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             (mp_opt->add_addr && !mp_opt->echo)) {
 890                 /* subflows are fully established as soon as we get any
 891                  * additional ack, including ADD_ADDR.
 892                  */
 893                 subflow->fully_established = 1;
 894                 WRITE_ONCE(msk->fully_established, true);
 895                 goto fully_established;
 896         }
 897
 898         /* If the first established packet does not contain MP_CAPABLE + data
 899          * then fallback to TCP. Fallback scenarios requires a reset for
 900          * MP_JOIN subflows.
 901          */
 902         if (!mp_opt->mp_capable) {
 903                 if (subflow->mp_join)
 904                         goto reset;
 905                 subflow->mp_capable = 0;
 906                 pr_fallback(msk);
 907                 __mptcp_do_fallback(msk);
 908                 return false;
 909         }
 910
 911         if (mp_opt->deny_join_id0)
 912                 WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 913
 914         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 915                 pr_warn_once("bogus mpc option on established client sk");
 916         mptcp_subflow_fully_established(subflow, mp_opt);
 917
 918 fully_established:
 919         /* if the subflow is not already linked into the conn_list, we can't
 920          * notify the PM: this subflow is still on the listener queue
 921          * and the PM possibly acquiring the subflow lock could race with
 922          * the listener close
 923          */
 924         if (likely(subflow->pm_notified) || list_empty(&subflow->node))
 925                 return true;
 926
 927         subflow->pm_notified = 1;
 928         if (subflow->mp_join) {
 929                 clear_3rdack_retransmission(ssk);
 930                 mptcp_pm_subflow_established(msk);
 931         } else {
 932                 mptcp_pm_fully_established(msk, ssk, GFP_ATOMIC);
 933         }
 934         return true;
 935
 936 reset:
 937         mptcp_subflow_reset(ssk);
 938         return false;
 939 }
 940
 941 u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
 942 {
 943         u32 old_seq32, cur_seq32;
 944
 945         old_seq32 = (u32)old_seq;
 946         cur_seq32 = (u32)cur_seq;
 947         cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
 948         if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
 949                 return cur_seq + (1LL << 32);
 950
 951         /* reverse wrap could happen, too */
 952         if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
 953                 return cur_seq - (1LL << 32);
 954         return cur_seq;
 955 }
 956
 957 static void ack_update_msk(struct mptcp_sock *msk,
 958                            struct sock *ssk,
 959                            struct mptcp_options_received *mp_opt)
 960 {
 961         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
 962         struct sock *sk = (struct sock *)msk;
 963         u64 old_snd_una;
 964
 965         mptcp_data_lock(sk);
 966
 967         /* avoid ack expansion on update conflict, to reduce the risk of
 968          * wrongly expanding to a future ack sequence number, which is way
 969          * more dangerous than missing an ack
 970          */
 971         old_snd_una = msk->snd_una;
 972         new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 973
 974         /* ACK for data not even sent yet? Ignore. */
 975         if (after64(new_snd_una, snd_nxt))
 976                 new_snd_una = old_snd_una;
 977
 978         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
 979
 980         if (after64(new_wnd_end, msk->wnd_end))
 981                 msk->wnd_end = new_wnd_end;
 982
 983         /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
 984         if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
 985                 __mptcp_check_push(sk, ssk);
 986
 987         if (after64(new_snd_una, old_snd_una)) {
 988                 msk->snd_una = new_snd_una;
 989                 __mptcp_data_acked(sk);
 990         }
 991         mptcp_data_unlock(sk);
 992
 993         trace_ack_update_msk(mp_opt->data_ack,
 994                              old_snd_una, new_snd_una,
 995                              new_wnd_end, msk->wnd_end);
 996 }
 997
 998 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
 999 {
1000         /* Skip if DATA_FIN was already received.
1001          * If updating simultaneously with the recvmsg loop, values
1002          * should match. If they mismatch, the peer is misbehaving and
1003          * we will prefer the most recent information.
1004          */
1005         if (READ_ONCE(msk->rcv_data_fin))
1006                 return false;
1007
1008         WRITE_ONCE(msk->rcv_data_fin_seq,
1009                    mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1010         WRITE_ONCE(msk->rcv_data_fin, 1);
1011
1012         return true;
1013 }
1014
1015 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1016                                 struct mptcp_options_received *mp_opt)
1017 {
1018         u64 hmac = 0;
1019
1020         if (mp_opt->echo)
1021                 return true;
1022
1023         hmac = add_addr_generate_hmac(msk->remote_key,
1024                                       msk->local_key,
1025                                       &mp_opt->addr);
1026
1027         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1028                  msk, (unsigned long long)hmac,
1029                  (unsigned long long)mp_opt->ahmac);
1030
1031         return hmac == mp_opt->ahmac;
1032 }
1033
1034 /* Return false if a subflow has been reset, else return true */
1035 bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1036 {
1037         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1038         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1039         struct mptcp_options_received mp_opt;
1040         struct mptcp_ext *mpext;
1041
1042         if (__mptcp_check_fallback(msk)) {
1043                 /* Keep it simple and unconditionally trigger send data cleanup and
1044                  * pending queue spooling. We will need to acquire the data lock
1045                  * for more accurate checks, and once the lock is acquired, such
1046                  * helpers are cheap.
1047                  */
1048                 mptcp_data_lock(subflow->conn);
1049                 if (sk_stream_memory_free(sk))
1050                         __mptcp_check_push(subflow->conn, sk);
1051                 __mptcp_data_acked(subflow->conn);
1052                 mptcp_data_unlock(subflow->conn);
1053                 return true;
1054         }
1055
1056         mptcp_get_options(sk, skb, &mp_opt);
1057
1058         /* The subflow can be in close state only if check_fully_established()
1059          * just sent a reset. If so, tell the caller to ignore the current packet.
1060          */
1061         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1062                 return sk->sk_state != TCP_CLOSE;
1063
1064         if (mp_opt.fastclose &&
1065             msk->local_key == mp_opt.rcvr_key) {
1066                 WRITE_ONCE(msk->rcv_fastclose, true);
1067                 mptcp_schedule_work((struct sock *)msk);
1068         }
1069
1070         if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
1071                 if (!mp_opt.echo) {
1072                         mptcp_pm_add_addr_received(msk, &mp_opt.addr);
1073                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1074                 } else {
1075                         mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1076                         mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1077                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1078                 }
1079
1080                 if (mp_opt.addr.port)
1081                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1082
1083                 mp_opt.add_addr = 0;
1084         }
1085
1086         if (mp_opt.rm_addr) {
1087                 mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1088                 mp_opt.rm_addr = 0;
1089         }
1090
1091         if (mp_opt.mp_prio) {
1092                 mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1093                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1094                 mp_opt.mp_prio = 0;
1095         }
1096
1097         if (mp_opt.reset) {
1098                 subflow->reset_seen = 1;
1099                 subflow->reset_reason = mp_opt.reset_reason;
1100                 subflow->reset_transient = mp_opt.reset_transient;
1101         }
1102
1103         if (!mp_opt.dss)
1104                 return true;
1105
1106         /* we can't wait for recvmsg() to update the ack_seq, otherwise
1107          * monodirectional flows will stuck
1108          */
1109         if (mp_opt.use_ack)
1110                 ack_update_msk(msk, sk, &mp_opt);
1111
1112         /* Zero-data-length packets are dropped by the caller and not
1113          * propagated to the MPTCP layer, so the skb extension does not
1114          * need to be allocated or populated. DATA_FIN information, if
1115          * present, needs to be updated here before the skb is freed.
1116          */
1117         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1118                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1119                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
1120                     schedule_work(&msk->work))
1121                         sock_hold(subflow->conn);
1122
1123                 return true;
1124         }
1125
1126         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1127         if (!mpext)
1128                 return true;
1129
1130         memset(mpext, 0, sizeof(*mpext));
1131
1132         if (mp_opt.use_map) {
1133                 if (mp_opt.mpc_map) {
1134                         /* this is an MP_CAPABLE carrying MPTCP data
1135                          * we know this map the first chunk of data
1136                          */
1137                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1138                                              &mpext->data_seq);
1139                         mpext->data_seq++;
1140                         mpext->subflow_seq = 1;
1141                         mpext->dsn64 = 1;
1142                         mpext->mpc_map = 1;
1143                         mpext->data_fin = 0;
1144                 } else {
1145                         mpext->data_seq = mp_opt.data_seq;
1146                         mpext->subflow_seq = mp_opt.subflow_seq;
1147                         mpext->dsn64 = mp_opt.dsn64;
1148                         mpext->data_fin = mp_opt.data_fin;
1149                 }
1150                 mpext->data_len = mp_opt.data_len;
1151                 mpext->use_map = 1;
1152                 mpext->csum_reqd = mp_opt.csum_reqd;
1153
1154                 if (mpext->csum_reqd)
1155                         mpext->csum = mp_opt.csum;
1156         }
1157
1158         return true;
1159 }
1160
1161 static void mptcp_set_rwin(const struct tcp_sock *tp)
1162 {
1163         const struct sock *ssk = (const struct sock *)tp;
1164         const struct mptcp_subflow_context *subflow;
1165         struct mptcp_sock *msk;
1166         u64 ack_seq;
1167
1168         subflow = mptcp_subflow_ctx(ssk);
1169         msk = mptcp_sk(subflow->conn);
1170
1171         ack_seq = READ_ONCE(msk->ack_seq) + tp->rcv_wnd;
1172
1173         if (after64(ack_seq, READ_ONCE(msk->rcv_wnd_sent)))
1174                 WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
1175 }
1176
1177 static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
1178 {
1179         struct csum_pseudo_header header;
1180         __wsum csum;
1181
1182         /* cfr RFC 8684 3.3.1.:
1183          * the data sequence number used in the pseudo-header is
1184          * always the 64-bit value, irrespective of what length is used in the
1185          * DSS option itself.
1186          */
1187         header.data_seq = cpu_to_be64(mpext->data_seq);
1188         header.subflow_seq = htonl(mpext->subflow_seq);
1189         header.data_len = htons(mpext->data_len);
1190         header.csum = 0;
1191
1192         csum = csum_partial(&header, sizeof(header), ~csum_unfold(mpext->csum));
1193         return (__force u16)csum_fold(csum);
1194 }
1195
1196 void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
1197                          struct mptcp_out_options *opts)
1198 {
1199         if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
1200              OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
1201                 u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1202
1203                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1204                         len = TCPOLEN_MPTCP_MPC_SYN;
1205                 } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1206                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1207                 } else if (opts->ext_copy.data_len) {
1208                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1209                         if (opts->csum_reqd)
1210                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1211                 } else {
1212                         len = TCPOLEN_MPTCP_MPC_ACK;
1213                 }
1214
1215                 if (opts->csum_reqd)
1216                         flag |= MPTCP_CAP_CHECKSUM_REQD;
1217
1218                 if (!opts->allow_join_id0)
1219                         flag |= MPTCP_CAP_DENY_JOIN_ID0;
1220
1221                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1222                                       MPTCP_SUPPORTED_VERSION,
1223                                       flag);
1224
1225                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1226                     opts->suboptions))
1227                         goto mp_capable_done;
1228
1229                 put_unaligned_be64(opts->sndr_key, ptr);
1230                 ptr += 2;
1231                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1232                         goto mp_capable_done;
1233
1234                 put_unaligned_be64(opts->rcvr_key, ptr);
1235                 ptr += 2;
1236                 if (!opts->ext_copy.data_len)
1237                         goto mp_capable_done;
1238
1239                 if (opts->csum_reqd) {
1240                         put_unaligned_be32(opts->ext_copy.data_len << 16 |
1241                                            mptcp_make_csum(&opts->ext_copy), ptr);
1242                 } else {
1243                         put_unaligned_be32(opts->ext_copy.data_len << 16 |
1244                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1245                 }
1246                 ptr += 1;
1247         }
1248
1249 mp_capable_done:
1250         if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1251                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1252                 u8 echo = MPTCP_ADDR_ECHO;
1253
1254 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1255                 if (opts->addr.family == AF_INET6)
1256                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1257 #endif
1258
1259                 if (opts->addr.port)
1260                         len += TCPOLEN_MPTCP_PORT_LEN;
1261
1262                 if (opts->ahmac) {
1263                         len += sizeof(opts->ahmac);
1264                         echo = 0;
1265                 }
1266
1267                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1268                                       len, echo, opts->addr.id);
1269                 if (opts->addr.family == AF_INET) {
1270                         memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1271                         ptr += 1;
1272                 }
1273 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1274                 else if (opts->addr.family == AF_INET6) {
1275                         memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1276                         ptr += 4;
1277                 }
1278 #endif
1279
1280                 if (!opts->addr.port) {
1281                         if (opts->ahmac) {
1282                                 put_unaligned_be64(opts->ahmac, ptr);
1283                                 ptr += 2;
1284                         }
1285                 } else {
1286                         u16 port = ntohs(opts->addr.port);
1287
1288                         if (opts->ahmac) {
1289                                 u8 *bptr = (u8 *)ptr;
1290
1291                                 put_unaligned_be16(port, bptr);
1292                                 bptr += 2;
1293                                 put_unaligned_be64(opts->ahmac, bptr);
1294                                 bptr += 8;
1295                                 put_unaligned_be16(TCPOPT_NOP << 8 |
1296                                                    TCPOPT_NOP, bptr);
1297
1298                                 ptr += 3;
1299                         } else {
1300                                 put_unaligned_be32(port << 16 |
1301                                                    TCPOPT_NOP << 8 |
1302                                                    TCPOPT_NOP, ptr);
1303                                 ptr += 1;
1304                         }
1305                 }
1306         }
1307
1308         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1309                 u8 i = 1;
1310
1311                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1312                                       TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1313                                       0, opts->rm_list.ids[0]);
1314
1315                 while (i < opts->rm_list.nr) {
1316                         u8 id1, id2, id3, id4;
1317
1318                         id1 = opts->rm_list.ids[i];
1319                         id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1320                         id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1321                         id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1322                         put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1323                         ptr += 1;
1324                         i += 4;
1325                 }
1326         }
1327
1328         if (OPTION_MPTCP_PRIO & opts->suboptions) {
1329                 const struct sock *ssk = (const struct sock *)tp;
1330                 struct mptcp_subflow_context *subflow;
1331
1332                 subflow = mptcp_subflow_ctx(ssk);
1333                 subflow->send_mp_prio = 0;
1334
1335                 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1336                                       TCPOLEN_MPTCP_PRIO,
1337                                       opts->backup, TCPOPT_NOP);
1338         }
1339
1340         if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1341                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1342                                       TCPOLEN_MPTCP_MPJ_SYN,
1343                                       opts->backup, opts->join_id);
1344                 put_unaligned_be32(opts->token, ptr);
1345                 ptr += 1;
1346                 put_unaligned_be32(opts->nonce, ptr);
1347                 ptr += 1;
1348         }
1349
1350         if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1351                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1352                                       TCPOLEN_MPTCP_MPJ_SYNACK,
1353                                       opts->backup, opts->join_id);
1354                 put_unaligned_be64(opts->thmac, ptr);
1355                 ptr += 2;
1356                 put_unaligned_be32(opts->nonce, ptr);
1357                 ptr += 1;
1358         }
1359
1360         if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
1361                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1362                                       TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1363                 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1364                 ptr += 5;
1365         }
1366
1367         if (OPTION_MPTCP_RST & opts->suboptions)
1368                 *ptr++ = mptcp_option(MPTCPOPT_RST,
1369                                       TCPOLEN_MPTCP_RST,
1370                                       opts->reset_transient,
1371                                       opts->reset_reason);
1372
1373         if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
1374                 struct mptcp_ext *mpext = &opts->ext_copy;
1375                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1376                 u8 flags = 0;
1377
1378                 if (mpext->use_ack) {
1379                         flags = MPTCP_DSS_HAS_ACK;
1380                         if (mpext->ack64) {
1381                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1382                                 flags |= MPTCP_DSS_ACK64;
1383                         } else {
1384                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1385                         }
1386                 }
1387
1388                 if (mpext->use_map) {
1389                         len += TCPOLEN_MPTCP_DSS_MAP64;
1390
1391                         /* Use only 64-bit mapping flags for now, add
1392                          * support for optional 32-bit mappings later.
1393                          */
1394                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1395                         if (mpext->data_fin)
1396                                 flags |= MPTCP_DSS_DATA_FIN;
1397
1398                         if (opts->csum_reqd)
1399                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1400                 }
1401
1402                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1403
1404                 if (mpext->use_ack) {
1405                         if (mpext->ack64) {
1406                                 put_unaligned_be64(mpext->data_ack, ptr);
1407                                 ptr += 2;
1408                         } else {
1409                                 put_unaligned_be32(mpext->data_ack32, ptr);
1410                                 ptr += 1;
1411                         }
1412                 }
1413
1414                 if (mpext->use_map) {
1415                         put_unaligned_be64(mpext->data_seq, ptr);
1416                         ptr += 2;
1417                         put_unaligned_be32(mpext->subflow_seq, ptr);
1418                         ptr += 1;
1419                         if (opts->csum_reqd) {
1420                                 put_unaligned_be32(mpext->data_len << 16 |
1421                                                    mptcp_make_csum(mpext), ptr);
1422                         } else {
1423                                 put_unaligned_be32(mpext->data_len << 16 |
1424                                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1425                         }
1426                 }
1427         }
1428
1429         if (tp)
1430                 mptcp_set_rwin(tp);
1431 }
1432
1433 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1434 {
1435         const struct mptcp_ext *ext = mptcp_get_ext(skb);
1436         u8 flags, reason;
1437
1438         if (ext) {
1439                 flags = ext->reset_transient;
1440                 reason = ext->reset_reason;
1441
1442                 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1443                                     flags, reason);
1444         }
1445
1446         return htonl(0u);
1447 }
1448 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);