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 <net/tcp.h>
  11 #include <net/mptcp.h>
  12 #include "protocol.h"
  13
  14 static bool mptcp_cap_flag_sha256(u8 flags)
  15 {
  16         return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
  17 }
  18
  19 static void mptcp_parse_option(const struct sk_buff *skb,
  20                                const unsigned char *ptr, int opsize,
  21                                struct mptcp_options_received *mp_opt)
  22 {
  23         u8 subtype = *ptr >> 4;
  24         int expected_opsize;
  25         u8 version;
  26         u8 flags;
  27
  28         switch (subtype) {
  29         case MPTCPOPT_MP_CAPABLE:
  30                 /* strict size checking */
  31                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
  32                         if (skb->len > tcp_hdr(skb)->doff << 2)
  33                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
  34                         else
  35                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
  36                 } else {
  37                         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)
  38                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
  39                         else
  40                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
  41                 }
  42                 if (opsize != expected_opsize)
  43                         break;
  44
  45                 /* try to be gentle vs future versions on the initial syn */
  46                 version = *ptr++ & MPTCP_VERSION_MASK;
  47                 if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
  48                         if (version != MPTCP_SUPPORTED_VERSION)
  49                                 break;
  50                 } else if (version < MPTCP_SUPPORTED_VERSION) {
  51                         break;
  52                 }
  53
  54                 flags = *ptr++;
  55                 if (!mptcp_cap_flag_sha256(flags) ||
  56                     (flags & MPTCP_CAP_EXTENSIBILITY))
  57                         break;
  58
  59                 /* RFC 6824, Section 3.1:
  60                  * "For the Checksum Required bit (labeled "A"), if either
  61                  * host requires the use of checksums, checksums MUST be used.
  62                  * In other words, the only way for checksums not to be used
  63                  * is if both hosts in their SYNs set A=0."
  64                  *
  65                  * Section 3.3.0:
  66                  * "If a checksum is not present when its use has been
  67                  * negotiated, the receiver MUST close the subflow with a RST as
  68                  * it is considered broken."
  69                  *
  70                  * We don't implement DSS checksum - fall back to TCP.
  71                  */
  72                 if (flags & MPTCP_CAP_CHECKSUM_REQD)
  73                         break;
  74
  75                 mp_opt->mp_capable = 1;
  76                 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
  77                         mp_opt->sndr_key = get_unaligned_be64(ptr);
  78                         ptr += 8;
  79                 }
  80                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
  81                         mp_opt->rcvr_key = get_unaligned_be64(ptr);
  82                         ptr += 8;
  83                 }
  84                 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA) {
  85                         /* Section 3.1.:
  86                          * "the data parameters in a MP_CAPABLE are semantically
  87                          * equivalent to those in a DSS option and can be used
  88                          * interchangeably."
  89                          */
  90                         mp_opt->dss = 1;
  91                         mp_opt->use_map = 1;
  92                         mp_opt->mpc_map = 1;
  93                         mp_opt->data_len = get_unaligned_be16(ptr);
  94                         ptr += 2;
  95                 }
  96                 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d",
  97                          version, flags, opsize, mp_opt->sndr_key,
  98                          mp_opt->rcvr_key, mp_opt->data_len);
  99                 break;
 100
 101         case MPTCPOPT_MP_JOIN:
 102                 mp_opt->mp_join = 1;
 103                 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 104                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 105                         mp_opt->join_id = *ptr++;
 106                         mp_opt->token = get_unaligned_be32(ptr);
 107                         ptr += 4;
 108                         mp_opt->nonce = get_unaligned_be32(ptr);
 109                         ptr += 4;
 110                         pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
 111                                  mp_opt->backup, mp_opt->join_id,
 112                                  mp_opt->token, mp_opt->nonce);
 113                 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
 114                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 115                         mp_opt->join_id = *ptr++;
 116                         mp_opt->thmac = get_unaligned_be64(ptr);
 117                         ptr += 8;
 118                         mp_opt->nonce = get_unaligned_be32(ptr);
 119                         ptr += 4;
 120                         pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
 121                                  mp_opt->backup, mp_opt->join_id,
 122                                  mp_opt->thmac, mp_opt->nonce);
 123                 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 124                         ptr += 2;
 125                         memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 126                         pr_debug("MP_JOIN hmac");
 127                 } else {
 128                         pr_warn("MP_JOIN bad option size");
 129                         mp_opt->mp_join = 0;
 130                 }
 131                 break;
 132
 133         case MPTCPOPT_DSS:
 134                 pr_debug("DSS");
 135                 ptr++;
 136
 137                 /* we must clear 'mpc_map' be able to detect MP_CAPABLE
 138                  * map vs DSS map in mptcp_incoming_options(), and reconstruct
 139                  * map info accordingly
 140                  */
 141                 mp_opt->mpc_map = 0;
 142                 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 143                 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 144                 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 145                 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 146                 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 147                 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 148
 149                 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
 150                          mp_opt->data_fin, mp_opt->dsn64,
 151                          mp_opt->use_map, mp_opt->ack64,
 152                          mp_opt->use_ack);
 153
 154                 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 155
 156                 if (mp_opt->use_ack) {
 157                         if (mp_opt->ack64)
 158                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 159                         else
 160                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 161                 }
 162
 163                 if (mp_opt->use_map) {
 164                         if (mp_opt->dsn64)
 165                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 166                         else
 167                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 168                 }
 169
 170                 /* RFC 6824, Section 3.3:
 171                  * If a checksum is present, but its use had
 172                  * not been negotiated in the MP_CAPABLE handshake,
 173                  * the checksum field MUST be ignored.
 174                  */
 175                 if (opsize != expected_opsize &&
 176                     opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 177                         break;
 178
 179                 mp_opt->dss = 1;
 180
 181                 if (mp_opt->use_ack) {
 182                         if (mp_opt->ack64) {
 183                                 mp_opt->data_ack = get_unaligned_be64(ptr);
 184                                 ptr += 8;
 185                         } else {
 186                                 mp_opt->data_ack = get_unaligned_be32(ptr);
 187                                 ptr += 4;
 188                         }
 189
 190                         pr_debug("data_ack=%llu", mp_opt->data_ack);
 191                 }
 192
 193                 if (mp_opt->use_map) {
 194                         if (mp_opt->dsn64) {
 195                                 mp_opt->data_seq = get_unaligned_be64(ptr);
 196                                 ptr += 8;
 197                         } else {
 198                                 mp_opt->data_seq = get_unaligned_be32(ptr);
 199                                 ptr += 4;
 200                         }
 201
 202                         mp_opt->subflow_seq = get_unaligned_be32(ptr);
 203                         ptr += 4;
 204
 205                         mp_opt->data_len = get_unaligned_be16(ptr);
 206                         ptr += 2;
 207
 208                         pr_debug("data_seq=%llu subflow_seq=%u data_len=%u",
 209                                  mp_opt->data_seq, mp_opt->subflow_seq,
 210                                  mp_opt->data_len);
 211                 }
 212
 213                 break;
 214
 215         case MPTCPOPT_ADD_ADDR:
 216                 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 217                 if (!mp_opt->echo) {
 218                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 219                             opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 220                                 mp_opt->family = MPTCP_ADDR_IPVERSION_4;
 221 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 222                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 223                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 224                                 mp_opt->family = MPTCP_ADDR_IPVERSION_6;
 225 #endif
 226                         else
 227                                 break;
 228                 } else {
 229                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 230                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 231                                 mp_opt->family = MPTCP_ADDR_IPVERSION_4;
 232 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 233                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 234                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 235                                 mp_opt->family = MPTCP_ADDR_IPVERSION_6;
 236 #endif
 237                         else
 238                                 break;
 239                 }
 240
 241                 mp_opt->add_addr = 1;
 242                 mp_opt->port = 0;
 243                 mp_opt->addr_id = *ptr++;
 244                 pr_debug("ADD_ADDR: id=%d", mp_opt->addr_id);
 245                 if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) {
 246                         memcpy((u8 *)&mp_opt->addr.s_addr, (u8 *)ptr, 4);
 247                         ptr += 4;
 248                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 249                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 250                                 mp_opt->port = get_unaligned_be16(ptr);
 251                                 ptr += 2;
 252                         }
 253                 }
 254 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 255                 else {
 256                         memcpy(mp_opt->addr6.s6_addr, (u8 *)ptr, 16);
 257                         ptr += 16;
 258                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 259                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 260                                 mp_opt->port = get_unaligned_be16(ptr);
 261                                 ptr += 2;
 262                         }
 263                 }
 264 #endif
 265                 if (!mp_opt->echo) {
 266                         mp_opt->ahmac = get_unaligned_be64(ptr);
 267                         ptr += 8;
 268                 }
 269                 break;
 270
 271         case MPTCPOPT_RM_ADDR:
 272                 if (opsize != TCPOLEN_MPTCP_RM_ADDR_BASE)
 273                         break;
 274
 275                 mp_opt->rm_addr = 1;
 276                 mp_opt->rm_id = *ptr++;
 277                 pr_debug("RM_ADDR: id=%d", mp_opt->rm_id);
 278                 break;
 279
 280         default:
 281                 break;
 282         }
 283 }
 284
 285 void mptcp_get_options(const struct sk_buff *skb,
 286                        struct mptcp_options_received *mp_opt)
 287 {
 288         const struct tcphdr *th = tcp_hdr(skb);
 289         const unsigned char *ptr;
 290         int length;
 291
 292         /* initialize option status */
 293         mp_opt->mp_capable = 0;
 294         mp_opt->mp_join = 0;
 295         mp_opt->add_addr = 0;
 296         mp_opt->rm_addr = 0;
 297         mp_opt->dss = 0;
 298
 299         length = (th->doff * 4) - sizeof(struct tcphdr);
 300         ptr = (const unsigned char *)(th + 1);
 301
 302         while (length > 0) {
 303                 int opcode = *ptr++;
 304                 int opsize;
 305
 306                 switch (opcode) {
 307                 case TCPOPT_EOL:
 308                         return;
 309                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 310                         length--;
 311                         continue;
 312                 default:
 313                         opsize = *ptr++;
 314                         if (opsize < 2) /* "silly options" */
 315                                 return;
 316                         if (opsize > length)
 317                                 return; /* don't parse partial options */
 318                         if (opcode == TCPOPT_MPTCP)
 319                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 320                         ptr += opsize - 2;
 321                         length -= opsize;
 322                 }
 323         }
 324 }
 325
 326 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 327                        unsigned int *size, struct mptcp_out_options *opts)
 328 {
 329         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 330
 331         /* we will use snd_isn to detect first pkt [re]transmission
 332          * in mptcp_established_options_mp()
 333          */
 334         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 335         if (subflow->request_mptcp) {
 336                 pr_debug("local_key=%llu", subflow->local_key);
 337                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 338                 opts->sndr_key = subflow->local_key;
 339                 *size = TCPOLEN_MPTCP_MPC_SYN;
 340                 return true;
 341         } else if (subflow->request_join) {
 342                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 343                          subflow->local_nonce);
 344                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 345                 opts->join_id = subflow->local_id;
 346                 opts->token = subflow->remote_token;
 347                 opts->nonce = subflow->local_nonce;
 348                 opts->backup = subflow->request_bkup;
 349                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 350                 return true;
 351         }
 352         return false;
 353 }
 354
 355 /* MP_JOIN client subflow must wait for 4th ack before sending any data:
 356  * TCP can't schedule delack timer before the subflow is fully established.
 357  * MPTCP uses the delack timer to do 3rd ack retransmissions
 358  */
 359 static void schedule_3rdack_retransmission(struct sock *sk)
 360 {
 361         struct inet_connection_sock *icsk = inet_csk(sk);
 362         struct tcp_sock *tp = tcp_sk(sk);
 363         unsigned long timeout;
 364
 365         /* reschedule with a timeout above RTT, as we must look only for drop */
 366         if (tp->srtt_us)
 367                 timeout = tp->srtt_us << 1;
 368         else
 369                 timeout = TCP_TIMEOUT_INIT;
 370
 371         WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 372         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 373         icsk->icsk_ack.timeout = timeout;
 374         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 375 }
 376
 377 static void clear_3rdack_retransmission(struct sock *sk)
 378 {
 379         struct inet_connection_sock *icsk = inet_csk(sk);
 380
 381         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 382         icsk->icsk_ack.timeout = 0;
 383         icsk->icsk_ack.ato = 0;
 384         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 385 }
 386
 387 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 388                                          unsigned int *size,
 389                                          unsigned int remaining,
 390                                          struct mptcp_out_options *opts)
 391 {
 392         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 393         struct mptcp_ext *mpext;
 394         unsigned int data_len;
 395
 396         /* When skb is not available, we better over-estimate the emitted
 397          * options len. A full DSS option (28 bytes) is longer than
 398          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 399          * tell the caller to defer the estimate to
 400          * mptcp_established_options_dss(), which will reserve enough space.
 401          */
 402         if (!skb)
 403                 return false;
 404
 405         /* MPC/MPJ needed only on 3rd ack packet */
 406         if (subflow->fully_established ||
 407             subflow->snd_isn != TCP_SKB_CB(skb)->seq)
 408                 return false;
 409
 410         if (subflow->mp_capable) {
 411                 mpext = mptcp_get_ext(skb);
 412                 data_len = mpext ? mpext->data_len : 0;
 413
 414                 /* we will check ext_copy.data_len in mptcp_write_options() to
 415                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 416                  * TCPOLEN_MPTCP_MPC_ACK
 417                  */
 418                 opts->ext_copy.data_len = data_len;
 419                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 420                 opts->sndr_key = subflow->local_key;
 421                 opts->rcvr_key = subflow->remote_key;
 422
 423                 /* Section 3.1.
 424                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 425                  * packets that start the first subflow of an MPTCP connection,
 426                  * as well as the first packet that carries data
 427                  */
 428                 if (data_len > 0)
 429                         *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
 430                 else
 431                         *size = TCPOLEN_MPTCP_MPC_ACK;
 432
 433                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 434                          subflow, subflow->local_key, subflow->remote_key,
 435                          data_len);
 436
 437                 return true;
 438         } else if (subflow->mp_join) {
 439                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 440                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 441                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 442                 pr_debug("subflow=%p", subflow);
 443
 444                 schedule_3rdack_retransmission(sk);
 445                 return true;
 446         }
 447         return false;
 448 }
 449
 450 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 451                                  struct mptcp_ext *ext)
 452 {
 453         if (!ext->use_map) {
 454                 /* RFC6824 requires a DSS mapping with specific values
 455                  * if DATA_FIN is set but no data payload is mapped
 456                  */
 457                 ext->data_fin = 1;
 458                 ext->use_map = 1;
 459                 ext->dsn64 = 1;
 460                 ext->data_seq = subflow->data_fin_tx_seq;
 461                 ext->subflow_seq = 0;
 462                 ext->data_len = 1;
 463         } else if (ext->data_seq + ext->data_len == subflow->data_fin_tx_seq) {
 464                 /* If there's an existing DSS mapping and it is the
 465                  * final mapping, DATA_FIN consumes 1 additional byte of
 466                  * mapping space.
 467                  */
 468                 ext->data_fin = 1;
 469                 ext->data_len++;
 470         }
 471 }
 472
 473 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 474                                           unsigned int *size,
 475                                           unsigned int remaining,
 476                                           struct mptcp_out_options *opts)
 477 {
 478         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 479         unsigned int dss_size = 0;
 480         struct mptcp_ext *mpext;
 481         struct mptcp_sock *msk;
 482         unsigned int ack_size;
 483         bool ret = false;
 484         u8 tcp_fin;
 485
 486         if (skb) {
 487                 mpext = mptcp_get_ext(skb);
 488                 tcp_fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
 489         } else {
 490                 mpext = NULL;
 491                 tcp_fin = 0;
 492         }
 493
 494         if (!skb || (mpext && mpext->use_map) || tcp_fin) {
 495                 unsigned int map_size;
 496
 497                 map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 498
 499                 remaining -= map_size;
 500                 dss_size = map_size;
 501                 if (mpext)
 502                         opts->ext_copy = *mpext;
 503
 504                 if (skb && tcp_fin && subflow->data_fin_tx_enable)
 505                         mptcp_write_data_fin(subflow, &opts->ext_copy);
 506                 ret = true;
 507         }
 508
 509         /* passive sockets msk will set the 'can_ack' after accept(), even
 510          * if the first subflow may have the already the remote key handy
 511          */
 512         opts->ext_copy.use_ack = 0;
 513         msk = mptcp_sk(subflow->conn);
 514         if (!READ_ONCE(msk->can_ack)) {
 515                 *size = ALIGN(dss_size, 4);
 516                 return ret;
 517         }
 518
 519         ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 520
 521         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 522         if (dss_size == 0)
 523                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 524
 525         dss_size += ack_size;
 526
 527         opts->ext_copy.data_ack = msk->ack_seq;
 528         opts->ext_copy.ack64 = 1;
 529         opts->ext_copy.use_ack = 1;
 530
 531         *size = ALIGN(dss_size, 4);
 532         return true;
 533 }
 534
 535 static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 536                                   struct in_addr *addr)
 537 {
 538         u8 hmac[MPTCP_ADDR_HMAC_LEN];
 539         u8 msg[7];
 540
 541         msg[0] = addr_id;
 542         memcpy(&msg[1], &addr->s_addr, 4);
 543         msg[5] = 0;
 544         msg[6] = 0;
 545
 546         mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac);
 547
 548         return get_unaligned_be64(hmac);
 549 }
 550
 551 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 552 static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 553                                    struct in6_addr *addr)
 554 {
 555         u8 hmac[MPTCP_ADDR_HMAC_LEN];
 556         u8 msg[19];
 557
 558         msg[0] = addr_id;
 559         memcpy(&msg[1], &addr->s6_addr, 16);
 560         msg[17] = 0;
 561         msg[18] = 0;
 562
 563         mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac);
 564
 565         return get_unaligned_be64(hmac);
 566 }
 567 #endif
 568
 569 static bool mptcp_established_options_addr(struct sock *sk,
 570                                            unsigned int *size,
 571                                            unsigned int remaining,
 572                                            struct mptcp_out_options *opts)
 573 {
 574         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 575         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 576         struct mptcp_addr_info saddr;
 577         int len;
 578
 579         if (!mptcp_pm_should_signal(msk) ||
 580             !(mptcp_pm_addr_signal(msk, remaining, &saddr)))
 581                 return false;
 582
 583         len = mptcp_add_addr_len(saddr.family);
 584         if (remaining < len)
 585                 return false;
 586
 587         *size = len;
 588         opts->addr_id = saddr.id;
 589         if (saddr.family == AF_INET) {
 590                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 591                 opts->addr = saddr.addr;
 592                 opts->ahmac = add_addr_generate_hmac(msk->local_key,
 593                                                      msk->remote_key,
 594                                                      opts->addr_id,
 595                                                      &opts->addr);
 596         }
 597 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 598         else if (saddr.family == AF_INET6) {
 599                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR6;
 600                 opts->addr6 = saddr.addr6;
 601                 opts->ahmac = add_addr6_generate_hmac(msk->local_key,
 602                                                       msk->remote_key,
 603                                                       opts->addr_id,
 604                                                       &opts->addr6);
 605         }
 606 #endif
 607         pr_debug("addr_id=%d, ahmac=%llu", opts->addr_id, opts->ahmac);
 608
 609         return true;
 610 }
 611
 612 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 613                                unsigned int *size, unsigned int remaining,
 614                                struct mptcp_out_options *opts)
 615 {
 616         unsigned int opt_size = 0;
 617         bool ret = false;
 618
 619         opts->suboptions = 0;
 620
 621         if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts))
 622                 ret = true;
 623         else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining,
 624                                                opts))
 625                 ret = true;
 626
 627         /* we reserved enough space for the above options, and exceeding the
 628          * TCP option space would be fatal
 629          */
 630         if (WARN_ON_ONCE(opt_size > remaining))
 631                 return false;
 632
 633         *size += opt_size;
 634         remaining -= opt_size;
 635         if (mptcp_established_options_addr(sk, &opt_size, remaining, opts)) {
 636                 *size += opt_size;
 637                 remaining -= opt_size;
 638                 ret = true;
 639         }
 640
 641         return ret;
 642 }
 643
 644 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 645                           struct mptcp_out_options *opts)
 646 {
 647         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 648
 649         if (subflow_req->mp_capable) {
 650                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 651                 opts->sndr_key = subflow_req->local_key;
 652                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 653                 pr_debug("subflow_req=%p, local_key=%llu",
 654                          subflow_req, subflow_req->local_key);
 655                 return true;
 656         } else if (subflow_req->mp_join) {
 657                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 658                 opts->backup = subflow_req->backup;
 659                 opts->join_id = subflow_req->local_id;
 660                 opts->thmac = subflow_req->thmac;
 661                 opts->nonce = subflow_req->local_nonce;
 662                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 663                          subflow_req, opts->backup, opts->join_id,
 664                          opts->thmac, opts->nonce);
 665                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 666                 return true;
 667         }
 668         return false;
 669 }
 670
 671 static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
 672                                     struct mptcp_subflow_context *subflow,
 673                                     struct sk_buff *skb,
 674                                     struct mptcp_options_received *mp_opt)
 675 {
 676         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 677          * will make the subflow fully established
 678          */
 679         if (likely(subflow->fully_established)) {
 680                 /* on passive sockets, check for 3rd ack retransmission
 681                  * note that msk is always set by subflow_syn_recv_sock()
 682                  * for mp_join subflows
 683                  */
 684                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 685                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 686                     subflow->mp_join && mp_opt->mp_join &&
 687                     READ_ONCE(msk->pm.server_side))
 688                         tcp_send_ack(sk);
 689                 goto fully_established;
 690         }
 691
 692         /* we should process OoO packets before the first subflow is fully
 693          * established, but not expected for MP_JOIN subflows
 694          */
 695         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1)
 696                 return subflow->mp_capable;
 697
 698         if (mp_opt->dss && mp_opt->use_ack) {
 699                 /* subflows are fully established as soon as we get any
 700                  * additional ack.
 701                  */
 702                 subflow->fully_established = 1;
 703                 goto fully_established;
 704         }
 705
 706         /* If the first established packet does not contain MP_CAPABLE + data
 707          * then fallback to TCP
 708          */
 709         if (!mp_opt->mp_capable) {
 710                 subflow->mp_capable = 0;
 711                 tcp_sk(sk)->is_mptcp = 0;
 712                 return false;
 713         }
 714
 715         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 716                 pr_warn_once("bogus mpc option on established client sk");
 717         subflow->fully_established = 1;
 718         subflow->remote_key = mp_opt->sndr_key;
 719         subflow->can_ack = 1;
 720
 721 fully_established:
 722         if (likely(subflow->pm_notified))
 723                 return true;
 724
 725         subflow->pm_notified = 1;
 726         if (subflow->mp_join) {
 727                 clear_3rdack_retransmission(sk);
 728                 mptcp_pm_subflow_established(msk, subflow);
 729         } else {
 730                 mptcp_pm_fully_established(msk);
 731         }
 732         return true;
 733 }
 734
 735 static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)
 736 {
 737         u32 old_ack32, cur_ack32;
 738
 739         if (use_64bit)
 740                 return cur_ack;
 741
 742         old_ack32 = (u32)old_ack;
 743         cur_ack32 = (u32)cur_ack;
 744         cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32;
 745         if (unlikely(before(cur_ack32, old_ack32)))
 746                 return cur_ack + (1LL << 32);
 747         return cur_ack;
 748 }
 749
 750 static void update_una(struct mptcp_sock *msk,
 751                        struct mptcp_options_received *mp_opt)
 752 {
 753         u64 new_snd_una, snd_una, old_snd_una = atomic64_read(&msk->snd_una);
 754         u64 write_seq = READ_ONCE(msk->write_seq);
 755
 756         /* avoid ack expansion on update conflict, to reduce the risk of
 757          * wrongly expanding to a future ack sequence number, which is way
 758          * more dangerous than missing an ack
 759          */
 760         new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 761
 762         /* ACK for data not even sent yet? Ignore. */
 763         if (after64(new_snd_una, write_seq))
 764                 new_snd_una = old_snd_una;
 765
 766         while (after64(new_snd_una, old_snd_una)) {
 767                 snd_una = old_snd_una;
 768                 old_snd_una = atomic64_cmpxchg(&msk->snd_una, snd_una,
 769                                                new_snd_una);
 770                 if (old_snd_una == snd_una) {
 771                         mptcp_data_acked((struct sock *)msk);
 772                         break;
 773                 }
 774         }
 775 }
 776
 777 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
 778                                 struct mptcp_options_received *mp_opt)
 779 {
 780         u64 hmac = 0;
 781
 782         if (mp_opt->echo)
 783                 return true;
 784
 785         if (mp_opt->family == MPTCP_ADDR_IPVERSION_4)
 786                 hmac = add_addr_generate_hmac(msk->remote_key,
 787                                               msk->local_key,
 788                                               mp_opt->addr_id, &mp_opt->addr);
 789 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 790         else
 791                 hmac = add_addr6_generate_hmac(msk->remote_key,
 792                                                msk->local_key,
 793                                                mp_opt->addr_id, &mp_opt->addr6);
 794 #endif
 795
 796         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
 797                  msk, (unsigned long long)hmac,
 798                  (unsigned long long)mp_opt->ahmac);
 799
 800         return hmac == mp_opt->ahmac;
 801 }
 802
 803 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb,
 804                             struct tcp_options_received *opt_rx)
 805 {
 806         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 807         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 808         struct mptcp_options_received mp_opt;
 809         struct mptcp_ext *mpext;
 810
 811         mptcp_get_options(skb, &mp_opt);
 812         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
 813                 return;
 814
 815         if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
 816                 struct mptcp_addr_info addr;
 817
 818                 addr.port = htons(mp_opt.port);
 819                 addr.id = mp_opt.addr_id;
 820                 if (mp_opt.family == MPTCP_ADDR_IPVERSION_4) {
 821                         addr.family = AF_INET;
 822                         addr.addr = mp_opt.addr;
 823                 }
 824 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 825                 else if (mp_opt.family == MPTCP_ADDR_IPVERSION_6) {
 826                         addr.family = AF_INET6;
 827                         addr.addr6 = mp_opt.addr6;
 828                 }
 829 #endif
 830                 if (!mp_opt.echo)
 831                         mptcp_pm_add_addr_received(msk, &addr);
 832                 mp_opt.add_addr = 0;
 833         }
 834
 835         if (!mp_opt.dss)
 836                 return;
 837
 838         /* we can't wait for recvmsg() to update the ack_seq, otherwise
 839          * monodirectional flows will stuck
 840          */
 841         if (mp_opt.use_ack)
 842                 update_una(msk, &mp_opt);
 843
 844         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
 845         if (!mpext)
 846                 return;
 847
 848         memset(mpext, 0, sizeof(*mpext));
 849
 850         if (mp_opt.use_map) {
 851                 if (mp_opt.mpc_map) {
 852                         /* this is an MP_CAPABLE carrying MPTCP data
 853                          * we know this map the first chunk of data
 854                          */
 855                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
 856                                              &mpext->data_seq);
 857                         mpext->data_seq++;
 858                         mpext->subflow_seq = 1;
 859                         mpext->dsn64 = 1;
 860                         mpext->mpc_map = 1;
 861                         mpext->data_fin = 0;
 862                 } else {
 863                         mpext->data_seq = mp_opt.data_seq;
 864                         mpext->subflow_seq = mp_opt.subflow_seq;
 865                         mpext->dsn64 = mp_opt.dsn64;
 866                         mpext->data_fin = mp_opt.data_fin;
 867                 }
 868                 mpext->data_len = mp_opt.data_len;
 869                 mpext->use_map = 1;
 870         }
 871 }
 872
 873 void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts)
 874 {
 875         if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
 876              OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
 877                 u8 len;
 878
 879                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
 880                         len = TCPOLEN_MPTCP_MPC_SYN;
 881                 else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
 882                         len = TCPOLEN_MPTCP_MPC_SYNACK;
 883                 else if (opts->ext_copy.data_len)
 884                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 885                 else
 886                         len = TCPOLEN_MPTCP_MPC_ACK;
 887
 888                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
 889                                       MPTCP_SUPPORTED_VERSION,
 890                                       MPTCP_CAP_HMAC_SHA256);
 891
 892                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
 893                     opts->suboptions))
 894                         goto mp_capable_done;
 895
 896                 put_unaligned_be64(opts->sndr_key, ptr);
 897                 ptr += 2;
 898                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
 899                         goto mp_capable_done;
 900
 901                 put_unaligned_be64(opts->rcvr_key, ptr);
 902                 ptr += 2;
 903                 if (!opts->ext_copy.data_len)
 904                         goto mp_capable_done;
 905
 906                 put_unaligned_be32(opts->ext_copy.data_len << 16 |
 907                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
 908                 ptr += 1;
 909         }
 910
 911 mp_capable_done:
 912         if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
 913                 if (opts->ahmac)
 914                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 915                                               TCPOLEN_MPTCP_ADD_ADDR, 0,
 916                                               opts->addr_id);
 917                 else
 918                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 919                                               TCPOLEN_MPTCP_ADD_ADDR_BASE,
 920                                               MPTCP_ADDR_ECHO,
 921                                               opts->addr_id);
 922                 memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4);
 923                 ptr += 1;
 924                 if (opts->ahmac) {
 925                         put_unaligned_be64(opts->ahmac, ptr);
 926                         ptr += 2;
 927                 }
 928         }
 929
 930 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 931         if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) {
 932                 if (opts->ahmac)
 933                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 934                                               TCPOLEN_MPTCP_ADD_ADDR6, 0,
 935                                               opts->addr_id);
 936                 else
 937                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 938                                               TCPOLEN_MPTCP_ADD_ADDR6_BASE,
 939                                               MPTCP_ADDR_ECHO,
 940                                               opts->addr_id);
 941                 memcpy((u8 *)ptr, opts->addr6.s6_addr, 16);
 942                 ptr += 4;
 943                 if (opts->ahmac) {
 944                         put_unaligned_be64(opts->ahmac, ptr);
 945                         ptr += 2;
 946                 }
 947         }
 948 #endif
 949
 950         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
 951                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
 952                                       TCPOLEN_MPTCP_RM_ADDR_BASE,
 953                                       0, opts->rm_id);
 954         }
 955
 956         if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
 957                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
 958                                       TCPOLEN_MPTCP_MPJ_SYN,
 959                                       opts->backup, opts->join_id);
 960                 put_unaligned_be32(opts->token, ptr);
 961                 ptr += 1;
 962                 put_unaligned_be32(opts->nonce, ptr);
 963                 ptr += 1;
 964         }
 965
 966         if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
 967                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
 968                                       TCPOLEN_MPTCP_MPJ_SYNACK,
 969                                       opts->backup, opts->join_id);
 970                 put_unaligned_be64(opts->thmac, ptr);
 971                 ptr += 2;
 972                 put_unaligned_be32(opts->nonce, ptr);
 973                 ptr += 1;
 974         }
 975
 976         if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
 977                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
 978                                       TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
 979                 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
 980                 ptr += 5;
 981         }
 982
 983         if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
 984                 struct mptcp_ext *mpext = &opts->ext_copy;
 985                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
 986                 u8 flags = 0;
 987
 988                 if (mpext->use_ack) {
 989                         len += TCPOLEN_MPTCP_DSS_ACK64;
 990                         flags = MPTCP_DSS_HAS_ACK | MPTCP_DSS_ACK64;
 991                 }
 992
 993                 if (mpext->use_map) {
 994                         len += TCPOLEN_MPTCP_DSS_MAP64;
 995
 996                         /* Use only 64-bit mapping flags for now, add
 997                          * support for optional 32-bit mappings later.
 998                          */
 999                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1000                         if (mpext->data_fin)
1001                                 flags |= MPTCP_DSS_DATA_FIN;
1002                 }
1003
1004                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1005
1006                 if (mpext->use_ack) {
1007                         put_unaligned_be64(mpext->data_ack, ptr);
1008                         ptr += 2;
1009                 }
1010
1011                 if (mpext->use_map) {
1012                         put_unaligned_be64(mpext->data_seq, ptr);
1013                         ptr += 2;
1014                         put_unaligned_be32(mpext->subflow_seq, ptr);
1015                         ptr += 1;
1016                         put_unaligned_be32(mpext->data_len << 16 |
1017                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1018                 }
1019         }
1020 }