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/sha2.h> 11 #include <net/tcp.h> 12 #include <net/mptcp.h> 13 #include "protocol.h" 14 #include "mib.h" 15 16 #include <trace/events/mptcp.h> 17 18 static bool mptcp_cap_flag_sha256(u8 flags) 19 { 20 return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256; 21 } 22 23 static void mptcp_parse_option(const struct sk_buff *skb, 24 const unsigned char *ptr, int opsize, 25 struct mptcp_options_received *mp_opt) 26 { 27 u8 subtype = *ptr >> 4; 28 int expected_opsize; 29 u16 subopt; 30 u8 version; 31 u8 flags; 32 u8 i; 33 34 switch (subtype) { 35 case MPTCPOPT_MP_CAPABLE: 36 /* strict size checking */ 37 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) { 38 if (skb->len > tcp_hdr(skb)->doff << 2) 39 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA; 40 else 41 expected_opsize = TCPOLEN_MPTCP_MPC_ACK; 42 subopt = OPTION_MPTCP_MPC_ACK; 43 } else { 44 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) { 45 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK; 46 subopt = OPTION_MPTCP_MPC_SYNACK; 47 } else { 48 expected_opsize = TCPOLEN_MPTCP_MPC_SYN; 49 subopt = OPTION_MPTCP_MPC_SYN; 50 } 51 } 52 53 /* Cfr RFC 8684 Section 3.3.0: 54 * If a checksum is present but its use had 55 * not been negotiated in the MP_CAPABLE handshake, the receiver MUST 56 * close the subflow with a RST, as it is not behaving as negotiated. 57 * If a checksum is not present when its use has been negotiated, the 58 * receiver MUST close the subflow with a RST, as it is considered 59 * broken 60 * We parse even option with mismatching csum presence, so that 61 * later in subflow_data_ready we can trigger the reset. 62 */ 63 if (opsize != expected_opsize && 64 (expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA || 65 opsize != TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM)) 66 break; 67 68 /* try to be gentle vs future versions on the initial syn */ 69 version = *ptr++ & MPTCP_VERSION_MASK; 70 if (opsize != TCPOLEN_MPTCP_MPC_SYN) { 71 if (version != MPTCP_SUPPORTED_VERSION) 72 break; 73 } else if (version < MPTCP_SUPPORTED_VERSION) { 74 break; 75 } 76 77 flags = *ptr++; 78 if (!mptcp_cap_flag_sha256(flags) || 79 (flags & MPTCP_CAP_EXTENSIBILITY)) 80 break; 81 82 /* RFC 6824, Section 3.1: 83 * "For the Checksum Required bit (labeled "A"), if either 84 * host requires the use of checksums, checksums MUST be used. 85 * In other words, the only way for checksums not to be used 86 * is if both hosts in their SYNs set A=0." 87 */ 88 if (flags & MPTCP_CAP_CHECKSUM_REQD) 89 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD; 90 91 mp_opt->deny_join_id0 = !!(flags & MPTCP_CAP_DENY_JOIN_ID0); 92 93 mp_opt->suboptions |= subopt; 94 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) { 95 mp_opt->sndr_key = get_unaligned_be64(ptr); 96 ptr += 8; 97 } 98 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) { 99 mp_opt->rcvr_key = get_unaligned_be64(ptr); 100 ptr += 8; 101 } 102 if (opsize >= TCPOLEN_MPTCP_MPC_ACK_DATA) { 103 /* Section 3.1.: 104 * "the data parameters in a MP_CAPABLE are semantically 105 * equivalent to those in a DSS option and can be used 106 * interchangeably." 107 */ 108 mp_opt->suboptions |= OPTION_MPTCP_DSS; 109 mp_opt->use_map = 1; 110 mp_opt->mpc_map = 1; 111 mp_opt->data_len = get_unaligned_be16(ptr); 112 ptr += 2; 113 } 114 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) { 115 mp_opt->csum = get_unaligned((__force __sum16 *)ptr); 116 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD; 117 ptr += 2; 118 } 119 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u\n", 120 version, flags, opsize, mp_opt->sndr_key, 121 mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum); 122 break; 123 124 case MPTCPOPT_MP_JOIN: 125 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) { 126 mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYN; 127 mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP; 128 mp_opt->join_id = *ptr++; 129 mp_opt->token = get_unaligned_be32(ptr); 130 ptr += 4; 131 mp_opt->nonce = get_unaligned_be32(ptr); 132 ptr += 4; 133 pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u\n", 134 mp_opt->backup, mp_opt->join_id, 135 mp_opt->token, mp_opt->nonce); 136 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) { 137 mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYNACK; 138 mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP; 139 mp_opt->join_id = *ptr++; 140 mp_opt->thmac = get_unaligned_be64(ptr); 141 ptr += 8; 142 mp_opt->nonce = get_unaligned_be32(ptr); 143 ptr += 4; 144 pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u\n", 145 mp_opt->backup, mp_opt->join_id, 146 mp_opt->thmac, mp_opt->nonce); 147 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) { 148 mp_opt->suboptions |= OPTION_MPTCP_MPJ_ACK; 149 ptr += 2; 150 memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN); 151 pr_debug("MP_JOIN hmac\n"); 152 } 153 break; 154 155 case MPTCPOPT_DSS: 156 pr_debug("DSS\n"); 157 ptr++; 158 159 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK; 160 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0; 161 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0; 162 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0; 163 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0; 164 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK); 165 166 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d\n", 167 mp_opt->data_fin, mp_opt->dsn64, 168 mp_opt->use_map, mp_opt->ack64, 169 mp_opt->use_ack); 170 171 expected_opsize = TCPOLEN_MPTCP_DSS_BASE; 172 173 if (mp_opt->use_ack) { 174 if (mp_opt->ack64) 175 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64; 176 else 177 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32; 178 } 179 180 if (mp_opt->use_map) { 181 if (mp_opt->dsn64) 182 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64; 183 else 184 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32; 185 } 186 187 /* Always parse any csum presence combination, we will enforce 188 * RFC 8684 Section 3.3.0 checks later in subflow_data_ready 189 */ 190 if (opsize != expected_opsize && 191 opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) 192 break; 193 194 mp_opt->suboptions |= OPTION_MPTCP_DSS; 195 if (mp_opt->use_ack) { 196 if (mp_opt->ack64) { 197 mp_opt->data_ack = get_unaligned_be64(ptr); 198 ptr += 8; 199 } else { 200 mp_opt->data_ack = get_unaligned_be32(ptr); 201 ptr += 4; 202 } 203 204 pr_debug("data_ack=%llu\n", mp_opt->data_ack); 205 } 206 207 if (mp_opt->use_map) { 208 if (mp_opt->dsn64) { 209 mp_opt->data_seq = get_unaligned_be64(ptr); 210 ptr += 8; 211 } else { 212 mp_opt->data_seq = get_unaligned_be32(ptr); 213 ptr += 4; 214 } 215 216 mp_opt->subflow_seq = get_unaligned_be32(ptr); 217 ptr += 4; 218 219 mp_opt->data_len = get_unaligned_be16(ptr); 220 ptr += 2; 221 222 if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) { 223 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD; 224 mp_opt->csum = get_unaligned((__force __sum16 *)ptr); 225 ptr += 2; 226 } 227 228 pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u\n", 229 mp_opt->data_seq, mp_opt->subflow_seq, 230 mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD), 231 mp_opt->csum); 232 } 233 234 break; 235 236 case MPTCPOPT_ADD_ADDR: 237 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO; 238 if (!mp_opt->echo) { 239 if (opsize == TCPOLEN_MPTCP_ADD_ADDR || 240 opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT) 241 mp_opt->addr.family = AF_INET; 242 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 243 else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 || 244 opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT) 245 mp_opt->addr.family = AF_INET6; 246 #endif 247 else 248 break; 249 } else { 250 if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE || 251 opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) 252 mp_opt->addr.family = AF_INET; 253 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 254 else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE || 255 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) 256 mp_opt->addr.family = AF_INET6; 257 #endif 258 else 259 break; 260 } 261 262 mp_opt->suboptions |= OPTION_MPTCP_ADD_ADDR; 263 mp_opt->addr.id = *ptr++; 264 mp_opt->addr.port = 0; 265 mp_opt->ahmac = 0; 266 if (mp_opt->addr.family == AF_INET) { 267 memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4); 268 ptr += 4; 269 if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT || 270 opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) { 271 mp_opt->addr.port = htons(get_unaligned_be16(ptr)); 272 ptr += 2; 273 } 274 } 275 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 276 else { 277 memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16); 278 ptr += 16; 279 if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT || 280 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) { 281 mp_opt->addr.port = htons(get_unaligned_be16(ptr)); 282 ptr += 2; 283 } 284 } 285 #endif 286 if (!mp_opt->echo) { 287 mp_opt->ahmac = get_unaligned_be64(ptr); 288 ptr += 8; 289 } 290 pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d\n", 291 (mp_opt->addr.family == AF_INET6) ? "6" : "", 292 mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port)); 293 break; 294 295 case MPTCPOPT_RM_ADDR: 296 if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 || 297 opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX) 298 break; 299 300 ptr++; 301 302 mp_opt->suboptions |= OPTION_MPTCP_RM_ADDR; 303 mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE; 304 for (i = 0; i < mp_opt->rm_list.nr; i++) 305 mp_opt->rm_list.ids[i] = *ptr++; 306 pr_debug("RM_ADDR: rm_list_nr=%d\n", mp_opt->rm_list.nr); 307 break; 308 309 case MPTCPOPT_MP_PRIO: 310 if (opsize != TCPOLEN_MPTCP_PRIO) 311 break; 312 313 mp_opt->suboptions |= OPTION_MPTCP_PRIO; 314 mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP; 315 pr_debug("MP_PRIO: prio=%d\n", mp_opt->backup); 316 break; 317 318 case MPTCPOPT_MP_FASTCLOSE: 319 if (opsize != TCPOLEN_MPTCP_FASTCLOSE) 320 break; 321 322 ptr += 2; 323 mp_opt->rcvr_key = get_unaligned_be64(ptr); 324 ptr += 8; 325 mp_opt->suboptions |= OPTION_MPTCP_FASTCLOSE; 326 pr_debug("MP_FASTCLOSE: recv_key=%llu\n", mp_opt->rcvr_key); 327 break; 328 329 case MPTCPOPT_RST: 330 if (opsize != TCPOLEN_MPTCP_RST) 331 break; 332 333 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) 334 break; 335 336 mp_opt->suboptions |= OPTION_MPTCP_RST; 337 flags = *ptr++; 338 mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT; 339 mp_opt->reset_reason = *ptr; 340 pr_debug("MP_RST: transient=%u reason=%u\n", 341 mp_opt->reset_transient, mp_opt->reset_reason); 342 break; 343 344 case MPTCPOPT_MP_FAIL: 345 if (opsize != TCPOLEN_MPTCP_FAIL) 346 break; 347 348 ptr += 2; 349 mp_opt->suboptions |= OPTION_MPTCP_FAIL; 350 mp_opt->fail_seq = get_unaligned_be64(ptr); 351 pr_debug("MP_FAIL: data_seq=%llu\n", mp_opt->fail_seq); 352 break; 353 354 default: 355 break; 356 } 357 } 358 359 void mptcp_get_options(const struct sk_buff *skb, 360 struct mptcp_options_received *mp_opt) 361 { 362 const struct tcphdr *th = tcp_hdr(skb); 363 const unsigned char *ptr; 364 int length; 365 366 /* Ensure that casting the whole status to u32 is efficient and safe */ 367 BUILD_BUG_ON(sizeof_field(struct mptcp_options_received, status) != sizeof(u32)); 368 BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct mptcp_options_received, status), 369 sizeof(u32))); 370 *(u32 *)&mp_opt->status = 0; 371 372 length = (th->doff * 4) - sizeof(struct tcphdr); 373 ptr = (const unsigned char *)(th + 1); 374 375 while (length > 0) { 376 int opcode = *ptr++; 377 int opsize; 378 379 switch (opcode) { 380 case TCPOPT_EOL: 381 return; 382 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ 383 length--; 384 continue; 385 default: 386 if (length < 2) 387 return; 388 opsize = *ptr++; 389 if (opsize < 2) /* "silly options" */ 390 return; 391 if (opsize > length) 392 return; /* don't parse partial options */ 393 if (opcode == TCPOPT_MPTCP) 394 mptcp_parse_option(skb, ptr, opsize, mp_opt); 395 ptr += opsize - 2; 396 length -= opsize; 397 } 398 } 399 } 400 401 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb, 402 unsigned int *size, struct mptcp_out_options *opts) 403 { 404 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 405 406 /* we will use snd_isn to detect first pkt [re]transmission 407 * in mptcp_established_options_mp() 408 */ 409 subflow->snd_isn = TCP_SKB_CB(skb)->end_seq; 410 if (subflow->request_mptcp) { 411 if (unlikely(subflow_simultaneous_connect(sk))) { 412 WARN_ON_ONCE(!mptcp_try_fallback(sk, MPTCP_MIB_SIMULTCONNFALLBACK)); 413 414 /* Ensure mptcp_finish_connect() will not process the 415 * MPC handshake. 416 */ 417 subflow->request_mptcp = 0; 418 return false; 419 } 420 421 opts->suboptions = OPTION_MPTCP_MPC_SYN; 422 opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk)); 423 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk)); 424 *size = TCPOLEN_MPTCP_MPC_SYN; 425 return true; 426 } else if (subflow->request_join) { 427 pr_debug("remote_token=%u, nonce=%u\n", subflow->remote_token, 428 subflow->local_nonce); 429 opts->suboptions = OPTION_MPTCP_MPJ_SYN; 430 opts->join_id = subflow->local_id; 431 opts->token = subflow->remote_token; 432 opts->nonce = subflow->local_nonce; 433 opts->backup = subflow->request_bkup; 434 *size = TCPOLEN_MPTCP_MPJ_SYN; 435 return true; 436 } 437 return false; 438 } 439 440 static void clear_3rdack_retransmission(struct sock *sk) 441 { 442 struct inet_connection_sock *icsk = inet_csk(sk); 443 444 sk_stop_timer(sk, &icsk->icsk_delack_timer); 445 icsk->icsk_ack.ato = 0; 446 icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER); 447 } 448 449 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb, 450 bool snd_data_fin_enable, 451 unsigned int *size, 452 struct mptcp_out_options *opts) 453 { 454 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 455 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 456 struct mptcp_ext *mpext; 457 unsigned int data_len; 458 u8 len; 459 460 /* When skb is not available, we better over-estimate the emitted 461 * options len. A full DSS option (28 bytes) is longer than 462 * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so 463 * tell the caller to defer the estimate to 464 * mptcp_established_options_dss(), which will reserve enough space. 465 */ 466 if (!skb) 467 return false; 468 469 /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */ 470 if (READ_ONCE(subflow->fully_established) || snd_data_fin_enable || 471 subflow->snd_isn != TCP_SKB_CB(skb)->seq || 472 sk->sk_state != TCP_ESTABLISHED) 473 return false; 474 475 if (subflow->mp_capable) { 476 mpext = mptcp_get_ext(skb); 477 data_len = mpext ? mpext->data_len : 0; 478 479 /* we will check ops->data_len in mptcp_write_options() to 480 * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and 481 * TCPOLEN_MPTCP_MPC_ACK 482 */ 483 opts->data_len = data_len; 484 opts->suboptions = OPTION_MPTCP_MPC_ACK; 485 opts->sndr_key = subflow->local_key; 486 opts->rcvr_key = subflow->remote_key; 487 opts->csum_reqd = READ_ONCE(msk->csum_enabled); 488 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk)); 489 490 /* Section 3.1. 491 * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK 492 * packets that start the first subflow of an MPTCP connection, 493 * as well as the first packet that carries data 494 */ 495 if (data_len > 0) { 496 len = TCPOLEN_MPTCP_MPC_ACK_DATA; 497 if (opts->csum_reqd) { 498 /* we need to propagate more info to csum the pseudo hdr */ 499 opts->data_seq = mpext->data_seq; 500 opts->subflow_seq = mpext->subflow_seq; 501 opts->csum = mpext->csum; 502 len += TCPOLEN_MPTCP_DSS_CHECKSUM; 503 } 504 *size = ALIGN(len, 4); 505 } else { 506 *size = TCPOLEN_MPTCP_MPC_ACK; 507 } 508 509 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d\n", 510 subflow, subflow->local_key, subflow->remote_key, 511 data_len); 512 513 return true; 514 } else if (subflow->mp_join) { 515 opts->suboptions = OPTION_MPTCP_MPJ_ACK; 516 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN); 517 *size = TCPOLEN_MPTCP_MPJ_ACK; 518 pr_debug("subflow=%p\n", subflow); 519 520 /* we can use the full delegate action helper only from BH context 521 * If we are in process context - sk is flushing the backlog at 522 * socket lock release time - just set the appropriate flag, will 523 * be handled by the release callback 524 */ 525 if (sock_owned_by_user(sk)) 526 set_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status); 527 else 528 mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_ACK); 529 return true; 530 } 531 return false; 532 } 533 534 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow, 535 struct sk_buff *skb, struct mptcp_ext *ext) 536 { 537 /* The write_seq value has already been incremented, so the actual 538 * sequence number for the DATA_FIN is one less. 539 */ 540 u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1; 541 542 if (!ext->use_map || !skb->len) { 543 /* RFC6824 requires a DSS mapping with specific values 544 * if DATA_FIN is set but no data payload is mapped 545 */ 546 ext->data_fin = 1; 547 ext->use_map = 1; 548 ext->dsn64 = 1; 549 ext->data_seq = data_fin_tx_seq; 550 ext->subflow_seq = 0; 551 ext->data_len = 1; 552 } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) { 553 /* If there's an existing DSS mapping and it is the 554 * final mapping, DATA_FIN consumes 1 additional byte of 555 * mapping space. 556 */ 557 ext->data_fin = 1; 558 ext->data_len++; 559 } 560 } 561 562 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb, 563 bool snd_data_fin_enable, 564 unsigned int *size, 565 struct mptcp_out_options *opts) 566 { 567 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 568 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 569 struct tcp_sock *tp = tcp_sk(sk); 570 unsigned int dss_size = 0; 571 struct mptcp_ext *mpext; 572 unsigned int ack_size; 573 bool ret = false; 574 575 /* Zero `use_ack` and `use_map` flags with one shot. */ 576 BUILD_BUG_ON(sizeof_field(struct mptcp_ext, flags) != sizeof(u16)); 577 BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct mptcp_ext, flags), 578 sizeof(u16))); 579 *(u16 *)&opts->ext_copy.flags = 0; 580 opts->csum_reqd = READ_ONCE(msk->csum_enabled); 581 mpext = skb ? mptcp_get_ext(skb) : NULL; 582 583 if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) { 584 unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64; 585 586 if (mpext) { 587 if (opts->csum_reqd) 588 map_size += TCPOLEN_MPTCP_DSS_CHECKSUM; 589 590 opts->ext_copy = *mpext; 591 } 592 593 dss_size = map_size; 594 if (skb && snd_data_fin_enable) 595 mptcp_write_data_fin(subflow, skb, &opts->ext_copy); 596 opts->suboptions = OPTION_MPTCP_DSS; 597 ret = true; 598 } 599 600 /* passive sockets msk will set the 'can_ack' after accept(), even 601 * if the first subflow may have the already the remote key handy 602 */ 603 if (!READ_ONCE(msk->can_ack)) { 604 *size = ALIGN(dss_size, 4); 605 return ret; 606 } 607 608 if (READ_ONCE(msk->use_64bit_ack)) { 609 ack_size = TCPOLEN_MPTCP_DSS_ACK64; 610 opts->ext_copy.ack64 = 1; 611 } else { 612 ack_size = TCPOLEN_MPTCP_DSS_ACK32; 613 opts->ext_copy.ack64 = 0; 614 } 615 opts->ext_copy.use_ack = 1; 616 opts->suboptions = OPTION_MPTCP_DSS; 617 618 /* Add kind/length/subtype/flag overhead if mapping is not populated */ 619 if (dss_size == 0) 620 ack_size += TCPOLEN_MPTCP_DSS_BASE; 621 622 /* The caller is __tcp_transmit_skb(), and will compute the new rcv 623 * wnd soon: ensure that the window can shrink. 624 */ 625 if (skb) 626 tp->rcv_wnd = tp->rcv_nxt - tp->rcv_wup; 627 628 dss_size += ack_size; 629 630 *size = ALIGN(dss_size, 4); 631 return true; 632 } 633 634 static u64 add_addr_generate_hmac(u64 key1, u64 key2, 635 struct mptcp_addr_info *addr) 636 { 637 u16 port = ntohs(addr->port); 638 u8 hmac[SHA256_DIGEST_SIZE]; 639 u8 msg[19]; 640 int i = 0; 641 642 msg[i++] = addr->id; 643 if (addr->family == AF_INET) { 644 memcpy(&msg[i], &addr->addr.s_addr, 4); 645 i += 4; 646 } 647 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 648 else if (addr->family == AF_INET6) { 649 memcpy(&msg[i], &addr->addr6.s6_addr, 16); 650 i += 16; 651 } 652 #endif 653 msg[i++] = port >> 8; 654 msg[i++] = port & 0xFF; 655 656 mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac); 657 658 return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]); 659 } 660 661 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb, 662 unsigned int *size, 663 unsigned int remaining, 664 struct mptcp_out_options *opts) 665 { 666 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 667 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 668 unsigned int opt_size = *size; 669 struct mptcp_addr_info addr; 670 bool echo; 671 int len; 672 673 /* add addr will strip the existing options, be sure to avoid breaking 674 * MPC/MPJ handshakes 675 */ 676 if (!mptcp_pm_should_add_signal(msk) || 677 (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) || 678 !skb || !skb_is_tcp_pure_ack(skb) || 679 !mptcp_pm_add_addr_signal(msk, opt_size, remaining, &addr, &echo)) 680 return false; 681 682 remaining += opt_size; 683 684 len = mptcp_add_addr_len(addr.family, echo, !!addr.port); 685 if (remaining < len) 686 return false; 687 688 *size = len; 689 pr_debug("drop other suboptions\n"); 690 opts->suboptions = 0; 691 *size -= opt_size; 692 opts->addr = addr; 693 opts->suboptions |= OPTION_MPTCP_ADD_ADDR; 694 if (!echo) { 695 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX); 696 opts->ahmac = add_addr_generate_hmac(READ_ONCE(msk->local_key), 697 READ_ONCE(msk->remote_key), 698 &opts->addr); 699 } else { 700 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADDTX); 701 opts->ahmac = 0; 702 } 703 pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d\n", 704 opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port)); 705 706 return true; 707 } 708 709 static bool mptcp_established_options_rm_addr(struct sock *sk, 710 unsigned int *size, 711 unsigned int remaining, 712 struct mptcp_out_options *opts) 713 { 714 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 715 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 716 struct mptcp_rm_list rm_list; 717 int i, len; 718 719 if (!mptcp_pm_should_rm_signal(msk) || 720 !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list))) 721 return false; 722 723 len = mptcp_rm_addr_len(&rm_list); 724 if (len < 0) 725 return false; 726 if (remaining < len) 727 return false; 728 729 *size = len; 730 opts->suboptions |= OPTION_MPTCP_RM_ADDR; 731 opts->rm_list = rm_list; 732 733 for (i = 0; i < opts->rm_list.nr; i++) 734 pr_debug("rm_list_ids[%d]=%d\n", i, opts->rm_list.ids[i]); 735 MPTCP_ADD_STATS(sock_net(sk), MPTCP_MIB_RMADDRTX, opts->rm_list.nr); 736 return true; 737 } 738 739 static bool mptcp_established_options_mp_prio(struct sock *sk, 740 unsigned int *size, 741 unsigned int remaining, 742 struct mptcp_out_options *opts) 743 { 744 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 745 746 /* can't send MP_PRIO with MPC, as they share the same option space: 747 * 'backup'. Also it makes no sense at all 748 */ 749 if (!subflow->send_mp_prio || (opts->suboptions & OPTIONS_MPTCP_MPC)) 750 return false; 751 752 /* account for the trailing 'nop' option */ 753 if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN) 754 return false; 755 756 *size = TCPOLEN_MPTCP_PRIO_ALIGN; 757 opts->suboptions |= OPTION_MPTCP_PRIO; 758 opts->backup = subflow->request_bkup; 759 760 pr_debug("prio=%d\n", opts->backup); 761 762 return true; 763 } 764 765 static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb, 766 unsigned int *size, 767 unsigned int remaining, 768 struct mptcp_out_options *opts) 769 { 770 const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 771 772 if (remaining < TCPOLEN_MPTCP_RST) 773 return false; 774 775 *size = TCPOLEN_MPTCP_RST; 776 opts->suboptions |= OPTION_MPTCP_RST; 777 opts->reset_transient = subflow->reset_transient; 778 opts->reset_reason = subflow->reset_reason; 779 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTTX); 780 781 return true; 782 } 783 784 static bool mptcp_established_options_fastclose(struct sock *sk, 785 unsigned int *size, 786 unsigned int remaining, 787 struct mptcp_out_options *opts) 788 { 789 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 790 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 791 792 if (likely(!subflow->send_fastclose)) 793 return false; 794 795 if (remaining < TCPOLEN_MPTCP_FASTCLOSE) 796 return false; 797 798 *size = TCPOLEN_MPTCP_FASTCLOSE; 799 opts->suboptions |= OPTION_MPTCP_FASTCLOSE; 800 opts->rcvr_key = READ_ONCE(msk->remote_key); 801 802 pr_debug("FASTCLOSE key=%llu\n", opts->rcvr_key); 803 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSETX); 804 return true; 805 } 806 807 static bool mptcp_established_options_mp_fail(struct sock *sk, 808 unsigned int *size, 809 unsigned int remaining, 810 struct mptcp_out_options *opts) 811 { 812 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 813 814 if (likely(!subflow->send_mp_fail)) 815 return false; 816 817 if (remaining < TCPOLEN_MPTCP_FAIL) 818 return false; 819 820 *size = TCPOLEN_MPTCP_FAIL; 821 opts->suboptions |= OPTION_MPTCP_FAIL; 822 opts->fail_seq = subflow->map_seq; 823 824 pr_debug("MP_FAIL fail_seq=%llu\n", opts->fail_seq); 825 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILTX); 826 827 return true; 828 } 829 830 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb, 831 unsigned int *size, unsigned int remaining, 832 struct mptcp_out_options *opts) 833 { 834 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 835 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 836 unsigned int opt_size = 0; 837 bool snd_data_fin; 838 bool ret = false; 839 840 opts->suboptions = 0; 841 842 /* Force later mptcp_write_options(), but do not use any actual 843 * option space. 844 */ 845 if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb))) 846 return true; 847 848 if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) { 849 if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) || 850 mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) { 851 *size += opt_size; 852 remaining -= opt_size; 853 } 854 /* MP_RST can be used with MP_FASTCLOSE and MP_FAIL if there is room */ 855 if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) { 856 *size += opt_size; 857 remaining -= opt_size; 858 } 859 return true; 860 } 861 862 snd_data_fin = mptcp_data_fin_enabled(msk); 863 if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, opts)) 864 ret = true; 865 else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, opts)) { 866 unsigned int mp_fail_size; 867 868 ret = true; 869 if (mptcp_established_options_mp_fail(sk, &mp_fail_size, 870 remaining - opt_size, opts)) { 871 *size += opt_size + mp_fail_size; 872 remaining -= opt_size - mp_fail_size; 873 return true; 874 } 875 } 876 877 /* we reserved enough space for the above options, and exceeding the 878 * TCP option space would be fatal 879 */ 880 if (WARN_ON_ONCE(opt_size > remaining)) 881 return false; 882 883 *size += opt_size; 884 remaining -= opt_size; 885 if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) { 886 *size += opt_size; 887 remaining -= opt_size; 888 ret = true; 889 } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) { 890 *size += opt_size; 891 remaining -= opt_size; 892 ret = true; 893 } 894 895 if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) { 896 *size += opt_size; 897 remaining -= opt_size; 898 ret = true; 899 } 900 901 return ret; 902 } 903 904 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size, 905 struct mptcp_out_options *opts) 906 { 907 struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req); 908 909 if (subflow_req->mp_capable) { 910 opts->suboptions = OPTION_MPTCP_MPC_SYNACK; 911 opts->sndr_key = subflow_req->local_key; 912 opts->csum_reqd = subflow_req->csum_reqd; 913 opts->allow_join_id0 = subflow_req->allow_join_id0; 914 *size = TCPOLEN_MPTCP_MPC_SYNACK; 915 pr_debug("subflow_req=%p, local_key=%llu\n", 916 subflow_req, subflow_req->local_key); 917 return true; 918 } else if (subflow_req->mp_join) { 919 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK; 920 opts->backup = subflow_req->request_bkup; 921 opts->join_id = subflow_req->local_id; 922 opts->thmac = subflow_req->thmac; 923 opts->nonce = subflow_req->local_nonce; 924 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u\n", 925 subflow_req, opts->backup, opts->join_id, 926 opts->thmac, opts->nonce); 927 *size = TCPOLEN_MPTCP_MPJ_SYNACK; 928 return true; 929 } 930 return false; 931 } 932 933 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk, 934 struct mptcp_subflow_context *subflow, 935 struct sk_buff *skb, 936 struct mptcp_options_received *mp_opt) 937 { 938 /* here we can process OoO, in-window pkts, only in-sequence 4th ack 939 * will make the subflow fully established 940 */ 941 if (likely(READ_ONCE(subflow->fully_established))) { 942 /* on passive sockets, check for 3rd ack retransmission 943 * note that msk is always set by subflow_syn_recv_sock() 944 * for mp_join subflows 945 */ 946 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 && 947 TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq && 948 subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) && 949 !subflow->request_join) 950 tcp_send_ack(ssk); 951 goto check_notify; 952 } 953 954 /* we must process OoO packets before the first subflow is fully 955 * established. OoO packets are instead a protocol violation 956 * for MP_JOIN subflows as the peer must not send any data 957 * before receiving the forth ack - cfr. RFC 8684 section 3.2. 958 */ 959 if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) { 960 if (subflow->mp_join) 961 goto reset; 962 if (subflow->is_mptfo && mp_opt->suboptions & OPTION_MPTCP_MPC_ACK) 963 goto set_fully_established; 964 return subflow->mp_capable; 965 } 966 967 if (subflow->remote_key_valid && 968 (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) || 969 ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) && 970 (!mp_opt->echo || subflow->mp_join)))) { 971 /* subflows are fully established as soon as we get any 972 * additional ack, including ADD_ADDR. 973 */ 974 goto set_fully_established; 975 } 976 977 /* If the first established packet does not contain MP_CAPABLE + data 978 * then fallback to TCP. Fallback scenarios requires a reset for 979 * MP_JOIN subflows. 980 */ 981 if (!(mp_opt->suboptions & OPTIONS_MPTCP_MPC)) { 982 if (subflow->mp_join) 983 goto reset; 984 subflow->mp_capable = 0; 985 if (!mptcp_try_fallback(ssk, MPTCP_MIB_MPCAPABLEDATAFALLBACK)) { 986 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_FALLBACKFAILED); 987 goto reset; 988 } 989 return false; 990 } 991 992 if (unlikely(!READ_ONCE(msk->pm.server_side))) 993 pr_warn_once("bogus mpc option on established client sk"); 994 995 set_fully_established: 996 if (mp_opt->deny_join_id0) 997 WRITE_ONCE(msk->pm.remote_deny_join_id0, true); 998 999 mptcp_data_lock((struct sock *)msk); 1000 __mptcp_subflow_fully_established(msk, subflow, mp_opt); 1001 mptcp_data_unlock((struct sock *)msk); 1002 1003 check_notify: 1004 /* if the subflow is not already linked into the conn_list, we can't 1005 * notify the PM: this subflow is still on the listener queue 1006 * and the PM possibly acquiring the subflow lock could race with 1007 * the listener close 1008 */ 1009 if (likely(subflow->pm_notified) || list_empty(&subflow->node)) 1010 return true; 1011 1012 subflow->pm_notified = 1; 1013 if (subflow->mp_join) { 1014 clear_3rdack_retransmission(ssk); 1015 mptcp_pm_subflow_established(msk); 1016 } else { 1017 mptcp_pm_fully_established(msk, ssk); 1018 } 1019 return true; 1020 1021 reset: 1022 mptcp_subflow_reset(ssk); 1023 return false; 1024 } 1025 1026 u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq) 1027 { 1028 u32 old_seq32, cur_seq32; 1029 1030 old_seq32 = (u32)old_seq; 1031 cur_seq32 = (u32)cur_seq; 1032 cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32; 1033 if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32))) 1034 return cur_seq + (1LL << 32); 1035 1036 /* reverse wrap could happen, too */ 1037 if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32))) 1038 return cur_seq - (1LL << 32); 1039 return cur_seq; 1040 } 1041 1042 static void __mptcp_snd_una_update(struct mptcp_sock *msk, u64 new_snd_una) 1043 { 1044 msk->bytes_acked += new_snd_una - msk->snd_una; 1045 WRITE_ONCE(msk->snd_una, new_snd_una); 1046 } 1047 1048 static void rwin_update(struct mptcp_sock *msk, struct sock *ssk, 1049 struct sk_buff *skb) 1050 { 1051 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk); 1052 struct tcp_sock *tp = tcp_sk(ssk); 1053 u64 mptcp_rcv_wnd; 1054 1055 /* Avoid touching extra cachelines if TCP is going to accept this 1056 * skb without filling the TCP-level window even with a possibly 1057 * outdated mptcp-level rwin. 1058 */ 1059 if (!skb->len || skb->len < tcp_receive_window(tp)) 1060 return; 1061 1062 mptcp_rcv_wnd = atomic64_read(&msk->rcv_wnd_sent); 1063 if (!after64(mptcp_rcv_wnd, subflow->rcv_wnd_sent)) 1064 return; 1065 1066 /* Some other subflow grew the mptcp-level rwin since rcv_wup, 1067 * resync. 1068 */ 1069 tp->rcv_wnd += mptcp_rcv_wnd - subflow->rcv_wnd_sent; 1070 tcp_update_max_rcv_wnd_seq(tp); 1071 subflow->rcv_wnd_sent = mptcp_rcv_wnd; 1072 } 1073 1074 static void ack_update_msk(struct mptcp_sock *msk, 1075 struct sock *ssk, 1076 struct mptcp_options_received *mp_opt) 1077 { 1078 u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt); 1079 struct sock *sk = (struct sock *)msk; 1080 u64 old_snd_una; 1081 1082 mptcp_data_lock(sk); 1083 1084 /* avoid ack expansion on update conflict, to reduce the risk of 1085 * wrongly expanding to a future ack sequence number, which is way 1086 * more dangerous than missing an ack 1087 */ 1088 old_snd_una = msk->snd_una; 1089 new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64); 1090 1091 /* ACK for data not even sent yet? Ignore.*/ 1092 if (unlikely(after64(new_snd_una, snd_nxt))) 1093 new_snd_una = old_snd_una; 1094 1095 new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd; 1096 1097 if (after64(new_wnd_end, msk->wnd_end)) 1098 WRITE_ONCE(msk->wnd_end, new_wnd_end); 1099 1100 /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */ 1101 if (after64(msk->wnd_end, snd_nxt)) 1102 __mptcp_check_push(sk, ssk); 1103 1104 if (after64(new_snd_una, old_snd_una)) { 1105 __mptcp_snd_una_update(msk, new_snd_una); 1106 __mptcp_data_acked(sk); 1107 } 1108 msk->last_ack_recv = tcp_jiffies32; 1109 mptcp_data_unlock(sk); 1110 1111 trace_ack_update_msk(mp_opt->data_ack, 1112 old_snd_una, new_snd_una, 1113 new_wnd_end, READ_ONCE(msk->wnd_end)); 1114 } 1115 1116 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit) 1117 { 1118 /* Skip if DATA_FIN was already received. 1119 * If updating simultaneously with the recvmsg loop, values 1120 * should match. If they mismatch, the peer is misbehaving and 1121 * we will prefer the most recent information. 1122 */ 1123 if (READ_ONCE(msk->rcv_data_fin)) 1124 return false; 1125 1126 WRITE_ONCE(msk->rcv_data_fin_seq, 1127 mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit)); 1128 WRITE_ONCE(msk->rcv_data_fin, 1); 1129 1130 return true; 1131 } 1132 1133 static bool add_addr_hmac_valid(struct mptcp_sock *msk, 1134 struct mptcp_options_received *mp_opt) 1135 { 1136 u64 hmac = 0; 1137 1138 if (mp_opt->echo) 1139 return true; 1140 1141 hmac = add_addr_generate_hmac(READ_ONCE(msk->remote_key), 1142 READ_ONCE(msk->local_key), 1143 &mp_opt->addr); 1144 1145 pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n", 1146 msk, hmac, mp_opt->ahmac); 1147 1148 return hmac == mp_opt->ahmac; 1149 } 1150 1151 /* Return false in case of error (or subflow has been reset), 1152 * else return true. 1153 */ 1154 bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb) 1155 { 1156 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); 1157 struct mptcp_sock *msk = mptcp_sk(subflow->conn); 1158 struct mptcp_options_received mp_opt; 1159 struct mptcp_ext *mpext; 1160 1161 if (__mptcp_check_fallback(msk)) { 1162 /* Keep it simple and unconditionally trigger send data cleanup and 1163 * pending queue spooling. We will need to acquire the data lock 1164 * for more accurate checks, and once the lock is acquired, such 1165 * helpers are cheap. 1166 */ 1167 mptcp_data_lock(subflow->conn); 1168 if (sk_stream_memory_free(sk)) 1169 __mptcp_check_push(subflow->conn, sk); 1170 1171 /* on fallback we just need to ignore the msk-level snd_una, as 1172 * this is really plain TCP 1173 */ 1174 __mptcp_snd_una_update(msk, READ_ONCE(msk->snd_nxt)); 1175 1176 __mptcp_data_acked(subflow->conn); 1177 mptcp_data_unlock(subflow->conn); 1178 return true; 1179 } 1180 1181 mptcp_get_options(skb, &mp_opt); 1182 1183 /* The subflow can be in close state only if check_fully_established() 1184 * just sent a reset. If so, tell the caller to ignore the current packet. 1185 */ 1186 if (!check_fully_established(msk, sk, subflow, skb, &mp_opt)) 1187 return sk->sk_state != TCP_CLOSE; 1188 1189 if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) { 1190 if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) && 1191 READ_ONCE(msk->local_key) == mp_opt.rcvr_key) { 1192 WRITE_ONCE(msk->rcv_fastclose, true); 1193 mptcp_schedule_work((struct sock *)msk); 1194 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSERX); 1195 } 1196 1197 if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) && 1198 add_addr_hmac_valid(msk, &mp_opt)) { 1199 if (!mp_opt.echo) { 1200 mptcp_pm_add_addr_received(sk, &mp_opt.addr); 1201 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR); 1202 } else { 1203 mptcp_pm_add_addr_echoed(msk, &mp_opt.addr); 1204 mptcp_pm_del_add_timer(msk, &mp_opt.addr, true); 1205 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD); 1206 } 1207 1208 if (mp_opt.addr.port) 1209 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD); 1210 } 1211 1212 if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR) 1213 mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list); 1214 1215 if (mp_opt.suboptions & OPTION_MPTCP_PRIO) { 1216 mptcp_pm_mp_prio_received(sk, mp_opt.backup); 1217 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX); 1218 } 1219 1220 if (mp_opt.suboptions & OPTION_MPTCP_FAIL) { 1221 mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq); 1222 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX); 1223 } 1224 1225 if (mp_opt.suboptions & OPTION_MPTCP_RST) { 1226 subflow->reset_seen = 1; 1227 subflow->reset_reason = mp_opt.reset_reason; 1228 subflow->reset_transient = mp_opt.reset_transient; 1229 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTRX); 1230 } 1231 1232 if (!(mp_opt.suboptions & OPTION_MPTCP_DSS)) 1233 return true; 1234 } 1235 1236 /* we can't wait for recvmsg() to update the ack_seq, otherwise 1237 * monodirectional flows will stuck 1238 */ 1239 if (mp_opt.use_ack) 1240 ack_update_msk(msk, sk, &mp_opt); 1241 rwin_update(msk, sk, skb); 1242 1243 /* Zero-data-length packets are dropped by the caller and not 1244 * propagated to the MPTCP layer, so the skb extension does not 1245 * need to be allocated or populated. DATA_FIN information, if 1246 * present, needs to be updated here before the skb is freed. 1247 */ 1248 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) { 1249 if (mp_opt.data_fin && mp_opt.data_len == 1 && 1250 mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64)) 1251 mptcp_schedule_work((struct sock *)msk); 1252 1253 return true; 1254 } 1255 1256 mpext = skb_ext_add(skb, SKB_EXT_MPTCP); 1257 if (!mpext) 1258 return false; 1259 1260 memset(mpext, 0, sizeof(*mpext)); 1261 1262 if (likely(mp_opt.use_map)) { 1263 if (mp_opt.mpc_map) { 1264 /* this is an MP_CAPABLE carrying MPTCP data 1265 * we know this map the first chunk of data 1266 */ 1267 mptcp_crypto_key_sha(subflow->remote_key, NULL, 1268 &mpext->data_seq); 1269 mpext->data_seq++; 1270 mpext->subflow_seq = 1; 1271 mpext->dsn64 = 1; 1272 mpext->mpc_map = 1; 1273 mpext->data_fin = 0; 1274 } else { 1275 mpext->data_seq = mp_opt.data_seq; 1276 mpext->subflow_seq = mp_opt.subflow_seq; 1277 mpext->dsn64 = mp_opt.dsn64; 1278 mpext->data_fin = mp_opt.data_fin; 1279 } 1280 mpext->data_len = mp_opt.data_len; 1281 mpext->use_map = 1; 1282 mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD); 1283 1284 if (mpext->csum_reqd) 1285 mpext->csum = mp_opt.csum; 1286 } 1287 1288 return true; 1289 } 1290 1291 static u64 mptcp_set_rwin(struct mptcp_sock *msk, struct tcp_sock *tp, 1292 struct tcphdr *th, u64 ack_seq) 1293 { 1294 const struct sock *ssk = (const struct sock *)tp; 1295 u64 rcv_wnd_old, rcv_wnd_new; 1296 u32 new_win; 1297 u64 win; 1298 1299 rcv_wnd_new = ack_seq + tp->rcv_wnd; 1300 1301 rcv_wnd_old = atomic64_read(&msk->rcv_wnd_sent); 1302 if (after64(rcv_wnd_new, rcv_wnd_old)) { 1303 u64 rcv_wnd; 1304 1305 for (;;) { 1306 rcv_wnd = atomic64_cmpxchg(&msk->rcv_wnd_sent, rcv_wnd_old, rcv_wnd_new); 1307 1308 if (rcv_wnd == rcv_wnd_old) 1309 break; 1310 1311 rcv_wnd_old = rcv_wnd; 1312 if (before64(rcv_wnd_new, rcv_wnd_old)) { 1313 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE); 1314 goto raise_win; 1315 } 1316 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT); 1317 } 1318 goto update_wspace; 1319 } 1320 1321 if (rcv_wnd_new != rcv_wnd_old) { 1322 raise_win: 1323 /* The msk-level rcv wnd is after the tcp level one, 1324 * sync the latter. 1325 */ 1326 rcv_wnd_new = rcv_wnd_old; 1327 win = rcv_wnd_old - ack_seq; 1328 new_win = min_t(u64, win, U32_MAX); 1329 tp->rcv_wnd = new_win; 1330 tcp_update_max_rcv_wnd_seq(tp); 1331 1332 /* Make sure we do not exceed the maximum possible 1333 * scaled window. 1334 */ 1335 if (unlikely(th->syn)) 1336 new_win = min(new_win, 65535U) << tp->rx_opt.rcv_wscale; 1337 if (!tp->rx_opt.rcv_wscale && 1338 READ_ONCE(sock_net(ssk)->ipv4.sysctl_tcp_workaround_signed_windows)) 1339 new_win = min(new_win, MAX_TCP_WINDOW); 1340 else 1341 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); 1342 1343 /* RFC1323 scaling applied */ 1344 new_win >>= tp->rx_opt.rcv_wscale; 1345 th->window = htons(new_win); 1346 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDSHARED); 1347 } 1348 1349 update_wspace: 1350 WRITE_ONCE(msk->old_wspace, tp->rcv_wnd); 1351 return rcv_wnd_new; 1352 } 1353 1354 static void mptcp_track_rwin(struct tcp_sock *tp) 1355 { 1356 const struct sock *ssk = (const struct sock *)tp; 1357 struct mptcp_subflow_context *subflow; 1358 struct mptcp_sock *msk; 1359 1360 if (!ssk) 1361 return; 1362 1363 subflow = mptcp_subflow_ctx(ssk); 1364 msk = mptcp_sk(subflow->conn); 1365 WRITE_ONCE(msk->old_wspace, tp->rcv_wnd); 1366 } 1367 1368 __sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum) 1369 { 1370 struct csum_pseudo_header header; 1371 __wsum csum; 1372 1373 /* cfr RFC 8684 3.3.1.: 1374 * the data sequence number used in the pseudo-header is 1375 * always the 64-bit value, irrespective of what length is used in the 1376 * DSS option itself. 1377 */ 1378 header.data_seq = cpu_to_be64(data_seq); 1379 header.subflow_seq = htonl(subflow_seq); 1380 header.data_len = htons(data_len); 1381 header.csum = 0; 1382 1383 csum = csum_partial(&header, sizeof(header), sum); 1384 return csum_fold(csum); 1385 } 1386 1387 static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext) 1388 { 1389 return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len, 1390 ~csum_unfold(mpext->csum)); 1391 } 1392 1393 static void put_len_csum(u16 len, __sum16 csum, void *data) 1394 { 1395 __sum16 *sumptr = data + 2; 1396 __be16 *ptr = data; 1397 1398 put_unaligned_be16(len, ptr); 1399 1400 put_unaligned(csum, sumptr); 1401 } 1402 1403 void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp, 1404 struct mptcp_out_options *opts) 1405 { 1406 const struct sock *ssk = (const struct sock *)tp; 1407 struct mptcp_subflow_context *subflow; 1408 1409 /* Which options can be used together? 1410 * 1411 * X: mutually exclusive 1412 * O: often used together 1413 * C: can be used together in some cases 1414 * P: could be used together but we prefer not to (optimisations) 1415 * 1416 * Opt: | MPC | MPJ | DSS | ADD | RM | PRIO | FAIL | FC | 1417 * ------|------|------|------|------|------|------|------|------| 1418 * MPC |------|------|------|------|------|------|------|------| 1419 * MPJ | X |------|------|------|------|------|------|------| 1420 * DSS | X | X |------|------|------|------|------|------| 1421 * ADD | X | X | P |------|------|------|------|------| 1422 * RM | C | C | C | P |------|------|------|------| 1423 * PRIO | X | C | C | C | C |------|------|------| 1424 * FAIL | X | X | C | X | X | X |------|------| 1425 * FC | X | X | X | X | X | X | X |------| 1426 * RST | X | X | X | X | X | X | O | O | 1427 * ------|------|------|------|------|------|------|------|------| 1428 * 1429 * The same applies in mptcp_established_options() function. 1430 */ 1431 if (likely(OPTION_MPTCP_DSS & opts->suboptions)) { 1432 struct mptcp_ext *mpext = &opts->ext_copy; 1433 u8 len = TCPOLEN_MPTCP_DSS_BASE; 1434 u8 flags = 0; 1435 1436 if (mpext->use_ack) { 1437 flags = MPTCP_DSS_HAS_ACK; 1438 if (mpext->ack64) { 1439 len += TCPOLEN_MPTCP_DSS_ACK64; 1440 flags |= MPTCP_DSS_ACK64; 1441 } else { 1442 len += TCPOLEN_MPTCP_DSS_ACK32; 1443 } 1444 } 1445 1446 if (mpext->use_map) { 1447 len += TCPOLEN_MPTCP_DSS_MAP64; 1448 1449 /* Use only 64-bit mapping flags for now, add 1450 * support for optional 32-bit mappings later. 1451 */ 1452 flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64; 1453 if (mpext->data_fin) 1454 flags |= MPTCP_DSS_DATA_FIN; 1455 1456 if (opts->csum_reqd) 1457 len += TCPOLEN_MPTCP_DSS_CHECKSUM; 1458 } 1459 1460 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags); 1461 1462 if (mpext->use_ack) { 1463 struct mptcp_sock *msk; 1464 u64 ack_seq; 1465 1466 /* DSS option is set only by mptcp_established_options, 1467 * the caller is __tcp_transmit_skb() and ssk is always 1468 * not NULL. 1469 */ 1470 subflow = mptcp_subflow_ctx(ssk); 1471 msk = mptcp_sk(subflow->conn); 1472 ack_seq = READ_ONCE(msk->ack_seq); 1473 if (mpext->ack64) { 1474 put_unaligned_be64(ack_seq, ptr); 1475 ptr += 2; 1476 } else { 1477 put_unaligned_be32(ack_seq, ptr); 1478 ptr += 1; 1479 } 1480 subflow->rcv_wnd_sent = mptcp_set_rwin(msk, tp, th, 1481 ack_seq); 1482 } 1483 1484 if (mpext->use_map) { 1485 put_unaligned_be64(mpext->data_seq, ptr); 1486 ptr += 2; 1487 put_unaligned_be32(mpext->subflow_seq, ptr); 1488 ptr += 1; 1489 if (opts->csum_reqd) { 1490 /* data_len == 0 is reserved for the infinite mapping, 1491 * the checksum will also be set to 0. 1492 */ 1493 put_len_csum(mpext->data_len, 1494 (mpext->data_len ? mptcp_make_csum(mpext) : 0), 1495 ptr); 1496 } else { 1497 put_unaligned_be32(mpext->data_len << 16 | 1498 TCPOPT_NOP << 8 | TCPOPT_NOP, ptr); 1499 } 1500 ptr += 1; 1501 } 1502 1503 /* We might need to add MP_FAIL options in rare cases */ 1504 if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) 1505 goto mp_fail; 1506 } else if (OPTIONS_MPTCP_MPC & opts->suboptions) { 1507 u8 len, flag = MPTCP_CAP_HMAC_SHA256; 1508 1509 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) { 1510 len = TCPOLEN_MPTCP_MPC_SYN; 1511 } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) { 1512 len = TCPOLEN_MPTCP_MPC_SYNACK; 1513 } else if (opts->data_len) { 1514 len = TCPOLEN_MPTCP_MPC_ACK_DATA; 1515 if (opts->csum_reqd) 1516 len += TCPOLEN_MPTCP_DSS_CHECKSUM; 1517 } else { 1518 len = TCPOLEN_MPTCP_MPC_ACK; 1519 } 1520 1521 if (opts->csum_reqd) 1522 flag |= MPTCP_CAP_CHECKSUM_REQD; 1523 1524 if (!opts->allow_join_id0) 1525 flag |= MPTCP_CAP_DENY_JOIN_ID0; 1526 1527 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len, 1528 MPTCP_SUPPORTED_VERSION, 1529 flag); 1530 1531 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) & 1532 opts->suboptions)) 1533 goto mp_capable_done; 1534 1535 put_unaligned_be64(opts->sndr_key, ptr); 1536 ptr += 2; 1537 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions)) 1538 goto mp_capable_done; 1539 1540 put_unaligned_be64(opts->rcvr_key, ptr); 1541 ptr += 2; 1542 if (!opts->data_len) 1543 goto mp_capable_done; 1544 1545 if (opts->csum_reqd) { 1546 put_len_csum(opts->data_len, 1547 __mptcp_make_csum(opts->data_seq, 1548 opts->subflow_seq, 1549 opts->data_len, 1550 ~csum_unfold(opts->csum)), 1551 ptr); 1552 } else { 1553 put_unaligned_be32(opts->data_len << 16 | 1554 TCPOPT_NOP << 8 | TCPOPT_NOP, ptr); 1555 } 1556 ptr += 1; 1557 1558 /* MPC is additionally mutually exclusive with MP_PRIO */ 1559 goto mp_capable_done; 1560 } else if (OPTIONS_MPTCP_MPJ & opts->suboptions) { 1561 if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) { 1562 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN, 1563 TCPOLEN_MPTCP_MPJ_SYN, 1564 opts->backup, opts->join_id); 1565 put_unaligned_be32(opts->token, ptr); 1566 ptr += 1; 1567 put_unaligned_be32(opts->nonce, ptr); 1568 ptr += 1; 1569 } else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) { 1570 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN, 1571 TCPOLEN_MPTCP_MPJ_SYNACK, 1572 opts->backup, opts->join_id); 1573 put_unaligned_be64(opts->thmac, ptr); 1574 ptr += 2; 1575 put_unaligned_be32(opts->nonce, ptr); 1576 ptr += 1; 1577 } else { 1578 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN, 1579 TCPOLEN_MPTCP_MPJ_ACK, 0, 0); 1580 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN); 1581 ptr += 5; 1582 } 1583 } else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) { 1584 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE; 1585 u8 echo = MPTCP_ADDR_ECHO; 1586 1587 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 1588 if (opts->addr.family == AF_INET6) 1589 len = TCPOLEN_MPTCP_ADD_ADDR6_BASE; 1590 #endif 1591 1592 if (opts->addr.port) 1593 len += TCPOLEN_MPTCP_PORT_LEN; 1594 1595 if (opts->ahmac) { 1596 len += sizeof(opts->ahmac); 1597 echo = 0; 1598 } 1599 1600 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR, 1601 len, echo, opts->addr.id); 1602 if (opts->addr.family == AF_INET) { 1603 memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4); 1604 ptr += 1; 1605 } 1606 #if IS_ENABLED(CONFIG_MPTCP_IPV6) 1607 else if (opts->addr.family == AF_INET6) { 1608 memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16); 1609 ptr += 4; 1610 } 1611 #endif 1612 1613 if (!opts->addr.port) { 1614 if (opts->ahmac) { 1615 put_unaligned_be64(opts->ahmac, ptr); 1616 ptr += 2; 1617 } 1618 } else { 1619 u16 port = ntohs(opts->addr.port); 1620 1621 if (opts->ahmac) { 1622 u8 *bptr = (u8 *)ptr; 1623 1624 put_unaligned_be16(port, bptr); 1625 bptr += 2; 1626 put_unaligned_be64(opts->ahmac, bptr); 1627 bptr += 8; 1628 put_unaligned_be16(TCPOPT_NOP << 8 | 1629 TCPOPT_NOP, bptr); 1630 1631 ptr += 3; 1632 } else { 1633 put_unaligned_be32(port << 16 | 1634 TCPOPT_NOP << 8 | 1635 TCPOPT_NOP, ptr); 1636 ptr += 1; 1637 } 1638 } 1639 } else if (unlikely(OPTION_MPTCP_FASTCLOSE & opts->suboptions)) { 1640 /* FASTCLOSE is mutually exclusive with others except RST */ 1641 *ptr++ = mptcp_option(MPTCPOPT_MP_FASTCLOSE, 1642 TCPOLEN_MPTCP_FASTCLOSE, 1643 0, 0); 1644 put_unaligned_be64(opts->rcvr_key, ptr); 1645 ptr += 2; 1646 1647 if (OPTION_MPTCP_RST & opts->suboptions) 1648 goto mp_rst; 1649 return; 1650 } else if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) { 1651 mp_fail: 1652 /* MP_FAIL is mutually exclusive with others except RST */ 1653 subflow = mptcp_subflow_ctx(ssk); 1654 subflow->send_mp_fail = 0; 1655 1656 *ptr++ = mptcp_option(MPTCPOPT_MP_FAIL, 1657 TCPOLEN_MPTCP_FAIL, 1658 0, 0); 1659 put_unaligned_be64(opts->fail_seq, ptr); 1660 ptr += 2; 1661 1662 if (OPTION_MPTCP_RST & opts->suboptions) 1663 goto mp_rst; 1664 return; 1665 } else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) { 1666 mp_rst: 1667 *ptr++ = mptcp_option(MPTCPOPT_RST, 1668 TCPOLEN_MPTCP_RST, 1669 opts->reset_transient, 1670 opts->reset_reason); 1671 return; 1672 } else if (unlikely(!opts->suboptions)) { 1673 /* Fallback to TCP */ 1674 mptcp_track_rwin(tp); 1675 return; 1676 } 1677 1678 if (OPTION_MPTCP_PRIO & opts->suboptions) { 1679 subflow = mptcp_subflow_ctx(ssk); 1680 subflow->send_mp_prio = 0; 1681 1682 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO, 1683 TCPOLEN_MPTCP_PRIO, 1684 opts->backup, TCPOPT_NOP); 1685 1686 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPPRIOTX); 1687 } 1688 1689 mp_capable_done: 1690 if (OPTION_MPTCP_RM_ADDR & opts->suboptions) { 1691 u8 i = 1; 1692 1693 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR, 1694 TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr, 1695 0, opts->rm_list.ids[0]); 1696 1697 while (i < opts->rm_list.nr) { 1698 u8 id1, id2, id3, id4; 1699 1700 id1 = opts->rm_list.ids[i]; 1701 id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP; 1702 id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP; 1703 id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP; 1704 put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr); 1705 ptr += 1; 1706 i += 4; 1707 } 1708 } 1709 } 1710 1711 __be32 mptcp_get_reset_option(const struct sk_buff *skb) 1712 { 1713 const struct mptcp_ext *ext = mptcp_get_ext(skb); 1714 u8 flags, reason; 1715 1716 if (ext) { 1717 flags = ext->reset_transient; 1718 reason = ext->reset_reason; 1719 1720 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST, 1721 flags, reason); 1722 } 1723 1724 return htonl(0u); 1725 } 1726 EXPORT_SYMBOL_GPL(mptcp_get_reset_option); 1727