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 static bool mptcp_cap_flag_sha256(u8 flags)
  17 {
  18         return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
  19 }
  20
  21 static void mptcp_parse_option(const struct sk_buff *skb,
  22                                const unsigned char *ptr, int opsize,
  23                                struct mptcp_options_received *mp_opt)
  24 {
  25         u8 subtype = *ptr >> 4;
  26         int expected_opsize;
  27         u8 version;
  28         u8 flags;
  29
  30         switch (subtype) {
  31         case MPTCPOPT_MP_CAPABLE:
  32                 /* strict size checking */
  33                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
  34                         if (skb->len > tcp_hdr(skb)->doff << 2)
  35                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
  36                         else
  37                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
  38                 } else {
  39                         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)
  40                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
  41                         else
  42                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
  43                 }
  44                 if (opsize != expected_opsize)
  45                         break;
  46
  47                 /* try to be gentle vs future versions on the initial syn */
  48                 version = *ptr++ & MPTCP_VERSION_MASK;
  49                 if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
  50                         if (version != MPTCP_SUPPORTED_VERSION)
  51                                 break;
  52                 } else if (version < MPTCP_SUPPORTED_VERSION) {
  53                         break;
  54                 }
  55
  56                 flags = *ptr++;
  57                 if (!mptcp_cap_flag_sha256(flags) ||
  58                     (flags & MPTCP_CAP_EXTENSIBILITY))
  59                         break;
  60
  61                 /* RFC 6824, Section 3.1:
  62                  * "For the Checksum Required bit (labeled "A"), if either
  63                  * host requires the use of checksums, checksums MUST be used.
  64                  * In other words, the only way for checksums not to be used
  65                  * is if both hosts in their SYNs set A=0."
  66                  *
  67                  * Section 3.3.0:
  68                  * "If a checksum is not present when its use has been
  69                  * negotiated, the receiver MUST close the subflow with a RST as
  70                  * it is considered broken."
  71                  *
  72                  * We don't implement DSS checksum - fall back to TCP.
  73                  */
  74                 if (flags & MPTCP_CAP_CHECKSUM_REQD)
  75                         break;
  76
  77                 mp_opt->mp_capable = 1;
  78                 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
  79                         mp_opt->sndr_key = get_unaligned_be64(ptr);
  80                         ptr += 8;
  81                 }
  82                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
  83                         mp_opt->rcvr_key = get_unaligned_be64(ptr);
  84                         ptr += 8;
  85                 }
  86                 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA) {
  87                         /* Section 3.1.:
  88                          * "the data parameters in a MP_CAPABLE are semantically
  89                          * equivalent to those in a DSS option and can be used
  90                          * interchangeably."
  91                          */
  92                         mp_opt->dss = 1;
  93                         mp_opt->use_map = 1;
  94                         mp_opt->mpc_map = 1;
  95                         mp_opt->data_len = get_unaligned_be16(ptr);
  96                         ptr += 2;
  97                 }
  98                 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d",
  99                          version, flags, opsize, mp_opt->sndr_key,
 100                          mp_opt->rcvr_key, mp_opt->data_len);
 101                 break;
 102
 103         case MPTCPOPT_MP_JOIN:
 104                 mp_opt->mp_join = 1;
 105                 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 106                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 107                         mp_opt->join_id = *ptr++;
 108                         mp_opt->token = get_unaligned_be32(ptr);
 109                         ptr += 4;
 110                         mp_opt->nonce = get_unaligned_be32(ptr);
 111                         ptr += 4;
 112                         pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
 113                                  mp_opt->backup, mp_opt->join_id,
 114                                  mp_opt->token, mp_opt->nonce);
 115                 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
 116                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 117                         mp_opt->join_id = *ptr++;
 118                         mp_opt->thmac = get_unaligned_be64(ptr);
 119                         ptr += 8;
 120                         mp_opt->nonce = get_unaligned_be32(ptr);
 121                         ptr += 4;
 122                         pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
 123                                  mp_opt->backup, mp_opt->join_id,
 124                                  mp_opt->thmac, mp_opt->nonce);
 125                 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 126                         ptr += 2;
 127                         memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 128                         pr_debug("MP_JOIN hmac");
 129                 } else {
 130                         pr_warn("MP_JOIN bad option size");
 131                         mp_opt->mp_join = 0;
 132                 }
 133                 break;
 134
 135         case MPTCPOPT_DSS:
 136                 pr_debug("DSS");
 137                 ptr++;
 138
 139                 /* we must clear 'mpc_map' be able to detect MP_CAPABLE
 140                  * map vs DSS map in mptcp_incoming_options(), and reconstruct
 141                  * map info accordingly
 142                  */
 143                 mp_opt->mpc_map = 0;
 144                 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 145                 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 146                 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 147                 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 148                 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 149                 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 150
 151                 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
 152                          mp_opt->data_fin, mp_opt->dsn64,
 153                          mp_opt->use_map, mp_opt->ack64,
 154                          mp_opt->use_ack);
 155
 156                 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 157
 158                 if (mp_opt->use_ack) {
 159                         if (mp_opt->ack64)
 160                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 161                         else
 162                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 163                 }
 164
 165                 if (mp_opt->use_map) {
 166                         if (mp_opt->dsn64)
 167                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 168                         else
 169                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 170                 }
 171
 172                 /* RFC 6824, Section 3.3:
 173                  * If a checksum is present, but its use had
 174                  * not been negotiated in the MP_CAPABLE handshake,
 175                  * the checksum field MUST be ignored.
 176                  */
 177                 if (opsize != expected_opsize &&
 178                     opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 179                         break;
 180
 181                 mp_opt->dss = 1;
 182
 183                 if (mp_opt->use_ack) {
 184                         if (mp_opt->ack64) {
 185                                 mp_opt->data_ack = get_unaligned_be64(ptr);
 186                                 ptr += 8;
 187                         } else {
 188                                 mp_opt->data_ack = get_unaligned_be32(ptr);
 189                                 ptr += 4;
 190                         }
 191
 192                         pr_debug("data_ack=%llu", mp_opt->data_ack);
 193                 }
 194
 195                 if (mp_opt->use_map) {
 196                         if (mp_opt->dsn64) {
 197                                 mp_opt->data_seq = get_unaligned_be64(ptr);
 198                                 ptr += 8;
 199                         } else {
 200                                 mp_opt->data_seq = get_unaligned_be32(ptr);
 201                                 ptr += 4;
 202                         }
 203
 204                         mp_opt->subflow_seq = get_unaligned_be32(ptr);
 205                         ptr += 4;
 206
 207                         mp_opt->data_len = get_unaligned_be16(ptr);
 208                         ptr += 2;
 209
 210                         pr_debug("data_seq=%llu subflow_seq=%u data_len=%u",
 211                                  mp_opt->data_seq, mp_opt->subflow_seq,
 212                                  mp_opt->data_len);
 213                 }
 214
 215                 break;
 216
 217         case MPTCPOPT_ADD_ADDR:
 218                 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 219                 if (!mp_opt->echo) {
 220                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 221                             opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 222                                 mp_opt->family = MPTCP_ADDR_IPVERSION_4;
 223 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 224                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 225                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 226                                 mp_opt->family = MPTCP_ADDR_IPVERSION_6;
 227 #endif
 228                         else
 229                                 break;
 230                 } else {
 231                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 232                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 233                                 mp_opt->family = MPTCP_ADDR_IPVERSION_4;
 234 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 235                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 236                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 237                                 mp_opt->family = MPTCP_ADDR_IPVERSION_6;
 238 #endif
 239                         else
 240                                 break;
 241                 }
 242
 243                 mp_opt->add_addr = 1;
 244                 mp_opt->addr_id = *ptr++;
 245                 if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) {
 246                         memcpy((u8 *)&mp_opt->addr.s_addr, (u8 *)ptr, 4);
 247                         ptr += 4;
 248                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 249                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 250                                 mp_opt->port = get_unaligned_be16(ptr);
 251                                 ptr += 2;
 252                         }
 253                 }
 254 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 255                 else {
 256                         memcpy(mp_opt->addr6.s6_addr, (u8 *)ptr, 16);
 257                         ptr += 16;
 258                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 259                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 260                                 mp_opt->port = get_unaligned_be16(ptr);
 261                                 ptr += 2;
 262                         }
 263                 }
 264 #endif
 265                 if (!mp_opt->echo) {
 266                         mp_opt->ahmac = get_unaligned_be64(ptr);
 267                         ptr += 8;
 268                 }
 269                 pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d",
 270                          (mp_opt->family == MPTCP_ADDR_IPVERSION_6) ? "6" : "",
 271                          mp_opt->addr_id, mp_opt->ahmac, mp_opt->echo, mp_opt->port);
 272                 break;
 273
 274         case MPTCPOPT_RM_ADDR:
 275                 if (opsize != TCPOLEN_MPTCP_RM_ADDR_BASE)
 276                         break;
 277
 278                 ptr++;
 279
 280                 mp_opt->rm_addr = 1;
 281                 mp_opt->rm_id = *ptr++;
 282                 pr_debug("RM_ADDR: id=%d", mp_opt->rm_id);
 283                 break;
 284
 285         case MPTCPOPT_MP_PRIO:
 286                 if (opsize != TCPOLEN_MPTCP_PRIO)
 287                         break;
 288
 289                 mp_opt->mp_prio = 1;
 290                 mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
 291                 pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
 292                 break;
 293
 294         case MPTCPOPT_MP_FASTCLOSE:
 295                 if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 296                         break;
 297
 298                 ptr += 2;
 299                 mp_opt->rcvr_key = get_unaligned_be64(ptr);
 300                 ptr += 8;
 301                 mp_opt->fastclose = 1;
 302                 break;
 303
 304         default:
 305                 break;
 306         }
 307 }
 308
 309 void mptcp_get_options(const struct sk_buff *skb,
 310                        struct mptcp_options_received *mp_opt)
 311 {
 312         const struct tcphdr *th = tcp_hdr(skb);
 313         const unsigned char *ptr;
 314         int length;
 315
 316         /* initialize option status */
 317         mp_opt->mp_capable = 0;
 318         mp_opt->mp_join = 0;
 319         mp_opt->add_addr = 0;
 320         mp_opt->ahmac = 0;
 321         mp_opt->fastclose = 0;
 322         mp_opt->port = 0;
 323         mp_opt->rm_addr = 0;
 324         mp_opt->dss = 0;
 325         mp_opt->mp_prio = 0;
 326
 327         length = (th->doff * 4) - sizeof(struct tcphdr);
 328         ptr = (const unsigned char *)(th + 1);
 329
 330         while (length > 0) {
 331                 int opcode = *ptr++;
 332                 int opsize;
 333
 334                 switch (opcode) {
 335                 case TCPOPT_EOL:
 336                         return;
 337                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 338                         length--;
 339                         continue;
 340                 default:
 341                         opsize = *ptr++;
 342                         if (opsize < 2) /* "silly options" */
 343                                 return;
 344                         if (opsize > length)
 345                                 return; /* don't parse partial options */
 346                         if (opcode == TCPOPT_MPTCP)
 347                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 348                         ptr += opsize - 2;
 349                         length -= opsize;
 350                 }
 351         }
 352 }
 353
 354 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 355                        unsigned int *size, struct mptcp_out_options *opts)
 356 {
 357         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 358
 359         /* we will use snd_isn to detect first pkt [re]transmission
 360          * in mptcp_established_options_mp()
 361          */
 362         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 363         if (subflow->request_mptcp) {
 364                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 365                 *size = TCPOLEN_MPTCP_MPC_SYN;
 366                 return true;
 367         } else if (subflow->request_join) {
 368                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 369                          subflow->local_nonce);
 370                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 371                 opts->join_id = subflow->local_id;
 372                 opts->token = subflow->remote_token;
 373                 opts->nonce = subflow->local_nonce;
 374                 opts->backup = subflow->request_bkup;
 375                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 376                 return true;
 377         }
 378         return false;
 379 }
 380
 381 /* MP_JOIN client subflow must wait for 4th ack before sending any data:
 382  * TCP can't schedule delack timer before the subflow is fully established.
 383  * MPTCP uses the delack timer to do 3rd ack retransmissions
 384  */
 385 static void schedule_3rdack_retransmission(struct sock *sk)
 386 {
 387         struct inet_connection_sock *icsk = inet_csk(sk);
 388         struct tcp_sock *tp = tcp_sk(sk);
 389         unsigned long timeout;
 390
 391         /* reschedule with a timeout above RTT, as we must look only for drop */
 392         if (tp->srtt_us)
 393                 timeout = tp->srtt_us << 1;
 394         else
 395                 timeout = TCP_TIMEOUT_INIT;
 396
 397         WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 398         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 399         icsk->icsk_ack.timeout = timeout;
 400         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 401 }
 402
 403 static void clear_3rdack_retransmission(struct sock *sk)
 404 {
 405         struct inet_connection_sock *icsk = inet_csk(sk);
 406
 407         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 408         icsk->icsk_ack.timeout = 0;
 409         icsk->icsk_ack.ato = 0;
 410         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 411 }
 412
 413 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 414                                          bool snd_data_fin_enable,
 415                                          unsigned int *size,
 416                                          unsigned int remaining,
 417                                          struct mptcp_out_options *opts)
 418 {
 419         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 420         struct mptcp_ext *mpext;
 421         unsigned int data_len;
 422
 423         /* When skb is not available, we better over-estimate the emitted
 424          * options len. A full DSS option (28 bytes) is longer than
 425          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 426          * tell the caller to defer the estimate to
 427          * mptcp_established_options_dss(), which will reserve enough space.
 428          */
 429         if (!skb)
 430                 return false;
 431
 432         /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
 433         if (subflow->fully_established || snd_data_fin_enable ||
 434             subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 435             sk->sk_state != TCP_ESTABLISHED)
 436                 return false;
 437
 438         if (subflow->mp_capable) {
 439                 mpext = mptcp_get_ext(skb);
 440                 data_len = mpext ? mpext->data_len : 0;
 441
 442                 /* we will check ext_copy.data_len in mptcp_write_options() to
 443                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 444                  * TCPOLEN_MPTCP_MPC_ACK
 445                  */
 446                 opts->ext_copy.data_len = data_len;
 447                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 448                 opts->sndr_key = subflow->local_key;
 449                 opts->rcvr_key = subflow->remote_key;
 450
 451                 /* Section 3.1.
 452                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 453                  * packets that start the first subflow of an MPTCP connection,
 454                  * as well as the first packet that carries data
 455                  */
 456                 if (data_len > 0)
 457                         *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
 458                 else
 459                         *size = TCPOLEN_MPTCP_MPC_ACK;
 460
 461                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 462                          subflow, subflow->local_key, subflow->remote_key,
 463                          data_len);
 464
 465                 return true;
 466         } else if (subflow->mp_join) {
 467                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 468                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 469                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 470                 pr_debug("subflow=%p", subflow);
 471
 472                 schedule_3rdack_retransmission(sk);
 473                 return true;
 474         }
 475         return false;
 476 }
 477
 478 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 479                                  struct sk_buff *skb, struct mptcp_ext *ext)
 480 {
 481         /* The write_seq value has already been incremented, so the actual
 482          * sequence number for the DATA_FIN is one less.
 483          */
 484         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 485
 486         if (!ext->use_map || !skb->len) {
 487                 /* RFC6824 requires a DSS mapping with specific values
 488                  * if DATA_FIN is set but no data payload is mapped
 489                  */
 490                 ext->data_fin = 1;
 491                 ext->use_map = 1;
 492                 ext->dsn64 = 1;
 493                 ext->data_seq = data_fin_tx_seq;
 494                 ext->subflow_seq = 0;
 495                 ext->data_len = 1;
 496         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 497                 /* If there's an existing DSS mapping and it is the
 498                  * final mapping, DATA_FIN consumes 1 additional byte of
 499                  * mapping space.
 500                  */
 501                 ext->data_fin = 1;
 502                 ext->data_len++;
 503         }
 504 }
 505
 506 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 507                                           bool snd_data_fin_enable,
 508                                           unsigned int *size,
 509                                           unsigned int remaining,
 510                                           struct mptcp_out_options *opts)
 511 {
 512         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 513         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 514         unsigned int dss_size = 0;
 515         struct mptcp_ext *mpext;
 516         unsigned int ack_size;
 517         bool ret = false;
 518         u64 ack_seq;
 519
 520         mpext = skb ? mptcp_get_ext(skb) : NULL;
 521
 522         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 523                 unsigned int map_size;
 524
 525                 map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 526
 527                 remaining -= map_size;
 528                 dss_size = map_size;
 529                 if (mpext)
 530                         opts->ext_copy = *mpext;
 531
 532                 if (skb && snd_data_fin_enable)
 533                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 534                 ret = true;
 535         }
 536
 537         /* passive sockets msk will set the 'can_ack' after accept(), even
 538          * if the first subflow may have the already the remote key handy
 539          */
 540         opts->ext_copy.use_ack = 0;
 541         if (!READ_ONCE(msk->can_ack)) {
 542                 *size = ALIGN(dss_size, 4);
 543                 return ret;
 544         }
 545
 546         ack_seq = READ_ONCE(msk->ack_seq);
 547         if (READ_ONCE(msk->use_64bit_ack)) {
 548                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 549                 opts->ext_copy.data_ack = ack_seq;
 550                 opts->ext_copy.ack64 = 1;
 551         } else {
 552                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 553                 opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
 554                 opts->ext_copy.ack64 = 0;
 555         }
 556         opts->ext_copy.use_ack = 1;
 557         WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 558
 559         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 560         if (dss_size == 0)
 561                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 562
 563         dss_size += ack_size;
 564
 565         *size = ALIGN(dss_size, 4);
 566         return true;
 567 }
 568
 569 static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 570                                   struct in_addr *addr, u16 port)
 571 {
 572         u8 hmac[SHA256_DIGEST_SIZE];
 573         u8 msg[7];
 574
 575         msg[0] = addr_id;
 576         memcpy(&msg[1], &addr->s_addr, 4);
 577         msg[5] = port >> 8;
 578         msg[6] = port & 0xFF;
 579
 580         mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac);
 581
 582         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 583 }
 584
 585 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 586 static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 587                                    struct in6_addr *addr, u16 port)
 588 {
 589         u8 hmac[SHA256_DIGEST_SIZE];
 590         u8 msg[19];
 591
 592         msg[0] = addr_id;
 593         memcpy(&msg[1], &addr->s6_addr, 16);
 594         msg[17] = port >> 8;
 595         msg[18] = port & 0xFF;
 596
 597         mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac);
 598
 599         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 600 }
 601 #endif
 602
 603 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 604                                                unsigned int *size,
 605                                                unsigned int remaining,
 606                                                struct mptcp_out_options *opts)
 607 {
 608         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 609         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 610         bool drop_other_suboptions = false;
 611         unsigned int opt_size = *size;
 612         struct mptcp_addr_info saddr;
 613         bool echo;
 614         bool port;
 615         int len;
 616
 617         if ((mptcp_pm_should_add_signal_ipv6(msk) ||
 618              mptcp_pm_should_add_signal_port(msk)) &&
 619             skb && skb_is_tcp_pure_ack(skb)) {
 620                 pr_debug("drop other suboptions");
 621                 opts->suboptions = 0;
 622                 opts->ext_copy.use_ack = 0;
 623                 opts->ext_copy.use_map = 0;
 624                 remaining += opt_size;
 625                 drop_other_suboptions = true;
 626         }
 627
 628         if (!mptcp_pm_should_add_signal(msk) ||
 629             !(mptcp_pm_add_addr_signal(msk, remaining, &saddr, &echo, &port)))
 630                 return false;
 631
 632         len = mptcp_add_addr_len(saddr.family, echo, port);
 633         if (remaining < len)
 634                 return false;
 635
 636         *size = len;
 637         if (drop_other_suboptions)
 638                 *size -= opt_size;
 639         opts->addr_id = saddr.id;
 640         if (port)
 641                 opts->port = ntohs(saddr.port);
 642         if (saddr.family == AF_INET) {
 643                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 644                 opts->addr = saddr.addr;
 645                 if (!echo) {
 646                         opts->ahmac = add_addr_generate_hmac(msk->local_key,
 647                                                              msk->remote_key,
 648                                                              opts->addr_id,
 649                                                              &opts->addr,
 650                                                              opts->port);
 651                 }
 652         }
 653 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 654         else if (saddr.family == AF_INET6) {
 655                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR6;
 656                 opts->addr6 = saddr.addr6;
 657                 if (!echo) {
 658                         opts->ahmac = add_addr6_generate_hmac(msk->local_key,
 659                                                               msk->remote_key,
 660                                                               opts->addr_id,
 661                                                               &opts->addr6,
 662                                                               opts->port);
 663                 }
 664         }
 665 #endif
 666         pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d",
 667                  opts->addr_id, opts->ahmac, echo, opts->port);
 668
 669         return true;
 670 }
 671
 672 static bool mptcp_established_options_rm_addr(struct sock *sk,
 673                                               unsigned int *size,
 674                                               unsigned int remaining,
 675                                               struct mptcp_out_options *opts)
 676 {
 677         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 678         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 679         u8 rm_id;
 680
 681         if (!mptcp_pm_should_rm_signal(msk) ||
 682             !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_id)))
 683                 return false;
 684
 685         if (remaining < TCPOLEN_MPTCP_RM_ADDR_BASE)
 686                 return false;
 687
 688         *size = TCPOLEN_MPTCP_RM_ADDR_BASE;
 689         opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 690         opts->rm_id = rm_id;
 691
 692         pr_debug("rm_id=%d", opts->rm_id);
 693
 694         return true;
 695 }
 696
 697 static bool mptcp_established_options_mp_prio(struct sock *sk,
 698                                               unsigned int *size,
 699                                               unsigned int remaining,
 700                                               struct mptcp_out_options *opts)
 701 {
 702         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 703
 704         if (!subflow->send_mp_prio)
 705                 return false;
 706
 707         /* account for the trailing 'nop' option */
 708         if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
 709                 return false;
 710
 711         *size = TCPOLEN_MPTCP_PRIO_ALIGN;
 712         opts->suboptions |= OPTION_MPTCP_PRIO;
 713         opts->backup = subflow->request_bkup;
 714
 715         pr_debug("prio=%d", opts->backup);
 716
 717         return true;
 718 }
 719
 720 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 721                                unsigned int *size, unsigned int remaining,
 722                                struct mptcp_out_options *opts)
 723 {
 724         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 725         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 726         unsigned int opt_size = 0;
 727         bool snd_data_fin;
 728         bool ret = false;
 729
 730         opts->suboptions = 0;
 731
 732         if (unlikely(__mptcp_check_fallback(msk)))
 733                 return false;
 734
 735         /* prevent adding of any MPTCP related options on reset packet
 736          * until we support MP_TCPRST/MP_FASTCLOSE
 737          */
 738         if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 739                 return false;
 740
 741         snd_data_fin = mptcp_data_fin_enabled(msk);
 742         if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 743                 ret = true;
 744         else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 745                 ret = true;
 746
 747         /* we reserved enough space for the above options, and exceeding the
 748          * TCP option space would be fatal
 749          */
 750         if (WARN_ON_ONCE(opt_size > remaining))
 751                 return false;
 752
 753         *size += opt_size;
 754         remaining -= opt_size;
 755         if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
 756                 *size += opt_size;
 757                 remaining -= opt_size;
 758                 ret = true;
 759         } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 760                 *size += opt_size;
 761                 remaining -= opt_size;
 762                 ret = true;
 763         }
 764
 765         if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
 766                 *size += opt_size;
 767                 remaining -= opt_size;
 768                 ret = true;
 769         }
 770
 771         return ret;
 772 }
 773
 774 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 775                           struct mptcp_out_options *opts)
 776 {
 777         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 778
 779         if (subflow_req->mp_capable) {
 780                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 781                 opts->sndr_key = subflow_req->local_key;
 782                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 783                 pr_debug("subflow_req=%p, local_key=%llu",
 784                          subflow_req, subflow_req->local_key);
 785                 return true;
 786         } else if (subflow_req->mp_join) {
 787                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 788                 opts->backup = subflow_req->backup;
 789                 opts->join_id = subflow_req->local_id;
 790                 opts->thmac = subflow_req->thmac;
 791                 opts->nonce = subflow_req->local_nonce;
 792                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 793                          subflow_req, opts->backup, opts->join_id,
 794                          opts->thmac, opts->nonce);
 795                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 796                 return true;
 797         }
 798         return false;
 799 }
 800
 801 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 802                                     struct mptcp_subflow_context *subflow,
 803                                     struct sk_buff *skb,
 804                                     struct mptcp_options_received *mp_opt)
 805 {
 806         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 807          * will make the subflow fully established
 808          */
 809         if (likely(subflow->fully_established)) {
 810                 /* on passive sockets, check for 3rd ack retransmission
 811                  * note that msk is always set by subflow_syn_recv_sock()
 812                  * for mp_join subflows
 813                  */
 814                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 815                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 816                     subflow->mp_join && mp_opt->mp_join &&
 817                     READ_ONCE(msk->pm.server_side))
 818                         tcp_send_ack(ssk);
 819                 goto fully_established;
 820         }
 821
 822         /* we must process OoO packets before the first subflow is fully
 823          * established. OoO packets are instead a protocol violation
 824          * for MP_JOIN subflows as the peer must not send any data
 825          * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 826          */
 827         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 828                 if (subflow->mp_join)
 829                         goto reset;
 830                 return subflow->mp_capable;
 831         }
 832
 833         if (mp_opt->dss && mp_opt->use_ack) {
 834                 /* subflows are fully established as soon as we get any
 835                  * additional ack.
 836                  */
 837                 subflow->fully_established = 1;
 838                 WRITE_ONCE(msk->fully_established, true);
 839                 goto fully_established;
 840         }
 841
 842         if (mp_opt->add_addr) {
 843                 WRITE_ONCE(msk->fully_established, true);
 844                 return true;
 845         }
 846
 847         /* If the first established packet does not contain MP_CAPABLE + data
 848          * then fallback to TCP. Fallback scenarios requires a reset for
 849          * MP_JOIN subflows.
 850          */
 851         if (!mp_opt->mp_capable) {
 852                 if (subflow->mp_join)
 853                         goto reset;
 854                 subflow->mp_capable = 0;
 855                 pr_fallback(msk);
 856                 __mptcp_do_fallback(msk);
 857                 return false;
 858         }
 859
 860         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 861                 pr_warn_once("bogus mpc option on established client sk");
 862         mptcp_subflow_fully_established(subflow, mp_opt);
 863
 864 fully_established:
 865         /* if the subflow is not already linked into the conn_list, we can't
 866          * notify the PM: this subflow is still on the listener queue
 867          * and the PM possibly acquiring the subflow lock could race with
 868          * the listener close
 869          */
 870         if (likely(subflow->pm_notified) || list_empty(&subflow->node))
 871                 return true;
 872
 873         subflow->pm_notified = 1;
 874         if (subflow->mp_join) {
 875                 clear_3rdack_retransmission(ssk);
 876                 mptcp_pm_subflow_established(msk, subflow);
 877         } else {
 878                 mptcp_pm_fully_established(msk, ssk, GFP_ATOMIC);
 879         }
 880         return true;
 881
 882 reset:
 883         mptcp_subflow_reset(ssk);
 884         return false;
 885 }
 886
 887 static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)
 888 {
 889         u32 old_ack32, cur_ack32;
 890
 891         if (use_64bit)
 892                 return cur_ack;
 893
 894         old_ack32 = (u32)old_ack;
 895         cur_ack32 = (u32)cur_ack;
 896         cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32;
 897         if (unlikely(before(cur_ack32, old_ack32)))
 898                 return cur_ack + (1LL << 32);
 899         return cur_ack;
 900 }
 901
 902 static void ack_update_msk(struct mptcp_sock *msk,
 903                            struct sock *ssk,
 904                            struct mptcp_options_received *mp_opt)
 905 {
 906         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
 907         struct sock *sk = (struct sock *)msk;
 908         u64 old_snd_una;
 909
 910         mptcp_data_lock(sk);
 911
 912         /* avoid ack expansion on update conflict, to reduce the risk of
 913          * wrongly expanding to a future ack sequence number, which is way
 914          * more dangerous than missing an ack
 915          */
 916         old_snd_una = msk->snd_una;
 917         new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 918
 919         /* ACK for data not even sent yet? Ignore. */
 920         if (after64(new_snd_una, snd_nxt))
 921                 new_snd_una = old_snd_una;
 922
 923         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
 924
 925         if (after64(new_wnd_end, msk->wnd_end))
 926                 msk->wnd_end = new_wnd_end;
 927
 928         /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
 929         if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
 930                 __mptcp_check_push(sk, ssk);
 931
 932         if (after64(new_snd_una, old_snd_una)) {
 933                 msk->snd_una = new_snd_una;
 934                 __mptcp_data_acked(sk);
 935         }
 936         mptcp_data_unlock(sk);
 937 }
 938
 939 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
 940 {
 941         /* Skip if DATA_FIN was already received.
 942          * If updating simultaneously with the recvmsg loop, values
 943          * should match. If they mismatch, the peer is misbehaving and
 944          * we will prefer the most recent information.
 945          */
 946         if (READ_ONCE(msk->rcv_data_fin) || !READ_ONCE(msk->first))
 947                 return false;
 948
 949         WRITE_ONCE(msk->rcv_data_fin_seq,
 950                    expand_ack(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
 951         WRITE_ONCE(msk->rcv_data_fin, 1);
 952
 953         return true;
 954 }
 955
 956 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
 957                                 struct mptcp_options_received *mp_opt)
 958 {
 959         u64 hmac = 0;
 960
 961         if (mp_opt->echo)
 962                 return true;
 963
 964         if (mp_opt->family == MPTCP_ADDR_IPVERSION_4)
 965                 hmac = add_addr_generate_hmac(msk->remote_key,
 966                                               msk->local_key,
 967                                               mp_opt->addr_id, &mp_opt->addr,
 968                                               mp_opt->port);
 969 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 970         else
 971                 hmac = add_addr6_generate_hmac(msk->remote_key,
 972                                                msk->local_key,
 973                                                mp_opt->addr_id, &mp_opt->addr6,
 974                                                mp_opt->port);
 975 #endif
 976
 977         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
 978                  msk, (unsigned long long)hmac,
 979                  (unsigned long long)mp_opt->ahmac);
 980
 981         return hmac == mp_opt->ahmac;
 982 }
 983
 984 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 985 {
 986         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 987         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 988         struct mptcp_options_received mp_opt;
 989         struct mptcp_ext *mpext;
 990
 991         if (__mptcp_check_fallback(msk)) {
 992                 /* Keep it simple and unconditionally trigger send data cleanup and
 993                  * pending queue spooling. We will need to acquire the data lock
 994                  * for more accurate checks, and once the lock is acquired, such
 995                  * helpers are cheap.
 996                  */
 997                 mptcp_data_lock(subflow->conn);
 998                 if (sk_stream_memory_free(sk))
 999                         __mptcp_check_push(subflow->conn, sk);
1000                 __mptcp_data_acked(subflow->conn);
1001                 mptcp_data_unlock(subflow->conn);
1002                 return;
1003         }
1004
1005         mptcp_get_options(skb, &mp_opt);
1006         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1007                 return;
1008
1009         if (mp_opt.fastclose &&
1010             msk->local_key == mp_opt.rcvr_key) {
1011                 WRITE_ONCE(msk->rcv_fastclose, true);
1012                 mptcp_schedule_work((struct sock *)msk);
1013         }
1014
1015         if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
1016                 struct mptcp_addr_info addr;
1017
1018                 addr.port = htons(mp_opt.port);
1019                 addr.id = mp_opt.addr_id;
1020                 if (mp_opt.family == MPTCP_ADDR_IPVERSION_4) {
1021                         addr.family = AF_INET;
1022                         addr.addr = mp_opt.addr;
1023                 }
1024 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1025                 else if (mp_opt.family == MPTCP_ADDR_IPVERSION_6) {
1026                         addr.family = AF_INET6;
1027                         addr.addr6 = mp_opt.addr6;
1028                 }
1029 #endif
1030                 if (!mp_opt.echo) {
1031                         mptcp_pm_add_addr_received(msk, &addr);
1032                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1033                 } else {
1034                         mptcp_pm_del_add_timer(msk, &addr);
1035                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1036                 }
1037
1038                 if (mp_opt.port)
1039                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1040
1041                 mp_opt.add_addr = 0;
1042         }
1043
1044         if (mp_opt.rm_addr) {
1045                 mptcp_pm_rm_addr_received(msk, mp_opt.rm_id);
1046                 mp_opt.rm_addr = 0;
1047         }
1048
1049         if (mp_opt.mp_prio) {
1050                 mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1051                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1052                 mp_opt.mp_prio = 0;
1053         }
1054
1055         if (!mp_opt.dss)
1056                 return;
1057
1058         /* we can't wait for recvmsg() to update the ack_seq, otherwise
1059          * monodirectional flows will stuck
1060          */
1061         if (mp_opt.use_ack)
1062                 ack_update_msk(msk, sk, &mp_opt);
1063
1064         /* Zero-data-length packets are dropped by the caller and not
1065          * propagated to the MPTCP layer, so the skb extension does not
1066          * need to be allocated or populated. DATA_FIN information, if
1067          * present, needs to be updated here before the skb is freed.
1068          */
1069         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1070                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1071                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
1072                     schedule_work(&msk->work))
1073                         sock_hold(subflow->conn);
1074
1075                 return;
1076         }
1077
1078         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1079         if (!mpext)
1080                 return;
1081
1082         memset(mpext, 0, sizeof(*mpext));
1083
1084         if (mp_opt.use_map) {
1085                 if (mp_opt.mpc_map) {
1086                         /* this is an MP_CAPABLE carrying MPTCP data
1087                          * we know this map the first chunk of data
1088                          */
1089                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1090                                              &mpext->data_seq);
1091                         mpext->data_seq++;
1092                         mpext->subflow_seq = 1;
1093                         mpext->dsn64 = 1;
1094                         mpext->mpc_map = 1;
1095                         mpext->data_fin = 0;
1096                 } else {
1097                         mpext->data_seq = mp_opt.data_seq;
1098                         mpext->subflow_seq = mp_opt.subflow_seq;
1099                         mpext->dsn64 = mp_opt.dsn64;
1100                         mpext->data_fin = mp_opt.data_fin;
1101                 }
1102                 mpext->data_len = mp_opt.data_len;
1103                 mpext->use_map = 1;
1104         }
1105 }
1106
1107 static void mptcp_set_rwin(const struct tcp_sock *tp)
1108 {
1109         const struct sock *ssk = (const struct sock *)tp;
1110         const struct mptcp_subflow_context *subflow;
1111         struct mptcp_sock *msk;
1112         u64 ack_seq;
1113
1114         subflow = mptcp_subflow_ctx(ssk);
1115         msk = mptcp_sk(subflow->conn);
1116
1117         ack_seq = READ_ONCE(msk->ack_seq) + tp->rcv_wnd;
1118
1119         if (after64(ack_seq, READ_ONCE(msk->rcv_wnd_sent)))
1120                 WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
1121 }
1122
1123 void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
1124                          struct mptcp_out_options *opts)
1125 {
1126         if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
1127              OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
1128                 u8 len;
1129
1130                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
1131                         len = TCPOLEN_MPTCP_MPC_SYN;
1132                 else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
1133                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1134                 else if (opts->ext_copy.data_len)
1135                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1136                 else
1137                         len = TCPOLEN_MPTCP_MPC_ACK;
1138
1139                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1140                                       MPTCP_SUPPORTED_VERSION,
1141                                       MPTCP_CAP_HMAC_SHA256);
1142
1143                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1144                     opts->suboptions))
1145                         goto mp_capable_done;
1146
1147                 put_unaligned_be64(opts->sndr_key, ptr);
1148                 ptr += 2;
1149                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1150                         goto mp_capable_done;
1151
1152                 put_unaligned_be64(opts->rcvr_key, ptr);
1153                 ptr += 2;
1154                 if (!opts->ext_copy.data_len)
1155                         goto mp_capable_done;
1156
1157                 put_unaligned_be32(opts->ext_copy.data_len << 16 |
1158                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1159                 ptr += 1;
1160         }
1161
1162 mp_capable_done:
1163         if ((OPTION_MPTCP_ADD_ADDR
1164 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1165              | OPTION_MPTCP_ADD_ADDR6
1166 #endif
1167             ) & opts->suboptions) {
1168                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1169                 u8 echo = MPTCP_ADDR_ECHO;
1170
1171 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1172                 if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions)
1173                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1174 #endif
1175
1176                 if (opts->port)
1177                         len += TCPOLEN_MPTCP_PORT_LEN;
1178
1179                 if (opts->ahmac) {
1180                         len += sizeof(opts->ahmac);
1181                         echo = 0;
1182                 }
1183
1184                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1185                                       len, echo, opts->addr_id);
1186                 if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1187                         memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4);
1188                         ptr += 1;
1189                 }
1190 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1191                 else if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) {
1192                         memcpy((u8 *)ptr, opts->addr6.s6_addr, 16);
1193                         ptr += 4;
1194                 }
1195 #endif
1196
1197                 if (!opts->port) {
1198                         if (opts->ahmac) {
1199                                 put_unaligned_be64(opts->ahmac, ptr);
1200                                 ptr += 2;
1201                         }
1202                 } else {
1203                         if (opts->ahmac) {
1204                                 u8 *bptr = (u8 *)ptr;
1205
1206                                 put_unaligned_be16(opts->port, bptr);
1207                                 bptr += 2;
1208                                 put_unaligned_be64(opts->ahmac, bptr);
1209                                 bptr += 8;
1210                                 put_unaligned_be16(TCPOPT_NOP << 8 |
1211                                                    TCPOPT_NOP, bptr);
1212
1213                                 ptr += 3;
1214                         } else {
1215                                 put_unaligned_be32(opts->port << 16 |
1216                                                    TCPOPT_NOP << 8 |
1217                                                    TCPOPT_NOP, ptr);
1218                                 ptr += 1;
1219                         }
1220                 }
1221         }
1222
1223         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1224                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1225                                       TCPOLEN_MPTCP_RM_ADDR_BASE,
1226                                       0, opts->rm_id);
1227         }
1228
1229         if (OPTION_MPTCP_PRIO & opts->suboptions) {
1230                 const struct sock *ssk = (const struct sock *)tp;
1231                 struct mptcp_subflow_context *subflow;
1232
1233                 subflow = mptcp_subflow_ctx(ssk);
1234                 subflow->send_mp_prio = 0;
1235
1236                 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1237                                       TCPOLEN_MPTCP_PRIO,
1238                                       opts->backup, TCPOPT_NOP);
1239         }
1240
1241         if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1242                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1243                                       TCPOLEN_MPTCP_MPJ_SYN,
1244                                       opts->backup, opts->join_id);
1245                 put_unaligned_be32(opts->token, ptr);
1246                 ptr += 1;
1247                 put_unaligned_be32(opts->nonce, ptr);
1248                 ptr += 1;
1249         }
1250
1251         if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1252                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1253                                       TCPOLEN_MPTCP_MPJ_SYNACK,
1254                                       opts->backup, opts->join_id);
1255                 put_unaligned_be64(opts->thmac, ptr);
1256                 ptr += 2;
1257                 put_unaligned_be32(opts->nonce, ptr);
1258                 ptr += 1;
1259         }
1260
1261         if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
1262                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1263                                       TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1264                 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1265                 ptr += 5;
1266         }
1267
1268         if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
1269                 struct mptcp_ext *mpext = &opts->ext_copy;
1270                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1271                 u8 flags = 0;
1272
1273                 if (mpext->use_ack) {
1274                         flags = MPTCP_DSS_HAS_ACK;
1275                         if (mpext->ack64) {
1276                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1277                                 flags |= MPTCP_DSS_ACK64;
1278                         } else {
1279                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1280                         }
1281                 }
1282
1283                 if (mpext->use_map) {
1284                         len += TCPOLEN_MPTCP_DSS_MAP64;
1285
1286                         /* Use only 64-bit mapping flags for now, add
1287                          * support for optional 32-bit mappings later.
1288                          */
1289                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1290                         if (mpext->data_fin)
1291                                 flags |= MPTCP_DSS_DATA_FIN;
1292                 }
1293
1294                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1295
1296                 if (mpext->use_ack) {
1297                         if (mpext->ack64) {
1298                                 put_unaligned_be64(mpext->data_ack, ptr);
1299                                 ptr += 2;
1300                         } else {
1301                                 put_unaligned_be32(mpext->data_ack32, ptr);
1302                                 ptr += 1;
1303                         }
1304                 }
1305
1306                 if (mpext->use_map) {
1307                         put_unaligned_be64(mpext->data_seq, ptr);
1308                         ptr += 2;
1309                         put_unaligned_be32(mpext->subflow_seq, ptr);
1310                         ptr += 1;
1311                         put_unaligned_be32(mpext->data_len << 16 |
1312                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1313                 }
1314         }
1315
1316         if (tp)
1317                 mptcp_set_rwin(tp);
1318 }