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