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->addr_id = *ptr++;
 245                 pr_debug("ADD_ADDR%s: id=%d, echo=%d",
 246                          (mp_opt->family == MPTCP_ADDR_IPVERSION_6) ? "6" : "",
 247                          mp_opt->addr_id, mp_opt->echo);
 248                 if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) {
 249                         memcpy((u8 *)&mp_opt->addr.s_addr, (u8 *)ptr, 4);
 250                         ptr += 4;
 251                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 252                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 253                                 mp_opt->port = get_unaligned_be16(ptr);
 254                                 ptr += 2;
 255                         }
 256                 }
 257 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 258                 else {
 259                         memcpy(mp_opt->addr6.s6_addr, (u8 *)ptr, 16);
 260                         ptr += 16;
 261                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 262                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 263                                 mp_opt->port = get_unaligned_be16(ptr);
 264                                 ptr += 2;
 265                         }
 266                 }
 267 #endif
 268                 if (!mp_opt->echo) {
 269                         mp_opt->ahmac = get_unaligned_be64(ptr);
 270                         ptr += 8;
 271                 }
 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         default:
 286                 break;
 287         }
 288 }
 289
 290 void mptcp_get_options(const struct sk_buff *skb,
 291                        struct mptcp_options_received *mp_opt)
 292 {
 293         const struct tcphdr *th = tcp_hdr(skb);
 294         const unsigned char *ptr;
 295         int length;
 296
 297         /* initialize option status */
 298         mp_opt->mp_capable = 0;
 299         mp_opt->mp_join = 0;
 300         mp_opt->add_addr = 0;
 301         mp_opt->ahmac = 0;
 302         mp_opt->port = 0;
 303         mp_opt->rm_addr = 0;
 304         mp_opt->dss = 0;
 305
 306         length = (th->doff * 4) - sizeof(struct tcphdr);
 307         ptr = (const unsigned char *)(th + 1);
 308
 309         while (length > 0) {
 310                 int opcode = *ptr++;
 311                 int opsize;
 312
 313                 switch (opcode) {
 314                 case TCPOPT_EOL:
 315                         return;
 316                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 317                         length--;
 318                         continue;
 319                 default:
 320                         opsize = *ptr++;
 321                         if (opsize < 2) /* "silly options" */
 322                                 return;
 323                         if (opsize > length)
 324                                 return; /* don't parse partial options */
 325                         if (opcode == TCPOPT_MPTCP)
 326                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 327                         ptr += opsize - 2;
 328                         length -= opsize;
 329                 }
 330         }
 331 }
 332
 333 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 334                        unsigned int *size, struct mptcp_out_options *opts)
 335 {
 336         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 337
 338         /* we will use snd_isn to detect first pkt [re]transmission
 339          * in mptcp_established_options_mp()
 340          */
 341         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 342         if (subflow->request_mptcp) {
 343                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 344                 *size = TCPOLEN_MPTCP_MPC_SYN;
 345                 return true;
 346         } else if (subflow->request_join) {
 347                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 348                          subflow->local_nonce);
 349                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 350                 opts->join_id = subflow->local_id;
 351                 opts->token = subflow->remote_token;
 352                 opts->nonce = subflow->local_nonce;
 353                 opts->backup = subflow->request_bkup;
 354                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 355                 return true;
 356         }
 357         return false;
 358 }
 359
 360 /* MP_JOIN client subflow must wait for 4th ack before sending any data:
 361  * TCP can't schedule delack timer before the subflow is fully established.
 362  * MPTCP uses the delack timer to do 3rd ack retransmissions
 363  */
 364 static void schedule_3rdack_retransmission(struct sock *sk)
 365 {
 366         struct inet_connection_sock *icsk = inet_csk(sk);
 367         struct tcp_sock *tp = tcp_sk(sk);
 368         unsigned long timeout;
 369
 370         /* reschedule with a timeout above RTT, as we must look only for drop */
 371         if (tp->srtt_us)
 372                 timeout = tp->srtt_us << 1;
 373         else
 374                 timeout = TCP_TIMEOUT_INIT;
 375
 376         WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 377         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 378         icsk->icsk_ack.timeout = timeout;
 379         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 380 }
 381
 382 static void clear_3rdack_retransmission(struct sock *sk)
 383 {
 384         struct inet_connection_sock *icsk = inet_csk(sk);
 385
 386         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 387         icsk->icsk_ack.timeout = 0;
 388         icsk->icsk_ack.ato = 0;
 389         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 390 }
 391
 392 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 393                                          unsigned int *size,
 394                                          unsigned int remaining,
 395                                          struct mptcp_out_options *opts)
 396 {
 397         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 398         struct mptcp_ext *mpext;
 399         unsigned int data_len;
 400
 401         /* When skb is not available, we better over-estimate the emitted
 402          * options len. A full DSS option (28 bytes) is longer than
 403          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 404          * tell the caller to defer the estimate to
 405          * mptcp_established_options_dss(), which will reserve enough space.
 406          */
 407         if (!skb)
 408                 return false;
 409
 410         /* MPC/MPJ needed only on 3rd ack packet */
 411         if (subflow->fully_established ||
 412             subflow->snd_isn != TCP_SKB_CB(skb)->seq)
 413                 return false;
 414
 415         if (subflow->mp_capable) {
 416                 mpext = mptcp_get_ext(skb);
 417                 data_len = mpext ? mpext->data_len : 0;
 418
 419                 /* we will check ext_copy.data_len in mptcp_write_options() to
 420                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 421                  * TCPOLEN_MPTCP_MPC_ACK
 422                  */
 423                 opts->ext_copy.data_len = data_len;
 424                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 425                 opts->sndr_key = subflow->local_key;
 426                 opts->rcvr_key = subflow->remote_key;
 427
 428                 /* Section 3.1.
 429                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 430                  * packets that start the first subflow of an MPTCP connection,
 431                  * as well as the first packet that carries data
 432                  */
 433                 if (data_len > 0)
 434                         *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
 435                 else
 436                         *size = TCPOLEN_MPTCP_MPC_ACK;
 437
 438                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 439                          subflow, subflow->local_key, subflow->remote_key,
 440                          data_len);
 441
 442                 return true;
 443         } else if (subflow->mp_join) {
 444                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 445                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 446                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 447                 pr_debug("subflow=%p", subflow);
 448
 449                 schedule_3rdack_retransmission(sk);
 450                 return true;
 451         }
 452         return false;
 453 }
 454
 455 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 456                                  struct sk_buff *skb, struct mptcp_ext *ext)
 457 {
 458         /* The write_seq value has already been incremented, so the actual
 459          * sequence number for the DATA_FIN is one less.
 460          */
 461         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 462
 463         if (!ext->use_map || !skb->len) {
 464                 /* RFC6824 requires a DSS mapping with specific values
 465                  * if DATA_FIN is set but no data payload is mapped
 466                  */
 467                 ext->data_fin = 1;
 468                 ext->use_map = 1;
 469                 ext->dsn64 = 1;
 470                 ext->data_seq = data_fin_tx_seq;
 471                 ext->subflow_seq = 0;
 472                 ext->data_len = 1;
 473         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 474                 /* If there's an existing DSS mapping and it is the
 475                  * final mapping, DATA_FIN consumes 1 additional byte of
 476                  * mapping space.
 477                  */
 478                 ext->data_fin = 1;
 479                 ext->data_len++;
 480         }
 481 }
 482
 483 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 484                                           unsigned int *size,
 485                                           unsigned int remaining,
 486                                           struct mptcp_out_options *opts)
 487 {
 488         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 489         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 490         unsigned int dss_size = 0;
 491         u64 snd_data_fin_enable;
 492         struct mptcp_ext *mpext;
 493         unsigned int ack_size;
 494         bool ret = false;
 495
 496         mpext = skb ? mptcp_get_ext(skb) : NULL;
 497         snd_data_fin_enable = mptcp_data_fin_enabled(msk);
 498
 499         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 500                 unsigned int map_size;
 501
 502                 map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 503
 504                 remaining -= map_size;
 505                 dss_size = map_size;
 506                 if (mpext)
 507                         opts->ext_copy = *mpext;
 508
 509                 if (skb && snd_data_fin_enable)
 510                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 511                 ret = true;
 512         }
 513
 514         /* passive sockets msk will set the 'can_ack' after accept(), even
 515          * if the first subflow may have the already the remote key handy
 516          */
 517         opts->ext_copy.use_ack = 0;
 518         if (!READ_ONCE(msk->can_ack)) {
 519                 *size = ALIGN(dss_size, 4);
 520                 return ret;
 521         }
 522
 523         if (READ_ONCE(msk->use_64bit_ack)) {
 524                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 525                 opts->ext_copy.data_ack = READ_ONCE(msk->ack_seq);
 526                 opts->ext_copy.ack64 = 1;
 527         } else {
 528                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 529                 opts->ext_copy.data_ack32 = (uint32_t)READ_ONCE(msk->ack_seq);
 530                 opts->ext_copy.ack64 = 0;
 531         }
 532         opts->ext_copy.use_ack = 1;
 533         WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 534
 535         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 536         if (dss_size == 0)
 537                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 538
 539         dss_size += ack_size;
 540
 541         *size = ALIGN(dss_size, 4);
 542         return true;
 543 }
 544
 545 static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 546                                   struct in_addr *addr)
 547 {
 548         u8 hmac[SHA256_DIGEST_SIZE];
 549         u8 msg[7];
 550
 551         msg[0] = addr_id;
 552         memcpy(&msg[1], &addr->s_addr, 4);
 553         msg[5] = 0;
 554         msg[6] = 0;
 555
 556         mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac);
 557
 558         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 559 }
 560
 561 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 562 static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 563                                    struct in6_addr *addr)
 564 {
 565         u8 hmac[SHA256_DIGEST_SIZE];
 566         u8 msg[19];
 567
 568         msg[0] = addr_id;
 569         memcpy(&msg[1], &addr->s6_addr, 16);
 570         msg[17] = 0;
 571         msg[18] = 0;
 572
 573         mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac);
 574
 575         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 576 }
 577 #endif
 578
 579 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 580                                                unsigned int *size,
 581                                                unsigned int remaining,
 582                                                struct mptcp_out_options *opts)
 583 {
 584         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 585         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 586         bool drop_other_suboptions = false;
 587         unsigned int opt_size = *size;
 588         struct mptcp_addr_info saddr;
 589         bool echo;
 590         int len;
 591
 592         if (mptcp_pm_should_add_signal_ipv6(msk) &&
 593             skb && skb_is_tcp_pure_ack(skb)) {
 594                 pr_debug("drop other suboptions");
 595                 opts->suboptions = 0;
 596                 remaining += opt_size;
 597                 drop_other_suboptions = true;
 598         }
 599
 600         if (!mptcp_pm_should_add_signal(msk) ||
 601             !(mptcp_pm_add_addr_signal(msk, remaining, &saddr, &echo)))
 602                 return false;
 603
 604         len = mptcp_add_addr_len(saddr.family, echo);
 605         if (remaining < len)
 606                 return false;
 607
 608         *size = len;
 609         if (drop_other_suboptions)
 610                 *size -= opt_size;
 611         opts->addr_id = saddr.id;
 612         if (saddr.family == AF_INET) {
 613                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 614                 opts->addr = saddr.addr;
 615                 if (!echo) {
 616                         opts->ahmac = add_addr_generate_hmac(msk->local_key,
 617                                                              msk->remote_key,
 618                                                              opts->addr_id,
 619                                                              &opts->addr);
 620                 }
 621         }
 622 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 623         else if (saddr.family == AF_INET6) {
 624                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR6;
 625                 opts->addr6 = saddr.addr6;
 626                 if (!echo) {
 627                         opts->ahmac = add_addr6_generate_hmac(msk->local_key,
 628                                                               msk->remote_key,
 629                                                               opts->addr_id,
 630                                                               &opts->addr6);
 631                 }
 632         }
 633 #endif
 634         pr_debug("addr_id=%d, ahmac=%llu, echo=%d", opts->addr_id, opts->ahmac, echo);
 635
 636         return true;
 637 }
 638
 639 static bool mptcp_established_options_rm_addr(struct sock *sk,
 640                                               unsigned int *size,
 641                                               unsigned int remaining,
 642                                               struct mptcp_out_options *opts)
 643 {
 644         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 645         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 646         u8 rm_id;
 647
 648         if (!mptcp_pm_should_rm_signal(msk) ||
 649             !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_id)))
 650                 return false;
 651
 652         if (remaining < TCPOLEN_MPTCP_RM_ADDR_BASE)
 653                 return false;
 654
 655         *size = TCPOLEN_MPTCP_RM_ADDR_BASE;
 656         opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 657         opts->rm_id = rm_id;
 658
 659         pr_debug("rm_id=%d", opts->rm_id);
 660
 661         return true;
 662 }
 663
 664 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 665                                unsigned int *size, unsigned int remaining,
 666                                struct mptcp_out_options *opts)
 667 {
 668         unsigned int opt_size = 0;
 669         bool ret = false;
 670
 671         opts->suboptions = 0;
 672
 673         if (unlikely(mptcp_check_fallback(sk)))
 674                 return false;
 675
 676         /* prevent adding of any MPTCP related options on reset packet
 677          * until we support MP_TCPRST/MP_FASTCLOSE
 678          */
 679         if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 680                 return false;
 681
 682         if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts))
 683                 ret = true;
 684         else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining,
 685                                                opts))
 686                 ret = true;
 687
 688         /* we reserved enough space for the above options, and exceeding the
 689          * TCP option space would be fatal
 690          */
 691         if (WARN_ON_ONCE(opt_size > remaining))
 692                 return false;
 693
 694         *size += opt_size;
 695         remaining -= opt_size;
 696         if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
 697                 *size += opt_size;
 698                 remaining -= opt_size;
 699                 ret = true;
 700         } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 701                 *size += opt_size;
 702                 remaining -= opt_size;
 703                 ret = true;
 704         }
 705
 706         return ret;
 707 }
 708
 709 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 710                           struct mptcp_out_options *opts)
 711 {
 712         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 713
 714         if (subflow_req->mp_capable) {
 715                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 716                 opts->sndr_key = subflow_req->local_key;
 717                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 718                 pr_debug("subflow_req=%p, local_key=%llu",
 719                          subflow_req, subflow_req->local_key);
 720                 return true;
 721         } else if (subflow_req->mp_join) {
 722                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 723                 opts->backup = subflow_req->backup;
 724                 opts->join_id = subflow_req->local_id;
 725                 opts->thmac = subflow_req->thmac;
 726                 opts->nonce = subflow_req->local_nonce;
 727                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 728                          subflow_req, opts->backup, opts->join_id,
 729                          opts->thmac, opts->nonce);
 730                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 731                 return true;
 732         }
 733         return false;
 734 }
 735
 736 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 737                                     struct mptcp_subflow_context *subflow,
 738                                     struct sk_buff *skb,
 739                                     struct mptcp_options_received *mp_opt)
 740 {
 741         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 742          * will make the subflow fully established
 743          */
 744         if (likely(subflow->fully_established)) {
 745                 /* on passive sockets, check for 3rd ack retransmission
 746                  * note that msk is always set by subflow_syn_recv_sock()
 747                  * for mp_join subflows
 748                  */
 749                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 750                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 751                     subflow->mp_join && mp_opt->mp_join &&
 752                     READ_ONCE(msk->pm.server_side))
 753                         tcp_send_ack(ssk);
 754                 goto fully_established;
 755         }
 756
 757         /* we must process OoO packets before the first subflow is fully
 758          * established. OoO packets are instead a protocol violation
 759          * for MP_JOIN subflows as the peer must not send any data
 760          * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 761          */
 762         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 763                 if (subflow->mp_join)
 764                         goto reset;
 765                 return subflow->mp_capable;
 766         }
 767
 768         if (mp_opt->dss && mp_opt->use_ack) {
 769                 /* subflows are fully established as soon as we get any
 770                  * additional ack.
 771                  */
 772                 subflow->fully_established = 1;
 773                 WRITE_ONCE(msk->fully_established, true);
 774                 goto fully_established;
 775         }
 776
 777         if (mp_opt->add_addr) {
 778                 WRITE_ONCE(msk->fully_established, true);
 779                 return true;
 780         }
 781
 782         /* If the first established packet does not contain MP_CAPABLE + data
 783          * then fallback to TCP. Fallback scenarios requires a reset for
 784          * MP_JOIN subflows.
 785          */
 786         if (!mp_opt->mp_capable) {
 787                 if (subflow->mp_join)
 788                         goto reset;
 789                 subflow->mp_capable = 0;
 790                 pr_fallback(msk);
 791                 __mptcp_do_fallback(msk);
 792                 return false;
 793         }
 794
 795         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 796                 pr_warn_once("bogus mpc option on established client sk");
 797         mptcp_subflow_fully_established(subflow, mp_opt);
 798
 799 fully_established:
 800         if (likely(subflow->pm_notified))
 801                 return true;
 802
 803         subflow->pm_notified = 1;
 804         if (subflow->mp_join) {
 805                 clear_3rdack_retransmission(ssk);
 806                 mptcp_pm_subflow_established(msk, subflow);
 807         } else {
 808                 mptcp_pm_fully_established(msk);
 809         }
 810         return true;
 811
 812 reset:
 813         mptcp_subflow_reset(ssk);
 814         return false;
 815 }
 816
 817 static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)
 818 {
 819         u32 old_ack32, cur_ack32;
 820
 821         if (use_64bit)
 822                 return cur_ack;
 823
 824         old_ack32 = (u32)old_ack;
 825         cur_ack32 = (u32)cur_ack;
 826         cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32;
 827         if (unlikely(before(cur_ack32, old_ack32)))
 828                 return cur_ack + (1LL << 32);
 829         return cur_ack;
 830 }
 831
 832 static void ack_update_msk(struct mptcp_sock *msk,
 833                            struct sock *ssk,
 834                            struct mptcp_options_received *mp_opt)
 835 {
 836         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
 837         struct sock *sk = (struct sock *)msk;
 838         u64 old_snd_una;
 839
 840         mptcp_data_lock(sk);
 841
 842         /* avoid ack expansion on update conflict, to reduce the risk of
 843          * wrongly expanding to a future ack sequence number, which is way
 844          * more dangerous than missing an ack
 845          */
 846         old_snd_una = msk->snd_una;
 847         new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 848
 849         /* ACK for data not even sent yet? Ignore. */
 850         if (after64(new_snd_una, snd_nxt))
 851                 new_snd_una = old_snd_una;
 852
 853         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
 854
 855         if (after64(new_wnd_end, msk->wnd_end)) {
 856                 msk->wnd_end = new_wnd_end;
 857                 __mptcp_wnd_updated(sk, ssk);
 858         }
 859
 860         if (after64(new_snd_una, old_snd_una)) {
 861                 msk->snd_una = new_snd_una;
 862                 __mptcp_data_acked(sk);
 863         }
 864         mptcp_data_unlock(sk);
 865 }
 866
 867 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
 868 {
 869         /* Skip if DATA_FIN was already received.
 870          * If updating simultaneously with the recvmsg loop, values
 871          * should match. If they mismatch, the peer is misbehaving and
 872          * we will prefer the most recent information.
 873          */
 874         if (READ_ONCE(msk->rcv_data_fin) || !READ_ONCE(msk->first))
 875                 return false;
 876
 877         WRITE_ONCE(msk->rcv_data_fin_seq,
 878                    expand_ack(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
 879         WRITE_ONCE(msk->rcv_data_fin, 1);
 880
 881         return true;
 882 }
 883
 884 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
 885                                 struct mptcp_options_received *mp_opt)
 886 {
 887         u64 hmac = 0;
 888
 889         if (mp_opt->echo)
 890                 return true;
 891
 892         if (mp_opt->family == MPTCP_ADDR_IPVERSION_4)
 893                 hmac = add_addr_generate_hmac(msk->remote_key,
 894                                               msk->local_key,
 895                                               mp_opt->addr_id, &mp_opt->addr);
 896 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 897         else
 898                 hmac = add_addr6_generate_hmac(msk->remote_key,
 899                                                msk->local_key,
 900                                                mp_opt->addr_id, &mp_opt->addr6);
 901 #endif
 902
 903         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
 904                  msk, (unsigned long long)hmac,
 905                  (unsigned long long)mp_opt->ahmac);
 906
 907         return hmac == mp_opt->ahmac;
 908 }
 909
 910 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 911 {
 912         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 913         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 914         struct mptcp_options_received mp_opt;
 915         struct mptcp_ext *mpext;
 916
 917         if (__mptcp_check_fallback(msk)) {
 918                 /* Keep it simple and unconditionally trigger send data cleanup and
 919                  * pending queue spooling. We will need to acquire the data lock
 920                  * for more accurate checks, and once the lock is acquired, such
 921                  * helpers are cheap.
 922                  */
 923                 mptcp_data_lock(subflow->conn);
 924                 if (mptcp_send_head(subflow->conn))
 925                         __mptcp_wnd_updated(subflow->conn, sk);
 926                 __mptcp_data_acked(subflow->conn);
 927                 mptcp_data_unlock(subflow->conn);
 928                 return;
 929         }
 930
 931         mptcp_get_options(skb, &mp_opt);
 932         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
 933                 return;
 934
 935         if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
 936                 struct mptcp_addr_info addr;
 937
 938                 addr.port = htons(mp_opt.port);
 939                 addr.id = mp_opt.addr_id;
 940                 if (mp_opt.family == MPTCP_ADDR_IPVERSION_4) {
 941                         addr.family = AF_INET;
 942                         addr.addr = mp_opt.addr;
 943                 }
 944 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 945                 else if (mp_opt.family == MPTCP_ADDR_IPVERSION_6) {
 946                         addr.family = AF_INET6;
 947                         addr.addr6 = mp_opt.addr6;
 948                 }
 949 #endif
 950                 if (!mp_opt.echo) {
 951                         mptcp_pm_add_addr_received(msk, &addr);
 952                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
 953                 } else {
 954                         mptcp_pm_del_add_timer(msk, &addr);
 955                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
 956                 }
 957                 mp_opt.add_addr = 0;
 958         }
 959
 960         if (mp_opt.rm_addr) {
 961                 mptcp_pm_rm_addr_received(msk, mp_opt.rm_id);
 962                 mp_opt.rm_addr = 0;
 963         }
 964
 965         if (!mp_opt.dss)
 966                 return;
 967
 968         /* we can't wait for recvmsg() to update the ack_seq, otherwise
 969          * monodirectional flows will stuck
 970          */
 971         if (mp_opt.use_ack)
 972                 ack_update_msk(msk, sk, &mp_opt);
 973
 974         /* Zero-data-length packets are dropped by the caller and not
 975          * propagated to the MPTCP layer, so the skb extension does not
 976          * need to be allocated or populated. DATA_FIN information, if
 977          * present, needs to be updated here before the skb is freed.
 978          */
 979         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
 980                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
 981                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
 982                     schedule_work(&msk->work))
 983                         sock_hold(subflow->conn);
 984
 985                 return;
 986         }
 987
 988         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
 989         if (!mpext)
 990                 return;
 991
 992         memset(mpext, 0, sizeof(*mpext));
 993
 994         if (mp_opt.use_map) {
 995                 if (mp_opt.mpc_map) {
 996                         /* this is an MP_CAPABLE carrying MPTCP data
 997                          * we know this map the first chunk of data
 998                          */
 999                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1000                                              &mpext->data_seq);
1001                         mpext->data_seq++;
1002                         mpext->subflow_seq = 1;
1003                         mpext->dsn64 = 1;
1004                         mpext->mpc_map = 1;
1005                         mpext->data_fin = 0;
1006                 } else {
1007                         mpext->data_seq = mp_opt.data_seq;
1008                         mpext->subflow_seq = mp_opt.subflow_seq;
1009                         mpext->dsn64 = mp_opt.dsn64;
1010                         mpext->data_fin = mp_opt.data_fin;
1011                 }
1012                 mpext->data_len = mp_opt.data_len;
1013                 mpext->use_map = 1;
1014         }
1015 }
1016
1017 static void mptcp_set_rwin(const struct tcp_sock *tp)
1018 {
1019         const struct sock *ssk = (const struct sock *)tp;
1020         const struct mptcp_subflow_context *subflow;
1021         struct mptcp_sock *msk;
1022         u64 ack_seq;
1023
1024         subflow = mptcp_subflow_ctx(ssk);
1025         msk = mptcp_sk(subflow->conn);
1026
1027         ack_seq = READ_ONCE(msk->ack_seq) + tp->rcv_wnd;
1028
1029         if (after64(ack_seq, READ_ONCE(msk->rcv_wnd_sent)))
1030                 WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
1031 }
1032
1033 void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
1034                          struct mptcp_out_options *opts)
1035 {
1036         if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
1037              OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
1038                 u8 len;
1039
1040                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
1041                         len = TCPOLEN_MPTCP_MPC_SYN;
1042                 else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
1043                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1044                 else if (opts->ext_copy.data_len)
1045                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1046                 else
1047                         len = TCPOLEN_MPTCP_MPC_ACK;
1048
1049                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1050                                       MPTCP_SUPPORTED_VERSION,
1051                                       MPTCP_CAP_HMAC_SHA256);
1052
1053                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1054                     opts->suboptions))
1055                         goto mp_capable_done;
1056
1057                 put_unaligned_be64(opts->sndr_key, ptr);
1058                 ptr += 2;
1059                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1060                         goto mp_capable_done;
1061
1062                 put_unaligned_be64(opts->rcvr_key, ptr);
1063                 ptr += 2;
1064                 if (!opts->ext_copy.data_len)
1065                         goto mp_capable_done;
1066
1067                 put_unaligned_be32(opts->ext_copy.data_len << 16 |
1068                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1069                 ptr += 1;
1070         }
1071
1072 mp_capable_done:
1073         if ((OPTION_MPTCP_ADD_ADDR
1074 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1075              | OPTION_MPTCP_ADD_ADDR6
1076 #endif
1077             ) & opts->suboptions) {
1078                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1079                 u8 echo = MPTCP_ADDR_ECHO;
1080
1081 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1082                 if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions)
1083                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1084 #endif
1085
1086                 if (opts->ahmac) {
1087                         len += sizeof(opts->ahmac);
1088                         echo = 0;
1089                 }
1090
1091                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1092                                       len, echo, opts->addr_id);
1093                 if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1094                         memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4);
1095                         ptr += 1;
1096                 }
1097 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1098                 else if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) {
1099                         memcpy((u8 *)ptr, opts->addr6.s6_addr, 16);
1100                         ptr += 4;
1101                 }
1102 #endif
1103                 if (opts->ahmac) {
1104                         put_unaligned_be64(opts->ahmac, ptr);
1105                         ptr += 2;
1106                 }
1107         }
1108
1109         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1110                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1111                                       TCPOLEN_MPTCP_RM_ADDR_BASE,
1112                                       0, opts->rm_id);
1113         }
1114
1115         if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1116                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1117                                       TCPOLEN_MPTCP_MPJ_SYN,
1118                                       opts->backup, opts->join_id);
1119                 put_unaligned_be32(opts->token, ptr);
1120                 ptr += 1;
1121                 put_unaligned_be32(opts->nonce, ptr);
1122                 ptr += 1;
1123         }
1124
1125         if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1126                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1127                                       TCPOLEN_MPTCP_MPJ_SYNACK,
1128                                       opts->backup, opts->join_id);
1129                 put_unaligned_be64(opts->thmac, ptr);
1130                 ptr += 2;
1131                 put_unaligned_be32(opts->nonce, ptr);
1132                 ptr += 1;
1133         }
1134
1135         if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
1136                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1137                                       TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1138                 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1139                 ptr += 5;
1140         }
1141
1142         if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
1143                 struct mptcp_ext *mpext = &opts->ext_copy;
1144                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1145                 u8 flags = 0;
1146
1147                 if (mpext->use_ack) {
1148                         flags = MPTCP_DSS_HAS_ACK;
1149                         if (mpext->ack64) {
1150                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1151                                 flags |= MPTCP_DSS_ACK64;
1152                         } else {
1153                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1154                         }
1155                 }
1156
1157                 if (mpext->use_map) {
1158                         len += TCPOLEN_MPTCP_DSS_MAP64;
1159
1160                         /* Use only 64-bit mapping flags for now, add
1161                          * support for optional 32-bit mappings later.
1162                          */
1163                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1164                         if (mpext->data_fin)
1165                                 flags |= MPTCP_DSS_DATA_FIN;
1166                 }
1167
1168                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1169
1170                 if (mpext->use_ack) {
1171                         if (mpext->ack64) {
1172                                 put_unaligned_be64(mpext->data_ack, ptr);
1173                                 ptr += 2;
1174                         } else {
1175                                 put_unaligned_be32(mpext->data_ack32, ptr);
1176                                 ptr += 1;
1177                         }
1178                 }
1179
1180                 if (mpext->use_map) {
1181                         put_unaligned_be64(mpext->data_seq, ptr);
1182                         ptr += 2;
1183                         put_unaligned_be32(mpext->subflow_seq, ptr);
1184                         ptr += 1;
1185                         put_unaligned_be32(mpext->data_len << 16 |
1186                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1187                 }
1188         }
1189
1190         if (tp)
1191                 mptcp_set_rwin(tp);
1192 }