net/mptcp/options.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Multipath TCP
   3  *
   4  * Copyright (c) 2017 - 2019, Intel Corporation.
   5  */
   6
   7 #define pr_fmt(fmt) "MPTCP: " fmt
   8
   9 #include <linux/kernel.h>
  10 #include <crypto/sha.h>
  11 #include <net/tcp.h>
  12 #include <net/mptcp.h>
  13 #include "protocol.h"
  14
  15 static bool mptcp_cap_flag_sha256(u8 flags)
  16 {
  17         return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
  18 }
  19
  20 static void mptcp_parse_option(const struct sk_buff *skb,
  21                                const unsigned char *ptr, int opsize,
  22                                struct mptcp_options_received *mp_opt)
  23 {
  24         u8 subtype = *ptr >> 4;
  25         int expected_opsize;
  26         u8 version;
  27         u8 flags;
  28
  29         switch (subtype) {
  30         case MPTCPOPT_MP_CAPABLE:
  31                 /* strict size checking */
  32                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
  33                         if (skb->len > tcp_hdr(skb)->doff << 2)
  34                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
  35                         else
  36                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
  37                 } else {
  38                         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)
  39                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
  40                         else
  41                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
  42                 }
  43                 if (opsize != expected_opsize)
  44                         break;
  45
  46                 /* try to be gentle vs future versions on the initial syn */
  47                 version = *ptr++ & MPTCP_VERSION_MASK;
  48                 if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
  49                         if (version != MPTCP_SUPPORTED_VERSION)
  50                                 break;
  51                 } else if (version < MPTCP_SUPPORTED_VERSION) {
  52                         break;
  53                 }
  54
  55                 flags = *ptr++;
  56                 if (!mptcp_cap_flag_sha256(flags) ||
  57                     (flags & MPTCP_CAP_EXTENSIBILITY))
  58                         break;
  59
  60                 /* RFC 6824, Section 3.1:
  61                  * "For the Checksum Required bit (labeled "A"), if either
  62                  * host requires the use of checksums, checksums MUST be used.
  63                  * In other words, the only way for checksums not to be used
  64                  * is if both hosts in their SYNs set A=0."
  65                  *
  66                  * Section 3.3.0:
  67                  * "If a checksum is not present when its use has been
  68                  * negotiated, the receiver MUST close the subflow with a RST as
  69                  * it is considered broken."
  70                  *
  71                  * We don't implement DSS checksum - fall back to TCP.
  72                  */
  73                 if (flags & MPTCP_CAP_CHECKSUM_REQD)
  74                         break;
  75
  76                 mp_opt->mp_capable = 1;
  77                 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
  78                         mp_opt->sndr_key = get_unaligned_be64(ptr);
  79                         ptr += 8;
  80                 }
  81                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
  82                         mp_opt->rcvr_key = get_unaligned_be64(ptr);
  83                         ptr += 8;
  84                 }
  85                 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA) {
  86                         /* Section 3.1.:
  87                          * "the data parameters in a MP_CAPABLE are semantically
  88                          * equivalent to those in a DSS option and can be used
  89                          * interchangeably."
  90                          */
  91                         mp_opt->dss = 1;
  92                         mp_opt->use_map = 1;
  93                         mp_opt->mpc_map = 1;
  94                         mp_opt->data_len = get_unaligned_be16(ptr);
  95                         ptr += 2;
  96                 }
  97                 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d",
  98                          version, flags, opsize, mp_opt->sndr_key,
  99                          mp_opt->rcvr_key, mp_opt->data_len);
 100                 break;
 101
 102         case MPTCPOPT_MP_JOIN:
 103                 mp_opt->mp_join = 1;
 104                 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 105                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 106                         mp_opt->join_id = *ptr++;
 107                         mp_opt->token = get_unaligned_be32(ptr);
 108                         ptr += 4;
 109                         mp_opt->nonce = get_unaligned_be32(ptr);
 110                         ptr += 4;
 111                         pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
 112                                  mp_opt->backup, mp_opt->join_id,
 113                                  mp_opt->token, mp_opt->nonce);
 114                 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
 115                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 116                         mp_opt->join_id = *ptr++;
 117                         mp_opt->thmac = get_unaligned_be64(ptr);
 118                         ptr += 8;
 119                         mp_opt->nonce = get_unaligned_be32(ptr);
 120                         ptr += 4;
 121                         pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
 122                                  mp_opt->backup, mp_opt->join_id,
 123                                  mp_opt->thmac, mp_opt->nonce);
 124                 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 125                         ptr += 2;
 126                         memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 127                         pr_debug("MP_JOIN hmac");
 128                 } else {
 129                         pr_warn("MP_JOIN bad option size");
 130                         mp_opt->mp_join = 0;
 131                 }
 132                 break;
 133
 134         case MPTCPOPT_DSS:
 135                 pr_debug("DSS");
 136                 ptr++;
 137
 138                 /* we must clear 'mpc_map' be able to detect MP_CAPABLE
 139                  * map vs DSS map in mptcp_incoming_options(), and reconstruct
 140                  * map info accordingly
 141                  */
 142                 mp_opt->mpc_map = 0;
 143                 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 144                 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 145                 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 146                 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 147                 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 148                 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 149
 150                 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
 151                          mp_opt->data_fin, mp_opt->dsn64,
 152                          mp_opt->use_map, mp_opt->ack64,
 153                          mp_opt->use_ack);
 154
 155                 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 156
 157                 if (mp_opt->use_ack) {
 158                         if (mp_opt->ack64)
 159                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 160                         else
 161                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 162                 }
 163
 164                 if (mp_opt->use_map) {
 165                         if (mp_opt->dsn64)
 166                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 167                         else
 168                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 169                 }
 170
 171                 /* RFC 6824, Section 3.3:
 172                  * If a checksum is present, but its use had
 173                  * not been negotiated in the MP_CAPABLE handshake,
 174                  * the checksum field MUST be ignored.
 175                  */
 176                 if (opsize != expected_opsize &&
 177                     opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 178                         break;
 179
 180                 mp_opt->dss = 1;
 181
 182                 if (mp_opt->use_ack) {
 183                         if (mp_opt->ack64) {
 184                                 mp_opt->data_ack = get_unaligned_be64(ptr);
 185                                 ptr += 8;
 186                         } else {
 187                                 mp_opt->data_ack = get_unaligned_be32(ptr);
 188                                 ptr += 4;
 189                         }
 190
 191                         pr_debug("data_ack=%llu", mp_opt->data_ack);
 192                 }
 193
 194                 if (mp_opt->use_map) {
 195                         if (mp_opt->dsn64) {
 196                                 mp_opt->data_seq = get_unaligned_be64(ptr);
 197                                 ptr += 8;
 198                         } else {
 199                                 mp_opt->data_seq = get_unaligned_be32(ptr);
 200                                 ptr += 4;
 201                         }
 202
 203                         mp_opt->subflow_seq = get_unaligned_be32(ptr);
 204                         ptr += 4;
 205
 206                         mp_opt->data_len = get_unaligned_be16(ptr);
 207                         ptr += 2;
 208
 209                         pr_debug("data_seq=%llu subflow_seq=%u data_len=%u",
 210                                  mp_opt->data_seq, mp_opt->subflow_seq,
 211                                  mp_opt->data_len);
 212                 }
 213
 214                 break;
 215
 216         case MPTCPOPT_ADD_ADDR:
 217                 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 218                 if (!mp_opt->echo) {
 219                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 220                             opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 221                                 mp_opt->family = MPTCP_ADDR_IPVERSION_4;
 222 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 223                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 224                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 225                                 mp_opt->family = MPTCP_ADDR_IPVERSION_6;
 226 #endif
 227                         else
 228                                 break;
 229                 } else {
 230                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 231                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 232                                 mp_opt->family = MPTCP_ADDR_IPVERSION_4;
 233 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 234                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 235                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 236                                 mp_opt->family = MPTCP_ADDR_IPVERSION_6;
 237 #endif
 238                         else
 239                                 break;
 240                 }
 241
 242                 mp_opt->add_addr = 1;
 243                 mp_opt->port = 0;
 244                 mp_opt->addr_id = *ptr++;
 245                 pr_debug("ADD_ADDR: id=%d", mp_opt->addr_id);
 246                 if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) {
 247                         memcpy((u8 *)&mp_opt->addr.s_addr, (u8 *)ptr, 4);
 248                         ptr += 4;
 249                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 250                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 251                                 mp_opt->port = get_unaligned_be16(ptr);
 252                                 ptr += 2;
 253                         }
 254                 }
 255 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 256                 else {
 257                         memcpy(mp_opt->addr6.s6_addr, (u8 *)ptr, 16);
 258                         ptr += 16;
 259                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 260                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 261                                 mp_opt->port = get_unaligned_be16(ptr);
 262                                 ptr += 2;
 263                         }
 264                 }
 265 #endif
 266                 if (!mp_opt->echo) {
 267                         mp_opt->ahmac = get_unaligned_be64(ptr);
 268                         ptr += 8;
 269                 }
 270                 break;
 271
 272         case MPTCPOPT_RM_ADDR:
 273                 if (opsize != TCPOLEN_MPTCP_RM_ADDR_BASE)
 274                         break;
 275
 276                 ptr++;
 277
 278                 mp_opt->rm_addr = 1;
 279                 mp_opt->rm_id = *ptr++;
 280                 pr_debug("RM_ADDR: id=%d", mp_opt->rm_id);
 281                 break;
 282
 283         default:
 284                 break;
 285         }
 286 }
 287
 288 void mptcp_get_options(const struct sk_buff *skb,
 289                        struct mptcp_options_received *mp_opt)
 290 {
 291         const struct tcphdr *th = tcp_hdr(skb);
 292         const unsigned char *ptr;
 293         int length;
 294
 295         /* initialize option status */
 296         mp_opt->mp_capable = 0;
 297         mp_opt->mp_join = 0;
 298         mp_opt->add_addr = 0;
 299         mp_opt->rm_addr = 0;
 300         mp_opt->dss = 0;
 301
 302         length = (th->doff * 4) - sizeof(struct tcphdr);
 303         ptr = (const unsigned char *)(th + 1);
 304
 305         while (length > 0) {
 306                 int opcode = *ptr++;
 307                 int opsize;
 308
 309                 switch (opcode) {
 310                 case TCPOPT_EOL:
 311                         return;
 312                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 313                         length--;
 314                         continue;
 315                 default:
 316                         opsize = *ptr++;
 317                         if (opsize < 2) /* "silly options" */
 318                                 return;
 319                         if (opsize > length)
 320                                 return; /* don't parse partial options */
 321                         if (opcode == TCPOPT_MPTCP)
 322                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 323                         ptr += opsize - 2;
 324                         length -= opsize;
 325                 }
 326         }
 327 }
 328
 329 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 330                        unsigned int *size, struct mptcp_out_options *opts)
 331 {
 332         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 333
 334         /* we will use snd_isn to detect first pkt [re]transmission
 335          * in mptcp_established_options_mp()
 336          */
 337         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 338         if (subflow->request_mptcp) {
 339                 pr_debug("local_key=%llu", subflow->local_key);
 340                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 341                 opts->sndr_key = subflow->local_key;
 342                 *size = TCPOLEN_MPTCP_MPC_SYN;
 343                 return true;
 344         } else if (subflow->request_join) {
 345                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 346                          subflow->local_nonce);
 347                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 348                 opts->join_id = subflow->local_id;
 349                 opts->token = subflow->remote_token;
 350                 opts->nonce = subflow->local_nonce;
 351                 opts->backup = subflow->request_bkup;
 352                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 353                 return true;
 354         }
 355         return false;
 356 }
 357
 358 /* MP_JOIN client subflow must wait for 4th ack before sending any data:
 359  * TCP can't schedule delack timer before the subflow is fully established.
 360  * MPTCP uses the delack timer to do 3rd ack retransmissions
 361  */
 362 static void schedule_3rdack_retransmission(struct sock *sk)
 363 {
 364         struct inet_connection_sock *icsk = inet_csk(sk);
 365         struct tcp_sock *tp = tcp_sk(sk);
 366         unsigned long timeout;
 367
 368         /* reschedule with a timeout above RTT, as we must look only for drop */
 369         if (tp->srtt_us)
 370                 timeout = tp->srtt_us << 1;
 371         else
 372                 timeout = TCP_TIMEOUT_INIT;
 373
 374         WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 375         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 376         icsk->icsk_ack.timeout = timeout;
 377         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 378 }
 379
 380 static void clear_3rdack_retransmission(struct sock *sk)
 381 {
 382         struct inet_connection_sock *icsk = inet_csk(sk);
 383
 384         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 385         icsk->icsk_ack.timeout = 0;
 386         icsk->icsk_ack.ato = 0;
 387         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 388 }
 389
 390 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 391                                          unsigned int *size,
 392                                          unsigned int remaining,
 393                                          struct mptcp_out_options *opts)
 394 {
 395         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 396         struct mptcp_ext *mpext;
 397         unsigned int data_len;
 398
 399         /* When skb is not available, we better over-estimate the emitted
 400          * options len. A full DSS option (28 bytes) is longer than
 401          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 402          * tell the caller to defer the estimate to
 403          * mptcp_established_options_dss(), which will reserve enough space.
 404          */
 405         if (!skb)
 406                 return false;
 407
 408         /* MPC/MPJ needed only on 3rd ack packet */
 409         if (subflow->fully_established ||
 410             subflow->snd_isn != TCP_SKB_CB(skb)->seq)
 411                 return false;
 412
 413         if (subflow->mp_capable) {
 414                 mpext = mptcp_get_ext(skb);
 415                 data_len = mpext ? mpext->data_len : 0;
 416
 417                 /* we will check ext_copy.data_len in mptcp_write_options() to
 418                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 419                  * TCPOLEN_MPTCP_MPC_ACK
 420                  */
 421                 opts->ext_copy.data_len = data_len;
 422                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 423                 opts->sndr_key = subflow->local_key;
 424                 opts->rcvr_key = subflow->remote_key;
 425
 426                 /* Section 3.1.
 427                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 428                  * packets that start the first subflow of an MPTCP connection,
 429                  * as well as the first packet that carries data
 430                  */
 431                 if (data_len > 0)
 432                         *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
 433                 else
 434                         *size = TCPOLEN_MPTCP_MPC_ACK;
 435
 436                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 437                          subflow, subflow->local_key, subflow->remote_key,
 438                          data_len);
 439
 440                 return true;
 441         } else if (subflow->mp_join) {
 442                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 443                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 444                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 445                 pr_debug("subflow=%p", subflow);
 446
 447                 schedule_3rdack_retransmission(sk);
 448                 return true;
 449         }
 450         return false;
 451 }
 452
 453 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 454                                  struct mptcp_ext *ext)
 455 {
 456         if (!ext->use_map) {
 457                 /* RFC6824 requires a DSS mapping with specific values
 458                  * if DATA_FIN is set but no data payload is mapped
 459                  */
 460                 ext->data_fin = 1;
 461                 ext->use_map = 1;
 462                 ext->dsn64 = 1;
 463                 ext->data_seq = subflow->data_fin_tx_seq;
 464                 ext->subflow_seq = 0;
 465                 ext->data_len = 1;
 466         } else if (ext->data_seq + ext->data_len == subflow->data_fin_tx_seq) {
 467                 /* If there's an existing DSS mapping and it is the
 468                  * final mapping, DATA_FIN consumes 1 additional byte of
 469                  * mapping space.
 470                  */
 471                 ext->data_fin = 1;
 472                 ext->data_len++;
 473         }
 474 }
 475
 476 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 477                                           unsigned int *size,
 478                                           unsigned int remaining,
 479                                           struct mptcp_out_options *opts)
 480 {
 481         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 482         unsigned int dss_size = 0;
 483         struct mptcp_ext *mpext;
 484         struct mptcp_sock *msk;
 485         unsigned int ack_size;
 486         bool ret = false;
 487         u8 tcp_fin;
 488
 489         if (skb) {
 490                 mpext = mptcp_get_ext(skb);
 491                 tcp_fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
 492         } else {
 493                 mpext = NULL;
 494                 tcp_fin = 0;
 495         }
 496
 497         if (!skb || (mpext && mpext->use_map) || tcp_fin) {
 498                 unsigned int map_size;
 499
 500                 map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 501
 502                 remaining -= map_size;
 503                 dss_size = map_size;
 504                 if (mpext)
 505                         opts->ext_copy = *mpext;
 506
 507                 if (skb && tcp_fin && subflow->data_fin_tx_enable)
 508                         mptcp_write_data_fin(subflow, &opts->ext_copy);
 509                 ret = true;
 510         }
 511
 512         /* passive sockets msk will set the 'can_ack' after accept(), even
 513          * if the first subflow may have the already the remote key handy
 514          */
 515         opts->ext_copy.use_ack = 0;
 516         msk = mptcp_sk(subflow->conn);
 517         if (!READ_ONCE(msk->can_ack)) {
 518                 *size = ALIGN(dss_size, 4);
 519                 return ret;
 520         }
 521
 522         if (subflow->use_64bit_ack) {
 523                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 524                 opts->ext_copy.data_ack = msk->ack_seq;
 525                 opts->ext_copy.ack64 = 1;
 526         } else {
 527                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 528                 opts->ext_copy.data_ack32 = (uint32_t)(msk->ack_seq);
 529                 opts->ext_copy.ack64 = 0;
 530         }
 531         opts->ext_copy.use_ack = 1;
 532
 533         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 534         if (dss_size == 0)
 535                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 536
 537         dss_size += ack_size;
 538
 539         *size = ALIGN(dss_size, 4);
 540         return true;
 541 }
 542
 543 static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 544                                   struct in_addr *addr)
 545 {
 546         u8 hmac[SHA256_DIGEST_SIZE];
 547         u8 msg[7];
 548
 549         msg[0] = addr_id;
 550         memcpy(&msg[1], &addr->s_addr, 4);
 551         msg[5] = 0;
 552         msg[6] = 0;
 553
 554         mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac);
 555
 556         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 557 }
 558
 559 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 560 static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 561                                    struct in6_addr *addr)
 562 {
 563         u8 hmac[SHA256_DIGEST_SIZE];
 564         u8 msg[19];
 565
 566         msg[0] = addr_id;
 567         memcpy(&msg[1], &addr->s6_addr, 16);
 568         msg[17] = 0;
 569         msg[18] = 0;
 570
 571         mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac);
 572
 573         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 574 }
 575 #endif
 576
 577 static bool mptcp_established_options_addr(struct sock *sk,
 578                                            unsigned int *size,
 579                                            unsigned int remaining,
 580                                            struct mptcp_out_options *opts)
 581 {
 582         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 583         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 584         struct mptcp_addr_info saddr;
 585         int len;
 586
 587         if (!mptcp_pm_should_signal(msk) ||
 588             !(mptcp_pm_addr_signal(msk, remaining, &saddr)))
 589                 return false;
 590
 591         len = mptcp_add_addr_len(saddr.family);
 592         if (remaining < len)
 593                 return false;
 594
 595         *size = len;
 596         opts->addr_id = saddr.id;
 597         if (saddr.family == AF_INET) {
 598                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 599                 opts->addr = saddr.addr;
 600                 opts->ahmac = add_addr_generate_hmac(msk->local_key,
 601                                                      msk->remote_key,
 602                                                      opts->addr_id,
 603                                                      &opts->addr);
 604         }
 605 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 606         else if (saddr.family == AF_INET6) {
 607                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR6;
 608                 opts->addr6 = saddr.addr6;
 609                 opts->ahmac = add_addr6_generate_hmac(msk->local_key,
 610                                                       msk->remote_key,
 611                                                       opts->addr_id,
 612                                                       &opts->addr6);
 613         }
 614 #endif
 615         pr_debug("addr_id=%d, ahmac=%llu", opts->addr_id, opts->ahmac);
 616
 617         return true;
 618 }
 619
 620 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 621                                unsigned int *size, unsigned int remaining,
 622                                struct mptcp_out_options *opts)
 623 {
 624         unsigned int opt_size = 0;
 625         bool ret = false;
 626
 627         opts->suboptions = 0;
 628
 629         if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts))
 630                 ret = true;
 631         else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining,
 632                                                opts))
 633                 ret = true;
 634
 635         /* we reserved enough space for the above options, and exceeding the
 636          * TCP option space would be fatal
 637          */
 638         if (WARN_ON_ONCE(opt_size > remaining))
 639                 return false;
 640
 641         *size += opt_size;
 642         remaining -= opt_size;
 643         if (mptcp_established_options_addr(sk, &opt_size, remaining, opts)) {
 644                 *size += opt_size;
 645                 remaining -= opt_size;
 646                 ret = true;
 647         }
 648
 649         return ret;
 650 }
 651
 652 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 653                           struct mptcp_out_options *opts)
 654 {
 655         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 656
 657         if (subflow_req->mp_capable) {
 658                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 659                 opts->sndr_key = subflow_req->local_key;
 660                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 661                 pr_debug("subflow_req=%p, local_key=%llu",
 662                          subflow_req, subflow_req->local_key);
 663                 return true;
 664         } else if (subflow_req->mp_join) {
 665                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 666                 opts->backup = subflow_req->backup;
 667                 opts->join_id = subflow_req->local_id;
 668                 opts->thmac = subflow_req->thmac;
 669                 opts->nonce = subflow_req->local_nonce;
 670                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 671                          subflow_req, opts->backup, opts->join_id,
 672                          opts->thmac, opts->nonce);
 673                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 674                 return true;
 675         }
 676         return false;
 677 }
 678
 679 static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
 680                                     struct mptcp_subflow_context *subflow,
 681                                     struct sk_buff *skb,
 682                                     struct mptcp_options_received *mp_opt)
 683 {
 684         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 685          * will make the subflow fully established
 686          */
 687         if (likely(subflow->fully_established)) {
 688                 /* on passive sockets, check for 3rd ack retransmission
 689                  * note that msk is always set by subflow_syn_recv_sock()
 690                  * for mp_join subflows
 691                  */
 692                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 693                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 694                     subflow->mp_join && mp_opt->mp_join &&
 695                     READ_ONCE(msk->pm.server_side))
 696                         tcp_send_ack(sk);
 697                 goto fully_established;
 698         }
 699
 700         /* we should process OoO packets before the first subflow is fully
 701          * established, but not expected for MP_JOIN subflows
 702          */
 703         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1)
 704                 return subflow->mp_capable;
 705
 706         if (mp_opt->dss && mp_opt->use_ack) {
 707                 /* subflows are fully established as soon as we get any
 708                  * additional ack.
 709                  */
 710                 subflow->fully_established = 1;
 711                 goto fully_established;
 712         }
 713
 714         /* If the first established packet does not contain MP_CAPABLE + data
 715          * then fallback to TCP
 716          */
 717         if (!mp_opt->mp_capable) {
 718                 subflow->mp_capable = 0;
 719                 tcp_sk(sk)->is_mptcp = 0;
 720                 return false;
 721         }
 722
 723         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 724                 pr_warn_once("bogus mpc option on established client sk");
 725         subflow->fully_established = 1;
 726         subflow->remote_key = mp_opt->sndr_key;
 727         subflow->can_ack = 1;
 728
 729 fully_established:
 730         if (likely(subflow->pm_notified))
 731                 return true;
 732
 733         subflow->pm_notified = 1;
 734         if (subflow->mp_join) {
 735                 clear_3rdack_retransmission(sk);
 736                 mptcp_pm_subflow_established(msk, subflow);
 737         } else {
 738                 mptcp_pm_fully_established(msk);
 739         }
 740         return true;
 741 }
 742
 743 static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)
 744 {
 745         u32 old_ack32, cur_ack32;
 746
 747         if (use_64bit)
 748                 return cur_ack;
 749
 750         old_ack32 = (u32)old_ack;
 751         cur_ack32 = (u32)cur_ack;
 752         cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32;
 753         if (unlikely(before(cur_ack32, old_ack32)))
 754                 return cur_ack + (1LL << 32);
 755         return cur_ack;
 756 }
 757
 758 static void update_una(struct mptcp_sock *msk,
 759                        struct mptcp_options_received *mp_opt)
 760 {
 761         u64 new_snd_una, snd_una, old_snd_una = atomic64_read(&msk->snd_una);
 762         u64 write_seq = READ_ONCE(msk->write_seq);
 763
 764         /* avoid ack expansion on update conflict, to reduce the risk of
 765          * wrongly expanding to a future ack sequence number, which is way
 766          * more dangerous than missing an ack
 767          */
 768         new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 769
 770         /* ACK for data not even sent yet? Ignore. */
 771         if (after64(new_snd_una, write_seq))
 772                 new_snd_una = old_snd_una;
 773
 774         while (after64(new_snd_una, old_snd_una)) {
 775                 snd_una = old_snd_una;
 776                 old_snd_una = atomic64_cmpxchg(&msk->snd_una, snd_una,
 777                                                new_snd_una);
 778                 if (old_snd_una == snd_una) {
 779                         mptcp_data_acked((struct sock *)msk);
 780                         break;
 781                 }
 782         }
 783 }
 784
 785 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
 786                                 struct mptcp_options_received *mp_opt)
 787 {
 788         u64 hmac = 0;
 789
 790         if (mp_opt->echo)
 791                 return true;
 792
 793         if (mp_opt->family == MPTCP_ADDR_IPVERSION_4)
 794                 hmac = add_addr_generate_hmac(msk->remote_key,
 795                                               msk->local_key,
 796                                               mp_opt->addr_id, &mp_opt->addr);
 797 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 798         else
 799                 hmac = add_addr6_generate_hmac(msk->remote_key,
 800                                                msk->local_key,
 801                                                mp_opt->addr_id, &mp_opt->addr6);
 802 #endif
 803
 804         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
 805                  msk, (unsigned long long)hmac,
 806                  (unsigned long long)mp_opt->ahmac);
 807
 808         return hmac == mp_opt->ahmac;
 809 }
 810
 811 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb,
 812                             struct tcp_options_received *opt_rx)
 813 {
 814         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 815         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 816         struct mptcp_options_received mp_opt;
 817         struct mptcp_ext *mpext;
 818
 819         mptcp_get_options(skb, &mp_opt);
 820         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
 821                 return;
 822
 823         if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
 824                 struct mptcp_addr_info addr;
 825
 826                 addr.port = htons(mp_opt.port);
 827                 addr.id = mp_opt.addr_id;
 828                 if (mp_opt.family == MPTCP_ADDR_IPVERSION_4) {
 829                         addr.family = AF_INET;
 830                         addr.addr = mp_opt.addr;
 831                 }
 832 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 833                 else if (mp_opt.family == MPTCP_ADDR_IPVERSION_6) {
 834                         addr.family = AF_INET6;
 835                         addr.addr6 = mp_opt.addr6;
 836                 }
 837 #endif
 838                 if (!mp_opt.echo)
 839                         mptcp_pm_add_addr_received(msk, &addr);
 840                 mp_opt.add_addr = 0;
 841         }
 842
 843         if (!mp_opt.dss)
 844                 return;
 845
 846         /* we can't wait for recvmsg() to update the ack_seq, otherwise
 847          * monodirectional flows will stuck
 848          */
 849         if (mp_opt.use_ack)
 850                 update_una(msk, &mp_opt);
 851
 852         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
 853         if (!mpext)
 854                 return;
 855
 856         memset(mpext, 0, sizeof(*mpext));
 857
 858         if (mp_opt.use_map) {
 859                 if (mp_opt.mpc_map) {
 860                         /* this is an MP_CAPABLE carrying MPTCP data
 861                          * we know this map the first chunk of data
 862                          */
 863                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
 864                                              &mpext->data_seq);
 865                         mpext->data_seq++;
 866                         mpext->subflow_seq = 1;
 867                         mpext->dsn64 = 1;
 868                         mpext->mpc_map = 1;
 869                         mpext->data_fin = 0;
 870                 } else {
 871                         mpext->data_seq = mp_opt.data_seq;
 872                         mpext->subflow_seq = mp_opt.subflow_seq;
 873                         mpext->dsn64 = mp_opt.dsn64;
 874                         mpext->data_fin = mp_opt.data_fin;
 875                 }
 876                 mpext->data_len = mp_opt.data_len;
 877                 mpext->use_map = 1;
 878         }
 879 }
 880
 881 void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts)
 882 {
 883         if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
 884              OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
 885                 u8 len;
 886
 887                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
 888                         len = TCPOLEN_MPTCP_MPC_SYN;
 889                 else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
 890                         len = TCPOLEN_MPTCP_MPC_SYNACK;
 891                 else if (opts->ext_copy.data_len)
 892                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 893                 else
 894                         len = TCPOLEN_MPTCP_MPC_ACK;
 895
 896                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
 897                                       MPTCP_SUPPORTED_VERSION,
 898                                       MPTCP_CAP_HMAC_SHA256);
 899
 900                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
 901                     opts->suboptions))
 902                         goto mp_capable_done;
 903
 904                 put_unaligned_be64(opts->sndr_key, ptr);
 905                 ptr += 2;
 906                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
 907                         goto mp_capable_done;
 908
 909                 put_unaligned_be64(opts->rcvr_key, ptr);
 910                 ptr += 2;
 911                 if (!opts->ext_copy.data_len)
 912                         goto mp_capable_done;
 913
 914                 put_unaligned_be32(opts->ext_copy.data_len << 16 |
 915                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
 916                 ptr += 1;
 917         }
 918
 919 mp_capable_done:
 920         if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
 921                 if (opts->ahmac)
 922                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 923                                               TCPOLEN_MPTCP_ADD_ADDR, 0,
 924                                               opts->addr_id);
 925                 else
 926                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 927                                               TCPOLEN_MPTCP_ADD_ADDR_BASE,
 928                                               MPTCP_ADDR_ECHO,
 929                                               opts->addr_id);
 930                 memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4);
 931                 ptr += 1;
 932                 if (opts->ahmac) {
 933                         put_unaligned_be64(opts->ahmac, ptr);
 934                         ptr += 2;
 935                 }
 936         }
 937
 938 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 939         if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) {
 940                 if (opts->ahmac)
 941                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 942                                               TCPOLEN_MPTCP_ADD_ADDR6, 0,
 943                                               opts->addr_id);
 944                 else
 945                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 946                                               TCPOLEN_MPTCP_ADD_ADDR6_BASE,
 947                                               MPTCP_ADDR_ECHO,
 948                                               opts->addr_id);
 949                 memcpy((u8 *)ptr, opts->addr6.s6_addr, 16);
 950                 ptr += 4;
 951                 if (opts->ahmac) {
 952                         put_unaligned_be64(opts->ahmac, ptr);
 953                         ptr += 2;
 954                 }
 955         }
 956 #endif
 957
 958         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
 959                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
 960                                       TCPOLEN_MPTCP_RM_ADDR_BASE,
 961                                       0, opts->rm_id);
 962         }
 963
 964         if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
 965                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
 966                                       TCPOLEN_MPTCP_MPJ_SYN,
 967                                       opts->backup, opts->join_id);
 968                 put_unaligned_be32(opts->token, ptr);
 969                 ptr += 1;
 970                 put_unaligned_be32(opts->nonce, ptr);
 971                 ptr += 1;
 972         }
 973
 974         if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
 975                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
 976                                       TCPOLEN_MPTCP_MPJ_SYNACK,
 977                                       opts->backup, opts->join_id);
 978                 put_unaligned_be64(opts->thmac, ptr);
 979                 ptr += 2;
 980                 put_unaligned_be32(opts->nonce, ptr);
 981                 ptr += 1;
 982         }
 983
 984         if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
 985                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
 986                                       TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
 987                 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
 988                 ptr += 5;
 989         }
 990
 991         if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
 992                 struct mptcp_ext *mpext = &opts->ext_copy;
 993                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
 994                 u8 flags = 0;
 995
 996                 if (mpext->use_ack) {
 997                         flags = MPTCP_DSS_HAS_ACK;
 998                         if (mpext->ack64) {
 999                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1000                                 flags |= MPTCP_DSS_ACK64;
1001                         } else {
1002                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1003                         }
1004                 }
1005
1006                 if (mpext->use_map) {
1007                         len += TCPOLEN_MPTCP_DSS_MAP64;
1008
1009                         /* Use only 64-bit mapping flags for now, add
1010                          * support for optional 32-bit mappings later.
1011                          */
1012                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1013                         if (mpext->data_fin)
1014                                 flags |= MPTCP_DSS_DATA_FIN;
1015                 }
1016
1017                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1018
1019                 if (mpext->use_ack) {
1020                         if (mpext->ack64) {
1021                                 put_unaligned_be64(mpext->data_ack, ptr);
1022                                 ptr += 2;
1023                         } else {
1024                                 put_unaligned_be32(mpext->data_ack32, ptr);
1025                                 ptr += 1;
1026                         }
1027                 }
1028
1029                 if (mpext->use_map) {
1030                         put_unaligned_be64(mpext->data_seq, ptr);
1031                         ptr += 2;
1032                         put_unaligned_be32(mpext->subflow_seq, ptr);
1033                         ptr += 1;
1034                         put_unaligned_be32(mpext->data_len << 16 |
1035                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1036                 }
1037         }
1038 }