1 // SPDX-License-Identifier: GPL-2.0 2 /* Multipath TCP 3 * 4 * Copyright (c) 2017 - 2019, Intel Corporation. 5 */ 6 7 #define pr_fmt(fmt) "MPTCP: " fmt 8 9 #include <linux/kernel.h> 10 #include <crypto/sha.h> 11 #include <net/tcp.h> 12 #include <net/mptcp.h> 13 #include "protocol.h" 14 #include "mib.h" 15 16 static bool mptcp_cap_flag_sha256(u8 flags) 17 { 18 return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256; 19 } 20 21 static void mptcp_parse_option(const struct sk_buff *skb, 22 const unsigned char *ptr, int opsize, 23 struct mptcp_options_received *mp_opt) 24 { 25 u8 subtype = *ptr >> 4; 26 int expected_opsize; 27 u8 version; 28 u8 flags; 29 30 switch (subtype) { 31 case MPTCPOPT_MP_CAPABLE: 32 /* strict size checking */ 33 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) { 34 if (skb->len > tcp_hdr(skb)->doff << 2) 35 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA; 36 else 37 expected_opsize = TCPOLEN_MPTCP_MPC_ACK; 38 } else { 39 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) 40 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK; 41 else 42 expected_opsize = TCPOLEN_MPTCP_MPC_SYN; 43 } 44 if (opsize != expected_opsize) 45 break; 46 47 /* try to be gentle vs future versions on the initial syn */ 48 version = *ptr++ & MPTCP_VERSION_MASK; 49 if (opsize != TCPOLEN_MPTCP_MPC_SYN) { 50 if (version != MPTCP_SUPPORTED_VERSION) 51 break; 52 } else if (version < MPTCP_SUPPORTED_VERSION) { 53 break; 54 } 55 56 flags = *ptr++; 57 if (!mptcp_cap_flag_sha256(flags) || 58 (flags & MPTCP_CAP_EXTENSIBILITY)) 59 break; 60 61 /* RFC 6824, Section 3.1: 62 * "For the Checksum Required bit (labeled "A"), if either 63 * host requires the use of checksums, checksums MUST be used. 64 * In other words, the only way for checksums not to be used 65 * is if both hosts in their SYNs set A=0." 66 * 67 * Section 3.3.0: 68 * "If a checksum is not present when its use has been 69 * negotiated, the receiver MUST close the subflow with a RST as 70 * it is considered broken." 71 * 72 * We don't implement DSS checksum - fall back to TCP. 73 */ 74 if (flags & MPTCP_CAP_CHECKSUM_REQD) 75 break; 76 77 mp_opt->mp_capable = 1; 78 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) { 79 mp_opt->sndr_key = get_unaligned_be64(ptr); 80 ptr += 8; 81 } 82 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) { 83 mp_opt->rcvr_key = get_unaligned_be64(ptr); 84 ptr += 8; 85 } 86 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA) { 87 /* Section 3.1.: 88 * "the data parameters in a MP_CAPABLE are semantically 89 * equivalent to those in a DSS option and can be used 90 * interchangeably." 91 */ 92 mp_opt->dss = 1; 93 mp_opt->use_map = 1; 94 mp_opt->mpc_map = 1; 95 mp_opt->data_len = get_unaligned_be16(ptr); 96 ptr += 2; 97 } 98 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d", 99 version, flags, opsize, mp_opt->sndr_key, 100 mp_opt->rcvr_key, mp_opt->data_len); 101 break; 102 103 case MPTCPOPT_MP_JOIN: 104 mp_opt->mp_join = 1; 105 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) { 106 mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP; 107 mp_opt->join_id = *ptr++; 108 mp_opt->token = get_unaligned_be32(ptr); 109 ptr += 4; 110 mp_opt->nonce = get_unaligned_be32(ptr); 111 ptr += 4; 112 pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u", 113 mp_opt->backup, mp_opt->join_id, 114 mp_opt->token, mp_opt->nonce); 115 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) { 116 mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP; 117 mp_opt->join_id = *ptr++; 118 mp_opt->thmac = get_unaligned_be64(ptr); 119 ptr += 8; 120 mp_opt->nonce = get_unaligned_be32(ptr); 121 ptr += 4; 122 pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u", 123 mp_opt->backup, mp_opt->join_id, 124 mp_opt->thmac, mp_opt->nonce); 125 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) { 126 ptr += 2; 127 memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN); 128 pr_debug("MP_JOIN hmac"); 129 } else { 130 pr_warn("MP_JOIN bad option size"); 131 mp_opt->mp_join = 0; 132 } 133 break; 134 135 case MPTCPOPT_DSS: 136 pr_debug("DSS"); 137 ptr++; 138 139 /* we must clear 'mpc_map' be able to detect MP_CAPABLE 140 * map vs DSS map in mptcp_incoming_options(), and reconstruct 141 * map info accordingly 142 */ 143 mp_opt->mpc_map = 0; 144 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK; 145 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0; 146 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0; 147 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0; 148 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0; 149 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK); 150 151 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d", 152 mp_opt->data_fin, mp_opt->dsn64, 153 mp_opt->use_map, mp_opt->ack64, 154 mp_opt->use_ack); 155 156 expected_opsize = TCPOLEN_MPTCP_DSS_BASE; 157 158 if (mp_opt->use_ack) { 159 if (mp_opt->ack64) 160 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64; 161 else 162 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32; 163 } 164 165 if (mp_opt->use_map) { 166 if (mp_opt->dsn64) 167 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64; 168 else 169 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32; 170 } 171 172 /* RFC 6824, Section 3.3: 173 * If a checksum is present, but its use had 174 * not been negotiated in the MP_CAPABLE handshake, 175 * the checksum field MUST be ignored. 176 */ 177 if (opsize != expected_opsize && 178 opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) 179 break; 180 181 mp_opt->dss = 1; 182 183 if (mp_opt->use_ack) { 184 if (mp_opt->ack64) { 185 mp_opt->data_ack = get_unaligned_be64(ptr); 186 ptr += 8; 187 } else { 188 mp_opt->data_ack = get_unaligned_be32(ptr); 189 ptr += 4; 190 } 191 192 pr_debug("data_ack=%llu", mp_opt->data_ack); 193 } 194 195 if (mp_opt->use_map) { 196 if (mp_opt->dsn64) { 197 mp_opt->data_seq = get_unaligned_be64(ptr); 198 ptr += 8; 199 } else { 200 mp_opt->data_seq = get_unaligned_be32(ptr); 201 ptr += 4; 202 } 203 204 mp_opt->subflow_seq = get_unaligned_be32(ptr); 205 ptr += 4; 206 207 mp_opt->data_len = get_unaligned_be16(ptr); 208 ptr += 2; 209 210 pr_debug("data_seq=%llu subflow_seq=%u data_len=%u", 211 mp_opt->data_seq, mp_opt->subflow_seq, 212 mp_opt->data_len); 213 } 214 215 break; 216 217 case MPTCPOPT_ADD_ADDR: 218 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO; 219 if (!mp_opt->echo) { 220 if (opsize == TCPOLEN_MPTCP_ADD_ADDR || 221 opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT) 222 mp_opt->family = MPTCP_ADDR_IPVERSION_4; 223 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 224 else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 || 225 opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT) 226 mp_opt->family = MPTCP_ADDR_IPVERSION_6; 227 #endif 228 else 229 break; 230 } else { 231 if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE || 232 opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) 233 mp_opt->family = MPTCP_ADDR_IPVERSION_4; 234 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 235 else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE || 236 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) 237 mp_opt->family = MPTCP_ADDR_IPVERSION_6; 238 #endif 239 else 240 break; 241 } 242 243 mp_opt->add_addr = 1; 244 mp_opt->addr_id = *ptr++; 245 pr_debug("ADD_ADDR: id=%d, echo=%d", mp_opt->addr_id, mp_opt->echo); 246 if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) { 247 memcpy((u8 *)&mp_opt->addr.s_addr, (u8 *)ptr, 4); 248 ptr += 4; 249 if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT || 250 opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) { 251 mp_opt->port = get_unaligned_be16(ptr); 252 ptr += 2; 253 } 254 } 255 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 256 else { 257 memcpy(mp_opt->addr6.s6_addr, (u8 *)ptr, 16); 258 ptr += 16; 259 if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT || 260 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) { 261 mp_opt->port = get_unaligned_be16(ptr); 262 ptr += 2; 263 } 264 } 265 #endif 266 if (!mp_opt->echo) { 267 mp_opt->ahmac = get_unaligned_be64(ptr); 268 ptr += 8; 269 } 270 break; 271 272 case MPTCPOPT_RM_ADDR: 273 if (opsize != TCPOLEN_MPTCP_RM_ADDR_BASE) 274 break; 275 276 ptr++; 277 278 mp_opt->rm_addr = 1; 279 mp_opt->rm_id = *ptr++; 280 pr_debug("RM_ADDR: id=%d", mp_opt->rm_id); 281 break; 282 283 default: 284 break; 285 } 286 } 287 288 void mptcp_get_options(const struct sk_buff *skb, 289 struct mptcp_options_received *mp_opt) 290 { 291 const struct tcphdr *th = tcp_hdr(skb); 292 const unsigned char *ptr; 293 int length; 294 295 /* initialize option status */ 296 mp_opt->mp_capable = 0; 297 mp_opt->mp_join = 0; 298 mp_opt->add_addr = 0; 299 mp_opt->ahmac = 0; 300 mp_opt->port = 0; 301 mp_opt->rm_addr = 0; 302 mp_opt->dss = 0; 303 304 length = (th->doff * 4) - sizeof(struct tcphdr); 305 ptr = (const unsigned char *)(th + 1); 306 307 while (length > 0) { 308 int opcode = *ptr++; 309 int opsize; 310 311 switch (opcode) { 312 case TCPOPT_EOL: 313 return; 314 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ 315 length--; 316 continue; 317 default: 318 opsize = *ptr++; 319 if (opsize < 2) /* "silly options" */ 320 return; 321 if (opsize > length) 322 return; /* don't parse partial options */ 323 if (opcode == TCPOPT_MPTCP) 324 mptcp_parse_option(skb, ptr, opsize, mp_opt); 325 ptr += opsize - 2; 326 length -= opsize; 327 } 328 } 329 } 330 331 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb, 332 unsigned int *size, struct mptcp_out_options *opts) 333 { 334 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 335 336 /* we will use snd_isn to detect first pkt [re]transmission 337 * in mptcp_established_options_mp() 338 */ 339 subflow->snd_isn = TCP_SKB_CB(skb)->end_seq; 340 if (subflow->request_mptcp) { 341 opts->suboptions = OPTION_MPTCP_MPC_SYN; 342 *size = TCPOLEN_MPTCP_MPC_SYN; 343 return true; 344 } else if (subflow->request_join) { 345 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token, 346 subflow->local_nonce); 347 opts->suboptions = OPTION_MPTCP_MPJ_SYN; 348 opts->join_id = subflow->local_id; 349 opts->token = subflow->remote_token; 350 opts->nonce = subflow->local_nonce; 351 opts->backup = subflow->request_bkup; 352 *size = TCPOLEN_MPTCP_MPJ_SYN; 353 return true; 354 } 355 return false; 356 } 357 358 /* MP_JOIN client subflow must wait for 4th ack before sending any data: 359 * TCP can't schedule delack timer before the subflow is fully established. 360 * MPTCP uses the delack timer to do 3rd ack retransmissions 361 */ 362 static void schedule_3rdack_retransmission(struct sock *sk) 363 { 364 struct inet_connection_sock *icsk = inet_csk(sk); 365 struct tcp_sock *tp = tcp_sk(sk); 366 unsigned long timeout; 367 368 /* reschedule with a timeout above RTT, as we must look only for drop */ 369 if (tp->srtt_us) 370 timeout = tp->srtt_us << 1; 371 else 372 timeout = TCP_TIMEOUT_INIT; 373 374 WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER); 375 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; 376 icsk->icsk_ack.timeout = timeout; 377 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); 378 } 379 380 static void clear_3rdack_retransmission(struct sock *sk) 381 { 382 struct inet_connection_sock *icsk = inet_csk(sk); 383 384 sk_stop_timer(sk, &icsk->icsk_delack_timer); 385 icsk->icsk_ack.timeout = 0; 386 icsk->icsk_ack.ato = 0; 387 icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER); 388 } 389 390 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb, 391 unsigned int *size, 392 unsigned int remaining, 393 struct mptcp_out_options *opts) 394 { 395 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 396 struct mptcp_ext *mpext; 397 unsigned int data_len; 398 399 /* When skb is not available, we better over-estimate the emitted 400 * options len. A full DSS option (28 bytes) is longer than 401 * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so 402 * tell the caller to defer the estimate to 403 * mptcp_established_options_dss(), which will reserve enough space. 404 */ 405 if (!skb) 406 return false; 407 408 /* MPC/MPJ needed only on 3rd ack packet */ 409 if (subflow->fully_established || 410 subflow->snd_isn != TCP_SKB_CB(skb)->seq) 411 return false; 412 413 if (subflow->mp_capable) { 414 mpext = mptcp_get_ext(skb); 415 data_len = mpext ? mpext->data_len : 0; 416 417 /* we will check ext_copy.data_len in mptcp_write_options() to 418 * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and 419 * TCPOLEN_MPTCP_MPC_ACK 420 */ 421 opts->ext_copy.data_len = data_len; 422 opts->suboptions = OPTION_MPTCP_MPC_ACK; 423 opts->sndr_key = subflow->local_key; 424 opts->rcvr_key = subflow->remote_key; 425 426 /* Section 3.1. 427 * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK 428 * packets that start the first subflow of an MPTCP connection, 429 * as well as the first packet that carries data 430 */ 431 if (data_len > 0) 432 *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4); 433 else 434 *size = TCPOLEN_MPTCP_MPC_ACK; 435 436 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d", 437 subflow, subflow->local_key, subflow->remote_key, 438 data_len); 439 440 return true; 441 } else if (subflow->mp_join) { 442 opts->suboptions = OPTION_MPTCP_MPJ_ACK; 443 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN); 444 *size = TCPOLEN_MPTCP_MPJ_ACK; 445 pr_debug("subflow=%p", subflow); 446 447 schedule_3rdack_retransmission(sk); 448 return true; 449 } 450 return false; 451 } 452 453 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow, 454 struct sk_buff *skb, struct mptcp_ext *ext) 455 { 456 /* The write_seq value has already been incremented, so the actual 457 * sequence number for the DATA_FIN is one less. 458 */ 459 u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1; 460 461 if (!ext->use_map || !skb->len) { 462 /* RFC6824 requires a DSS mapping with specific values 463 * if DATA_FIN is set but no data payload is mapped 464 */ 465 ext->data_fin = 1; 466 ext->use_map = 1; 467 ext->dsn64 = 1; 468 ext->data_seq = data_fin_tx_seq; 469 ext->subflow_seq = 0; 470 ext->data_len = 1; 471 } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) { 472 /* If there's an existing DSS mapping and it is the 473 * final mapping, DATA_FIN consumes 1 additional byte of 474 * mapping space. 475 */ 476 ext->data_fin = 1; 477 ext->data_len++; 478 } 479 } 480 481 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb, 482 unsigned int *size, 483 unsigned int remaining, 484 struct mptcp_out_options *opts) 485 { 486 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 487 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 488 unsigned int dss_size = 0; 489 u64 snd_data_fin_enable; 490 struct mptcp_ext *mpext; 491 unsigned int ack_size; 492 bool ret = false; 493 494 mpext = skb ? mptcp_get_ext(skb) : NULL; 495 snd_data_fin_enable = READ_ONCE(msk->snd_data_fin_enable); 496 497 if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) { 498 unsigned int map_size; 499 500 map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64; 501 502 remaining -= map_size; 503 dss_size = map_size; 504 if (mpext) 505 opts->ext_copy = *mpext; 506 507 if (skb && snd_data_fin_enable) 508 mptcp_write_data_fin(subflow, skb, &opts->ext_copy); 509 ret = true; 510 } 511 512 /* passive sockets msk will set the 'can_ack' after accept(), even 513 * if the first subflow may have the already the remote key handy 514 */ 515 opts->ext_copy.use_ack = 0; 516 if (!READ_ONCE(msk->can_ack)) { 517 *size = ALIGN(dss_size, 4); 518 return ret; 519 } 520 521 if (READ_ONCE(msk->use_64bit_ack)) { 522 ack_size = TCPOLEN_MPTCP_DSS_ACK64; 523 opts->ext_copy.data_ack = READ_ONCE(msk->ack_seq); 524 opts->ext_copy.ack64 = 1; 525 } else { 526 ack_size = TCPOLEN_MPTCP_DSS_ACK32; 527 opts->ext_copy.data_ack32 = (uint32_t)READ_ONCE(msk->ack_seq); 528 opts->ext_copy.ack64 = 0; 529 } 530 opts->ext_copy.use_ack = 1; 531 532 /* Add kind/length/subtype/flag overhead if mapping is not populated */ 533 if (dss_size == 0) 534 ack_size += TCPOLEN_MPTCP_DSS_BASE; 535 536 dss_size += ack_size; 537 538 *size = ALIGN(dss_size, 4); 539 return true; 540 } 541 542 static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id, 543 struct in_addr *addr) 544 { 545 u8 hmac[SHA256_DIGEST_SIZE]; 546 u8 msg[7]; 547 548 msg[0] = addr_id; 549 memcpy(&msg[1], &addr->s_addr, 4); 550 msg[5] = 0; 551 msg[6] = 0; 552 553 mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac); 554 555 return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]); 556 } 557 558 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 559 static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id, 560 struct in6_addr *addr) 561 { 562 u8 hmac[SHA256_DIGEST_SIZE]; 563 u8 msg[19]; 564 565 msg[0] = addr_id; 566 memcpy(&msg[1], &addr->s6_addr, 16); 567 msg[17] = 0; 568 msg[18] = 0; 569 570 mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac); 571 572 return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]); 573 } 574 #endif 575 576 static bool mptcp_established_options_add_addr(struct sock *sk, 577 unsigned int *size, 578 unsigned int remaining, 579 struct mptcp_out_options *opts) 580 { 581 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 582 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 583 struct mptcp_addr_info saddr; 584 bool echo; 585 int len; 586 587 if (!mptcp_pm_should_add_signal(msk) || 588 !(mptcp_pm_add_addr_signal(msk, remaining, &saddr, &echo))) 589 return false; 590 591 len = mptcp_add_addr_len(saddr.family, echo); 592 if (remaining < len) 593 return false; 594 595 *size = len; 596 opts->addr_id = saddr.id; 597 if (saddr.family == AF_INET) { 598 opts->suboptions |= OPTION_MPTCP_ADD_ADDR; 599 opts->addr = saddr.addr; 600 if (!echo) { 601 opts->ahmac = add_addr_generate_hmac(msk->local_key, 602 msk->remote_key, 603 opts->addr_id, 604 &opts->addr); 605 } 606 } 607 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 608 else if (saddr.family == AF_INET6) { 609 opts->suboptions |= OPTION_MPTCP_ADD_ADDR6; 610 opts->addr6 = saddr.addr6; 611 if (!echo) { 612 opts->ahmac = add_addr6_generate_hmac(msk->local_key, 613 msk->remote_key, 614 opts->addr_id, 615 &opts->addr6); 616 } 617 } 618 #endif 619 pr_debug("addr_id=%d, ahmac=%llu, echo=%d", opts->addr_id, opts->ahmac, echo); 620 621 return true; 622 } 623 624 static bool mptcp_established_options_rm_addr(struct sock *sk, 625 unsigned int *size, 626 unsigned int remaining, 627 struct mptcp_out_options *opts) 628 { 629 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 630 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 631 u8 rm_id; 632 633 if (!mptcp_pm_should_rm_signal(msk) || 634 !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_id))) 635 return false; 636 637 if (remaining < TCPOLEN_MPTCP_RM_ADDR_BASE) 638 return false; 639 640 *size = TCPOLEN_MPTCP_RM_ADDR_BASE; 641 opts->suboptions |= OPTION_MPTCP_RM_ADDR; 642 opts->rm_id = rm_id; 643 644 pr_debug("rm_id=%d", opts->rm_id); 645 646 return true; 647 } 648 649 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb, 650 unsigned int *size, unsigned int remaining, 651 struct mptcp_out_options *opts) 652 { 653 unsigned int opt_size = 0; 654 bool ret = false; 655 656 opts->suboptions = 0; 657 658 if (unlikely(mptcp_check_fallback(sk))) 659 return false; 660 661 /* prevent adding of any MPTCP related options on reset packet 662 * until we support MP_TCPRST/MP_FASTCLOSE 663 */ 664 if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) 665 return false; 666 667 if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts)) 668 ret = true; 669 else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining, 670 opts)) 671 ret = true; 672 673 /* we reserved enough space for the above options, and exceeding the 674 * TCP option space would be fatal 675 */ 676 if (WARN_ON_ONCE(opt_size > remaining)) 677 return false; 678 679 *size += opt_size; 680 remaining -= opt_size; 681 if (mptcp_established_options_add_addr(sk, &opt_size, remaining, opts)) { 682 *size += opt_size; 683 remaining -= opt_size; 684 ret = true; 685 } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) { 686 *size += opt_size; 687 remaining -= opt_size; 688 ret = true; 689 } 690 691 return ret; 692 } 693 694 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size, 695 struct mptcp_out_options *opts) 696 { 697 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req); 698 699 if (subflow_req->mp_capable) { 700 opts->suboptions = OPTION_MPTCP_MPC_SYNACK; 701 opts->sndr_key = subflow_req->local_key; 702 *size = TCPOLEN_MPTCP_MPC_SYNACK; 703 pr_debug("subflow_req=%p, local_key=%llu", 704 subflow_req, subflow_req->local_key); 705 return true; 706 } else if (subflow_req->mp_join) { 707 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK; 708 opts->backup = subflow_req->backup; 709 opts->join_id = subflow_req->local_id; 710 opts->thmac = subflow_req->thmac; 711 opts->nonce = subflow_req->local_nonce; 712 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u", 713 subflow_req, opts->backup, opts->join_id, 714 opts->thmac, opts->nonce); 715 *size = TCPOLEN_MPTCP_MPJ_SYNACK; 716 return true; 717 } 718 return false; 719 } 720 721 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk, 722 struct mptcp_subflow_context *subflow, 723 struct sk_buff *skb, 724 struct mptcp_options_received *mp_opt) 725 { 726 /* here we can process OoO, in-window pkts, only in-sequence 4th ack 727 * will make the subflow fully established 728 */ 729 if (likely(subflow->fully_established)) { 730 /* on passive sockets, check for 3rd ack retransmission 731 * note that msk is always set by subflow_syn_recv_sock() 732 * for mp_join subflows 733 */ 734 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 && 735 TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq && 736 subflow->mp_join && mp_opt->mp_join && 737 READ_ONCE(msk->pm.server_side)) 738 tcp_send_ack(ssk); 739 goto fully_established; 740 } 741 742 /* we must process OoO packets before the first subflow is fully 743 * established. OoO packets are instead a protocol violation 744 * for MP_JOIN subflows as the peer must not send any data 745 * before receiving the forth ack - cfr. RFC 8684 section 3.2. 746 */ 747 if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) { 748 if (subflow->mp_join) 749 goto reset; 750 return subflow->mp_capable; 751 } 752 753 if (mp_opt->dss && mp_opt->use_ack) { 754 /* subflows are fully established as soon as we get any 755 * additional ack. 756 */ 757 subflow->fully_established = 1; 758 WRITE_ONCE(msk->fully_established, true); 759 goto fully_established; 760 } 761 762 /* If the first established packet does not contain MP_CAPABLE + data 763 * then fallback to TCP. Fallback scenarios requires a reset for 764 * MP_JOIN subflows. 765 */ 766 if (!mp_opt->mp_capable) { 767 if (subflow->mp_join) 768 goto reset; 769 subflow->mp_capable = 0; 770 pr_fallback(msk); 771 __mptcp_do_fallback(msk); 772 return false; 773 } 774 775 if (unlikely(!READ_ONCE(msk->pm.server_side))) 776 pr_warn_once("bogus mpc option on established client sk"); 777 mptcp_subflow_fully_established(subflow, mp_opt); 778 779 fully_established: 780 if (likely(subflow->pm_notified)) 781 return true; 782 783 subflow->pm_notified = 1; 784 if (subflow->mp_join) { 785 clear_3rdack_retransmission(ssk); 786 mptcp_pm_subflow_established(msk, subflow); 787 } else { 788 mptcp_pm_fully_established(msk); 789 } 790 return true; 791 792 reset: 793 mptcp_subflow_reset(ssk); 794 return false; 795 } 796 797 static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit) 798 { 799 u32 old_ack32, cur_ack32; 800 801 if (use_64bit) 802 return cur_ack; 803 804 old_ack32 = (u32)old_ack; 805 cur_ack32 = (u32)cur_ack; 806 cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32; 807 if (unlikely(before(cur_ack32, old_ack32))) 808 return cur_ack + (1LL << 32); 809 return cur_ack; 810 } 811 812 static void update_una(struct mptcp_sock *msk, 813 struct mptcp_options_received *mp_opt) 814 { 815 u64 new_snd_una, snd_una, old_snd_una = atomic64_read(&msk->snd_una); 816 u64 write_seq = READ_ONCE(msk->write_seq); 817 818 /* avoid ack expansion on update conflict, to reduce the risk of 819 * wrongly expanding to a future ack sequence number, which is way 820 * more dangerous than missing an ack 821 */ 822 new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64); 823 824 /* ACK for data not even sent yet? Ignore. */ 825 if (after64(new_snd_una, write_seq)) 826 new_snd_una = old_snd_una; 827 828 while (after64(new_snd_una, old_snd_una)) { 829 snd_una = old_snd_una; 830 old_snd_una = atomic64_cmpxchg(&msk->snd_una, snd_una, 831 new_snd_una); 832 if (old_snd_una == snd_una) { 833 mptcp_data_acked((struct sock *)msk); 834 break; 835 } 836 } 837 } 838 839 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit) 840 { 841 /* Skip if DATA_FIN was already received. 842 * If updating simultaneously with the recvmsg loop, values 843 * should match. If they mismatch, the peer is misbehaving and 844 * we will prefer the most recent information. 845 */ 846 if (READ_ONCE(msk->rcv_data_fin) || !READ_ONCE(msk->first)) 847 return false; 848 849 WRITE_ONCE(msk->rcv_data_fin_seq, 850 expand_ack(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit)); 851 WRITE_ONCE(msk->rcv_data_fin, 1); 852 853 return true; 854 } 855 856 static bool add_addr_hmac_valid(struct mptcp_sock *msk, 857 struct mptcp_options_received *mp_opt) 858 { 859 u64 hmac = 0; 860 861 if (mp_opt->echo) 862 return true; 863 864 if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) 865 hmac = add_addr_generate_hmac(msk->remote_key, 866 msk->local_key, 867 mp_opt->addr_id, &mp_opt->addr); 868 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 869 else 870 hmac = add_addr6_generate_hmac(msk->remote_key, 871 msk->local_key, 872 mp_opt->addr_id, &mp_opt->addr6); 873 #endif 874 875 pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n", 876 msk, (unsigned long long)hmac, 877 (unsigned long long)mp_opt->ahmac); 878 879 return hmac == mp_opt->ahmac; 880 } 881 882 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) 883 { 884 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 885 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 886 struct mptcp_options_received mp_opt; 887 struct mptcp_ext *mpext; 888 889 if (__mptcp_check_fallback(msk)) 890 return; 891 892 mptcp_get_options(skb, &mp_opt); 893 if (!check_fully_established(msk, sk, subflow, skb, &mp_opt)) 894 return; 895 896 if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) { 897 struct mptcp_addr_info addr; 898 899 addr.port = htons(mp_opt.port); 900 addr.id = mp_opt.addr_id; 901 if (mp_opt.family == MPTCP_ADDR_IPVERSION_4) { 902 addr.family = AF_INET; 903 addr.addr = mp_opt.addr; 904 } 905 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 906 else if (mp_opt.family == MPTCP_ADDR_IPVERSION_6) { 907 addr.family = AF_INET6; 908 addr.addr6 = mp_opt.addr6; 909 } 910 #endif 911 if (!mp_opt.echo) { 912 mptcp_pm_add_addr_received(msk, &addr); 913 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR); 914 } else { 915 mptcp_pm_del_add_timer(msk, &addr); 916 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD); 917 } 918 mp_opt.add_addr = 0; 919 } 920 921 if (mp_opt.rm_addr) { 922 mptcp_pm_rm_addr_received(msk, mp_opt.rm_id); 923 mp_opt.rm_addr = 0; 924 } 925 926 if (!mp_opt.dss) 927 return; 928 929 /* we can't wait for recvmsg() to update the ack_seq, otherwise 930 * monodirectional flows will stuck 931 */ 932 if (mp_opt.use_ack) 933 update_una(msk, &mp_opt); 934 935 /* Zero-data-length packets are dropped by the caller and not 936 * propagated to the MPTCP layer, so the skb extension does not 937 * need to be allocated or populated. DATA_FIN information, if 938 * present, needs to be updated here before the skb is freed. 939 */ 940 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) { 941 if (mp_opt.data_fin && mp_opt.data_len == 1 && 942 mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) && 943 schedule_work(&msk->work)) 944 sock_hold(subflow->conn); 945 946 return; 947 } 948 949 mpext = skb_ext_add(skb, SKB_EXT_MPTCP); 950 if (!mpext) 951 return; 952 953 memset(mpext, 0, sizeof(*mpext)); 954 955 if (mp_opt.use_map) { 956 if (mp_opt.mpc_map) { 957 /* this is an MP_CAPABLE carrying MPTCP data 958 * we know this map the first chunk of data 959 */ 960 mptcp_crypto_key_sha(subflow->remote_key, NULL, 961 &mpext->data_seq); 962 mpext->data_seq++; 963 mpext->subflow_seq = 1; 964 mpext->dsn64 = 1; 965 mpext->mpc_map = 1; 966 mpext->data_fin = 0; 967 } else { 968 mpext->data_seq = mp_opt.data_seq; 969 mpext->subflow_seq = mp_opt.subflow_seq; 970 mpext->dsn64 = mp_opt.dsn64; 971 mpext->data_fin = mp_opt.data_fin; 972 } 973 mpext->data_len = mp_opt.data_len; 974 mpext->use_map = 1; 975 } 976 } 977 978 void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts) 979 { 980 if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK | 981 OPTION_MPTCP_MPC_ACK) & opts->suboptions) { 982 u8 len; 983 984 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) 985 len = TCPOLEN_MPTCP_MPC_SYN; 986 else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) 987 len = TCPOLEN_MPTCP_MPC_SYNACK; 988 else if (opts->ext_copy.data_len) 989 len = TCPOLEN_MPTCP_MPC_ACK_DATA; 990 else 991 len = TCPOLEN_MPTCP_MPC_ACK; 992 993 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len, 994 MPTCP_SUPPORTED_VERSION, 995 MPTCP_CAP_HMAC_SHA256); 996 997 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) & 998 opts->suboptions)) 999 goto mp_capable_done; 1000 1001 put_unaligned_be64(opts->sndr_key, ptr); 1002 ptr += 2; 1003 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions)) 1004 goto mp_capable_done; 1005 1006 put_unaligned_be64(opts->rcvr_key, ptr); 1007 ptr += 2; 1008 if (!opts->ext_copy.data_len) 1009 goto mp_capable_done; 1010 1011 put_unaligned_be32(opts->ext_copy.data_len << 16 | 1012 TCPOPT_NOP << 8 | TCPOPT_NOP, ptr); 1013 ptr += 1; 1014 } 1015 1016 mp_capable_done: 1017 if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) { 1018 if (opts->ahmac) 1019 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR, 1020 TCPOLEN_MPTCP_ADD_ADDR, 0, 1021 opts->addr_id); 1022 else 1023 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR, 1024 TCPOLEN_MPTCP_ADD_ADDR_BASE, 1025 MPTCP_ADDR_ECHO, 1026 opts->addr_id); 1027 memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4); 1028 ptr += 1; 1029 if (opts->ahmac) { 1030 put_unaligned_be64(opts->ahmac, ptr); 1031 ptr += 2; 1032 } 1033 } 1034 1035 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 1036 if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) { 1037 if (opts->ahmac) 1038 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR, 1039 TCPOLEN_MPTCP_ADD_ADDR6, 0, 1040 opts->addr_id); 1041 else 1042 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR, 1043 TCPOLEN_MPTCP_ADD_ADDR6_BASE, 1044 MPTCP_ADDR_ECHO, 1045 opts->addr_id); 1046 memcpy((u8 *)ptr, opts->addr6.s6_addr, 16); 1047 ptr += 4; 1048 if (opts->ahmac) { 1049 put_unaligned_be64(opts->ahmac, ptr); 1050 ptr += 2; 1051 } 1052 } 1053 #endif 1054 1055 if (OPTION_MPTCP_RM_ADDR & opts->suboptions) { 1056 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR, 1057 TCPOLEN_MPTCP_RM_ADDR_BASE, 1058 0, opts->rm_id); 1059 } 1060 1061 if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) { 1062 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN, 1063 TCPOLEN_MPTCP_MPJ_SYN, 1064 opts->backup, opts->join_id); 1065 put_unaligned_be32(opts->token, ptr); 1066 ptr += 1; 1067 put_unaligned_be32(opts->nonce, ptr); 1068 ptr += 1; 1069 } 1070 1071 if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) { 1072 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN, 1073 TCPOLEN_MPTCP_MPJ_SYNACK, 1074 opts->backup, opts->join_id); 1075 put_unaligned_be64(opts->thmac, ptr); 1076 ptr += 2; 1077 put_unaligned_be32(opts->nonce, ptr); 1078 ptr += 1; 1079 } 1080 1081 if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) { 1082 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN, 1083 TCPOLEN_MPTCP_MPJ_ACK, 0, 0); 1084 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN); 1085 ptr += 5; 1086 } 1087 1088 if (opts->ext_copy.use_ack || opts->ext_copy.use_map) { 1089 struct mptcp_ext *mpext = &opts->ext_copy; 1090 u8 len = TCPOLEN_MPTCP_DSS_BASE; 1091 u8 flags = 0; 1092 1093 if (mpext->use_ack) { 1094 flags = MPTCP_DSS_HAS_ACK; 1095 if (mpext->ack64) { 1096 len += TCPOLEN_MPTCP_DSS_ACK64; 1097 flags |= MPTCP_DSS_ACK64; 1098 } else { 1099 len += TCPOLEN_MPTCP_DSS_ACK32; 1100 } 1101 } 1102 1103 if (mpext->use_map) { 1104 len += TCPOLEN_MPTCP_DSS_MAP64; 1105 1106 /* Use only 64-bit mapping flags for now, add 1107 * support for optional 32-bit mappings later. 1108 */ 1109 flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64; 1110 if (mpext->data_fin) 1111 flags |= MPTCP_DSS_DATA_FIN; 1112 } 1113 1114 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags); 1115 1116 if (mpext->use_ack) { 1117 if (mpext->ack64) { 1118 put_unaligned_be64(mpext->data_ack, ptr); 1119 ptr += 2; 1120 } else { 1121 put_unaligned_be32(mpext->data_ack32, ptr); 1122 ptr += 1; 1123 } 1124 } 1125 1126 if (mpext->use_map) { 1127 put_unaligned_be64(mpext->data_seq, ptr); 1128 ptr += 2; 1129 put_unaligned_be32(mpext->subflow_seq, ptr); 1130 ptr += 1; 1131 put_unaligned_be32(mpext->data_len << 16 | 1132 TCPOPT_NOP << 8 | TCPOPT_NOP, ptr); 1133 } 1134 } 1135 } 1136