494 * @feat: one out of %dccp_feature_numbers 495 * @val: NN value or SP array (preferred element first) to copy 496 * @len: true length of @val in bytes (excluding first element repetition) 497 * @repeat_first: whether to copy the first element of @val twice 498 * 499 * The last argument is used to construct Confirm options, where the preferred 500 * value and the preference list appear separately (RFC 4340, 6.3.1). Preference 501 * lists are kept such that the preferred entry is always first, so we only need 502 * to copy twice, and avoid the overhead of cloning into a bigger array. 503 */ 504 int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat, 505 u8 *val, u8 len, bool repeat_first) 506 { 507 u8 tot_len, *to; 508 509 /* take the `Feature' field and possible repetition into account */ 510 if (len > (DCCP_SINGLE_OPT_MAXLEN - 2)) { 511 DCCP_WARN("length %u for feature %u too large\n", len, feat); 512 return -1; 513 } 514 515 if (unlikely(val == NULL || len == 0)) 516 len = repeat_first = false; 517 tot_len = 3 + repeat_first + len; 518 519 if (DCCP_SKB_CB(skb)->dccpd_opt_len + tot_len > DCCP_MAX_OPT_LEN) { 520 DCCP_WARN("packet too small for feature %d option!\n", feat); 521 return -1; 522 } 523 DCCP_SKB_CB(skb)->dccpd_opt_len += tot_len; 524 525 to = skb_push(skb, tot_len); 526 *to++ = type; 527 *to++ = tot_len; 528 *to++ = feat; 529 530 if (repeat_first) 531 *to++ = *val; 532 if (len) 533 memcpy(to, val, len); 534 return 0; 535 } 536 537 /* The length of all options needs to be a multiple of 4 (5.8) */ 538 static void dccp_insert_option_padding(struct sk_buff *skb) 539 { 540 int padding = DCCP_SKB_CB(skb)->dccpd_opt_len % 4; 541 542 if (padding != 0) { 543 padding = 4 - padding; 544 memset(skb_push(skb, padding), 0, padding); 545 DCCP_SKB_CB(skb)->dccpd_opt_len += padding; 546 } 547 } 548 549 int dccp_insert_options(struct sock *sk, struct sk_buff *skb) 550 { 551 struct dccp_sock *dp = dccp_sk(sk); 552 553 DCCP_SKB_CB(skb)->dccpd_opt_len = 0; 554 555 if (dp->dccps_send_ndp_count && dccp_insert_option_ndp(sk, skb)) 556 return -1; 557 558 if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA) { 559 560 /* Feature Negotiation */ 561 if (dccp_feat_insert_opts(dp, NULL, skb)) 562 return -1; 563 564 if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST) { 565 /* 566 * Obtain RTT sample from Request/Response exchange. 567 * This is currently used for TFRC initialisation. 568 */ 569 if (dccp_insert_option_timestamp(skb)) 570 return -1; 571 572 } else if (dccp_ackvec_pending(sk) && 573 dccp_insert_option_ackvec(sk, skb)) { 574 return -1; 575 } 576 } 577 578 if (dp->dccps_hc_rx_insert_options) { 579 if (ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb)) 580 return -1; 581 dp->dccps_hc_rx_insert_options = 0; 582 } 583 584 if (dp->dccps_timestamp_echo != 0 && 585 dccp_insert_option_timestamp_echo(dp, NULL, skb)) 586 return -1; 587 588 dccp_insert_option_padding(skb); 589 return 0; 590 } 591 592 int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb) 593 { 594 DCCP_SKB_CB(skb)->dccpd_opt_len = 0; 595 596 if (dccp_feat_insert_opts(NULL, dreq, skb)) 597 return -1; 598 599 /* Obtain RTT sample from Response/Ack exchange (used by TFRC). */ 600 if (dccp_insert_option_timestamp(skb)) 601 return -1; 602 603 if (dreq->dreq_timestamp_echo != 0 && 604 dccp_insert_option_timestamp_echo(NULL, dreq, skb)) 605 return -1; 606 607 dccp_insert_option_padding(skb); 608 return 0; 609 } 610