net/mptcp/options.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Multipath TCP
   3  *
   4  * Copyright (c) 2017 - 2019, Intel Corporation.
   5  */
   6
   7 #define pr_fmt(fmt) "MPTCP: " fmt
   8
   9 #include <linux/kernel.h>
  10 #include <crypto/sha2.h>
  11 #include <net/tcp.h>
  12 #include <net/mptcp.h>
  13 #include "protocol.h"
  14 #include "mib.h"
  15
  16 #include <trace/events/mptcp.h>
  17
  18 static bool mptcp_cap_flag_sha256(u8 flags)
  19 {
  20         return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
  21 }
  22
  23 static void mptcp_parse_option(const struct sk_buff *skb,
  24                                const unsigned char *ptr, int opsize,
  25                                struct mptcp_options_received *mp_opt)
  26 {
  27         u8 subtype = *ptr >> 4;
  28         int expected_opsize;
  29         u8 version;
  30         u8 flags;
  31         u8 i;
  32
  33         switch (subtype) {
  34         case MPTCPOPT_MP_CAPABLE:
  35                 /* strict size checking */
  36                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
  37                         if (skb->len > tcp_hdr(skb)->doff << 2)
  38                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
  39                         else
  40                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
  41                 } else {
  42                         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)
  43                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
  44                         else
  45                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
  46                 }
  47                 if (opsize != expected_opsize)
  48                         break;
  49
  50                 /* try to be gentle vs future versions on the initial syn */
  51                 version = *ptr++ & MPTCP_VERSION_MASK;
  52                 if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
  53                         if (version != MPTCP_SUPPORTED_VERSION)
  54                                 break;
  55                 } else if (version < MPTCP_SUPPORTED_VERSION) {
  56                         break;
  57                 }
  58
  59                 flags = *ptr++;
  60                 if (!mptcp_cap_flag_sha256(flags) ||
  61                     (flags & MPTCP_CAP_EXTENSIBILITY))
  62                         break;
  63
  64                 /* RFC 6824, Section 3.1:
  65                  * "For the Checksum Required bit (labeled "A"), if either
  66                  * host requires the use of checksums, checksums MUST be used.
  67                  * In other words, the only way for checksums not to be used
  68                  * is if both hosts in their SYNs set A=0."
  69                  *
  70                  * Section 3.3.0:
  71                  * "If a checksum is not present when its use has been
  72                  * negotiated, the receiver MUST close the subflow with a RST as
  73                  * it is considered broken."
  74                  *
  75                  * We don't implement DSS checksum - fall back to TCP.
  76                  */
  77                 if (flags & MPTCP_CAP_CHECKSUM_REQD)
  78                         break;
  79
  80                 mp_opt->mp_capable = 1;
  81                 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
  82                         mp_opt->sndr_key = get_unaligned_be64(ptr);
  83                         ptr += 8;
  84                 }
  85                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
  86                         mp_opt->rcvr_key = get_unaligned_be64(ptr);
  87                         ptr += 8;
  88                 }
  89                 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA) {
  90                         /* Section 3.1.:
  91                          * "the data parameters in a MP_CAPABLE are semantically
  92                          * equivalent to those in a DSS option and can be used
  93                          * interchangeably."
  94                          */
  95                         mp_opt->dss = 1;
  96                         mp_opt->use_map = 1;
  97                         mp_opt->mpc_map = 1;
  98                         mp_opt->data_len = get_unaligned_be16(ptr);
  99                         ptr += 2;
 100                 }
 101                 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d",
 102                          version, flags, opsize, mp_opt->sndr_key,
 103                          mp_opt->rcvr_key, mp_opt->data_len);
 104                 break;
 105
 106         case MPTCPOPT_MP_JOIN:
 107                 mp_opt->mp_join = 1;
 108                 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 109                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 110                         mp_opt->join_id = *ptr++;
 111                         mp_opt->token = get_unaligned_be32(ptr);
 112                         ptr += 4;
 113                         mp_opt->nonce = get_unaligned_be32(ptr);
 114                         ptr += 4;
 115                         pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
 116                                  mp_opt->backup, mp_opt->join_id,
 117                                  mp_opt->token, mp_opt->nonce);
 118                 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
 119                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 120                         mp_opt->join_id = *ptr++;
 121                         mp_opt->thmac = get_unaligned_be64(ptr);
 122                         ptr += 8;
 123                         mp_opt->nonce = get_unaligned_be32(ptr);
 124                         ptr += 4;
 125                         pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
 126                                  mp_opt->backup, mp_opt->join_id,
 127                                  mp_opt->thmac, mp_opt->nonce);
 128                 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 129                         ptr += 2;
 130                         memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 131                         pr_debug("MP_JOIN hmac");
 132                 } else {
 133                         pr_warn("MP_JOIN bad option size");
 134                         mp_opt->mp_join = 0;
 135                 }
 136                 break;
 137
 138         case MPTCPOPT_DSS:
 139                 pr_debug("DSS");
 140                 ptr++;
 141
 142                 /* we must clear 'mpc_map' be able to detect MP_CAPABLE
 143                  * map vs DSS map in mptcp_incoming_options(), and reconstruct
 144                  * map info accordingly
 145                  */
 146                 mp_opt->mpc_map = 0;
 147                 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 148                 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 149                 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 150                 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 151                 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 152                 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 153
 154                 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
 155                          mp_opt->data_fin, mp_opt->dsn64,
 156                          mp_opt->use_map, mp_opt->ack64,
 157                          mp_opt->use_ack);
 158
 159                 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 160
 161                 if (mp_opt->use_ack) {
 162                         if (mp_opt->ack64)
 163                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 164                         else
 165                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 166                 }
 167
 168                 if (mp_opt->use_map) {
 169                         if (mp_opt->dsn64)
 170                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 171                         else
 172                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 173                 }
 174
 175                 /* RFC 6824, Section 3.3:
 176                  * If a checksum is present, but its use had
 177                  * not been negotiated in the MP_CAPABLE handshake,
 178                  * the checksum field MUST be ignored.
 179                  */
 180                 if (opsize != expected_opsize &&
 181                     opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 182                         break;
 183
 184                 mp_opt->dss = 1;
 185
 186                 if (mp_opt->use_ack) {
 187                         if (mp_opt->ack64) {
 188                                 mp_opt->data_ack = get_unaligned_be64(ptr);
 189                                 ptr += 8;
 190                         } else {
 191                                 mp_opt->data_ack = get_unaligned_be32(ptr);
 192                                 ptr += 4;
 193                         }
 194
 195                         pr_debug("data_ack=%llu", mp_opt->data_ack);
 196                 }
 197
 198                 if (mp_opt->use_map) {
 199                         if (mp_opt->dsn64) {
 200                                 mp_opt->data_seq = get_unaligned_be64(ptr);
 201                                 ptr += 8;
 202                         } else {
 203                                 mp_opt->data_seq = get_unaligned_be32(ptr);
 204                                 ptr += 4;
 205                         }
 206
 207                         mp_opt->subflow_seq = get_unaligned_be32(ptr);
 208                         ptr += 4;
 209
 210                         mp_opt->data_len = get_unaligned_be16(ptr);
 211                         ptr += 2;
 212
 213                         pr_debug("data_seq=%llu subflow_seq=%u data_len=%u",
 214                                  mp_opt->data_seq, mp_opt->subflow_seq,
 215                                  mp_opt->data_len);
 216                 }
 217
 218                 break;
 219
 220         case MPTCPOPT_ADD_ADDR:
 221                 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 222                 if (!mp_opt->echo) {
 223                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 224                             opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 225                                 mp_opt->addr.family = AF_INET;
 226 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 227                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 228                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 229                                 mp_opt->addr.family = AF_INET6;
 230 #endif
 231                         else
 232                                 break;
 233                 } else {
 234                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 235                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 236                                 mp_opt->addr.family = AF_INET;
 237 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 238                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 239                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 240                                 mp_opt->addr.family = AF_INET6;
 241 #endif
 242                         else
 243                                 break;
 244                 }
 245
 246                 mp_opt->add_addr = 1;
 247                 mp_opt->addr.id = *ptr++;
 248                 if (mp_opt->addr.family == AF_INET) {
 249                         memcpy((u8 *)&mp_opt->addr.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->addr.port = htons(get_unaligned_be16(ptr));
 254                                 ptr += 2;
 255                         }
 256                 }
 257 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 258                 else {
 259                         memcpy(mp_opt->addr.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->addr.port = htons(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                 pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d",
 273                          (mp_opt->addr.family == AF_INET6) ? "6" : "",
 274                          mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
 275                 break;
 276
 277         case MPTCPOPT_RM_ADDR:
 278                 if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
 279                     opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
 280                         break;
 281
 282                 ptr++;
 283
 284                 mp_opt->rm_addr = 1;
 285                 mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
 286                 for (i = 0; i < mp_opt->rm_list.nr; i++)
 287                         mp_opt->rm_list.ids[i] = *ptr++;
 288                 pr_debug("RM_ADDR: rm_list_nr=%d", mp_opt->rm_list.nr);
 289                 break;
 290
 291         case MPTCPOPT_MP_PRIO:
 292                 if (opsize != TCPOLEN_MPTCP_PRIO)
 293                         break;
 294
 295                 mp_opt->mp_prio = 1;
 296                 mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
 297                 pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
 298                 break;
 299
 300         case MPTCPOPT_MP_FASTCLOSE:
 301                 if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 302                         break;
 303
 304                 ptr += 2;
 305                 mp_opt->rcvr_key = get_unaligned_be64(ptr);
 306                 ptr += 8;
 307                 mp_opt->fastclose = 1;
 308                 break;
 309
 310         case MPTCPOPT_RST:
 311                 if (opsize != TCPOLEN_MPTCP_RST)
 312                         break;
 313
 314                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 315                         break;
 316                 mp_opt->reset = 1;
 317                 flags = *ptr++;
 318                 mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
 319                 mp_opt->reset_reason = *ptr;
 320                 break;
 321
 322         default:
 323                 break;
 324         }
 325 }
 326
 327 void mptcp_get_options(const struct sk_buff *skb,
 328                        struct mptcp_options_received *mp_opt)
 329 {
 330         const struct tcphdr *th = tcp_hdr(skb);
 331         const unsigned char *ptr;
 332         int length;
 333
 334         /* initialize option status */
 335         mp_opt->mp_capable = 0;
 336         mp_opt->mp_join = 0;
 337         mp_opt->add_addr = 0;
 338         mp_opt->ahmac = 0;
 339         mp_opt->fastclose = 0;
 340         mp_opt->addr.port = 0;
 341         mp_opt->rm_addr = 0;
 342         mp_opt->dss = 0;
 343         mp_opt->mp_prio = 0;
 344         mp_opt->reset = 0;
 345
 346         length = (th->doff * 4) - sizeof(struct tcphdr);
 347         ptr = (const unsigned char *)(th + 1);
 348
 349         while (length > 0) {
 350                 int opcode = *ptr++;
 351                 int opsize;
 352
 353                 switch (opcode) {
 354                 case TCPOPT_EOL:
 355                         return;
 356                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 357                         length--;
 358                         continue;
 359                 default:
 360                         opsize = *ptr++;
 361                         if (opsize < 2) /* "silly options" */
 362                                 return;
 363                         if (opsize > length)
 364                                 return; /* don't parse partial options */
 365                         if (opcode == TCPOPT_MPTCP)
 366                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 367                         ptr += opsize - 2;
 368                         length -= opsize;
 369                 }
 370         }
 371 }
 372
 373 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 374                        unsigned int *size, struct mptcp_out_options *opts)
 375 {
 376         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 377
 378         /* we will use snd_isn to detect first pkt [re]transmission
 379          * in mptcp_established_options_mp()
 380          */
 381         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 382         if (subflow->request_mptcp) {
 383                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 384                 *size = TCPOLEN_MPTCP_MPC_SYN;
 385                 return true;
 386         } else if (subflow->request_join) {
 387                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 388                          subflow->local_nonce);
 389                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 390                 opts->join_id = subflow->local_id;
 391                 opts->token = subflow->remote_token;
 392                 opts->nonce = subflow->local_nonce;
 393                 opts->backup = subflow->request_bkup;
 394                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 395                 return true;
 396         }
 397         return false;
 398 }
 399
 400 /* MP_JOIN client subflow must wait for 4th ack before sending any data:
 401  * TCP can't schedule delack timer before the subflow is fully established.
 402  * MPTCP uses the delack timer to do 3rd ack retransmissions
 403  */
 404 static void schedule_3rdack_retransmission(struct sock *sk)
 405 {
 406         struct inet_connection_sock *icsk = inet_csk(sk);
 407         struct tcp_sock *tp = tcp_sk(sk);
 408         unsigned long timeout;
 409
 410         /* reschedule with a timeout above RTT, as we must look only for drop */
 411         if (tp->srtt_us)
 412                 timeout = tp->srtt_us << 1;
 413         else
 414                 timeout = TCP_TIMEOUT_INIT;
 415
 416         WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 417         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 418         icsk->icsk_ack.timeout = timeout;
 419         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 420 }
 421
 422 static void clear_3rdack_retransmission(struct sock *sk)
 423 {
 424         struct inet_connection_sock *icsk = inet_csk(sk);
 425
 426         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 427         icsk->icsk_ack.timeout = 0;
 428         icsk->icsk_ack.ato = 0;
 429         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 430 }
 431
 432 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 433                                          bool snd_data_fin_enable,
 434                                          unsigned int *size,
 435                                          unsigned int remaining,
 436                                          struct mptcp_out_options *opts)
 437 {
 438         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 439         struct mptcp_ext *mpext;
 440         unsigned int data_len;
 441
 442         /* When skb is not available, we better over-estimate the emitted
 443          * options len. A full DSS option (28 bytes) is longer than
 444          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 445          * tell the caller to defer the estimate to
 446          * mptcp_established_options_dss(), which will reserve enough space.
 447          */
 448         if (!skb)
 449                 return false;
 450
 451         /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
 452         if (subflow->fully_established || snd_data_fin_enable ||
 453             subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 454             sk->sk_state != TCP_ESTABLISHED)
 455                 return false;
 456
 457         if (subflow->mp_capable) {
 458                 mpext = mptcp_get_ext(skb);
 459                 data_len = mpext ? mpext->data_len : 0;
 460
 461                 /* we will check ext_copy.data_len in mptcp_write_options() to
 462                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 463                  * TCPOLEN_MPTCP_MPC_ACK
 464                  */
 465                 opts->ext_copy.data_len = data_len;
 466                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 467                 opts->sndr_key = subflow->local_key;
 468                 opts->rcvr_key = subflow->remote_key;
 469
 470                 /* Section 3.1.
 471                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 472                  * packets that start the first subflow of an MPTCP connection,
 473                  * as well as the first packet that carries data
 474                  */
 475                 if (data_len > 0)
 476                         *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
 477                 else
 478                         *size = TCPOLEN_MPTCP_MPC_ACK;
 479
 480                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 481                          subflow, subflow->local_key, subflow->remote_key,
 482                          data_len);
 483
 484                 return true;
 485         } else if (subflow->mp_join) {
 486                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 487                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 488                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 489                 pr_debug("subflow=%p", subflow);
 490
 491                 schedule_3rdack_retransmission(sk);
 492                 return true;
 493         }
 494         return false;
 495 }
 496
 497 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 498                                  struct sk_buff *skb, struct mptcp_ext *ext)
 499 {
 500         /* The write_seq value has already been incremented, so the actual
 501          * sequence number for the DATA_FIN is one less.
 502          */
 503         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 504
 505         if (!ext->use_map || !skb->len) {
 506                 /* RFC6824 requires a DSS mapping with specific values
 507                  * if DATA_FIN is set but no data payload is mapped
 508                  */
 509                 ext->data_fin = 1;
 510                 ext->use_map = 1;
 511                 ext->dsn64 = 1;
 512                 ext->data_seq = data_fin_tx_seq;
 513                 ext->subflow_seq = 0;
 514                 ext->data_len = 1;
 515         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 516                 /* If there's an existing DSS mapping and it is the
 517                  * final mapping, DATA_FIN consumes 1 additional byte of
 518                  * mapping space.
 519                  */
 520                 ext->data_fin = 1;
 521                 ext->data_len++;
 522         }
 523 }
 524
 525 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 526                                           bool snd_data_fin_enable,
 527                                           unsigned int *size,
 528                                           unsigned int remaining,
 529                                           struct mptcp_out_options *opts)
 530 {
 531         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 532         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 533         unsigned int dss_size = 0;
 534         struct mptcp_ext *mpext;
 535         unsigned int ack_size;
 536         bool ret = false;
 537         u64 ack_seq;
 538
 539         mpext = skb ? mptcp_get_ext(skb) : NULL;
 540
 541         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 542                 unsigned int map_size;
 543
 544                 map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 545
 546                 remaining -= map_size;
 547                 dss_size = map_size;
 548                 if (mpext)
 549                         opts->ext_copy = *mpext;
 550
 551                 if (skb && snd_data_fin_enable)
 552                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 553                 ret = true;
 554         }
 555
 556         /* passive sockets msk will set the 'can_ack' after accept(), even
 557          * if the first subflow may have the already the remote key handy
 558          */
 559         opts->ext_copy.use_ack = 0;
 560         if (!READ_ONCE(msk->can_ack)) {
 561                 *size = ALIGN(dss_size, 4);
 562                 return ret;
 563         }
 564
 565         ack_seq = READ_ONCE(msk->ack_seq);
 566         if (READ_ONCE(msk->use_64bit_ack)) {
 567                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 568                 opts->ext_copy.data_ack = ack_seq;
 569                 opts->ext_copy.ack64 = 1;
 570         } else {
 571                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 572                 opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
 573                 opts->ext_copy.ack64 = 0;
 574         }
 575         opts->ext_copy.use_ack = 1;
 576         WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 577
 578         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 579         if (dss_size == 0)
 580                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 581
 582         dss_size += ack_size;
 583
 584         *size = ALIGN(dss_size, 4);
 585         return true;
 586 }
 587
 588 static u64 add_addr_generate_hmac(u64 key1, u64 key2,
 589                                   struct mptcp_addr_info *addr)
 590 {
 591         u16 port = ntohs(addr->port);
 592         u8 hmac[SHA256_DIGEST_SIZE];
 593         u8 msg[19];
 594         int i = 0;
 595
 596         msg[i++] = addr->id;
 597         if (addr->family == AF_INET) {
 598                 memcpy(&msg[i], &addr->addr.s_addr, 4);
 599                 i += 4;
 600         }
 601 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 602         else if (addr->family == AF_INET6) {
 603                 memcpy(&msg[i], &addr->addr6.s6_addr, 16);
 604                 i += 16;
 605         }
 606 #endif
 607         msg[i++] = port >> 8;
 608         msg[i++] = port & 0xFF;
 609
 610         mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
 611
 612         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 613 }
 614
 615 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 616                                                unsigned int *size,
 617                                                unsigned int remaining,
 618                                                struct mptcp_out_options *opts)
 619 {
 620         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 621         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 622         bool drop_other_suboptions = false;
 623         unsigned int opt_size = *size;
 624         bool echo;
 625         bool port;
 626         int len;
 627
 628         if ((mptcp_pm_should_add_signal_ipv6(msk) ||
 629              mptcp_pm_should_add_signal_port(msk) ||
 630              mptcp_pm_should_add_signal_echo(msk)) &&
 631             skb && skb_is_tcp_pure_ack(skb)) {
 632                 pr_debug("drop other suboptions");
 633                 opts->suboptions = 0;
 634                 opts->ext_copy.use_ack = 0;
 635                 opts->ext_copy.use_map = 0;
 636                 remaining += opt_size;
 637                 drop_other_suboptions = true;
 638         }
 639
 640         if (!mptcp_pm_should_add_signal(msk) ||
 641             !(mptcp_pm_add_addr_signal(msk, remaining, &opts->addr, &echo, &port)))
 642                 return false;
 643
 644         len = mptcp_add_addr_len(opts->addr.family, echo, port);
 645         if (remaining < len)
 646                 return false;
 647
 648         *size = len;
 649         if (drop_other_suboptions)
 650                 *size -= opt_size;
 651         opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 652         if (!echo) {
 653                 opts->ahmac = add_addr_generate_hmac(msk->local_key,
 654                                                      msk->remote_key,
 655                                                      &opts->addr);
 656         }
 657         pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d",
 658                  opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
 659
 660         return true;
 661 }
 662
 663 static bool mptcp_established_options_rm_addr(struct sock *sk,
 664                                               unsigned int *size,
 665                                               unsigned int remaining,
 666                                               struct mptcp_out_options *opts)
 667 {
 668         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 669         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 670         struct mptcp_rm_list rm_list;
 671         int i, len;
 672
 673         if (!mptcp_pm_should_rm_signal(msk) ||
 674             !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
 675                 return false;
 676
 677         len = mptcp_rm_addr_len(&rm_list);
 678         if (len < 0)
 679                 return false;
 680         if (remaining < len)
 681                 return false;
 682
 683         *size = len;
 684         opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 685         opts->rm_list = rm_list;
 686
 687         for (i = 0; i < opts->rm_list.nr; i++)
 688                 pr_debug("rm_list_ids[%d]=%d", i, opts->rm_list.ids[i]);
 689
 690         return true;
 691 }
 692
 693 static bool mptcp_established_options_mp_prio(struct sock *sk,
 694                                               unsigned int *size,
 695                                               unsigned int remaining,
 696                                               struct mptcp_out_options *opts)
 697 {
 698         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 699
 700         if (!subflow->send_mp_prio)
 701                 return false;
 702
 703         /* account for the trailing 'nop' option */
 704         if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
 705                 return false;
 706
 707         *size = TCPOLEN_MPTCP_PRIO_ALIGN;
 708         opts->suboptions |= OPTION_MPTCP_PRIO;
 709         opts->backup = subflow->request_bkup;
 710
 711         pr_debug("prio=%d", opts->backup);
 712
 713         return true;
 714 }
 715
 716 static noinline void mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
 717                                                    unsigned int *size,
 718                                                    unsigned int remaining,
 719                                                    struct mptcp_out_options *opts)
 720 {
 721         const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 722
 723         if (remaining < TCPOLEN_MPTCP_RST)
 724                 return;
 725
 726         *size = TCPOLEN_MPTCP_RST;
 727         opts->suboptions |= OPTION_MPTCP_RST;
 728         opts->reset_transient = subflow->reset_transient;
 729         opts->reset_reason = subflow->reset_reason;
 730 }
 731
 732 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 733                                unsigned int *size, unsigned int remaining,
 734                                struct mptcp_out_options *opts)
 735 {
 736         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 737         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 738         unsigned int opt_size = 0;
 739         bool snd_data_fin;
 740         bool ret = false;
 741
 742         opts->suboptions = 0;
 743
 744         if (unlikely(__mptcp_check_fallback(msk)))
 745                 return false;
 746
 747         if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 748                 mptcp_established_options_rst(sk, skb, size, remaining, opts);
 749                 return true;
 750         }
 751
 752         snd_data_fin = mptcp_data_fin_enabled(msk);
 753         if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 754                 ret = true;
 755         else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 756                 ret = true;
 757
 758         /* we reserved enough space for the above options, and exceeding the
 759          * TCP option space would be fatal
 760          */
 761         if (WARN_ON_ONCE(opt_size > remaining))
 762                 return false;
 763
 764         *size += opt_size;
 765         remaining -= opt_size;
 766         if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
 767                 *size += opt_size;
 768                 remaining -= opt_size;
 769                 ret = true;
 770         } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 771                 *size += opt_size;
 772                 remaining -= opt_size;
 773                 ret = true;
 774         }
 775
 776         if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
 777                 *size += opt_size;
 778                 remaining -= opt_size;
 779                 ret = true;
 780         }
 781
 782         return ret;
 783 }
 784
 785 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 786                           struct mptcp_out_options *opts)
 787 {
 788         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 789
 790         if (subflow_req->mp_capable) {
 791                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 792                 opts->sndr_key = subflow_req->local_key;
 793                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 794                 pr_debug("subflow_req=%p, local_key=%llu",
 795                          subflow_req, subflow_req->local_key);
 796                 return true;
 797         } else if (subflow_req->mp_join) {
 798                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 799                 opts->backup = subflow_req->backup;
 800                 opts->join_id = subflow_req->local_id;
 801                 opts->thmac = subflow_req->thmac;
 802                 opts->nonce = subflow_req->local_nonce;
 803                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 804                          subflow_req, opts->backup, opts->join_id,
 805                          opts->thmac, opts->nonce);
 806                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 807                 return true;
 808         }
 809         return false;
 810 }
 811
 812 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 813                                     struct mptcp_subflow_context *subflow,
 814                                     struct sk_buff *skb,
 815                                     struct mptcp_options_received *mp_opt)
 816 {
 817         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 818          * will make the subflow fully established
 819          */
 820         if (likely(subflow->fully_established)) {
 821                 /* on passive sockets, check for 3rd ack retransmission
 822                  * note that msk is always set by subflow_syn_recv_sock()
 823                  * for mp_join subflows
 824                  */
 825                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 826                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 827                     subflow->mp_join && mp_opt->mp_join &&
 828                     READ_ONCE(msk->pm.server_side))
 829                         tcp_send_ack(ssk);
 830                 goto fully_established;
 831         }
 832
 833         /* we must process OoO packets before the first subflow is fully
 834          * established. OoO packets are instead a protocol violation
 835          * for MP_JOIN subflows as the peer must not send any data
 836          * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 837          */
 838         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 839                 if (subflow->mp_join)
 840                         goto reset;
 841                 return subflow->mp_capable;
 842         }
 843
 844         if (mp_opt->dss && mp_opt->use_ack) {
 845                 /* subflows are fully established as soon as we get any
 846                  * additional ack.
 847                  */
 848                 subflow->fully_established = 1;
 849                 WRITE_ONCE(msk->fully_established, true);
 850                 goto fully_established;
 851         }
 852
 853         if (mp_opt->add_addr) {
 854                 WRITE_ONCE(msk->fully_established, true);
 855                 return true;
 856         }
 857
 858         /* If the first established packet does not contain MP_CAPABLE + data
 859          * then fallback to TCP. Fallback scenarios requires a reset for
 860          * MP_JOIN subflows.
 861          */
 862         if (!mp_opt->mp_capable) {
 863                 if (subflow->mp_join)
 864                         goto reset;
 865                 subflow->mp_capable = 0;
 866                 pr_fallback(msk);
 867                 __mptcp_do_fallback(msk);
 868                 return false;
 869         }
 870
 871         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 872                 pr_warn_once("bogus mpc option on established client sk");
 873         mptcp_subflow_fully_established(subflow, mp_opt);
 874
 875 fully_established:
 876         /* if the subflow is not already linked into the conn_list, we can't
 877          * notify the PM: this subflow is still on the listener queue
 878          * and the PM possibly acquiring the subflow lock could race with
 879          * the listener close
 880          */
 881         if (likely(subflow->pm_notified) || list_empty(&subflow->node))
 882                 return true;
 883
 884         subflow->pm_notified = 1;
 885         if (subflow->mp_join) {
 886                 clear_3rdack_retransmission(ssk);
 887                 mptcp_pm_subflow_established(msk);
 888         } else {
 889                 mptcp_pm_fully_established(msk, ssk, GFP_ATOMIC);
 890         }
 891         return true;
 892
 893 reset:
 894         mptcp_subflow_reset(ssk);
 895         return false;
 896 }
 897
 898 static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)
 899 {
 900         u32 old_ack32, cur_ack32;
 901
 902         if (use_64bit)
 903                 return cur_ack;
 904
 905         old_ack32 = (u32)old_ack;
 906         cur_ack32 = (u32)cur_ack;
 907         cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32;
 908         if (unlikely(before(cur_ack32, old_ack32)))
 909                 return cur_ack + (1LL << 32);
 910         return cur_ack;
 911 }
 912
 913 static void ack_update_msk(struct mptcp_sock *msk,
 914                            struct sock *ssk,
 915                            struct mptcp_options_received *mp_opt)
 916 {
 917         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
 918         struct sock *sk = (struct sock *)msk;
 919         u64 old_snd_una;
 920
 921         mptcp_data_lock(sk);
 922
 923         /* avoid ack expansion on update conflict, to reduce the risk of
 924          * wrongly expanding to a future ack sequence number, which is way
 925          * more dangerous than missing an ack
 926          */
 927         old_snd_una = msk->snd_una;
 928         new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 929
 930         /* ACK for data not even sent yet? Ignore. */
 931         if (after64(new_snd_una, snd_nxt))
 932                 new_snd_una = old_snd_una;
 933
 934         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
 935
 936         if (after64(new_wnd_end, msk->wnd_end))
 937                 msk->wnd_end = new_wnd_end;
 938
 939         /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
 940         if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
 941                 __mptcp_check_push(sk, ssk);
 942
 943         if (after64(new_snd_una, old_snd_una)) {
 944                 msk->snd_una = new_snd_una;
 945                 __mptcp_data_acked(sk);
 946         }
 947         mptcp_data_unlock(sk);
 948
 949         trace_ack_update_msk(mp_opt->data_ack,
 950                              old_snd_una, new_snd_una,
 951                              new_wnd_end, msk->wnd_end);
 952 }
 953
 954 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
 955 {
 956         /* Skip if DATA_FIN was already received.
 957          * If updating simultaneously with the recvmsg loop, values
 958          * should match. If they mismatch, the peer is misbehaving and
 959          * we will prefer the most recent information.
 960          */
 961         if (READ_ONCE(msk->rcv_data_fin))
 962                 return false;
 963
 964         WRITE_ONCE(msk->rcv_data_fin_seq,
 965                    expand_ack(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
 966         WRITE_ONCE(msk->rcv_data_fin, 1);
 967
 968         return true;
 969 }
 970
 971 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
 972                                 struct mptcp_options_received *mp_opt)
 973 {
 974         u64 hmac = 0;
 975
 976         if (mp_opt->echo)
 977                 return true;
 978
 979         hmac = add_addr_generate_hmac(msk->remote_key,
 980                                       msk->local_key,
 981                                       &mp_opt->addr);
 982
 983         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
 984                  msk, (unsigned long long)hmac,
 985                  (unsigned long long)mp_opt->ahmac);
 986
 987         return hmac == mp_opt->ahmac;
 988 }
 989
 990 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 991 {
 992         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 993         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 994         struct mptcp_options_received mp_opt;
 995         struct mptcp_ext *mpext;
 996
 997         if (__mptcp_check_fallback(msk)) {
 998                 /* Keep it simple and unconditionally trigger send data cleanup and
 999                  * pending queue spooling. We will need to acquire the data lock
1000                  * for more accurate checks, and once the lock is acquired, such
1001                  * helpers are cheap.
1002                  */
1003                 mptcp_data_lock(subflow->conn);
1004                 if (sk_stream_memory_free(sk))
1005                         __mptcp_check_push(subflow->conn, sk);
1006                 __mptcp_data_acked(subflow->conn);
1007                 mptcp_data_unlock(subflow->conn);
1008                 return;
1009         }
1010
1011         mptcp_get_options(skb, &mp_opt);
1012         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1013                 return;
1014
1015         if (mp_opt.fastclose &&
1016             msk->local_key == mp_opt.rcvr_key) {
1017                 WRITE_ONCE(msk->rcv_fastclose, true);
1018                 mptcp_schedule_work((struct sock *)msk);
1019         }
1020
1021         if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
1022                 if (!mp_opt.echo) {
1023                         mptcp_pm_add_addr_received(msk, &mp_opt.addr);
1024                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1025                 } else {
1026                         mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1027                         mptcp_pm_del_add_timer(msk, &mp_opt.addr);
1028                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1029                 }
1030
1031                 if (mp_opt.addr.port)
1032                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1033
1034                 mp_opt.add_addr = 0;
1035         }
1036
1037         if (mp_opt.rm_addr) {
1038                 mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1039                 mp_opt.rm_addr = 0;
1040         }
1041
1042         if (mp_opt.mp_prio) {
1043                 mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1044                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1045                 mp_opt.mp_prio = 0;
1046         }
1047
1048         if (mp_opt.reset) {
1049                 subflow->reset_seen = 1;
1050                 subflow->reset_reason = mp_opt.reset_reason;
1051                 subflow->reset_transient = mp_opt.reset_transient;
1052         }
1053
1054         if (!mp_opt.dss)
1055                 return;
1056
1057         /* we can't wait for recvmsg() to update the ack_seq, otherwise
1058          * monodirectional flows will stuck
1059          */
1060         if (mp_opt.use_ack)
1061                 ack_update_msk(msk, sk, &mp_opt);
1062
1063         /* Zero-data-length packets are dropped by the caller and not
1064          * propagated to the MPTCP layer, so the skb extension does not
1065          * need to be allocated or populated. DATA_FIN information, if
1066          * present, needs to be updated here before the skb is freed.
1067          */
1068         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1069                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1070                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
1071                     schedule_work(&msk->work))
1072                         sock_hold(subflow->conn);
1073
1074                 return;
1075         }
1076
1077         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1078         if (!mpext)
1079                 return;
1080
1081         memset(mpext, 0, sizeof(*mpext));
1082
1083         if (mp_opt.use_map) {
1084                 if (mp_opt.mpc_map) {
1085                         /* this is an MP_CAPABLE carrying MPTCP data
1086                          * we know this map the first chunk of data
1087                          */
1088                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1089                                              &mpext->data_seq);
1090                         mpext->data_seq++;
1091                         mpext->subflow_seq = 1;
1092                         mpext->dsn64 = 1;
1093                         mpext->mpc_map = 1;
1094                         mpext->data_fin = 0;
1095                 } else {
1096                         mpext->data_seq = mp_opt.data_seq;
1097                         mpext->subflow_seq = mp_opt.subflow_seq;
1098                         mpext->dsn64 = mp_opt.dsn64;
1099                         mpext->data_fin = mp_opt.data_fin;
1100                 }
1101                 mpext->data_len = mp_opt.data_len;
1102                 mpext->use_map = 1;
1103         }
1104 }
1105
1106 static void mptcp_set_rwin(const struct tcp_sock *tp)
1107 {
1108         const struct sock *ssk = (const struct sock *)tp;
1109         const struct mptcp_subflow_context *subflow;
1110         struct mptcp_sock *msk;
1111         u64 ack_seq;
1112
1113         subflow = mptcp_subflow_ctx(ssk);
1114         msk = mptcp_sk(subflow->conn);
1115
1116         ack_seq = READ_ONCE(msk->ack_seq) + tp->rcv_wnd;
1117
1118         if (after64(ack_seq, READ_ONCE(msk->rcv_wnd_sent)))
1119                 WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
1120 }
1121
1122 void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
1123                          struct mptcp_out_options *opts)
1124 {
1125         if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
1126              OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
1127                 u8 len;
1128
1129                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
1130                         len = TCPOLEN_MPTCP_MPC_SYN;
1131                 else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
1132                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1133                 else if (opts->ext_copy.data_len)
1134                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1135                 else
1136                         len = TCPOLEN_MPTCP_MPC_ACK;
1137
1138                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1139                                       MPTCP_SUPPORTED_VERSION,
1140                                       MPTCP_CAP_HMAC_SHA256);
1141
1142                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1143                     opts->suboptions))
1144                         goto mp_capable_done;
1145
1146                 put_unaligned_be64(opts->sndr_key, ptr);
1147                 ptr += 2;
1148                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1149                         goto mp_capable_done;
1150
1151                 put_unaligned_be64(opts->rcvr_key, ptr);
1152                 ptr += 2;
1153                 if (!opts->ext_copy.data_len)
1154                         goto mp_capable_done;
1155
1156                 put_unaligned_be32(opts->ext_copy.data_len << 16 |
1157                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1158                 ptr += 1;
1159         }
1160
1161 mp_capable_done:
1162         if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1163                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1164                 u8 echo = MPTCP_ADDR_ECHO;
1165
1166 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1167                 if (opts->addr.family == AF_INET6)
1168                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1169 #endif
1170
1171                 if (opts->addr.port)
1172                         len += TCPOLEN_MPTCP_PORT_LEN;
1173
1174                 if (opts->ahmac) {
1175                         len += sizeof(opts->ahmac);
1176                         echo = 0;
1177                 }
1178
1179                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1180                                       len, echo, opts->addr.id);
1181                 if (opts->addr.family == AF_INET) {
1182                         memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1183                         ptr += 1;
1184                 }
1185 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1186                 else if (opts->addr.family == AF_INET6) {
1187                         memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1188                         ptr += 4;
1189                 }
1190 #endif
1191
1192                 if (!opts->addr.port) {
1193                         if (opts->ahmac) {
1194                                 put_unaligned_be64(opts->ahmac, ptr);
1195                                 ptr += 2;
1196                         }
1197                 } else {
1198                         u16 port = ntohs(opts->addr.port);
1199
1200                         if (opts->ahmac) {
1201                                 u8 *bptr = (u8 *)ptr;
1202
1203                                 put_unaligned_be16(port, bptr);
1204                                 bptr += 2;
1205                                 put_unaligned_be64(opts->ahmac, bptr);
1206                                 bptr += 8;
1207                                 put_unaligned_be16(TCPOPT_NOP << 8 |
1208                                                    TCPOPT_NOP, bptr);
1209
1210                                 ptr += 3;
1211                         } else {
1212                                 put_unaligned_be32(port << 16 |
1213                                                    TCPOPT_NOP << 8 |
1214                                                    TCPOPT_NOP, ptr);
1215                                 ptr += 1;
1216                         }
1217                 }
1218         }
1219
1220         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1221                 u8 i = 1;
1222
1223                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1224                                       TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1225                                       0, opts->rm_list.ids[0]);
1226
1227                 while (i < opts->rm_list.nr) {
1228                         u8 id1, id2, id3, id4;
1229
1230                         id1 = opts->rm_list.ids[i];
1231                         id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1232                         id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1233                         id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1234                         put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1235                         ptr += 1;
1236                         i += 4;
1237                 }
1238         }
1239
1240         if (OPTION_MPTCP_PRIO & opts->suboptions) {
1241                 const struct sock *ssk = (const struct sock *)tp;
1242                 struct mptcp_subflow_context *subflow;
1243
1244                 subflow = mptcp_subflow_ctx(ssk);
1245                 subflow->send_mp_prio = 0;
1246
1247                 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1248                                       TCPOLEN_MPTCP_PRIO,
1249                                       opts->backup, TCPOPT_NOP);
1250         }
1251
1252         if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1253                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1254                                       TCPOLEN_MPTCP_MPJ_SYN,
1255                                       opts->backup, opts->join_id);
1256                 put_unaligned_be32(opts->token, ptr);
1257                 ptr += 1;
1258                 put_unaligned_be32(opts->nonce, ptr);
1259                 ptr += 1;
1260         }
1261
1262         if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1263                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1264                                       TCPOLEN_MPTCP_MPJ_SYNACK,
1265                                       opts->backup, opts->join_id);
1266                 put_unaligned_be64(opts->thmac, ptr);
1267                 ptr += 2;
1268                 put_unaligned_be32(opts->nonce, ptr);
1269                 ptr += 1;
1270         }
1271
1272         if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
1273                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1274                                       TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1275                 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1276                 ptr += 5;
1277         }
1278
1279         if (OPTION_MPTCP_RST & opts->suboptions)
1280                 *ptr++ = mptcp_option(MPTCPOPT_RST,
1281                                       TCPOLEN_MPTCP_RST,
1282                                       opts->reset_transient,
1283                                       opts->reset_reason);
1284
1285         if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
1286                 struct mptcp_ext *mpext = &opts->ext_copy;
1287                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1288                 u8 flags = 0;
1289
1290                 if (mpext->use_ack) {
1291                         flags = MPTCP_DSS_HAS_ACK;
1292                         if (mpext->ack64) {
1293                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1294                                 flags |= MPTCP_DSS_ACK64;
1295                         } else {
1296                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1297                         }
1298                 }
1299
1300                 if (mpext->use_map) {
1301                         len += TCPOLEN_MPTCP_DSS_MAP64;
1302
1303                         /* Use only 64-bit mapping flags for now, add
1304                          * support for optional 32-bit mappings later.
1305                          */
1306                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1307                         if (mpext->data_fin)
1308                                 flags |= MPTCP_DSS_DATA_FIN;
1309                 }
1310
1311                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1312
1313                 if (mpext->use_ack) {
1314                         if (mpext->ack64) {
1315                                 put_unaligned_be64(mpext->data_ack, ptr);
1316                                 ptr += 2;
1317                         } else {
1318                                 put_unaligned_be32(mpext->data_ack32, ptr);
1319                                 ptr += 1;
1320                         }
1321                 }
1322
1323                 if (mpext->use_map) {
1324                         put_unaligned_be64(mpext->data_seq, ptr);
1325                         ptr += 2;
1326                         put_unaligned_be32(mpext->subflow_seq, ptr);
1327                         ptr += 1;
1328                         put_unaligned_be32(mpext->data_len << 16 |
1329                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1330                 }
1331         }
1332
1333         if (tp)
1334                 mptcp_set_rwin(tp);
1335 }
1336
1337 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1338 {
1339         const struct mptcp_ext *ext = mptcp_get_ext(skb);
1340         u8 flags, reason;
1341
1342         if (ext) {
1343                 flags = ext->reset_transient;
1344                 reason = ext->reset_reason;
1345
1346                 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1347                                     flags, reason);
1348         }
1349
1350         return htonl(0u);
1351 }
1352 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);