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 void mptcp_parse_option(const struct sk_buff *skb, const unsigned char *ptr,
  20                         int opsize, struct tcp_options_received *opt_rx)
  21 {
  22         struct mptcp_options_received *mp_opt = &opt_rx->mptcp;
  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 tcp_options_received *opt_rx)
 287 {
 288         const unsigned char *ptr;
 289         const struct tcphdr *th = tcp_hdr(skb);
 290         int length = (th->doff * 4) - sizeof(struct tcphdr);
 291
 292         ptr = (const unsigned char *)(th + 1);
 293
 294         while (length > 0) {
 295                 int opcode = *ptr++;
 296                 int opsize;
 297
 298                 switch (opcode) {
 299                 case TCPOPT_EOL:
 300                         return;
 301                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 302                         length--;
 303                         continue;
 304                 default:
 305                         opsize = *ptr++;
 306                         if (opsize < 2) /* "silly options" */
 307                                 return;
 308                         if (opsize > length)
 309                                 return; /* don't parse partial options */
 310                         if (opcode == TCPOPT_MPTCP)
 311                                 mptcp_parse_option(skb, ptr, opsize, opt_rx);
 312                         ptr += opsize - 2;
 313                         length -= opsize;
 314                 }
 315         }
 316 }
 317
 318 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 319                        unsigned int *size, struct mptcp_out_options *opts)
 320 {
 321         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 322
 323         /* we will use snd_isn to detect first pkt [re]transmission
 324          * in mptcp_established_options_mp()
 325          */
 326         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 327         if (subflow->request_mptcp) {
 328                 pr_debug("local_key=%llu", subflow->local_key);
 329                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 330                 opts->sndr_key = subflow->local_key;
 331                 *size = TCPOLEN_MPTCP_MPC_SYN;
 332                 return true;
 333         } else if (subflow->request_join) {
 334                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 335                          subflow->local_nonce);
 336                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 337                 opts->join_id = subflow->local_id;
 338                 opts->token = subflow->remote_token;
 339                 opts->nonce = subflow->local_nonce;
 340                 opts->backup = subflow->request_bkup;
 341                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 342                 return true;
 343         }
 344         return false;
 345 }
 346
 347 void mptcp_rcv_synsent(struct sock *sk)
 348 {
 349         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 350         struct tcp_sock *tp = tcp_sk(sk);
 351
 352         if (subflow->request_mptcp && tp->rx_opt.mptcp.mp_capable) {
 353                 subflow->mp_capable = 1;
 354                 subflow->can_ack = 1;
 355                 subflow->remote_key = tp->rx_opt.mptcp.sndr_key;
 356                 pr_debug("subflow=%p, remote_key=%llu", subflow,
 357                          subflow->remote_key);
 358         } else if (subflow->request_join && tp->rx_opt.mptcp.mp_join) {
 359                 subflow->mp_join = 1;
 360                 subflow->thmac = tp->rx_opt.mptcp.thmac;
 361                 subflow->remote_nonce = tp->rx_opt.mptcp.nonce;
 362                 pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u", subflow,
 363                          subflow->thmac, subflow->remote_nonce);
 364         } else if (subflow->request_mptcp) {
 365                 tcp_sk(sk)->is_mptcp = 0;
 366         }
 367 }
 368
 369 /* MP_JOIN client subflow must wait for 4th ack before sending any data:
 370  * TCP can't schedule delack timer before the subflow is fully established.
 371  * MPTCP uses the delack timer to do 3rd ack retransmissions
 372  */
 373 static void schedule_3rdack_retransmission(struct sock *sk)
 374 {
 375         struct inet_connection_sock *icsk = inet_csk(sk);
 376         struct tcp_sock *tp = tcp_sk(sk);
 377         unsigned long timeout;
 378
 379         /* reschedule with a timeout above RTT, as we must look only for drop */
 380         if (tp->srtt_us)
 381                 timeout = tp->srtt_us << 1;
 382         else
 383                 timeout = TCP_TIMEOUT_INIT;
 384
 385         WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 386         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 387         icsk->icsk_ack.timeout = timeout;
 388         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 389 }
 390
 391 static void clear_3rdack_retransmission(struct sock *sk)
 392 {
 393         struct inet_connection_sock *icsk = inet_csk(sk);
 394
 395         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 396         icsk->icsk_ack.timeout = 0;
 397         icsk->icsk_ack.ato = 0;
 398         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 399 }
 400
 401 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 402                                          unsigned int *size,
 403                                          unsigned int remaining,
 404                                          struct mptcp_out_options *opts)
 405 {
 406         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 407         struct mptcp_ext *mpext;
 408         unsigned int data_len;
 409
 410         /* When skb is not available, we better over-estimate the emitted
 411          * options len. A full DSS option (28 bytes) is longer than
 412          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 413          * tell the caller to defer the estimate to
 414          * mptcp_established_options_dss(), which will reserve enough space.
 415          */
 416         if (!skb)
 417                 return false;
 418
 419         /* MPC/MPJ needed only on 3rd ack packet */
 420         if (subflow->fully_established ||
 421             subflow->snd_isn != TCP_SKB_CB(skb)->seq)
 422                 return false;
 423
 424         if (subflow->mp_capable) {
 425                 mpext = mptcp_get_ext(skb);
 426                 data_len = mpext ? mpext->data_len : 0;
 427
 428                 /* we will check ext_copy.data_len in mptcp_write_options() to
 429                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 430                  * TCPOLEN_MPTCP_MPC_ACK
 431                  */
 432                 opts->ext_copy.data_len = data_len;
 433                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 434                 opts->sndr_key = subflow->local_key;
 435                 opts->rcvr_key = subflow->remote_key;
 436
 437                 /* Section 3.1.
 438                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 439                  * packets that start the first subflow of an MPTCP connection,
 440                  * as well as the first packet that carries data
 441                  */
 442                 if (data_len > 0)
 443                         *size = ALIGN(TCPOLEN_MPTCP_MPC_ACK_DATA, 4);
 444                 else
 445                         *size = TCPOLEN_MPTCP_MPC_ACK;
 446
 447                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 448                          subflow, subflow->local_key, subflow->remote_key,
 449                          data_len);
 450
 451                 return true;
 452         } else if (subflow->mp_join) {
 453                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 454                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 455                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 456                 pr_debug("subflow=%p", subflow);
 457
 458                 schedule_3rdack_retransmission(sk);
 459                 return true;
 460         }
 461         return false;
 462 }
 463
 464 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 465                                  struct mptcp_ext *ext)
 466 {
 467         if (!ext->use_map) {
 468                 /* RFC6824 requires a DSS mapping with specific values
 469                  * if DATA_FIN is set but no data payload is mapped
 470                  */
 471                 ext->data_fin = 1;
 472                 ext->use_map = 1;
 473                 ext->dsn64 = 1;
 474                 ext->data_seq = subflow->data_fin_tx_seq;
 475                 ext->subflow_seq = 0;
 476                 ext->data_len = 1;
 477         } else if (ext->data_seq + ext->data_len == subflow->data_fin_tx_seq) {
 478                 /* If there's an existing DSS mapping and it is the
 479                  * final mapping, DATA_FIN consumes 1 additional byte of
 480                  * mapping space.
 481                  */
 482                 ext->data_fin = 1;
 483                 ext->data_len++;
 484         }
 485 }
 486
 487 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 488                                           unsigned int *size,
 489                                           unsigned int remaining,
 490                                           struct mptcp_out_options *opts)
 491 {
 492         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 493         unsigned int dss_size = 0;
 494         struct mptcp_ext *mpext;
 495         struct mptcp_sock *msk;
 496         unsigned int ack_size;
 497         bool ret = false;
 498         u8 tcp_fin;
 499
 500         if (skb) {
 501                 mpext = mptcp_get_ext(skb);
 502                 tcp_fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
 503         } else {
 504                 mpext = NULL;
 505                 tcp_fin = 0;
 506         }
 507
 508         if (!skb || (mpext && mpext->use_map) || tcp_fin) {
 509                 unsigned int map_size;
 510
 511                 map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 512
 513                 remaining -= map_size;
 514                 dss_size = map_size;
 515                 if (mpext)
 516                         opts->ext_copy = *mpext;
 517
 518                 if (skb && tcp_fin && subflow->data_fin_tx_enable)
 519                         mptcp_write_data_fin(subflow, &opts->ext_copy);
 520                 ret = true;
 521         }
 522
 523         /* passive sockets msk will set the 'can_ack' after accept(), even
 524          * if the first subflow may have the already the remote key handy
 525          */
 526         opts->ext_copy.use_ack = 0;
 527         msk = mptcp_sk(subflow->conn);
 528         if (!READ_ONCE(msk->can_ack)) {
 529                 *size = ALIGN(dss_size, 4);
 530                 return ret;
 531         }
 532
 533         ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 534
 535         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 536         if (dss_size == 0)
 537                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 538
 539         dss_size += ack_size;
 540
 541         opts->ext_copy.data_ack = msk->ack_seq;
 542         opts->ext_copy.ack64 = 1;
 543         opts->ext_copy.use_ack = 1;
 544
 545         *size = ALIGN(dss_size, 4);
 546         return true;
 547 }
 548
 549 static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 550                                   struct in_addr *addr)
 551 {
 552         u8 hmac[MPTCP_ADDR_HMAC_LEN];
 553         u8 msg[7];
 554
 555         msg[0] = addr_id;
 556         memcpy(&msg[1], &addr->s_addr, 4);
 557         msg[5] = 0;
 558         msg[6] = 0;
 559
 560         mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac);
 561
 562         return get_unaligned_be64(hmac);
 563 }
 564
 565 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 566 static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id,
 567                                    struct in6_addr *addr)
 568 {
 569         u8 hmac[MPTCP_ADDR_HMAC_LEN];
 570         u8 msg[19];
 571
 572         msg[0] = addr_id;
 573         memcpy(&msg[1], &addr->s6_addr, 16);
 574         msg[17] = 0;
 575         msg[18] = 0;
 576
 577         mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac);
 578
 579         return get_unaligned_be64(hmac);
 580 }
 581 #endif
 582
 583 static bool mptcp_established_options_addr(struct sock *sk,
 584                                            unsigned int *size,
 585                                            unsigned int remaining,
 586                                            struct mptcp_out_options *opts)
 587 {
 588         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 589         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 590         struct mptcp_addr_info saddr;
 591         int len;
 592
 593         if (!mptcp_pm_should_signal(msk) ||
 594             !(mptcp_pm_addr_signal(msk, remaining, &saddr)))
 595                 return false;
 596
 597         len = mptcp_add_addr_len(saddr.family);
 598         if (remaining < len)
 599                 return false;
 600
 601         *size = len;
 602         opts->addr_id = saddr.id;
 603         if (saddr.family == AF_INET) {
 604                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 605                 opts->addr = saddr.addr;
 606                 opts->ahmac = add_addr_generate_hmac(msk->local_key,
 607                                                      msk->remote_key,
 608                                                      opts->addr_id,
 609                                                      &opts->addr);
 610         }
 611 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 612         else if (saddr.family == AF_INET6) {
 613                 opts->suboptions |= OPTION_MPTCP_ADD_ADDR6;
 614                 opts->addr6 = saddr.addr6;
 615                 opts->ahmac = add_addr6_generate_hmac(msk->local_key,
 616                                                       msk->remote_key,
 617                                                       opts->addr_id,
 618                                                       &opts->addr6);
 619         }
 620 #endif
 621         pr_debug("addr_id=%d, ahmac=%llu", opts->addr_id, opts->ahmac);
 622
 623         return true;
 624 }
 625
 626 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 627                                unsigned int *size, unsigned int remaining,
 628                                struct mptcp_out_options *opts)
 629 {
 630         unsigned int opt_size = 0;
 631         bool ret = false;
 632
 633         opts->suboptions = 0;
 634
 635         if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts))
 636                 ret = true;
 637         else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining,
 638                                                opts))
 639                 ret = true;
 640
 641         /* we reserved enough space for the above options, and exceeding the
 642          * TCP option space would be fatal
 643          */
 644         if (WARN_ON_ONCE(opt_size > remaining))
 645                 return false;
 646
 647         *size += opt_size;
 648         remaining -= opt_size;
 649         if (mptcp_established_options_addr(sk, &opt_size, remaining, opts)) {
 650                 *size += opt_size;
 651                 remaining -= opt_size;
 652                 ret = true;
 653         }
 654
 655         return ret;
 656 }
 657
 658 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 659                           struct mptcp_out_options *opts)
 660 {
 661         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 662
 663         if (subflow_req->mp_capable) {
 664                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 665                 opts->sndr_key = subflow_req->local_key;
 666                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 667                 pr_debug("subflow_req=%p, local_key=%llu",
 668                          subflow_req, subflow_req->local_key);
 669                 return true;
 670         } else if (subflow_req->mp_join) {
 671                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 672                 opts->backup = subflow_req->backup;
 673                 opts->join_id = subflow_req->local_id;
 674                 opts->thmac = subflow_req->thmac;
 675                 opts->nonce = subflow_req->local_nonce;
 676                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 677                          subflow_req, opts->backup, opts->join_id,
 678                          opts->thmac, opts->nonce);
 679                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 680                 return true;
 681         }
 682         return false;
 683 }
 684
 685 static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
 686                                     struct mptcp_subflow_context *subflow,
 687                                     struct sk_buff *skb,
 688                                     struct mptcp_options_received *mp_opt)
 689 {
 690         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 691          * will make the subflow fully established
 692          */
 693         if (likely(subflow->fully_established)) {
 694                 /* on passive sockets, check for 3rd ack retransmission
 695                  * note that msk is always set by subflow_syn_recv_sock()
 696                  * for mp_join subflows
 697                  */
 698                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 699                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 700                     subflow->mp_join && mp_opt->mp_join &&
 701                     READ_ONCE(msk->pm.server_side))
 702                         tcp_send_ack(sk);
 703                 goto fully_established;
 704         }
 705
 706         /* we should process OoO packets before the first subflow is fully
 707          * established, but not expected for MP_JOIN subflows
 708          */
 709         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1)
 710                 return subflow->mp_capable;
 711
 712         if (mp_opt->use_ack) {
 713                 /* subflows are fully established as soon as we get any
 714                  * additional ack.
 715                  */
 716                 subflow->fully_established = 1;
 717                 goto fully_established;
 718         }
 719
 720         WARN_ON_ONCE(subflow->can_ack);
 721
 722         /* If the first established packet does not contain MP_CAPABLE + data
 723          * then fallback to TCP
 724          */
 725         if (!mp_opt->mp_capable) {
 726                 subflow->mp_capable = 0;
 727                 tcp_sk(sk)->is_mptcp = 0;
 728                 return false;
 729         }
 730
 731         subflow->fully_established = 1;
 732         subflow->remote_key = mp_opt->sndr_key;
 733         subflow->can_ack = 1;
 734
 735 fully_established:
 736         if (likely(subflow->pm_notified))
 737                 return true;
 738
 739         subflow->pm_notified = 1;
 740         if (subflow->mp_join) {
 741                 clear_3rdack_retransmission(sk);
 742                 mptcp_pm_subflow_established(msk, subflow);
 743         } else {
 744                 mptcp_pm_fully_established(msk);
 745         }
 746         return true;
 747 }
 748
 749 static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)
 750 {
 751         u32 old_ack32, cur_ack32;
 752
 753         if (use_64bit)
 754                 return cur_ack;
 755
 756         old_ack32 = (u32)old_ack;
 757         cur_ack32 = (u32)cur_ack;
 758         cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32;
 759         if (unlikely(before(cur_ack32, old_ack32)))
 760                 return cur_ack + (1LL << 32);
 761         return cur_ack;
 762 }
 763
 764 static void update_una(struct mptcp_sock *msk,
 765                        struct mptcp_options_received *mp_opt)
 766 {
 767         u64 new_snd_una, snd_una, old_snd_una = atomic64_read(&msk->snd_una);
 768         u64 write_seq = READ_ONCE(msk->write_seq);
 769
 770         /* avoid ack expansion on update conflict, to reduce the risk of
 771          * wrongly expanding to a future ack sequence number, which is way
 772          * more dangerous than missing an ack
 773          */
 774         new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 775
 776         /* ACK for data not even sent yet? Ignore. */
 777         if (after64(new_snd_una, write_seq))
 778                 new_snd_una = old_snd_una;
 779
 780         while (after64(new_snd_una, old_snd_una)) {
 781                 snd_una = old_snd_una;
 782                 old_snd_una = atomic64_cmpxchg(&msk->snd_una, snd_una,
 783                                                new_snd_una);
 784                 if (old_snd_una == snd_una) {
 785                         mptcp_data_acked((struct sock *)msk);
 786                         break;
 787                 }
 788         }
 789 }
 790
 791 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
 792                                 struct mptcp_options_received *mp_opt)
 793 {
 794         u64 hmac = 0;
 795
 796         if (mp_opt->echo)
 797                 return true;
 798
 799         if (mp_opt->family == MPTCP_ADDR_IPVERSION_4)
 800                 hmac = add_addr_generate_hmac(msk->remote_key,
 801                                               msk->local_key,
 802                                               mp_opt->addr_id, &mp_opt->addr);
 803 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 804         else
 805                 hmac = add_addr6_generate_hmac(msk->remote_key,
 806                                                msk->local_key,
 807                                                mp_opt->addr_id, &mp_opt->addr6);
 808 #endif
 809
 810         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
 811                  msk, (unsigned long long)hmac,
 812                  (unsigned long long)mp_opt->ahmac);
 813
 814         return hmac == mp_opt->ahmac;
 815 }
 816
 817 void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb,
 818                             struct tcp_options_received *opt_rx)
 819 {
 820         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 821         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 822         struct mptcp_options_received *mp_opt;
 823         struct mptcp_ext *mpext;
 824
 825         mp_opt = &opt_rx->mptcp;
 826         if (!check_fully_established(msk, sk, subflow, skb, mp_opt))
 827                 return;
 828
 829         if (mp_opt->add_addr && add_addr_hmac_valid(msk, mp_opt)) {
 830                 struct mptcp_addr_info addr;
 831
 832                 addr.port = htons(mp_opt->port);
 833                 addr.id = mp_opt->addr_id;
 834                 if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) {
 835                         addr.family = AF_INET;
 836                         addr.addr = mp_opt->addr;
 837                 }
 838 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 839                 else if (mp_opt->family == MPTCP_ADDR_IPVERSION_6) {
 840                         addr.family = AF_INET6;
 841                         addr.addr6 = mp_opt->addr6;
 842                 }
 843 #endif
 844                 if (!mp_opt->echo)
 845                         mptcp_pm_add_addr_received(msk, &addr);
 846                 mp_opt->add_addr = 0;
 847         }
 848
 849         if (!mp_opt->dss)
 850                 return;
 851
 852         /* we can't wait for recvmsg() to update the ack_seq, otherwise
 853          * monodirectional flows will stuck
 854          */
 855         if (mp_opt->use_ack)
 856                 update_una(msk, mp_opt);
 857
 858         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
 859         if (!mpext)
 860                 return;
 861
 862         memset(mpext, 0, sizeof(*mpext));
 863
 864         if (mp_opt->use_map) {
 865                 if (mp_opt->mpc_map) {
 866                         /* this is an MP_CAPABLE carrying MPTCP data
 867                          * we know this map the first chunk of data
 868                          */
 869                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
 870                                              &mpext->data_seq);
 871                         mpext->data_seq++;
 872                         mpext->subflow_seq = 1;
 873                         mpext->dsn64 = 1;
 874                         mpext->mpc_map = 1;
 875                 } else {
 876                         mpext->data_seq = mp_opt->data_seq;
 877                         mpext->subflow_seq = mp_opt->subflow_seq;
 878                         mpext->dsn64 = mp_opt->dsn64;
 879                         mpext->data_fin = mp_opt->data_fin;
 880                 }
 881                 mpext->data_len = mp_opt->data_len;
 882                 mpext->use_map = 1;
 883         }
 884 }
 885
 886 void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts)
 887 {
 888         if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
 889              OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
 890                 u8 len;
 891
 892                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions)
 893                         len = TCPOLEN_MPTCP_MPC_SYN;
 894                 else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions)
 895                         len = TCPOLEN_MPTCP_MPC_SYNACK;
 896                 else if (opts->ext_copy.data_len)
 897                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 898                 else
 899                         len = TCPOLEN_MPTCP_MPC_ACK;
 900
 901                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
 902                                       MPTCP_SUPPORTED_VERSION,
 903                                       MPTCP_CAP_HMAC_SHA256);
 904
 905                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
 906                     opts->suboptions))
 907                         goto mp_capable_done;
 908
 909                 put_unaligned_be64(opts->sndr_key, ptr);
 910                 ptr += 2;
 911                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
 912                         goto mp_capable_done;
 913
 914                 put_unaligned_be64(opts->rcvr_key, ptr);
 915                 ptr += 2;
 916                 if (!opts->ext_copy.data_len)
 917                         goto mp_capable_done;
 918
 919                 put_unaligned_be32(opts->ext_copy.data_len << 16 |
 920                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
 921                 ptr += 1;
 922         }
 923
 924 mp_capable_done:
 925         if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
 926                 if (opts->ahmac)
 927                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 928                                               TCPOLEN_MPTCP_ADD_ADDR, 0,
 929                                               opts->addr_id);
 930                 else
 931                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 932                                               TCPOLEN_MPTCP_ADD_ADDR_BASE,
 933                                               MPTCP_ADDR_ECHO,
 934                                               opts->addr_id);
 935                 memcpy((u8 *)ptr, (u8 *)&opts->addr.s_addr, 4);
 936                 ptr += 1;
 937                 if (opts->ahmac) {
 938                         put_unaligned_be64(opts->ahmac, ptr);
 939                         ptr += 2;
 940                 }
 941         }
 942
 943 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 944         if (OPTION_MPTCP_ADD_ADDR6 & opts->suboptions) {
 945                 if (opts->ahmac)
 946                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 947                                               TCPOLEN_MPTCP_ADD_ADDR6, 0,
 948                                               opts->addr_id);
 949                 else
 950                         *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
 951                                               TCPOLEN_MPTCP_ADD_ADDR6_BASE,
 952                                               MPTCP_ADDR_ECHO,
 953                                               opts->addr_id);
 954                 memcpy((u8 *)ptr, opts->addr6.s6_addr, 16);
 955                 ptr += 4;
 956                 if (opts->ahmac) {
 957                         put_unaligned_be64(opts->ahmac, ptr);
 958                         ptr += 2;
 959                 }
 960         }
 961 #endif
 962
 963         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
 964                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
 965                                       TCPOLEN_MPTCP_RM_ADDR_BASE,
 966                                       0, opts->rm_id);
 967         }
 968
 969         if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
 970                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
 971                                       TCPOLEN_MPTCP_MPJ_SYN,
 972                                       opts->backup, opts->join_id);
 973                 put_unaligned_be32(opts->token, ptr);
 974                 ptr += 1;
 975                 put_unaligned_be32(opts->nonce, ptr);
 976                 ptr += 1;
 977         }
 978
 979         if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
 980                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
 981                                       TCPOLEN_MPTCP_MPJ_SYNACK,
 982                                       opts->backup, opts->join_id);
 983                 put_unaligned_be64(opts->thmac, ptr);
 984                 ptr += 2;
 985                 put_unaligned_be32(opts->nonce, ptr);
 986                 ptr += 1;
 987         }
 988
 989         if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
 990                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
 991                                       TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
 992                 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
 993                 ptr += 5;
 994         }
 995
 996         if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
 997                 struct mptcp_ext *mpext = &opts->ext_copy;
 998                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
 999                 u8 flags = 0;
1000
1001                 if (mpext->use_ack) {
1002                         len += TCPOLEN_MPTCP_DSS_ACK64;
1003                         flags = MPTCP_DSS_HAS_ACK | MPTCP_DSS_ACK64;
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                         put_unaligned_be64(mpext->data_ack, ptr);
1021                         ptr += 2;
1022                 }
1023
1024                 if (mpext->use_map) {
1025                         put_unaligned_be64(mpext->data_seq, ptr);
1026                         ptr += 2;
1027                         put_unaligned_be32(mpext->subflow_seq, ptr);
1028                         ptr += 1;
1029                         put_unaligned_be32(mpext->data_len << 16 |
1030                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1031                 }
1032         }
1033 }