net/mptcp/subflow.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 <linux/module.h>
  11 #include <linux/netdevice.h>
  12 #include <crypto/sha2.h>
  13 #include <crypto/utils.h>
  14 #include <net/sock.h>
  15 #include <net/inet_common.h>
  16 #include <net/inet_hashtables.h>
  17 #include <net/protocol.h>
  18 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
  19 #include <net/ip6_route.h>
  20 #include <net/transp_v6.h>
  21 #endif
  22 #include <net/mptcp.h>
  23
  24 #include "protocol.h"
  25 #include "mib.h"
  26
  27 #include <trace/events/mptcp.h>
  28 #include <trace/events/sock.h>
  29
  30 static void mptcp_subflow_ops_undo_override(struct sock *ssk);
  31
  32 static void SUBFLOW_REQ_INC_STATS(struct request_sock *req,
  33                                   enum linux_mptcp_mib_field field)
  34 {
  35         MPTCP_INC_STATS(sock_net(req_to_sk(req)), field);
  36 }
  37
  38 static void subflow_req_destructor(struct request_sock *req)
  39 {
  40         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
  41
  42         pr_debug("subflow_req=%p\n", subflow_req);
  43
  44         if (subflow_req->msk)
  45                 sock_put((struct sock *)subflow_req->msk);
  46
  47         mptcp_token_destroy_request(req);
  48 }
  49
  50 static void subflow_generate_hmac(u64 key1, u64 key2, u32 nonce1, u32 nonce2,
  51                                   void *hmac)
  52 {
  53         u8 msg[8];
  54
  55         put_unaligned_be32(nonce1, &msg[0]);
  56         put_unaligned_be32(nonce2, &msg[4]);
  57
  58         mptcp_crypto_hmac_sha(key1, key2, msg, 8, hmac);
  59 }
  60
  61 static bool mptcp_can_accept_new_subflow(const struct mptcp_sock *msk)
  62 {
  63         return mptcp_is_fully_established((void *)msk) &&
  64                 ((mptcp_pm_is_userspace(msk) &&
  65                   mptcp_userspace_pm_active(msk)) ||
  66                  READ_ONCE(msk->pm.accept_subflow));
  67 }
  68
  69 /* validate received token and create truncated hmac and nonce for SYN-ACK */
  70 static void subflow_req_create_thmac(struct mptcp_subflow_request_sock *subflow_req)
  71 {
  72         struct mptcp_sock *msk = subflow_req->msk;
  73         u8 hmac[SHA256_DIGEST_SIZE];
  74
  75         get_random_bytes(&subflow_req->local_nonce, sizeof(u32));
  76
  77         subflow_generate_hmac(READ_ONCE(msk->local_key),
  78                               READ_ONCE(msk->remote_key),
  79                               subflow_req->local_nonce,
  80                               subflow_req->remote_nonce, hmac);
  81
  82         subflow_req->thmac = get_unaligned_be64(hmac);
  83 }
  84
  85 static struct mptcp_sock *subflow_token_join_request(struct request_sock *req)
  86 {
  87         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
  88         struct mptcp_sock *msk;
  89         int local_id;
  90
  91         msk = mptcp_token_get_sock(sock_net(req_to_sk(req)), subflow_req->token);
  92         if (!msk) {
  93                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINNOTOKEN);
  94                 return NULL;
  95         }
  96
  97         local_id = mptcp_pm_get_local_id(msk, (struct sock_common *)req);
  98         if (local_id < 0) {
  99                 sock_put((struct sock *)msk);
 100                 return NULL;
 101         }
 102         subflow_req->local_id = local_id;
 103         subflow_req->request_bkup = mptcp_pm_is_backup(msk, (struct sock_common *)req);
 104
 105         return msk;
 106 }
 107
 108 static void subflow_init_req(struct request_sock *req, const struct sock *sk_listener)
 109 {
 110         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 111
 112         subflow_req->mp_capable = 0;
 113         subflow_req->mp_join = 0;
 114         subflow_req->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk_listener));
 115         subflow_req->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk_listener));
 116         subflow_req->msk = NULL;
 117         mptcp_token_init_request(req);
 118 }
 119
 120 static bool subflow_use_different_sport(struct mptcp_sock *msk, const struct sock *sk)
 121 {
 122         return inet_sk(sk)->inet_sport != inet_sk((struct sock *)msk)->inet_sport;
 123 }
 124
 125 static void subflow_add_reset_reason(struct sk_buff *skb, u8 reason)
 126 {
 127         struct mptcp_ext *mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
 128
 129         if (mpext) {
 130                 memset(mpext, 0, sizeof(*mpext));
 131                 mpext->reset_reason = reason;
 132         }
 133 }
 134
 135 static int subflow_reset_req_endp(struct request_sock *req, struct sk_buff *skb)
 136 {
 137         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEENDPATTEMPT);
 138         subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
 139         return -EPERM;
 140 }
 141
 142 /* Init mptcp request socket.
 143  *
 144  * Returns an error code if a JOIN has failed and a TCP reset
 145  * should be sent.
 146  */
 147 static int subflow_check_req(struct request_sock *req,
 148                              const struct sock *sk_listener,
 149                              struct sk_buff *skb)
 150 {
 151         struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
 152         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 153         struct mptcp_options_received mp_opt;
 154         bool opt_mp_capable, opt_mp_join;
 155
 156         pr_debug("subflow_req=%p, listener=%p\n", subflow_req, listener);
 157
 158 #ifdef CONFIG_TCP_MD5SIG
 159         /* no MPTCP if MD5SIG is enabled on this socket or we may run out of
 160          * TCP option space.
 161          */
 162         if (rcu_access_pointer(tcp_sk(sk_listener)->md5sig_info)) {
 163                 subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
 164                 return -EINVAL;
 165         }
 166 #endif
 167
 168         mptcp_get_options(skb, &mp_opt);
 169
 170         opt_mp_capable = !!(mp_opt.suboptions & OPTION_MPTCP_MPC_SYN);
 171         opt_mp_join = !!(mp_opt.suboptions & OPTION_MPTCP_MPJ_SYN);
 172         if (opt_mp_capable) {
 173                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVE);
 174
 175                 if (unlikely(listener->pm_listener))
 176                         return subflow_reset_req_endp(req, skb);
 177                 if (opt_mp_join)
 178                         return 0;
 179         } else if (opt_mp_join) {
 180                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNRX);
 181
 182                 if (mp_opt.backup)
 183                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNBACKUPRX);
 184         } else if (unlikely(listener->pm_listener)) {
 185                 return subflow_reset_req_endp(req, skb);
 186         }
 187
 188         if (opt_mp_capable && listener->request_mptcp) {
 189                 int err, retries = MPTCP_TOKEN_MAX_RETRIES;
 190
 191                 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
 192 again:
 193                 do {
 194                         get_random_bytes(&subflow_req->local_key, sizeof(subflow_req->local_key));
 195                 } while (subflow_req->local_key == 0);
 196
 197                 if (unlikely(req->syncookie)) {
 198                         mptcp_crypto_key_sha(subflow_req->local_key,
 199                                              &subflow_req->token,
 200                                              &subflow_req->idsn);
 201                         if (mptcp_token_exists(subflow_req->token)) {
 202                                 if (retries-- > 0)
 203                                         goto again;
 204                                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
 205                         } else {
 206                                 subflow_req->mp_capable = 1;
 207                         }
 208                         return 0;
 209                 }
 210
 211                 err = mptcp_token_new_request(req);
 212                 if (err == 0)
 213                         subflow_req->mp_capable = 1;
 214                 else if (retries-- > 0)
 215                         goto again;
 216                 else
 217                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
 218
 219         } else if (opt_mp_join && listener->request_mptcp) {
 220                 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
 221                 subflow_req->mp_join = 1;
 222                 subflow_req->backup = mp_opt.backup;
 223                 subflow_req->remote_id = mp_opt.join_id;
 224                 subflow_req->token = mp_opt.token;
 225                 subflow_req->remote_nonce = mp_opt.nonce;
 226                 subflow_req->msk = subflow_token_join_request(req);
 227
 228                 /* Can't fall back to TCP in this case. */
 229                 if (!subflow_req->msk) {
 230                         subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
 231                         return -EPERM;
 232                 }
 233
 234                 if (subflow_use_different_sport(subflow_req->msk, sk_listener)) {
 235                         pr_debug("syn inet_sport=%d %d\n",
 236                                  ntohs(inet_sk(sk_listener)->inet_sport),
 237                                  ntohs(inet_sk((struct sock *)subflow_req->msk)->inet_sport));
 238                         if (!mptcp_pm_sport_in_anno_list(subflow_req->msk, sk_listener)) {
 239                                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTSYNRX);
 240                                 subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
 241                                 return -EPERM;
 242                         }
 243                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTSYNRX);
 244                 }
 245
 246                 subflow_req_create_thmac(subflow_req);
 247
 248                 if (unlikely(req->syncookie)) {
 249                         if (!mptcp_can_accept_new_subflow(subflow_req->msk)) {
 250                                 subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
 251                                 return -EPERM;
 252                         }
 253
 254                         subflow_init_req_cookie_join_save(subflow_req, skb);
 255                 }
 256
 257                 pr_debug("token=%u, remote_nonce=%u msk=%p\n", subflow_req->token,
 258                          subflow_req->remote_nonce, subflow_req->msk);
 259         }
 260
 261         return 0;
 262 }
 263
 264 int mptcp_subflow_init_cookie_req(struct request_sock *req,
 265                                   const struct sock *sk_listener,
 266                                   struct sk_buff *skb)
 267 {
 268         struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
 269         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 270         struct mptcp_options_received mp_opt;
 271         bool opt_mp_capable, opt_mp_join;
 272         int err;
 273
 274         subflow_init_req(req, sk_listener);
 275         mptcp_get_options(skb, &mp_opt);
 276
 277         opt_mp_capable = !!(mp_opt.suboptions & OPTION_MPTCP_MPC_ACK);
 278         opt_mp_join = !!(mp_opt.suboptions & OPTION_MPTCP_MPJ_ACK);
 279         if (opt_mp_capable && opt_mp_join)
 280                 return -EINVAL;
 281
 282         if (opt_mp_capable && listener->request_mptcp) {
 283                 if (mp_opt.sndr_key == 0)
 284                         return -EINVAL;
 285
 286                 subflow_req->local_key = mp_opt.rcvr_key;
 287                 err = mptcp_token_new_request(req);
 288                 if (err)
 289                         return err;
 290
 291                 subflow_req->mp_capable = 1;
 292                 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
 293         } else if (opt_mp_join && listener->request_mptcp) {
 294                 if (!mptcp_token_join_cookie_init_state(subflow_req, skb))
 295                         return -EINVAL;
 296
 297                 subflow_req->mp_join = 1;
 298                 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
 299         }
 300
 301         return 0;
 302 }
 303 EXPORT_SYMBOL_GPL(mptcp_subflow_init_cookie_req);
 304
 305 static enum sk_rst_reason mptcp_get_rst_reason(const struct sk_buff *skb)
 306 {
 307         const struct mptcp_ext *mpext = mptcp_get_ext(skb);
 308
 309         if (!mpext)
 310                 return SK_RST_REASON_NOT_SPECIFIED;
 311
 312         return sk_rst_convert_mptcp_reason(mpext->reset_reason);
 313 }
 314
 315 static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
 316                                               struct sk_buff *skb,
 317                                               struct flowi *fl,
 318                                               struct request_sock *req,
 319                                               u32 tw_isn)
 320 {
 321         struct dst_entry *dst;
 322         int err;
 323
 324         tcp_rsk(req)->is_mptcp = 1;
 325         subflow_init_req(req, sk);
 326
 327         dst = tcp_request_sock_ipv4_ops.route_req(sk, skb, fl, req, tw_isn);
 328         if (!dst)
 329                 return NULL;
 330
 331         err = subflow_check_req(req, sk, skb);
 332         if (err == 0)
 333                 return dst;
 334
 335         dst_release(dst);
 336         if (!req->syncookie)
 337                 tcp_request_sock_ops.send_reset(sk, skb,
 338                                                 mptcp_get_rst_reason(skb));
 339         return NULL;
 340 }
 341
 342 static void subflow_prep_synack(const struct sock *sk, struct request_sock *req,
 343                                 struct tcp_fastopen_cookie *foc,
 344                                 enum tcp_synack_type synack_type)
 345 {
 346         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 347         struct inet_request_sock *ireq = inet_rsk(req);
 348
 349         /* clear tstamp_ok, as needed depending on cookie */
 350         if (foc && foc->len > -1)
 351                 ireq->tstamp_ok = 0;
 352
 353         if (synack_type == TCP_SYNACK_FASTOPEN)
 354                 mptcp_fastopen_subflow_synack_set_params(subflow, req);
 355 }
 356
 357 static int subflow_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
 358                                   struct flowi *fl,
 359                                   struct request_sock *req,
 360                                   struct tcp_fastopen_cookie *foc,
 361                                   enum tcp_synack_type synack_type,
 362                                   struct sk_buff *syn_skb)
 363 {
 364         subflow_prep_synack(sk, req, foc, synack_type);
 365
 366         return tcp_request_sock_ipv4_ops.send_synack(sk, dst, fl, req, foc,
 367                                                      synack_type, syn_skb);
 368 }
 369
 370 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 371 static int subflow_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
 372                                   struct flowi *fl,
 373                                   struct request_sock *req,
 374                                   struct tcp_fastopen_cookie *foc,
 375                                   enum tcp_synack_type synack_type,
 376                                   struct sk_buff *syn_skb)
 377 {
 378         subflow_prep_synack(sk, req, foc, synack_type);
 379
 380         return tcp_request_sock_ipv6_ops.send_synack(sk, dst, fl, req, foc,
 381                                                      synack_type, syn_skb);
 382 }
 383
 384 static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
 385                                               struct sk_buff *skb,
 386                                               struct flowi *fl,
 387                                               struct request_sock *req,
 388                                               u32 tw_isn)
 389 {
 390         struct dst_entry *dst;
 391         int err;
 392
 393         tcp_rsk(req)->is_mptcp = 1;
 394         subflow_init_req(req, sk);
 395
 396         dst = tcp_request_sock_ipv6_ops.route_req(sk, skb, fl, req, tw_isn);
 397         if (!dst)
 398                 return NULL;
 399
 400         err = subflow_check_req(req, sk, skb);
 401         if (err == 0)
 402                 return dst;
 403
 404         dst_release(dst);
 405         if (!req->syncookie)
 406                 tcp6_request_sock_ops.send_reset(sk, skb,
 407                                                  mptcp_get_rst_reason(skb));
 408         return NULL;
 409 }
 410 #endif
 411
 412 /* validate received truncated hmac and create hmac for third ACK */
 413 static bool subflow_thmac_valid(struct mptcp_subflow_context *subflow)
 414 {
 415         u8 hmac[SHA256_DIGEST_SIZE];
 416         u64 thmac;
 417
 418         subflow_generate_hmac(subflow->remote_key, subflow->local_key,
 419                               subflow->remote_nonce, subflow->local_nonce,
 420                               hmac);
 421
 422         thmac = get_unaligned_be64(hmac);
 423         pr_debug("subflow=%p, token=%u, thmac=%llu, subflow->thmac=%llu\n",
 424                  subflow, subflow->token, thmac, subflow->thmac);
 425
 426         return thmac == subflow->thmac;
 427 }
 428
 429 void mptcp_subflow_reset(struct sock *ssk)
 430 {
 431         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 432         struct sock *sk = subflow->conn;
 433
 434         /* mptcp_mp_fail_no_response() can reach here on an already closed
 435          * socket
 436          */
 437         if (ssk->sk_state == TCP_CLOSE)
 438                 return;
 439
 440         /* must hold: tcp_done() could drop last reference on parent */
 441         sock_hold(sk);
 442
 443         mptcp_send_active_reset_reason(ssk);
 444         tcp_done(ssk);
 445         if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags))
 446                 mptcp_schedule_work(sk);
 447
 448         sock_put(sk);
 449 }
 450
 451 static bool subflow_use_different_dport(struct mptcp_sock *msk, const struct sock *sk)
 452 {
 453         return inet_sk(sk)->inet_dport != inet_sk((struct sock *)msk)->inet_dport;
 454 }
 455
 456 void __mptcp_sync_state(struct sock *sk, int state)
 457 {
 458         struct mptcp_subflow_context *subflow;
 459         struct mptcp_sock *msk = mptcp_sk(sk);
 460         struct sock *ssk = msk->first;
 461
 462         subflow = mptcp_subflow_ctx(ssk);
 463         __mptcp_propagate_sndbuf(sk, ssk);
 464         if (!msk->rcvspace_init)
 465                 mptcp_rcv_space_init(msk, ssk);
 466
 467         if (sk->sk_state == TCP_SYN_SENT) {
 468                 /* subflow->idsn is always available is TCP_SYN_SENT state,
 469                  * even for the FASTOPEN scenarios
 470                  */
 471                 WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
 472                 WRITE_ONCE(msk->snd_nxt, msk->write_seq);
 473                 mptcp_set_state(sk, state);
 474                 sk->sk_state_change(sk);
 475         }
 476 }
 477
 478 static void subflow_set_remote_key(struct mptcp_sock *msk,
 479                                    struct mptcp_subflow_context *subflow,
 480                                    const struct mptcp_options_received *mp_opt)
 481 {
 482         /* active MPC subflow will reach here multiple times:
 483          * at subflow_finish_connect() time and at 4th ack time
 484          */
 485         if (subflow->remote_key_valid)
 486                 return;
 487
 488         subflow->remote_key_valid = 1;
 489         subflow->remote_key = mp_opt->sndr_key;
 490         mptcp_crypto_key_sha(subflow->remote_key, NULL, &subflow->iasn);
 491         subflow->iasn++;
 492
 493         WRITE_ONCE(msk->remote_key, subflow->remote_key);
 494         WRITE_ONCE(msk->ack_seq, subflow->iasn);
 495         WRITE_ONCE(msk->can_ack, true);
 496         atomic64_set(&msk->rcv_wnd_sent, subflow->iasn);
 497 }
 498
 499 static void mptcp_propagate_state(struct sock *sk, struct sock *ssk,
 500                                   struct mptcp_subflow_context *subflow,
 501                                   const struct mptcp_options_received *mp_opt)
 502 {
 503         struct mptcp_sock *msk = mptcp_sk(sk);
 504
 505         mptcp_data_lock(sk);
 506         if (mp_opt) {
 507                 /* Options are available only in the non fallback cases
 508                  * avoid updating rx path fields otherwise
 509                  */
 510                 WRITE_ONCE(msk->snd_una, subflow->idsn + 1);
 511                 WRITE_ONCE(msk->wnd_end, subflow->idsn + 1 + tcp_sk(ssk)->snd_wnd);
 512                 subflow_set_remote_key(msk, subflow, mp_opt);
 513         }
 514
 515         if (!sock_owned_by_user(sk)) {
 516                 __mptcp_sync_state(sk, ssk->sk_state);
 517         } else {
 518                 msk->pending_state = ssk->sk_state;
 519                 __set_bit(MPTCP_SYNC_STATE, &msk->cb_flags);
 520         }
 521         mptcp_data_unlock(sk);
 522 }
 523
 524 static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 525 {
 526         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 527         struct mptcp_options_received mp_opt;
 528         struct sock *parent = subflow->conn;
 529         struct mptcp_sock *msk;
 530
 531         subflow->icsk_af_ops->sk_rx_dst_set(sk, skb);
 532
 533         /* be sure no special action on any packet other than syn-ack */
 534         if (subflow->conn_finished)
 535                 return;
 536
 537         msk = mptcp_sk(parent);
 538         subflow->rel_write_seq = 1;
 539         subflow->conn_finished = 1;
 540         subflow->ssn_offset = TCP_SKB_CB(skb)->seq;
 541         pr_debug("subflow=%p synack seq=%x\n", subflow, subflow->ssn_offset);
 542
 543         mptcp_get_options(skb, &mp_opt);
 544         if (subflow->request_mptcp) {
 545                 if (!(mp_opt.suboptions & OPTION_MPTCP_MPC_SYNACK)) {
 546                         MPTCP_INC_STATS(sock_net(sk),
 547                                         MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
 548                         mptcp_do_fallback(sk);
 549                         pr_fallback(msk);
 550                         goto fallback;
 551                 }
 552
 553                 if (mp_opt.suboptions & OPTION_MPTCP_CSUMREQD)
 554                         WRITE_ONCE(msk->csum_enabled, true);
 555                 if (mp_opt.deny_join_id0)
 556                         WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 557                 subflow->mp_capable = 1;
 558                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVEACK);
 559                 mptcp_finish_connect(sk);
 560                 mptcp_active_enable(parent);
 561                 mptcp_propagate_state(parent, sk, subflow, &mp_opt);
 562         } else if (subflow->request_join) {
 563                 u8 hmac[SHA256_DIGEST_SIZE];
 564
 565                 if (!(mp_opt.suboptions & OPTION_MPTCP_MPJ_SYNACK)) {
 566                         subflow->reset_reason = MPTCP_RST_EMPTCP;
 567                         goto do_reset;
 568                 }
 569
 570                 subflow->backup = mp_opt.backup;
 571                 subflow->thmac = mp_opt.thmac;
 572                 subflow->remote_nonce = mp_opt.nonce;
 573                 WRITE_ONCE(subflow->remote_id, mp_opt.join_id);
 574                 pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u backup=%d\n",
 575                          subflow, subflow->thmac, subflow->remote_nonce,
 576                          subflow->backup);
 577
 578                 if (!subflow_thmac_valid(subflow)) {
 579                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINACKMAC);
 580                         subflow->reset_reason = MPTCP_RST_EMPTCP;
 581                         goto do_reset;
 582                 }
 583
 584                 if (!mptcp_finish_join(sk))
 585                         goto do_reset;
 586
 587                 subflow_generate_hmac(subflow->local_key, subflow->remote_key,
 588                                       subflow->local_nonce,
 589                                       subflow->remote_nonce,
 590                                       hmac);
 591                 memcpy(subflow->hmac, hmac, MPTCPOPT_HMAC_LEN);
 592
 593                 subflow->mp_join = 1;
 594                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKRX);
 595
 596                 if (subflow->backup)
 597                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKBACKUPRX);
 598
 599                 if (subflow_use_different_dport(msk, sk)) {
 600                         pr_debug("synack inet_dport=%d %d\n",
 601                                  ntohs(inet_sk(sk)->inet_dport),
 602                                  ntohs(inet_sk(parent)->inet_dport));
 603                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINPORTSYNACKRX);
 604                 }
 605         } else if (mptcp_check_fallback(sk)) {
 606                 /* It looks like MPTCP is blocked, while TCP is not */
 607                 if (subflow->mpc_drop)
 608                         mptcp_active_disable(parent);
 609 fallback:
 610                 mptcp_propagate_state(parent, sk, subflow, NULL);
 611         }
 612         return;
 613
 614 do_reset:
 615         subflow->reset_transient = 0;
 616         mptcp_subflow_reset(sk);
 617 }
 618
 619 static void subflow_set_local_id(struct mptcp_subflow_context *subflow, int local_id)
 620 {
 621         WARN_ON_ONCE(local_id < 0 || local_id > 255);
 622         WRITE_ONCE(subflow->local_id, local_id);
 623 }
 624
 625 static int subflow_chk_local_id(struct sock *sk)
 626 {
 627         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 628         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 629         int err;
 630
 631         if (likely(subflow->local_id >= 0))
 632                 return 0;
 633
 634         err = mptcp_pm_get_local_id(msk, (struct sock_common *)sk);
 635         if (err < 0)
 636                 return err;
 637
 638         subflow_set_local_id(subflow, err);
 639         subflow->request_bkup = mptcp_pm_is_backup(msk, (struct sock_common *)sk);
 640
 641         return 0;
 642 }
 643
 644 static int subflow_rebuild_header(struct sock *sk)
 645 {
 646         int err = subflow_chk_local_id(sk);
 647
 648         if (unlikely(err < 0))
 649                 return err;
 650
 651         return inet_sk_rebuild_header(sk);
 652 }
 653
 654 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 655 static int subflow_v6_rebuild_header(struct sock *sk)
 656 {
 657         int err = subflow_chk_local_id(sk);
 658
 659         if (unlikely(err < 0))
 660                 return err;
 661
 662         return inet6_sk_rebuild_header(sk);
 663 }
 664 #endif
 665
 666 static struct request_sock_ops mptcp_subflow_v4_request_sock_ops __ro_after_init;
 667 static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops __ro_after_init;
 668
 669 static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 670 {
 671         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 672
 673         pr_debug("subflow=%p\n", subflow);
 674
 675         /* Never answer to SYNs sent to broadcast or multicast */
 676         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 677                 goto drop;
 678
 679         return tcp_conn_request(&mptcp_subflow_v4_request_sock_ops,
 680                                 &subflow_request_sock_ipv4_ops,
 681                                 sk, skb);
 682 drop:
 683         tcp_listendrop(sk);
 684         return 0;
 685 }
 686
 687 static void subflow_v4_req_destructor(struct request_sock *req)
 688 {
 689         subflow_req_destructor(req);
 690         tcp_request_sock_ops.destructor(req);
 691 }
 692
 693 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 694 static struct request_sock_ops mptcp_subflow_v6_request_sock_ops __ro_after_init;
 695 static struct tcp_request_sock_ops subflow_request_sock_ipv6_ops __ro_after_init;
 696 static struct inet_connection_sock_af_ops subflow_v6_specific __ro_after_init;
 697 static struct inet_connection_sock_af_ops subflow_v6m_specific __ro_after_init;
 698 static struct proto tcpv6_prot_override __ro_after_init;
 699
 700 static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 701 {
 702         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 703
 704         pr_debug("subflow=%p\n", subflow);
 705
 706         if (skb->protocol == htons(ETH_P_IP))
 707                 return subflow_v4_conn_request(sk, skb);
 708
 709         if (!ipv6_unicast_destination(skb))
 710                 goto drop;
 711
 712         if (ipv6_addr_v4mapped(&ipv6_hdr(skb)->saddr)) {
 713                 __IP6_INC_STATS(sock_net(sk), NULL, IPSTATS_MIB_INHDRERRORS);
 714                 return 0;
 715         }
 716
 717         return tcp_conn_request(&mptcp_subflow_v6_request_sock_ops,
 718                                 &subflow_request_sock_ipv6_ops, sk, skb);
 719
 720 drop:
 721         tcp_listendrop(sk);
 722         return 0; /* don't send reset */
 723 }
 724
 725 static void subflow_v6_req_destructor(struct request_sock *req)
 726 {
 727         subflow_req_destructor(req);
 728         tcp6_request_sock_ops.destructor(req);
 729 }
 730 #endif
 731
 732 struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
 733                                                struct sock *sk_listener,
 734                                                bool attach_listener)
 735 {
 736         if (ops->family == AF_INET)
 737                 ops = &mptcp_subflow_v4_request_sock_ops;
 738 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 739         else if (ops->family == AF_INET6)
 740                 ops = &mptcp_subflow_v6_request_sock_ops;
 741 #endif
 742
 743         return inet_reqsk_alloc(ops, sk_listener, attach_listener);
 744 }
 745 EXPORT_SYMBOL(mptcp_subflow_reqsk_alloc);
 746
 747 /* validate hmac received in third ACK */
 748 static bool subflow_hmac_valid(const struct request_sock *req,
 749                                const struct mptcp_options_received *mp_opt)
 750 {
 751         const struct mptcp_subflow_request_sock *subflow_req;
 752         u8 hmac[SHA256_DIGEST_SIZE];
 753         struct mptcp_sock *msk;
 754
 755         subflow_req = mptcp_subflow_rsk(req);
 756         msk = subflow_req->msk;
 757         if (!msk)
 758                 return false;
 759
 760         subflow_generate_hmac(READ_ONCE(msk->remote_key),
 761                               READ_ONCE(msk->local_key),
 762                               subflow_req->remote_nonce,
 763                               subflow_req->local_nonce, hmac);
 764
 765         return !crypto_memneq(hmac, mp_opt->hmac, MPTCPOPT_HMAC_LEN);
 766 }
 767
 768 static void subflow_ulp_fallback(struct sock *sk,
 769                                  struct mptcp_subflow_context *old_ctx)
 770 {
 771         struct inet_connection_sock *icsk = inet_csk(sk);
 772
 773         mptcp_subflow_tcp_fallback(sk, old_ctx);
 774         icsk->icsk_ulp_ops = NULL;
 775         rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
 776         tcp_sk(sk)->is_mptcp = 0;
 777
 778         mptcp_subflow_ops_undo_override(sk);
 779 }
 780
 781 void mptcp_subflow_drop_ctx(struct sock *ssk)
 782 {
 783         struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
 784
 785         if (!ctx)
 786                 return;
 787
 788         list_del(&mptcp_subflow_ctx(ssk)->node);
 789         if (inet_csk(ssk)->icsk_ulp_ops) {
 790                 subflow_ulp_fallback(ssk, ctx);
 791                 if (ctx->conn)
 792                         sock_put(ctx->conn);
 793         }
 794
 795         kfree_rcu(ctx, rcu);
 796 }
 797
 798 void __mptcp_subflow_fully_established(struct mptcp_sock *msk,
 799                                        struct mptcp_subflow_context *subflow,
 800                                        const struct mptcp_options_received *mp_opt)
 801 {
 802         subflow_set_remote_key(msk, subflow, mp_opt);
 803         WRITE_ONCE(subflow->fully_established, true);
 804         WRITE_ONCE(msk->fully_established, true);
 805
 806         if (subflow->is_mptfo)
 807                 __mptcp_fastopen_gen_msk_ackseq(msk, subflow, mp_opt);
 808 }
 809
 810 static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 811                                           struct sk_buff *skb,
 812                                           struct request_sock *req,
 813                                           struct dst_entry *dst,
 814                                           struct request_sock *req_unhash,
 815                                           bool *own_req)
 816 {
 817         struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk);
 818         struct mptcp_subflow_request_sock *subflow_req;
 819         struct mptcp_options_received mp_opt;
 820         bool fallback, fallback_is_fatal;
 821         enum sk_rst_reason reason;
 822         struct mptcp_sock *owner;
 823         struct sock *child;
 824
 825         pr_debug("listener=%p, req=%p, conn=%p\n", listener, req, listener->conn);
 826
 827         /* After child creation we must look for MPC even when options
 828          * are not parsed
 829          */
 830         mp_opt.suboptions = 0;
 831
 832         /* hopefully temporary handling for MP_JOIN+syncookie */
 833         subflow_req = mptcp_subflow_rsk(req);
 834         fallback_is_fatal = tcp_rsk(req)->is_mptcp && subflow_req->mp_join;
 835         fallback = !tcp_rsk(req)->is_mptcp;
 836         if (fallback)
 837                 goto create_child;
 838
 839         /* if the sk is MP_CAPABLE, we try to fetch the client key */
 840         if (subflow_req->mp_capable) {
 841                 /* we can receive and accept an in-window, out-of-order pkt,
 842                  * which may not carry the MP_CAPABLE opt even on mptcp enabled
 843                  * paths: always try to extract the peer key, and fallback
 844                  * for packets missing it.
 845                  * Even OoO DSS packets coming legitly after dropped or
 846                  * reordered MPC will cause fallback, but we don't have other
 847                  * options.
 848                  */
 849                 mptcp_get_options(skb, &mp_opt);
 850                 if (!(mp_opt.suboptions &
 851                       (OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_ACK)))
 852                         fallback = true;
 853
 854         } else if (subflow_req->mp_join) {
 855                 mptcp_get_options(skb, &mp_opt);
 856                 if (!(mp_opt.suboptions & OPTION_MPTCP_MPJ_ACK) ||
 857                     !subflow_hmac_valid(req, &mp_opt) ||
 858                     !mptcp_can_accept_new_subflow(subflow_req->msk)) {
 859                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKMAC);
 860                         fallback = true;
 861                 }
 862         }
 863
 864 create_child:
 865         child = listener->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
 866                                                      req_unhash, own_req);
 867
 868         if (child && *own_req) {
 869                 struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);
 870
 871                 tcp_rsk(req)->drop_req = false;
 872
 873                 /* we need to fallback on ctx allocation failure and on pre-reqs
 874                  * checking above. In the latter scenario we additionally need
 875                  * to reset the context to non MPTCP status.
 876                  */
 877                 if (!ctx || fallback) {
 878                         if (fallback_is_fatal) {
 879                                 subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
 880                                 goto dispose_child;
 881                         }
 882                         goto fallback;
 883                 }
 884
 885                 /* ssk inherits options of listener sk */
 886                 ctx->setsockopt_seq = listener->setsockopt_seq;
 887
 888                 if (ctx->mp_capable) {
 889                         ctx->conn = mptcp_sk_clone_init(listener->conn, &mp_opt, child, req);
 890                         if (!ctx->conn)
 891                                 goto fallback;
 892
 893                         ctx->subflow_id = 1;
 894                         owner = mptcp_sk(ctx->conn);
 895                         mptcp_pm_new_connection(owner, child, 1);
 896
 897                         /* with OoO packets we can reach here without ingress
 898                          * mpc option
 899                          */
 900                         if (mp_opt.suboptions & OPTION_MPTCP_MPC_ACK) {
 901                                 mptcp_pm_fully_established(owner, child);
 902                                 ctx->pm_notified = 1;
 903                         }
 904                 } else if (ctx->mp_join) {
 905                         owner = subflow_req->msk;
 906                         if (!owner) {
 907                                 subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
 908                                 goto dispose_child;
 909                         }
 910
 911                         /* move the msk reference ownership to the subflow */
 912                         subflow_req->msk = NULL;
 913                         ctx->conn = (struct sock *)owner;
 914
 915                         if (subflow_use_different_sport(owner, sk)) {
 916                                 pr_debug("ack inet_sport=%d %d\n",
 917                                          ntohs(inet_sk(sk)->inet_sport),
 918                                          ntohs(inet_sk((struct sock *)owner)->inet_sport));
 919                                 if (!mptcp_pm_sport_in_anno_list(owner, sk)) {
 920                                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTACKRX);
 921                                         subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
 922                                         goto dispose_child;
 923                                 }
 924                                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTACKRX);
 925                         }
 926
 927                         if (!mptcp_finish_join(child)) {
 928                                 struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(child);
 929
 930                                 subflow_add_reset_reason(skb, subflow->reset_reason);
 931                                 goto dispose_child;
 932                         }
 933
 934                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKRX);
 935                         tcp_rsk(req)->drop_req = true;
 936                 }
 937         }
 938
 939         /* check for expected invariant - should never trigger, just help
 940          * catching earlier subtle bugs
 941          */
 942         WARN_ON_ONCE(child && *own_req && tcp_sk(child)->is_mptcp &&
 943                      (!mptcp_subflow_ctx(child) ||
 944                       !mptcp_subflow_ctx(child)->conn));
 945         return child;
 946
 947 dispose_child:
 948         mptcp_subflow_drop_ctx(child);
 949         tcp_rsk(req)->drop_req = true;
 950         inet_csk_prepare_for_destroy_sock(child);
 951         tcp_done(child);
 952         reason = mptcp_get_rst_reason(skb);
 953         req->rsk_ops->send_reset(sk, skb, reason);
 954
 955         /* The last child reference will be released by the caller */
 956         return child;
 957
 958 fallback:
 959         if (fallback)
 960                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
 961         mptcp_subflow_drop_ctx(child);
 962         return child;
 963 }
 964
 965 static struct inet_connection_sock_af_ops subflow_specific __ro_after_init;
 966 static struct proto tcp_prot_override __ro_after_init;
 967
 968 enum mapping_status {
 969         MAPPING_OK,
 970         MAPPING_INVALID,
 971         MAPPING_EMPTY,
 972         MAPPING_DATA_FIN,
 973         MAPPING_DUMMY,
 974         MAPPING_BAD_CSUM,
 975         MAPPING_NODSS
 976 };
 977
 978 static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
 979 {
 980         pr_debug("Bad mapping: ssn=%d map_seq=%d map_data_len=%d\n",
 981                  ssn, subflow->map_subflow_seq, subflow->map_data_len);
 982 }
 983
 984 static bool skb_is_fully_mapped(struct sock *ssk, struct sk_buff *skb)
 985 {
 986         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 987         unsigned int skb_consumed;
 988
 989         skb_consumed = tcp_sk(ssk)->copied_seq - TCP_SKB_CB(skb)->seq;
 990         if (unlikely(skb_consumed >= skb->len)) {
 991                 DEBUG_NET_WARN_ON_ONCE(1);
 992                 return true;
 993         }
 994
 995         return skb->len - skb_consumed <= subflow->map_data_len -
 996                                           mptcp_subflow_get_map_offset(subflow);
 997 }
 998
 999 static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
1000 {
1001         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1002         u32 ssn = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
1003
1004         if (unlikely(before(ssn, subflow->map_subflow_seq))) {
1005                 /* Mapping covers data later in the subflow stream,
1006                  * currently unsupported.
1007                  */
1008                 dbg_bad_map(subflow, ssn);
1009                 return false;
1010         }
1011         if (unlikely(!before(ssn, subflow->map_subflow_seq +
1012                                   subflow->map_data_len))) {
1013                 /* Mapping does covers past subflow data, invalid */
1014                 dbg_bad_map(subflow, ssn);
1015                 return false;
1016         }
1017         return true;
1018 }
1019
1020 static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *skb,
1021                                               bool csum_reqd)
1022 {
1023         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1024         u32 offset, seq, delta;
1025         __sum16 csum;
1026         int len;
1027
1028         if (!csum_reqd)
1029                 return MAPPING_OK;
1030
1031         /* mapping already validated on previous traversal */
1032         if (subflow->map_csum_len == subflow->map_data_len)
1033                 return MAPPING_OK;
1034
1035         /* traverse the receive queue, ensuring it contains a full
1036          * DSS mapping and accumulating the related csum.
1037          * Preserve the accoumlate csum across multiple calls, to compute
1038          * the csum only once
1039          */
1040         delta = subflow->map_data_len - subflow->map_csum_len;
1041         for (;;) {
1042                 seq = tcp_sk(ssk)->copied_seq + subflow->map_csum_len;
1043                 offset = seq - TCP_SKB_CB(skb)->seq;
1044
1045                 /* if the current skb has not been accounted yet, csum its contents
1046                  * up to the amount covered by the current DSS
1047                  */
1048                 if (offset < skb->len) {
1049                         __wsum csum;
1050
1051                         len = min(skb->len - offset, delta);
1052                         csum = skb_checksum(skb, offset, len, 0);
1053                         subflow->map_data_csum = csum_block_add(subflow->map_data_csum, csum,
1054                                                                 subflow->map_csum_len);
1055
1056                         delta -= len;
1057                         subflow->map_csum_len += len;
1058                 }
1059                 if (delta == 0)
1060                         break;
1061
1062                 if (skb_queue_is_last(&ssk->sk_receive_queue, skb)) {
1063                         /* if this subflow is closed, the partial mapping
1064                          * will be never completed; flush the pending skbs, so
1065                          * that subflow_sched_work_if_closed() can kick in
1066                          */
1067                         if (unlikely(ssk->sk_state == TCP_CLOSE))
1068                                 while ((skb = skb_peek(&ssk->sk_receive_queue)))
1069                                         sk_eat_skb(ssk, skb);
1070
1071                         /* not enough data to validate the csum */
1072                         return MAPPING_EMPTY;
1073                 }
1074
1075                 /* the DSS mapping for next skbs will be validated later,
1076                  * when a get_mapping_status call will process such skb
1077                  */
1078                 skb = skb->next;
1079         }
1080
1081         /* note that 'map_data_len' accounts only for the carried data, does
1082          * not include the eventual seq increment due to the data fin,
1083          * while the pseudo header requires the original DSS data len,
1084          * including that
1085          */
1086         csum = __mptcp_make_csum(subflow->map_seq,
1087                                  subflow->map_subflow_seq,
1088                                  subflow->map_data_len + subflow->map_data_fin,
1089                                  subflow->map_data_csum);
1090         if (unlikely(csum)) {
1091                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
1092                 return MAPPING_BAD_CSUM;
1093         }
1094
1095         subflow->valid_csum_seen = 1;
1096         return MAPPING_OK;
1097 }
1098
1099 static enum mapping_status get_mapping_status(struct sock *ssk,
1100                                               struct mptcp_sock *msk)
1101 {
1102         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1103         bool csum_reqd = READ_ONCE(msk->csum_enabled);
1104         struct mptcp_ext *mpext;
1105         struct sk_buff *skb;
1106         u16 data_len;
1107         u64 map_seq;
1108
1109         skb = skb_peek(&ssk->sk_receive_queue);
1110         if (!skb)
1111                 return MAPPING_EMPTY;
1112
1113         if (mptcp_check_fallback(ssk))
1114                 return MAPPING_DUMMY;
1115
1116         mpext = mptcp_get_ext(skb);
1117         if (!mpext || !mpext->use_map) {
1118                 if (!subflow->map_valid && !skb->len) {
1119                         /* the TCP stack deliver 0 len FIN pkt to the receive
1120                          * queue, that is the only 0len pkts ever expected here,
1121                          * and we can admit no mapping only for 0 len pkts
1122                          */
1123                         if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1124                                 WARN_ONCE(1, "0len seq %d:%d flags %x",
1125                                           TCP_SKB_CB(skb)->seq,
1126                                           TCP_SKB_CB(skb)->end_seq,
1127                                           TCP_SKB_CB(skb)->tcp_flags);
1128                         sk_eat_skb(ssk, skb);
1129                         return MAPPING_EMPTY;
1130                 }
1131
1132                 /* If the required DSS has likely been dropped by a middlebox */
1133                 if (!subflow->map_valid)
1134                         return MAPPING_NODSS;
1135
1136                 goto validate_seq;
1137         }
1138
1139         trace_get_mapping_status(mpext);
1140
1141         data_len = mpext->data_len;
1142         if (data_len == 0) {
1143                 pr_debug("infinite mapping received\n");
1144                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX);
1145                 subflow->map_data_len = 0;
1146                 return MAPPING_INVALID;
1147         }
1148
1149         if (mpext->data_fin == 1) {
1150                 u64 data_fin_seq;
1151
1152                 if (data_len == 1) {
1153                         bool updated = mptcp_update_rcv_data_fin(msk, mpext->data_seq,
1154                                                                  mpext->dsn64);
1155                         pr_debug("DATA_FIN with no payload seq=%llu\n", mpext->data_seq);
1156                         if (subflow->map_valid) {
1157                                 /* A DATA_FIN might arrive in a DSS
1158                                  * option before the previous mapping
1159                                  * has been fully consumed. Continue
1160                                  * handling the existing mapping.
1161                                  */
1162                                 skb_ext_del(skb, SKB_EXT_MPTCP);
1163                                 return MAPPING_OK;
1164                         }
1165
1166                         if (updated)
1167                                 mptcp_schedule_work((struct sock *)msk);
1168
1169                         return MAPPING_DATA_FIN;
1170                 }
1171
1172                 data_fin_seq = mpext->data_seq + data_len - 1;
1173
1174                 /* If mpext->data_seq is a 32-bit value, data_fin_seq must also
1175                  * be limited to 32 bits.
1176                  */
1177                 if (!mpext->dsn64)
1178                         data_fin_seq &= GENMASK_ULL(31, 0);
1179
1180                 mptcp_update_rcv_data_fin(msk, data_fin_seq, mpext->dsn64);
1181                 pr_debug("DATA_FIN with mapping seq=%llu dsn64=%d\n",
1182                          data_fin_seq, mpext->dsn64);
1183
1184                 /* Adjust for DATA_FIN using 1 byte of sequence space */
1185                 data_len--;
1186         }
1187
1188         map_seq = mptcp_expand_seq(READ_ONCE(msk->ack_seq), mpext->data_seq, mpext->dsn64);
1189         WRITE_ONCE(mptcp_sk(subflow->conn)->use_64bit_ack, !!mpext->dsn64);
1190
1191         if (subflow->map_valid) {
1192                 /* Allow replacing only with an identical map */
1193                 if (subflow->map_seq == map_seq &&
1194                     subflow->map_subflow_seq == mpext->subflow_seq &&
1195                     subflow->map_data_len == data_len &&
1196                     subflow->map_csum_reqd == mpext->csum_reqd) {
1197                         skb_ext_del(skb, SKB_EXT_MPTCP);
1198                         goto validate_csum;
1199                 }
1200
1201                 /* If this skb data are fully covered by the current mapping,
1202                  * the new map would need caching, which is not supported
1203                  */
1204                 if (skb_is_fully_mapped(ssk, skb)) {
1205                         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSNOMATCH);
1206                         return MAPPING_INVALID;
1207                 }
1208
1209                 /* will validate the next map after consuming the current one */
1210                 goto validate_csum;
1211         }
1212
1213         subflow->map_seq = map_seq;
1214         subflow->map_subflow_seq = mpext->subflow_seq;
1215         subflow->map_data_len = data_len;
1216         subflow->map_valid = 1;
1217         subflow->map_data_fin = mpext->data_fin;
1218         subflow->mpc_map = mpext->mpc_map;
1219         subflow->map_csum_reqd = mpext->csum_reqd;
1220         subflow->map_csum_len = 0;
1221         subflow->map_data_csum = csum_unfold(mpext->csum);
1222
1223         /* Cfr RFC 8684 Section 3.3.0 */
1224         if (unlikely(subflow->map_csum_reqd != csum_reqd))
1225                 return MAPPING_INVALID;
1226
1227         pr_debug("new map seq=%llu subflow_seq=%u data_len=%u csum=%d:%u\n",
1228                  subflow->map_seq, subflow->map_subflow_seq,
1229                  subflow->map_data_len, subflow->map_csum_reqd,
1230                  subflow->map_data_csum);
1231
1232 validate_seq:
1233         /* we revalidate valid mapping on new skb, because we must ensure
1234          * the current skb is completely covered by the available mapping
1235          */
1236         if (!validate_mapping(ssk, skb)) {
1237                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSTCPMISMATCH);
1238                 return MAPPING_INVALID;
1239         }
1240
1241         skb_ext_del(skb, SKB_EXT_MPTCP);
1242
1243 validate_csum:
1244         return validate_data_csum(ssk, skb, csum_reqd);
1245 }
1246
1247 static void mptcp_subflow_discard_data(struct sock *ssk, struct sk_buff *skb,
1248                                        u64 limit)
1249 {
1250         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1251         bool fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
1252         struct tcp_sock *tp = tcp_sk(ssk);
1253         u32 offset, incr, avail_len;
1254
1255         offset = tp->copied_seq - TCP_SKB_CB(skb)->seq;
1256         if (WARN_ON_ONCE(offset > skb->len))
1257                 goto out;
1258
1259         avail_len = skb->len - offset;
1260         incr = limit >= avail_len ? avail_len + fin : limit;
1261
1262         pr_debug("discarding=%d len=%d offset=%d seq=%d\n", incr, skb->len,
1263                  offset, subflow->map_subflow_seq);
1264         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DUPDATA);
1265         tcp_sk(ssk)->copied_seq += incr;
1266
1267 out:
1268         if (!before(tcp_sk(ssk)->copied_seq, TCP_SKB_CB(skb)->end_seq))
1269                 sk_eat_skb(ssk, skb);
1270         if (mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len)
1271                 subflow->map_valid = 0;
1272 }
1273
1274 /* sched mptcp worker to remove the subflow if no more data is pending */
1275 static void subflow_sched_work_if_closed(struct mptcp_sock *msk, struct sock *ssk)
1276 {
1277         struct sock *sk = (struct sock *)msk;
1278
1279         if (likely(ssk->sk_state != TCP_CLOSE &&
1280                    (ssk->sk_state != TCP_CLOSE_WAIT ||
1281                     inet_sk_state_load(sk) != TCP_ESTABLISHED)))
1282                 return;
1283
1284         if (skb_queue_empty(&ssk->sk_receive_queue) &&
1285             !test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags))
1286                 mptcp_schedule_work(sk);
1287 }
1288
1289 static bool subflow_can_fallback(struct mptcp_subflow_context *subflow)
1290 {
1291         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1292
1293         if (subflow->mp_join)
1294                 return false;
1295         else if (READ_ONCE(msk->csum_enabled))
1296                 return !subflow->valid_csum_seen;
1297         else
1298                 return READ_ONCE(msk->allow_infinite_fallback);
1299 }
1300
1301 static void mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk)
1302 {
1303         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1304         unsigned long fail_tout;
1305
1306         /* graceful failure can happen only on the MPC subflow */
1307         if (WARN_ON_ONCE(ssk != READ_ONCE(msk->first)))
1308                 return;
1309
1310         /* since the close timeout take precedence on the fail one,
1311          * no need to start the latter when the first is already set
1312          */
1313         if (sock_flag((struct sock *)msk, SOCK_DEAD))
1314                 return;
1315
1316         /* we don't need extreme accuracy here, use a zero fail_tout as special
1317          * value meaning no fail timeout at all;
1318          */
1319         fail_tout = jiffies + TCP_RTO_MAX;
1320         if (!fail_tout)
1321                 fail_tout = 1;
1322         WRITE_ONCE(subflow->fail_tout, fail_tout);
1323         tcp_send_ack(ssk);
1324
1325         mptcp_reset_tout_timer(msk, subflow->fail_tout);
1326 }
1327
1328 static bool subflow_check_data_avail(struct sock *ssk)
1329 {
1330         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1331         enum mapping_status status;
1332         struct mptcp_sock *msk;
1333         struct sk_buff *skb;
1334
1335         if (!skb_peek(&ssk->sk_receive_queue))
1336                 WRITE_ONCE(subflow->data_avail, false);
1337         if (subflow->data_avail)
1338                 return true;
1339
1340         msk = mptcp_sk(subflow->conn);
1341         for (;;) {
1342                 u64 ack_seq;
1343                 u64 old_ack;
1344
1345                 status = get_mapping_status(ssk, msk);
1346                 trace_subflow_check_data_avail(status, skb_peek(&ssk->sk_receive_queue));
1347                 if (unlikely(status == MAPPING_INVALID || status == MAPPING_DUMMY ||
1348                              status == MAPPING_BAD_CSUM || status == MAPPING_NODSS))
1349                         goto fallback;
1350
1351                 if (status != MAPPING_OK)
1352                         goto no_data;
1353
1354                 skb = skb_peek(&ssk->sk_receive_queue);
1355                 if (WARN_ON_ONCE(!skb))
1356                         goto no_data;
1357
1358                 if (unlikely(!READ_ONCE(msk->can_ack)))
1359                         goto fallback;
1360
1361                 old_ack = READ_ONCE(msk->ack_seq);
1362                 ack_seq = mptcp_subflow_get_mapped_dsn(subflow);
1363                 pr_debug("msk ack_seq=%llx subflow ack_seq=%llx\n", old_ack,
1364                          ack_seq);
1365                 if (unlikely(before64(ack_seq, old_ack))) {
1366                         mptcp_subflow_discard_data(ssk, skb, old_ack - ack_seq);
1367                         continue;
1368                 }
1369
1370                 WRITE_ONCE(subflow->data_avail, true);
1371                 break;
1372         }
1373         return true;
1374
1375 no_data:
1376         subflow_sched_work_if_closed(msk, ssk);
1377         return false;
1378
1379 fallback:
1380         if (!__mptcp_check_fallback(msk)) {
1381                 /* RFC 8684 section 3.7. */
1382                 if (status == MAPPING_BAD_CSUM &&
1383                     (subflow->mp_join || subflow->valid_csum_seen)) {
1384                         subflow->send_mp_fail = 1;
1385
1386                         if (!READ_ONCE(msk->allow_infinite_fallback)) {
1387                                 subflow->reset_transient = 0;
1388                                 subflow->reset_reason = MPTCP_RST_EMIDDLEBOX;
1389                                 goto reset;
1390                         }
1391                         mptcp_subflow_fail(msk, ssk);
1392                         WRITE_ONCE(subflow->data_avail, true);
1393                         return true;
1394                 }
1395
1396                 if (!subflow_can_fallback(subflow) && subflow->map_data_len) {
1397                         /* fatal protocol error, close the socket.
1398                          * subflow_error_report() will introduce the appropriate barriers
1399                          */
1400                         subflow->reset_transient = 0;
1401                         subflow->reset_reason = status == MAPPING_NODSS ?
1402                                                 MPTCP_RST_EMIDDLEBOX :
1403                                                 MPTCP_RST_EMPTCP;
1404
1405 reset:
1406                         WRITE_ONCE(ssk->sk_err, EBADMSG);
1407                         tcp_set_state(ssk, TCP_CLOSE);
1408                         while ((skb = skb_peek(&ssk->sk_receive_queue)))
1409                                 sk_eat_skb(ssk, skb);
1410                         mptcp_send_active_reset_reason(ssk);
1411                         WRITE_ONCE(subflow->data_avail, false);
1412                         return false;
1413                 }
1414
1415                 mptcp_do_fallback(ssk);
1416         }
1417
1418         skb = skb_peek(&ssk->sk_receive_queue);
1419         subflow->map_valid = 1;
1420         subflow->map_seq = READ_ONCE(msk->ack_seq);
1421         subflow->map_data_len = skb->len;
1422         subflow->map_subflow_seq = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
1423         WRITE_ONCE(subflow->data_avail, true);
1424         return true;
1425 }
1426
1427 bool mptcp_subflow_data_available(struct sock *sk)
1428 {
1429         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1430
1431         /* check if current mapping is still valid */
1432         if (subflow->map_valid &&
1433             mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len) {
1434                 subflow->map_valid = 0;
1435                 WRITE_ONCE(subflow->data_avail, false);
1436
1437                 pr_debug("Done with mapping: seq=%u data_len=%u\n",
1438                          subflow->map_subflow_seq,
1439                          subflow->map_data_len);
1440         }
1441
1442         return subflow_check_data_avail(sk);
1443 }
1444
1445 /* If ssk has an mptcp parent socket, use the mptcp rcvbuf occupancy,
1446  * not the ssk one.
1447  *
1448  * In mptcp, rwin is about the mptcp-level connection data.
1449  *
1450  * Data that is still on the ssk rx queue can thus be ignored,
1451  * as far as mptcp peer is concerned that data is still inflight.
1452  * DSS ACK is updated when skb is moved to the mptcp rx queue.
1453  */
1454 void mptcp_space(const struct sock *ssk, int *space, int *full_space)
1455 {
1456         const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1457         const struct sock *sk = subflow->conn;
1458
1459         *space = __mptcp_space(sk);
1460         *full_space = mptcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf));
1461 }
1462
1463 static void subflow_error_report(struct sock *ssk)
1464 {
1465         struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
1466
1467         /* bail early if this is a no-op, so that we avoid introducing a
1468          * problematic lockdep dependency between TCP accept queue lock
1469          * and msk socket spinlock
1470          */
1471         if (!sk->sk_socket)
1472                 return;
1473
1474         mptcp_data_lock(sk);
1475         if (!sock_owned_by_user(sk))
1476                 __mptcp_error_report(sk);
1477         else
1478                 __set_bit(MPTCP_ERROR_REPORT,  &mptcp_sk(sk)->cb_flags);
1479         mptcp_data_unlock(sk);
1480 }
1481
1482 static void subflow_data_ready(struct sock *sk)
1483 {
1484         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1485         u16 state = 1 << inet_sk_state_load(sk);
1486         struct sock *parent = subflow->conn;
1487         struct mptcp_sock *msk;
1488
1489         trace_sk_data_ready(sk);
1490
1491         msk = mptcp_sk(parent);
1492         if (state & TCPF_LISTEN) {
1493                 /* MPJ subflow are removed from accept queue before reaching here,
1494                  * avoid stray wakeups
1495                  */
1496                 if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue))
1497                         return;
1498
1499                 parent->sk_data_ready(parent);
1500                 return;
1501         }
1502
1503         WARN_ON_ONCE(!__mptcp_check_fallback(msk) && !subflow->mp_capable &&
1504                      !subflow->mp_join && !(state & TCPF_CLOSE));
1505
1506         if (mptcp_subflow_data_available(sk)) {
1507                 mptcp_data_ready(parent, sk);
1508
1509                 /* subflow-level lowat test are not relevant.
1510                  * respect the msk-level threshold eventually mandating an immediate ack
1511                  */
1512                 if (mptcp_data_avail(msk) < parent->sk_rcvlowat &&
1513                     (tcp_sk(sk)->rcv_nxt - tcp_sk(sk)->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss)
1514                         inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
1515         } else if (unlikely(sk->sk_err)) {
1516                 subflow_error_report(sk);
1517         }
1518 }
1519
1520 static void subflow_write_space(struct sock *ssk)
1521 {
1522         struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
1523
1524         mptcp_propagate_sndbuf(sk, ssk);
1525         mptcp_write_space(sk);
1526 }
1527
1528 static const struct inet_connection_sock_af_ops *
1529 subflow_default_af_ops(struct sock *sk)
1530 {
1531 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1532         if (sk->sk_family == AF_INET6)
1533                 return &subflow_v6_specific;
1534 #endif
1535         return &subflow_specific;
1536 }
1537
1538 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1539 void mptcpv6_handle_mapped(struct sock *sk, bool mapped)
1540 {
1541         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1542         struct inet_connection_sock *icsk = inet_csk(sk);
1543         const struct inet_connection_sock_af_ops *target;
1544
1545         target = mapped ? &subflow_v6m_specific : subflow_default_af_ops(sk);
1546
1547         pr_debug("subflow=%p family=%d ops=%p target=%p mapped=%d\n",
1548                  subflow, sk->sk_family, icsk->icsk_af_ops, target, mapped);
1549
1550         if (likely(icsk->icsk_af_ops == target))
1551                 return;
1552
1553         subflow->icsk_af_ops = icsk->icsk_af_ops;
1554         icsk->icsk_af_ops = target;
1555 }
1556 #endif
1557
1558 void mptcp_info2sockaddr(const struct mptcp_addr_info *info,
1559                          struct sockaddr_storage *addr,
1560                          unsigned short family)
1561 {
1562         memset(addr, 0, sizeof(*addr));
1563         addr->ss_family = family;
1564         if (addr->ss_family == AF_INET) {
1565                 struct sockaddr_in *in_addr = (struct sockaddr_in *)addr;
1566
1567                 if (info->family == AF_INET)
1568                         in_addr->sin_addr = info->addr;
1569 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1570                 else if (ipv6_addr_v4mapped(&info->addr6))
1571                         in_addr->sin_addr.s_addr = info->addr6.s6_addr32[3];
1572 #endif
1573                 in_addr->sin_port = info->port;
1574         }
1575 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1576         else if (addr->ss_family == AF_INET6) {
1577                 struct sockaddr_in6 *in6_addr = (struct sockaddr_in6 *)addr;
1578
1579                 if (info->family == AF_INET)
1580                         ipv6_addr_set_v4mapped(info->addr.s_addr,
1581                                                &in6_addr->sin6_addr);
1582                 else
1583                         in6_addr->sin6_addr = info->addr6;
1584                 in6_addr->sin6_port = info->port;
1585         }
1586 #endif
1587 }
1588
1589 int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_pm_local *local,
1590                             const struct mptcp_addr_info *remote)
1591 {
1592         struct mptcp_sock *msk = mptcp_sk(sk);
1593         struct mptcp_subflow_context *subflow;
1594         int local_id = local->addr.id;
1595         struct sockaddr_storage addr;
1596         int remote_id = remote->id;
1597         int err = -ENOTCONN;
1598         struct socket *sf;
1599         struct sock *ssk;
1600         u32 remote_token;
1601         int addrlen;
1602
1603         /* The userspace PM sent the request too early? */
1604         if (!mptcp_is_fully_established(sk))
1605                 goto err_out;
1606
1607         err = mptcp_subflow_create_socket(sk, local->addr.family, &sf);
1608         if (err) {
1609                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTXCREATSKERR);
1610                 pr_debug("msk=%p local=%d remote=%d create sock error: %d\n",
1611                          msk, local_id, remote_id, err);
1612                 goto err_out;
1613         }
1614
1615         ssk = sf->sk;
1616         subflow = mptcp_subflow_ctx(ssk);
1617         do {
1618                 get_random_bytes(&subflow->local_nonce, sizeof(u32));
1619         } while (!subflow->local_nonce);
1620
1621         /* if 'IPADDRANY', the ID will be set later, after the routing */
1622         if (local->addr.family == AF_INET) {
1623                 if (!local->addr.addr.s_addr)
1624                         local_id = -1;
1625 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1626         } else if (sk->sk_family == AF_INET6) {
1627                 if (ipv6_addr_any(&local->addr.addr6))
1628                         local_id = -1;
1629 #endif
1630         }
1631
1632         if (local_id >= 0)
1633                 subflow_set_local_id(subflow, local_id);
1634
1635         subflow->remote_key_valid = 1;
1636         subflow->remote_key = READ_ONCE(msk->remote_key);
1637         subflow->local_key = READ_ONCE(msk->local_key);
1638         subflow->token = msk->token;
1639         mptcp_info2sockaddr(&local->addr, &addr, ssk->sk_family);
1640
1641         addrlen = sizeof(struct sockaddr_in);
1642 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1643         if (addr.ss_family == AF_INET6)
1644                 addrlen = sizeof(struct sockaddr_in6);
1645 #endif
1646         ssk->sk_bound_dev_if = local->ifindex;
1647         err = kernel_bind(sf, (struct sockaddr *)&addr, addrlen);
1648         if (err) {
1649                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTXBINDERR);
1650                 pr_debug("msk=%p local=%d remote=%d bind error: %d\n",
1651                          msk, local_id, remote_id, err);
1652                 goto failed;
1653         }
1654
1655         mptcp_crypto_key_sha(subflow->remote_key, &remote_token, NULL);
1656         pr_debug("msk=%p remote_token=%u local_id=%d remote_id=%d\n", msk,
1657                  remote_token, local_id, remote_id);
1658         subflow->remote_token = remote_token;
1659         WRITE_ONCE(subflow->remote_id, remote_id);
1660         subflow->request_join = 1;
1661         subflow->request_bkup = !!(local->flags & MPTCP_PM_ADDR_FLAG_BACKUP);
1662         subflow->subflow_id = msk->subflow_id++;
1663         mptcp_info2sockaddr(remote, &addr, ssk->sk_family);
1664
1665         sock_hold(ssk);
1666         list_add_tail(&subflow->node, &msk->conn_list);
1667         err = kernel_connect(sf, (struct sockaddr *)&addr, addrlen, O_NONBLOCK);
1668         if (err && err != -EINPROGRESS) {
1669                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTXCONNECTERR);
1670                 pr_debug("msk=%p local=%d remote=%d connect error: %d\n",
1671                          msk, local_id, remote_id, err);
1672                 goto failed_unlink;
1673         }
1674
1675         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNTX);
1676
1677         /* discard the subflow socket */
1678         mptcp_sock_graft(ssk, sk->sk_socket);
1679         iput(SOCK_INODE(sf));
1680         WRITE_ONCE(msk->allow_infinite_fallback, false);
1681         mptcp_stop_tout_timer(sk);
1682         return 0;
1683
1684 failed_unlink:
1685         list_del(&subflow->node);
1686         sock_put(mptcp_subflow_tcp_sock(subflow));
1687
1688 failed:
1689         subflow->disposable = 1;
1690         sock_release(sf);
1691
1692 err_out:
1693         /* we account subflows before the creation, and this failures will not
1694          * be caught by sk_state_change()
1695          */
1696         mptcp_pm_close_subflow(msk);
1697         return err;
1698 }
1699
1700 static void mptcp_attach_cgroup(struct sock *parent, struct sock *child)
1701 {
1702 #ifdef CONFIG_SOCK_CGROUP_DATA
1703         struct sock_cgroup_data *parent_skcd = &parent->sk_cgrp_data,
1704                                 *child_skcd = &child->sk_cgrp_data;
1705
1706         /* only the additional subflows created by kworkers have to be modified */
1707         if (cgroup_id(sock_cgroup_ptr(parent_skcd)) !=
1708             cgroup_id(sock_cgroup_ptr(child_skcd))) {
1709 #ifdef CONFIG_MEMCG
1710                 struct mem_cgroup *memcg = parent->sk_memcg;
1711
1712                 mem_cgroup_sk_free(child);
1713                 if (memcg && css_tryget(&memcg->css))
1714                         child->sk_memcg = memcg;
1715 #endif /* CONFIG_MEMCG */
1716
1717                 cgroup_sk_free(child_skcd);
1718                 *child_skcd = *parent_skcd;
1719                 cgroup_sk_clone(child_skcd);
1720         }
1721 #endif /* CONFIG_SOCK_CGROUP_DATA */
1722 }
1723
1724 static void mptcp_subflow_ops_override(struct sock *ssk)
1725 {
1726 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1727         if (ssk->sk_prot == &tcpv6_prot)
1728                 ssk->sk_prot = &tcpv6_prot_override;
1729         else
1730 #endif
1731                 ssk->sk_prot = &tcp_prot_override;
1732 }
1733
1734 static void mptcp_subflow_ops_undo_override(struct sock *ssk)
1735 {
1736 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1737         if (ssk->sk_prot == &tcpv6_prot_override)
1738                 ssk->sk_prot = &tcpv6_prot;
1739         else
1740 #endif
1741                 ssk->sk_prot = &tcp_prot;
1742 }
1743
1744 int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
1745                                 struct socket **new_sock)
1746 {
1747         struct mptcp_subflow_context *subflow;
1748         struct net *net = sock_net(sk);
1749         struct socket *sf;
1750         int err;
1751
1752         /* un-accepted server sockets can reach here - on bad configuration
1753          * bail early to avoid greater trouble later
1754          */
1755         if (unlikely(!sk->sk_socket))
1756                 return -EINVAL;
1757
1758         err = sock_create_kern(net, family, SOCK_STREAM, IPPROTO_TCP, &sf);
1759         if (err)
1760                 return err;
1761
1762         lock_sock_nested(sf->sk, SINGLE_DEPTH_NESTING);
1763
1764         err = security_mptcp_add_subflow(sk, sf->sk);
1765         if (err)
1766                 goto err_free;
1767
1768         /* the newly created socket has to be in the same cgroup as its parent */
1769         mptcp_attach_cgroup(sk, sf->sk);
1770
1771         /* kernel sockets do not by default acquire net ref, but TCP timer
1772          * needs it.
1773          * Update ns_tracker to current stack trace and refcounted tracker.
1774          */
1775         __netns_tracker_free(net, &sf->sk->ns_tracker, false);
1776         sf->sk->sk_net_refcnt = 1;
1777         get_net_track(net, &sf->sk->ns_tracker, GFP_KERNEL);
1778         sock_inuse_add(net, 1);
1779         err = tcp_set_ulp(sf->sk, "mptcp");
1780         if (err)
1781                 goto err_free;
1782
1783         mptcp_sockopt_sync_locked(mptcp_sk(sk), sf->sk);
1784         release_sock(sf->sk);
1785
1786         /* the newly created socket really belongs to the owning MPTCP
1787          * socket, even if for additional subflows the allocation is performed
1788          * by a kernel workqueue. Adjust inode references, so that the
1789          * procfs/diag interfaces really show this one belonging to the correct
1790          * user.
1791          */
1792         SOCK_INODE(sf)->i_ino = SOCK_INODE(sk->sk_socket)->i_ino;
1793         SOCK_INODE(sf)->i_uid = SOCK_INODE(sk->sk_socket)->i_uid;
1794         SOCK_INODE(sf)->i_gid = SOCK_INODE(sk->sk_socket)->i_gid;
1795
1796         subflow = mptcp_subflow_ctx(sf->sk);
1797         pr_debug("subflow=%p\n", subflow);
1798
1799         *new_sock = sf;
1800         sock_hold(sk);
1801         subflow->conn = sk;
1802         mptcp_subflow_ops_override(sf->sk);
1803
1804         return 0;
1805
1806 err_free:
1807         release_sock(sf->sk);
1808         sock_release(sf);
1809         return err;
1810 }
1811
1812 static struct mptcp_subflow_context *subflow_create_ctx(struct sock *sk,
1813                                                         gfp_t priority)
1814 {
1815         struct inet_connection_sock *icsk = inet_csk(sk);
1816         struct mptcp_subflow_context *ctx;
1817
1818         ctx = kzalloc(sizeof(*ctx), priority);
1819         if (!ctx)
1820                 return NULL;
1821
1822         rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
1823         INIT_LIST_HEAD(&ctx->node);
1824         INIT_LIST_HEAD(&ctx->delegated_node);
1825
1826         pr_debug("subflow=%p\n", ctx);
1827
1828         ctx->tcp_sock = sk;
1829         WRITE_ONCE(ctx->local_id, -1);
1830
1831         return ctx;
1832 }
1833
1834 static void __subflow_state_change(struct sock *sk)
1835 {
1836         struct socket_wq *wq;
1837
1838         rcu_read_lock();
1839         wq = rcu_dereference(sk->sk_wq);
1840         if (skwq_has_sleeper(wq))
1841                 wake_up_interruptible_all(&wq->wait);
1842         rcu_read_unlock();
1843 }
1844
1845 static bool subflow_is_done(const struct sock *sk)
1846 {
1847         return sk->sk_shutdown & RCV_SHUTDOWN || sk->sk_state == TCP_CLOSE;
1848 }
1849
1850 static void subflow_state_change(struct sock *sk)
1851 {
1852         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1853         struct sock *parent = subflow->conn;
1854         struct mptcp_sock *msk;
1855
1856         __subflow_state_change(sk);
1857
1858         msk = mptcp_sk(parent);
1859         if (subflow_simultaneous_connect(sk)) {
1860                 mptcp_do_fallback(sk);
1861                 pr_fallback(msk);
1862                 subflow->conn_finished = 1;
1863                 mptcp_propagate_state(parent, sk, subflow, NULL);
1864         }
1865
1866         /* as recvmsg() does not acquire the subflow socket for ssk selection
1867          * a fin packet carrying a DSS can be unnoticed if we don't trigger
1868          * the data available machinery here.
1869          */
1870         if (mptcp_subflow_data_available(sk))
1871                 mptcp_data_ready(parent, sk);
1872         else if (unlikely(sk->sk_err))
1873                 subflow_error_report(sk);
1874
1875         subflow_sched_work_if_closed(mptcp_sk(parent), sk);
1876
1877         /* when the fallback subflow closes the rx side, trigger a 'dummy'
1878          * ingress data fin, so that the msk state will follow along
1879          */
1880         if (__mptcp_check_fallback(msk) && subflow_is_done(sk) && msk->first == sk &&
1881             mptcp_update_rcv_data_fin(msk, READ_ONCE(msk->ack_seq), true))
1882                 mptcp_schedule_work(parent);
1883 }
1884
1885 void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_ssk)
1886 {
1887         struct request_sock_queue *queue = &inet_csk(listener_ssk)->icsk_accept_queue;
1888         struct request_sock *req, *head, *tail;
1889         struct mptcp_subflow_context *subflow;
1890         struct sock *sk, *ssk;
1891
1892         /* Due to lock dependencies no relevant lock can be acquired under rskq_lock.
1893          * Splice the req list, so that accept() can not reach the pending ssk after
1894          * the listener socket is released below.
1895          */
1896         spin_lock_bh(&queue->rskq_lock);
1897         head = queue->rskq_accept_head;
1898         tail = queue->rskq_accept_tail;
1899         queue->rskq_accept_head = NULL;
1900         queue->rskq_accept_tail = NULL;
1901         spin_unlock_bh(&queue->rskq_lock);
1902
1903         if (!head)
1904                 return;
1905
1906         /* can't acquire the msk socket lock under the subflow one,
1907          * or will cause ABBA deadlock
1908          */
1909         release_sock(listener_ssk);
1910
1911         for (req = head; req; req = req->dl_next) {
1912                 ssk = req->sk;
1913                 if (!sk_is_mptcp(ssk))
1914                         continue;
1915
1916                 subflow = mptcp_subflow_ctx(ssk);
1917                 if (!subflow || !subflow->conn)
1918                         continue;
1919
1920                 sk = subflow->conn;
1921                 sock_hold(sk);
1922
1923                 lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
1924                 __mptcp_unaccepted_force_close(sk);
1925                 release_sock(sk);
1926
1927                 /* lockdep will report a false positive ABBA deadlock
1928                  * between cancel_work_sync and the listener socket.
1929                  * The involved locks belong to different sockets WRT
1930                  * the existing AB chain.
1931                  * Using a per socket key is problematic as key
1932                  * deregistration requires process context and must be
1933                  * performed at socket disposal time, in atomic
1934                  * context.
1935                  * Just tell lockdep to consider the listener socket
1936                  * released here.
1937                  */
1938                 mutex_release(&listener_sk->sk_lock.dep_map, _RET_IP_);
1939                 mptcp_cancel_work(sk);
1940                 mutex_acquire(&listener_sk->sk_lock.dep_map, 0, 0, _RET_IP_);
1941
1942                 sock_put(sk);
1943         }
1944
1945         /* we are still under the listener msk socket lock */
1946         lock_sock_nested(listener_ssk, SINGLE_DEPTH_NESTING);
1947
1948         /* restore the listener queue, to let the TCP code clean it up */
1949         spin_lock_bh(&queue->rskq_lock);
1950         WARN_ON_ONCE(queue->rskq_accept_head);
1951         queue->rskq_accept_head = head;
1952         queue->rskq_accept_tail = tail;
1953         spin_unlock_bh(&queue->rskq_lock);
1954 }
1955
1956 static int subflow_ulp_init(struct sock *sk)
1957 {
1958         struct inet_connection_sock *icsk = inet_csk(sk);
1959         struct mptcp_subflow_context *ctx;
1960         struct tcp_sock *tp = tcp_sk(sk);
1961         int err = 0;
1962
1963         /* disallow attaching ULP to a socket unless it has been
1964          * created with sock_create_kern()
1965          */
1966         if (!sk->sk_kern_sock) {
1967                 err = -EOPNOTSUPP;
1968                 goto out;
1969         }
1970
1971         ctx = subflow_create_ctx(sk, GFP_KERNEL);
1972         if (!ctx) {
1973                 err = -ENOMEM;
1974                 goto out;
1975         }
1976
1977         pr_debug("subflow=%p, family=%d\n", ctx, sk->sk_family);
1978
1979         tp->is_mptcp = 1;
1980         ctx->icsk_af_ops = icsk->icsk_af_ops;
1981         icsk->icsk_af_ops = subflow_default_af_ops(sk);
1982         ctx->tcp_state_change = sk->sk_state_change;
1983         ctx->tcp_error_report = sk->sk_error_report;
1984
1985         WARN_ON_ONCE(sk->sk_data_ready != sock_def_readable);
1986         WARN_ON_ONCE(sk->sk_write_space != sk_stream_write_space);
1987
1988         sk->sk_data_ready = subflow_data_ready;
1989         sk->sk_write_space = subflow_write_space;
1990         sk->sk_state_change = subflow_state_change;
1991         sk->sk_error_report = subflow_error_report;
1992 out:
1993         return err;
1994 }
1995
1996 static void subflow_ulp_release(struct sock *ssk)
1997 {
1998         struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
1999         bool release = true;
2000         struct sock *sk;
2001
2002         if (!ctx)
2003                 return;
2004
2005         sk = ctx->conn;
2006         if (sk) {
2007                 /* if the msk has been orphaned, keep the ctx
2008                  * alive, will be freed by __mptcp_close_ssk(),
2009                  * when the subflow is still unaccepted
2010                  */
2011                 release = ctx->disposable || list_empty(&ctx->node);
2012
2013                 /* inet_child_forget() does not call sk_state_change(),
2014                  * explicitly trigger the socket close machinery
2015                  */
2016                 if (!release && !test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW,
2017                                                   &mptcp_sk(sk)->flags))
2018                         mptcp_schedule_work(sk);
2019                 sock_put(sk);
2020         }
2021
2022         mptcp_subflow_ops_undo_override(ssk);
2023         if (release)
2024                 kfree_rcu(ctx, rcu);
2025 }
2026
2027 static void subflow_ulp_clone(const struct request_sock *req,
2028                               struct sock *newsk,
2029                               const gfp_t priority)
2030 {
2031         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
2032         struct mptcp_subflow_context *old_ctx = mptcp_subflow_ctx(newsk);
2033         struct mptcp_subflow_context *new_ctx;
2034
2035         if (!tcp_rsk(req)->is_mptcp ||
2036             (!subflow_req->mp_capable && !subflow_req->mp_join)) {
2037                 subflow_ulp_fallback(newsk, old_ctx);
2038                 return;
2039         }
2040
2041         new_ctx = subflow_create_ctx(newsk, priority);
2042         if (!new_ctx) {
2043                 subflow_ulp_fallback(newsk, old_ctx);
2044                 return;
2045         }
2046
2047         new_ctx->conn_finished = 1;
2048         new_ctx->icsk_af_ops = old_ctx->icsk_af_ops;
2049         new_ctx->tcp_state_change = old_ctx->tcp_state_change;
2050         new_ctx->tcp_error_report = old_ctx->tcp_error_report;
2051         new_ctx->rel_write_seq = 1;
2052
2053         if (subflow_req->mp_capable) {
2054                 /* see comments in subflow_syn_recv_sock(), MPTCP connection
2055                  * is fully established only after we receive the remote key
2056                  */
2057                 new_ctx->mp_capable = 1;
2058                 new_ctx->local_key = subflow_req->local_key;
2059                 new_ctx->token = subflow_req->token;
2060                 new_ctx->ssn_offset = subflow_req->ssn_offset;
2061                 new_ctx->idsn = subflow_req->idsn;
2062
2063                 /* this is the first subflow, id is always 0 */
2064                 subflow_set_local_id(new_ctx, 0);
2065         } else if (subflow_req->mp_join) {
2066                 new_ctx->ssn_offset = subflow_req->ssn_offset;
2067                 new_ctx->mp_join = 1;
2068                 WRITE_ONCE(new_ctx->fully_established, true);
2069                 new_ctx->remote_key_valid = 1;
2070                 new_ctx->backup = subflow_req->backup;
2071                 new_ctx->request_bkup = subflow_req->request_bkup;
2072                 WRITE_ONCE(new_ctx->remote_id, subflow_req->remote_id);
2073                 new_ctx->token = subflow_req->token;
2074                 new_ctx->thmac = subflow_req->thmac;
2075
2076                 /* the subflow req id is valid, fetched via subflow_check_req()
2077                  * and subflow_token_join_request()
2078                  */
2079                 subflow_set_local_id(new_ctx, subflow_req->local_id);
2080         }
2081 }
2082
2083 static void tcp_release_cb_override(struct sock *ssk)
2084 {
2085         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
2086         long status;
2087
2088         /* process and clear all the pending actions, but leave the subflow into
2089          * the napi queue. To respect locking, only the same CPU that originated
2090          * the action can touch the list. mptcp_napi_poll will take care of it.
2091          */
2092         status = set_mask_bits(&subflow->delegated_status, MPTCP_DELEGATE_ACTIONS_MASK, 0);
2093         if (status)
2094                 mptcp_subflow_process_delegated(ssk, status);
2095
2096         tcp_release_cb(ssk);
2097 }
2098
2099 static int tcp_abort_override(struct sock *ssk, int err)
2100 {
2101         /* closing a listener subflow requires a great deal of care.
2102          * keep it simple and just prevent such operation
2103          */
2104         if (inet_sk_state_load(ssk) == TCP_LISTEN)
2105                 return -EINVAL;
2106
2107         return tcp_abort(ssk, err);
2108 }
2109
2110 static struct tcp_ulp_ops subflow_ulp_ops __read_mostly = {
2111         .name           = "mptcp",
2112         .owner          = THIS_MODULE,
2113         .init           = subflow_ulp_init,
2114         .release        = subflow_ulp_release,
2115         .clone          = subflow_ulp_clone,
2116 };
2117
2118 static int subflow_ops_init(struct request_sock_ops *subflow_ops)
2119 {
2120         subflow_ops->obj_size = sizeof(struct mptcp_subflow_request_sock);
2121
2122         subflow_ops->slab = kmem_cache_create(subflow_ops->slab_name,
2123                                               subflow_ops->obj_size, 0,
2124                                               SLAB_ACCOUNT |
2125                                               SLAB_TYPESAFE_BY_RCU,
2126                                               NULL);
2127         if (!subflow_ops->slab)
2128                 return -ENOMEM;
2129
2130         return 0;
2131 }
2132
2133 void __init mptcp_subflow_init(void)
2134 {
2135         mptcp_subflow_v4_request_sock_ops = tcp_request_sock_ops;
2136         mptcp_subflow_v4_request_sock_ops.slab_name = "request_sock_subflow_v4";
2137         mptcp_subflow_v4_request_sock_ops.destructor = subflow_v4_req_destructor;
2138
2139         if (subflow_ops_init(&mptcp_subflow_v4_request_sock_ops) != 0)
2140                 panic("MPTCP: failed to init subflow v4 request sock ops\n");
2141
2142         subflow_request_sock_ipv4_ops = tcp_request_sock_ipv4_ops;
2143         subflow_request_sock_ipv4_ops.route_req = subflow_v4_route_req;
2144         subflow_request_sock_ipv4_ops.send_synack = subflow_v4_send_synack;
2145
2146         subflow_specific = ipv4_specific;
2147         subflow_specific.conn_request = subflow_v4_conn_request;
2148         subflow_specific.syn_recv_sock = subflow_syn_recv_sock;
2149         subflow_specific.sk_rx_dst_set = subflow_finish_connect;
2150         subflow_specific.rebuild_header = subflow_rebuild_header;
2151
2152         tcp_prot_override = tcp_prot;
2153         tcp_prot_override.release_cb = tcp_release_cb_override;
2154         tcp_prot_override.diag_destroy = tcp_abort_override;
2155
2156 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
2157         /* In struct mptcp_subflow_request_sock, we assume the TCP request sock
2158          * structures for v4 and v6 have the same size. It should not changed in
2159          * the future but better to make sure to be warned if it is no longer
2160          * the case.
2161          */
2162         BUILD_BUG_ON(sizeof(struct tcp_request_sock) != sizeof(struct tcp6_request_sock));
2163
2164         mptcp_subflow_v6_request_sock_ops = tcp6_request_sock_ops;
2165         mptcp_subflow_v6_request_sock_ops.slab_name = "request_sock_subflow_v6";
2166         mptcp_subflow_v6_request_sock_ops.destructor = subflow_v6_req_destructor;
2167
2168         if (subflow_ops_init(&mptcp_subflow_v6_request_sock_ops) != 0)
2169                 panic("MPTCP: failed to init subflow v6 request sock ops\n");
2170
2171         subflow_request_sock_ipv6_ops = tcp_request_sock_ipv6_ops;
2172         subflow_request_sock_ipv6_ops.route_req = subflow_v6_route_req;
2173         subflow_request_sock_ipv6_ops.send_synack = subflow_v6_send_synack;
2174
2175         subflow_v6_specific = ipv6_specific;
2176         subflow_v6_specific.conn_request = subflow_v6_conn_request;
2177         subflow_v6_specific.syn_recv_sock = subflow_syn_recv_sock;
2178         subflow_v6_specific.sk_rx_dst_set = subflow_finish_connect;
2179         subflow_v6_specific.rebuild_header = subflow_v6_rebuild_header;
2180
2181         subflow_v6m_specific = subflow_v6_specific;
2182         subflow_v6m_specific.queue_xmit = ipv4_specific.queue_xmit;
2183         subflow_v6m_specific.send_check = ipv4_specific.send_check;
2184         subflow_v6m_specific.net_header_len = ipv4_specific.net_header_len;
2185         subflow_v6m_specific.mtu_reduced = ipv4_specific.mtu_reduced;
2186         subflow_v6m_specific.rebuild_header = subflow_rebuild_header;
2187
2188         tcpv6_prot_override = tcpv6_prot;
2189         tcpv6_prot_override.release_cb = tcp_release_cb_override;
2190         tcpv6_prot_override.diag_destroy = tcp_abort_override;
2191 #endif
2192
2193         mptcp_diag_subflow_init(&subflow_ulp_ops);
2194
2195         if (tcp_register_ulp(&subflow_ulp_ops) != 0)
2196                 panic("MPTCP: failed to register subflows to ULP\n");
2197 }