net/mptcp/options.c

   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",
 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                 mp_opt->suboptions |= OPTIONS_MPTCP_MPJ;
 126                 if (opsize == TCPOLEN_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",
 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->backup = *ptr++ & MPTCPOPT_BACKUP;
 138                         mp_opt->join_id = *ptr++;
 139                         mp_opt->thmac = get_unaligned_be64(ptr);
 140                         ptr += 8;
 141                         mp_opt->nonce = get_unaligned_be32(ptr);
 142                         ptr += 4;
 143                         pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
 144                                  mp_opt->backup, mp_opt->join_id,
 145                                  mp_opt->thmac, mp_opt->nonce);
 146                 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 147                         ptr += 2;
 148                         memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 149                         pr_debug("MP_JOIN hmac");
 150                 } else {
 151                         mp_opt->suboptions &= ~OPTIONS_MPTCP_MPJ;
 152                 }
 153                 break;
 154
 155         case MPTCPOPT_DSS:
 156                 pr_debug("DSS");
 157                 ptr++;
 158
 159                 /* we must clear 'mpc_map' be able to detect MP_CAPABLE
 160                  * map vs DSS map in mptcp_incoming_options(), and reconstruct
 161                  * map info accordingly
 162                  */
 163                 mp_opt->mpc_map = 0;
 164                 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 165                 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 166                 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 167                 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 168                 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 169                 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 170
 171                 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
 172                          mp_opt->data_fin, mp_opt->dsn64,
 173                          mp_opt->use_map, mp_opt->ack64,
 174                          mp_opt->use_ack);
 175
 176                 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 177
 178                 if (mp_opt->use_ack) {
 179                         if (mp_opt->ack64)
 180                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 181                         else
 182                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 183                 }
 184
 185                 if (mp_opt->use_map) {
 186                         if (mp_opt->dsn64)
 187                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 188                         else
 189                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 190                 }
 191
 192                 /* Always parse any csum presence combination, we will enforce
 193                  * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
 194                  */
 195                 if (opsize != expected_opsize &&
 196                     opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 197                         break;
 198
 199                 mp_opt->suboptions |= OPTION_MPTCP_DSS;
 200                 if (mp_opt->use_ack) {
 201                         if (mp_opt->ack64) {
 202                                 mp_opt->data_ack = get_unaligned_be64(ptr);
 203                                 ptr += 8;
 204                         } else {
 205                                 mp_opt->data_ack = get_unaligned_be32(ptr);
 206                                 ptr += 4;
 207                         }
 208
 209                         pr_debug("data_ack=%llu", mp_opt->data_ack);
 210                 }
 211
 212                 if (mp_opt->use_map) {
 213                         if (mp_opt->dsn64) {
 214                                 mp_opt->data_seq = get_unaligned_be64(ptr);
 215                                 ptr += 8;
 216                         } else {
 217                                 mp_opt->data_seq = get_unaligned_be32(ptr);
 218                                 ptr += 4;
 219                         }
 220
 221                         mp_opt->subflow_seq = get_unaligned_be32(ptr);
 222                         ptr += 4;
 223
 224                         mp_opt->data_len = get_unaligned_be16(ptr);
 225                         ptr += 2;
 226
 227                         if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
 228                                 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 229                                 mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
 230                                 ptr += 2;
 231                         }
 232
 233                         pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u",
 234                                  mp_opt->data_seq, mp_opt->subflow_seq,
 235                                  mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD),
 236                                  mp_opt->csum);
 237                 }
 238
 239                 break;
 240
 241         case MPTCPOPT_ADD_ADDR:
 242                 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 243                 if (!mp_opt->echo) {
 244                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 245                             opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 246                                 mp_opt->addr.family = AF_INET;
 247 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 248                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 249                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 250                                 mp_opt->addr.family = AF_INET6;
 251 #endif
 252                         else
 253                                 break;
 254                 } else {
 255                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 256                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 257                                 mp_opt->addr.family = AF_INET;
 258 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 259                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 260                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 261                                 mp_opt->addr.family = AF_INET6;
 262 #endif
 263                         else
 264                                 break;
 265                 }
 266
 267                 mp_opt->suboptions |= OPTION_MPTCP_ADD_ADDR;
 268                 mp_opt->addr.id = *ptr++;
 269                 mp_opt->addr.port = 0;
 270                 mp_opt->ahmac = 0;
 271                 if (mp_opt->addr.family == AF_INET) {
 272                         memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
 273                         ptr += 4;
 274                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 275                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 276                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 277                                 ptr += 2;
 278                         }
 279                 }
 280 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 281                 else {
 282                         memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16);
 283                         ptr += 16;
 284                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 285                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 286                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 287                                 ptr += 2;
 288                         }
 289                 }
 290 #endif
 291                 if (!mp_opt->echo) {
 292                         mp_opt->ahmac = get_unaligned_be64(ptr);
 293                         ptr += 8;
 294                 }
 295                 pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d",
 296                          (mp_opt->addr.family == AF_INET6) ? "6" : "",
 297                          mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
 298                 break;
 299
 300         case MPTCPOPT_RM_ADDR:
 301                 if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
 302                     opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
 303                         break;
 304
 305                 ptr++;
 306
 307                 mp_opt->suboptions |= OPTION_MPTCP_RM_ADDR;
 308                 mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
 309                 for (i = 0; i < mp_opt->rm_list.nr; i++)
 310                         mp_opt->rm_list.ids[i] = *ptr++;
 311                 pr_debug("RM_ADDR: rm_list_nr=%d", mp_opt->rm_list.nr);
 312                 break;
 313
 314         case MPTCPOPT_MP_PRIO:
 315                 if (opsize != TCPOLEN_MPTCP_PRIO)
 316                         break;
 317
 318                 mp_opt->suboptions |= OPTION_MPTCP_PRIO;
 319                 mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
 320                 pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
 321                 break;
 322
 323         case MPTCPOPT_MP_FASTCLOSE:
 324                 if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 325                         break;
 326
 327                 ptr += 2;
 328                 mp_opt->rcvr_key = get_unaligned_be64(ptr);
 329                 ptr += 8;
 330                 mp_opt->suboptions |= OPTION_MPTCP_FASTCLOSE;
 331                 pr_debug("MP_FASTCLOSE: recv_key=%llu", mp_opt->rcvr_key);
 332                 break;
 333
 334         case MPTCPOPT_RST:
 335                 if (opsize != TCPOLEN_MPTCP_RST)
 336                         break;
 337
 338                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 339                         break;
 340
 341                 mp_opt->suboptions |= OPTION_MPTCP_RST;
 342                 flags = *ptr++;
 343                 mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
 344                 mp_opt->reset_reason = *ptr;
 345                 pr_debug("MP_RST: transient=%u reason=%u",
 346                          mp_opt->reset_transient, mp_opt->reset_reason);
 347                 break;
 348
 349         case MPTCPOPT_MP_FAIL:
 350                 if (opsize != TCPOLEN_MPTCP_FAIL)
 351                         break;
 352
 353                 ptr += 2;
 354                 mp_opt->suboptions |= OPTION_MPTCP_FAIL;
 355                 mp_opt->fail_seq = get_unaligned_be64(ptr);
 356                 pr_debug("MP_FAIL: data_seq=%llu", mp_opt->fail_seq);
 357                 break;
 358
 359         default:
 360                 break;
 361         }
 362 }
 363
 364 void mptcp_get_options(const struct sk_buff *skb,
 365                        struct mptcp_options_received *mp_opt)
 366 {
 367         const struct tcphdr *th = tcp_hdr(skb);
 368         const unsigned char *ptr;
 369         int length;
 370
 371         /* initialize option status */
 372         mp_opt->suboptions = 0;
 373
 374         length = (th->doff * 4) - sizeof(struct tcphdr);
 375         ptr = (const unsigned char *)(th + 1);
 376
 377         while (length > 0) {
 378                 int opcode = *ptr++;
 379                 int opsize;
 380
 381                 switch (opcode) {
 382                 case TCPOPT_EOL:
 383                         return;
 384                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 385                         length--;
 386                         continue;
 387                 default:
 388                         if (length < 2)
 389                                 return;
 390                         opsize = *ptr++;
 391                         if (opsize < 2) /* "silly options" */
 392                                 return;
 393                         if (opsize > length)
 394                                 return; /* don't parse partial options */
 395                         if (opcode == TCPOPT_MPTCP)
 396                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 397                         ptr += opsize - 2;
 398                         length -= opsize;
 399                 }
 400         }
 401 }
 402
 403 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 404                        unsigned int *size, struct mptcp_out_options *opts)
 405 {
 406         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 407
 408         /* we will use snd_isn to detect first pkt [re]transmission
 409          * in mptcp_established_options_mp()
 410          */
 411         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 412         if (subflow->request_mptcp) {
 413                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 414                 opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
 415                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 416                 *size = TCPOLEN_MPTCP_MPC_SYN;
 417                 return true;
 418         } else if (subflow->request_join) {
 419                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 420                          subflow->local_nonce);
 421                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 422                 opts->join_id = subflow->local_id;
 423                 opts->token = subflow->remote_token;
 424                 opts->nonce = subflow->local_nonce;
 425                 opts->backup = subflow->request_bkup;
 426                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 427                 return true;
 428         }
 429         return false;
 430 }
 431
 432 static void clear_3rdack_retransmission(struct sock *sk)
 433 {
 434         struct inet_connection_sock *icsk = inet_csk(sk);
 435
 436         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 437         icsk->icsk_ack.timeout = 0;
 438         icsk->icsk_ack.ato = 0;
 439         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 440 }
 441
 442 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 443                                          bool snd_data_fin_enable,
 444                                          unsigned int *size,
 445                                          unsigned int remaining,
 446                                          struct mptcp_out_options *opts)
 447 {
 448         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 449         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 450         struct mptcp_ext *mpext;
 451         unsigned int data_len;
 452         u8 len;
 453
 454         /* When skb is not available, we better over-estimate the emitted
 455          * options len. A full DSS option (28 bytes) is longer than
 456          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 457          * tell the caller to defer the estimate to
 458          * mptcp_established_options_dss(), which will reserve enough space.
 459          */
 460         if (!skb)
 461                 return false;
 462
 463         /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
 464         if (subflow->fully_established || snd_data_fin_enable ||
 465             subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 466             sk->sk_state != TCP_ESTABLISHED)
 467                 return false;
 468
 469         if (subflow->mp_capable) {
 470                 mpext = mptcp_get_ext(skb);
 471                 data_len = mpext ? mpext->data_len : 0;
 472
 473                 /* we will check ops->data_len in mptcp_write_options() to
 474                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 475                  * TCPOLEN_MPTCP_MPC_ACK
 476                  */
 477                 opts->data_len = data_len;
 478                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 479                 opts->sndr_key = subflow->local_key;
 480                 opts->rcvr_key = subflow->remote_key;
 481                 opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 482                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 483
 484                 /* Section 3.1.
 485                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 486                  * packets that start the first subflow of an MPTCP connection,
 487                  * as well as the first packet that carries data
 488                  */
 489                 if (data_len > 0) {
 490                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 491                         if (opts->csum_reqd) {
 492                                 /* we need to propagate more info to csum the pseudo hdr */
 493                                 opts->data_seq = mpext->data_seq;
 494                                 opts->subflow_seq = mpext->subflow_seq;
 495                                 opts->csum = mpext->csum;
 496                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
 497                         }
 498                         *size = ALIGN(len, 4);
 499                 } else {
 500                         *size = TCPOLEN_MPTCP_MPC_ACK;
 501                 }
 502
 503                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 504                          subflow, subflow->local_key, subflow->remote_key,
 505                          data_len);
 506
 507                 return true;
 508         } else if (subflow->mp_join) {
 509                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 510                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 511                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 512                 pr_debug("subflow=%p", subflow);
 513
 514                 /* we can use the full delegate action helper only from BH context
 515                  * If we are in process context - sk is flushing the backlog at
 516                  * socket lock release time - just set the appropriate flag, will
 517                  * be handled by the release callback
 518                  */
 519                 if (sock_owned_by_user(sk))
 520                         set_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status);
 521                 else
 522                         mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_ACK);
 523                 return true;
 524         }
 525         return false;
 526 }
 527
 528 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 529                                  struct sk_buff *skb, struct mptcp_ext *ext)
 530 {
 531         /* The write_seq value has already been incremented, so the actual
 532          * sequence number for the DATA_FIN is one less.
 533          */
 534         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 535
 536         if (!ext->use_map || !skb->len) {
 537                 /* RFC6824 requires a DSS mapping with specific values
 538                  * if DATA_FIN is set but no data payload is mapped
 539                  */
 540                 ext->data_fin = 1;
 541                 ext->use_map = 1;
 542                 ext->dsn64 = 1;
 543                 ext->data_seq = data_fin_tx_seq;
 544                 ext->subflow_seq = 0;
 545                 ext->data_len = 1;
 546         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 547                 /* If there's an existing DSS mapping and it is the
 548                  * final mapping, DATA_FIN consumes 1 additional byte of
 549                  * mapping space.
 550                  */
 551                 ext->data_fin = 1;
 552                 ext->data_len++;
 553         }
 554 }
 555
 556 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 557                                           bool snd_data_fin_enable,
 558                                           unsigned int *size,
 559                                           unsigned int remaining,
 560                                           struct mptcp_out_options *opts)
 561 {
 562         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 563         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 564         unsigned int dss_size = 0;
 565         struct mptcp_ext *mpext;
 566         unsigned int ack_size;
 567         bool ret = false;
 568         u64 ack_seq;
 569
 570         opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 571         mpext = skb ? mptcp_get_ext(skb) : NULL;
 572
 573         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 574                 unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 575
 576                 if (mpext) {
 577                         if (opts->csum_reqd)
 578                                 map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
 579
 580                         opts->ext_copy = *mpext;
 581                 }
 582
 583                 remaining -= map_size;
 584                 dss_size = map_size;
 585                 if (skb && snd_data_fin_enable)
 586                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 587                 opts->suboptions = OPTION_MPTCP_DSS;
 588                 ret = true;
 589         }
 590
 591         /* passive sockets msk will set the 'can_ack' after accept(), even
 592          * if the first subflow may have the already the remote key handy
 593          */
 594         opts->ext_copy.use_ack = 0;
 595         if (!READ_ONCE(msk->can_ack)) {
 596                 *size = ALIGN(dss_size, 4);
 597                 return ret;
 598         }
 599
 600         ack_seq = READ_ONCE(msk->ack_seq);
 601         if (READ_ONCE(msk->use_64bit_ack)) {
 602                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 603                 opts->ext_copy.data_ack = ack_seq;
 604                 opts->ext_copy.ack64 = 1;
 605         } else {
 606                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 607                 opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
 608                 opts->ext_copy.ack64 = 0;
 609         }
 610         opts->ext_copy.use_ack = 1;
 611         opts->suboptions = OPTION_MPTCP_DSS;
 612         WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 613
 614         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 615         if (dss_size == 0)
 616                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 617
 618         dss_size += ack_size;
 619
 620         *size = ALIGN(dss_size, 4);
 621         return true;
 622 }
 623
 624 static u64 add_addr_generate_hmac(u64 key1, u64 key2,
 625                                   struct mptcp_addr_info *addr)
 626 {
 627         u16 port = ntohs(addr->port);
 628         u8 hmac[SHA256_DIGEST_SIZE];
 629         u8 msg[19];
 630         int i = 0;
 631
 632         msg[i++] = addr->id;
 633         if (addr->family == AF_INET) {
 634                 memcpy(&msg[i], &addr->addr.s_addr, 4);
 635                 i += 4;
 636         }
 637 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 638         else if (addr->family == AF_INET6) {
 639                 memcpy(&msg[i], &addr->addr6.s6_addr, 16);
 640                 i += 16;
 641         }
 642 #endif
 643         msg[i++] = port >> 8;
 644         msg[i++] = port & 0xFF;
 645
 646         mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
 647
 648         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 649 }
 650
 651 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 652                                                unsigned int *size,
 653                                                unsigned int remaining,
 654                                                struct mptcp_out_options *opts)
 655 {
 656         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 657         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 658         bool drop_other_suboptions = false;
 659         unsigned int opt_size = *size;
 660         bool echo;
 661         int len;
 662
 663         /* add addr will strip the existing options, be sure to avoid breaking
 664          * MPC/MPJ handshakes
 665          */
 666         if (!mptcp_pm_should_add_signal(msk) ||
 667             (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
 668             !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &opts->addr,
 669                     &echo, &drop_other_suboptions))
 670                 return false;
 671
 672         if (drop_other_suboptions)
 673                 remaining += opt_size;
 674         len = mptcp_add_addr_len(opts->addr.family, echo, !!opts->addr.port);
 675         if (remaining < len)
 676                 return false;
 677
 678         *size = len;
 679         if (drop_other_suboptions) {
 680                 pr_debug("drop other suboptions");
 681                 opts->suboptions = 0;
 682
 683                 /* note that e.g. DSS could have written into the memory
 684                  * aliased by ahmac, we must reset the field here
 685                  * to avoid appending the hmac even for ADD_ADDR echo
 686                  * options
 687                  */
 688                 opts->ahmac = 0;
 689                 *size -= opt_size;
 690         }
 691         opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 692         if (!echo) {
 693                 opts->ahmac = add_addr_generate_hmac(msk->local_key,
 694                                                      msk->remote_key,
 695                                                      &opts->addr);
 696         }
 697         pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d",
 698                  opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
 699
 700         return true;
 701 }
 702
 703 static bool mptcp_established_options_rm_addr(struct sock *sk,
 704                                               unsigned int *size,
 705                                               unsigned int remaining,
 706                                               struct mptcp_out_options *opts)
 707 {
 708         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 709         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 710         struct mptcp_rm_list rm_list;
 711         int i, len;
 712
 713         if (!mptcp_pm_should_rm_signal(msk) ||
 714             !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
 715                 return false;
 716
 717         len = mptcp_rm_addr_len(&rm_list);
 718         if (len < 0)
 719                 return false;
 720         if (remaining < len)
 721                 return false;
 722
 723         *size = len;
 724         opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 725         opts->rm_list = rm_list;
 726
 727         for (i = 0; i < opts->rm_list.nr; i++)
 728                 pr_debug("rm_list_ids[%d]=%d", i, opts->rm_list.ids[i]);
 729
 730         return true;
 731 }
 732
 733 static bool mptcp_established_options_mp_prio(struct sock *sk,
 734                                               unsigned int *size,
 735                                               unsigned int remaining,
 736                                               struct mptcp_out_options *opts)
 737 {
 738         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 739
 740         /* can't send MP_PRIO with MPC, as they share the same option space:
 741          * 'backup'. Also it makes no sense at all
 742          */
 743         if (!subflow->send_mp_prio || (opts->suboptions & OPTIONS_MPTCP_MPC))
 744                 return false;
 745
 746         /* account for the trailing 'nop' option */
 747         if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
 748                 return false;
 749
 750         *size = TCPOLEN_MPTCP_PRIO_ALIGN;
 751         opts->suboptions |= OPTION_MPTCP_PRIO;
 752         opts->backup = subflow->request_bkup;
 753
 754         pr_debug("prio=%d", opts->backup);
 755
 756         return true;
 757 }
 758
 759 static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
 760                                                    unsigned int *size,
 761                                                    unsigned int remaining,
 762                                                    struct mptcp_out_options *opts)
 763 {
 764         const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 765
 766         if (remaining < TCPOLEN_MPTCP_RST)
 767                 return false;
 768
 769         *size = TCPOLEN_MPTCP_RST;
 770         opts->suboptions |= OPTION_MPTCP_RST;
 771         opts->reset_transient = subflow->reset_transient;
 772         opts->reset_reason = subflow->reset_reason;
 773         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTTX);
 774
 775         return true;
 776 }
 777
 778 static bool mptcp_established_options_fastclose(struct sock *sk,
 779                                                 unsigned int *size,
 780                                                 unsigned int remaining,
 781                                                 struct mptcp_out_options *opts)
 782 {
 783         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 784         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 785
 786         if (likely(!subflow->send_fastclose))
 787                 return false;
 788
 789         if (remaining < TCPOLEN_MPTCP_FASTCLOSE)
 790                 return false;
 791
 792         *size = TCPOLEN_MPTCP_FASTCLOSE;
 793         opts->suboptions |= OPTION_MPTCP_FASTCLOSE;
 794         opts->rcvr_key = msk->remote_key;
 795
 796         pr_debug("FASTCLOSE key=%llu", opts->rcvr_key);
 797         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSETX);
 798         return true;
 799 }
 800
 801 static bool mptcp_established_options_mp_fail(struct sock *sk,
 802                                               unsigned int *size,
 803                                               unsigned int remaining,
 804                                               struct mptcp_out_options *opts)
 805 {
 806         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 807
 808         if (likely(!subflow->send_mp_fail))
 809                 return false;
 810
 811         if (remaining < TCPOLEN_MPTCP_FAIL)
 812                 return false;
 813
 814         *size = TCPOLEN_MPTCP_FAIL;
 815         opts->suboptions |= OPTION_MPTCP_FAIL;
 816         opts->fail_seq = subflow->map_seq;
 817
 818         pr_debug("MP_FAIL fail_seq=%llu", opts->fail_seq);
 819         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILTX);
 820
 821         return true;
 822 }
 823
 824 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 825                                unsigned int *size, unsigned int remaining,
 826                                struct mptcp_out_options *opts)
 827 {
 828         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 829         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 830         unsigned int opt_size = 0;
 831         bool snd_data_fin;
 832         bool ret = false;
 833
 834         opts->suboptions = 0;
 835
 836         if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb)))
 837                 return false;
 838
 839         if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 840                 if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
 841                     mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
 842                         *size += opt_size;
 843                         remaining -= opt_size;
 844                 }
 845                 /* MP_RST can be used with MP_FASTCLOSE and MP_FAIL if there is room */
 846                 if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
 847                         *size += opt_size;
 848                         remaining -= opt_size;
 849                 }
 850                 return true;
 851         }
 852
 853         snd_data_fin = mptcp_data_fin_enabled(msk);
 854         if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 855                 ret = true;
 856         else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts)) {
 857                 unsigned int mp_fail_size;
 858
 859                 ret = true;
 860                 if (mptcp_established_options_mp_fail(sk, &mp_fail_size,
 861                                                       remaining - opt_size, opts)) {
 862                         *size += opt_size + mp_fail_size;
 863                         remaining -= opt_size - mp_fail_size;
 864                         return true;
 865                 }
 866         }
 867
 868         /* we reserved enough space for the above options, and exceeding the
 869          * TCP option space would be fatal
 870          */
 871         if (WARN_ON_ONCE(opt_size > remaining))
 872                 return false;
 873
 874         *size += opt_size;
 875         remaining -= opt_size;
 876         if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
 877                 *size += opt_size;
 878                 remaining -= opt_size;
 879                 ret = true;
 880         } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 881                 *size += opt_size;
 882                 remaining -= opt_size;
 883                 ret = true;
 884         }
 885
 886         if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
 887                 *size += opt_size;
 888                 remaining -= opt_size;
 889                 ret = true;
 890         }
 891
 892         return ret;
 893 }
 894
 895 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 896                           struct mptcp_out_options *opts)
 897 {
 898         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 899
 900         if (subflow_req->mp_capable) {
 901                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 902                 opts->sndr_key = subflow_req->local_key;
 903                 opts->csum_reqd = subflow_req->csum_reqd;
 904                 opts->allow_join_id0 = subflow_req->allow_join_id0;
 905                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 906                 pr_debug("subflow_req=%p, local_key=%llu",
 907                          subflow_req, subflow_req->local_key);
 908                 return true;
 909         } else if (subflow_req->mp_join) {
 910                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 911                 opts->backup = subflow_req->backup;
 912                 opts->join_id = subflow_req->local_id;
 913                 opts->thmac = subflow_req->thmac;
 914                 opts->nonce = subflow_req->local_nonce;
 915                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 916                          subflow_req, opts->backup, opts->join_id,
 917                          opts->thmac, opts->nonce);
 918                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 919                 return true;
 920         }
 921         return false;
 922 }
 923
 924 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 925                                     struct mptcp_subflow_context *subflow,
 926                                     struct sk_buff *skb,
 927                                     struct mptcp_options_received *mp_opt)
 928 {
 929         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 930          * will make the subflow fully established
 931          */
 932         if (likely(subflow->fully_established)) {
 933                 /* on passive sockets, check for 3rd ack retransmission
 934                  * note that msk is always set by subflow_syn_recv_sock()
 935                  * for mp_join subflows
 936                  */
 937                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 938                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 939                     subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) &&
 940                     !subflow->request_join)
 941                         tcp_send_ack(ssk);
 942                 goto check_notify;
 943         }
 944
 945         /* we must process OoO packets before the first subflow is fully
 946          * established. OoO packets are instead a protocol violation
 947          * for MP_JOIN subflows as the peer must not send any data
 948          * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 949          */
 950         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 951                 if (subflow->mp_join)
 952                         goto reset;
 953                 if (subflow->is_mptfo && mp_opt->suboptions & OPTION_MPTCP_MPC_ACK)
 954                         goto set_fully_established;
 955                 return subflow->mp_capable;
 956         }
 957
 958         if (subflow->remote_key_valid &&
 959             (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) ||
 960              ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) && !mp_opt->echo))) {
 961                 /* subflows are fully established as soon as we get any
 962                  * additional ack, including ADD_ADDR.
 963                  */
 964                 subflow->fully_established = 1;
 965                 WRITE_ONCE(msk->fully_established, true);
 966                 goto check_notify;
 967         }
 968
 969         /* If the first established packet does not contain MP_CAPABLE + data
 970          * then fallback to TCP. Fallback scenarios requires a reset for
 971          * MP_JOIN subflows.
 972          */
 973         if (!(mp_opt->suboptions & OPTIONS_MPTCP_MPC)) {
 974                 if (subflow->mp_join)
 975                         goto reset;
 976                 subflow->mp_capable = 0;
 977                 pr_fallback(msk);
 978                 mptcp_do_fallback(ssk);
 979                 return false;
 980         }
 981
 982         if (mp_opt->deny_join_id0)
 983                 WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 984
 985 set_fully_established:
 986         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 987                 pr_warn_once("bogus mpc option on established client sk");
 988         mptcp_subflow_fully_established(subflow, mp_opt);
 989
 990 check_notify:
 991         /* if the subflow is not already linked into the conn_list, we can't
 992          * notify the PM: this subflow is still on the listener queue
 993          * and the PM possibly acquiring the subflow lock could race with
 994          * the listener close
 995          */
 996         if (likely(subflow->pm_notified) || list_empty(&subflow->node))
 997                 return true;
 998
 999         subflow->pm_notified = 1;
1000         if (subflow->mp_join) {
1001                 clear_3rdack_retransmission(ssk);
1002                 mptcp_pm_subflow_established(msk);
1003         } else {
1004                 mptcp_pm_fully_established(msk, ssk);
1005         }
1006         return true;
1007
1008 reset:
1009         mptcp_subflow_reset(ssk);
1010         return false;
1011 }
1012
1013 u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
1014 {
1015         u32 old_seq32, cur_seq32;
1016
1017         old_seq32 = (u32)old_seq;
1018         cur_seq32 = (u32)cur_seq;
1019         cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
1020         if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
1021                 return cur_seq + (1LL << 32);
1022
1023         /* reverse wrap could happen, too */
1024         if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
1025                 return cur_seq - (1LL << 32);
1026         return cur_seq;
1027 }
1028
1029 static void ack_update_msk(struct mptcp_sock *msk,
1030                            struct sock *ssk,
1031                            struct mptcp_options_received *mp_opt)
1032 {
1033         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
1034         struct sock *sk = (struct sock *)msk;
1035         u64 old_snd_una;
1036
1037         mptcp_data_lock(sk);
1038
1039         /* avoid ack expansion on update conflict, to reduce the risk of
1040          * wrongly expanding to a future ack sequence number, which is way
1041          * more dangerous than missing an ack
1042          */
1043         old_snd_una = msk->snd_una;
1044         new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
1045
1046         /* ACK for data not even sent yet? Ignore.*/
1047         if (unlikely(after64(new_snd_una, snd_nxt)))
1048                 new_snd_una = old_snd_una;
1049
1050         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
1051
1052         if (after64(new_wnd_end, msk->wnd_end))
1053                 msk->wnd_end = new_wnd_end;
1054
1055         /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
1056         if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
1057                 __mptcp_check_push(sk, ssk);
1058
1059         if (after64(new_snd_una, old_snd_una)) {
1060                 msk->snd_una = new_snd_una;
1061                 __mptcp_data_acked(sk);
1062         }
1063         mptcp_data_unlock(sk);
1064
1065         trace_ack_update_msk(mp_opt->data_ack,
1066                              old_snd_una, new_snd_una,
1067                              new_wnd_end, msk->wnd_end);
1068 }
1069
1070 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
1071 {
1072         /* Skip if DATA_FIN was already received.
1073          * If updating simultaneously with the recvmsg loop, values
1074          * should match. If they mismatch, the peer is misbehaving and
1075          * we will prefer the most recent information.
1076          */
1077         if (READ_ONCE(msk->rcv_data_fin))
1078                 return false;
1079
1080         WRITE_ONCE(msk->rcv_data_fin_seq,
1081                    mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1082         WRITE_ONCE(msk->rcv_data_fin, 1);
1083
1084         return true;
1085 }
1086
1087 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1088                                 struct mptcp_options_received *mp_opt)
1089 {
1090         u64 hmac = 0;
1091
1092         if (mp_opt->echo)
1093                 return true;
1094
1095         hmac = add_addr_generate_hmac(msk->remote_key,
1096                                       msk->local_key,
1097                                       &mp_opt->addr);
1098
1099         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1100                  msk, hmac, mp_opt->ahmac);
1101
1102         return hmac == mp_opt->ahmac;
1103 }
1104
1105 /* Return false if a subflow has been reset, else return true */
1106 bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1107 {
1108         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1109         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1110         struct mptcp_options_received mp_opt;
1111         struct mptcp_ext *mpext;
1112
1113         if (__mptcp_check_fallback(msk)) {
1114                 /* Keep it simple and unconditionally trigger send data cleanup and
1115                  * pending queue spooling. We will need to acquire the data lock
1116                  * for more accurate checks, and once the lock is acquired, such
1117                  * helpers are cheap.
1118                  */
1119                 mptcp_data_lock(subflow->conn);
1120                 if (sk_stream_memory_free(sk))
1121                         __mptcp_check_push(subflow->conn, sk);
1122                 __mptcp_data_acked(subflow->conn);
1123                 mptcp_data_unlock(subflow->conn);
1124                 return true;
1125         }
1126
1127         mptcp_get_options(skb, &mp_opt);
1128
1129         /* The subflow can be in close state only if check_fully_established()
1130          * just sent a reset. If so, tell the caller to ignore the current packet.
1131          */
1132         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1133                 return sk->sk_state != TCP_CLOSE;
1134
1135         if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
1136                 if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
1137                     msk->local_key == mp_opt.rcvr_key) {
1138                         WRITE_ONCE(msk->rcv_fastclose, true);
1139                         mptcp_schedule_work((struct sock *)msk);
1140                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSERX);
1141                 }
1142
1143                 if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
1144                     add_addr_hmac_valid(msk, &mp_opt)) {
1145                         if (!mp_opt.echo) {
1146                                 mptcp_pm_add_addr_received(sk, &mp_opt.addr);
1147                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1148                         } else {
1149                                 mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1150                                 mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1151                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1152                         }
1153
1154                         if (mp_opt.addr.port)
1155                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1156                 }
1157
1158                 if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR)
1159                         mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1160
1161                 if (mp_opt.suboptions & OPTION_MPTCP_PRIO) {
1162                         mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1163                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1164                 }
1165
1166                 if (mp_opt.suboptions & OPTION_MPTCP_FAIL) {
1167                         mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq);
1168                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX);
1169                 }
1170
1171                 if (mp_opt.suboptions & OPTION_MPTCP_RST) {
1172                         subflow->reset_seen = 1;
1173                         subflow->reset_reason = mp_opt.reset_reason;
1174                         subflow->reset_transient = mp_opt.reset_transient;
1175                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTRX);
1176                 }
1177
1178                 if (!(mp_opt.suboptions & OPTION_MPTCP_DSS))
1179                         return true;
1180         }
1181
1182         /* we can't wait for recvmsg() to update the ack_seq, otherwise
1183          * monodirectional flows will stuck
1184          */
1185         if (mp_opt.use_ack)
1186                 ack_update_msk(msk, sk, &mp_opt);
1187
1188         /* Zero-data-length packets are dropped by the caller and not
1189          * propagated to the MPTCP layer, so the skb extension does not
1190          * need to be allocated or populated. DATA_FIN information, if
1191          * present, needs to be updated here before the skb is freed.
1192          */
1193         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1194                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1195                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64))
1196                         mptcp_schedule_work((struct sock *)msk);
1197
1198                 return true;
1199         }
1200
1201         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1202         if (!mpext)
1203                 return true;
1204
1205         memset(mpext, 0, sizeof(*mpext));
1206
1207         if (likely(mp_opt.use_map)) {
1208                 if (mp_opt.mpc_map) {
1209                         /* this is an MP_CAPABLE carrying MPTCP data
1210                          * we know this map the first chunk of data
1211                          */
1212                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1213                                              &mpext->data_seq);
1214                         mpext->data_seq++;
1215                         mpext->subflow_seq = 1;
1216                         mpext->dsn64 = 1;
1217                         mpext->mpc_map = 1;
1218                         mpext->data_fin = 0;
1219                 } else {
1220                         mpext->data_seq = mp_opt.data_seq;
1221                         mpext->subflow_seq = mp_opt.subflow_seq;
1222                         mpext->dsn64 = mp_opt.dsn64;
1223                         mpext->data_fin = mp_opt.data_fin;
1224                 }
1225                 mpext->data_len = mp_opt.data_len;
1226                 mpext->use_map = 1;
1227                 mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD);
1228
1229                 if (mpext->csum_reqd)
1230                         mpext->csum = mp_opt.csum;
1231         }
1232
1233         return true;
1234 }
1235
1236 static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
1237 {
1238         const struct sock *ssk = (const struct sock *)tp;
1239         struct mptcp_subflow_context *subflow;
1240         u64 ack_seq, rcv_wnd_old, rcv_wnd_new;
1241         struct mptcp_sock *msk;
1242         u32 new_win;
1243         u64 win;
1244
1245         subflow = mptcp_subflow_ctx(ssk);
1246         msk = mptcp_sk(subflow->conn);
1247
1248         ack_seq = READ_ONCE(msk->ack_seq);
1249         rcv_wnd_new = ack_seq + tp->rcv_wnd;
1250
1251         rcv_wnd_old = atomic64_read(&msk->rcv_wnd_sent);
1252         if (after64(rcv_wnd_new, rcv_wnd_old)) {
1253                 u64 rcv_wnd;
1254
1255                 for (;;) {
1256                         rcv_wnd = atomic64_cmpxchg(&msk->rcv_wnd_sent, rcv_wnd_old, rcv_wnd_new);
1257
1258                         if (rcv_wnd == rcv_wnd_old)
1259                                 break;
1260                         if (before64(rcv_wnd_new, rcv_wnd)) {
1261                                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);
1262                                 goto raise_win;
1263                         }
1264                         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);
1265                         rcv_wnd_old = rcv_wnd;
1266                 }
1267                 return;
1268         }
1269
1270         if (rcv_wnd_new != rcv_wnd_old) {
1271 raise_win:
1272                 win = rcv_wnd_old - ack_seq;
1273                 tp->rcv_wnd = min_t(u64, win, U32_MAX);
1274                 new_win = tp->rcv_wnd;
1275
1276                 /* Make sure we do not exceed the maximum possible
1277                  * scaled window.
1278                  */
1279                 if (unlikely(th->syn))
1280                         new_win = min(new_win, 65535U) << tp->rx_opt.rcv_wscale;
1281                 if (!tp->rx_opt.rcv_wscale &&
1282                     READ_ONCE(sock_net(ssk)->ipv4.sysctl_tcp_workaround_signed_windows))
1283                         new_win = min(new_win, MAX_TCP_WINDOW);
1284                 else
1285                         new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
1286
1287                 /* RFC1323 scaling applied */
1288                 new_win >>= tp->rx_opt.rcv_wscale;
1289                 th->window = htons(new_win);
1290                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDSHARED);
1291         }
1292 }
1293
1294 __sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
1295 {
1296         struct csum_pseudo_header header;
1297         __wsum csum;
1298
1299         /* cfr RFC 8684 3.3.1.:
1300          * the data sequence number used in the pseudo-header is
1301          * always the 64-bit value, irrespective of what length is used in the
1302          * DSS option itself.
1303          */
1304         header.data_seq = cpu_to_be64(data_seq);
1305         header.subflow_seq = htonl(subflow_seq);
1306         header.data_len = htons(data_len);
1307         header.csum = 0;
1308
1309         csum = csum_partial(&header, sizeof(header), sum);
1310         return csum_fold(csum);
1311 }
1312
1313 static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext)
1314 {
1315         return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
1316                                  ~csum_unfold(mpext->csum));
1317 }
1318
1319 static void put_len_csum(u16 len, __sum16 csum, void *data)
1320 {
1321         __sum16 *sumptr = data + 2;
1322         __be16 *ptr = data;
1323
1324         put_unaligned_be16(len, ptr);
1325
1326         put_unaligned(csum, sumptr);
1327 }
1328
1329 void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
1330                          struct mptcp_out_options *opts)
1331 {
1332         const struct sock *ssk = (const struct sock *)tp;
1333         struct mptcp_subflow_context *subflow;
1334
1335         /* Which options can be used together?
1336          *
1337          * X: mutually exclusive
1338          * O: often used together
1339          * C: can be used together in some cases
1340          * P: could be used together but we prefer not to (optimisations)
1341          *
1342          *  Opt: | MPC  | MPJ  | DSS  | ADD  |  RM  | PRIO | FAIL |  FC  |
1343          * ------|------|------|------|------|------|------|------|------|
1344          *  MPC  |------|------|------|------|------|------|------|------|
1345          *  MPJ  |  X   |------|------|------|------|------|------|------|
1346          *  DSS  |  X   |  X   |------|------|------|------|------|------|
1347          *  ADD  |  X   |  X   |  P   |------|------|------|------|------|
1348          *  RM   |  C   |  C   |  C   |  P   |------|------|------|------|
1349          *  PRIO |  X   |  C   |  C   |  C   |  C   |------|------|------|
1350          *  FAIL |  X   |  X   |  C   |  X   |  X   |  X   |------|------|
1351          *  FC   |  X   |  X   |  X   |  X   |  X   |  X   |  X   |------|
1352          *  RST  |  X   |  X   |  X   |  X   |  X   |  X   |  O   |  O   |
1353          * ------|------|------|------|------|------|------|------|------|
1354          *
1355          * The same applies in mptcp_established_options() function.
1356          */
1357         if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
1358                 struct mptcp_ext *mpext = &opts->ext_copy;
1359                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1360                 u8 flags = 0;
1361
1362                 if (mpext->use_ack) {
1363                         flags = MPTCP_DSS_HAS_ACK;
1364                         if (mpext->ack64) {
1365                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1366                                 flags |= MPTCP_DSS_ACK64;
1367                         } else {
1368                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1369                         }
1370                 }
1371
1372                 if (mpext->use_map) {
1373                         len += TCPOLEN_MPTCP_DSS_MAP64;
1374
1375                         /* Use only 64-bit mapping flags for now, add
1376                          * support for optional 32-bit mappings later.
1377                          */
1378                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1379                         if (mpext->data_fin)
1380                                 flags |= MPTCP_DSS_DATA_FIN;
1381
1382                         if (opts->csum_reqd)
1383                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1384                 }
1385
1386                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1387
1388                 if (mpext->use_ack) {
1389                         if (mpext->ack64) {
1390                                 put_unaligned_be64(mpext->data_ack, ptr);
1391                                 ptr += 2;
1392                         } else {
1393                                 put_unaligned_be32(mpext->data_ack32, ptr);
1394                                 ptr += 1;
1395                         }
1396                 }
1397
1398                 if (mpext->use_map) {
1399                         put_unaligned_be64(mpext->data_seq, ptr);
1400                         ptr += 2;
1401                         put_unaligned_be32(mpext->subflow_seq, ptr);
1402                         ptr += 1;
1403                         if (opts->csum_reqd) {
1404                                 /* data_len == 0 is reserved for the infinite mapping,
1405                                  * the checksum will also be set to 0.
1406                                  */
1407                                 put_len_csum(mpext->data_len,
1408                                              (mpext->data_len ? mptcp_make_csum(mpext) : 0),
1409                                              ptr);
1410                         } else {
1411                                 put_unaligned_be32(mpext->data_len << 16 |
1412                                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1413                         }
1414                         ptr += 1;
1415                 }
1416
1417                 /* We might need to add MP_FAIL options in rare cases */
1418                 if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions))
1419                         goto mp_fail;
1420         } else if (OPTIONS_MPTCP_MPC & opts->suboptions) {
1421                 u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1422
1423                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1424                         len = TCPOLEN_MPTCP_MPC_SYN;
1425                 } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1426                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1427                 } else if (opts->data_len) {
1428                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1429                         if (opts->csum_reqd)
1430                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1431                 } else {
1432                         len = TCPOLEN_MPTCP_MPC_ACK;
1433                 }
1434
1435                 if (opts->csum_reqd)
1436                         flag |= MPTCP_CAP_CHECKSUM_REQD;
1437
1438                 if (!opts->allow_join_id0)
1439                         flag |= MPTCP_CAP_DENY_JOIN_ID0;
1440
1441                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1442                                       MPTCP_SUPPORTED_VERSION,
1443                                       flag);
1444
1445                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1446                     opts->suboptions))
1447                         goto mp_capable_done;
1448
1449                 put_unaligned_be64(opts->sndr_key, ptr);
1450                 ptr += 2;
1451                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1452                         goto mp_capable_done;
1453
1454                 put_unaligned_be64(opts->rcvr_key, ptr);
1455                 ptr += 2;
1456                 if (!opts->data_len)
1457                         goto mp_capable_done;
1458
1459                 if (opts->csum_reqd) {
1460                         put_len_csum(opts->data_len,
1461                                      __mptcp_make_csum(opts->data_seq,
1462                                                        opts->subflow_seq,
1463                                                        opts->data_len,
1464                                                        ~csum_unfold(opts->csum)),
1465                                      ptr);
1466                 } else {
1467                         put_unaligned_be32(opts->data_len << 16 |
1468                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1469                 }
1470                 ptr += 1;
1471
1472                 /* MPC is additionally mutually exclusive with MP_PRIO */
1473                 goto mp_capable_done;
1474         } else if (OPTIONS_MPTCP_MPJ & opts->suboptions) {
1475                 if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1476                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1477                                               TCPOLEN_MPTCP_MPJ_SYN,
1478                                               opts->backup, opts->join_id);
1479                         put_unaligned_be32(opts->token, ptr);
1480                         ptr += 1;
1481                         put_unaligned_be32(opts->nonce, ptr);
1482                         ptr += 1;
1483                 } else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1484                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1485                                               TCPOLEN_MPTCP_MPJ_SYNACK,
1486                                               opts->backup, opts->join_id);
1487                         put_unaligned_be64(opts->thmac, ptr);
1488                         ptr += 2;
1489                         put_unaligned_be32(opts->nonce, ptr);
1490                         ptr += 1;
1491                 } else {
1492                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1493                                               TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1494                         memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1495                         ptr += 5;
1496                 }
1497         } else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1498                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1499                 u8 echo = MPTCP_ADDR_ECHO;
1500
1501 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1502                 if (opts->addr.family == AF_INET6)
1503                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1504 #endif
1505
1506                 if (opts->addr.port)
1507                         len += TCPOLEN_MPTCP_PORT_LEN;
1508
1509                 if (opts->ahmac) {
1510                         len += sizeof(opts->ahmac);
1511                         echo = 0;
1512                 }
1513
1514                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1515                                       len, echo, opts->addr.id);
1516                 if (opts->addr.family == AF_INET) {
1517                         memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1518                         ptr += 1;
1519                 }
1520 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1521                 else if (opts->addr.family == AF_INET6) {
1522                         memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1523                         ptr += 4;
1524                 }
1525 #endif
1526
1527                 if (!opts->addr.port) {
1528                         if (opts->ahmac) {
1529                                 put_unaligned_be64(opts->ahmac, ptr);
1530                                 ptr += 2;
1531                         }
1532                 } else {
1533                         u16 port = ntohs(opts->addr.port);
1534
1535                         if (opts->ahmac) {
1536                                 u8 *bptr = (u8 *)ptr;
1537
1538                                 put_unaligned_be16(port, bptr);
1539                                 bptr += 2;
1540                                 put_unaligned_be64(opts->ahmac, bptr);
1541                                 bptr += 8;
1542                                 put_unaligned_be16(TCPOPT_NOP << 8 |
1543                                                    TCPOPT_NOP, bptr);
1544
1545                                 ptr += 3;
1546                         } else {
1547                                 put_unaligned_be32(port << 16 |
1548                                                    TCPOPT_NOP << 8 |
1549                                                    TCPOPT_NOP, ptr);
1550                                 ptr += 1;
1551                         }
1552                 }
1553         } else if (unlikely(OPTION_MPTCP_FASTCLOSE & opts->suboptions)) {
1554                 /* FASTCLOSE is mutually exclusive with others except RST */
1555                 *ptr++ = mptcp_option(MPTCPOPT_MP_FASTCLOSE,
1556                                       TCPOLEN_MPTCP_FASTCLOSE,
1557                                       0, 0);
1558                 put_unaligned_be64(opts->rcvr_key, ptr);
1559                 ptr += 2;
1560
1561                 if (OPTION_MPTCP_RST & opts->suboptions)
1562                         goto mp_rst;
1563                 return;
1564         } else if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) {
1565 mp_fail:
1566                 /* MP_FAIL is mutually exclusive with others except RST */
1567                 subflow = mptcp_subflow_ctx(ssk);
1568                 subflow->send_mp_fail = 0;
1569
1570                 *ptr++ = mptcp_option(MPTCPOPT_MP_FAIL,
1571                                       TCPOLEN_MPTCP_FAIL,
1572                                       0, 0);
1573                 put_unaligned_be64(opts->fail_seq, ptr);
1574                 ptr += 2;
1575
1576                 if (OPTION_MPTCP_RST & opts->suboptions)
1577                         goto mp_rst;
1578                 return;
1579         } else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
1580 mp_rst:
1581                 *ptr++ = mptcp_option(MPTCPOPT_RST,
1582                                       TCPOLEN_MPTCP_RST,
1583                                       opts->reset_transient,
1584                                       opts->reset_reason);
1585                 return;
1586         }
1587
1588         if (OPTION_MPTCP_PRIO & opts->suboptions) {
1589                 subflow = mptcp_subflow_ctx(ssk);
1590                 subflow->send_mp_prio = 0;
1591
1592                 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1593                                       TCPOLEN_MPTCP_PRIO,
1594                                       opts->backup, TCPOPT_NOP);
1595
1596                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPPRIOTX);
1597         }
1598
1599 mp_capable_done:
1600         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1601                 u8 i = 1;
1602
1603                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1604                                       TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1605                                       0, opts->rm_list.ids[0]);
1606
1607                 while (i < opts->rm_list.nr) {
1608                         u8 id1, id2, id3, id4;
1609
1610                         id1 = opts->rm_list.ids[i];
1611                         id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1612                         id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1613                         id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1614                         put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1615                         ptr += 1;
1616                         i += 4;
1617                 }
1618         }
1619
1620         if (tp)
1621                 mptcp_set_rwin(tp, th);
1622 }
1623
1624 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1625 {
1626         const struct mptcp_ext *ext = mptcp_get_ext(skb);
1627         u8 flags, reason;
1628
1629         if (ext) {
1630                 flags = ext->reset_transient;
1631                 reason = ext->reset_reason;
1632
1633                 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1634                                     flags, reason);
1635         }
1636
1637         return htonl(0u);
1638 }
1639 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);