linux/net/mptcp/options.c
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   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
  18static bool mptcp_cap_flag_sha256(u8 flags)
  19{
  20        return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
  21}
  22
  23static void mptcp_parse_option(const struct sk_buff *skb,
  24                               const unsigned char *ptr, int opsize,
  25                               struct mptcp_options_received *mp_opt)
  26{
  27        u8 subtype = *ptr >> 4;
  28        int expected_opsize;
  29        u8 version;
  30        u8 flags;
  31        u8 i;
  32
  33        switch (subtype) {
  34        case MPTCPOPT_MP_CAPABLE:
  35                /* strict size checking */
  36                if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
  37                        if (skb->len > tcp_hdr(skb)->doff << 2)
  38                                expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
  39                        else
  40                                expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
  41                } else {
  42                        if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)
  43                                expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
  44                        else
  45                                expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
  46                }
  47
  48                /* Cfr RFC 8684 Section 3.3.0:
  49                 * If a checksum is present but its use had
  50                 * not been negotiated in the MP_CAPABLE handshake, the receiver MUST
  51                 * close the subflow with a RST, as it is not behaving as negotiated.
  52                 * If a checksum is not present when its use has been negotiated, the
  53                 * receiver MUST close the subflow with a RST, as it is considered
  54                 * broken
  55                 * We parse even option with mismatching csum presence, so that
  56                 * later in subflow_data_ready we can trigger the reset.
  57                 */
  58                if (opsize != expected_opsize &&
  59                    (expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA ||
  60                     opsize != TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM))
  61                        break;
  62
  63                /* try to be gentle vs future versions on the initial syn */
  64                version = *ptr++ & MPTCP_VERSION_MASK;
  65                if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
  66                        if (version != MPTCP_SUPPORTED_VERSION)
  67                                break;
  68                } else if (version < MPTCP_SUPPORTED_VERSION) {
  69                        break;
  70                }
  71
  72                flags = *ptr++;
  73                if (!mptcp_cap_flag_sha256(flags) ||
  74                    (flags & MPTCP_CAP_EXTENSIBILITY))
  75                        break;
  76
  77                /* RFC 6824, Section 3.1:
  78                 * "For the Checksum Required bit (labeled "A"), if either
  79                 * host requires the use of checksums, checksums MUST be used.
  80                 * In other words, the only way for checksums not to be used
  81                 * is if both hosts in their SYNs set A=0."
  82                 */
  83                if (flags & MPTCP_CAP_CHECKSUM_REQD)
  84                        mp_opt->csum_reqd = 1;
  85
  86                if (flags & MPTCP_CAP_DENY_JOIN_ID0)
  87                        mp_opt->deny_join_id0 = 1;
  88
  89                mp_opt->mp_capable = 1;
  90                if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
  91                        mp_opt->sndr_key = get_unaligned_be64(ptr);
  92                        ptr += 8;
  93                }
  94                if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
  95                        mp_opt->rcvr_key = get_unaligned_be64(ptr);
  96                        ptr += 8;
  97                }
  98                if (opsize >= TCPOLEN_MPTCP_MPC_ACK_DATA) {
  99                        /* Section 3.1.:
 100                         * "the data parameters in a MP_CAPABLE are semantically
 101                         * equivalent to those in a DSS option and can be used
 102                         * interchangeably."
 103                         */
 104                        mp_opt->dss = 1;
 105                        mp_opt->use_map = 1;
 106                        mp_opt->mpc_map = 1;
 107                        mp_opt->data_len = get_unaligned_be16(ptr);
 108                        ptr += 2;
 109                }
 110                if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
 111                        mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
 112                        mp_opt->csum_reqd = 1;
 113                        ptr += 2;
 114                }
 115                pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u",
 116                         version, flags, opsize, mp_opt->sndr_key,
 117                         mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum);
 118                break;
 119
 120        case MPTCPOPT_MP_JOIN:
 121                mp_opt->mp_join = 1;
 122                if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 123                        mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 124                        mp_opt->join_id = *ptr++;
 125                        mp_opt->token = get_unaligned_be32(ptr);
 126                        ptr += 4;
 127                        mp_opt->nonce = get_unaligned_be32(ptr);
 128                        ptr += 4;
 129                        pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
 130                                 mp_opt->backup, mp_opt->join_id,
 131                                 mp_opt->token, mp_opt->nonce);
 132                } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
 133                        mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 134                        mp_opt->join_id = *ptr++;
 135                        mp_opt->thmac = get_unaligned_be64(ptr);
 136                        ptr += 8;
 137                        mp_opt->nonce = get_unaligned_be32(ptr);
 138                        ptr += 4;
 139                        pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
 140                                 mp_opt->backup, mp_opt->join_id,
 141                                 mp_opt->thmac, mp_opt->nonce);
 142                } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 143                        ptr += 2;
 144                        memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 145                        pr_debug("MP_JOIN hmac");
 146                } else {
 147                        mp_opt->mp_join = 0;
 148                }
 149                break;
 150
 151        case MPTCPOPT_DSS:
 152                pr_debug("DSS");
 153                ptr++;
 154
 155                /* we must clear 'mpc_map' be able to detect MP_CAPABLE
 156                 * map vs DSS map in mptcp_incoming_options(), and reconstruct
 157                 * map info accordingly
 158                 */
 159                mp_opt->mpc_map = 0;
 160                flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 161                mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 162                mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 163                mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 164                mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 165                mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 166
 167                pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
 168                         mp_opt->data_fin, mp_opt->dsn64,
 169                         mp_opt->use_map, mp_opt->ack64,
 170                         mp_opt->use_ack);
 171
 172                expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 173
 174                if (mp_opt->use_ack) {
 175                        if (mp_opt->ack64)
 176                                expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 177                        else
 178                                expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 179                }
 180
 181                if (mp_opt->use_map) {
 182                        if (mp_opt->dsn64)
 183                                expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 184                        else
 185                                expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 186                }
 187
 188                /* Always parse any csum presence combination, we will enforce
 189                 * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
 190                 */
 191                if (opsize != expected_opsize &&
 192                    opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 193                        break;
 194
 195                mp_opt->dss = 1;
 196
 197                if (mp_opt->use_ack) {
 198                        if (mp_opt->ack64) {
 199                                mp_opt->data_ack = get_unaligned_be64(ptr);
 200                                ptr += 8;
 201                        } else {
 202                                mp_opt->data_ack = get_unaligned_be32(ptr);
 203                                ptr += 4;
 204                        }
 205
 206                        pr_debug("data_ack=%llu", mp_opt->data_ack);
 207                }
 208
 209                if (mp_opt->use_map) {
 210                        if (mp_opt->dsn64) {
 211                                mp_opt->data_seq = get_unaligned_be64(ptr);
 212                                ptr += 8;
 213                        } else {
 214                                mp_opt->data_seq = get_unaligned_be32(ptr);
 215                                ptr += 4;
 216                        }
 217
 218                        mp_opt->subflow_seq = get_unaligned_be32(ptr);
 219                        ptr += 4;
 220
 221                        mp_opt->data_len = get_unaligned_be16(ptr);
 222                        ptr += 2;
 223
 224                        if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
 225                                mp_opt->csum_reqd = 1;
 226                                mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
 227                                ptr += 2;
 228                        }
 229
 230                        pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u",
 231                                 mp_opt->data_seq, mp_opt->subflow_seq,
 232                                 mp_opt->data_len, mp_opt->csum_reqd, mp_opt->csum);
 233                }
 234
 235                break;
 236
 237        case MPTCPOPT_ADD_ADDR:
 238                mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 239                if (!mp_opt->echo) {
 240                        if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 241                            opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 242                                mp_opt->addr.family = AF_INET;
 243#if IS_ENABLED(CONFIG_MPTCP_IPV6)
 244                        else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 245                                 opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 246                                mp_opt->addr.family = AF_INET6;
 247#endif
 248                        else
 249                                break;
 250                } else {
 251                        if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 252                            opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 253                                mp_opt->addr.family = AF_INET;
 254#if IS_ENABLED(CONFIG_MPTCP_IPV6)
 255                        else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 256                                 opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 257                                mp_opt->addr.family = AF_INET6;
 258#endif
 259                        else
 260                                break;
 261                }
 262
 263                mp_opt->add_addr = 1;
 264                mp_opt->addr.id = *ptr++;
 265                if (mp_opt->addr.family == AF_INET) {
 266                        memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
 267                        ptr += 4;
 268                        if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 269                            opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 270                                mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 271                                ptr += 2;
 272                        }
 273                }
 274#if IS_ENABLED(CONFIG_MPTCP_IPV6)
 275                else {
 276                        memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16);
 277                        ptr += 16;
 278                        if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 279                            opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 280                                mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 281                                ptr += 2;
 282                        }
 283                }
 284#endif
 285                if (!mp_opt->echo) {
 286                        mp_opt->ahmac = get_unaligned_be64(ptr);
 287                        ptr += 8;
 288                }
 289                pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d",
 290                         (mp_opt->addr.family == AF_INET6) ? "6" : "",
 291                         mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
 292                break;
 293
 294        case MPTCPOPT_RM_ADDR:
 295                if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
 296                    opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
 297                        break;
 298
 299                ptr++;
 300
 301                mp_opt->rm_addr = 1;
 302                mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
 303                for (i = 0; i < mp_opt->rm_list.nr; i++)
 304                        mp_opt->rm_list.ids[i] = *ptr++;
 305                pr_debug("RM_ADDR: rm_list_nr=%d", mp_opt->rm_list.nr);
 306                break;
 307
 308        case MPTCPOPT_MP_PRIO:
 309                if (opsize != TCPOLEN_MPTCP_PRIO)
 310                        break;
 311
 312                mp_opt->mp_prio = 1;
 313                mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
 314                pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
 315                break;
 316
 317        case MPTCPOPT_MP_FASTCLOSE:
 318                if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 319                        break;
 320
 321                ptr += 2;
 322                mp_opt->rcvr_key = get_unaligned_be64(ptr);
 323                ptr += 8;
 324                mp_opt->fastclose = 1;
 325                break;
 326
 327        case MPTCPOPT_RST:
 328                if (opsize != TCPOLEN_MPTCP_RST)
 329                        break;
 330
 331                if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 332                        break;
 333                mp_opt->reset = 1;
 334                flags = *ptr++;
 335                mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
 336                mp_opt->reset_reason = *ptr;
 337                break;
 338
 339        default:
 340                break;
 341        }
 342}
 343
 344void mptcp_get_options(const struct sock *sk,
 345                       const struct sk_buff *skb,
 346                       struct mptcp_options_received *mp_opt)
 347{
 348        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 349        struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 350        const struct tcphdr *th = tcp_hdr(skb);
 351        const unsigned char *ptr;
 352        int length;
 353
 354        /* initialize option status */
 355        mp_opt->mp_capable = 0;
 356        mp_opt->mp_join = 0;
 357        mp_opt->add_addr = 0;
 358        mp_opt->ahmac = 0;
 359        mp_opt->fastclose = 0;
 360        mp_opt->addr.port = 0;
 361        mp_opt->rm_addr = 0;
 362        mp_opt->dss = 0;
 363        mp_opt->mp_prio = 0;
 364        mp_opt->reset = 0;
 365        mp_opt->csum_reqd = READ_ONCE(msk->csum_enabled);
 366        mp_opt->deny_join_id0 = 0;
 367
 368        length = (th->doff * 4) - sizeof(struct tcphdr);
 369        ptr = (const unsigned char *)(th + 1);
 370
 371        while (length > 0) {
 372                int opcode = *ptr++;
 373                int opsize;
 374
 375                switch (opcode) {
 376                case TCPOPT_EOL:
 377                        return;
 378                case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 379                        length--;
 380                        continue;
 381                default:
 382                        if (length < 2)
 383                                return;
 384                        opsize = *ptr++;
 385                        if (opsize < 2) /* "silly options" */
 386                                return;
 387                        if (opsize > length)
 388                                return; /* don't parse partial options */
 389                        if (opcode == TCPOPT_MPTCP)
 390                                mptcp_parse_option(skb, ptr, opsize, mp_opt);
 391                        ptr += opsize - 2;
 392                        length -= opsize;
 393                }
 394        }
 395}
 396
 397bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 398                       unsigned int *size, struct mptcp_out_options *opts)
 399{
 400        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 401
 402        /* we will use snd_isn to detect first pkt [re]transmission
 403         * in mptcp_established_options_mp()
 404         */
 405        subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 406        if (subflow->request_mptcp) {
 407                opts->suboptions = OPTION_MPTCP_MPC_SYN;
 408                opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
 409                opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 410                *size = TCPOLEN_MPTCP_MPC_SYN;
 411                return true;
 412        } else if (subflow->request_join) {
 413                pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 414                         subflow->local_nonce);
 415                opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 416                opts->join_id = subflow->local_id;
 417                opts->token = subflow->remote_token;
 418                opts->nonce = subflow->local_nonce;
 419                opts->backup = subflow->request_bkup;
 420                *size = TCPOLEN_MPTCP_MPJ_SYN;
 421                return true;
 422        }
 423        return false;
 424}
 425
 426/* MP_JOIN client subflow must wait for 4th ack before sending any data:
 427 * TCP can't schedule delack timer before the subflow is fully established.
 428 * MPTCP uses the delack timer to do 3rd ack retransmissions
 429 */
 430static void schedule_3rdack_retransmission(struct sock *sk)
 431{
 432        struct inet_connection_sock *icsk = inet_csk(sk);
 433        struct tcp_sock *tp = tcp_sk(sk);
 434        unsigned long timeout;
 435
 436        /* reschedule with a timeout above RTT, as we must look only for drop */
 437        if (tp->srtt_us)
 438                timeout = tp->srtt_us << 1;
 439        else
 440                timeout = TCP_TIMEOUT_INIT;
 441
 442        WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 443        icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 444        icsk->icsk_ack.timeout = timeout;
 445        sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 446}
 447
 448static void clear_3rdack_retransmission(struct sock *sk)
 449{
 450        struct inet_connection_sock *icsk = inet_csk(sk);
 451
 452        sk_stop_timer(sk, &icsk->icsk_delack_timer);
 453        icsk->icsk_ack.timeout = 0;
 454        icsk->icsk_ack.ato = 0;
 455        icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 456}
 457
 458static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 459                                         bool snd_data_fin_enable,
 460                                         unsigned int *size,
 461                                         unsigned int remaining,
 462                                         struct mptcp_out_options *opts)
 463{
 464        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 465        struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 466        struct mptcp_ext *mpext;
 467        unsigned int data_len;
 468        u8 len;
 469
 470        /* When skb is not available, we better over-estimate the emitted
 471         * options len. A full DSS option (28 bytes) is longer than
 472         * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 473         * tell the caller to defer the estimate to
 474         * mptcp_established_options_dss(), which will reserve enough space.
 475         */
 476        if (!skb)
 477                return false;
 478
 479        /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
 480        if (subflow->fully_established || snd_data_fin_enable ||
 481            subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 482            sk->sk_state != TCP_ESTABLISHED)
 483                return false;
 484
 485        if (subflow->mp_capable) {
 486                mpext = mptcp_get_ext(skb);
 487                data_len = mpext ? mpext->data_len : 0;
 488
 489                /* we will check ext_copy.data_len in mptcp_write_options() to
 490                 * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 491                 * TCPOLEN_MPTCP_MPC_ACK
 492                 */
 493                opts->ext_copy.data_len = data_len;
 494                opts->suboptions = OPTION_MPTCP_MPC_ACK;
 495                opts->sndr_key = subflow->local_key;
 496                opts->rcvr_key = subflow->remote_key;
 497                opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 498                opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 499
 500                /* Section 3.1.
 501                 * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 502                 * packets that start the first subflow of an MPTCP connection,
 503                 * as well as the first packet that carries data
 504                 */
 505                if (data_len > 0) {
 506                        len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 507                        if (opts->csum_reqd) {
 508                                /* we need to propagate more info to csum the pseudo hdr */
 509                                opts->ext_copy.data_seq = mpext->data_seq;
 510                                opts->ext_copy.subflow_seq = mpext->subflow_seq;
 511                                opts->ext_copy.csum = mpext->csum;
 512                                len += TCPOLEN_MPTCP_DSS_CHECKSUM;
 513                        }
 514                        *size = ALIGN(len, 4);
 515                } else {
 516                        *size = TCPOLEN_MPTCP_MPC_ACK;
 517                }
 518
 519                pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 520                         subflow, subflow->local_key, subflow->remote_key,
 521                         data_len);
 522
 523                return true;
 524        } else if (subflow->mp_join) {
 525                opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 526                memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 527                *size = TCPOLEN_MPTCP_MPJ_ACK;
 528                pr_debug("subflow=%p", subflow);
 529
 530                schedule_3rdack_retransmission(sk);
 531                return true;
 532        }
 533        return false;
 534}
 535
 536static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 537                                 struct sk_buff *skb, struct mptcp_ext *ext)
 538{
 539        /* The write_seq value has already been incremented, so the actual
 540         * sequence number for the DATA_FIN is one less.
 541         */
 542        u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 543
 544        if (!ext->use_map || !skb->len) {
 545                /* RFC6824 requires a DSS mapping with specific values
 546                 * if DATA_FIN is set but no data payload is mapped
 547                 */
 548                ext->data_fin = 1;
 549                ext->use_map = 1;
 550                ext->dsn64 = 1;
 551                ext->data_seq = data_fin_tx_seq;
 552                ext->subflow_seq = 0;
 553                ext->data_len = 1;
 554        } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 555                /* If there's an existing DSS mapping and it is the
 556                 * final mapping, DATA_FIN consumes 1 additional byte of
 557                 * mapping space.
 558                 */
 559                ext->data_fin = 1;
 560                ext->data_len++;
 561        }
 562}
 563
 564static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 565                                          bool snd_data_fin_enable,
 566                                          unsigned int *size,
 567                                          unsigned int remaining,
 568                                          struct mptcp_out_options *opts)
 569{
 570        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 571        struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 572        unsigned int dss_size = 0;
 573        struct mptcp_ext *mpext;
 574        unsigned int ack_size;
 575        bool ret = false;
 576        u64 ack_seq;
 577
 578        opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 579        mpext = skb ? mptcp_get_ext(skb) : NULL;
 580
 581        if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 582                unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 583
 584                if (mpext) {
 585                        if (opts->csum_reqd)
 586                                map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
 587
 588                        opts->ext_copy = *mpext;
 589                }
 590
 591                remaining -= map_size;
 592                dss_size = map_size;
 593                if (skb && snd_data_fin_enable)
 594                        mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 595                ret = true;
 596        }
 597
 598        /* passive sockets msk will set the 'can_ack' after accept(), even
 599         * if the first subflow may have the already the remote key handy
 600         */
 601        opts->ext_copy.use_ack = 0;
 602        if (!READ_ONCE(msk->can_ack)) {
 603                *size = ALIGN(dss_size, 4);
 604                return ret;
 605        }
 606
 607        ack_seq = READ_ONCE(msk->ack_seq);
 608        if (READ_ONCE(msk->use_64bit_ack)) {
 609                ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 610                opts->ext_copy.data_ack = ack_seq;
 611                opts->ext_copy.ack64 = 1;
 612        } else {
 613                ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 614                opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
 615                opts->ext_copy.ack64 = 0;
 616        }
 617        opts->ext_copy.use_ack = 1;
 618        WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 619
 620        /* Add kind/length/subtype/flag overhead if mapping is not populated */
 621        if (dss_size == 0)
 622                ack_size += TCPOLEN_MPTCP_DSS_BASE;
 623
 624        dss_size += ack_size;
 625
 626        *size = ALIGN(dss_size, 4);
 627        return true;
 628}
 629
 630static u64 add_addr_generate_hmac(u64 key1, u64 key2,
 631                                  struct mptcp_addr_info *addr)
 632{
 633        u16 port = ntohs(addr->port);
 634        u8 hmac[SHA256_DIGEST_SIZE];
 635        u8 msg[19];
 636        int i = 0;
 637
 638        msg[i++] = addr->id;
 639        if (addr->family == AF_INET) {
 640                memcpy(&msg[i], &addr->addr.s_addr, 4);
 641                i += 4;
 642        }
 643#if IS_ENABLED(CONFIG_MPTCP_IPV6)
 644        else if (addr->family == AF_INET6) {
 645                memcpy(&msg[i], &addr->addr6.s6_addr, 16);
 646                i += 16;
 647        }
 648#endif
 649        msg[i++] = port >> 8;
 650        msg[i++] = port & 0xFF;
 651
 652        mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
 653
 654        return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 655}
 656
 657static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 658                                               unsigned int *size,
 659                                               unsigned int remaining,
 660                                               struct mptcp_out_options *opts)
 661{
 662        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 663        struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 664        bool drop_other_suboptions = false;
 665        unsigned int opt_size = *size;
 666        bool echo;
 667        bool port;
 668        int len;
 669
 670        if ((mptcp_pm_should_add_signal_ipv6(msk) ||
 671             mptcp_pm_should_add_signal_port(msk) ||
 672             mptcp_pm_should_add_signal_echo(msk)) &&
 673            skb && skb_is_tcp_pure_ack(skb)) {
 674                pr_debug("drop other suboptions");
 675                opts->suboptions = 0;
 676                opts->ext_copy.use_ack = 0;
 677                opts->ext_copy.use_map = 0;
 678                remaining += opt_size;
 679                drop_other_suboptions = true;
 680        }
 681
 682        if (!mptcp_pm_should_add_signal(msk) ||
 683            !(mptcp_pm_add_addr_signal(msk, remaining, &opts->addr, &echo, &port)))
 684                return false;
 685
 686        len = mptcp_add_addr_len(opts->addr.family, echo, port);
 687        if (remaining < len)
 688                return false;
 689
 690        *size = len;
 691        if (drop_other_suboptions)
 692                *size -= opt_size;
 693        opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 694        if (!echo) {
 695                opts->ahmac = add_addr_generate_hmac(msk->local_key,
 696                                                     msk->remote_key,
 697                                                     &opts->addr);
 698        }
 699        pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d",
 700                 opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
 701
 702        return true;
 703}
 704
 705static bool mptcp_established_options_rm_addr(struct sock *sk,
 706                                              unsigned int *size,
 707                                              unsigned int remaining,
 708                                              struct mptcp_out_options *opts)
 709{
 710        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 711        struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 712        struct mptcp_rm_list rm_list;
 713        int i, len;
 714
 715        if (!mptcp_pm_should_rm_signal(msk) ||
 716            !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
 717                return false;
 718
 719        len = mptcp_rm_addr_len(&rm_list);
 720        if (len < 0)
 721                return false;
 722        if (remaining < len)
 723                return false;
 724
 725        *size = len;
 726        opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 727        opts->rm_list = rm_list;
 728
 729        for (i = 0; i < opts->rm_list.nr; i++)
 730                pr_debug("rm_list_ids[%d]=%d", i, opts->rm_list.ids[i]);
 731
 732        return true;
 733}
 734
 735static bool mptcp_established_options_mp_prio(struct sock *sk,
 736                                              unsigned int *size,
 737                                              unsigned int remaining,
 738                                              struct mptcp_out_options *opts)
 739{
 740        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 741
 742        if (!subflow->send_mp_prio)
 743                return false;
 744
 745        /* account for the trailing 'nop' option */
 746        if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
 747                return false;
 748
 749        *size = TCPOLEN_MPTCP_PRIO_ALIGN;
 750        opts->suboptions |= OPTION_MPTCP_PRIO;
 751        opts->backup = subflow->request_bkup;
 752
 753        pr_debug("prio=%d", opts->backup);
 754
 755        return true;
 756}
 757
 758static noinline void mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
 759                                                   unsigned int *size,
 760                                                   unsigned int remaining,
 761                                                   struct mptcp_out_options *opts)
 762{
 763        const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 764
 765        if (remaining < TCPOLEN_MPTCP_RST)
 766                return;
 767
 768        *size = TCPOLEN_MPTCP_RST;
 769        opts->suboptions |= OPTION_MPTCP_RST;
 770        opts->reset_transient = subflow->reset_transient;
 771        opts->reset_reason = subflow->reset_reason;
 772}
 773
 774bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 775                               unsigned int *size, unsigned int remaining,
 776                               struct mptcp_out_options *opts)
 777{
 778        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 779        struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 780        unsigned int opt_size = 0;
 781        bool snd_data_fin;
 782        bool ret = false;
 783
 784        opts->suboptions = 0;
 785
 786        if (unlikely(__mptcp_check_fallback(msk)))
 787                return false;
 788
 789        if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 790                mptcp_established_options_rst(sk, skb, size, remaining, opts);
 791                return true;
 792        }
 793
 794        snd_data_fin = mptcp_data_fin_enabled(msk);
 795        if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 796                ret = true;
 797        else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 798                ret = true;
 799
 800        /* we reserved enough space for the above options, and exceeding the
 801         * TCP option space would be fatal
 802         */
 803        if (WARN_ON_ONCE(opt_size > remaining))
 804                return false;
 805
 806        *size += opt_size;
 807        remaining -= opt_size;
 808        if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
 809                *size += opt_size;
 810                remaining -= opt_size;
 811                ret = true;
 812        } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 813                *size += opt_size;
 814                remaining -= opt_size;
 815                ret = true;
 816        }
 817
 818        if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
 819                *size += opt_size;
 820                remaining -= opt_size;
 821                ret = true;
 822        }
 823
 824        return ret;
 825}
 826
 827bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 828                          struct mptcp_out_options *opts)
 829{
 830        struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 831
 832        if (subflow_req->mp_capable) {
 833                opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 834                opts->sndr_key = subflow_req->local_key;
 835                opts->csum_reqd = subflow_req->csum_reqd;
 836                opts->allow_join_id0 = subflow_req->allow_join_id0;
 837                *size = TCPOLEN_MPTCP_MPC_SYNACK;
 838                pr_debug("subflow_req=%p, local_key=%llu",
 839                         subflow_req, subflow_req->local_key);
 840                return true;
 841        } else if (subflow_req->mp_join) {
 842                opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 843                opts->backup = subflow_req->backup;
 844                opts->join_id = subflow_req->local_id;
 845                opts->thmac = subflow_req->thmac;
 846                opts->nonce = subflow_req->local_nonce;
 847                pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 848                         subflow_req, opts->backup, opts->join_id,
 849                         opts->thmac, opts->nonce);
 850                *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 851                return true;
 852        }
 853        return false;
 854}
 855
 856static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 857                                    struct mptcp_subflow_context *subflow,
 858                                    struct sk_buff *skb,
 859                                    struct mptcp_options_received *mp_opt)
 860{
 861        /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 862         * will make the subflow fully established
 863         */
 864        if (likely(subflow->fully_established)) {
 865                /* on passive sockets, check for 3rd ack retransmission
 866                 * note that msk is always set by subflow_syn_recv_sock()
 867                 * for mp_join subflows
 868                 */
 869                if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 870                    TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 871                    subflow->mp_join && mp_opt->mp_join &&
 872                    READ_ONCE(msk->pm.server_side))
 873                        tcp_send_ack(ssk);
 874                goto fully_established;
 875        }
 876
 877        /* we must process OoO packets before the first subflow is fully
 878         * established. OoO packets are instead a protocol violation
 879         * for MP_JOIN subflows as the peer must not send any data
 880         * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 881         */
 882        if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 883                if (subflow->mp_join)
 884                        goto reset;
 885                return subflow->mp_capable;
 886        }
 887
 888        if ((mp_opt->dss && mp_opt->use_ack) ||
 889            (mp_opt->add_addr && !mp_opt->echo)) {
 890                /* subflows are fully established as soon as we get any
 891                 * additional ack, including ADD_ADDR.
 892                 */
 893                subflow->fully_established = 1;
 894                WRITE_ONCE(msk->fully_established, true);
 895                goto fully_established;
 896        }
 897
 898        /* If the first established packet does not contain MP_CAPABLE + data
 899         * then fallback to TCP. Fallback scenarios requires a reset for
 900         * MP_JOIN subflows.
 901         */
 902        if (!mp_opt->mp_capable) {
 903                if (subflow->mp_join)
 904                        goto reset;
 905                subflow->mp_capable = 0;
 906                pr_fallback(msk);
 907                __mptcp_do_fallback(msk);
 908                return false;
 909        }
 910
 911        if (mp_opt->deny_join_id0)
 912                WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 913
 914        if (unlikely(!READ_ONCE(msk->pm.server_side)))
 915                pr_warn_once("bogus mpc option on established client sk");
 916        mptcp_subflow_fully_established(subflow, mp_opt);
 917
 918fully_established:
 919        /* if the subflow is not already linked into the conn_list, we can't
 920         * notify the PM: this subflow is still on the listener queue
 921         * and the PM possibly acquiring the subflow lock could race with
 922         * the listener close
 923         */
 924        if (likely(subflow->pm_notified) || list_empty(&subflow->node))
 925                return true;
 926
 927        subflow->pm_notified = 1;
 928        if (subflow->mp_join) {
 929                clear_3rdack_retransmission(ssk);
 930                mptcp_pm_subflow_established(msk);
 931        } else {
 932                mptcp_pm_fully_established(msk, ssk, GFP_ATOMIC);
 933        }
 934        return true;
 935
 936reset:
 937        mptcp_subflow_reset(ssk);
 938        return false;
 939}
 940
 941u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
 942{
 943        u32 old_seq32, cur_seq32;
 944
 945        old_seq32 = (u32)old_seq;
 946        cur_seq32 = (u32)cur_seq;
 947        cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
 948        if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
 949                return cur_seq + (1LL << 32);
 950
 951        /* reverse wrap could happen, too */
 952        if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
 953                return cur_seq - (1LL << 32);
 954        return cur_seq;
 955}
 956
 957static void ack_update_msk(struct mptcp_sock *msk,
 958                           struct sock *ssk,
 959                           struct mptcp_options_received *mp_opt)
 960{
 961        u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
 962        struct sock *sk = (struct sock *)msk;
 963        u64 old_snd_una;
 964
 965        mptcp_data_lock(sk);
 966
 967        /* avoid ack expansion on update conflict, to reduce the risk of
 968         * wrongly expanding to a future ack sequence number, which is way
 969         * more dangerous than missing an ack
 970         */
 971        old_snd_una = msk->snd_una;
 972        new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 973
 974        /* ACK for data not even sent yet? Ignore. */
 975        if (after64(new_snd_una, snd_nxt))
 976                new_snd_una = old_snd_una;
 977
 978        new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
 979
 980        if (after64(new_wnd_end, msk->wnd_end))
 981                msk->wnd_end = new_wnd_end;
 982
 983        /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
 984        if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
 985                __mptcp_check_push(sk, ssk);
 986
 987        if (after64(new_snd_una, old_snd_una)) {
 988                msk->snd_una = new_snd_una;
 989                __mptcp_data_acked(sk);
 990        }
 991        mptcp_data_unlock(sk);
 992
 993        trace_ack_update_msk(mp_opt->data_ack,
 994                             old_snd_una, new_snd_una,
 995                             new_wnd_end, msk->wnd_end);
 996}
 997
 998bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
 999{
1000        /* Skip if DATA_FIN was already received.
1001         * If updating simultaneously with the recvmsg loop, values
1002         * should match. If they mismatch, the peer is misbehaving and
1003         * we will prefer the most recent information.
1004         */
1005        if (READ_ONCE(msk->rcv_data_fin))
1006                return false;
1007
1008        WRITE_ONCE(msk->rcv_data_fin_seq,
1009                   mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1010        WRITE_ONCE(msk->rcv_data_fin, 1);
1011
1012        return true;
1013}
1014
1015static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1016                                struct mptcp_options_received *mp_opt)
1017{
1018        u64 hmac = 0;
1019
1020        if (mp_opt->echo)
1021                return true;
1022
1023        hmac = add_addr_generate_hmac(msk->remote_key,
1024                                      msk->local_key,
1025                                      &mp_opt->addr);
1026
1027        pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1028                 msk, (unsigned long long)hmac,
1029                 (unsigned long long)mp_opt->ahmac);
1030
1031        return hmac == mp_opt->ahmac;
1032}
1033
1034/* Return false if a subflow has been reset, else return true */
1035bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1036{
1037        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1038        struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1039        struct mptcp_options_received mp_opt;
1040        struct mptcp_ext *mpext;
1041
1042        if (__mptcp_check_fallback(msk)) {
1043                /* Keep it simple and unconditionally trigger send data cleanup and
1044                 * pending queue spooling. We will need to acquire the data lock
1045                 * for more accurate checks, and once the lock is acquired, such
1046                 * helpers are cheap.
1047                 */
1048                mptcp_data_lock(subflow->conn);
1049                if (sk_stream_memory_free(sk))
1050                        __mptcp_check_push(subflow->conn, sk);
1051                __mptcp_data_acked(subflow->conn);
1052                mptcp_data_unlock(subflow->conn);
1053                return true;
1054        }
1055
1056        mptcp_get_options(sk, skb, &mp_opt);
1057
1058        /* The subflow can be in close state only if check_fully_established()
1059         * just sent a reset. If so, tell the caller to ignore the current packet.
1060         */
1061        if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1062                return sk->sk_state != TCP_CLOSE;
1063
1064        if (mp_opt.fastclose &&
1065            msk->local_key == mp_opt.rcvr_key) {
1066                WRITE_ONCE(msk->rcv_fastclose, true);
1067                mptcp_schedule_work((struct sock *)msk);
1068        }
1069
1070        if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
1071                if (!mp_opt.echo) {
1072                        mptcp_pm_add_addr_received(msk, &mp_opt.addr);
1073                        MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1074                } else {
1075                        mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1076                        mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1077                        MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1078                }
1079
1080                if (mp_opt.addr.port)
1081                        MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1082
1083                mp_opt.add_addr = 0;
1084        }
1085
1086        if (mp_opt.rm_addr) {
1087                mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1088                mp_opt.rm_addr = 0;
1089        }
1090
1091        if (mp_opt.mp_prio) {
1092                mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1093                MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1094                mp_opt.mp_prio = 0;
1095        }
1096
1097        if (mp_opt.reset) {
1098                subflow->reset_seen = 1;
1099                subflow->reset_reason = mp_opt.reset_reason;
1100                subflow->reset_transient = mp_opt.reset_transient;
1101        }
1102
1103        if (!mp_opt.dss)
1104                return true;
1105
1106        /* we can't wait for recvmsg() to update the ack_seq, otherwise
1107         * monodirectional flows will stuck
1108         */
1109        if (mp_opt.use_ack)
1110                ack_update_msk(msk, sk, &mp_opt);
1111
1112        /* Zero-data-length packets are dropped by the caller and not
1113         * propagated to the MPTCP layer, so the skb extension does not
1114         * need to be allocated or populated. DATA_FIN information, if
1115         * present, needs to be updated here before the skb is freed.
1116         */
1117        if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1118                if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1119                    mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
1120                    schedule_work(&msk->work))
1121                        sock_hold(subflow->conn);
1122
1123                return true;
1124        }
1125
1126        mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1127        if (!mpext)
1128                return true;
1129
1130        memset(mpext, 0, sizeof(*mpext));
1131
1132        if (mp_opt.use_map) {
1133                if (mp_opt.mpc_map) {
1134                        /* this is an MP_CAPABLE carrying MPTCP data
1135                         * we know this map the first chunk of data
1136                         */
1137                        mptcp_crypto_key_sha(subflow->remote_key, NULL,
1138                                             &mpext->data_seq);
1139                        mpext->data_seq++;
1140                        mpext->subflow_seq = 1;
1141                        mpext->dsn64 = 1;
1142                        mpext->mpc_map = 1;
1143                        mpext->data_fin = 0;
1144                } else {
1145                        mpext->data_seq = mp_opt.data_seq;
1146                        mpext->subflow_seq = mp_opt.subflow_seq;
1147                        mpext->dsn64 = mp_opt.dsn64;
1148                        mpext->data_fin = mp_opt.data_fin;
1149                }
1150                mpext->data_len = mp_opt.data_len;
1151                mpext->use_map = 1;
1152                mpext->csum_reqd = mp_opt.csum_reqd;
1153
1154                if (mpext->csum_reqd)
1155                        mpext->csum = mp_opt.csum;
1156        }
1157
1158        return true;
1159}
1160
1161static void mptcp_set_rwin(const struct tcp_sock *tp)
1162{
1163        const struct sock *ssk = (const struct sock *)tp;
1164        const struct mptcp_subflow_context *subflow;
1165        struct mptcp_sock *msk;
1166        u64 ack_seq;
1167
1168        subflow = mptcp_subflow_ctx(ssk);
1169        msk = mptcp_sk(subflow->conn);
1170
1171        ack_seq = READ_ONCE(msk->ack_seq) + tp->rcv_wnd;
1172
1173        if (after64(ack_seq, READ_ONCE(msk->rcv_wnd_sent)))
1174                WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
1175}
1176
1177static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
1178{
1179        struct csum_pseudo_header header;
1180        __wsum csum;
1181
1182        /* cfr RFC 8684 3.3.1.:
1183         * the data sequence number used in the pseudo-header is
1184         * always the 64-bit value, irrespective of what length is used in the
1185         * DSS option itself.
1186         */
1187        header.data_seq = cpu_to_be64(mpext->data_seq);
1188        header.subflow_seq = htonl(mpext->subflow_seq);
1189        header.data_len = htons(mpext->data_len);
1190        header.csum = 0;
1191
1192        csum = csum_partial(&header, sizeof(header), ~csum_unfold(mpext->csum));
1193        return (__force u16)csum_fold(csum);
1194}
1195
1196void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
1197                         struct mptcp_out_options *opts)
1198{
1199        if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
1200             OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
1201                u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1202
1203                if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1204                        len = TCPOLEN_MPTCP_MPC_SYN;
1205                } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1206                        len = TCPOLEN_MPTCP_MPC_SYNACK;
1207                } else if (opts->ext_copy.data_len) {
1208                        len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1209                        if (opts->csum_reqd)
1210                                len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1211                } else {
1212                        len = TCPOLEN_MPTCP_MPC_ACK;
1213                }
1214
1215                if (opts->csum_reqd)
1216                        flag |= MPTCP_CAP_CHECKSUM_REQD;
1217
1218                if (!opts->allow_join_id0)
1219                        flag |= MPTCP_CAP_DENY_JOIN_ID0;
1220
1221                *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1222                                      MPTCP_SUPPORTED_VERSION,
1223                                      flag);
1224
1225                if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1226                    opts->suboptions))
1227                        goto mp_capable_done;
1228
1229                put_unaligned_be64(opts->sndr_key, ptr);
1230                ptr += 2;
1231                if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1232                        goto mp_capable_done;
1233
1234                put_unaligned_be64(opts->rcvr_key, ptr);
1235                ptr += 2;
1236                if (!opts->ext_copy.data_len)
1237                        goto mp_capable_done;
1238
1239                if (opts->csum_reqd) {
1240                        put_unaligned_be32(opts->ext_copy.data_len << 16 |
1241                                           mptcp_make_csum(&opts->ext_copy), ptr);
1242                } else {
1243                        put_unaligned_be32(opts->ext_copy.data_len << 16 |
1244                                           TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1245                }
1246                ptr += 1;
1247        }
1248
1249mp_capable_done:
1250        if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1251                u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1252                u8 echo = MPTCP_ADDR_ECHO;
1253
1254#if IS_ENABLED(CONFIG_MPTCP_IPV6)
1255                if (opts->addr.family == AF_INET6)
1256                        len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1257#endif
1258
1259                if (opts->addr.port)
1260                        len += TCPOLEN_MPTCP_PORT_LEN;
1261
1262                if (opts->ahmac) {
1263                        len += sizeof(opts->ahmac);
1264                        echo = 0;
1265                }
1266
1267                *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1268                                      len, echo, opts->addr.id);
1269                if (opts->addr.family == AF_INET) {
1270                        memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1271                        ptr += 1;
1272                }
1273#if IS_ENABLED(CONFIG_MPTCP_IPV6)
1274                else if (opts->addr.family == AF_INET6) {
1275                        memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1276                        ptr += 4;
1277                }
1278#endif
1279
1280                if (!opts->addr.port) {
1281                        if (opts->ahmac) {
1282                                put_unaligned_be64(opts->ahmac, ptr);
1283                                ptr += 2;
1284                        }
1285                } else {
1286                        u16 port = ntohs(opts->addr.port);
1287
1288                        if (opts->ahmac) {
1289                                u8 *bptr = (u8 *)ptr;
1290
1291                                put_unaligned_be16(port, bptr);
1292                                bptr += 2;
1293                                put_unaligned_be64(opts->ahmac, bptr);
1294                                bptr += 8;
1295                                put_unaligned_be16(TCPOPT_NOP << 8 |
1296                                                   TCPOPT_NOP, bptr);
1297
1298                                ptr += 3;
1299                        } else {
1300                                put_unaligned_be32(port << 16 |
1301                                                   TCPOPT_NOP << 8 |
1302                                                   TCPOPT_NOP, ptr);
1303                                ptr += 1;
1304                        }
1305                }
1306        }
1307
1308        if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1309                u8 i = 1;
1310
1311                *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1312                                      TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1313                                      0, opts->rm_list.ids[0]);
1314
1315                while (i < opts->rm_list.nr) {
1316                        u8 id1, id2, id3, id4;
1317
1318                        id1 = opts->rm_list.ids[i];
1319                        id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1320                        id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1321                        id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1322                        put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1323                        ptr += 1;
1324                        i += 4;
1325                }
1326        }
1327
1328        if (OPTION_MPTCP_PRIO & opts->suboptions) {
1329                const struct sock *ssk = (const struct sock *)tp;
1330                struct mptcp_subflow_context *subflow;
1331
1332                subflow = mptcp_subflow_ctx(ssk);
1333                subflow->send_mp_prio = 0;
1334
1335                *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1336                                      TCPOLEN_MPTCP_PRIO,
1337                                      opts->backup, TCPOPT_NOP);
1338        }
1339
1340        if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1341                *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1342                                      TCPOLEN_MPTCP_MPJ_SYN,
1343                                      opts->backup, opts->join_id);
1344                put_unaligned_be32(opts->token, ptr);
1345                ptr += 1;
1346                put_unaligned_be32(opts->nonce, ptr);
1347                ptr += 1;
1348        }
1349
1350        if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1351                *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1352                                      TCPOLEN_MPTCP_MPJ_SYNACK,
1353                                      opts->backup, opts->join_id);
1354                put_unaligned_be64(opts->thmac, ptr);
1355                ptr += 2;
1356                put_unaligned_be32(opts->nonce, ptr);
1357                ptr += 1;
1358        }
1359
1360        if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
1361                *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1362                                      TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1363                memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1364                ptr += 5;
1365        }
1366
1367        if (OPTION_MPTCP_RST & opts->suboptions)
1368                *ptr++ = mptcp_option(MPTCPOPT_RST,
1369                                      TCPOLEN_MPTCP_RST,
1370                                      opts->reset_transient,
1371                                      opts->reset_reason);
1372
1373        if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
1374                struct mptcp_ext *mpext = &opts->ext_copy;
1375                u8 len = TCPOLEN_MPTCP_DSS_BASE;
1376                u8 flags = 0;
1377
1378                if (mpext->use_ack) {
1379                        flags = MPTCP_DSS_HAS_ACK;
1380                        if (mpext->ack64) {
1381                                len += TCPOLEN_MPTCP_DSS_ACK64;
1382                                flags |= MPTCP_DSS_ACK64;
1383                        } else {
1384                                len += TCPOLEN_MPTCP_DSS_ACK32;
1385                        }
1386                }
1387
1388                if (mpext->use_map) {
1389                        len += TCPOLEN_MPTCP_DSS_MAP64;
1390
1391                        /* Use only 64-bit mapping flags for now, add
1392                         * support for optional 32-bit mappings later.
1393                         */
1394                        flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1395                        if (mpext->data_fin)
1396                                flags |= MPTCP_DSS_DATA_FIN;
1397
1398                        if (opts->csum_reqd)
1399                                len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1400                }
1401
1402                *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1403
1404                if (mpext->use_ack) {
1405                        if (mpext->ack64) {
1406                                put_unaligned_be64(mpext->data_ack, ptr);
1407                                ptr += 2;
1408                        } else {
1409                                put_unaligned_be32(mpext->data_ack32, ptr);
1410                                ptr += 1;
1411                        }
1412                }
1413
1414                if (mpext->use_map) {
1415                        put_unaligned_be64(mpext->data_seq, ptr);
1416                        ptr += 2;
1417                        put_unaligned_be32(mpext->subflow_seq, ptr);
1418                        ptr += 1;
1419                        if (opts->csum_reqd) {
1420                                put_unaligned_be32(mpext->data_len << 16 |
1421                                                   mptcp_make_csum(mpext), ptr);
1422                        } else {
1423                                put_unaligned_be32(mpext->data_len << 16 |
1424                                                   TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1425                        }
1426                }
1427        }
1428
1429        if (tp)
1430                mptcp_set_rwin(tp);
1431}
1432
1433__be32 mptcp_get_reset_option(const struct sk_buff *skb)
1434{
1435        const struct mptcp_ext *ext = mptcp_get_ext(skb);
1436        u8 flags, reason;
1437
1438        if (ext) {
1439                flags = ext->reset_transient;
1440                reason = ext->reset_reason;
1441
1442                return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1443                                    flags, reason);
1444        }
1445
1446        return htonl(0u);
1447}
1448EXPORT_SYMBOL_GPL(mptcp_get_reset_option);
1449