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\n",
 120                          version, flags, opsize, mp_opt->sndr_key,
 121                          mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum);
 122                 break;
 123
 124         case MPTCPOPT_MP_JOIN:
 125                 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 126                         mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYN;
 127                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 128                         mp_opt->join_id = *ptr++;
 129                         mp_opt->token = get_unaligned_be32(ptr);
 130                         ptr += 4;
 131                         mp_opt->nonce = get_unaligned_be32(ptr);
 132                         ptr += 4;
 133                         pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u\n",
 134                                  mp_opt->backup, mp_opt->join_id,
 135                                  mp_opt->token, mp_opt->nonce);
 136                 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
 137                         mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYNACK;
 138                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 139                         mp_opt->join_id = *ptr++;
 140                         mp_opt->thmac = get_unaligned_be64(ptr);
 141                         ptr += 8;
 142                         mp_opt->nonce = get_unaligned_be32(ptr);
 143                         ptr += 4;
 144                         pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u\n",
 145                                  mp_opt->backup, mp_opt->join_id,
 146                                  mp_opt->thmac, mp_opt->nonce);
 147                 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 148                         mp_opt->suboptions |= OPTION_MPTCP_MPJ_ACK;
 149                         ptr += 2;
 150                         memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 151                         pr_debug("MP_JOIN hmac\n");
 152                 }
 153                 break;
 154
 155         case MPTCPOPT_DSS:
 156                 pr_debug("DSS\n");
 157                 ptr++;
 158
 159                 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 160                 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 161                 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 162                 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 163                 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 164                 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 165
 166                 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d\n",
 167                          mp_opt->data_fin, mp_opt->dsn64,
 168                          mp_opt->use_map, mp_opt->ack64,
 169                          mp_opt->use_ack);
 170
 171                 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 172
 173                 if (mp_opt->use_ack) {
 174                         if (mp_opt->ack64)
 175                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 176                         else
 177                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 178                 }
 179
 180                 if (mp_opt->use_map) {
 181                         if (mp_opt->dsn64)
 182                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 183                         else
 184                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 185                 }
 186
 187                 /* Always parse any csum presence combination, we will enforce
 188                  * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
 189                  */
 190                 if (opsize != expected_opsize &&
 191                     opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 192                         break;
 193
 194                 mp_opt->suboptions |= OPTION_MPTCP_DSS;
 195                 if (mp_opt->use_ack) {
 196                         if (mp_opt->ack64) {
 197                                 mp_opt->data_ack = get_unaligned_be64(ptr);
 198                                 ptr += 8;
 199                         } else {
 200                                 mp_opt->data_ack = get_unaligned_be32(ptr);
 201                                 ptr += 4;
 202                         }
 203
 204                         pr_debug("data_ack=%llu\n", mp_opt->data_ack);
 205                 }
 206
 207                 if (mp_opt->use_map) {
 208                         if (mp_opt->dsn64) {
 209                                 mp_opt->data_seq = get_unaligned_be64(ptr);
 210                                 ptr += 8;
 211                         } else {
 212                                 mp_opt->data_seq = get_unaligned_be32(ptr);
 213                                 ptr += 4;
 214                         }
 215
 216                         mp_opt->subflow_seq = get_unaligned_be32(ptr);
 217                         ptr += 4;
 218
 219                         mp_opt->data_len = get_unaligned_be16(ptr);
 220                         ptr += 2;
 221
 222                         if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
 223                                 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 224                                 mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
 225                                 ptr += 2;
 226                         }
 227
 228                         pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u\n",
 229                                  mp_opt->data_seq, mp_opt->subflow_seq,
 230                                  mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD),
 231                                  mp_opt->csum);
 232                 }
 233
 234                 break;
 235
 236         case MPTCPOPT_ADD_ADDR:
 237                 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 238                 if (!mp_opt->echo) {
 239                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 240                             opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 241                                 mp_opt->addr.family = AF_INET;
 242 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 243                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 244                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 245                                 mp_opt->addr.family = AF_INET6;
 246 #endif
 247                         else
 248                                 break;
 249                 } else {
 250                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 251                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 252                                 mp_opt->addr.family = AF_INET;
 253 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 254                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 255                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 256                                 mp_opt->addr.family = AF_INET6;
 257 #endif
 258                         else
 259                                 break;
 260                 }
 261
 262                 mp_opt->suboptions |= OPTION_MPTCP_ADD_ADDR;
 263                 mp_opt->addr.id = *ptr++;
 264                 mp_opt->addr.port = 0;
 265                 mp_opt->ahmac = 0;
 266                 if (mp_opt->addr.family == AF_INET) {
 267                         memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
 268                         ptr += 4;
 269                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 270                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 271                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 272                                 ptr += 2;
 273                         }
 274                 }
 275 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 276                 else {
 277                         memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16);
 278                         ptr += 16;
 279                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 280                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 281                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 282                                 ptr += 2;
 283                         }
 284                 }
 285 #endif
 286                 if (!mp_opt->echo) {
 287                         mp_opt->ahmac = get_unaligned_be64(ptr);
 288                         ptr += 8;
 289                 }
 290                 pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d\n",
 291                          (mp_opt->addr.family == AF_INET6) ? "6" : "",
 292                          mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
 293                 break;
 294
 295         case MPTCPOPT_RM_ADDR:
 296                 if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
 297                     opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
 298                         break;
 299
 300                 ptr++;
 301
 302                 mp_opt->suboptions |= OPTION_MPTCP_RM_ADDR;
 303                 mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
 304                 for (i = 0; i < mp_opt->rm_list.nr; i++)
 305                         mp_opt->rm_list.ids[i] = *ptr++;
 306                 pr_debug("RM_ADDR: rm_list_nr=%d\n", mp_opt->rm_list.nr);
 307                 break;
 308
 309         case MPTCPOPT_MP_PRIO:
 310                 if (opsize != TCPOLEN_MPTCP_PRIO)
 311                         break;
 312
 313                 mp_opt->suboptions |= OPTION_MPTCP_PRIO;
 314                 mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
 315                 pr_debug("MP_PRIO: prio=%d\n", mp_opt->backup);
 316                 break;
 317
 318         case MPTCPOPT_MP_FASTCLOSE:
 319                 if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 320                         break;
 321
 322                 ptr += 2;
 323                 mp_opt->rcvr_key = get_unaligned_be64(ptr);
 324                 ptr += 8;
 325                 mp_opt->suboptions |= OPTION_MPTCP_FASTCLOSE;
 326                 pr_debug("MP_FASTCLOSE: recv_key=%llu\n", mp_opt->rcvr_key);
 327                 break;
 328
 329         case MPTCPOPT_RST:
 330                 if (opsize != TCPOLEN_MPTCP_RST)
 331                         break;
 332
 333                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 334                         break;
 335
 336                 mp_opt->suboptions |= OPTION_MPTCP_RST;
 337                 flags = *ptr++;
 338                 mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
 339                 mp_opt->reset_reason = *ptr;
 340                 pr_debug("MP_RST: transient=%u reason=%u\n",
 341                          mp_opt->reset_transient, mp_opt->reset_reason);
 342                 break;
 343
 344         case MPTCPOPT_MP_FAIL:
 345                 if (opsize != TCPOLEN_MPTCP_FAIL)
 346                         break;
 347
 348                 ptr += 2;
 349                 mp_opt->suboptions |= OPTION_MPTCP_FAIL;
 350                 mp_opt->fail_seq = get_unaligned_be64(ptr);
 351                 pr_debug("MP_FAIL: data_seq=%llu\n", mp_opt->fail_seq);
 352                 break;
 353
 354         default:
 355                 break;
 356         }
 357 }
 358
 359 void mptcp_get_options(const struct sk_buff *skb,
 360                        struct mptcp_options_received *mp_opt)
 361 {
 362         const struct tcphdr *th = tcp_hdr(skb);
 363         const unsigned char *ptr;
 364         int length;
 365
 366         /* Ensure that casting the whole status to u32 is efficient and safe */
 367         BUILD_BUG_ON(sizeof_field(struct mptcp_options_received, status) != sizeof(u32));
 368         BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct mptcp_options_received, status),
 369                                  sizeof(u32)));
 370         *(u32 *)&mp_opt->status = 0;
 371
 372         length = (th->doff * 4) - sizeof(struct tcphdr);
 373         ptr = (const unsigned char *)(th + 1);
 374
 375         while (length > 0) {
 376                 int opcode = *ptr++;
 377                 int opsize;
 378
 379                 switch (opcode) {
 380                 case TCPOPT_EOL:
 381                         return;
 382                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 383                         length--;
 384                         continue;
 385                 default:
 386                         if (length < 2)
 387                                 return;
 388                         opsize = *ptr++;
 389                         if (opsize < 2) /* "silly options" */
 390                                 return;
 391                         if (opsize > length)
 392                                 return; /* don't parse partial options */
 393                         if (opcode == TCPOPT_MPTCP)
 394                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 395                         ptr += opsize - 2;
 396                         length -= opsize;
 397                 }
 398         }
 399 }
 400
 401 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 402                        unsigned int *size, struct mptcp_out_options *opts)
 403 {
 404         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 405
 406         /* we will use snd_isn to detect first pkt [re]transmission
 407          * in mptcp_established_options_mp()
 408          */
 409         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 410         if (subflow->request_mptcp) {
 411                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 412                 opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
 413                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 414                 *size = TCPOLEN_MPTCP_MPC_SYN;
 415                 return true;
 416         } else if (subflow->request_join) {
 417                 pr_debug("remote_token=%u, nonce=%u\n", subflow->remote_token,
 418                          subflow->local_nonce);
 419                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 420                 opts->join_id = subflow->local_id;
 421                 opts->token = subflow->remote_token;
 422                 opts->nonce = subflow->local_nonce;
 423                 opts->backup = subflow->request_bkup;
 424                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 425                 return true;
 426         }
 427         return false;
 428 }
 429
 430 static void clear_3rdack_retransmission(struct sock *sk)
 431 {
 432         struct inet_connection_sock *icsk = inet_csk(sk);
 433
 434         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 435         icsk->icsk_ack.ato = 0;
 436         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 437 }
 438
 439 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 440                                          bool snd_data_fin_enable,
 441                                          unsigned int *size,
 442                                          struct mptcp_out_options *opts)
 443 {
 444         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 445         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 446         struct mptcp_ext *mpext;
 447         unsigned int data_len;
 448         u8 len;
 449
 450         /* When skb is not available, we better over-estimate the emitted
 451          * options len. A full DSS option (28 bytes) is longer than
 452          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 453          * tell the caller to defer the estimate to
 454          * mptcp_established_options_dss(), which will reserve enough space.
 455          */
 456         if (!skb)
 457                 return false;
 458
 459         /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
 460         if (READ_ONCE(subflow->fully_established) || snd_data_fin_enable ||
 461             subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 462             sk->sk_state != TCP_ESTABLISHED)
 463                 return false;
 464
 465         if (subflow->mp_capable) {
 466                 mpext = mptcp_get_ext(skb);
 467                 data_len = mpext ? mpext->data_len : 0;
 468
 469                 /* we will check ops->data_len in mptcp_write_options() to
 470                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 471                  * TCPOLEN_MPTCP_MPC_ACK
 472                  */
 473                 opts->data_len = data_len;
 474                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 475                 opts->sndr_key = subflow->local_key;
 476                 opts->rcvr_key = subflow->remote_key;
 477                 opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 478                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 479
 480                 /* Section 3.1.
 481                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 482                  * packets that start the first subflow of an MPTCP connection,
 483                  * as well as the first packet that carries data
 484                  */
 485                 if (data_len > 0) {
 486                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 487                         if (opts->csum_reqd) {
 488                                 /* we need to propagate more info to csum the pseudo hdr */
 489                                 opts->data_seq = mpext->data_seq;
 490                                 opts->subflow_seq = mpext->subflow_seq;
 491                                 opts->csum = mpext->csum;
 492                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
 493                         }
 494                         *size = ALIGN(len, 4);
 495                 } else {
 496                         *size = TCPOLEN_MPTCP_MPC_ACK;
 497                 }
 498
 499                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d\n",
 500                          subflow, subflow->local_key, subflow->remote_key,
 501                          data_len);
 502
 503                 return true;
 504         } else if (subflow->mp_join) {
 505                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 506                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 507                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 508                 pr_debug("subflow=%p\n", subflow);
 509
 510                 /* we can use the full delegate action helper only from BH context
 511                  * If we are in process context - sk is flushing the backlog at
 512                  * socket lock release time - just set the appropriate flag, will
 513                  * be handled by the release callback
 514                  */
 515                 if (sock_owned_by_user(sk))
 516                         set_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status);
 517                 else
 518                         mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_ACK);
 519                 return true;
 520         }
 521         return false;
 522 }
 523
 524 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 525                                  struct sk_buff *skb, struct mptcp_ext *ext)
 526 {
 527         /* The write_seq value has already been incremented, so the actual
 528          * sequence number for the DATA_FIN is one less.
 529          */
 530         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 531
 532         if (!ext->use_map || !skb->len) {
 533                 /* RFC6824 requires a DSS mapping with specific values
 534                  * if DATA_FIN is set but no data payload is mapped
 535                  */
 536                 ext->data_fin = 1;
 537                 ext->use_map = 1;
 538                 ext->dsn64 = 1;
 539                 ext->data_seq = data_fin_tx_seq;
 540                 ext->subflow_seq = 0;
 541                 ext->data_len = 1;
 542         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 543                 /* If there's an existing DSS mapping and it is the
 544                  * final mapping, DATA_FIN consumes 1 additional byte of
 545                  * mapping space.
 546                  */
 547                 ext->data_fin = 1;
 548                 ext->data_len++;
 549         }
 550 }
 551
 552 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 553                                           bool snd_data_fin_enable,
 554                                           unsigned int *size,
 555                                           struct mptcp_out_options *opts)
 556 {
 557         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 558         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 559         unsigned int dss_size = 0;
 560         struct mptcp_ext *mpext;
 561         unsigned int ack_size;
 562         bool ret = false;
 563         u64 ack_seq;
 564
 565         opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 566         mpext = skb ? mptcp_get_ext(skb) : NULL;
 567
 568         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 569                 unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 570
 571                 if (mpext) {
 572                         if (opts->csum_reqd)
 573                                 map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
 574
 575                         opts->ext_copy = *mpext;
 576                 }
 577
 578                 dss_size = map_size;
 579                 if (skb && snd_data_fin_enable)
 580                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 581                 opts->suboptions = OPTION_MPTCP_DSS;
 582                 ret = true;
 583         }
 584
 585         /* passive sockets msk will set the 'can_ack' after accept(), even
 586          * if the first subflow may have the already the remote key handy
 587          */
 588         opts->ext_copy.use_ack = 0;
 589         if (!READ_ONCE(msk->can_ack)) {
 590                 *size = ALIGN(dss_size, 4);
 591                 return ret;
 592         }
 593
 594         ack_seq = READ_ONCE(msk->ack_seq);
 595         if (READ_ONCE(msk->use_64bit_ack)) {
 596                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 597                 opts->ext_copy.data_ack = ack_seq;
 598                 opts->ext_copy.ack64 = 1;
 599         } else {
 600                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 601                 opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
 602                 opts->ext_copy.ack64 = 0;
 603         }
 604         opts->ext_copy.use_ack = 1;
 605         opts->suboptions = OPTION_MPTCP_DSS;
 606
 607         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 608         if (dss_size == 0)
 609                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 610
 611         dss_size += ack_size;
 612
 613         *size = ALIGN(dss_size, 4);
 614         return true;
 615 }
 616
 617 static u64 add_addr_generate_hmac(u64 key1, u64 key2,
 618                                   struct mptcp_addr_info *addr)
 619 {
 620         u16 port = ntohs(addr->port);
 621         u8 hmac[SHA256_DIGEST_SIZE];
 622         u8 msg[19];
 623         int i = 0;
 624
 625         msg[i++] = addr->id;
 626         if (addr->family == AF_INET) {
 627                 memcpy(&msg[i], &addr->addr.s_addr, 4);
 628                 i += 4;
 629         }
 630 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 631         else if (addr->family == AF_INET6) {
 632                 memcpy(&msg[i], &addr->addr6.s6_addr, 16);
 633                 i += 16;
 634         }
 635 #endif
 636         msg[i++] = port >> 8;
 637         msg[i++] = port & 0xFF;
 638
 639         mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
 640
 641         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 642 }
 643
 644 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 645                                                unsigned int *size,
 646                                                unsigned int remaining,
 647                                                struct mptcp_out_options *opts)
 648 {
 649         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 650         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 651         bool drop_other_suboptions = false;
 652         unsigned int opt_size = *size;
 653         struct mptcp_addr_info addr;
 654         bool echo;
 655         int len;
 656
 657         /* add addr will strip the existing options, be sure to avoid breaking
 658          * MPC/MPJ handshakes
 659          */
 660         if (!mptcp_pm_should_add_signal(msk) ||
 661             (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
 662             !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &addr,
 663                     &echo, &drop_other_suboptions))
 664                 return false;
 665
 666         /*
 667          * Later on, mptcp_write_options() will enforce mutually exclusion with
 668          * DSS, bail out if such option is set and we can't drop it.
 669          */
 670         if (drop_other_suboptions)
 671                 remaining += opt_size;
 672         else if (opts->suboptions & OPTION_MPTCP_DSS)
 673                 return false;
 674
 675         len = mptcp_add_addr_len(addr.family, echo, !!addr.port);
 676         if (remaining < len)
 677                 return false;
 678
 679         *size = len;
 680         if (drop_other_suboptions) {
 681                 pr_debug("drop other suboptions\n");
 682                 opts->suboptions = 0;
 683
 684                 /* note that e.g. DSS could have written into the memory
 685                  * aliased by ahmac, we must reset the field here
 686                  * to avoid appending the hmac even for ADD_ADDR echo
 687                  * options
 688                  */
 689                 opts->ahmac = 0;
 690                 *size -= opt_size;
 691         }
 692         opts->addr = addr;
 693         opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 694         if (!echo) {
 695                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX);
 696                 opts->ahmac = add_addr_generate_hmac(READ_ONCE(msk->local_key),
 697                                                      READ_ONCE(msk->remote_key),
 698                                                      &opts->addr);
 699         } else {
 700                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADDTX);
 701         }
 702         pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d\n",
 703                  opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
 704
 705         return true;
 706 }
 707
 708 static bool mptcp_established_options_rm_addr(struct sock *sk,
 709                                               unsigned int *size,
 710                                               unsigned int remaining,
 711                                               struct mptcp_out_options *opts)
 712 {
 713         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 714         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 715         struct mptcp_rm_list rm_list;
 716         int i, len;
 717
 718         if (!mptcp_pm_should_rm_signal(msk) ||
 719             !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
 720                 return false;
 721
 722         len = mptcp_rm_addr_len(&rm_list);
 723         if (len < 0)
 724                 return false;
 725         if (remaining < len)
 726                 return false;
 727
 728         *size = len;
 729         opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 730         opts->rm_list = rm_list;
 731
 732         for (i = 0; i < opts->rm_list.nr; i++)
 733                 pr_debug("rm_list_ids[%d]=%d\n", i, opts->rm_list.ids[i]);
 734         MPTCP_ADD_STATS(sock_net(sk), MPTCP_MIB_RMADDRTX, opts->rm_list.nr);
 735         return true;
 736 }
 737
 738 static bool mptcp_established_options_mp_prio(struct sock *sk,
 739                                               unsigned int *size,
 740                                               unsigned int remaining,
 741                                               struct mptcp_out_options *opts)
 742 {
 743         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 744
 745         /* can't send MP_PRIO with MPC, as they share the same option space:
 746          * 'backup'. Also it makes no sense at all
 747          */
 748         if (!subflow->send_mp_prio || (opts->suboptions & OPTIONS_MPTCP_MPC))
 749                 return false;
 750
 751         /* account for the trailing 'nop' option */
 752         if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
 753                 return false;
 754
 755         *size = TCPOLEN_MPTCP_PRIO_ALIGN;
 756         opts->suboptions |= OPTION_MPTCP_PRIO;
 757         opts->backup = subflow->request_bkup;
 758
 759         pr_debug("prio=%d\n", opts->backup);
 760
 761         return true;
 762 }
 763
 764 static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
 765                                                    unsigned int *size,
 766                                                    unsigned int remaining,
 767                                                    struct mptcp_out_options *opts)
 768 {
 769         const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 770
 771         if (remaining < TCPOLEN_MPTCP_RST)
 772                 return false;
 773
 774         *size = TCPOLEN_MPTCP_RST;
 775         opts->suboptions |= OPTION_MPTCP_RST;
 776         opts->reset_transient = subflow->reset_transient;
 777         opts->reset_reason = subflow->reset_reason;
 778         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTTX);
 779
 780         return true;
 781 }
 782
 783 static bool mptcp_established_options_fastclose(struct sock *sk,
 784                                                 unsigned int *size,
 785                                                 unsigned int remaining,
 786                                                 struct mptcp_out_options *opts)
 787 {
 788         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 789         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 790
 791         if (likely(!subflow->send_fastclose))
 792                 return false;
 793
 794         if (remaining < TCPOLEN_MPTCP_FASTCLOSE)
 795                 return false;
 796
 797         *size = TCPOLEN_MPTCP_FASTCLOSE;
 798         opts->suboptions |= OPTION_MPTCP_FASTCLOSE;
 799         opts->rcvr_key = READ_ONCE(msk->remote_key);
 800
 801         pr_debug("FASTCLOSE key=%llu\n", opts->rcvr_key);
 802         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSETX);
 803         return true;
 804 }
 805
 806 static bool mptcp_established_options_mp_fail(struct sock *sk,
 807                                               unsigned int *size,
 808                                               unsigned int remaining,
 809                                               struct mptcp_out_options *opts)
 810 {
 811         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 812
 813         if (likely(!subflow->send_mp_fail))
 814                 return false;
 815
 816         if (remaining < TCPOLEN_MPTCP_FAIL)
 817                 return false;
 818
 819         *size = TCPOLEN_MPTCP_FAIL;
 820         opts->suboptions |= OPTION_MPTCP_FAIL;
 821         opts->fail_seq = subflow->map_seq;
 822
 823         pr_debug("MP_FAIL fail_seq=%llu\n", opts->fail_seq);
 824         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILTX);
 825
 826         return true;
 827 }
 828
 829 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 830                                unsigned int *size, unsigned int remaining,
 831                                struct mptcp_out_options *opts)
 832 {
 833         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 834         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 835         unsigned int opt_size = 0;
 836         bool snd_data_fin;
 837         bool ret = false;
 838
 839         opts->suboptions = 0;
 840
 841         if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb)))
 842                 return false;
 843
 844         if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 845                 if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
 846                     mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
 847                         *size += opt_size;
 848                         remaining -= opt_size;
 849                 }
 850                 /* MP_RST can be used with MP_FASTCLOSE and MP_FAIL if there is room */
 851                 if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
 852                         *size += opt_size;
 853                         remaining -= opt_size;
 854                 }
 855                 return true;
 856         }
 857
 858         snd_data_fin = mptcp_data_fin_enabled(msk);
 859         if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, opts))
 860                 ret = true;
 861         else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, opts)) {
 862                 unsigned int mp_fail_size;
 863
 864                 ret = true;
 865                 if (mptcp_established_options_mp_fail(sk, &mp_fail_size,
 866                                                       remaining - opt_size, opts)) {
 867                         *size += opt_size + mp_fail_size;
 868                         remaining -= opt_size - mp_fail_size;
 869                         return true;
 870                 }
 871         }
 872
 873         /* we reserved enough space for the above options, and exceeding the
 874          * TCP option space would be fatal
 875          */
 876         if (WARN_ON_ONCE(opt_size > remaining))
 877                 return false;
 878
 879         *size += opt_size;
 880         remaining -= opt_size;
 881         if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
 882                 *size += opt_size;
 883                 remaining -= opt_size;
 884                 ret = true;
 885         } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 886                 *size += opt_size;
 887                 remaining -= opt_size;
 888                 ret = true;
 889         }
 890
 891         if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
 892                 *size += opt_size;
 893                 remaining -= opt_size;
 894                 ret = true;
 895         }
 896
 897         return ret;
 898 }
 899
 900 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 901                           struct mptcp_out_options *opts)
 902 {
 903         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 904
 905         if (subflow_req->mp_capable) {
 906                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 907                 opts->sndr_key = subflow_req->local_key;
 908                 opts->csum_reqd = subflow_req->csum_reqd;
 909                 opts->allow_join_id0 = subflow_req->allow_join_id0;
 910                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 911                 pr_debug("subflow_req=%p, local_key=%llu\n",
 912                          subflow_req, subflow_req->local_key);
 913                 return true;
 914         } else if (subflow_req->mp_join) {
 915                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 916                 opts->backup = subflow_req->request_bkup;
 917                 opts->join_id = subflow_req->local_id;
 918                 opts->thmac = subflow_req->thmac;
 919                 opts->nonce = subflow_req->local_nonce;
 920                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u\n",
 921                          subflow_req, opts->backup, opts->join_id,
 922                          opts->thmac, opts->nonce);
 923                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 924                 return true;
 925         }
 926         return false;
 927 }
 928
 929 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 930                                     struct mptcp_subflow_context *subflow,
 931                                     struct sk_buff *skb,
 932                                     struct mptcp_options_received *mp_opt)
 933 {
 934         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 935          * will make the subflow fully established
 936          */
 937         if (likely(READ_ONCE(subflow->fully_established))) {
 938                 /* on passive sockets, check for 3rd ack retransmission
 939                  * note that msk is always set by subflow_syn_recv_sock()
 940                  * for mp_join subflows
 941                  */
 942                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 943                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 944                     subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) &&
 945                     !subflow->request_join)
 946                         tcp_send_ack(ssk);
 947                 goto check_notify;
 948         }
 949
 950         /* we must process OoO packets before the first subflow is fully
 951          * established. OoO packets are instead a protocol violation
 952          * for MP_JOIN subflows as the peer must not send any data
 953          * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 954          */
 955         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 956                 if (subflow->mp_join)
 957                         goto reset;
 958                 if (subflow->is_mptfo && mp_opt->suboptions & OPTION_MPTCP_MPC_ACK)
 959                         goto set_fully_established;
 960                 return subflow->mp_capable;
 961         }
 962
 963         if (subflow->remote_key_valid &&
 964             (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) ||
 965              ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) &&
 966               (!mp_opt->echo || subflow->mp_join)))) {
 967                 /* subflows are fully established as soon as we get any
 968                  * additional ack, including ADD_ADDR.
 969                  */
 970                 goto set_fully_established;
 971         }
 972
 973         /* If the first established packet does not contain MP_CAPABLE + data
 974          * then fallback to TCP. Fallback scenarios requires a reset for
 975          * MP_JOIN subflows.
 976          */
 977         if (!(mp_opt->suboptions & OPTIONS_MPTCP_MPC)) {
 978                 if (subflow->mp_join)
 979                         goto reset;
 980                 subflow->mp_capable = 0;
 981                 pr_fallback(msk);
 982                 mptcp_do_fallback(ssk);
 983                 return false;
 984         }
 985
 986         if (mp_opt->deny_join_id0)
 987                 WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 988
 989         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 990                 pr_warn_once("bogus mpc option on established client sk");
 991
 992 set_fully_established:
 993         mptcp_data_lock((struct sock *)msk);
 994         __mptcp_subflow_fully_established(msk, subflow, mp_opt);
 995         mptcp_data_unlock((struct sock *)msk);
 996
 997 check_notify:
 998         /* if the subflow is not already linked into the conn_list, we can't
 999          * notify the PM: this subflow is still on the listener queue
1000          * and the PM possibly acquiring the subflow lock could race with
1001          * the listener close
1002          */
1003         if (likely(subflow->pm_notified) || list_empty(&subflow->node))
1004                 return true;
1005
1006         subflow->pm_notified = 1;
1007         if (subflow->mp_join) {
1008                 clear_3rdack_retransmission(ssk);
1009                 mptcp_pm_subflow_established(msk);
1010         } else {
1011                 mptcp_pm_fully_established(msk, ssk);
1012         }
1013         return true;
1014
1015 reset:
1016         mptcp_subflow_reset(ssk);
1017         return false;
1018 }
1019
1020 u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
1021 {
1022         u32 old_seq32, cur_seq32;
1023
1024         old_seq32 = (u32)old_seq;
1025         cur_seq32 = (u32)cur_seq;
1026         cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
1027         if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
1028                 return cur_seq + (1LL << 32);
1029
1030         /* reverse wrap could happen, too */
1031         if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
1032                 return cur_seq - (1LL << 32);
1033         return cur_seq;
1034 }
1035
1036 static void __mptcp_snd_una_update(struct mptcp_sock *msk, u64 new_snd_una)
1037 {
1038         msk->bytes_acked += new_snd_una - msk->snd_una;
1039         WRITE_ONCE(msk->snd_una, new_snd_una);
1040 }
1041
1042 static void ack_update_msk(struct mptcp_sock *msk,
1043                            struct sock *ssk,
1044                            struct mptcp_options_received *mp_opt)
1045 {
1046         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
1047         struct sock *sk = (struct sock *)msk;
1048         u64 old_snd_una;
1049
1050         mptcp_data_lock(sk);
1051
1052         /* avoid ack expansion on update conflict, to reduce the risk of
1053          * wrongly expanding to a future ack sequence number, which is way
1054          * more dangerous than missing an ack
1055          */
1056         old_snd_una = msk->snd_una;
1057         new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
1058
1059         /* ACK for data not even sent yet? Ignore.*/
1060         if (unlikely(after64(new_snd_una, snd_nxt)))
1061                 new_snd_una = old_snd_una;
1062
1063         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
1064
1065         if (after64(new_wnd_end, msk->wnd_end))
1066                 WRITE_ONCE(msk->wnd_end, new_wnd_end);
1067
1068         /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
1069         if (after64(msk->wnd_end, snd_nxt))
1070                 __mptcp_check_push(sk, ssk);
1071
1072         if (after64(new_snd_una, old_snd_una)) {
1073                 __mptcp_snd_una_update(msk, new_snd_una);
1074                 __mptcp_data_acked(sk);
1075         }
1076         msk->last_ack_recv = tcp_jiffies32;
1077         mptcp_data_unlock(sk);
1078
1079         trace_ack_update_msk(mp_opt->data_ack,
1080                              old_snd_una, new_snd_una,
1081                              new_wnd_end, READ_ONCE(msk->wnd_end));
1082 }
1083
1084 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
1085 {
1086         /* Skip if DATA_FIN was already received.
1087          * If updating simultaneously with the recvmsg loop, values
1088          * should match. If they mismatch, the peer is misbehaving and
1089          * we will prefer the most recent information.
1090          */
1091         if (READ_ONCE(msk->rcv_data_fin))
1092                 return false;
1093
1094         WRITE_ONCE(msk->rcv_data_fin_seq,
1095                    mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1096         WRITE_ONCE(msk->rcv_data_fin, 1);
1097
1098         return true;
1099 }
1100
1101 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1102                                 struct mptcp_options_received *mp_opt)
1103 {
1104         u64 hmac = 0;
1105
1106         if (mp_opt->echo)
1107                 return true;
1108
1109         hmac = add_addr_generate_hmac(READ_ONCE(msk->remote_key),
1110                                       READ_ONCE(msk->local_key),
1111                                       &mp_opt->addr);
1112
1113         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1114                  msk, hmac, mp_opt->ahmac);
1115
1116         return hmac == mp_opt->ahmac;
1117 }
1118
1119 /* Return false if a subflow has been reset, else return true */
1120 bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1121 {
1122         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1123         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1124         struct mptcp_options_received mp_opt;
1125         struct mptcp_ext *mpext;
1126
1127         if (__mptcp_check_fallback(msk)) {
1128                 /* Keep it simple and unconditionally trigger send data cleanup and
1129                  * pending queue spooling. We will need to acquire the data lock
1130                  * for more accurate checks, and once the lock is acquired, such
1131                  * helpers are cheap.
1132                  */
1133                 mptcp_data_lock(subflow->conn);
1134                 if (sk_stream_memory_free(sk))
1135                         __mptcp_check_push(subflow->conn, sk);
1136
1137                 /* on fallback we just need to ignore the msk-level snd_una, as
1138                  * this is really plain TCP
1139                  */
1140                 __mptcp_snd_una_update(msk, READ_ONCE(msk->snd_nxt));
1141
1142                 __mptcp_data_acked(subflow->conn);
1143                 mptcp_data_unlock(subflow->conn);
1144                 return true;
1145         }
1146
1147         mptcp_get_options(skb, &mp_opt);
1148
1149         /* The subflow can be in close state only if check_fully_established()
1150          * just sent a reset. If so, tell the caller to ignore the current packet.
1151          */
1152         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1153                 return sk->sk_state != TCP_CLOSE;
1154
1155         if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
1156                 if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
1157                     READ_ONCE(msk->local_key) == mp_opt.rcvr_key) {
1158                         WRITE_ONCE(msk->rcv_fastclose, true);
1159                         mptcp_schedule_work((struct sock *)msk);
1160                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSERX);
1161                 }
1162
1163                 if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
1164                     add_addr_hmac_valid(msk, &mp_opt)) {
1165                         if (!mp_opt.echo) {
1166                                 mptcp_pm_add_addr_received(sk, &mp_opt.addr);
1167                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1168                         } else {
1169                                 mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1170                                 mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1171                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1172                         }
1173
1174                         if (mp_opt.addr.port)
1175                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1176                 }
1177
1178                 if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR)
1179                         mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1180
1181                 if (mp_opt.suboptions & OPTION_MPTCP_PRIO) {
1182                         mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1183                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1184                 }
1185
1186                 if (mp_opt.suboptions & OPTION_MPTCP_FAIL) {
1187                         mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq);
1188                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX);
1189                 }
1190
1191                 if (mp_opt.suboptions & OPTION_MPTCP_RST) {
1192                         subflow->reset_seen = 1;
1193                         subflow->reset_reason = mp_opt.reset_reason;
1194                         subflow->reset_transient = mp_opt.reset_transient;
1195                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTRX);
1196                 }
1197
1198                 if (!(mp_opt.suboptions & OPTION_MPTCP_DSS))
1199                         return true;
1200         }
1201
1202         /* we can't wait for recvmsg() to update the ack_seq, otherwise
1203          * monodirectional flows will stuck
1204          */
1205         if (mp_opt.use_ack)
1206                 ack_update_msk(msk, sk, &mp_opt);
1207
1208         /* Zero-data-length packets are dropped by the caller and not
1209          * propagated to the MPTCP layer, so the skb extension does not
1210          * need to be allocated or populated. DATA_FIN information, if
1211          * present, needs to be updated here before the skb is freed.
1212          */
1213         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1214                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1215                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64))
1216                         mptcp_schedule_work((struct sock *)msk);
1217
1218                 return true;
1219         }
1220
1221         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1222         if (!mpext)
1223                 return true;
1224
1225         memset(mpext, 0, sizeof(*mpext));
1226
1227         if (likely(mp_opt.use_map)) {
1228                 if (mp_opt.mpc_map) {
1229                         /* this is an MP_CAPABLE carrying MPTCP data
1230                          * we know this map the first chunk of data
1231                          */
1232                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1233                                              &mpext->data_seq);
1234                         mpext->data_seq++;
1235                         mpext->subflow_seq = 1;
1236                         mpext->dsn64 = 1;
1237                         mpext->mpc_map = 1;
1238                         mpext->data_fin = 0;
1239                 } else {
1240                         mpext->data_seq = mp_opt.data_seq;
1241                         mpext->subflow_seq = mp_opt.subflow_seq;
1242                         mpext->dsn64 = mp_opt.dsn64;
1243                         mpext->data_fin = mp_opt.data_fin;
1244                 }
1245                 mpext->data_len = mp_opt.data_len;
1246                 mpext->use_map = 1;
1247                 mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD);
1248
1249                 if (mpext->csum_reqd)
1250                         mpext->csum = mp_opt.csum;
1251         }
1252
1253         return true;
1254 }
1255
1256 static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
1257 {
1258         const struct sock *ssk = (const struct sock *)tp;
1259         struct mptcp_subflow_context *subflow;
1260         u64 ack_seq, rcv_wnd_old, rcv_wnd_new;
1261         struct mptcp_sock *msk;
1262         u32 new_win;
1263         u64 win;
1264
1265         subflow = mptcp_subflow_ctx(ssk);
1266         msk = mptcp_sk(subflow->conn);
1267
1268         ack_seq = READ_ONCE(msk->ack_seq);
1269         rcv_wnd_new = ack_seq + tp->rcv_wnd;
1270
1271         rcv_wnd_old = atomic64_read(&msk->rcv_wnd_sent);
1272         if (after64(rcv_wnd_new, rcv_wnd_old)) {
1273                 u64 rcv_wnd;
1274
1275                 for (;;) {
1276                         rcv_wnd = atomic64_cmpxchg(&msk->rcv_wnd_sent, rcv_wnd_old, rcv_wnd_new);
1277
1278                         if (rcv_wnd == rcv_wnd_old)
1279                                 break;
1280
1281                         rcv_wnd_old = rcv_wnd;
1282                         if (before64(rcv_wnd_new, rcv_wnd_old)) {
1283                                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);
1284                                 goto raise_win;
1285                         }
1286                         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);
1287                 }
1288                 goto update_wspace;
1289         }
1290
1291         if (rcv_wnd_new != rcv_wnd_old) {
1292 raise_win:
1293                 win = rcv_wnd_old - ack_seq;
1294                 tp->rcv_wnd = min_t(u64, win, U32_MAX);
1295                 new_win = tp->rcv_wnd;
1296
1297                 /* Make sure we do not exceed the maximum possible
1298                  * scaled window.
1299                  */
1300                 if (unlikely(th->syn))
1301                         new_win = min(new_win, 65535U) << tp->rx_opt.rcv_wscale;
1302                 if (!tp->rx_opt.rcv_wscale &&
1303                     READ_ONCE(sock_net(ssk)->ipv4.sysctl_tcp_workaround_signed_windows))
1304                         new_win = min(new_win, MAX_TCP_WINDOW);
1305                 else
1306                         new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
1307
1308                 /* RFC1323 scaling applied */
1309                 new_win >>= tp->rx_opt.rcv_wscale;
1310                 th->window = htons(new_win);
1311                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDSHARED);
1312         }
1313
1314 update_wspace:
1315         WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);
1316 }
1317
1318 __sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
1319 {
1320         struct csum_pseudo_header header;
1321         __wsum csum;
1322
1323         /* cfr RFC 8684 3.3.1.:
1324          * the data sequence number used in the pseudo-header is
1325          * always the 64-bit value, irrespective of what length is used in the
1326          * DSS option itself.
1327          */
1328         header.data_seq = cpu_to_be64(data_seq);
1329         header.subflow_seq = htonl(subflow_seq);
1330         header.data_len = htons(data_len);
1331         header.csum = 0;
1332
1333         csum = csum_partial(&header, sizeof(header), sum);
1334         return csum_fold(csum);
1335 }
1336
1337 static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext)
1338 {
1339         return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
1340                                  ~csum_unfold(mpext->csum));
1341 }
1342
1343 static void put_len_csum(u16 len, __sum16 csum, void *data)
1344 {
1345         __sum16 *sumptr = data + 2;
1346         __be16 *ptr = data;
1347
1348         put_unaligned_be16(len, ptr);
1349
1350         put_unaligned(csum, sumptr);
1351 }
1352
1353 void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
1354                          struct mptcp_out_options *opts)
1355 {
1356         const struct sock *ssk = (const struct sock *)tp;
1357         struct mptcp_subflow_context *subflow;
1358
1359         /* Which options can be used together?
1360          *
1361          * X: mutually exclusive
1362          * O: often used together
1363          * C: can be used together in some cases
1364          * P: could be used together but we prefer not to (optimisations)
1365          *
1366          *  Opt: | MPC  | MPJ  | DSS  | ADD  |  RM  | PRIO | FAIL |  FC  |
1367          * ------|------|------|------|------|------|------|------|------|
1368          *  MPC  |------|------|------|------|------|------|------|------|
1369          *  MPJ  |  X   |------|------|------|------|------|------|------|
1370          *  DSS  |  X   |  X   |------|------|------|------|------|------|
1371          *  ADD  |  X   |  X   |  P   |------|------|------|------|------|
1372          *  RM   |  C   |  C   |  C   |  P   |------|------|------|------|
1373          *  PRIO |  X   |  C   |  C   |  C   |  C   |------|------|------|
1374          *  FAIL |  X   |  X   |  C   |  X   |  X   |  X   |------|------|
1375          *  FC   |  X   |  X   |  X   |  X   |  X   |  X   |  X   |------|
1376          *  RST  |  X   |  X   |  X   |  X   |  X   |  X   |  O   |  O   |
1377          * ------|------|------|------|------|------|------|------|------|
1378          *
1379          * The same applies in mptcp_established_options() function.
1380          */
1381         if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
1382                 struct mptcp_ext *mpext = &opts->ext_copy;
1383                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1384                 u8 flags = 0;
1385
1386                 if (mpext->use_ack) {
1387                         flags = MPTCP_DSS_HAS_ACK;
1388                         if (mpext->ack64) {
1389                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1390                                 flags |= MPTCP_DSS_ACK64;
1391                         } else {
1392                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1393                         }
1394                 }
1395
1396                 if (mpext->use_map) {
1397                         len += TCPOLEN_MPTCP_DSS_MAP64;
1398
1399                         /* Use only 64-bit mapping flags for now, add
1400                          * support for optional 32-bit mappings later.
1401                          */
1402                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1403                         if (mpext->data_fin)
1404                                 flags |= MPTCP_DSS_DATA_FIN;
1405
1406                         if (opts->csum_reqd)
1407                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1408                 }
1409
1410                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1411
1412                 if (mpext->use_ack) {
1413                         if (mpext->ack64) {
1414                                 put_unaligned_be64(mpext->data_ack, ptr);
1415                                 ptr += 2;
1416                         } else {
1417                                 put_unaligned_be32(mpext->data_ack32, ptr);
1418                                 ptr += 1;
1419                         }
1420                 }
1421
1422                 if (mpext->use_map) {
1423                         put_unaligned_be64(mpext->data_seq, ptr);
1424                         ptr += 2;
1425                         put_unaligned_be32(mpext->subflow_seq, ptr);
1426                         ptr += 1;
1427                         if (opts->csum_reqd) {
1428                                 /* data_len == 0 is reserved for the infinite mapping,
1429                                  * the checksum will also be set to 0.
1430                                  */
1431                                 put_len_csum(mpext->data_len,
1432                                              (mpext->data_len ? mptcp_make_csum(mpext) : 0),
1433                                              ptr);
1434                         } else {
1435                                 put_unaligned_be32(mpext->data_len << 16 |
1436                                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1437                         }
1438                         ptr += 1;
1439                 }
1440
1441                 /* We might need to add MP_FAIL options in rare cases */
1442                 if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions))
1443                         goto mp_fail;
1444         } else if (OPTIONS_MPTCP_MPC & opts->suboptions) {
1445                 u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1446
1447                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1448                         len = TCPOLEN_MPTCP_MPC_SYN;
1449                 } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1450                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1451                 } else if (opts->data_len) {
1452                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1453                         if (opts->csum_reqd)
1454                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1455                 } else {
1456                         len = TCPOLEN_MPTCP_MPC_ACK;
1457                 }
1458
1459                 if (opts->csum_reqd)
1460                         flag |= MPTCP_CAP_CHECKSUM_REQD;
1461
1462                 if (!opts->allow_join_id0)
1463                         flag |= MPTCP_CAP_DENY_JOIN_ID0;
1464
1465                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1466                                       MPTCP_SUPPORTED_VERSION,
1467                                       flag);
1468
1469                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1470                     opts->suboptions))
1471                         goto mp_capable_done;
1472
1473                 put_unaligned_be64(opts->sndr_key, ptr);
1474                 ptr += 2;
1475                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1476                         goto mp_capable_done;
1477
1478                 put_unaligned_be64(opts->rcvr_key, ptr);
1479                 ptr += 2;
1480                 if (!opts->data_len)
1481                         goto mp_capable_done;
1482
1483                 if (opts->csum_reqd) {
1484                         put_len_csum(opts->data_len,
1485                                      __mptcp_make_csum(opts->data_seq,
1486                                                        opts->subflow_seq,
1487                                                        opts->data_len,
1488                                                        ~csum_unfold(opts->csum)),
1489                                      ptr);
1490                 } else {
1491                         put_unaligned_be32(opts->data_len << 16 |
1492                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1493                 }
1494                 ptr += 1;
1495
1496                 /* MPC is additionally mutually exclusive with MP_PRIO */
1497                 goto mp_capable_done;
1498         } else if (OPTIONS_MPTCP_MPJ & opts->suboptions) {
1499                 if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1500                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1501                                               TCPOLEN_MPTCP_MPJ_SYN,
1502                                               opts->backup, opts->join_id);
1503                         put_unaligned_be32(opts->token, ptr);
1504                         ptr += 1;
1505                         put_unaligned_be32(opts->nonce, ptr);
1506                         ptr += 1;
1507                 } else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1508                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1509                                               TCPOLEN_MPTCP_MPJ_SYNACK,
1510                                               opts->backup, opts->join_id);
1511                         put_unaligned_be64(opts->thmac, ptr);
1512                         ptr += 2;
1513                         put_unaligned_be32(opts->nonce, ptr);
1514                         ptr += 1;
1515                 } else {
1516                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1517                                               TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1518                         memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1519                         ptr += 5;
1520                 }
1521         } else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1522                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1523                 u8 echo = MPTCP_ADDR_ECHO;
1524
1525 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1526                 if (opts->addr.family == AF_INET6)
1527                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1528 #endif
1529
1530                 if (opts->addr.port)
1531                         len += TCPOLEN_MPTCP_PORT_LEN;
1532
1533                 if (opts->ahmac) {
1534                         len += sizeof(opts->ahmac);
1535                         echo = 0;
1536                 }
1537
1538                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1539                                       len, echo, opts->addr.id);
1540                 if (opts->addr.family == AF_INET) {
1541                         memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1542                         ptr += 1;
1543                 }
1544 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1545                 else if (opts->addr.family == AF_INET6) {
1546                         memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1547                         ptr += 4;
1548                 }
1549 #endif
1550
1551                 if (!opts->addr.port) {
1552                         if (opts->ahmac) {
1553                                 put_unaligned_be64(opts->ahmac, ptr);
1554                                 ptr += 2;
1555                         }
1556                 } else {
1557                         u16 port = ntohs(opts->addr.port);
1558
1559                         if (opts->ahmac) {
1560                                 u8 *bptr = (u8 *)ptr;
1561
1562                                 put_unaligned_be16(port, bptr);
1563                                 bptr += 2;
1564                                 put_unaligned_be64(opts->ahmac, bptr);
1565                                 bptr += 8;
1566                                 put_unaligned_be16(TCPOPT_NOP << 8 |
1567                                                    TCPOPT_NOP, bptr);
1568
1569                                 ptr += 3;
1570                         } else {
1571                                 put_unaligned_be32(port << 16 |
1572                                                    TCPOPT_NOP << 8 |
1573                                                    TCPOPT_NOP, ptr);
1574                                 ptr += 1;
1575                         }
1576                 }
1577         } else if (unlikely(OPTION_MPTCP_FASTCLOSE & opts->suboptions)) {
1578                 /* FASTCLOSE is mutually exclusive with others except RST */
1579                 *ptr++ = mptcp_option(MPTCPOPT_MP_FASTCLOSE,
1580                                       TCPOLEN_MPTCP_FASTCLOSE,
1581                                       0, 0);
1582                 put_unaligned_be64(opts->rcvr_key, ptr);
1583                 ptr += 2;
1584
1585                 if (OPTION_MPTCP_RST & opts->suboptions)
1586                         goto mp_rst;
1587                 return;
1588         } else if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) {
1589 mp_fail:
1590                 /* MP_FAIL is mutually exclusive with others except RST */
1591                 subflow = mptcp_subflow_ctx(ssk);
1592                 subflow->send_mp_fail = 0;
1593
1594                 *ptr++ = mptcp_option(MPTCPOPT_MP_FAIL,
1595                                       TCPOLEN_MPTCP_FAIL,
1596                                       0, 0);
1597                 put_unaligned_be64(opts->fail_seq, ptr);
1598                 ptr += 2;
1599
1600                 if (OPTION_MPTCP_RST & opts->suboptions)
1601                         goto mp_rst;
1602                 return;
1603         } else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
1604 mp_rst:
1605                 *ptr++ = mptcp_option(MPTCPOPT_RST,
1606                                       TCPOLEN_MPTCP_RST,
1607                                       opts->reset_transient,
1608                                       opts->reset_reason);
1609                 return;
1610         }
1611
1612         if (OPTION_MPTCP_PRIO & opts->suboptions) {
1613                 subflow = mptcp_subflow_ctx(ssk);
1614                 subflow->send_mp_prio = 0;
1615
1616                 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1617                                       TCPOLEN_MPTCP_PRIO,
1618                                       opts->backup, TCPOPT_NOP);
1619
1620                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPPRIOTX);
1621         }
1622
1623 mp_capable_done:
1624         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1625                 u8 i = 1;
1626
1627                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1628                                       TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1629                                       0, opts->rm_list.ids[0]);
1630
1631                 while (i < opts->rm_list.nr) {
1632                         u8 id1, id2, id3, id4;
1633
1634                         id1 = opts->rm_list.ids[i];
1635                         id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1636                         id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1637                         id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1638                         put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1639                         ptr += 1;
1640                         i += 4;
1641                 }
1642         }
1643
1644         if (tp)
1645                 mptcp_set_rwin(tp, th);
1646 }
1647
1648 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1649 {
1650         const struct mptcp_ext *ext = mptcp_get_ext(skb);
1651         u8 flags, reason;
1652
1653         if (ext) {
1654                 flags = ext->reset_transient;
1655                 reason = ext->reset_reason;
1656
1657                 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1658                                     flags, reason);
1659         }
1660
1661         return htonl(0u);
1662 }
1663 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);