net/mptcp/options.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Multipath TCP
   3  *
   4  * Copyright (c) 2017 - 2019, Intel Corporation.
   5  */
   6
   7 #define pr_fmt(fmt) "MPTCP: " fmt
   8
   9 #include <linux/kernel.h>
  10 #include <crypto/sha2.h>
  11 #include <net/tcp.h>
  12 #include <net/mptcp.h>
  13 #include "protocol.h"
  14 #include "mib.h"
  15
  16 #include <trace/events/mptcp.h>
  17
  18 static bool mptcp_cap_flag_sha256(u8 flags)
  19 {
  20         return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
  21 }
  22
  23 static void mptcp_parse_option(const struct sk_buff *skb,
  24                                const unsigned char *ptr, int opsize,
  25                                struct mptcp_options_received *mp_opt)
  26 {
  27         u8 subtype = *ptr >> 4;
  28         int expected_opsize;
  29         u8 version;
  30         u8 flags;
  31         u8 i;
  32
  33         switch (subtype) {
  34         case MPTCPOPT_MP_CAPABLE:
  35                 /* strict size checking */
  36                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
  37                         if (skb->len > tcp_hdr(skb)->doff << 2)
  38                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
  39                         else
  40                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
  41                 } else {
  42                         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)
  43                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
  44                         else
  45                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
  46                 }
  47
  48                 /* Cfr RFC 8684 Section 3.3.0:
  49                  * If a checksum is present but its use had
  50                  * not been negotiated in the MP_CAPABLE handshake, the receiver MUST
  51                  * close the subflow with a RST, as it is not behaving as negotiated.
  52                  * If a checksum is not present when its use has been negotiated, the
  53                  * receiver MUST close the subflow with a RST, as it is considered
  54                  * broken
  55                  * We parse even option with mismatching csum presence, so that
  56                  * later in subflow_data_ready we can trigger the reset.
  57                  */
  58                 if (opsize != expected_opsize &&
  59                     (expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA ||
  60                      opsize != TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM))
  61                         break;
  62
  63                 /* try to be gentle vs future versions on the initial syn */
  64                 version = *ptr++ & MPTCP_VERSION_MASK;
  65                 if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
  66                         if (version != MPTCP_SUPPORTED_VERSION)
  67                                 break;
  68                 } else if (version < MPTCP_SUPPORTED_VERSION) {
  69                         break;
  70                 }
  71
  72                 flags = *ptr++;
  73                 if (!mptcp_cap_flag_sha256(flags) ||
  74                     (flags & MPTCP_CAP_EXTENSIBILITY))
  75                         break;
  76
  77                 /* RFC 6824, Section 3.1:
  78                  * "For the Checksum Required bit (labeled "A"), if either
  79                  * host requires the use of checksums, checksums MUST be used.
  80                  * In other words, the only way for checksums not to be used
  81                  * is if both hosts in their SYNs set A=0."
  82                  */
  83                 if (flags & MPTCP_CAP_CHECKSUM_REQD)
  84                         mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
  85
  86                 mp_opt->deny_join_id0 = !!(flags & MPTCP_CAP_DENY_JOIN_ID0);
  87
  88                 mp_opt->suboptions |= OPTIONS_MPTCP_MPC;
  89                 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
  90                         mp_opt->sndr_key = get_unaligned_be64(ptr);
  91                         ptr += 8;
  92                 }
  93                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
  94                         mp_opt->rcvr_key = get_unaligned_be64(ptr);
  95                         ptr += 8;
  96                 }
  97                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK_DATA) {
  98                         /* Section 3.1.:
  99                          * "the data parameters in a MP_CAPABLE are semantically
 100                          * equivalent to those in a DSS option and can be used
 101                          * interchangeably."
 102                          */
 103                         mp_opt->suboptions |= OPTION_MPTCP_DSS;
 104                         mp_opt->use_map = 1;
 105                         mp_opt->mpc_map = 1;
 106                         mp_opt->data_len = get_unaligned_be16(ptr);
 107                         ptr += 2;
 108                 }
 109                 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
 110                         mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
 111                         mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 112                         ptr += 2;
 113                 }
 114                 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u",
 115                          version, flags, opsize, mp_opt->sndr_key,
 116                          mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum);
 117                 break;
 118
 119         case MPTCPOPT_MP_JOIN:
 120                 mp_opt->suboptions |= OPTIONS_MPTCP_MPJ;
 121                 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 122                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 123                         mp_opt->join_id = *ptr++;
 124                         mp_opt->token = get_unaligned_be32(ptr);
 125                         ptr += 4;
 126                         mp_opt->nonce = get_unaligned_be32(ptr);
 127                         ptr += 4;
 128                         pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
 129                                  mp_opt->backup, mp_opt->join_id,
 130                                  mp_opt->token, mp_opt->nonce);
 131                 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
 132                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 133                         mp_opt->join_id = *ptr++;
 134                         mp_opt->thmac = get_unaligned_be64(ptr);
 135                         ptr += 8;
 136                         mp_opt->nonce = get_unaligned_be32(ptr);
 137                         ptr += 4;
 138                         pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
 139                                  mp_opt->backup, mp_opt->join_id,
 140                                  mp_opt->thmac, mp_opt->nonce);
 141                 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 142                         ptr += 2;
 143                         memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 144                         pr_debug("MP_JOIN hmac");
 145                 } else {
 146                         mp_opt->suboptions &= ~OPTIONS_MPTCP_MPJ;
 147                 }
 148                 break;
 149
 150         case MPTCPOPT_DSS:
 151                 pr_debug("DSS");
 152                 ptr++;
 153
 154                 /* we must clear 'mpc_map' be able to detect MP_CAPABLE
 155                  * map vs DSS map in mptcp_incoming_options(), and reconstruct
 156                  * map info accordingly
 157                  */
 158                 mp_opt->mpc_map = 0;
 159                 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 160                 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 161                 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 162                 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 163                 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 164                 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 165
 166                 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
 167                          mp_opt->data_fin, mp_opt->dsn64,
 168                          mp_opt->use_map, mp_opt->ack64,
 169                          mp_opt->use_ack);
 170
 171                 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 172
 173                 if (mp_opt->use_ack) {
 174                         if (mp_opt->ack64)
 175                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 176                         else
 177                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 178                 }
 179
 180                 if (mp_opt->use_map) {
 181                         if (mp_opt->dsn64)
 182                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 183                         else
 184                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 185                 }
 186
 187                 /* Always parse any csum presence combination, we will enforce
 188                  * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
 189                  */
 190                 if (opsize != expected_opsize &&
 191                     opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 192                         break;
 193
 194                 mp_opt->suboptions |= OPTION_MPTCP_DSS;
 195                 if (mp_opt->use_ack) {
 196                         if (mp_opt->ack64) {
 197                                 mp_opt->data_ack = get_unaligned_be64(ptr);
 198                                 ptr += 8;
 199                         } else {
 200                                 mp_opt->data_ack = get_unaligned_be32(ptr);
 201                                 ptr += 4;
 202                         }
 203
 204                         pr_debug("data_ack=%llu", mp_opt->data_ack);
 205                 }
 206
 207                 if (mp_opt->use_map) {
 208                         if (mp_opt->dsn64) {
 209                                 mp_opt->data_seq = get_unaligned_be64(ptr);
 210                                 ptr += 8;
 211                         } else {
 212                                 mp_opt->data_seq = get_unaligned_be32(ptr);
 213                                 ptr += 4;
 214                         }
 215
 216                         mp_opt->subflow_seq = get_unaligned_be32(ptr);
 217                         ptr += 4;
 218
 219                         mp_opt->data_len = get_unaligned_be16(ptr);
 220                         ptr += 2;
 221
 222                         if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
 223                                 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 224                                 mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
 225                                 ptr += 2;
 226                         }
 227
 228                         pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u",
 229                                  mp_opt->data_seq, mp_opt->subflow_seq,
 230                                  mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD),
 231                                  mp_opt->csum);
 232                 }
 233
 234                 break;
 235
 236         case MPTCPOPT_ADD_ADDR:
 237                 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 238                 if (!mp_opt->echo) {
 239                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 240                             opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 241                                 mp_opt->addr.family = AF_INET;
 242 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 243                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 244                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 245                                 mp_opt->addr.family = AF_INET6;
 246 #endif
 247                         else
 248                                 break;
 249                 } else {
 250                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 251                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 252                                 mp_opt->addr.family = AF_INET;
 253 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 254                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 255                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 256                                 mp_opt->addr.family = AF_INET6;
 257 #endif
 258                         else
 259                                 break;
 260                 }
 261
 262                 mp_opt->suboptions |= OPTION_MPTCP_ADD_ADDR;
 263                 mp_opt->addr.id = *ptr++;
 264                 mp_opt->addr.port = 0;
 265                 mp_opt->ahmac = 0;
 266                 if (mp_opt->addr.family == AF_INET) {
 267                         memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
 268                         ptr += 4;
 269                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 270                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 271                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 272                                 ptr += 2;
 273                         }
 274                 }
 275 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 276                 else {
 277                         memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16);
 278                         ptr += 16;
 279                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 280                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 281                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 282                                 ptr += 2;
 283                         }
 284                 }
 285 #endif
 286                 if (!mp_opt->echo) {
 287                         mp_opt->ahmac = get_unaligned_be64(ptr);
 288                         ptr += 8;
 289                 }
 290                 pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d",
 291                          (mp_opt->addr.family == AF_INET6) ? "6" : "",
 292                          mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
 293                 break;
 294
 295         case MPTCPOPT_RM_ADDR:
 296                 if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
 297                     opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
 298                         break;
 299
 300                 ptr++;
 301
 302                 mp_opt->suboptions |= OPTION_MPTCP_RM_ADDR;
 303                 mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
 304                 for (i = 0; i < mp_opt->rm_list.nr; i++)
 305                         mp_opt->rm_list.ids[i] = *ptr++;
 306                 pr_debug("RM_ADDR: rm_list_nr=%d", mp_opt->rm_list.nr);
 307                 break;
 308
 309         case MPTCPOPT_MP_PRIO:
 310                 if (opsize != TCPOLEN_MPTCP_PRIO)
 311                         break;
 312
 313                 mp_opt->suboptions |= OPTION_MPTCP_PRIO;
 314                 mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
 315                 pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
 316                 break;
 317
 318         case MPTCPOPT_MP_FASTCLOSE:
 319                 if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 320                         break;
 321
 322                 ptr += 2;
 323                 mp_opt->rcvr_key = get_unaligned_be64(ptr);
 324                 ptr += 8;
 325                 mp_opt->suboptions |= OPTION_MPTCP_FASTCLOSE;
 326                 break;
 327
 328         case MPTCPOPT_RST:
 329                 if (opsize != TCPOLEN_MPTCP_RST)
 330                         break;
 331
 332                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 333                         break;
 334
 335                 mp_opt->suboptions |= OPTION_MPTCP_RST;
 336                 flags = *ptr++;
 337                 mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
 338                 mp_opt->reset_reason = *ptr;
 339                 break;
 340
 341         case MPTCPOPT_MP_FAIL:
 342                 if (opsize != TCPOLEN_MPTCP_FAIL)
 343                         break;
 344
 345                 ptr += 2;
 346                 mp_opt->suboptions |= OPTION_MPTCP_FAIL;
 347                 mp_opt->fail_seq = get_unaligned_be64(ptr);
 348                 pr_debug("MP_FAIL: data_seq=%llu", mp_opt->fail_seq);
 349                 break;
 350
 351         default:
 352                 break;
 353         }
 354 }
 355
 356 void mptcp_get_options(const struct sock *sk,
 357                        const struct sk_buff *skb,
 358                        struct mptcp_options_received *mp_opt)
 359 {
 360         const struct tcphdr *th = tcp_hdr(skb);
 361         const unsigned char *ptr;
 362         int length;
 363
 364         /* initialize option status */
 365         mp_opt->suboptions = 0;
 366
 367         length = (th->doff * 4) - sizeof(struct tcphdr);
 368         ptr = (const unsigned char *)(th + 1);
 369
 370         while (length > 0) {
 371                 int opcode = *ptr++;
 372                 int opsize;
 373
 374                 switch (opcode) {
 375                 case TCPOPT_EOL:
 376                         return;
 377                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 378                         length--;
 379                         continue;
 380                 default:
 381                         if (length < 2)
 382                                 return;
 383                         opsize = *ptr++;
 384                         if (opsize < 2) /* "silly options" */
 385                                 return;
 386                         if (opsize > length)
 387                                 return; /* don't parse partial options */
 388                         if (opcode == TCPOPT_MPTCP)
 389                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 390                         ptr += opsize - 2;
 391                         length -= opsize;
 392                 }
 393         }
 394 }
 395
 396 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 397                        unsigned int *size, struct mptcp_out_options *opts)
 398 {
 399         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 400
 401         /* we will use snd_isn to detect first pkt [re]transmission
 402          * in mptcp_established_options_mp()
 403          */
 404         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 405         if (subflow->request_mptcp) {
 406                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 407                 opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
 408                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 409                 *size = TCPOLEN_MPTCP_MPC_SYN;
 410                 return true;
 411         } else if (subflow->request_join) {
 412                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 413                          subflow->local_nonce);
 414                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 415                 opts->join_id = subflow->local_id;
 416                 opts->token = subflow->remote_token;
 417                 opts->nonce = subflow->local_nonce;
 418                 opts->backup = subflow->request_bkup;
 419                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 420                 return true;
 421         }
 422         return false;
 423 }
 424
 425 /* MP_JOIN client subflow must wait for 4th ack before sending any data:
 426  * TCP can't schedule delack timer before the subflow is fully established.
 427  * MPTCP uses the delack timer to do 3rd ack retransmissions
 428  */
 429 static void schedule_3rdack_retransmission(struct sock *sk)
 430 {
 431         struct inet_connection_sock *icsk = inet_csk(sk);
 432         struct tcp_sock *tp = tcp_sk(sk);
 433         unsigned long timeout;
 434
 435         /* reschedule with a timeout above RTT, as we must look only for drop */
 436         if (tp->srtt_us)
 437                 timeout = tp->srtt_us << 1;
 438         else
 439                 timeout = TCP_TIMEOUT_INIT;
 440
 441         WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 442         icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 443         icsk->icsk_ack.timeout = timeout;
 444         sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 445 }
 446
 447 static void clear_3rdack_retransmission(struct sock *sk)
 448 {
 449         struct inet_connection_sock *icsk = inet_csk(sk);
 450
 451         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 452         icsk->icsk_ack.timeout = 0;
 453         icsk->icsk_ack.ato = 0;
 454         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 455 }
 456
 457 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 458                                          bool snd_data_fin_enable,
 459                                          unsigned int *size,
 460                                          unsigned int remaining,
 461                                          struct mptcp_out_options *opts)
 462 {
 463         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 464         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 465         struct mptcp_ext *mpext;
 466         unsigned int data_len;
 467         u8 len;
 468
 469         /* When skb is not available, we better over-estimate the emitted
 470          * options len. A full DSS option (28 bytes) is longer than
 471          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 472          * tell the caller to defer the estimate to
 473          * mptcp_established_options_dss(), which will reserve enough space.
 474          */
 475         if (!skb)
 476                 return false;
 477
 478         /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
 479         if (subflow->fully_established || snd_data_fin_enable ||
 480             subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 481             sk->sk_state != TCP_ESTABLISHED)
 482                 return false;
 483
 484         if (subflow->mp_capable) {
 485                 mpext = mptcp_get_ext(skb);
 486                 data_len = mpext ? mpext->data_len : 0;
 487
 488                 /* we will check ext_copy.data_len in mptcp_write_options() to
 489                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 490                  * TCPOLEN_MPTCP_MPC_ACK
 491                  */
 492                 opts->ext_copy.data_len = data_len;
 493                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 494                 opts->sndr_key = subflow->local_key;
 495                 opts->rcvr_key = subflow->remote_key;
 496                 opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 497                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 498
 499                 /* Section 3.1.
 500                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 501                  * packets that start the first subflow of an MPTCP connection,
 502                  * as well as the first packet that carries data
 503                  */
 504                 if (data_len > 0) {
 505                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 506                         if (opts->csum_reqd) {
 507                                 /* we need to propagate more info to csum the pseudo hdr */
 508                                 opts->ext_copy.data_seq = mpext->data_seq;
 509                                 opts->ext_copy.subflow_seq = mpext->subflow_seq;
 510                                 opts->ext_copy.csum = mpext->csum;
 511                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
 512                         }
 513                         *size = ALIGN(len, 4);
 514                 } else {
 515                         *size = TCPOLEN_MPTCP_MPC_ACK;
 516                 }
 517
 518                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 519                          subflow, subflow->local_key, subflow->remote_key,
 520                          data_len);
 521
 522                 return true;
 523         } else if (subflow->mp_join) {
 524                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 525                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 526                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 527                 pr_debug("subflow=%p", subflow);
 528
 529                 schedule_3rdack_retransmission(sk);
 530                 return true;
 531         }
 532         return false;
 533 }
 534
 535 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 536                                  struct sk_buff *skb, struct mptcp_ext *ext)
 537 {
 538         /* The write_seq value has already been incremented, so the actual
 539          * sequence number for the DATA_FIN is one less.
 540          */
 541         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 542
 543         if (!ext->use_map || !skb->len) {
 544                 /* RFC6824 requires a DSS mapping with specific values
 545                  * if DATA_FIN is set but no data payload is mapped
 546                  */
 547                 ext->data_fin = 1;
 548                 ext->use_map = 1;
 549                 ext->dsn64 = 1;
 550                 ext->data_seq = data_fin_tx_seq;
 551                 ext->subflow_seq = 0;
 552                 ext->data_len = 1;
 553         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 554                 /* If there's an existing DSS mapping and it is the
 555                  * final mapping, DATA_FIN consumes 1 additional byte of
 556                  * mapping space.
 557                  */
 558                 ext->data_fin = 1;
 559                 ext->data_len++;
 560         }
 561 }
 562
 563 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 564                                           bool snd_data_fin_enable,
 565                                           unsigned int *size,
 566                                           unsigned int remaining,
 567                                           struct mptcp_out_options *opts)
 568 {
 569         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 570         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 571         unsigned int dss_size = 0;
 572         struct mptcp_ext *mpext;
 573         unsigned int ack_size;
 574         bool ret = false;
 575         u64 ack_seq;
 576
 577         opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 578         mpext = skb ? mptcp_get_ext(skb) : NULL;
 579
 580         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 581                 unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 582
 583                 if (mpext) {
 584                         if (opts->csum_reqd)
 585                                 map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
 586
 587                         opts->ext_copy = *mpext;
 588                 }
 589
 590                 remaining -= map_size;
 591                 dss_size = map_size;
 592                 if (skb && snd_data_fin_enable)
 593                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 594                 opts->suboptions = OPTION_MPTCP_DSS;
 595                 ret = true;
 596         }
 597
 598         /* passive sockets msk will set the 'can_ack' after accept(), even
 599          * if the first subflow may have the already the remote key handy
 600          */
 601         opts->ext_copy.use_ack = 0;
 602         if (!READ_ONCE(msk->can_ack)) {
 603                 *size = ALIGN(dss_size, 4);
 604                 return ret;
 605         }
 606
 607         ack_seq = READ_ONCE(msk->ack_seq);
 608         if (READ_ONCE(msk->use_64bit_ack)) {
 609                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 610                 opts->ext_copy.data_ack = ack_seq;
 611                 opts->ext_copy.ack64 = 1;
 612         } else {
 613                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 614                 opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
 615                 opts->ext_copy.ack64 = 0;
 616         }
 617         opts->ext_copy.use_ack = 1;
 618         opts->suboptions = OPTION_MPTCP_DSS;
 619         WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 620
 621         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 622         if (dss_size == 0)
 623                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 624
 625         dss_size += ack_size;
 626
 627         *size = ALIGN(dss_size, 4);
 628         return true;
 629 }
 630
 631 static u64 add_addr_generate_hmac(u64 key1, u64 key2,
 632                                   struct mptcp_addr_info *addr)
 633 {
 634         u16 port = ntohs(addr->port);
 635         u8 hmac[SHA256_DIGEST_SIZE];
 636         u8 msg[19];
 637         int i = 0;
 638
 639         msg[i++] = addr->id;
 640         if (addr->family == AF_INET) {
 641                 memcpy(&msg[i], &addr->addr.s_addr, 4);
 642                 i += 4;
 643         }
 644 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 645         else if (addr->family == AF_INET6) {
 646                 memcpy(&msg[i], &addr->addr6.s6_addr, 16);
 647                 i += 16;
 648         }
 649 #endif
 650         msg[i++] = port >> 8;
 651         msg[i++] = port & 0xFF;
 652
 653         mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
 654
 655         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 656 }
 657
 658 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 659                                                unsigned int *size,
 660                                                unsigned int remaining,
 661                                                struct mptcp_out_options *opts)
 662 {
 663         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 664         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 665         bool drop_other_suboptions = false;
 666         unsigned int opt_size = *size;
 667         bool echo;
 668         bool port;
 669         int len;
 670
 671         /* add addr will strip the existing options, be sure to avoid breaking
 672          * MPC/MPJ handshakes
 673          */
 674         if (!mptcp_pm_should_add_signal(msk) ||
 675             (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
 676             !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &opts->addr,
 677                     &echo, &port, &drop_other_suboptions))
 678                 return false;
 679
 680         if (drop_other_suboptions)
 681                 remaining += opt_size;
 682         len = mptcp_add_addr_len(opts->addr.family, echo, port);
 683         if (remaining < len)
 684                 return false;
 685
 686         *size = len;
 687         if (drop_other_suboptions) {
 688                 pr_debug("drop other suboptions");
 689                 opts->suboptions = 0;
 690
 691                 /* note that e.g. DSS could have written into the memory
 692                  * aliased by ahmac, we must reset the field here
 693                  * to avoid appending the hmac even for ADD_ADDR echo
 694                  * options
 695                  */
 696                 opts->ahmac = 0;
 697                 *size -= opt_size;
 698         }
 699         opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 700         if (!echo) {
 701                 opts->ahmac = add_addr_generate_hmac(msk->local_key,
 702                                                      msk->remote_key,
 703                                                      &opts->addr);
 704         }
 705         pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d",
 706                  opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
 707
 708         return true;
 709 }
 710
 711 static bool mptcp_established_options_rm_addr(struct sock *sk,
 712                                               unsigned int *size,
 713                                               unsigned int remaining,
 714                                               struct mptcp_out_options *opts)
 715 {
 716         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 717         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 718         struct mptcp_rm_list rm_list;
 719         int i, len;
 720
 721         if (!mptcp_pm_should_rm_signal(msk) ||
 722             !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
 723                 return false;
 724
 725         len = mptcp_rm_addr_len(&rm_list);
 726         if (len < 0)
 727                 return false;
 728         if (remaining < len)
 729                 return false;
 730
 731         *size = len;
 732         opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 733         opts->rm_list = rm_list;
 734
 735         for (i = 0; i < opts->rm_list.nr; i++)
 736                 pr_debug("rm_list_ids[%d]=%d", i, opts->rm_list.ids[i]);
 737
 738         return true;
 739 }
 740
 741 static bool mptcp_established_options_mp_prio(struct sock *sk,
 742                                               unsigned int *size,
 743                                               unsigned int remaining,
 744                                               struct mptcp_out_options *opts)
 745 {
 746         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 747
 748         /* can't send MP_PRIO with MPC, as they share the same option space:
 749          * 'backup'. Also it makes no sense at all
 750          */
 751         if (!subflow->send_mp_prio ||
 752             ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
 753               OPTION_MPTCP_MPC_ACK) & opts->suboptions))
 754                 return false;
 755
 756         /* account for the trailing 'nop' option */
 757         if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
 758                 return false;
 759
 760         *size = TCPOLEN_MPTCP_PRIO_ALIGN;
 761         opts->suboptions |= OPTION_MPTCP_PRIO;
 762         opts->backup = subflow->request_bkup;
 763
 764         pr_debug("prio=%d", opts->backup);
 765
 766         return true;
 767 }
 768
 769 static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
 770                                                    unsigned int *size,
 771                                                    unsigned int remaining,
 772                                                    struct mptcp_out_options *opts)
 773 {
 774         const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 775
 776         if (remaining < TCPOLEN_MPTCP_RST)
 777                 return false;
 778
 779         *size = TCPOLEN_MPTCP_RST;
 780         opts->suboptions |= OPTION_MPTCP_RST;
 781         opts->reset_transient = subflow->reset_transient;
 782         opts->reset_reason = subflow->reset_reason;
 783
 784         return true;
 785 }
 786
 787 static bool mptcp_established_options_mp_fail(struct sock *sk,
 788                                               unsigned int *size,
 789                                               unsigned int remaining,
 790                                               struct mptcp_out_options *opts)
 791 {
 792         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 793
 794         if (likely(!subflow->send_mp_fail))
 795                 return false;
 796
 797         if (remaining < TCPOLEN_MPTCP_FAIL)
 798                 return false;
 799
 800         *size = TCPOLEN_MPTCP_FAIL;
 801         opts->suboptions |= OPTION_MPTCP_FAIL;
 802         opts->fail_seq = subflow->map_seq;
 803
 804         pr_debug("MP_FAIL fail_seq=%llu", opts->fail_seq);
 805
 806         return true;
 807 }
 808
 809 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 810                                unsigned int *size, unsigned int remaining,
 811                                struct mptcp_out_options *opts)
 812 {
 813         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 814         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 815         unsigned int opt_size = 0;
 816         bool snd_data_fin;
 817         bool ret = false;
 818
 819         opts->suboptions = 0;
 820
 821         if (unlikely(__mptcp_check_fallback(msk)))
 822                 return false;
 823
 824         if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 825                 if (mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
 826                         *size += opt_size;
 827                         remaining -= opt_size;
 828                 }
 829                 if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
 830                         *size += opt_size;
 831                         remaining -= opt_size;
 832                 }
 833                 return true;
 834         }
 835
 836         snd_data_fin = mptcp_data_fin_enabled(msk);
 837         if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 838                 ret = true;
 839         else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts)) {
 840                 ret = true;
 841                 if (mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
 842                         *size += opt_size;
 843                         remaining -= opt_size;
 844                         return true;
 845                 }
 846         }
 847
 848         /* we reserved enough space for the above options, and exceeding the
 849          * TCP option space would be fatal
 850          */
 851         if (WARN_ON_ONCE(opt_size > remaining))
 852                 return false;
 853
 854         *size += opt_size;
 855         remaining -= opt_size;
 856         if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
 857                 *size += opt_size;
 858                 remaining -= opt_size;
 859                 ret = true;
 860         } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 861                 *size += opt_size;
 862                 remaining -= opt_size;
 863                 ret = true;
 864         }
 865
 866         if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
 867                 *size += opt_size;
 868                 remaining -= opt_size;
 869                 ret = true;
 870         }
 871
 872         return ret;
 873 }
 874
 875 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 876                           struct mptcp_out_options *opts)
 877 {
 878         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 879
 880         if (subflow_req->mp_capable) {
 881                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 882                 opts->sndr_key = subflow_req->local_key;
 883                 opts->csum_reqd = subflow_req->csum_reqd;
 884                 opts->allow_join_id0 = subflow_req->allow_join_id0;
 885                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 886                 pr_debug("subflow_req=%p, local_key=%llu",
 887                          subflow_req, subflow_req->local_key);
 888                 return true;
 889         } else if (subflow_req->mp_join) {
 890                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 891                 opts->backup = subflow_req->backup;
 892                 opts->join_id = subflow_req->local_id;
 893                 opts->thmac = subflow_req->thmac;
 894                 opts->nonce = subflow_req->local_nonce;
 895                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 896                          subflow_req, opts->backup, opts->join_id,
 897                          opts->thmac, opts->nonce);
 898                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 899                 return true;
 900         }
 901         return false;
 902 }
 903
 904 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 905                                     struct mptcp_subflow_context *subflow,
 906                                     struct sk_buff *skb,
 907                                     struct mptcp_options_received *mp_opt)
 908 {
 909         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 910          * will make the subflow fully established
 911          */
 912         if (likely(subflow->fully_established)) {
 913                 /* on passive sockets, check for 3rd ack retransmission
 914                  * note that msk is always set by subflow_syn_recv_sock()
 915                  * for mp_join subflows
 916                  */
 917                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 918                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 919                     subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) &&
 920                     READ_ONCE(msk->pm.server_side))
 921                         tcp_send_ack(ssk);
 922                 goto fully_established;
 923         }
 924
 925         /* we must process OoO packets before the first subflow is fully
 926          * established. OoO packets are instead a protocol violation
 927          * for MP_JOIN subflows as the peer must not send any data
 928          * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 929          */
 930         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 931                 if (subflow->mp_join)
 932                         goto reset;
 933                 return subflow->mp_capable;
 934         }
 935
 936         if (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) ||
 937             ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) && !mp_opt->echo)) {
 938                 /* subflows are fully established as soon as we get any
 939                  * additional ack, including ADD_ADDR.
 940                  */
 941                 subflow->fully_established = 1;
 942                 WRITE_ONCE(msk->fully_established, true);
 943                 goto fully_established;
 944         }
 945
 946         /* If the first established packet does not contain MP_CAPABLE + data
 947          * then fallback to TCP. Fallback scenarios requires a reset for
 948          * MP_JOIN subflows.
 949          */
 950         if (!(mp_opt->suboptions & OPTIONS_MPTCP_MPC)) {
 951                 if (subflow->mp_join)
 952                         goto reset;
 953                 subflow->mp_capable = 0;
 954                 pr_fallback(msk);
 955                 __mptcp_do_fallback(msk);
 956                 return false;
 957         }
 958
 959         if (mp_opt->deny_join_id0)
 960                 WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 961
 962         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 963                 pr_warn_once("bogus mpc option on established client sk");
 964         mptcp_subflow_fully_established(subflow, mp_opt);
 965
 966 fully_established:
 967         /* if the subflow is not already linked into the conn_list, we can't
 968          * notify the PM: this subflow is still on the listener queue
 969          * and the PM possibly acquiring the subflow lock could race with
 970          * the listener close
 971          */
 972         if (likely(subflow->pm_notified) || list_empty(&subflow->node))
 973                 return true;
 974
 975         subflow->pm_notified = 1;
 976         if (subflow->mp_join) {
 977                 clear_3rdack_retransmission(ssk);
 978                 mptcp_pm_subflow_established(msk);
 979         } else {
 980                 mptcp_pm_fully_established(msk, ssk, GFP_ATOMIC);
 981         }
 982         return true;
 983
 984 reset:
 985         mptcp_subflow_reset(ssk);
 986         return false;
 987 }
 988
 989 u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
 990 {
 991         u32 old_seq32, cur_seq32;
 992
 993         old_seq32 = (u32)old_seq;
 994         cur_seq32 = (u32)cur_seq;
 995         cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
 996         if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
 997                 return cur_seq + (1LL << 32);
 998
 999         /* reverse wrap could happen, too */
1000         if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
1001                 return cur_seq - (1LL << 32);
1002         return cur_seq;
1003 }
1004
1005 static void ack_update_msk(struct mptcp_sock *msk,
1006                            struct sock *ssk,
1007                            struct mptcp_options_received *mp_opt)
1008 {
1009         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
1010         struct sock *sk = (struct sock *)msk;
1011         u64 old_snd_una;
1012
1013         mptcp_data_lock(sk);
1014
1015         /* avoid ack expansion on update conflict, to reduce the risk of
1016          * wrongly expanding to a future ack sequence number, which is way
1017          * more dangerous than missing an ack
1018          */
1019         old_snd_una = msk->snd_una;
1020         new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
1021
1022         /* ACK for data not even sent yet and even above recovery bound? Ignore.*/
1023         if (unlikely(after64(new_snd_una, snd_nxt))) {
1024                 if (!msk->recovery || after64(new_snd_una, msk->recovery_snd_nxt))
1025                         new_snd_una = old_snd_una;
1026         }
1027
1028         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
1029
1030         if (after64(new_wnd_end, msk->wnd_end))
1031                 msk->wnd_end = new_wnd_end;
1032
1033         /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
1034         if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
1035                 __mptcp_check_push(sk, ssk);
1036
1037         if (after64(new_snd_una, old_snd_una)) {
1038                 msk->snd_una = new_snd_una;
1039                 __mptcp_data_acked(sk);
1040         }
1041         mptcp_data_unlock(sk);
1042
1043         trace_ack_update_msk(mp_opt->data_ack,
1044                              old_snd_una, new_snd_una,
1045                              new_wnd_end, msk->wnd_end);
1046 }
1047
1048 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
1049 {
1050         /* Skip if DATA_FIN was already received.
1051          * If updating simultaneously with the recvmsg loop, values
1052          * should match. If they mismatch, the peer is misbehaving and
1053          * we will prefer the most recent information.
1054          */
1055         if (READ_ONCE(msk->rcv_data_fin))
1056                 return false;
1057
1058         WRITE_ONCE(msk->rcv_data_fin_seq,
1059                    mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1060         WRITE_ONCE(msk->rcv_data_fin, 1);
1061
1062         return true;
1063 }
1064
1065 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1066                                 struct mptcp_options_received *mp_opt)
1067 {
1068         u64 hmac = 0;
1069
1070         if (mp_opt->echo)
1071                 return true;
1072
1073         hmac = add_addr_generate_hmac(msk->remote_key,
1074                                       msk->local_key,
1075                                       &mp_opt->addr);
1076
1077         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1078                  msk, (unsigned long long)hmac,
1079                  (unsigned long long)mp_opt->ahmac);
1080
1081         return hmac == mp_opt->ahmac;
1082 }
1083
1084 /* Return false if a subflow has been reset, else return true */
1085 bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1086 {
1087         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1088         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1089         struct mptcp_options_received mp_opt;
1090         struct mptcp_ext *mpext;
1091
1092         if (__mptcp_check_fallback(msk)) {
1093                 /* Keep it simple and unconditionally trigger send data cleanup and
1094                  * pending queue spooling. We will need to acquire the data lock
1095                  * for more accurate checks, and once the lock is acquired, such
1096                  * helpers are cheap.
1097                  */
1098                 mptcp_data_lock(subflow->conn);
1099                 if (sk_stream_memory_free(sk))
1100                         __mptcp_check_push(subflow->conn, sk);
1101                 __mptcp_data_acked(subflow->conn);
1102                 mptcp_data_unlock(subflow->conn);
1103                 return true;
1104         }
1105
1106         mptcp_get_options(sk, skb, &mp_opt);
1107
1108         /* The subflow can be in close state only if check_fully_established()
1109          * just sent a reset. If so, tell the caller to ignore the current packet.
1110          */
1111         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1112                 return sk->sk_state != TCP_CLOSE;
1113
1114         if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
1115                 if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
1116                     msk->local_key == mp_opt.rcvr_key) {
1117                         WRITE_ONCE(msk->rcv_fastclose, true);
1118                         mptcp_schedule_work((struct sock *)msk);
1119                 }
1120
1121                 if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
1122                     add_addr_hmac_valid(msk, &mp_opt)) {
1123                         if (!mp_opt.echo) {
1124                                 mptcp_pm_add_addr_received(msk, &mp_opt.addr);
1125                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1126                         } else {
1127                                 mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1128                                 mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1129                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1130                         }
1131
1132                         if (mp_opt.addr.port)
1133                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1134                 }
1135
1136                 if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR)
1137                         mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1138
1139                 if (mp_opt.suboptions & OPTION_MPTCP_PRIO) {
1140                         mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1141                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1142                 }
1143
1144                 if (mp_opt.suboptions & OPTION_MPTCP_FAIL) {
1145                         mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq);
1146                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX);
1147                 }
1148
1149                 if (mp_opt.suboptions & OPTION_MPTCP_RST) {
1150                         subflow->reset_seen = 1;
1151                         subflow->reset_reason = mp_opt.reset_reason;
1152                         subflow->reset_transient = mp_opt.reset_transient;
1153                 }
1154
1155                 if (!(mp_opt.suboptions & OPTION_MPTCP_DSS))
1156                         return true;
1157         }
1158
1159         /* we can't wait for recvmsg() to update the ack_seq, otherwise
1160          * monodirectional flows will stuck
1161          */
1162         if (mp_opt.use_ack)
1163                 ack_update_msk(msk, sk, &mp_opt);
1164
1165         /* Zero-data-length packets are dropped by the caller and not
1166          * propagated to the MPTCP layer, so the skb extension does not
1167          * need to be allocated or populated. DATA_FIN information, if
1168          * present, needs to be updated here before the skb is freed.
1169          */
1170         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1171                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1172                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
1173                     schedule_work(&msk->work))
1174                         sock_hold(subflow->conn);
1175
1176                 return true;
1177         }
1178
1179         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1180         if (!mpext)
1181                 return true;
1182
1183         memset(mpext, 0, sizeof(*mpext));
1184
1185         if (likely(mp_opt.use_map)) {
1186                 if (mp_opt.mpc_map) {
1187                         /* this is an MP_CAPABLE carrying MPTCP data
1188                          * we know this map the first chunk of data
1189                          */
1190                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1191                                              &mpext->data_seq);
1192                         mpext->data_seq++;
1193                         mpext->subflow_seq = 1;
1194                         mpext->dsn64 = 1;
1195                         mpext->mpc_map = 1;
1196                         mpext->data_fin = 0;
1197                 } else {
1198                         mpext->data_seq = mp_opt.data_seq;
1199                         mpext->subflow_seq = mp_opt.subflow_seq;
1200                         mpext->dsn64 = mp_opt.dsn64;
1201                         mpext->data_fin = mp_opt.data_fin;
1202                 }
1203                 mpext->data_len = mp_opt.data_len;
1204                 mpext->use_map = 1;
1205                 mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD);
1206
1207                 if (mpext->csum_reqd)
1208                         mpext->csum = mp_opt.csum;
1209         }
1210
1211         return true;
1212 }
1213
1214 static void mptcp_set_rwin(const struct tcp_sock *tp)
1215 {
1216         const struct sock *ssk = (const struct sock *)tp;
1217         const struct mptcp_subflow_context *subflow;
1218         struct mptcp_sock *msk;
1219         u64 ack_seq;
1220
1221         subflow = mptcp_subflow_ctx(ssk);
1222         msk = mptcp_sk(subflow->conn);
1223
1224         ack_seq = READ_ONCE(msk->ack_seq) + tp->rcv_wnd;
1225
1226         if (after64(ack_seq, READ_ONCE(msk->rcv_wnd_sent)))
1227                 WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
1228 }
1229
1230 static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
1231 {
1232         struct csum_pseudo_header header;
1233         __wsum csum;
1234
1235         /* cfr RFC 8684 3.3.1.:
1236          * the data sequence number used in the pseudo-header is
1237          * always the 64-bit value, irrespective of what length is used in the
1238          * DSS option itself.
1239          */
1240         header.data_seq = cpu_to_be64(mpext->data_seq);
1241         header.subflow_seq = htonl(mpext->subflow_seq);
1242         header.data_len = htons(mpext->data_len);
1243         header.csum = 0;
1244
1245         csum = csum_partial(&header, sizeof(header), ~csum_unfold(mpext->csum));
1246         return (__force u16)csum_fold(csum);
1247 }
1248
1249 void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
1250                          struct mptcp_out_options *opts)
1251 {
1252         if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) {
1253                 const struct sock *ssk = (const struct sock *)tp;
1254                 struct mptcp_subflow_context *subflow;
1255
1256                 subflow = mptcp_subflow_ctx(ssk);
1257                 subflow->send_mp_fail = 0;
1258
1259                 *ptr++ = mptcp_option(MPTCPOPT_MP_FAIL,
1260                                       TCPOLEN_MPTCP_FAIL,
1261                                       0, 0);
1262                 put_unaligned_be64(opts->fail_seq, ptr);
1263                 ptr += 2;
1264         }
1265
1266         /* RST is mutually exclusive with everything else */
1267         if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
1268                 *ptr++ = mptcp_option(MPTCPOPT_RST,
1269                                       TCPOLEN_MPTCP_RST,
1270                                       opts->reset_transient,
1271                                       opts->reset_reason);
1272                 return;
1273         }
1274
1275         /* DSS, MPC, MPJ and ADD_ADDR are mutually exclusive, see
1276          * mptcp_established_options*()
1277          */
1278         if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
1279                 struct mptcp_ext *mpext = &opts->ext_copy;
1280                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1281                 u8 flags = 0;
1282
1283                 if (mpext->use_ack) {
1284                         flags = MPTCP_DSS_HAS_ACK;
1285                         if (mpext->ack64) {
1286                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1287                                 flags |= MPTCP_DSS_ACK64;
1288                         } else {
1289                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1290                         }
1291                 }
1292
1293                 if (mpext->use_map) {
1294                         len += TCPOLEN_MPTCP_DSS_MAP64;
1295
1296                         /* Use only 64-bit mapping flags for now, add
1297                          * support for optional 32-bit mappings later.
1298                          */
1299                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1300                         if (mpext->data_fin)
1301                                 flags |= MPTCP_DSS_DATA_FIN;
1302
1303                         if (opts->csum_reqd)
1304                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1305                 }
1306
1307                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1308
1309                 if (mpext->use_ack) {
1310                         if (mpext->ack64) {
1311                                 put_unaligned_be64(mpext->data_ack, ptr);
1312                                 ptr += 2;
1313                         } else {
1314                                 put_unaligned_be32(mpext->data_ack32, ptr);
1315                                 ptr += 1;
1316                         }
1317                 }
1318
1319                 if (mpext->use_map) {
1320                         put_unaligned_be64(mpext->data_seq, ptr);
1321                         ptr += 2;
1322                         put_unaligned_be32(mpext->subflow_seq, ptr);
1323                         ptr += 1;
1324                         if (opts->csum_reqd) {
1325                                 put_unaligned_be32(mpext->data_len << 16 |
1326                                                    mptcp_make_csum(mpext), ptr);
1327                         } else {
1328                                 put_unaligned_be32(mpext->data_len << 16 |
1329                                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1330                         }
1331                 }
1332         } else if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
1333                     OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
1334                 u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1335
1336                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1337                         len = TCPOLEN_MPTCP_MPC_SYN;
1338                 } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1339                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1340                 } else if (opts->ext_copy.data_len) {
1341                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1342                         if (opts->csum_reqd)
1343                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1344                 } else {
1345                         len = TCPOLEN_MPTCP_MPC_ACK;
1346                 }
1347
1348                 if (opts->csum_reqd)
1349                         flag |= MPTCP_CAP_CHECKSUM_REQD;
1350
1351                 if (!opts->allow_join_id0)
1352                         flag |= MPTCP_CAP_DENY_JOIN_ID0;
1353
1354                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1355                                       MPTCP_SUPPORTED_VERSION,
1356                                       flag);
1357
1358                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1359                     opts->suboptions))
1360                         goto mp_capable_done;
1361
1362                 put_unaligned_be64(opts->sndr_key, ptr);
1363                 ptr += 2;
1364                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1365                         goto mp_capable_done;
1366
1367                 put_unaligned_be64(opts->rcvr_key, ptr);
1368                 ptr += 2;
1369                 if (!opts->ext_copy.data_len)
1370                         goto mp_capable_done;
1371
1372                 if (opts->csum_reqd) {
1373                         put_unaligned_be32(opts->ext_copy.data_len << 16 |
1374                                            mptcp_make_csum(&opts->ext_copy), ptr);
1375                 } else {
1376                         put_unaligned_be32(opts->ext_copy.data_len << 16 |
1377                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1378                 }
1379                 ptr += 1;
1380
1381                 /* MPC is additionally mutually exclusive with MP_PRIO */
1382                 goto mp_capable_done;
1383         } else if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1384                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1385                                       TCPOLEN_MPTCP_MPJ_SYN,
1386                                       opts->backup, opts->join_id);
1387                 put_unaligned_be32(opts->token, ptr);
1388                 ptr += 1;
1389                 put_unaligned_be32(opts->nonce, ptr);
1390                 ptr += 1;
1391         } else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1392                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1393                                       TCPOLEN_MPTCP_MPJ_SYNACK,
1394                                       opts->backup, opts->join_id);
1395                 put_unaligned_be64(opts->thmac, ptr);
1396                 ptr += 2;
1397                 put_unaligned_be32(opts->nonce, ptr);
1398                 ptr += 1;
1399         } else if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
1400                 *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1401                                       TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1402                 memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1403                 ptr += 5;
1404         } else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1405                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1406                 u8 echo = MPTCP_ADDR_ECHO;
1407
1408 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1409                 if (opts->addr.family == AF_INET6)
1410                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1411 #endif
1412
1413                 if (opts->addr.port)
1414                         len += TCPOLEN_MPTCP_PORT_LEN;
1415
1416                 if (opts->ahmac) {
1417                         len += sizeof(opts->ahmac);
1418                         echo = 0;
1419                 }
1420
1421                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1422                                       len, echo, opts->addr.id);
1423                 if (opts->addr.family == AF_INET) {
1424                         memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1425                         ptr += 1;
1426                 }
1427 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1428                 else if (opts->addr.family == AF_INET6) {
1429                         memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1430                         ptr += 4;
1431                 }
1432 #endif
1433
1434                 if (!opts->addr.port) {
1435                         if (opts->ahmac) {
1436                                 put_unaligned_be64(opts->ahmac, ptr);
1437                                 ptr += 2;
1438                         }
1439                 } else {
1440                         u16 port = ntohs(opts->addr.port);
1441
1442                         if (opts->ahmac) {
1443                                 u8 *bptr = (u8 *)ptr;
1444
1445                                 put_unaligned_be16(port, bptr);
1446                                 bptr += 2;
1447                                 put_unaligned_be64(opts->ahmac, bptr);
1448                                 bptr += 8;
1449                                 put_unaligned_be16(TCPOPT_NOP << 8 |
1450                                                    TCPOPT_NOP, bptr);
1451
1452                                 ptr += 3;
1453                         } else {
1454                                 put_unaligned_be32(port << 16 |
1455                                                    TCPOPT_NOP << 8 |
1456                                                    TCPOPT_NOP, ptr);
1457                                 ptr += 1;
1458                         }
1459                 }
1460         }
1461
1462         if (OPTION_MPTCP_PRIO & opts->suboptions) {
1463                 const struct sock *ssk = (const struct sock *)tp;
1464                 struct mptcp_subflow_context *subflow;
1465
1466                 subflow = mptcp_subflow_ctx(ssk);
1467                 subflow->send_mp_prio = 0;
1468
1469                 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1470                                       TCPOLEN_MPTCP_PRIO,
1471                                       opts->backup, TCPOPT_NOP);
1472         }
1473
1474 mp_capable_done:
1475         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1476                 u8 i = 1;
1477
1478                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1479                                       TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1480                                       0, opts->rm_list.ids[0]);
1481
1482                 while (i < opts->rm_list.nr) {
1483                         u8 id1, id2, id3, id4;
1484
1485                         id1 = opts->rm_list.ids[i];
1486                         id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1487                         id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1488                         id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1489                         put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1490                         ptr += 1;
1491                         i += 4;
1492                 }
1493         }
1494
1495         if (tp)
1496                 mptcp_set_rwin(tp);
1497 }
1498
1499 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1500 {
1501         const struct mptcp_ext *ext = mptcp_get_ext(skb);
1502         u8 flags, reason;
1503
1504         if (ext) {
1505                 flags = ext->reset_transient;
1506                 reason = ext->reset_reason;
1507
1508                 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1509                                     flags, reason);
1510         }
1511
1512         return htonl(0u);
1513 }
1514 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);