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
  48                 /* Cfr RFC 8684 Section 3.3.0:
  49                  * If a checksum is present but its use had
  50                  * not been negotiated in the MP_CAPABLE handshake, the receiver MUST
  51                  * close the subflow with a RST, as it is not behaving as negotiated.
  52                  * If a checksum is not present when its use has been negotiated, the
  53                  * receiver MUST close the subflow with a RST, as it is considered
  54                  * broken
  55                  * We parse even option with mismatching csum presence, so that
  56                  * later in subflow_data_ready we can trigger the reset.
  57                  */
  58                 if (opsize != expected_opsize &&
  59                     (expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA ||
  60                      opsize != TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM))
  61                         break;
  62
  63                 /* try to be gentle vs future versions on the initial syn */
  64                 version = *ptr++ & MPTCP_VERSION_MASK;
  65                 if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
  66                         if (version != MPTCP_SUPPORTED_VERSION)
  67                                 break;
  68                 } else if (version < MPTCP_SUPPORTED_VERSION) {
  69                         break;
  70                 }
  71
  72                 flags = *ptr++;
  73                 if (!mptcp_cap_flag_sha256(flags) ||
  74                     (flags & MPTCP_CAP_EXTENSIBILITY))
  75                         break;
  76
  77                 /* RFC 6824, Section 3.1:
  78                  * "For the Checksum Required bit (labeled "A"), if either
  79                  * host requires the use of checksums, checksums MUST be used.
  80                  * In other words, the only way for checksums not to be used
  81                  * is if both hosts in their SYNs set A=0."
  82                  */
  83                 if (flags & MPTCP_CAP_CHECKSUM_REQD)
  84                         mp_opt->csum_reqd = 1;
  85
  86                 if (flags & MPTCP_CAP_DENY_JOIN_ID0)
  87                         mp_opt->deny_join_id0 = 1;
  88
  89                 mp_opt->mp_capable = 1;
  90                 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
  91                         mp_opt->sndr_key = get_unaligned_be64(ptr);
  92                         ptr += 8;
  93                 }
  94                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
  95                         mp_opt->rcvr_key = get_unaligned_be64(ptr);
  96                         ptr += 8;
  97                 }
  98                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK_DATA) {
  99                         /* Section 3.1.:
 100                          * "the data parameters in a MP_CAPABLE are semantically
 101                          * equivalent to those in a DSS option and can be used
 102                          * interchangeably."
 103                          */
 104                         mp_opt->dss = 1;
 105                         mp_opt->use_map = 1;
 106                         mp_opt->mpc_map = 1;
 107                         mp_opt->data_len = get_unaligned_be16(ptr);
 108                         ptr += 2;
 109                 }
 110                 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
 111                         mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
 112                         mp_opt->csum_reqd = 1;
 113                         ptr += 2;
 114                 }
 115                 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u",
 116                          version, flags, opsize, mp_opt->sndr_key,
 117                          mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum);
 118                 break;
 119
 120         case MPTCPOPT_MP_JOIN:
 121                 mp_opt->mp_join = 1;
 122                 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 123                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 124                         mp_opt->join_id = *ptr++;
 125                         mp_opt->token = get_unaligned_be32(ptr);
 126                         ptr += 4;
 127                         mp_opt->nonce = get_unaligned_be32(ptr);
 128                         ptr += 4;
 129                         pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
 130                                  mp_opt->backup, mp_opt->join_id,
 131                                  mp_opt->token, mp_opt->nonce);
 132                 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
 133                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 134                         mp_opt->join_id = *ptr++;
 135                         mp_opt->thmac = get_unaligned_be64(ptr);
 136                         ptr += 8;
 137                         mp_opt->nonce = get_unaligned_be32(ptr);
 138                         ptr += 4;
 139                         pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
 140                                  mp_opt->backup, mp_opt->join_id,
 141                                  mp_opt->thmac, mp_opt->nonce);
 142                 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 143                         ptr += 2;
 144                         memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 145                         pr_debug("MP_JOIN hmac");
 146                 } else {
 147                         mp_opt->mp_join = 0;
 148                 }
 149                 break;
 150
 151         case MPTCPOPT_DSS:
 152                 pr_debug("DSS");
 153                 ptr++;
 154
 155                 /* we must clear 'mpc_map' be able to detect MP_CAPABLE
 156                  * map vs DSS map in mptcp_incoming_options(), and reconstruct
 157                  * map info accordingly
 158                  */
 159                 mp_opt->mpc_map = 0;
 160                 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 161                 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 162                 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 163                 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 164                 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 165                 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 166
 167                 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
 168                          mp_opt->data_fin, mp_opt->dsn64,
 169                          mp_opt->use_map, mp_opt->ack64,
 170                          mp_opt->use_ack);
 171
 172                 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 173
 174                 if (mp_opt->use_ack) {
 175                         if (mp_opt->ack64)
 176                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 177                         else
 178                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 179                 }
 180
 181                 if (mp_opt->use_map) {
 182                         if (mp_opt->dsn64)
 183                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 184                         else
 185                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 186                 }
 187
 188                 /* Always parse any csum presence combination, we will enforce
 189                  * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
 190                  */
 191                 if (opsize != expected_opsize &&
 192                     opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 193                         break;
 194
 195                 mp_opt->dss = 1;
 196
 197                 if (mp_opt->use_ack) {
 198                         if (mp_opt->ack64) {
 199                                 mp_opt->data_ack = get_unaligned_be64(ptr);
 200                                 ptr += 8;
 201                         } else {
 202                                 mp_opt->data_ack = get_unaligned_be32(ptr);
 203                                 ptr += 4;
 204                         }
 205
 206                         pr_debug("data_ack=%llu", mp_opt->data_ack);
 207                 }
 208
 209                 if (mp_opt->use_map) {
 210                         if (mp_opt->dsn64) {
 211                                 mp_opt->data_seq = get_unaligned_be64(ptr);
 212                                 ptr += 8;
 213                         } else {
 214                                 mp_opt->data_seq = get_unaligned_be32(ptr);
 215                                 ptr += 4;
 216                         }
 217
 218                         mp_opt->subflow_seq = get_unaligned_be32(ptr);
 219                         ptr += 4;
 220
 221                         mp_opt->data_len = get_unaligned_be16(ptr);
 222                         ptr += 2;
 223
 224                         if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
 225                                 mp_opt->csum_reqd = 1;
 226                                 mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
 227                                 ptr += 2;
 228                         }
 229
 230                         pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u",
 231                                  mp_opt->data_seq, mp_opt->subflow_seq,
 232                                  mp_opt->data_len, mp_opt->csum_reqd, mp_opt->csum);
 233                 }
 234
 235                 break;
 236
 237         case MPTCPOPT_ADD_ADDR:
 238                 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 239                 if (!mp_opt->echo) {
 240                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 241                             opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 242                                 mp_opt->addr.family = AF_INET;
 243 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 244                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 245                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 246                                 mp_opt->addr.family = AF_INET6;
 247 #endif
 248                         else
 249                                 break;
 250                 } else {
 251                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 252                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 253                                 mp_opt->addr.family = AF_INET;
 254 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 255                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 256                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 257                                 mp_opt->addr.family = AF_INET6;
 258 #endif
 259                         else
 260                                 break;
 261                 }
 262
 263                 mp_opt->add_addr = 1;
 264                 mp_opt->addr.id = *ptr++;
 265                 if (mp_opt->addr.family == AF_INET) {
 266                         memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
 267                         ptr += 4;
 268                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 269                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 270                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 271                                 ptr += 2;
 272                         }
 273                 }
 274 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 275                 else {
 276                         memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16);
 277                         ptr += 16;
 278                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 279                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 280                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 281                                 ptr += 2;
 282                         }
 283                 }
 284 #endif
 285                 if (!mp_opt->echo) {
 286                         mp_opt->ahmac = get_unaligned_be64(ptr);
 287                         ptr += 8;
 288                 }
 289                 pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d",
 290                          (mp_opt->addr.family == AF_INET6) ? "6" : "",
 291                          mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
 292                 break;
 293
 294         case MPTCPOPT_RM_ADDR:
 295                 if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
 296                     opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
 297                         break;
 298
 299                 ptr++;
 300
 301                 mp_opt->rm_addr = 1;
 302                 mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
 303                 for (i = 0; i < mp_opt->rm_list.nr; i++)
 304                         mp_opt->rm_list.ids[i] = *ptr++;
 305                 pr_debug("RM_ADDR: rm_list_nr=%d", mp_opt->rm_list.nr);
 306                 break;
 307
 308         case MPTCPOPT_MP_PRIO:
 309                 if (opsize != TCPOLEN_MPTCP_PRIO)
 310                         break;
 311
 312                 mp_opt->mp_prio = 1;
 313                 mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
 314                 pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
 315                 break;
 316
 317         case MPTCPOPT_MP_FASTCLOSE:
 318                 if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 319                         break;
 320
 321                 ptr += 2;
 322                 mp_opt->rcvr_key = get_unaligned_be64(ptr);
 323                 ptr += 8;
 324                 mp_opt->fastclose = 1;
 325                 break;
 326
 327         case MPTCPOPT_RST:
 328                 if (opsize != TCPOLEN_MPTCP_RST)
 329                         break;
 330
 331                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 332                         break;
 333                 mp_opt->reset = 1;
 334                 flags = *ptr++;
 335                 mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
 336                 mp_opt->reset_reason = *ptr;
 337                 break;
 338
 339         default:
 340                 break;
 341         }
 342 }
 343
 344 void mptcp_get_options(const struct sock *sk,
 345                        const struct sk_buff *skb,
 346                        struct mptcp_options_received *mp_opt)
 347 {
 348         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 349         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 350         const struct tcphdr *th = tcp_hdr(skb);
 351         const unsigned char *ptr;
 352         int length;
 353
 354         /* initialize option status */
 355         mp_opt->mp_capable = 0;
 356         mp_opt->mp_join = 0;
 357         mp_opt->add_addr = 0;
 358         mp_opt->ahmac = 0;
 359         mp_opt->fastclose = 0;
 360         mp_opt->addr.port = 0;
 361         mp_opt->rm_addr = 0;
 362         mp_opt->dss = 0;
 363         mp_opt->mp_prio = 0;
 364         mp_opt->reset = 0;
 365         mp_opt->csum_reqd = READ_ONCE(msk->csum_enabled);
 366         mp_opt->deny_join_id0 = 0;
 367
 368         length = (th->doff * 4) - sizeof(struct tcphdr);
 369         ptr = (const unsigned char *)(th + 1);
 370
 371         while (length > 0) {
 372                 int opcode = *ptr++;
 373                 int opsize;
 374
 375                 switch (opcode) {
 376                 case TCPOPT_EOL:
 377                         return;
 378                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 379                         length--;
 380                         continue;
 381                 default:
 382                         if (length < 2)
 383                                 return;
 384                         opsize = *ptr++;
 385                         if (opsize < 2) /* "silly options" */
 386                                 return;
 387                         if (opsize > length)
 388                                 return; /* don't parse partial options */
 389                         if (opcode == TCPOPT_MPTCP)
 390                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 391                         ptr += opsize - 2;
 392                         length -= opsize;
 393                 }
 394         }
 395 }
 396
 397 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 398                        unsigned int *size, struct mptcp_out_options *opts)
 399 {
 400         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 401
 402         /* we will use snd_isn to detect first pkt [re]transmission
 403          * in mptcp_established_options_mp()
 404          */
 405         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 406         if (subflow->request_mptcp) {
 407                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 408                 opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
 409                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 410                 *size = TCPOLEN_MPTCP_MPC_SYN;
 411                 return true;
 412         } else if (subflow->request_join) {
 413                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 414                          subflow->local_nonce);
 415                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 416                 opts->join_id = subflow->local_id;
 417                 opts->token = subflow->remote_token;
 418                 opts->nonce = subflow->local_nonce;
 419                 opts->backup = subflow->request_bkup;
 420                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 421                 return true;
 422         }
 423         return false;
 424 }
 425
 426 /* MP_JOIN client subflow must wait for 4th ack before sending any data:
 427  * TCP can't schedule delack timer before the subflow is fully established.
 428  * MPTCP uses the delack timer to do 3rd ack retransmissions
 429  */
 430 static void schedule_3rdack_retransmission(struct sock *sk)
 431 {
 432         struct inet_connection_sock *icsk = inet_csk(sk);
 433         struct tcp_sock *tp = tcp_sk(sk);
 434         unsigned long timeout;
 435
 436         /* reschedule with a timeout above RTT, as we must look only for drop */
 437         if (tp->srtt_us)
 438                 timeout = tp->srtt_us << 1;
 439         else
 440                 timeout = TCP_TIMEOUT_INIT;
 441
 442         WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 443         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 444         icsk->icsk_ack.timeout = timeout;
 445         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 446 }
 447
 448 static void clear_3rdack_retransmission(struct sock *sk)
 449 {
 450         struct inet_connection_sock *icsk = inet_csk(sk);
 451
 452         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 453         icsk->icsk_ack.timeout = 0;
 454         icsk->icsk_ack.ato = 0;
 455         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 456 }
 457
 458 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 459                                          bool snd_data_fin_enable,
 460                                          unsigned int *size,
 461                                          unsigned int remaining,
 462                                          struct mptcp_out_options *opts)
 463 {
 464         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 465         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 466         struct mptcp_ext *mpext;
 467         unsigned int data_len;
 468         u8 len;
 469
 470         /* When skb is not available, we better over-estimate the emitted
 471          * options len. A full DSS option (28 bytes) is longer than
 472          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 473          * tell the caller to defer the estimate to
 474          * mptcp_established_options_dss(), which will reserve enough space.
 475          */
 476         if (!skb)
 477                 return false;
 478
 479         /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
 480         if (subflow->fully_established || snd_data_fin_enable ||
 481             subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 482             sk->sk_state != TCP_ESTABLISHED)
 483                 return false;
 484
 485         if (subflow->mp_capable) {
 486                 mpext = mptcp_get_ext(skb);
 487                 data_len = mpext ? mpext->data_len : 0;
 488
 489                 /* we will check ext_copy.data_len in mptcp_write_options() to
 490                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 491                  * TCPOLEN_MPTCP_MPC_ACK
 492                  */
 493                 opts->ext_copy.data_len = data_len;
 494                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 495                 opts->sndr_key = subflow->local_key;
 496                 opts->rcvr_key = subflow->remote_key;
 497                 opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 498                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 499
 500                 /* Section 3.1.
 501                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 502                  * packets that start the first subflow of an MPTCP connection,
 503                  * as well as the first packet that carries data
 504                  */
 505                 if (data_len > 0) {
 506                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 507                         if (opts->csum_reqd) {
 508                                 /* we need to propagate more info to csum the pseudo hdr */
 509                                 opts->ext_copy.data_seq = mpext->data_seq;
 510                                 opts->ext_copy.subflow_seq = mpext->subflow_seq;
 511                                 opts->ext_copy.csum = mpext->csum;
 512                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
 513                         }
 514                         *size = ALIGN(len, 4);
 515                 } else {
 516                         *size = TCPOLEN_MPTCP_MPC_ACK;
 517                 }
 518
 519                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 520                          subflow, subflow->local_key, subflow->remote_key,
 521                          data_len);
 522
 523                 return true;
 524         } else if (subflow->mp_join) {
 525                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 526                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 527                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 528                 pr_debug("subflow=%p", subflow);
 529
 530                 schedule_3rdack_retransmission(sk);
 531                 return true;
 532         }
 533         return false;
 534 }
 535
 536 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 537                                  struct sk_buff *skb, struct mptcp_ext *ext)
 538 {
 539         /* The write_seq value has already been incremented, so the actual
 540          * sequence number for the DATA_FIN is one less.
 541          */
 542         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 543
 544         if (!ext->use_map || !skb->len) {
 545                 /* RFC6824 requires a DSS mapping with specific values
 546                  * if DATA_FIN is set but no data payload is mapped
 547                  */
 548                 ext->data_fin = 1;
 549                 ext->use_map = 1;
 550                 ext->dsn64 = 1;
 551                 ext->data_seq = data_fin_tx_seq;
 552                 ext->subflow_seq = 0;
 553                 ext->data_len = 1;
 554         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 555                 /* If there's an existing DSS mapping and it is the
 556                  * final mapping, DATA_FIN consumes 1 additional byte of
 557                  * mapping space.
 558                  */
 559                 ext->data_fin = 1;
 560                 ext->data_len++;
 561         }
 562 }
 563
 564 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 565                                           bool snd_data_fin_enable,
 566                                           unsigned int *size,
 567                                           unsigned int remaining,
 568                                           struct mptcp_out_options *opts)
 569 {
 570         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 571         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 572         unsigned int dss_size = 0;
 573         struct mptcp_ext *mpext;
 574         unsigned int ack_size;
 575         bool ret = false;
 576         u64 ack_seq;
 577
 578         opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 579         mpext = skb ? mptcp_get_ext(skb) : NULL;
 580
 581         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 582                 unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 583
 584                 if (mpext) {
 585                         if (opts->csum_reqd)
 586                                 map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
 587
 588                         opts->ext_copy = *mpext;
 589                 }
 590
 591                 remaining -= map_size;
 592                 dss_size = map_size;
 593                 if (skb && snd_data_fin_enable)
 594                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 595                 ret = true;
 596         }
 597
 598         /* passive sockets msk will set the 'can_ack' after accept(), even
 599          * if the first subflow may have the already the remote key handy
 600          */
 601         opts->ext_copy.use_ack = 0;
 602         if (!READ_ONCE(msk->can_ack)) {
 603                 *size = ALIGN(dss_size, 4);
 604                 return ret;
 605         }
 606
 607         ack_seq = READ_ONCE(msk->ack_seq);
 608         if (READ_ONCE(msk->use_64bit_ack)) {
 609                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 610                 opts->ext_copy.data_ack = ack_seq;
 611                 opts->ext_copy.ack64 = 1;
 612         } else {
 613                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 614                 opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
 615                 opts->ext_copy.ack64 = 0;
 616         }
 617         opts->ext_copy.use_ack = 1;
 618         WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 619
 620         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 621         if (dss_size == 0)
 622                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 623
 624         dss_size += ack_size;
 625
 626         *size = ALIGN(dss_size, 4);
 627         return true;
 628 }
 629
 630 static u64 add_addr_generate_hmac(u64 key1, u64 key2,
 631                                   struct mptcp_addr_info *addr)
 632 {
 633         u16 port = ntohs(addr->port);
 634         u8 hmac[SHA256_DIGEST_SIZE];
 635         u8 msg[19];
 636         int i = 0;
 637
 638         msg[i++] = addr->id;
 639         if (addr->family == AF_INET) {
 640                 memcpy(&msg[i], &addr->addr.s_addr, 4);
 641                 i += 4;
 642         }
 643 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 644         else if (addr->family == AF_INET6) {
 645                 memcpy(&msg[i], &addr->addr6.s6_addr, 16);
 646                 i += 16;
 647         }
 648 #endif
 649         msg[i++] = port >> 8;
 650         msg[i++] = port & 0xFF;
 651
 652         mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
 653
 654         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 655 }
 656
 657 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 658                                                unsigned int *size,
 659                                                unsigned int remaining,
 660                                                struct mptcp_out_options *opts)
 661 {
 662         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 663         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 664         bool drop_other_suboptions = false;
 665         unsigned int opt_size = *size;
 666         bool echo;
 667         bool port;
 668         int len;
 669
 670         if ((mptcp_pm_should_add_signal_ipv6(msk) ||
 671              mptcp_pm_should_add_signal_port(msk) ||
 672              mptcp_pm_should_add_signal_echo(msk)) &&
 673             skb && skb_is_tcp_pure_ack(skb)) {
 674                 pr_debug("drop other suboptions");
 675                 opts->suboptions = 0;
 676                 opts->ext_copy.use_ack = 0;
 677                 opts->ext_copy.use_map = 0;
 678                 remaining += opt_size;
 679                 drop_other_suboptions = true;
 680         }
 681
 682         if (!mptcp_pm_should_add_signal(msk) ||
 683             !(mptcp_pm_add_addr_signal(msk, remaining, &opts->addr, &echo, &port)))
 684                 return false;
 685
 686         len = mptcp_add_addr_len(opts->addr.family, echo, port);
 687         if (remaining < len)
 688                 return false;
 689
 690         *size = len;
 691         if (drop_other_suboptions)
 692                 *size -= opt_size;
 693         opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 694         if (!echo) {
 695                 opts->ahmac = add_addr_generate_hmac(msk->local_key,
 696                                                      msk->remote_key,
 697                                                      &opts->addr);
 698         }
 699         pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d",
 700                  opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
 701
 702         return true;
 703 }
 704
 705 static bool mptcp_established_options_rm_addr(struct sock *sk,
 706                                               unsigned int *size,
 707                                               unsigned int remaining,
 708                                               struct mptcp_out_options *opts)
 709 {
 710         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 711         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 712         struct mptcp_rm_list rm_list;
 713         int i, len;
 714
 715         if (!mptcp_pm_should_rm_signal(msk) ||
 716             !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
 717                 return false;
 718
 719         len = mptcp_rm_addr_len(&rm_list);
 720         if (len < 0)
 721                 return false;
 722         if (remaining < len)
 723                 return false;
 724
 725         *size = len;
 726         opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 727         opts->rm_list = rm_list;
 728
 729         for (i = 0; i < opts->rm_list.nr; i++)
 730                 pr_debug("rm_list_ids[%d]=%d", i, opts->rm_list.ids[i]);
 731
 732         return true;
 733 }
 734
 735 static bool mptcp_established_options_mp_prio(struct sock *sk,
 736                                               unsigned int *size,
 737                                               unsigned int remaining,
 738                                               struct mptcp_out_options *opts)
 739 {
 740         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 741
 742         if (!subflow->send_mp_prio)
 743                 return false;
 744
 745         /* account for the trailing 'nop' option */
 746         if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
 747                 return false;
 748
 749         *size = TCPOLEN_MPTCP_PRIO_ALIGN;
 750         opts->suboptions |= OPTION_MPTCP_PRIO;
 751         opts->backup = subflow->request_bkup;
 752
 753         pr_debug("prio=%d", opts->backup);
 754
 755         return true;
 756 }
 757
 758 static noinline void mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
 759                                                    unsigned int *size,
 760                                                    unsigned int remaining,
 761                                                    struct mptcp_out_options *opts)
 762 {
 763         const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 764
 765         if (remaining < TCPOLEN_MPTCP_RST)
 766                 return;
 767
 768         *size = TCPOLEN_MPTCP_RST;
 769         opts->suboptions |= OPTION_MPTCP_RST;
 770         opts->reset_transient = subflow->reset_transient;
 771         opts->reset_reason = subflow->reset_reason;
 772 }
 773
 774 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 775                                unsigned int *size, unsigned int remaining,
 776                                struct mptcp_out_options *opts)
 777 {
 778         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 779         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 780         unsigned int opt_size = 0;
 781         bool snd_data_fin;
 782         bool ret = false;
 783
 784         opts->suboptions = 0;
 785
 786         if (unlikely(__mptcp_check_fallback(msk)))
 787                 return false;
 788
 789         if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 790                 mptcp_established_options_rst(sk, skb, size, remaining, opts);
 791                 return true;
 792         }
 793
 794         snd_data_fin = mptcp_data_fin_enabled(msk);
 795         if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 796                 ret = true;
 797         else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 798                 ret = true;
 799
 800         /* we reserved enough space for the above options, and exceeding the
 801          * TCP option space would be fatal
 802          */
 803         if (WARN_ON_ONCE(opt_size > remaining))
 804                 return false;
 805
 806         *size += opt_size;
 807         remaining -= opt_size;
 808         if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
 809                 *size += opt_size;
 810                 remaining -= opt_size;
 811                 ret = true;
 812         } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 813                 *size += opt_size;
 814                 remaining -= opt_size;
 815                 ret = true;
 816         }
 817
 818         if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
 819                 *size += opt_size;
 820                 remaining -= opt_size;
 821                 ret = true;
 822         }
 823
 824         return ret;
 825 }
 826
 827 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 828                           struct mptcp_out_options *opts)
 829 {
 830         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 831
 832         if (subflow_req->mp_capable) {
 833                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 834                 opts->sndr_key = subflow_req->local_key;
 835                 opts->csum_reqd = subflow_req->csum_reqd;
 836                 opts->allow_join_id0 = subflow_req->allow_join_id0;
 837                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 838                 pr_debug("subflow_req=%p, local_key=%llu",
 839                          subflow_req, subflow_req->local_key);
 840                 return true;
 841         } else if (subflow_req->mp_join) {
 842                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 843                 opts->backup = subflow_req->backup;
 844                 opts->join_id = subflow_req->local_id;
 845                 opts->thmac = subflow_req->thmac;
 846                 opts->nonce = subflow_req->local_nonce;
 847                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 848                          subflow_req, opts->backup, opts->join_id,
 849                          opts->thmac, opts->nonce);
 850                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 851                 return true;
 852         }
 853         return false;
 854 }
 855
 856 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 857                                     struct mptcp_subflow_context *subflow,
 858                                     struct sk_buff *skb,
 859                                     struct mptcp_options_received *mp_opt)
 860 {
 861         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 862          * will make the subflow fully established
 863          */
 864         if (likely(subflow->fully_established)) {
 865                 /* on passive sockets, check for 3rd ack retransmission
 866                  * note that msk is always set by subflow_syn_recv_sock()
 867                  * for mp_join subflows
 868                  */
 869                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 870                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 871                     subflow->mp_join && mp_opt->mp_join &&
 872                     READ_ONCE(msk->pm.server_side))
 873                         tcp_send_ack(ssk);
 874                 goto fully_established;
 875         }
 876
 877         /* we must process OoO packets before the first subflow is fully
 878          * established. OoO packets are instead a protocol violation
 879          * for MP_JOIN subflows as the peer must not send any data
 880          * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 881          */
 882         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 883                 if (subflow->mp_join)
 884                         goto reset;
 885                 return subflow->mp_capable;
 886         }
 887
 888         if (mp_opt->dss && mp_opt->use_ack) {
 889                 /* subflows are fully established as soon as we get any
 890                  * additional ack.
 891                  */
 892                 subflow->fully_established = 1;
 893                 WRITE_ONCE(msk->fully_established, true);
 894                 goto fully_established;
 895         }
 896
 897         if (mp_opt->add_addr) {
 898                 WRITE_ONCE(msk->fully_established, true);
 899                 return true;
 900         }
 901
 902         /* If the first established packet does not contain MP_CAPABLE + data
 903          * then fallback to TCP. Fallback scenarios requires a reset for
 904          * MP_JOIN subflows.
 905          */
 906         if (!mp_opt->mp_capable) {
 907                 if (subflow->mp_join)
 908                         goto reset;
 909                 subflow->mp_capable = 0;
 910                 pr_fallback(msk);
 911                 __mptcp_do_fallback(msk);
 912                 return false;
 913         }
 914
 915         if (mp_opt->deny_join_id0)
 916                 WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 917
 918         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 919                 pr_warn_once("bogus mpc option on established client sk");
 920         mptcp_subflow_fully_established(subflow, mp_opt);
 921
 922 fully_established:
 923         /* if the subflow is not already linked into the conn_list, we can't
 924          * notify the PM: this subflow is still on the listener queue
 925          * and the PM possibly acquiring the subflow lock could race with
 926          * the listener close
 927          */
 928         if (likely(subflow->pm_notified) || list_empty(&subflow->node))
 929                 return true;
 930
 931         subflow->pm_notified = 1;
 932         if (subflow->mp_join) {
 933                 clear_3rdack_retransmission(ssk);
 934                 mptcp_pm_subflow_established(msk);
 935         } else {
 936                 mptcp_pm_fully_established(msk, ssk, GFP_ATOMIC);
 937         }
 938         return true;
 939
 940 reset:
 941         mptcp_subflow_reset(ssk);
 942         return false;
 943 }
 944
 945 u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
 946 {
 947         u32 old_seq32, cur_seq32;
 948
 949         old_seq32 = (u32)old_seq;
 950         cur_seq32 = (u32)cur_seq;
 951         cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
 952         if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
 953                 return cur_seq + (1LL << 32);
 954
 955         /* reverse wrap could happen, too */
 956         if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
 957                 return cur_seq - (1LL << 32);
 958         return cur_seq;
 959 }
 960
 961 static void ack_update_msk(struct mptcp_sock *msk,
 962                            struct sock *ssk,
 963                            struct mptcp_options_received *mp_opt)
 964 {
 965         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
 966         struct sock *sk = (struct sock *)msk;
 967         u64 old_snd_una;
 968
 969         mptcp_data_lock(sk);
 970
 971         /* avoid ack expansion on update conflict, to reduce the risk of
 972          * wrongly expanding to a future ack sequence number, which is way
 973          * more dangerous than missing an ack
 974          */
 975         old_snd_una = msk->snd_una;
 976         new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 977
 978         /* ACK for data not even sent yet? Ignore. */
 979         if (after64(new_snd_una, snd_nxt))
 980                 new_snd_una = old_snd_una;
 981
 982         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
 983
 984         if (after64(new_wnd_end, msk->wnd_end))
 985                 msk->wnd_end = new_wnd_end;
 986
 987         /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
 988         if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
 989                 __mptcp_check_push(sk, ssk);
 990
 991         if (after64(new_snd_una, old_snd_una)) {
 992                 msk->snd_una = new_snd_una;
 993                 __mptcp_data_acked(sk);
 994         }
 995         mptcp_data_unlock(sk);
 996
 997         trace_ack_update_msk(mp_opt->data_ack,
 998                              old_snd_una, new_snd_una,
 999                              new_wnd_end, msk->wnd_end);
1000 }
1001
1002 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
1003 {
1004         /* Skip if DATA_FIN was already received.
1005          * If updating simultaneously with the recvmsg loop, values
1006          * should match. If they mismatch, the peer is misbehaving and
1007          * we will prefer the most recent information.
1008          */
1009         if (READ_ONCE(msk->rcv_data_fin))
1010                 return false;
1011
1012         WRITE_ONCE(msk->rcv_data_fin_seq,
1013                    mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1014         WRITE_ONCE(msk->rcv_data_fin, 1);
1015
1016         return true;
1017 }
1018
1019 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1020                                 struct mptcp_options_received *mp_opt)
1021 {
1022         u64 hmac = 0;
1023
1024         if (mp_opt->echo)
1025                 return true;
1026
1027         hmac = add_addr_generate_hmac(msk->remote_key,
1028                                       msk->local_key,
1029                                       &mp_opt->addr);
1030
1031         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1032                  msk, (unsigned long long)hmac,
1033                  (unsigned long long)mp_opt->ahmac);
1034
1035         return hmac == mp_opt->ahmac;
1036 }
1037
1038 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1039 {
1040         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1041         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1042         struct mptcp_options_received mp_opt;
1043         struct mptcp_ext *mpext;
1044
1045         if (__mptcp_check_fallback(msk)) {
1046                 /* Keep it simple and unconditionally trigger send data cleanup and
1047                  * pending queue spooling. We will need to acquire the data lock
1048                  * for more accurate checks, and once the lock is acquired, such
1049                  * helpers are cheap.
1050                  */
1051                 mptcp_data_lock(subflow->conn);
1052                 if (sk_stream_memory_free(sk))
1053                         __mptcp_check_push(subflow->conn, sk);
1054                 __mptcp_data_acked(subflow->conn);
1055                 mptcp_data_unlock(subflow->conn);
1056                 return;
1057         }
1058
1059         mptcp_get_options(sk, skb, &mp_opt);
1060         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1061                 return;
1062
1063         if (mp_opt.fastclose &&
1064             msk->local_key == mp_opt.rcvr_key) {
1065                 WRITE_ONCE(msk->rcv_fastclose, true);
1066                 mptcp_schedule_work((struct sock *)msk);
1067         }
1068
1069         if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
1070                 if (!mp_opt.echo) {
1071                         mptcp_pm_add_addr_received(msk, &mp_opt.addr);
1072                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1073                 } else {
1074                         mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1075                         mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1076                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1077                 }
1078
1079                 if (mp_opt.addr.port)
1080                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1081
1082                 mp_opt.add_addr = 0;
1083         }
1084
1085         if (mp_opt.rm_addr) {
1086                 mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1087                 mp_opt.rm_addr = 0;
1088         }
1089
1090         if (mp_opt.mp_prio) {
1091                 mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1092                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1093                 mp_opt.mp_prio = 0;
1094         }
1095
1096         if (mp_opt.reset) {
1097                 subflow->reset_seen = 1;
1098                 subflow->reset_reason = mp_opt.reset_reason;
1099                 subflow->reset_transient = mp_opt.reset_transient;
1100         }
1101
1102         if (!mp_opt.dss)
1103                 return;
1104
1105         /* we can't wait for recvmsg() to update the ack_seq, otherwise
1106          * monodirectional flows will stuck
1107          */
1108         if (mp_opt.use_ack)
1109                 ack_update_msk(msk, sk, &mp_opt);
1110
1111         /* Zero-data-length packets are dropped by the caller and not
1112          * propagated to the MPTCP layer, so the skb extension does not
1113          * need to be allocated or populated. DATA_FIN information, if
1114          * present, needs to be updated here before the skb is freed.
1115          */
1116         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1117                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1118                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
1119                     schedule_work(&msk->work))
1120                         sock_hold(subflow->conn);
1121
1122                 return;
1123         }
1124
1125         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1126         if (!mpext)
1127                 return;
1128
1129         memset(mpext, 0, sizeof(*mpext));
1130
1131         if (mp_opt.use_map) {
1132                 if (mp_opt.mpc_map) {
1133                         /* this is an MP_CAPABLE carrying MPTCP data
1134                          * we know this map the first chunk of data
1135                          */
1136                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1137                                              &mpext->data_seq);
1138                         mpext->data_seq++;
1139                         mpext->subflow_seq = 1;
1140                         mpext->dsn64 = 1;
1141                         mpext->mpc_map = 1;
1142                         mpext->data_fin = 0;
1143                 } else {
1144                         mpext->data_seq = mp_opt.data_seq;
1145                         mpext->subflow_seq = mp_opt.subflow_seq;
1146                         mpext->dsn64 = mp_opt.dsn64;
1147                         mpext->data_fin = mp_opt.data_fin;
1148                 }
1149                 mpext->data_len = mp_opt.data_len;
1150                 mpext->use_map = 1;
1151                 mpext->csum_reqd = mp_opt.csum_reqd;
1152
1153                 if (mpext->csum_reqd)
1154                         mpext->csum = mp_opt.csum;
1155         }
1156 }
1157
1158 static void mptcp_set_rwin(const struct tcp_sock *tp)
1159 {
1160         const struct sock *ssk = (const struct sock *)tp;
1161         const struct mptcp_subflow_context *subflow;
1162         struct mptcp_sock *msk;
1163         u64 ack_seq;
1164
1165         subflow = mptcp_subflow_ctx(ssk);
1166         msk = mptcp_sk(subflow->conn);
1167
1168         ack_seq = READ_ONCE(msk->ack_seq) + tp->rcv_wnd;
1169
1170         if (after64(ack_seq, READ_ONCE(msk->rcv_wnd_sent)))
1171                 WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
1172 }
1173
1174 static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
1175 {
1176         struct csum_pseudo_header header;
1177         __wsum csum;
1178
1179         /* cfr RFC 8684 3.3.1.:
1180          * the data sequence number used in the pseudo-header is
1181          * always the 64-bit value, irrespective of what length is used in the
1182          * DSS option itself.
1183          */
1184         header.data_seq = cpu_to_be64(mpext->data_seq);
1185         header.subflow_seq = htonl(mpext->subflow_seq);
1186         header.data_len = htons(mpext->data_len);
1187         header.csum = 0;
1188
1189         csum = csum_partial(&header, sizeof(header), ~csum_unfold(mpext->csum));
1190         return (__force u16)csum_fold(csum);
1191 }
1192
1193 void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
1194                          struct mptcp_out_options *opts)
1195 {
1196         if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
1197              OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
1198                 u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1199
1200                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1201                         len = TCPOLEN_MPTCP_MPC_SYN;
1202                 } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1203                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1204                 } else if (opts->ext_copy.data_len) {
1205                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1206                         if (opts->csum_reqd)
1207                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1208                 } else {
1209                         len = TCPOLEN_MPTCP_MPC_ACK;
1210                 }
1211
1212                 if (opts->csum_reqd)
1213                         flag |= MPTCP_CAP_CHECKSUM_REQD;
1214
1215                 if (!opts->allow_join_id0)
1216                         flag |= MPTCP_CAP_DENY_JOIN_ID0;
1217
1218                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1219                                       MPTCP_SUPPORTED_VERSION,
1220                                       flag);
1221
1222                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1223                     opts->suboptions))
1224                         goto mp_capable_done;
1225
1226                 put_unaligned_be64(opts->sndr_key, ptr);
1227                 ptr += 2;
1228                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1229                         goto mp_capable_done;
1230
1231                 put_unaligned_be64(opts->rcvr_key, ptr);
1232                 ptr += 2;
1233                 if (!opts->ext_copy.data_len)
1234                         goto mp_capable_done;
1235
1236                 if (opts->csum_reqd) {
1237                         put_unaligned_be32(opts->ext_copy.data_len << 16 |
1238                                            mptcp_make_csum(&opts->ext_copy), ptr);
1239                 } else {
1240                         put_unaligned_be32(opts->ext_copy.data_len << 16 |
1241                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1242                 }
1243                 ptr += 1;
1244         }
1245
1246 mp_capable_done:
1247         if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1248                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1249                 u8 echo = MPTCP_ADDR_ECHO;
1250
1251 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1252                 if (opts->addr.family == AF_INET6)
1253                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1254 #endif
1255
1256                 if (opts->addr.port)
1257                         len += TCPOLEN_MPTCP_PORT_LEN;
1258
1259                 if (opts->ahmac) {
1260                         len += sizeof(opts->ahmac);
1261                         echo = 0;
1262                 }
1263
1264                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1265                                       len, echo, opts->addr.id);
1266                 if (opts->addr.family == AF_INET) {
1267                         memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1268                         ptr += 1;
1269                 }
1270 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1271                 else if (opts->addr.family == AF_INET6) {
1272                         memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1273                         ptr += 4;
1274                 }
1275 #endif
1276
1277                 if (!opts->addr.port) {
1278                         if (opts->ahmac) {
1279                                 put_unaligned_be64(opts->ahmac, ptr);
1280                                 ptr += 2;
1281                         }
1282                 } else {
1283                         u16 port = ntohs(opts->addr.port);
1284
1285                         if (opts->ahmac) {
1286                                 u8 *bptr = (u8 *)ptr;
1287
1288                                 put_unaligned_be16(port, bptr);
1289                                 bptr += 2;
1290                                 put_unaligned_be64(opts->ahmac, bptr);
1291                                 bptr += 8;
1292                                 put_unaligned_be16(TCPOPT_NOP << 8 |
1293                                                    TCPOPT_NOP, bptr);
1294
1295                                 ptr += 3;
1296                         } else {
1297                                 put_unaligned_be32(port << 16 |
1298                                                    TCPOPT_NOP << 8 |
1299                                                    TCPOPT_NOP, ptr);
1300                                 ptr += 1;
1301                         }
1302                 }
1303         }
1304
1305         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1306                 u8 i = 1;
1307
1308                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1309                                       TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1310                                       0, opts->rm_list.ids[0]);
1311
1312                 while (i < opts->rm_list.nr) {
1313                         u8 id1, id2, id3, id4;
1314
1315                         id1 = opts->rm_list.ids[i];
1316                         id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1317                         id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1318                         id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1319                         put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1320                         ptr += 1;
1321                         i += 4;
1322                 }
1323         }
1324
1325         if (OPTION_MPTCP_PRIO & opts->suboptions) {
1326                 const struct sock *ssk = (const struct sock *)tp;
1327                 struct mptcp_subflow_context *subflow;
1328
1329                 subflow = mptcp_subflow_ctx(ssk);
1330                 subflow->send_mp_prio = 0;
1331
1332                 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1333                                       TCPOLEN_MPTCP_PRIO,
1334                                       opts->backup, TCPOPT_NOP);
1335         }
1336
1337         if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1338                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1339                                       TCPOLEN_MPTCP_MPJ_SYN,
1340                                       opts->backup, opts->join_id);
1341                 put_unaligned_be32(opts->token, ptr);
1342                 ptr += 1;
1343                 put_unaligned_be32(opts->nonce, ptr);
1344                 ptr += 1;
1345         }
1346
1347         if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1348                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1349                                       TCPOLEN_MPTCP_MPJ_SYNACK,
1350                                       opts->backup, opts->join_id);
1351                 put_unaligned_be64(opts->thmac, ptr);
1352                 ptr += 2;
1353                 put_unaligned_be32(opts->nonce, ptr);
1354                 ptr += 1;
1355         }
1356
1357         if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
1358                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1359                                       TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1360                 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1361                 ptr += 5;
1362         }
1363
1364         if (OPTION_MPTCP_RST & opts->suboptions)
1365                 *ptr++ = mptcp_option(MPTCPOPT_RST,
1366                                       TCPOLEN_MPTCP_RST,
1367                                       opts->reset_transient,
1368                                       opts->reset_reason);
1369
1370         if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
1371                 struct mptcp_ext *mpext = &opts->ext_copy;
1372                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1373                 u8 flags = 0;
1374
1375                 if (mpext->use_ack) {
1376                         flags = MPTCP_DSS_HAS_ACK;
1377                         if (mpext->ack64) {
1378                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1379                                 flags |= MPTCP_DSS_ACK64;
1380                         } else {
1381                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1382                         }
1383                 }
1384
1385                 if (mpext->use_map) {
1386                         len += TCPOLEN_MPTCP_DSS_MAP64;
1387
1388                         /* Use only 64-bit mapping flags for now, add
1389                          * support for optional 32-bit mappings later.
1390                          */
1391                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1392                         if (mpext->data_fin)
1393                                 flags |= MPTCP_DSS_DATA_FIN;
1394
1395                         if (opts->csum_reqd)
1396                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1397                 }
1398
1399                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1400
1401                 if (mpext->use_ack) {
1402                         if (mpext->ack64) {
1403                                 put_unaligned_be64(mpext->data_ack, ptr);
1404                                 ptr += 2;
1405                         } else {
1406                                 put_unaligned_be32(mpext->data_ack32, ptr);
1407                                 ptr += 1;
1408                         }
1409                 }
1410
1411                 if (mpext->use_map) {
1412                         put_unaligned_be64(mpext->data_seq, ptr);
1413                         ptr += 2;
1414                         put_unaligned_be32(mpext->subflow_seq, ptr);
1415                         ptr += 1;
1416                         if (opts->csum_reqd) {
1417                                 put_unaligned_be32(mpext->data_len << 16 |
1418                                                    mptcp_make_csum(mpext), ptr);
1419                         } else {
1420                                 put_unaligned_be32(mpext->data_len << 16 |
1421                                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1422                         }
1423                 }
1424         }
1425
1426         if (tp)
1427                 mptcp_set_rwin(tp);
1428 }
1429
1430 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1431 {
1432         const struct mptcp_ext *ext = mptcp_get_ext(skb);
1433         u8 flags, reason;
1434
1435         if (ext) {
1436                 flags = ext->reset_transient;
1437                 reason = ext->reset_reason;
1438
1439                 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1440                                     flags, reason);
1441         }
1442
1443         return htonl(0u);
1444 }
1445 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);