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/sha.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->port = 0;
 245                 mp_opt->addr_id = *ptr++;
 246                 pr_debug("ADD_ADDR: id=%d, echo=%d", mp_opt->addr_id, mp_opt->echo);
 247                 if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) {
 248                         memcpy((u8 *)&mp_opt->addr.s_addr, (u8 *)ptr, 4);
 249                         ptr += 4;
 250                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 251                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 252                                 mp_opt->port = get_unaligned_be16(ptr);
 253                                 ptr += 2;
 254                         }
 255                 }
 256 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 257                 else {
 258                         memcpy(mp_opt->addr6.s6_addr, (u8 *)ptr, 16);
 259                         ptr += 16;
 260                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 261                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 262                                 mp_opt->port = get_unaligned_be16(ptr);
 263                                 ptr += 2;
 264                         }
 265                 }
 266 #endif
 267                 if (!mp_opt->echo) {
 268                         mp_opt->ahmac = get_unaligned_be64(ptr);
 269                         ptr += 8;
 270                 }
 271                 break;
 272
 273         case MPTCPOPT_RM_ADDR:
 274                 if (opsize != TCPOLEN_MPTCP_RM_ADDR_BASE)
 275                         break;
 276
 277                 ptr++;
 278
 279                 mp_opt->rm_addr = 1;
 280                 mp_opt->rm_id = *ptr++;
 281                 pr_debug("RM_ADDR: id=%d", mp_opt->rm_id);
 282                 break;
 283
 284         default:
 285                 break;
 286         }
 287 }
 288
 289 void mptcp_get_options(const struct sk_buff *skb,
 290                        struct mptcp_options_received *mp_opt)
 291 {
 292         const struct tcphdr *th = tcp_hdr(skb);
 293         const unsigned char *ptr;
 294         int length;
 295
 296         /* initialize option status */
 297         mp_opt->mp_capable = 0;
 298         mp_opt->mp_join = 0;
 299         mp_opt->add_addr = 0;
 300         mp_opt->rm_addr = 0;
 301         mp_opt->dss = 0;
 302
 303         length = (th->doff * 4) - sizeof(struct tcphdr);
 304         ptr = (const unsigned char *)(th + 1);
 305
 306         while (length > 0) {
 307                 int opcode = *ptr++;
 308                 int opsize;
 309
 310                 switch (opcode) {
 311                 case TCPOPT_EOL:
 312                         return;
 313                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 314                         length--;
 315                         continue;
 316                 default:
 317                         opsize = *ptr++;
 318                         if (opsize < 2) /* "silly options" */
 319                                 return;
 320                         if (opsize > length)
 321                                 return; /* don't parse partial options */
 322                         if (opcode == TCPOPT_MPTCP)
 323                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 324                         ptr += opsize - 2;
 325                         length -= opsize;
 326                 }
 327         }
 328 }
 329
 330 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 331                        unsigned int *size, struct mptcp_out_options *opts)
 332 {
 333         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 334
 335         /* we will use snd_isn to detect first pkt [re]transmission
 336          * in mptcp_established_options_mp()
 337          */
 338         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 339         if (subflow->request_mptcp) {
 340                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 341                 *size = TCPOLEN_MPTCP_MPC_SYN;
 342                 return true;
 343         } else if (subflow->request_join) {
 344                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 345                          subflow->local_nonce);
 346                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 347                 opts->join_id = subflow->local_id;
 348                 opts->token = subflow->remote_token;
 349                 opts->nonce = subflow->local_nonce;
 350                 opts->backup = subflow->request_bkup;
 351                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 352                 return true;
 353         }
 354         return false;
 355 }
 356
 357 /* MP_JOIN client subflow must wait for 4th ack before sending any data:
 358  * TCP can't schedule delack timer before the subflow is fully established.
 359  * MPTCP uses the delack timer to do 3rd ack retransmissions
 360  */
 361 static void schedule_3rdack_retransmission(struct sock *sk)
 362 {
 363         struct inet_connection_sock *icsk = inet_csk(sk);
 364         struct tcp_sock *tp = tcp_sk(sk);
 365         unsigned long timeout;
 366
 367         /* reschedule with a timeout above RTT, as we must look only for drop */
 368         if (tp->srtt_us)
 369                 timeout = tp->srtt_us << 1;
 370         else
 371                 timeout = TCP_TIMEOUT_INIT;
 372
 373         WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 374         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 375         icsk->icsk_ack.timeout = timeout;
 376         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 377 }
 378
 379 static void clear_3rdack_retransmission(struct sock *sk)
 380 {
 381         struct inet_connection_sock *icsk = inet_csk(sk);
 382
 383         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 384         icsk->icsk_ack.timeout = 0;
 385         icsk->icsk_ack.ato = 0;
 386         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 387 }
 388
 389 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 390                                          unsigned int *size,
 391                                          unsigned int remaining,
 392                                          struct mptcp_out_options *opts)
 393 {
 394         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 395         struct mptcp_ext *mpext;
 396         unsigned int data_len;
 397
 398         /* When skb is not available, we better over-estimate the emitted
 399          * options len. A full DSS option (28 bytes) is longer than
 400          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 401          * tell the caller to defer the estimate to
 402          * mptcp_established_options_dss(), which will reserve enough space.
 403          */
 404         if (!skb)
 405                 return false;
 406
 407         /* MPC/MPJ needed only on 3rd ack packet */
 408         if (subflow->fully_established ||
 409             subflow->snd_isn != TCP_SKB_CB(skb)->seq)
 410                 return false;
 411
 412         if (subflow->mp_capable) {
 413                 mpext = mptcp_get_ext(skb);
 414                 data_len = mpext ? mpext->data_len : 0;
 415
 416                 /* we will check ext_copy.data_len in mptcp_write_options() to
 417                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 418                  * TCPOLEN_MPTCP_MPC_ACK
 419                  */
 420                 opts->ext_copy.data_len = data_len;
 421                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 422                 opts->sndr_key = subflow->local_key;
 423                 opts->rcvr_key = subflow->remote_key;
 424
 425                 /* Section 3.1.
 426                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 427                  * packets that start the first subflow of an MPTCP connection,
 428                  * as well as the first packet that carries data
 429                  */
 430                 if (data_len > 0)
 431                         *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
 432                 else
 433                         *size = TCPOLEN_MPTCP_MPC_ACK;
 434
 435                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 436                          subflow, subflow->local_key, subflow->remote_key,
 437                          data_len);
 438
 439                 return true;
 440         } else if (subflow->mp_join) {
 441                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 442                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 443                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 444                 pr_debug("subflow=%p", subflow);
 445
 446                 schedule_3rdack_retransmission(sk);
 447                 return true;
 448         }
 449         return false;
 450 }
 451
 452 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 453                                  struct sk_buff *skb, struct mptcp_ext *ext)
 454 {
 455         /* The write_seq value has already been incremented, so the actual
 456          * sequence number for the DATA_FIN is one less.
 457          */
 458         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 459
 460         if (!ext->use_map || !skb->len) {
 461                 /* RFC6824 requires a DSS mapping with specific values
 462                  * if DATA_FIN is set but no data payload is mapped
 463                  */
 464                 ext->data_fin = 1;
 465                 ext->use_map = 1;
 466                 ext->dsn64 = 1;
 467                 ext->data_seq = data_fin_tx_seq;
 468                 ext->subflow_seq = 0;
 469                 ext->data_len = 1;
 470         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 471                 /* If there's an existing DSS mapping and it is the
 472                  * final mapping, DATA_FIN consumes 1 additional byte of
 473                  * mapping space.
 474                  */
 475                 ext->data_fin = 1;
 476                 ext->data_len++;
 477         }
 478 }
 479
 480 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 481                                           unsigned int *size,
 482                                           unsigned int remaining,
 483                                           struct mptcp_out_options *opts)
 484 {
 485         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 486         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 487         unsigned int dss_size = 0;
 488         u64 snd_data_fin_enable;
 489         struct mptcp_ext *mpext;
 490         unsigned int ack_size;
 491         bool ret = false;
 492
 493         mpext = skb ? mptcp_get_ext(skb) : NULL;
 494         snd_data_fin_enable = READ_ONCE(msk->snd_data_fin_enable);
 495
 496         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 497                 unsigned int map_size;
 498
 499                 map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 500
 501                 remaining -= map_size;
 502                 dss_size = map_size;
 503                 if (mpext)
 504                         opts->ext_copy = *mpext;
 505
 506                 if (skb && snd_data_fin_enable)
 507                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 508                 ret = true;
 509         }
 510
 511         /* passive sockets msk will set the 'can_ack' after accept(), even
 512          * if the first subflow may have the already the remote key handy
 513          */
 514         opts->ext_copy.use_ack = 0;
 515         if (!READ_ONCE(msk->can_ack)) {
 516                 *size = ALIGN(dss_size, 4);
 517                 return ret;
 518         }
 519
 520         if (READ_ONCE(msk->use_64bit_ack)) {
 521                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 522                 opts->ext_copy.data_ack = READ_ONCE(msk->ack_seq);
 523                 opts->ext_copy.ack64 = 1;
 524         } else {
 525                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 526                 opts->ext_copy.data_ack32 = (uint32_t)READ_ONCE(msk->ack_seq);
 527                 opts->ext_copy.ack64 = 0;
 528         }
 529         opts->ext_copy.use_ack = 1;
 530
 531         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 532         if (dss_size == 0)
 533                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 534
 535         dss_size += ack_size;
 536
 537         *size = ALIGN(dss_size, 4);
 538         return true;
 539 }
 540
 541 static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 542                                   struct in_addr *addr)
 543 {
 544         u8 hmac[SHA256_DIGEST_SIZE];
 545         u8 msg[7];
 546
 547         msg[0] = addr_id;
 548         memcpy(&msg[1], &addr->s_addr, 4);
 549         msg[5] = 0;
 550         msg[6] = 0;
 551
 552         mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac);
 553
 554         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 555 }
 556
 557 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 558 static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 559                                    struct in6_addr *addr)
 560 {
 561         u8 hmac[SHA256_DIGEST_SIZE];
 562         u8 msg[19];
 563
 564         msg[0] = addr_id;
 565         memcpy(&msg[1], &addr->s6_addr, 16);
 566         msg[17] = 0;
 567         msg[18] = 0;
 568
 569         mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac);
 570
 571         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 572 }
 573 #endif
 574
 575 static bool mptcp_established_options_add_addr(struct sock *sk,
 576                                                unsigned int *size,
 577                                                unsigned int remaining,
 578                                                struct mptcp_out_options *opts)
 579 {
 580         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 581         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 582         struct mptcp_addr_info saddr;
 583         bool echo;
 584         int len;
 585
 586         if (!mptcp_pm_should_add_signal(msk) ||
 587             !(mptcp_pm_add_addr_signal(msk, remaining, &saddr, &echo)))
 588                 return false;
 589
 590         len = mptcp_add_addr_len(saddr.family, echo);
 591         if (remaining < len)
 592                 return false;
 593
 594         *size = len;
 595         opts->addr_id = saddr.id;
 596         if (saddr.family == AF_INET) {
 597                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 598                 opts->addr = saddr.addr;
 599                 if (!echo) {
 600                         opts->ahmac = add_addr_generate_hmac(msk->local_key,
 601                                                              msk->remote_key,
 602                                                              opts->addr_id,
 603                                                              &opts->addr);
 604                 }
 605         }
 606 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 607         else if (saddr.family == AF_INET6) {
 608                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR6;
 609                 opts->addr6 = saddr.addr6;
 610                 if (!echo) {
 611                         opts->ahmac = add_addr6_generate_hmac(msk->local_key,
 612                                                               msk->remote_key,
 613                                                               opts->addr_id,
 614                                                               &opts->addr6);
 615                 }
 616         }
 617 #endif
 618         pr_debug("addr_id=%d, ahmac=%llu, echo=%d", opts->addr_id, opts->ahmac, echo);
 619
 620         return true;
 621 }
 622
 623 static bool mptcp_established_options_rm_addr(struct sock *sk,
 624                                               unsigned int *size,
 625                                               unsigned int remaining,
 626                                               struct mptcp_out_options *opts)
 627 {
 628         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 629         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 630         u8 rm_id;
 631
 632         if (!mptcp_pm_should_rm_signal(msk) ||
 633             !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_id)))
 634                 return false;
 635
 636         if (remaining < TCPOLEN_MPTCP_RM_ADDR_BASE)
 637                 return false;
 638
 639         *size = TCPOLEN_MPTCP_RM_ADDR_BASE;
 640         opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 641         opts->rm_id = rm_id;
 642
 643         pr_debug("rm_id=%d", opts->rm_id);
 644
 645         return true;
 646 }
 647
 648 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 649                                unsigned int *size, unsigned int remaining,
 650                                struct mptcp_out_options *opts)
 651 {
 652         unsigned int opt_size = 0;
 653         bool ret = false;
 654
 655         opts->suboptions = 0;
 656
 657         if (unlikely(mptcp_check_fallback(sk)))
 658                 return false;
 659
 660         /* prevent adding of any MPTCP related options on reset packet
 661          * until we support MP_TCPRST/MP_FASTCLOSE
 662          */
 663         if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 664                 return false;
 665
 666         if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts))
 667                 ret = true;
 668         else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining,
 669                                                opts))
 670                 ret = true;
 671
 672         /* we reserved enough space for the above options, and exceeding the
 673          * TCP option space would be fatal
 674          */
 675         if (WARN_ON_ONCE(opt_size > remaining))
 676                 return false;
 677
 678         *size += opt_size;
 679         remaining -= opt_size;
 680         if (mptcp_established_options_add_addr(sk, &opt_size, remaining, opts)) {
 681                 *size += opt_size;
 682                 remaining -= opt_size;
 683                 ret = true;
 684         } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 685                 *size += opt_size;
 686                 remaining -= opt_size;
 687                 ret = true;
 688         }
 689
 690         return ret;
 691 }
 692
 693 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 694                           struct mptcp_out_options *opts)
 695 {
 696         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 697
 698         if (subflow_req->mp_capable) {
 699                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 700                 opts->sndr_key = subflow_req->local_key;
 701                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 702                 pr_debug("subflow_req=%p, local_key=%llu",
 703                          subflow_req, subflow_req->local_key);
 704                 return true;
 705         } else if (subflow_req->mp_join) {
 706                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 707                 opts->backup = subflow_req->backup;
 708                 opts->join_id = subflow_req->local_id;
 709                 opts->thmac = subflow_req->thmac;
 710                 opts->nonce = subflow_req->local_nonce;
 711                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 712                          subflow_req, opts->backup, opts->join_id,
 713                          opts->thmac, opts->nonce);
 714                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 715                 return true;
 716         }
 717         return false;
 718 }
 719
 720 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 721                                     struct mptcp_subflow_context *subflow,
 722                                     struct sk_buff *skb,
 723                                     struct mptcp_options_received *mp_opt)
 724 {
 725         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 726          * will make the subflow fully established
 727          */
 728         if (likely(subflow->fully_established)) {
 729                 /* on passive sockets, check for 3rd ack retransmission
 730                  * note that msk is always set by subflow_syn_recv_sock()
 731                  * for mp_join subflows
 732                  */
 733                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 734                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 735                     subflow->mp_join && mp_opt->mp_join &&
 736                     READ_ONCE(msk->pm.server_side))
 737                         tcp_send_ack(ssk);
 738                 goto fully_established;
 739         }
 740
 741         /* we must process OoO packets before the first subflow is fully
 742          * established. OoO packets are instead a protocol violation
 743          * for MP_JOIN subflows as the peer must not send any data
 744          * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 745          */
 746         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 747                 if (subflow->mp_join)
 748                         goto reset;
 749                 return subflow->mp_capable;
 750         }
 751
 752         if (mp_opt->dss && mp_opt->use_ack) {
 753                 /* subflows are fully established as soon as we get any
 754                  * additional ack.
 755                  */
 756                 subflow->fully_established = 1;
 757                 WRITE_ONCE(msk->fully_established, true);
 758                 goto fully_established;
 759         }
 760
 761         /* If the first established packet does not contain MP_CAPABLE + data
 762          * then fallback to TCP. Fallback scenarios requires a reset for
 763          * MP_JOIN subflows.
 764          */
 765         if (!mp_opt->mp_capable) {
 766                 if (subflow->mp_join)
 767                         goto reset;
 768                 subflow->mp_capable = 0;
 769                 pr_fallback(msk);
 770                 __mptcp_do_fallback(msk);
 771                 return false;
 772         }
 773
 774         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 775                 pr_warn_once("bogus mpc option on established client sk");
 776         mptcp_subflow_fully_established(subflow, mp_opt);
 777
 778 fully_established:
 779         if (likely(subflow->pm_notified))
 780                 return true;
 781
 782         subflow->pm_notified = 1;
 783         if (subflow->mp_join) {
 784                 clear_3rdack_retransmission(ssk);
 785                 mptcp_pm_subflow_established(msk, subflow);
 786         } else {
 787                 mptcp_pm_fully_established(msk);
 788         }
 789         return true;
 790
 791 reset:
 792         mptcp_subflow_reset(ssk);
 793         return false;
 794 }
 795
 796 static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)
 797 {
 798         u32 old_ack32, cur_ack32;
 799
 800         if (use_64bit)
 801                 return cur_ack;
 802
 803         old_ack32 = (u32)old_ack;
 804         cur_ack32 = (u32)cur_ack;
 805         cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32;
 806         if (unlikely(before(cur_ack32, old_ack32)))
 807                 return cur_ack + (1LL << 32);
 808         return cur_ack;
 809 }
 810
 811 static void update_una(struct mptcp_sock *msk,
 812                        struct mptcp_options_received *mp_opt)
 813 {
 814         u64 new_snd_una, snd_una, old_snd_una = atomic64_read(&msk->snd_una);
 815         u64 write_seq = READ_ONCE(msk->write_seq);
 816
 817         /* avoid ack expansion on update conflict, to reduce the risk of
 818          * wrongly expanding to a future ack sequence number, which is way
 819          * more dangerous than missing an ack
 820          */
 821         new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 822
 823         /* ACK for data not even sent yet? Ignore. */
 824         if (after64(new_snd_una, write_seq))
 825                 new_snd_una = old_snd_una;
 826
 827         while (after64(new_snd_una, old_snd_una)) {
 828                 snd_una = old_snd_una;
 829                 old_snd_una = atomic64_cmpxchg(&msk->snd_una, snd_una,
 830                                                new_snd_una);
 831                 if (old_snd_una == snd_una) {
 832                         mptcp_data_acked((struct sock *)msk);
 833                         break;
 834                 }
 835         }
 836 }
 837
 838 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
 839 {
 840         /* Skip if DATA_FIN was already received.
 841          * If updating simultaneously with the recvmsg loop, values
 842          * should match. If they mismatch, the peer is misbehaving and
 843          * we will prefer the most recent information.
 844          */
 845         if (READ_ONCE(msk->rcv_data_fin) || !READ_ONCE(msk->first))
 846                 return false;
 847
 848         WRITE_ONCE(msk->rcv_data_fin_seq,
 849                    expand_ack(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
 850         WRITE_ONCE(msk->rcv_data_fin, 1);
 851
 852         return true;
 853 }
 854
 855 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
 856                                 struct mptcp_options_received *mp_opt)
 857 {
 858         u64 hmac = 0;
 859
 860         if (mp_opt->echo)
 861                 return true;
 862
 863         if (mp_opt->family == MPTCP_ADDR_IPVERSION_4)
 864                 hmac = add_addr_generate_hmac(msk->remote_key,
 865                                               msk->local_key,
 866                                               mp_opt->addr_id, &mp_opt->addr);
 867 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 868         else
 869                 hmac = add_addr6_generate_hmac(msk->remote_key,
 870                                                msk->local_key,
 871                                                mp_opt->addr_id, &mp_opt->addr6);
 872 #endif
 873
 874         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
 875                  msk, (unsigned long long)hmac,
 876                  (unsigned long long)mp_opt->ahmac);
 877
 878         return hmac == mp_opt->ahmac;
 879 }
 880
 881 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 882 {
 883         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 884         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 885         struct mptcp_options_received mp_opt;
 886         struct mptcp_ext *mpext;
 887
 888         if (__mptcp_check_fallback(msk))
 889                 return;
 890
 891         mptcp_get_options(skb, &mp_opt);
 892         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
 893                 return;
 894
 895         if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
 896                 struct mptcp_addr_info addr;
 897
 898                 addr.port = htons(mp_opt.port);
 899                 addr.id = mp_opt.addr_id;
 900                 if (mp_opt.family == MPTCP_ADDR_IPVERSION_4) {
 901                         addr.family = AF_INET;
 902                         addr.addr = mp_opt.addr;
 903                 }
 904 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 905                 else if (mp_opt.family == MPTCP_ADDR_IPVERSION_6) {
 906                         addr.family = AF_INET6;
 907                         addr.addr6 = mp_opt.addr6;
 908                 }
 909 #endif
 910                 if (!mp_opt.echo) {
 911                         mptcp_pm_add_addr_received(msk, &addr);
 912                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
 913                 } else {
 914                         mptcp_pm_del_add_timer(msk, &addr);
 915                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
 916                 }
 917                 mp_opt.add_addr = 0;
 918         }
 919
 920         if (mp_opt.rm_addr) {
 921                 mptcp_pm_rm_addr_received(msk, mp_opt.rm_id);
 922                 mp_opt.rm_addr = 0;
 923         }
 924
 925         if (!mp_opt.dss)
 926                 return;
 927
 928         /* we can't wait for recvmsg() to update the ack_seq, otherwise
 929          * monodirectional flows will stuck
 930          */
 931         if (mp_opt.use_ack)
 932                 update_una(msk, &mp_opt);
 933
 934         /* Zero-data-length packets are dropped by the caller and not
 935          * propagated to the MPTCP layer, so the skb extension does not
 936          * need to be allocated or populated. DATA_FIN information, if
 937          * present, needs to be updated here before the skb is freed.
 938          */
 939         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
 940                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
 941                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
 942                     schedule_work(&msk->work))
 943                         sock_hold(subflow->conn);
 944
 945                 return;
 946         }
 947
 948         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
 949         if (!mpext)
 950                 return;
 951
 952         memset(mpext, 0, sizeof(*mpext));
 953
 954         if (mp_opt.use_map) {
 955                 if (mp_opt.mpc_map) {
 956                         /* this is an MP_CAPABLE carrying MPTCP data
 957                          * we know this map the first chunk of data
 958                          */
 959                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
 960                                              &mpext->data_seq);
 961                         mpext->data_seq++;
 962                         mpext->subflow_seq = 1;
 963                         mpext->dsn64 = 1;
 964                         mpext->mpc_map = 1;
 965                         mpext->data_fin = 0;
 966                 } else {
 967                         mpext->data_seq = mp_opt.data_seq;
 968                         mpext->subflow_seq = mp_opt.subflow_seq;
 969                         mpext->dsn64 = mp_opt.dsn64;
 970                         mpext->data_fin = mp_opt.data_fin;
 971                 }
 972                 mpext->data_len = mp_opt.data_len;
 973                 mpext->use_map = 1;
 974         }
 975 }
 976
 977 void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts)
 978 {
 979         if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
 980              OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
 981                 u8 len;
 982
 983                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
 984                         len = TCPOLEN_MPTCP_MPC_SYN;
 985                 else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
 986                         len = TCPOLEN_MPTCP_MPC_SYNACK;
 987                 else if (opts->ext_copy.data_len)
 988                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 989                 else
 990                         len = TCPOLEN_MPTCP_MPC_ACK;
 991
 992                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
 993                                       MPTCP_SUPPORTED_VERSION,
 994                                       MPTCP_CAP_HMAC_SHA256);
 995
 996                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
 997                     opts->suboptions))
 998                         goto mp_capable_done;
 999
1000                 put_unaligned_be64(opts->sndr_key, ptr);
1001                 ptr += 2;
1002                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1003                         goto mp_capable_done;
1004
1005                 put_unaligned_be64(opts->rcvr_key, ptr);
1006                 ptr += 2;
1007                 if (!opts->ext_copy.data_len)
1008                         goto mp_capable_done;
1009
1010                 put_unaligned_be32(opts->ext_copy.data_len << 16 |
1011                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1012                 ptr += 1;
1013         }
1014
1015 mp_capable_done:
1016         if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1017                 if (opts->ahmac)
1018                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1019                                               TCPOLEN_MPTCP_ADD_ADDR, 0,
1020                                               opts->addr_id);
1021                 else
1022                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1023                                               TCPOLEN_MPTCP_ADD_ADDR_BASE,
1024                                               MPTCP_ADDR_ECHO,
1025                                               opts->addr_id);
1026                 memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4);
1027                 ptr += 1;
1028                 if (opts->ahmac) {
1029                         put_unaligned_be64(opts->ahmac, ptr);
1030                         ptr += 2;
1031                 }
1032         }
1033
1034 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1035         if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) {
1036                 if (opts->ahmac)
1037                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1038                                               TCPOLEN_MPTCP_ADD_ADDR6, 0,
1039                                               opts->addr_id);
1040                 else
1041                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1042                                               TCPOLEN_MPTCP_ADD_ADDR6_BASE,
1043                                               MPTCP_ADDR_ECHO,
1044                                               opts->addr_id);
1045                 memcpy((u8 *)ptr, opts->addr6.s6_addr, 16);
1046                 ptr += 4;
1047                 if (opts->ahmac) {
1048                         put_unaligned_be64(opts->ahmac, ptr);
1049                         ptr += 2;
1050                 }
1051         }
1052 #endif
1053
1054         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1055                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1056                                       TCPOLEN_MPTCP_RM_ADDR_BASE,
1057                                       0, opts->rm_id);
1058         }
1059
1060         if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1061                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1062                                       TCPOLEN_MPTCP_MPJ_SYN,
1063                                       opts->backup, opts->join_id);
1064                 put_unaligned_be32(opts->token, ptr);
1065                 ptr += 1;
1066                 put_unaligned_be32(opts->nonce, ptr);
1067                 ptr += 1;
1068         }
1069
1070         if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1071                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1072                                       TCPOLEN_MPTCP_MPJ_SYNACK,
1073                                       opts->backup, opts->join_id);
1074                 put_unaligned_be64(opts->thmac, ptr);
1075                 ptr += 2;
1076                 put_unaligned_be32(opts->nonce, ptr);
1077                 ptr += 1;
1078         }
1079
1080         if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
1081                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1082                                       TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1083                 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1084                 ptr += 5;
1085         }
1086
1087         if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
1088                 struct mptcp_ext *mpext = &opts->ext_copy;
1089                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1090                 u8 flags = 0;
1091
1092                 if (mpext->use_ack) {
1093                         flags = MPTCP_DSS_HAS_ACK;
1094                         if (mpext->ack64) {
1095                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1096                                 flags |= MPTCP_DSS_ACK64;
1097                         } else {
1098                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1099                         }
1100                 }
1101
1102                 if (mpext->use_map) {
1103                         len += TCPOLEN_MPTCP_DSS_MAP64;
1104
1105                         /* Use only 64-bit mapping flags for now, add
1106                          * support for optional 32-bit mappings later.
1107                          */
1108                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1109                         if (mpext->data_fin)
1110                                 flags |= MPTCP_DSS_DATA_FIN;
1111                 }
1112
1113                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1114
1115                 if (mpext->use_ack) {
1116                         if (mpext->ack64) {
1117                                 put_unaligned_be64(mpext->data_ack, ptr);
1118                                 ptr += 2;
1119                         } else {
1120                                 put_unaligned_be32(mpext->data_ack32, ptr);
1121                                 ptr += 1;
1122                         }
1123                 }
1124
1125                 if (mpext->use_map) {
1126                         put_unaligned_be64(mpext->data_seq, ptr);
1127                         ptr += 2;
1128                         put_unaligned_be32(mpext->subflow_seq, ptr);
1129                         ptr += 1;
1130                         put_unaligned_be32(mpext->data_len << 16 |
1131                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1132                 }
1133         }
1134 }