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                                          struct mptcp_out_options *opts)
 446 {
 447         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 448         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 449         struct mptcp_ext *mpext;
 450         unsigned int data_len;
 451         u8 len;
 452
 453         /* When skb is not available, we better over-estimate the emitted
 454          * options len. A full DSS option (28 bytes) is longer than
 455          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 456          * tell the caller to defer the estimate to
 457          * mptcp_established_options_dss(), which will reserve enough space.
 458          */
 459         if (!skb)
 460                 return false;
 461
 462         /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
 463         if (subflow->fully_established || snd_data_fin_enable ||
 464             subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 465             sk->sk_state != TCP_ESTABLISHED)
 466                 return false;
 467
 468         if (subflow->mp_capable) {
 469                 mpext = mptcp_get_ext(skb);
 470                 data_len = mpext ? mpext->data_len : 0;
 471
 472                 /* we will check ops->data_len in mptcp_write_options() to
 473                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 474                  * TCPOLEN_MPTCP_MPC_ACK
 475                  */
 476                 opts->data_len = data_len;
 477                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 478                 opts->sndr_key = subflow->local_key;
 479                 opts->rcvr_key = subflow->remote_key;
 480                 opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 481                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 482
 483                 /* Section 3.1.
 484                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 485                  * packets that start the first subflow of an MPTCP connection,
 486                  * as well as the first packet that carries data
 487                  */
 488                 if (data_len > 0) {
 489                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 490                         if (opts->csum_reqd) {
 491                                 /* we need to propagate more info to csum the pseudo hdr */
 492                                 opts->data_seq = mpext->data_seq;
 493                                 opts->subflow_seq = mpext->subflow_seq;
 494                                 opts->csum = mpext->csum;
 495                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
 496                         }
 497                         *size = ALIGN(len, 4);
 498                 } else {
 499                         *size = TCPOLEN_MPTCP_MPC_ACK;
 500                 }
 501
 502                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 503                          subflow, subflow->local_key, subflow->remote_key,
 504                          data_len);
 505
 506                 return true;
 507         } else if (subflow->mp_join) {
 508                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 509                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 510                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 511                 pr_debug("subflow=%p", subflow);
 512
 513                 /* we can use the full delegate action helper only from BH context
 514                  * If we are in process context - sk is flushing the backlog at
 515                  * socket lock release time - just set the appropriate flag, will
 516                  * be handled by the release callback
 517                  */
 518                 if (sock_owned_by_user(sk))
 519                         set_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status);
 520                 else
 521                         mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_ACK);
 522                 return true;
 523         }
 524         return false;
 525 }
 526
 527 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 528                                  struct sk_buff *skb, struct mptcp_ext *ext)
 529 {
 530         /* The write_seq value has already been incremented, so the actual
 531          * sequence number for the DATA_FIN is one less.
 532          */
 533         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 534
 535         if (!ext->use_map || !skb->len) {
 536                 /* RFC6824 requires a DSS mapping with specific values
 537                  * if DATA_FIN is set but no data payload is mapped
 538                  */
 539                 ext->data_fin = 1;
 540                 ext->use_map = 1;
 541                 ext->dsn64 = 1;
 542                 ext->data_seq = data_fin_tx_seq;
 543                 ext->subflow_seq = 0;
 544                 ext->data_len = 1;
 545         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 546                 /* If there's an existing DSS mapping and it is the
 547                  * final mapping, DATA_FIN consumes 1 additional byte of
 548                  * mapping space.
 549                  */
 550                 ext->data_fin = 1;
 551                 ext->data_len++;
 552         }
 553 }
 554
 555 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 556                                           bool snd_data_fin_enable,
 557                                           unsigned int *size,
 558                                           struct mptcp_out_options *opts)
 559 {
 560         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 561         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 562         unsigned int dss_size = 0;
 563         struct mptcp_ext *mpext;
 564         unsigned int ack_size;
 565         bool ret = false;
 566         u64 ack_seq;
 567
 568         opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 569         mpext = skb ? mptcp_get_ext(skb) : NULL;
 570
 571         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 572                 unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 573
 574                 if (mpext) {
 575                         if (opts->csum_reqd)
 576                                 map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
 577
 578                         opts->ext_copy = *mpext;
 579                 }
 580
 581                 dss_size = map_size;
 582                 if (skb && snd_data_fin_enable)
 583                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 584                 opts->suboptions = OPTION_MPTCP_DSS;
 585                 ret = true;
 586         }
 587
 588         /* passive sockets msk will set the 'can_ack' after accept(), even
 589          * if the first subflow may have the already the remote key handy
 590          */
 591         opts->ext_copy.use_ack = 0;
 592         if (!READ_ONCE(msk->can_ack)) {
 593                 *size = ALIGN(dss_size, 4);
 594                 return ret;
 595         }
 596
 597         ack_seq = READ_ONCE(msk->ack_seq);
 598         if (READ_ONCE(msk->use_64bit_ack)) {
 599                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 600                 opts->ext_copy.data_ack = ack_seq;
 601                 opts->ext_copy.ack64 = 1;
 602         } else {
 603                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 604                 opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
 605                 opts->ext_copy.ack64 = 0;
 606         }
 607         opts->ext_copy.use_ack = 1;
 608         opts->suboptions = OPTION_MPTCP_DSS;
 609         WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 610
 611         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 612         if (dss_size == 0)
 613                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 614
 615         dss_size += ack_size;
 616
 617         *size = ALIGN(dss_size, 4);
 618         return true;
 619 }
 620
 621 static u64 add_addr_generate_hmac(u64 key1, u64 key2,
 622                                   struct mptcp_addr_info *addr)
 623 {
 624         u16 port = ntohs(addr->port);
 625         u8 hmac[SHA256_DIGEST_SIZE];
 626         u8 msg[19];
 627         int i = 0;
 628
 629         msg[i++] = addr->id;
 630         if (addr->family == AF_INET) {
 631                 memcpy(&msg[i], &addr->addr.s_addr, 4);
 632                 i += 4;
 633         }
 634 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 635         else if (addr->family == AF_INET6) {
 636                 memcpy(&msg[i], &addr->addr6.s6_addr, 16);
 637                 i += 16;
 638         }
 639 #endif
 640         msg[i++] = port >> 8;
 641         msg[i++] = port & 0xFF;
 642
 643         mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
 644
 645         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 646 }
 647
 648 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 649                                                unsigned int *size,
 650                                                unsigned int remaining,
 651                                                struct mptcp_out_options *opts)
 652 {
 653         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 654         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 655         bool drop_other_suboptions = false;
 656         unsigned int opt_size = *size;
 657         bool echo;
 658         int len;
 659
 660         /* add addr will strip the existing options, be sure to avoid breaking
 661          * MPC/MPJ handshakes
 662          */
 663         if (!mptcp_pm_should_add_signal(msk) ||
 664             (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
 665             !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &opts->addr,
 666                     &echo, &drop_other_suboptions))
 667                 return false;
 668
 669         if (drop_other_suboptions)
 670                 remaining += opt_size;
 671         len = mptcp_add_addr_len(opts->addr.family, echo, !!opts->addr.port);
 672         if (remaining < len)
 673                 return false;
 674
 675         *size = len;
 676         if (drop_other_suboptions) {
 677                 pr_debug("drop other suboptions");
 678                 opts->suboptions = 0;
 679
 680                 /* note that e.g. DSS could have written into the memory
 681                  * aliased by ahmac, we must reset the field here
 682                  * to avoid appending the hmac even for ADD_ADDR echo
 683                  * options
 684                  */
 685                 opts->ahmac = 0;
 686                 *size -= opt_size;
 687         }
 688         opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 689         if (!echo) {
 690                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX);
 691                 opts->ahmac = add_addr_generate_hmac(msk->local_key,
 692                                                      msk->remote_key,
 693                                                      &opts->addr);
 694         } else {
 695                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADDTX);
 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         MPTCP_ADD_STATS(sock_net(sk), MPTCP_MIB_RMADDRTX, opts->rm_list.nr);
 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, opts))
 855                 ret = true;
 856         else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, 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 __mptcp_snd_una_update(struct mptcp_sock *msk, u64 new_snd_una)
1030 {
1031         msk->bytes_acked += new_snd_una - msk->snd_una;
1032         msk->snd_una = new_snd_una;
1033 }
1034
1035 static void ack_update_msk(struct mptcp_sock *msk,
1036                            struct sock *ssk,
1037                            struct mptcp_options_received *mp_opt)
1038 {
1039         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
1040         struct sock *sk = (struct sock *)msk;
1041         u64 old_snd_una;
1042
1043         mptcp_data_lock(sk);
1044
1045         /* avoid ack expansion on update conflict, to reduce the risk of
1046          * wrongly expanding to a future ack sequence number, which is way
1047          * more dangerous than missing an ack
1048          */
1049         old_snd_una = msk->snd_una;
1050         new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
1051
1052         /* ACK for data not even sent yet? Ignore.*/
1053         if (unlikely(after64(new_snd_una, snd_nxt)))
1054                 new_snd_una = old_snd_una;
1055
1056         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
1057
1058         if (after64(new_wnd_end, msk->wnd_end))
1059                 msk->wnd_end = new_wnd_end;
1060
1061         /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
1062         if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
1063                 __mptcp_check_push(sk, ssk);
1064
1065         if (after64(new_snd_una, old_snd_una)) {
1066                 __mptcp_snd_una_update(msk, new_snd_una);
1067                 __mptcp_data_acked(sk);
1068         }
1069         mptcp_data_unlock(sk);
1070
1071         trace_ack_update_msk(mp_opt->data_ack,
1072                              old_snd_una, new_snd_una,
1073                              new_wnd_end, msk->wnd_end);
1074 }
1075
1076 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
1077 {
1078         /* Skip if DATA_FIN was already received.
1079          * If updating simultaneously with the recvmsg loop, values
1080          * should match. If they mismatch, the peer is misbehaving and
1081          * we will prefer the most recent information.
1082          */
1083         if (READ_ONCE(msk->rcv_data_fin))
1084                 return false;
1085
1086         WRITE_ONCE(msk->rcv_data_fin_seq,
1087                    mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1088         WRITE_ONCE(msk->rcv_data_fin, 1);
1089
1090         return true;
1091 }
1092
1093 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1094                                 struct mptcp_options_received *mp_opt)
1095 {
1096         u64 hmac = 0;
1097
1098         if (mp_opt->echo)
1099                 return true;
1100
1101         hmac = add_addr_generate_hmac(msk->remote_key,
1102                                       msk->local_key,
1103                                       &mp_opt->addr);
1104
1105         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1106                  msk, hmac, mp_opt->ahmac);
1107
1108         return hmac == mp_opt->ahmac;
1109 }
1110
1111 /* Return false if a subflow has been reset, else return true */
1112 bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1113 {
1114         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1115         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1116         struct mptcp_options_received mp_opt;
1117         struct mptcp_ext *mpext;
1118
1119         if (__mptcp_check_fallback(msk)) {
1120                 /* Keep it simple and unconditionally trigger send data cleanup and
1121                  * pending queue spooling. We will need to acquire the data lock
1122                  * for more accurate checks, and once the lock is acquired, such
1123                  * helpers are cheap.
1124                  */
1125                 mptcp_data_lock(subflow->conn);
1126                 if (sk_stream_memory_free(sk))
1127                         __mptcp_check_push(subflow->conn, sk);
1128
1129                 /* on fallback we just need to ignore the msk-level snd_una, as
1130                  * this is really plain TCP
1131                  */
1132                 __mptcp_snd_una_update(msk, READ_ONCE(msk->snd_nxt));
1133
1134                 __mptcp_data_acked(subflow->conn);
1135                 mptcp_data_unlock(subflow->conn);
1136                 return true;
1137         }
1138
1139         mptcp_get_options(skb, &mp_opt);
1140
1141         /* The subflow can be in close state only if check_fully_established()
1142          * just sent a reset. If so, tell the caller to ignore the current packet.
1143          */
1144         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1145                 return sk->sk_state != TCP_CLOSE;
1146
1147         if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
1148                 if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
1149                     msk->local_key == mp_opt.rcvr_key) {
1150                         WRITE_ONCE(msk->rcv_fastclose, true);
1151                         mptcp_schedule_work((struct sock *)msk);
1152                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSERX);
1153                 }
1154
1155                 if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
1156                     add_addr_hmac_valid(msk, &mp_opt)) {
1157                         if (!mp_opt.echo) {
1158                                 mptcp_pm_add_addr_received(sk, &mp_opt.addr);
1159                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1160                         } else {
1161                                 mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1162                                 mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1163                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1164                         }
1165
1166                         if (mp_opt.addr.port)
1167                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1168                 }
1169
1170                 if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR)
1171                         mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1172
1173                 if (mp_opt.suboptions & OPTION_MPTCP_PRIO) {
1174                         mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1175                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1176                 }
1177
1178                 if (mp_opt.suboptions & OPTION_MPTCP_FAIL) {
1179                         mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq);
1180                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX);
1181                 }
1182
1183                 if (mp_opt.suboptions & OPTION_MPTCP_RST) {
1184                         subflow->reset_seen = 1;
1185                         subflow->reset_reason = mp_opt.reset_reason;
1186                         subflow->reset_transient = mp_opt.reset_transient;
1187                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTRX);
1188                 }
1189
1190                 if (!(mp_opt.suboptions & OPTION_MPTCP_DSS))
1191                         return true;
1192         }
1193
1194         /* we can't wait for recvmsg() to update the ack_seq, otherwise
1195          * monodirectional flows will stuck
1196          */
1197         if (mp_opt.use_ack)
1198                 ack_update_msk(msk, sk, &mp_opt);
1199
1200         /* Zero-data-length packets are dropped by the caller and not
1201          * propagated to the MPTCP layer, so the skb extension does not
1202          * need to be allocated or populated. DATA_FIN information, if
1203          * present, needs to be updated here before the skb is freed.
1204          */
1205         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1206                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1207                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64))
1208                         mptcp_schedule_work((struct sock *)msk);
1209
1210                 return true;
1211         }
1212
1213         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1214         if (!mpext)
1215                 return true;
1216
1217         memset(mpext, 0, sizeof(*mpext));
1218
1219         if (likely(mp_opt.use_map)) {
1220                 if (mp_opt.mpc_map) {
1221                         /* this is an MP_CAPABLE carrying MPTCP data
1222                          * we know this map the first chunk of data
1223                          */
1224                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1225                                              &mpext->data_seq);
1226                         mpext->data_seq++;
1227                         mpext->subflow_seq = 1;
1228                         mpext->dsn64 = 1;
1229                         mpext->mpc_map = 1;
1230                         mpext->data_fin = 0;
1231                 } else {
1232                         mpext->data_seq = mp_opt.data_seq;
1233                         mpext->subflow_seq = mp_opt.subflow_seq;
1234                         mpext->dsn64 = mp_opt.dsn64;
1235                         mpext->data_fin = mp_opt.data_fin;
1236                 }
1237                 mpext->data_len = mp_opt.data_len;
1238                 mpext->use_map = 1;
1239                 mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD);
1240
1241                 if (mpext->csum_reqd)
1242                         mpext->csum = mp_opt.csum;
1243         }
1244
1245         return true;
1246 }
1247
1248 static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
1249 {
1250         const struct sock *ssk = (const struct sock *)tp;
1251         struct mptcp_subflow_context *subflow;
1252         u64 ack_seq, rcv_wnd_old, rcv_wnd_new;
1253         struct mptcp_sock *msk;
1254         u32 new_win;
1255         u64 win;
1256
1257         subflow = mptcp_subflow_ctx(ssk);
1258         msk = mptcp_sk(subflow->conn);
1259
1260         ack_seq = READ_ONCE(msk->ack_seq);
1261         rcv_wnd_new = ack_seq + tp->rcv_wnd;
1262
1263         rcv_wnd_old = atomic64_read(&msk->rcv_wnd_sent);
1264         if (after64(rcv_wnd_new, rcv_wnd_old)) {
1265                 u64 rcv_wnd;
1266
1267                 for (;;) {
1268                         rcv_wnd = atomic64_cmpxchg(&msk->rcv_wnd_sent, rcv_wnd_old, rcv_wnd_new);
1269
1270                         if (rcv_wnd == rcv_wnd_old)
1271                                 break;
1272
1273                         rcv_wnd_old = rcv_wnd;
1274                         if (before64(rcv_wnd_new, rcv_wnd_old)) {
1275                                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);
1276                                 goto raise_win;
1277                         }
1278                         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);
1279                 }
1280                 return;
1281         }
1282
1283         if (rcv_wnd_new != rcv_wnd_old) {
1284 raise_win:
1285                 win = rcv_wnd_old - ack_seq;
1286                 tp->rcv_wnd = min_t(u64, win, U32_MAX);
1287                 new_win = tp->rcv_wnd;
1288
1289                 /* Make sure we do not exceed the maximum possible
1290                  * scaled window.
1291                  */
1292                 if (unlikely(th->syn))
1293                         new_win = min(new_win, 65535U) << tp->rx_opt.rcv_wscale;
1294                 if (!tp->rx_opt.rcv_wscale &&
1295                     READ_ONCE(sock_net(ssk)->ipv4.sysctl_tcp_workaround_signed_windows))
1296                         new_win = min(new_win, MAX_TCP_WINDOW);
1297                 else
1298                         new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
1299
1300                 /* RFC1323 scaling applied */
1301                 new_win >>= tp->rx_opt.rcv_wscale;
1302                 th->window = htons(new_win);
1303                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDSHARED);
1304         }
1305 }
1306
1307 __sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
1308 {
1309         struct csum_pseudo_header header;
1310         __wsum csum;
1311
1312         /* cfr RFC 8684 3.3.1.:
1313          * the data sequence number used in the pseudo-header is
1314          * always the 64-bit value, irrespective of what length is used in the
1315          * DSS option itself.
1316          */
1317         header.data_seq = cpu_to_be64(data_seq);
1318         header.subflow_seq = htonl(subflow_seq);
1319         header.data_len = htons(data_len);
1320         header.csum = 0;
1321
1322         csum = csum_partial(&header, sizeof(header), sum);
1323         return csum_fold(csum);
1324 }
1325
1326 static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext)
1327 {
1328         return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
1329                                  ~csum_unfold(mpext->csum));
1330 }
1331
1332 static void put_len_csum(u16 len, __sum16 csum, void *data)
1333 {
1334         __sum16 *sumptr = data + 2;
1335         __be16 *ptr = data;
1336
1337         put_unaligned_be16(len, ptr);
1338
1339         put_unaligned(csum, sumptr);
1340 }
1341
1342 void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
1343                          struct mptcp_out_options *opts)
1344 {
1345         const struct sock *ssk = (const struct sock *)tp;
1346         struct mptcp_subflow_context *subflow;
1347
1348         /* Which options can be used together?
1349          *
1350          * X: mutually exclusive
1351          * O: often used together
1352          * C: can be used together in some cases
1353          * P: could be used together but we prefer not to (optimisations)
1354          *
1355          *  Opt: | MPC  | MPJ  | DSS  | ADD  |  RM  | PRIO | FAIL |  FC  |
1356          * ------|------|------|------|------|------|------|------|------|
1357          *  MPC  |------|------|------|------|------|------|------|------|
1358          *  MPJ  |  X   |------|------|------|------|------|------|------|
1359          *  DSS  |  X   |  X   |------|------|------|------|------|------|
1360          *  ADD  |  X   |  X   |  P   |------|------|------|------|------|
1361          *  RM   |  C   |  C   |  C   |  P   |------|------|------|------|
1362          *  PRIO |  X   |  C   |  C   |  C   |  C   |------|------|------|
1363          *  FAIL |  X   |  X   |  C   |  X   |  X   |  X   |------|------|
1364          *  FC   |  X   |  X   |  X   |  X   |  X   |  X   |  X   |------|
1365          *  RST  |  X   |  X   |  X   |  X   |  X   |  X   |  O   |  O   |
1366          * ------|------|------|------|------|------|------|------|------|
1367          *
1368          * The same applies in mptcp_established_options() function.
1369          */
1370         if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
1371                 struct mptcp_ext *mpext = &opts->ext_copy;
1372                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1373                 u8 flags = 0;
1374
1375                 if (mpext->use_ack) {
1376                         flags = MPTCP_DSS_HAS_ACK;
1377                         if (mpext->ack64) {
1378                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1379                                 flags |= MPTCP_DSS_ACK64;
1380                         } else {
1381                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1382                         }
1383                 }
1384
1385                 if (mpext->use_map) {
1386                         len += TCPOLEN_MPTCP_DSS_MAP64;
1387
1388                         /* Use only 64-bit mapping flags for now, add
1389                          * support for optional 32-bit mappings later.
1390                          */
1391                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1392                         if (mpext->data_fin)
1393                                 flags |= MPTCP_DSS_DATA_FIN;
1394
1395                         if (opts->csum_reqd)
1396                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1397                 }
1398
1399                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1400
1401                 if (mpext->use_ack) {
1402                         if (mpext->ack64) {
1403                                 put_unaligned_be64(mpext->data_ack, ptr);
1404                                 ptr += 2;
1405                         } else {
1406                                 put_unaligned_be32(mpext->data_ack32, ptr);
1407                                 ptr += 1;
1408                         }
1409                 }
1410
1411                 if (mpext->use_map) {
1412                         put_unaligned_be64(mpext->data_seq, ptr);
1413                         ptr += 2;
1414                         put_unaligned_be32(mpext->subflow_seq, ptr);
1415                         ptr += 1;
1416                         if (opts->csum_reqd) {
1417                                 /* data_len == 0 is reserved for the infinite mapping,
1418                                  * the checksum will also be set to 0.
1419                                  */
1420                                 put_len_csum(mpext->data_len,
1421                                              (mpext->data_len ? mptcp_make_csum(mpext) : 0),
1422                                              ptr);
1423                         } else {
1424                                 put_unaligned_be32(mpext->data_len << 16 |
1425                                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1426                         }
1427                         ptr += 1;
1428                 }
1429
1430                 /* We might need to add MP_FAIL options in rare cases */
1431                 if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions))
1432                         goto mp_fail;
1433         } else if (OPTIONS_MPTCP_MPC & opts->suboptions) {
1434                 u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1435
1436                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1437                         len = TCPOLEN_MPTCP_MPC_SYN;
1438                 } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1439                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1440                 } else if (opts->data_len) {
1441                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1442                         if (opts->csum_reqd)
1443                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1444                 } else {
1445                         len = TCPOLEN_MPTCP_MPC_ACK;
1446                 }
1447
1448                 if (opts->csum_reqd)
1449                         flag |= MPTCP_CAP_CHECKSUM_REQD;
1450
1451                 if (!opts->allow_join_id0)
1452                         flag |= MPTCP_CAP_DENY_JOIN_ID0;
1453
1454                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1455                                       MPTCP_SUPPORTED_VERSION,
1456                                       flag);
1457
1458                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1459                     opts->suboptions))
1460                         goto mp_capable_done;
1461
1462                 put_unaligned_be64(opts->sndr_key, ptr);
1463                 ptr += 2;
1464                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1465                         goto mp_capable_done;
1466
1467                 put_unaligned_be64(opts->rcvr_key, ptr);
1468                 ptr += 2;
1469                 if (!opts->data_len)
1470                         goto mp_capable_done;
1471
1472                 if (opts->csum_reqd) {
1473                         put_len_csum(opts->data_len,
1474                                      __mptcp_make_csum(opts->data_seq,
1475                                                        opts->subflow_seq,
1476                                                        opts->data_len,
1477                                                        ~csum_unfold(opts->csum)),
1478                                      ptr);
1479                 } else {
1480                         put_unaligned_be32(opts->data_len << 16 |
1481                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1482                 }
1483                 ptr += 1;
1484
1485                 /* MPC is additionally mutually exclusive with MP_PRIO */
1486                 goto mp_capable_done;
1487         } else if (OPTIONS_MPTCP_MPJ & opts->suboptions) {
1488                 if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1489                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1490                                               TCPOLEN_MPTCP_MPJ_SYN,
1491                                               opts->backup, opts->join_id);
1492                         put_unaligned_be32(opts->token, ptr);
1493                         ptr += 1;
1494                         put_unaligned_be32(opts->nonce, ptr);
1495                         ptr += 1;
1496                 } else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1497                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1498                                               TCPOLEN_MPTCP_MPJ_SYNACK,
1499                                               opts->backup, opts->join_id);
1500                         put_unaligned_be64(opts->thmac, ptr);
1501                         ptr += 2;
1502                         put_unaligned_be32(opts->nonce, ptr);
1503                         ptr += 1;
1504                 } else {
1505                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1506                                               TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1507                         memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1508                         ptr += 5;
1509                 }
1510         } else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1511                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1512                 u8 echo = MPTCP_ADDR_ECHO;
1513
1514 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1515                 if (opts->addr.family == AF_INET6)
1516                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1517 #endif
1518
1519                 if (opts->addr.port)
1520                         len += TCPOLEN_MPTCP_PORT_LEN;
1521
1522                 if (opts->ahmac) {
1523                         len += sizeof(opts->ahmac);
1524                         echo = 0;
1525                 }
1526
1527                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1528                                       len, echo, opts->addr.id);
1529                 if (opts->addr.family == AF_INET) {
1530                         memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1531                         ptr += 1;
1532                 }
1533 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1534                 else if (opts->addr.family == AF_INET6) {
1535                         memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1536                         ptr += 4;
1537                 }
1538 #endif
1539
1540                 if (!opts->addr.port) {
1541                         if (opts->ahmac) {
1542                                 put_unaligned_be64(opts->ahmac, ptr);
1543                                 ptr += 2;
1544                         }
1545                 } else {
1546                         u16 port = ntohs(opts->addr.port);
1547
1548                         if (opts->ahmac) {
1549                                 u8 *bptr = (u8 *)ptr;
1550
1551                                 put_unaligned_be16(port, bptr);
1552                                 bptr += 2;
1553                                 put_unaligned_be64(opts->ahmac, bptr);
1554                                 bptr += 8;
1555                                 put_unaligned_be16(TCPOPT_NOP << 8 |
1556                                                    TCPOPT_NOP, bptr);
1557
1558                                 ptr += 3;
1559                         } else {
1560                                 put_unaligned_be32(port << 16 |
1561                                                    TCPOPT_NOP << 8 |
1562                                                    TCPOPT_NOP, ptr);
1563                                 ptr += 1;
1564                         }
1565                 }
1566         } else if (unlikely(OPTION_MPTCP_FASTCLOSE & opts->suboptions)) {
1567                 /* FASTCLOSE is mutually exclusive with others except RST */
1568                 *ptr++ = mptcp_option(MPTCPOPT_MP_FASTCLOSE,
1569                                       TCPOLEN_MPTCP_FASTCLOSE,
1570                                       0, 0);
1571                 put_unaligned_be64(opts->rcvr_key, ptr);
1572                 ptr += 2;
1573
1574                 if (OPTION_MPTCP_RST & opts->suboptions)
1575                         goto mp_rst;
1576                 return;
1577         } else if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) {
1578 mp_fail:
1579                 /* MP_FAIL is mutually exclusive with others except RST */
1580                 subflow = mptcp_subflow_ctx(ssk);
1581                 subflow->send_mp_fail = 0;
1582
1583                 *ptr++ = mptcp_option(MPTCPOPT_MP_FAIL,
1584                                       TCPOLEN_MPTCP_FAIL,
1585                                       0, 0);
1586                 put_unaligned_be64(opts->fail_seq, ptr);
1587                 ptr += 2;
1588
1589                 if (OPTION_MPTCP_RST & opts->suboptions)
1590                         goto mp_rst;
1591                 return;
1592         } else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
1593 mp_rst:
1594                 *ptr++ = mptcp_option(MPTCPOPT_RST,
1595                                       TCPOLEN_MPTCP_RST,
1596                                       opts->reset_transient,
1597                                       opts->reset_reason);
1598                 return;
1599         }
1600
1601         if (OPTION_MPTCP_PRIO & opts->suboptions) {
1602                 subflow = mptcp_subflow_ctx(ssk);
1603                 subflow->send_mp_prio = 0;
1604
1605                 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1606                                       TCPOLEN_MPTCP_PRIO,
1607                                       opts->backup, TCPOPT_NOP);
1608
1609                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPPRIOTX);
1610         }
1611
1612 mp_capable_done:
1613         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1614                 u8 i = 1;
1615
1616                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1617                                       TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1618                                       0, opts->rm_list.ids[0]);
1619
1620                 while (i < opts->rm_list.nr) {
1621                         u8 id1, id2, id3, id4;
1622
1623                         id1 = opts->rm_list.ids[i];
1624                         id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1625                         id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1626                         id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1627                         put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1628                         ptr += 1;
1629                         i += 4;
1630                 }
1631         }
1632
1633         if (tp)
1634                 mptcp_set_rwin(tp, th);
1635 }
1636
1637 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1638 {
1639         const struct mptcp_ext *ext = mptcp_get_ext(skb);
1640         u8 flags, reason;
1641
1642         if (ext) {
1643                 flags = ext->reset_transient;
1644                 reason = ext->reset_reason;
1645
1646                 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1647                                     flags, reason);
1648         }
1649
1650         return htonl(0u);
1651 }
1652 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);