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
  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", subflow_req);
  43
  44         if (subflow_req->msk)
  45                 sock_put((struct sock *)subflow_req->msk);
  46
  47         mptcp_token_destroy_request(req);
  48         tcp_request_sock_ops.destructor(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 & OPTIONS_MPTCP_MPC);
 161         opt_mp_join = !!(mp_opt.suboptions & OPTIONS_MPTCP_MPJ);
 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 & OPTIONS_MPTCP_MPC);
 258         opt_mp_join = !!(mp_opt.suboptions & OPTIONS_MPTCP_MPJ);
 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 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 311 static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
 312                                               struct sk_buff *skb,
 313                                               struct flowi *fl,
 314                                               struct request_sock *req)
 315 {
 316         struct dst_entry *dst;
 317         int err;
 318
 319         tcp_rsk(req)->is_mptcp = 1;
 320         subflow_init_req(req, sk);
 321
 322         dst = tcp_request_sock_ipv6_ops.route_req(sk, skb, fl, req);
 323         if (!dst)
 324                 return NULL;
 325
 326         err = subflow_check_req(req, sk, skb);
 327         if (err == 0)
 328                 return dst;
 329
 330         dst_release(dst);
 331         if (!req->syncookie)
 332                 tcp6_request_sock_ops.send_reset(sk, skb);
 333         return NULL;
 334 }
 335 #endif
 336
 337 /* validate received truncated hmac and create hmac for third ACK */
 338 static bool subflow_thmac_valid(struct mptcp_subflow_context *subflow)
 339 {
 340         u8 hmac[SHA256_DIGEST_SIZE];
 341         u64 thmac;
 342
 343         subflow_generate_hmac(subflow->remote_key, subflow->local_key,
 344                               subflow->remote_nonce, subflow->local_nonce,
 345                               hmac);
 346
 347         thmac = get_unaligned_be64(hmac);
 348         pr_debug("subflow=%p, token=%u, thmac=%llu, subflow->thmac=%llu\n",
 349                  subflow, subflow->token, thmac, subflow->thmac);
 350
 351         return thmac == subflow->thmac;
 352 }
 353
 354 void mptcp_subflow_reset(struct sock *ssk)
 355 {
 356         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 357         struct sock *sk = subflow->conn;
 358
 359         /* must hold: tcp_done() could drop last reference on parent */
 360         sock_hold(sk);
 361
 362         tcp_set_state(ssk, TCP_CLOSE);
 363         tcp_send_active_reset(ssk, GFP_ATOMIC);
 364         tcp_done(ssk);
 365         if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags) &&
 366             schedule_work(&mptcp_sk(sk)->work))
 367                 return; /* worker will put sk for us */
 368
 369         sock_put(sk);
 370 }
 371
 372 static bool subflow_use_different_dport(struct mptcp_sock *msk, const struct sock *sk)
 373 {
 374         return inet_sk(sk)->inet_dport != inet_sk((struct sock *)msk)->inet_dport;
 375 }
 376
 377 void __mptcp_set_connected(struct sock *sk)
 378 {
 379         if (sk->sk_state == TCP_SYN_SENT) {
 380                 inet_sk_state_store(sk, TCP_ESTABLISHED);
 381                 sk->sk_state_change(sk);
 382         }
 383 }
 384
 385 static void mptcp_set_connected(struct sock *sk)
 386 {
 387         mptcp_data_lock(sk);
 388         if (!sock_owned_by_user(sk))
 389                 __mptcp_set_connected(sk);
 390         else
 391                 __set_bit(MPTCP_CONNECTED, &mptcp_sk(sk)->cb_flags);
 392         mptcp_data_unlock(sk);
 393 }
 394
 395 static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 396 {
 397         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 398         struct mptcp_options_received mp_opt;
 399         struct sock *parent = subflow->conn;
 400
 401         subflow->icsk_af_ops->sk_rx_dst_set(sk, skb);
 402
 403         /* be sure no special action on any packet other than syn-ack */
 404         if (subflow->conn_finished)
 405                 return;
 406
 407         mptcp_propagate_sndbuf(parent, sk);
 408         subflow->rel_write_seq = 1;
 409         subflow->conn_finished = 1;
 410         subflow->ssn_offset = TCP_SKB_CB(skb)->seq;
 411         pr_debug("subflow=%p synack seq=%x", subflow, subflow->ssn_offset);
 412
 413         mptcp_get_options(skb, &mp_opt);
 414         if (subflow->request_mptcp) {
 415                 if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPC)) {
 416                         MPTCP_INC_STATS(sock_net(sk),
 417                                         MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
 418                         mptcp_do_fallback(sk);
 419                         pr_fallback(mptcp_sk(subflow->conn));
 420                         goto fallback;
 421                 }
 422
 423                 if (mp_opt.suboptions & OPTION_MPTCP_CSUMREQD)
 424                         WRITE_ONCE(mptcp_sk(parent)->csum_enabled, true);
 425                 if (mp_opt.deny_join_id0)
 426                         WRITE_ONCE(mptcp_sk(parent)->pm.remote_deny_join_id0, true);
 427                 subflow->mp_capable = 1;
 428                 subflow->can_ack = 1;
 429                 subflow->remote_key = mp_opt.sndr_key;
 430                 pr_debug("subflow=%p, remote_key=%llu", subflow,
 431                          subflow->remote_key);
 432                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVEACK);
 433                 mptcp_finish_connect(sk);
 434                 mptcp_set_connected(parent);
 435         } else if (subflow->request_join) {
 436                 u8 hmac[SHA256_DIGEST_SIZE];
 437
 438                 if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPJ)) {
 439                         subflow->reset_reason = MPTCP_RST_EMPTCP;
 440                         goto do_reset;
 441                 }
 442
 443                 subflow->backup = mp_opt.backup;
 444                 subflow->thmac = mp_opt.thmac;
 445                 subflow->remote_nonce = mp_opt.nonce;
 446                 subflow->remote_id = mp_opt.join_id;
 447                 pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u backup=%d",
 448                          subflow, subflow->thmac, subflow->remote_nonce,
 449                          subflow->backup);
 450
 451                 if (!subflow_thmac_valid(subflow)) {
 452                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINACKMAC);
 453                         subflow->reset_reason = MPTCP_RST_EMPTCP;
 454                         goto do_reset;
 455                 }
 456
 457                 if (!mptcp_finish_join(sk))
 458                         goto do_reset;
 459
 460                 subflow_generate_hmac(subflow->local_key, subflow->remote_key,
 461                                       subflow->local_nonce,
 462                                       subflow->remote_nonce,
 463                                       hmac);
 464                 memcpy(subflow->hmac, hmac, MPTCPOPT_HMAC_LEN);
 465
 466                 subflow->mp_join = 1;
 467                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKRX);
 468
 469                 if (subflow_use_different_dport(mptcp_sk(parent), sk)) {
 470                         pr_debug("synack inet_dport=%d %d",
 471                                  ntohs(inet_sk(sk)->inet_dport),
 472                                  ntohs(inet_sk(parent)->inet_dport));
 473                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINPORTSYNACKRX);
 474                 }
 475         } else if (mptcp_check_fallback(sk)) {
 476 fallback:
 477                 mptcp_rcv_space_init(mptcp_sk(parent), sk);
 478                 mptcp_set_connected(parent);
 479         }
 480         return;
 481
 482 do_reset:
 483         subflow->reset_transient = 0;
 484         mptcp_subflow_reset(sk);
 485 }
 486
 487 static void subflow_set_local_id(struct mptcp_subflow_context *subflow, int local_id)
 488 {
 489         subflow->local_id = local_id;
 490         subflow->local_id_valid = 1;
 491 }
 492
 493 static int subflow_chk_local_id(struct sock *sk)
 494 {
 495         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 496         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 497         int err;
 498
 499         if (likely(subflow->local_id_valid))
 500                 return 0;
 501
 502         err = mptcp_pm_get_local_id(msk, (struct sock_common *)sk);
 503         if (err < 0)
 504                 return err;
 505
 506         subflow_set_local_id(subflow, err);
 507         return 0;
 508 }
 509
 510 static int subflow_rebuild_header(struct sock *sk)
 511 {
 512         int err = subflow_chk_local_id(sk);
 513
 514         if (unlikely(err < 0))
 515                 return err;
 516
 517         return inet_sk_rebuild_header(sk);
 518 }
 519
 520 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 521 static int subflow_v6_rebuild_header(struct sock *sk)
 522 {
 523         int err = subflow_chk_local_id(sk);
 524
 525         if (unlikely(err < 0))
 526                 return err;
 527
 528         return inet6_sk_rebuild_header(sk);
 529 }
 530 #endif
 531
 532 struct request_sock_ops mptcp_subflow_request_sock_ops;
 533 static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops __ro_after_init;
 534
 535 static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 536 {
 537         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 538
 539         pr_debug("subflow=%p", subflow);
 540
 541         /* Never answer to SYNs sent to broadcast or multicast */
 542         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 543                 goto drop;
 544
 545         return tcp_conn_request(&mptcp_subflow_request_sock_ops,
 546                                 &subflow_request_sock_ipv4_ops,
 547                                 sk, skb);
 548 drop:
 549         tcp_listendrop(sk);
 550         return 0;
 551 }
 552
 553 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 554 static struct tcp_request_sock_ops subflow_request_sock_ipv6_ops __ro_after_init;
 555 static struct inet_connection_sock_af_ops subflow_v6_specific __ro_after_init;
 556 static struct inet_connection_sock_af_ops subflow_v6m_specific __ro_after_init;
 557 static struct proto tcpv6_prot_override;
 558
 559 static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 560 {
 561         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 562
 563         pr_debug("subflow=%p", subflow);
 564
 565         if (skb->protocol == htons(ETH_P_IP))
 566                 return subflow_v4_conn_request(sk, skb);
 567
 568         if (!ipv6_unicast_destination(skb))
 569                 goto drop;
 570
 571         if (ipv6_addr_v4mapped(&ipv6_hdr(skb)->saddr)) {
 572                 __IP6_INC_STATS(sock_net(sk), NULL, IPSTATS_MIB_INHDRERRORS);
 573                 return 0;
 574         }
 575
 576         return tcp_conn_request(&mptcp_subflow_request_sock_ops,
 577                                 &subflow_request_sock_ipv6_ops, sk, skb);
 578
 579 drop:
 580         tcp_listendrop(sk);
 581         return 0; /* don't send reset */
 582 }
 583 #endif
 584
 585 /* validate hmac received in third ACK */
 586 static bool subflow_hmac_valid(const struct request_sock *req,
 587                                const struct mptcp_options_received *mp_opt)
 588 {
 589         const struct mptcp_subflow_request_sock *subflow_req;
 590         u8 hmac[SHA256_DIGEST_SIZE];
 591         struct mptcp_sock *msk;
 592
 593         subflow_req = mptcp_subflow_rsk(req);
 594         msk = subflow_req->msk;
 595         if (!msk)
 596                 return false;
 597
 598         subflow_generate_hmac(msk->remote_key, msk->local_key,
 599                               subflow_req->remote_nonce,
 600                               subflow_req->local_nonce, hmac);
 601
 602         return !crypto_memneq(hmac, mp_opt->hmac, MPTCPOPT_HMAC_LEN);
 603 }
 604
 605 static void mptcp_sock_destruct(struct sock *sk)
 606 {
 607         /* if new mptcp socket isn't accepted, it is free'd
 608          * from the tcp listener sockets request queue, linked
 609          * from req->sk.  The tcp socket is released.
 610          * This calls the ULP release function which will
 611          * also remove the mptcp socket, via
 612          * sock_put(ctx->conn).
 613          *
 614          * Problem is that the mptcp socket will be in
 615          * ESTABLISHED state and will not have the SOCK_DEAD flag.
 616          * Both result in warnings from inet_sock_destruct.
 617          */
 618         if ((1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
 619                 sk->sk_state = TCP_CLOSE;
 620                 WARN_ON_ONCE(sk->sk_socket);
 621                 sock_orphan(sk);
 622         }
 623
 624         mptcp_destroy_common(mptcp_sk(sk));
 625         inet_sock_destruct(sk);
 626 }
 627
 628 static void mptcp_force_close(struct sock *sk)
 629 {
 630         /* the msk is not yet exposed to user-space */
 631         inet_sk_state_store(sk, TCP_CLOSE);
 632         sk_common_release(sk);
 633 }
 634
 635 static void subflow_ulp_fallback(struct sock *sk,
 636                                  struct mptcp_subflow_context *old_ctx)
 637 {
 638         struct inet_connection_sock *icsk = inet_csk(sk);
 639
 640         mptcp_subflow_tcp_fallback(sk, old_ctx);
 641         icsk->icsk_ulp_ops = NULL;
 642         rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
 643         tcp_sk(sk)->is_mptcp = 0;
 644
 645         mptcp_subflow_ops_undo_override(sk);
 646 }
 647
 648 static void subflow_drop_ctx(struct sock *ssk)
 649 {
 650         struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
 651
 652         if (!ctx)
 653                 return;
 654
 655         subflow_ulp_fallback(ssk, ctx);
 656         if (ctx->conn)
 657                 sock_put(ctx->conn);
 658
 659         kfree_rcu(ctx, rcu);
 660 }
 661
 662 void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow,
 663                                      struct mptcp_options_received *mp_opt)
 664 {
 665         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 666
 667         subflow->remote_key = mp_opt->sndr_key;
 668         subflow->fully_established = 1;
 669         subflow->can_ack = 1;
 670         WRITE_ONCE(msk->fully_established, true);
 671 }
 672
 673 static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 674                                           struct sk_buff *skb,
 675                                           struct request_sock *req,
 676                                           struct dst_entry *dst,
 677                                           struct request_sock *req_unhash,
 678                                           bool *own_req)
 679 {
 680         struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk);
 681         struct mptcp_subflow_request_sock *subflow_req;
 682         struct mptcp_options_received mp_opt;
 683         bool fallback, fallback_is_fatal;
 684         struct sock *new_msk = NULL;
 685         struct sock *child;
 686
 687         pr_debug("listener=%p, req=%p, conn=%p", listener, req, listener->conn);
 688
 689         /* After child creation we must look for MPC even when options
 690          * are not parsed
 691          */
 692         mp_opt.suboptions = 0;
 693
 694         /* hopefully temporary handling for MP_JOIN+syncookie */
 695         subflow_req = mptcp_subflow_rsk(req);
 696         fallback_is_fatal = tcp_rsk(req)->is_mptcp && subflow_req->mp_join;
 697         fallback = !tcp_rsk(req)->is_mptcp;
 698         if (fallback)
 699                 goto create_child;
 700
 701         /* if the sk is MP_CAPABLE, we try to fetch the client key */
 702         if (subflow_req->mp_capable) {
 703                 /* we can receive and accept an in-window, out-of-order pkt,
 704                  * which may not carry the MP_CAPABLE opt even on mptcp enabled
 705                  * paths: always try to extract the peer key, and fallback
 706                  * for packets missing it.
 707                  * Even OoO DSS packets coming legitly after dropped or
 708                  * reordered MPC will cause fallback, but we don't have other
 709                  * options.
 710                  */
 711                 mptcp_get_options(skb, &mp_opt);
 712                 if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPC)) {
 713                         fallback = true;
 714                         goto create_child;
 715                 }
 716
 717                 new_msk = mptcp_sk_clone(listener->conn, &mp_opt, req);
 718                 if (!new_msk)
 719                         fallback = true;
 720         } else if (subflow_req->mp_join) {
 721                 mptcp_get_options(skb, &mp_opt);
 722                 if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPJ) ||
 723                     !subflow_hmac_valid(req, &mp_opt) ||
 724                     !mptcp_can_accept_new_subflow(subflow_req->msk)) {
 725                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKMAC);
 726                         fallback = true;
 727                 }
 728         }
 729
 730 create_child:
 731         child = listener->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
 732                                                      req_unhash, own_req);
 733
 734         if (child && *own_req) {
 735                 struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);
 736
 737                 tcp_rsk(req)->drop_req = false;
 738
 739                 /* we need to fallback on ctx allocation failure and on pre-reqs
 740                  * checking above. In the latter scenario we additionally need
 741                  * to reset the context to non MPTCP status.
 742                  */
 743                 if (!ctx || fallback) {
 744                         if (fallback_is_fatal) {
 745                                 subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
 746                                 goto dispose_child;
 747                         }
 748
 749                         subflow_drop_ctx(child);
 750                         goto out;
 751                 }
 752
 753                 /* ssk inherits options of listener sk */
 754                 ctx->setsockopt_seq = listener->setsockopt_seq;
 755
 756                 if (ctx->mp_capable) {
 757                         /* this can't race with mptcp_close(), as the msk is
 758                          * not yet exposted to user-space
 759                          */
 760                         inet_sk_state_store((void *)new_msk, TCP_ESTABLISHED);
 761
 762                         /* record the newly created socket as the first msk
 763                          * subflow, but don't link it yet into conn_list
 764                          */
 765                         WRITE_ONCE(mptcp_sk(new_msk)->first, child);
 766
 767                         /* new mpc subflow takes ownership of the newly
 768                          * created mptcp socket
 769                          */
 770                         new_msk->sk_destruct = mptcp_sock_destruct;
 771                         mptcp_sk(new_msk)->setsockopt_seq = ctx->setsockopt_seq;
 772                         mptcp_pm_new_connection(mptcp_sk(new_msk), child, 1);
 773                         mptcp_token_accept(subflow_req, mptcp_sk(new_msk));
 774                         ctx->conn = new_msk;
 775                         new_msk = NULL;
 776
 777                         /* with OoO packets we can reach here without ingress
 778                          * mpc option
 779                          */
 780                         if (mp_opt.suboptions & OPTIONS_MPTCP_MPC)
 781                                 mptcp_subflow_fully_established(ctx, &mp_opt);
 782                 } else if (ctx->mp_join) {
 783                         struct mptcp_sock *owner;
 784
 785                         owner = subflow_req->msk;
 786                         if (!owner) {
 787                                 subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
 788                                 goto dispose_child;
 789                         }
 790
 791                         /* move the msk reference ownership to the subflow */
 792                         subflow_req->msk = NULL;
 793                         ctx->conn = (struct sock *)owner;
 794
 795                         if (subflow_use_different_sport(owner, sk)) {
 796                                 pr_debug("ack inet_sport=%d %d",
 797                                          ntohs(inet_sk(sk)->inet_sport),
 798                                          ntohs(inet_sk((struct sock *)owner)->inet_sport));
 799                                 if (!mptcp_pm_sport_in_anno_list(owner, sk)) {
 800                                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTACKRX);
 801                                         goto dispose_child;
 802                                 }
 803                                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTACKRX);
 804                         }
 805
 806                         if (!mptcp_finish_join(child))
 807                                 goto dispose_child;
 808
 809                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKRX);
 810                         tcp_rsk(req)->drop_req = true;
 811                 }
 812         }
 813
 814 out:
 815         /* dispose of the left over mptcp master, if any */
 816         if (unlikely(new_msk))
 817                 mptcp_force_close(new_msk);
 818
 819         /* check for expected invariant - should never trigger, just help
 820          * catching eariler subtle bugs
 821          */
 822         WARN_ON_ONCE(child && *own_req && tcp_sk(child)->is_mptcp &&
 823                      (!mptcp_subflow_ctx(child) ||
 824                       !mptcp_subflow_ctx(child)->conn));
 825         return child;
 826
 827 dispose_child:
 828         subflow_drop_ctx(child);
 829         tcp_rsk(req)->drop_req = true;
 830         inet_csk_prepare_for_destroy_sock(child);
 831         tcp_done(child);
 832         req->rsk_ops->send_reset(sk, skb);
 833
 834         /* The last child reference will be released by the caller */
 835         return child;
 836 }
 837
 838 static struct inet_connection_sock_af_ops subflow_specific __ro_after_init;
 839 static struct proto tcp_prot_override;
 840
 841 enum mapping_status {
 842         MAPPING_OK,
 843         MAPPING_INVALID,
 844         MAPPING_EMPTY,
 845         MAPPING_DATA_FIN,
 846         MAPPING_DUMMY
 847 };
 848
 849 static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
 850 {
 851         pr_debug("Bad mapping: ssn=%d map_seq=%d map_data_len=%d",
 852                  ssn, subflow->map_subflow_seq, subflow->map_data_len);
 853 }
 854
 855 static bool skb_is_fully_mapped(struct sock *ssk, struct sk_buff *skb)
 856 {
 857         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 858         unsigned int skb_consumed;
 859
 860         skb_consumed = tcp_sk(ssk)->copied_seq - TCP_SKB_CB(skb)->seq;
 861         if (WARN_ON_ONCE(skb_consumed >= skb->len))
 862                 return true;
 863
 864         return skb->len - skb_consumed <= subflow->map_data_len -
 865                                           mptcp_subflow_get_map_offset(subflow);
 866 }
 867
 868 static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
 869 {
 870         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 871         u32 ssn = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
 872
 873         if (unlikely(before(ssn, subflow->map_subflow_seq))) {
 874                 /* Mapping covers data later in the subflow stream,
 875                  * currently unsupported.
 876                  */
 877                 dbg_bad_map(subflow, ssn);
 878                 return false;
 879         }
 880         if (unlikely(!before(ssn, subflow->map_subflow_seq +
 881                                   subflow->map_data_len))) {
 882                 /* Mapping does covers past subflow data, invalid */
 883                 dbg_bad_map(subflow, ssn);
 884                 return false;
 885         }
 886         return true;
 887 }
 888
 889 static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *skb,
 890                                               bool csum_reqd)
 891 {
 892         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 893         u32 offset, seq, delta;
 894         __sum16 csum;
 895         int len;
 896
 897         if (!csum_reqd)
 898                 return MAPPING_OK;
 899
 900         /* mapping already validated on previous traversal */
 901         if (subflow->map_csum_len == subflow->map_data_len)
 902                 return MAPPING_OK;
 903
 904         /* traverse the receive queue, ensuring it contains a full
 905          * DSS mapping and accumulating the related csum.
 906          * Preserve the accoumlate csum across multiple calls, to compute
 907          * the csum only once
 908          */
 909         delta = subflow->map_data_len - subflow->map_csum_len;
 910         for (;;) {
 911                 seq = tcp_sk(ssk)->copied_seq + subflow->map_csum_len;
 912                 offset = seq - TCP_SKB_CB(skb)->seq;
 913
 914                 /* if the current skb has not been accounted yet, csum its contents
 915                  * up to the amount covered by the current DSS
 916                  */
 917                 if (offset < skb->len) {
 918                         __wsum csum;
 919
 920                         len = min(skb->len - offset, delta);
 921                         csum = skb_checksum(skb, offset, len, 0);
 922                         subflow->map_data_csum = csum_block_add(subflow->map_data_csum, csum,
 923                                                                 subflow->map_csum_len);
 924
 925                         delta -= len;
 926                         subflow->map_csum_len += len;
 927                 }
 928                 if (delta == 0)
 929                         break;
 930
 931                 if (skb_queue_is_last(&ssk->sk_receive_queue, skb)) {
 932                         /* if this subflow is closed, the partial mapping
 933                          * will be never completed; flush the pending skbs, so
 934                          * that subflow_sched_work_if_closed() can kick in
 935                          */
 936                         if (unlikely(ssk->sk_state == TCP_CLOSE))
 937                                 while ((skb = skb_peek(&ssk->sk_receive_queue)))
 938                                         sk_eat_skb(ssk, skb);
 939
 940                         /* not enough data to validate the csum */
 941                         return MAPPING_EMPTY;
 942                 }
 943
 944                 /* the DSS mapping for next skbs will be validated later,
 945                  * when a get_mapping_status call will process such skb
 946                  */
 947                 skb = skb->next;
 948         }
 949
 950         /* note that 'map_data_len' accounts only for the carried data, does
 951          * not include the eventual seq increment due to the data fin,
 952          * while the pseudo header requires the original DSS data len,
 953          * including that
 954          */
 955         csum = __mptcp_make_csum(subflow->map_seq,
 956                                  subflow->map_subflow_seq,
 957                                  subflow->map_data_len + subflow->map_data_fin,
 958                                  subflow->map_data_csum);
 959         if (unlikely(csum)) {
 960                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
 961                 if (subflow->mp_join || subflow->valid_csum_seen) {
 962                         subflow->send_mp_fail = 1;
 963                         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPFAILTX);
 964                 }
 965                 return subflow->mp_join ? MAPPING_INVALID : MAPPING_DUMMY;
 966         }
 967
 968         subflow->valid_csum_seen = 1;
 969         return MAPPING_OK;
 970 }
 971
 972 static enum mapping_status get_mapping_status(struct sock *ssk,
 973                                               struct mptcp_sock *msk)
 974 {
 975         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 976         bool csum_reqd = READ_ONCE(msk->csum_enabled);
 977         struct sock *sk = (struct sock *)msk;
 978         struct mptcp_ext *mpext;
 979         struct sk_buff *skb;
 980         u16 data_len;
 981         u64 map_seq;
 982
 983         skb = skb_peek(&ssk->sk_receive_queue);
 984         if (!skb)
 985                 return MAPPING_EMPTY;
 986
 987         if (mptcp_check_fallback(ssk))
 988                 return MAPPING_DUMMY;
 989
 990         mpext = mptcp_get_ext(skb);
 991         if (!mpext || !mpext->use_map) {
 992                 if (!subflow->map_valid && !skb->len) {
 993                         /* the TCP stack deliver 0 len FIN pkt to the receive
 994                          * queue, that is the only 0len pkts ever expected here,
 995                          * and we can admit no mapping only for 0 len pkts
 996                          */
 997                         if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
 998                                 WARN_ONCE(1, "0len seq %d:%d flags %x",
 999                                           TCP_SKB_CB(skb)->seq,
1000                                           TCP_SKB_CB(skb)->end_seq,
1001                                           TCP_SKB_CB(skb)->tcp_flags);
1002                         sk_eat_skb(ssk, skb);
1003                         return MAPPING_EMPTY;
1004                 }
1005
1006                 if (!subflow->map_valid)
1007                         return MAPPING_INVALID;
1008
1009                 goto validate_seq;
1010         }
1011
1012         trace_get_mapping_status(mpext);
1013
1014         data_len = mpext->data_len;
1015         if (data_len == 0) {
1016                 pr_debug("infinite mapping received");
1017                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX);
1018                 subflow->map_data_len = 0;
1019                 if (!sock_flag(ssk, SOCK_DEAD))
1020                         sk_stop_timer(sk, &sk->sk_timer);
1021
1022                 return MAPPING_INVALID;
1023         }
1024
1025         if (mpext->data_fin == 1) {
1026                 if (data_len == 1) {
1027                         bool updated = mptcp_update_rcv_data_fin(msk, mpext->data_seq,
1028                                                                  mpext->dsn64);
1029                         pr_debug("DATA_FIN with no payload seq=%llu", mpext->data_seq);
1030                         if (subflow->map_valid) {
1031                                 /* A DATA_FIN might arrive in a DSS
1032                                  * option before the previous mapping
1033                                  * has been fully consumed. Continue
1034                                  * handling the existing mapping.
1035                                  */
1036                                 skb_ext_del(skb, SKB_EXT_MPTCP);
1037                                 return MAPPING_OK;
1038                         } else {
1039                                 if (updated && schedule_work(&msk->work))
1040                                         sock_hold((struct sock *)msk);
1041
1042                                 return MAPPING_DATA_FIN;
1043                         }
1044                 } else {
1045                         u64 data_fin_seq = mpext->data_seq + data_len - 1;
1046
1047                         /* If mpext->data_seq is a 32-bit value, data_fin_seq
1048                          * must also be limited to 32 bits.
1049                          */
1050                         if (!mpext->dsn64)
1051                                 data_fin_seq &= GENMASK_ULL(31, 0);
1052
1053                         mptcp_update_rcv_data_fin(msk, data_fin_seq, mpext->dsn64);
1054                         pr_debug("DATA_FIN with mapping seq=%llu dsn64=%d",
1055                                  data_fin_seq, mpext->dsn64);
1056                 }
1057
1058                 /* Adjust for DATA_FIN using 1 byte of sequence space */
1059                 data_len--;
1060         }
1061
1062         map_seq = mptcp_expand_seq(READ_ONCE(msk->ack_seq), mpext->data_seq, mpext->dsn64);
1063         WRITE_ONCE(mptcp_sk(subflow->conn)->use_64bit_ack, !!mpext->dsn64);
1064
1065         if (subflow->map_valid) {
1066                 /* Allow replacing only with an identical map */
1067                 if (subflow->map_seq == map_seq &&
1068                     subflow->map_subflow_seq == mpext->subflow_seq &&
1069                     subflow->map_data_len == data_len &&
1070                     subflow->map_csum_reqd == mpext->csum_reqd) {
1071                         skb_ext_del(skb, SKB_EXT_MPTCP);
1072                         goto validate_csum;
1073                 }
1074
1075                 /* If this skb data are fully covered by the current mapping,
1076                  * the new map would need caching, which is not supported
1077                  */
1078                 if (skb_is_fully_mapped(ssk, skb)) {
1079                         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSNOMATCH);
1080                         return MAPPING_INVALID;
1081                 }
1082
1083                 /* will validate the next map after consuming the current one */
1084                 goto validate_csum;
1085         }
1086
1087         subflow->map_seq = map_seq;
1088         subflow->map_subflow_seq = mpext->subflow_seq;
1089         subflow->map_data_len = data_len;
1090         subflow->map_valid = 1;
1091         subflow->map_data_fin = mpext->data_fin;
1092         subflow->mpc_map = mpext->mpc_map;
1093         subflow->map_csum_reqd = mpext->csum_reqd;
1094         subflow->map_csum_len = 0;
1095         subflow->map_data_csum = csum_unfold(mpext->csum);
1096
1097         /* Cfr RFC 8684 Section 3.3.0 */
1098         if (unlikely(subflow->map_csum_reqd != csum_reqd))
1099                 return MAPPING_INVALID;
1100
1101         pr_debug("new map seq=%llu subflow_seq=%u data_len=%u csum=%d:%u",
1102                  subflow->map_seq, subflow->map_subflow_seq,
1103                  subflow->map_data_len, subflow->map_csum_reqd,
1104                  subflow->map_data_csum);
1105
1106 validate_seq:
1107         /* we revalidate valid mapping on new skb, because we must ensure
1108          * the current skb is completely covered by the available mapping
1109          */
1110         if (!validate_mapping(ssk, skb)) {
1111                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSTCPMISMATCH);
1112                 return MAPPING_INVALID;
1113         }
1114
1115         skb_ext_del(skb, SKB_EXT_MPTCP);
1116
1117 validate_csum:
1118         return validate_data_csum(ssk, skb, csum_reqd);
1119 }
1120
1121 static void mptcp_subflow_discard_data(struct sock *ssk, struct sk_buff *skb,
1122                                        u64 limit)
1123 {
1124         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1125         bool fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
1126         u32 incr;
1127
1128         incr = limit >= skb->len ? skb->len + fin : limit;
1129
1130         pr_debug("discarding=%d len=%d seq=%d", incr, skb->len,
1131                  subflow->map_subflow_seq);
1132         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DUPDATA);
1133         tcp_sk(ssk)->copied_seq += incr;
1134         if (!before(tcp_sk(ssk)->copied_seq, TCP_SKB_CB(skb)->end_seq))
1135                 sk_eat_skb(ssk, skb);
1136         if (mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len)
1137                 subflow->map_valid = 0;
1138 }
1139
1140 /* sched mptcp worker to remove the subflow if no more data is pending */
1141 static void subflow_sched_work_if_closed(struct mptcp_sock *msk, struct sock *ssk)
1142 {
1143         struct sock *sk = (struct sock *)msk;
1144
1145         if (likely(ssk->sk_state != TCP_CLOSE))
1146                 return;
1147
1148         if (skb_queue_empty(&ssk->sk_receive_queue) &&
1149             !test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags)) {
1150                 sock_hold(sk);
1151                 if (!schedule_work(&msk->work))
1152                         sock_put(sk);
1153         }
1154 }
1155
1156 static bool subflow_can_fallback(struct mptcp_subflow_context *subflow)
1157 {
1158         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1159
1160         if (subflow->mp_join)
1161                 return false;
1162         else if (READ_ONCE(msk->csum_enabled))
1163                 return !subflow->valid_csum_seen;
1164         else
1165                 return !subflow->fully_established;
1166 }
1167
1168 static bool subflow_check_data_avail(struct sock *ssk)
1169 {
1170         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1171         enum mapping_status status;
1172         struct mptcp_sock *msk;
1173         struct sk_buff *skb;
1174
1175         if (!skb_peek(&ssk->sk_receive_queue))
1176                 WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_NODATA);
1177         if (subflow->data_avail)
1178                 return true;
1179
1180         msk = mptcp_sk(subflow->conn);
1181         for (;;) {
1182                 u64 ack_seq;
1183                 u64 old_ack;
1184
1185                 status = get_mapping_status(ssk, msk);
1186                 trace_subflow_check_data_avail(status, skb_peek(&ssk->sk_receive_queue));
1187                 if (unlikely(status == MAPPING_INVALID))
1188                         goto fallback;
1189
1190                 if (unlikely(status == MAPPING_DUMMY))
1191                         goto fallback;
1192
1193                 if (status != MAPPING_OK)
1194                         goto no_data;
1195
1196                 skb = skb_peek(&ssk->sk_receive_queue);
1197                 if (WARN_ON_ONCE(!skb))
1198                         goto no_data;
1199
1200                 /* if msk lacks the remote key, this subflow must provide an
1201                  * MP_CAPABLE-based mapping
1202                  */
1203                 if (unlikely(!READ_ONCE(msk->can_ack))) {
1204                         if (!subflow->mpc_map)
1205                                 goto fallback;
1206                         WRITE_ONCE(msk->remote_key, subflow->remote_key);
1207                         WRITE_ONCE(msk->ack_seq, subflow->map_seq);
1208                         WRITE_ONCE(msk->can_ack, true);
1209                 }
1210
1211                 old_ack = READ_ONCE(msk->ack_seq);
1212                 ack_seq = mptcp_subflow_get_mapped_dsn(subflow);
1213                 pr_debug("msk ack_seq=%llx subflow ack_seq=%llx", old_ack,
1214                          ack_seq);
1215                 if (unlikely(before64(ack_seq, old_ack))) {
1216                         mptcp_subflow_discard_data(ssk, skb, old_ack - ack_seq);
1217                         continue;
1218                 }
1219
1220                 WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_DATA_AVAIL);
1221                 break;
1222         }
1223         return true;
1224
1225 no_data:
1226         subflow_sched_work_if_closed(msk, ssk);
1227         return false;
1228
1229 fallback:
1230         if (!__mptcp_check_fallback(msk)) {
1231                 /* RFC 8684 section 3.7. */
1232                 if (subflow->send_mp_fail) {
1233                         if (!READ_ONCE(msk->allow_infinite_fallback)) {
1234                                 ssk->sk_err = EBADMSG;
1235                                 tcp_set_state(ssk, TCP_CLOSE);
1236                                 subflow->reset_transient = 0;
1237                                 subflow->reset_reason = MPTCP_RST_EMIDDLEBOX;
1238                                 tcp_send_active_reset(ssk, GFP_ATOMIC);
1239                                 while ((skb = skb_peek(&ssk->sk_receive_queue)))
1240                                         sk_eat_skb(ssk, skb);
1241                         } else if (!sock_flag(ssk, SOCK_DEAD)) {
1242                                 WRITE_ONCE(subflow->mp_fail_response_expect, true);
1243                                 sk_reset_timer((struct sock *)msk,
1244                                                &((struct sock *)msk)->sk_timer,
1245                                                jiffies + TCP_RTO_MAX);
1246                         }
1247                         WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_NODATA);
1248                         return true;
1249                 }
1250
1251                 if (!subflow_can_fallback(subflow) && subflow->map_data_len) {
1252                         /* fatal protocol error, close the socket.
1253                          * subflow_error_report() will introduce the appropriate barriers
1254                          */
1255                         ssk->sk_err = EBADMSG;
1256                         tcp_set_state(ssk, TCP_CLOSE);
1257                         subflow->reset_transient = 0;
1258                         subflow->reset_reason = MPTCP_RST_EMPTCP;
1259                         tcp_send_active_reset(ssk, GFP_ATOMIC);
1260                         WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_NODATA);
1261                         return false;
1262                 }
1263
1264                 __mptcp_do_fallback(msk);
1265         }
1266
1267         skb = skb_peek(&ssk->sk_receive_queue);
1268         subflow->map_valid = 1;
1269         subflow->map_seq = READ_ONCE(msk->ack_seq);
1270         subflow->map_data_len = skb->len;
1271         subflow->map_subflow_seq = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
1272         WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_DATA_AVAIL);
1273         return true;
1274 }
1275
1276 bool mptcp_subflow_data_available(struct sock *sk)
1277 {
1278         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1279
1280         /* check if current mapping is still valid */
1281         if (subflow->map_valid &&
1282             mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len) {
1283                 subflow->map_valid = 0;
1284                 WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_NODATA);
1285
1286                 pr_debug("Done with mapping: seq=%u data_len=%u",
1287                          subflow->map_subflow_seq,
1288                          subflow->map_data_len);
1289         }
1290
1291         return subflow_check_data_avail(sk);
1292 }
1293
1294 /* If ssk has an mptcp parent socket, use the mptcp rcvbuf occupancy,
1295  * not the ssk one.
1296  *
1297  * In mptcp, rwin is about the mptcp-level connection data.
1298  *
1299  * Data that is still on the ssk rx queue can thus be ignored,
1300  * as far as mptcp peer is concerned that data is still inflight.
1301  * DSS ACK is updated when skb is moved to the mptcp rx queue.
1302  */
1303 void mptcp_space(const struct sock *ssk, int *space, int *full_space)
1304 {
1305         const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1306         const struct sock *sk = subflow->conn;
1307
1308         *space = __mptcp_space(sk);
1309         *full_space = tcp_full_space(sk);
1310 }
1311
1312 void __mptcp_error_report(struct sock *sk)
1313 {
1314         struct mptcp_subflow_context *subflow;
1315         struct mptcp_sock *msk = mptcp_sk(sk);
1316
1317         mptcp_for_each_subflow(msk, subflow) {
1318                 struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
1319                 int err = sock_error(ssk);
1320
1321                 if (!err)
1322                         continue;
1323
1324                 /* only propagate errors on fallen-back sockets or
1325                  * on MPC connect
1326                  */
1327                 if (sk->sk_state != TCP_SYN_SENT && !__mptcp_check_fallback(msk))
1328                         continue;
1329
1330                 inet_sk_state_store(sk, inet_sk_state_load(ssk));
1331                 sk->sk_err = -err;
1332
1333                 /* This barrier is coupled with smp_rmb() in mptcp_poll() */
1334                 smp_wmb();
1335                 sk_error_report(sk);
1336                 break;
1337         }
1338 }
1339
1340 static void subflow_error_report(struct sock *ssk)
1341 {
1342         struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
1343
1344         mptcp_data_lock(sk);
1345         if (!sock_owned_by_user(sk))
1346                 __mptcp_error_report(sk);
1347         else
1348                 __set_bit(MPTCP_ERROR_REPORT,  &mptcp_sk(sk)->cb_flags);
1349         mptcp_data_unlock(sk);
1350 }
1351
1352 static void subflow_data_ready(struct sock *sk)
1353 {
1354         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1355         u16 state = 1 << inet_sk_state_load(sk);
1356         struct sock *parent = subflow->conn;
1357         struct mptcp_sock *msk;
1358
1359         msk = mptcp_sk(parent);
1360         if (state & TCPF_LISTEN) {
1361                 /* MPJ subflow are removed from accept queue before reaching here,
1362                  * avoid stray wakeups
1363                  */
1364                 if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue))
1365                         return;
1366
1367                 parent->sk_data_ready(parent);
1368                 return;
1369         }
1370
1371         WARN_ON_ONCE(!__mptcp_check_fallback(msk) && !subflow->mp_capable &&
1372                      !subflow->mp_join && !(state & TCPF_CLOSE));
1373
1374         if (mptcp_subflow_data_available(sk))
1375                 mptcp_data_ready(parent, sk);
1376         else if (unlikely(sk->sk_err))
1377                 subflow_error_report(sk);
1378 }
1379
1380 static void subflow_write_space(struct sock *ssk)
1381 {
1382         struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
1383
1384         mptcp_propagate_sndbuf(sk, ssk);
1385         mptcp_write_space(sk);
1386 }
1387
1388 static const struct inet_connection_sock_af_ops *
1389 subflow_default_af_ops(struct sock *sk)
1390 {
1391 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1392         if (sk->sk_family == AF_INET6)
1393                 return &subflow_v6_specific;
1394 #endif
1395         return &subflow_specific;
1396 }
1397
1398 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1399 void mptcpv6_handle_mapped(struct sock *sk, bool mapped)
1400 {
1401         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1402         struct inet_connection_sock *icsk = inet_csk(sk);
1403         const struct inet_connection_sock_af_ops *target;
1404
1405         target = mapped ? &subflow_v6m_specific : subflow_default_af_ops(sk);
1406
1407         pr_debug("subflow=%p family=%d ops=%p target=%p mapped=%d",
1408                  subflow, sk->sk_family, icsk->icsk_af_ops, target, mapped);
1409
1410         if (likely(icsk->icsk_af_ops == target))
1411                 return;
1412
1413         subflow->icsk_af_ops = icsk->icsk_af_ops;
1414         icsk->icsk_af_ops = target;
1415 }
1416 #endif
1417
1418 void mptcp_info2sockaddr(const struct mptcp_addr_info *info,
1419                          struct sockaddr_storage *addr,
1420                          unsigned short family)
1421 {
1422         memset(addr, 0, sizeof(*addr));
1423         addr->ss_family = family;
1424         if (addr->ss_family == AF_INET) {
1425                 struct sockaddr_in *in_addr = (struct sockaddr_in *)addr;
1426
1427                 if (info->family == AF_INET)
1428                         in_addr->sin_addr = info->addr;
1429 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1430                 else if (ipv6_addr_v4mapped(&info->addr6))
1431                         in_addr->sin_addr.s_addr = info->addr6.s6_addr32[3];
1432 #endif
1433                 in_addr->sin_port = info->port;
1434         }
1435 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1436         else if (addr->ss_family == AF_INET6) {
1437                 struct sockaddr_in6 *in6_addr = (struct sockaddr_in6 *)addr;
1438
1439                 if (info->family == AF_INET)
1440                         ipv6_addr_set_v4mapped(info->addr.s_addr,
1441                                                &in6_addr->sin6_addr);
1442                 else
1443                         in6_addr->sin6_addr = info->addr6;
1444                 in6_addr->sin6_port = info->port;
1445         }
1446 #endif
1447 }
1448
1449 int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
1450                             const struct mptcp_addr_info *remote)
1451 {
1452         struct mptcp_sock *msk = mptcp_sk(sk);
1453         struct mptcp_subflow_context *subflow;
1454         struct sockaddr_storage addr;
1455         int remote_id = remote->id;
1456         int local_id = loc->id;
1457         int err = -ENOTCONN;
1458         struct socket *sf;
1459         struct sock *ssk;
1460         u32 remote_token;
1461         int addrlen;
1462         int ifindex;
1463         u8 flags;
1464
1465         if (!mptcp_is_fully_established(sk))
1466                 goto err_out;
1467
1468         err = mptcp_subflow_create_socket(sk, &sf);
1469         if (err)
1470                 goto err_out;
1471
1472         ssk = sf->sk;
1473         subflow = mptcp_subflow_ctx(ssk);
1474         do {
1475                 get_random_bytes(&subflow->local_nonce, sizeof(u32));
1476         } while (!subflow->local_nonce);
1477
1478         if (local_id)
1479                 subflow_set_local_id(subflow, local_id);
1480
1481         mptcp_pm_get_flags_and_ifindex_by_id(msk, local_id,
1482                                              &flags, &ifindex);
1483         subflow->remote_key = msk->remote_key;
1484         subflow->local_key = msk->local_key;
1485         subflow->token = msk->token;
1486         mptcp_info2sockaddr(loc, &addr, ssk->sk_family);
1487
1488         addrlen = sizeof(struct sockaddr_in);
1489 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1490         if (addr.ss_family == AF_INET6)
1491                 addrlen = sizeof(struct sockaddr_in6);
1492 #endif
1493         mptcp_sockopt_sync(msk, ssk);
1494
1495         ssk->sk_bound_dev_if = ifindex;
1496         err = kernel_bind(sf, (struct sockaddr *)&addr, addrlen);
1497         if (err)
1498                 goto failed;
1499
1500         mptcp_crypto_key_sha(subflow->remote_key, &remote_token, NULL);
1501         pr_debug("msk=%p remote_token=%u local_id=%d remote_id=%d", msk,
1502                  remote_token, local_id, remote_id);
1503         subflow->remote_token = remote_token;
1504         subflow->remote_id = remote_id;
1505         subflow->request_join = 1;
1506         subflow->request_bkup = !!(flags & MPTCP_PM_ADDR_FLAG_BACKUP);
1507         mptcp_info2sockaddr(remote, &addr, ssk->sk_family);
1508
1509         sock_hold(ssk);
1510         list_add_tail(&subflow->node, &msk->conn_list);
1511         err = kernel_connect(sf, (struct sockaddr *)&addr, addrlen, O_NONBLOCK);
1512         if (err && err != -EINPROGRESS)
1513                 goto failed_unlink;
1514
1515         /* discard the subflow socket */
1516         mptcp_sock_graft(ssk, sk->sk_socket);
1517         iput(SOCK_INODE(sf));
1518         WRITE_ONCE(msk->allow_infinite_fallback, false);
1519         return err;
1520
1521 failed_unlink:
1522         list_del(&subflow->node);
1523         sock_put(mptcp_subflow_tcp_sock(subflow));
1524
1525 failed:
1526         subflow->disposable = 1;
1527         sock_release(sf);
1528
1529 err_out:
1530         /* we account subflows before the creation, and this failures will not
1531          * be caught by sk_state_change()
1532          */
1533         mptcp_pm_close_subflow(msk);
1534         return err;
1535 }
1536
1537 static void mptcp_attach_cgroup(struct sock *parent, struct sock *child)
1538 {
1539 #ifdef CONFIG_SOCK_CGROUP_DATA
1540         struct sock_cgroup_data *parent_skcd = &parent->sk_cgrp_data,
1541                                 *child_skcd = &child->sk_cgrp_data;
1542
1543         /* only the additional subflows created by kworkers have to be modified */
1544         if (cgroup_id(sock_cgroup_ptr(parent_skcd)) !=
1545             cgroup_id(sock_cgroup_ptr(child_skcd))) {
1546 #ifdef CONFIG_MEMCG
1547                 struct mem_cgroup *memcg = parent->sk_memcg;
1548
1549                 mem_cgroup_sk_free(child);
1550                 if (memcg && css_tryget(&memcg->css))
1551                         child->sk_memcg = memcg;
1552 #endif /* CONFIG_MEMCG */
1553
1554                 cgroup_sk_free(child_skcd);
1555                 *child_skcd = *parent_skcd;
1556                 cgroup_sk_clone(child_skcd);
1557         }
1558 #endif /* CONFIG_SOCK_CGROUP_DATA */
1559 }
1560
1561 static void mptcp_subflow_ops_override(struct sock *ssk)
1562 {
1563 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1564         if (ssk->sk_prot == &tcpv6_prot)
1565                 ssk->sk_prot = &tcpv6_prot_override;
1566         else
1567 #endif
1568                 ssk->sk_prot = &tcp_prot_override;
1569 }
1570
1571 static void mptcp_subflow_ops_undo_override(struct sock *ssk)
1572 {
1573 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1574         if (ssk->sk_prot == &tcpv6_prot_override)
1575                 ssk->sk_prot = &tcpv6_prot;
1576         else
1577 #endif
1578                 ssk->sk_prot = &tcp_prot;
1579 }
1580 int mptcp_subflow_create_socket(struct sock *sk, struct socket **new_sock)
1581 {
1582         struct mptcp_subflow_context *subflow;
1583         struct net *net = sock_net(sk);
1584         struct socket *sf;
1585         int err;
1586
1587         /* un-accepted server sockets can reach here - on bad configuration
1588          * bail early to avoid greater trouble later
1589          */
1590         if (unlikely(!sk->sk_socket))
1591                 return -EINVAL;
1592
1593         err = sock_create_kern(net, sk->sk_family, SOCK_STREAM, IPPROTO_TCP,
1594                                &sf);
1595         if (err)
1596                 return err;
1597
1598         lock_sock(sf->sk);
1599
1600         /* the newly created socket has to be in the same cgroup as its parent */
1601         mptcp_attach_cgroup(sk, sf->sk);
1602
1603         /* kernel sockets do not by default acquire net ref, but TCP timer
1604          * needs it.
1605          */
1606         sf->sk->sk_net_refcnt = 1;
1607         get_net_track(net, &sf->sk->ns_tracker, GFP_KERNEL);
1608         sock_inuse_add(net, 1);
1609         err = tcp_set_ulp(sf->sk, "mptcp");
1610         release_sock(sf->sk);
1611
1612         if (err) {
1613                 sock_release(sf);
1614                 return err;
1615         }
1616
1617         /* the newly created socket really belongs to the owning MPTCP master
1618          * socket, even if for additional subflows the allocation is performed
1619          * by a kernel workqueue. Adjust inode references, so that the
1620          * procfs/diag interaces really show this one belonging to the correct
1621          * user.
1622          */
1623         SOCK_INODE(sf)->i_ino = SOCK_INODE(sk->sk_socket)->i_ino;
1624         SOCK_INODE(sf)->i_uid = SOCK_INODE(sk->sk_socket)->i_uid;
1625         SOCK_INODE(sf)->i_gid = SOCK_INODE(sk->sk_socket)->i_gid;
1626
1627         subflow = mptcp_subflow_ctx(sf->sk);
1628         pr_debug("subflow=%p", subflow);
1629
1630         *new_sock = sf;
1631         sock_hold(sk);
1632         subflow->conn = sk;
1633         mptcp_subflow_ops_override(sf->sk);
1634
1635         return 0;
1636 }
1637
1638 static struct mptcp_subflow_context *subflow_create_ctx(struct sock *sk,
1639                                                         gfp_t priority)
1640 {
1641         struct inet_connection_sock *icsk = inet_csk(sk);
1642         struct mptcp_subflow_context *ctx;
1643
1644         ctx = kzalloc(sizeof(*ctx), priority);
1645         if (!ctx)
1646                 return NULL;
1647
1648         rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
1649         INIT_LIST_HEAD(&ctx->node);
1650         INIT_LIST_HEAD(&ctx->delegated_node);
1651
1652         pr_debug("subflow=%p", ctx);
1653
1654         ctx->tcp_sock = sk;
1655
1656         return ctx;
1657 }
1658
1659 static void __subflow_state_change(struct sock *sk)
1660 {
1661         struct socket_wq *wq;
1662
1663         rcu_read_lock();
1664         wq = rcu_dereference(sk->sk_wq);
1665         if (skwq_has_sleeper(wq))
1666                 wake_up_interruptible_all(&wq->wait);
1667         rcu_read_unlock();
1668 }
1669
1670 static bool subflow_is_done(const struct sock *sk)
1671 {
1672         return sk->sk_shutdown & RCV_SHUTDOWN || sk->sk_state == TCP_CLOSE;
1673 }
1674
1675 static void subflow_state_change(struct sock *sk)
1676 {
1677         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1678         struct sock *parent = subflow->conn;
1679
1680         __subflow_state_change(sk);
1681
1682         if (subflow_simultaneous_connect(sk)) {
1683                 mptcp_propagate_sndbuf(parent, sk);
1684                 mptcp_do_fallback(sk);
1685                 mptcp_rcv_space_init(mptcp_sk(parent), sk);
1686                 pr_fallback(mptcp_sk(parent));
1687                 subflow->conn_finished = 1;
1688                 mptcp_set_connected(parent);
1689         }
1690
1691         /* as recvmsg() does not acquire the subflow socket for ssk selection
1692          * a fin packet carrying a DSS can be unnoticed if we don't trigger
1693          * the data available machinery here.
1694          */
1695         if (mptcp_subflow_data_available(sk))
1696                 mptcp_data_ready(parent, sk);
1697         else if (unlikely(sk->sk_err))
1698                 subflow_error_report(sk);
1699
1700         subflow_sched_work_if_closed(mptcp_sk(parent), sk);
1701
1702         if (__mptcp_check_fallback(mptcp_sk(parent)) &&
1703             !subflow->rx_eof && subflow_is_done(sk)) {
1704                 subflow->rx_eof = 1;
1705                 mptcp_subflow_eof(parent);
1706         }
1707 }
1708
1709 static int subflow_ulp_init(struct sock *sk)
1710 {
1711         struct inet_connection_sock *icsk = inet_csk(sk);
1712         struct mptcp_subflow_context *ctx;
1713         struct tcp_sock *tp = tcp_sk(sk);
1714         int err = 0;
1715
1716         /* disallow attaching ULP to a socket unless it has been
1717          * created with sock_create_kern()
1718          */
1719         if (!sk->sk_kern_sock) {
1720                 err = -EOPNOTSUPP;
1721                 goto out;
1722         }
1723
1724         ctx = subflow_create_ctx(sk, GFP_KERNEL);
1725         if (!ctx) {
1726                 err = -ENOMEM;
1727                 goto out;
1728         }
1729
1730         pr_debug("subflow=%p, family=%d", ctx, sk->sk_family);
1731
1732         tp->is_mptcp = 1;
1733         ctx->icsk_af_ops = icsk->icsk_af_ops;
1734         icsk->icsk_af_ops = subflow_default_af_ops(sk);
1735         ctx->tcp_state_change = sk->sk_state_change;
1736         ctx->tcp_error_report = sk->sk_error_report;
1737
1738         WARN_ON_ONCE(sk->sk_data_ready != sock_def_readable);
1739         WARN_ON_ONCE(sk->sk_write_space != sk_stream_write_space);
1740
1741         sk->sk_data_ready = subflow_data_ready;
1742         sk->sk_write_space = subflow_write_space;
1743         sk->sk_state_change = subflow_state_change;
1744         sk->sk_error_report = subflow_error_report;
1745 out:
1746         return err;
1747 }
1748
1749 static void subflow_ulp_release(struct sock *ssk)
1750 {
1751         struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
1752         bool release = true;
1753         struct sock *sk;
1754
1755         if (!ctx)
1756                 return;
1757
1758         sk = ctx->conn;
1759         if (sk) {
1760                 /* if the msk has been orphaned, keep the ctx
1761                  * alive, will be freed by __mptcp_close_ssk(),
1762                  * when the subflow is still unaccepted
1763                  */
1764                 release = ctx->disposable || list_empty(&ctx->node);
1765                 sock_put(sk);
1766         }
1767
1768         mptcp_subflow_ops_undo_override(ssk);
1769         if (release)
1770                 kfree_rcu(ctx, rcu);
1771 }
1772
1773 static void subflow_ulp_clone(const struct request_sock *req,
1774                               struct sock *newsk,
1775                               const gfp_t priority)
1776 {
1777         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
1778         struct mptcp_subflow_context *old_ctx = mptcp_subflow_ctx(newsk);
1779         struct mptcp_subflow_context *new_ctx;
1780
1781         if (!tcp_rsk(req)->is_mptcp ||
1782             (!subflow_req->mp_capable && !subflow_req->mp_join)) {
1783                 subflow_ulp_fallback(newsk, old_ctx);
1784                 return;
1785         }
1786
1787         new_ctx = subflow_create_ctx(newsk, priority);
1788         if (!new_ctx) {
1789                 subflow_ulp_fallback(newsk, old_ctx);
1790                 return;
1791         }
1792
1793         new_ctx->conn_finished = 1;
1794         new_ctx->icsk_af_ops = old_ctx->icsk_af_ops;
1795         new_ctx->tcp_state_change = old_ctx->tcp_state_change;
1796         new_ctx->tcp_error_report = old_ctx->tcp_error_report;
1797         new_ctx->rel_write_seq = 1;
1798         new_ctx->tcp_sock = newsk;
1799
1800         if (subflow_req->mp_capable) {
1801                 /* see comments in subflow_syn_recv_sock(), MPTCP connection
1802                  * is fully established only after we receive the remote key
1803                  */
1804                 new_ctx->mp_capable = 1;
1805                 new_ctx->local_key = subflow_req->local_key;
1806                 new_ctx->token = subflow_req->token;
1807                 new_ctx->ssn_offset = subflow_req->ssn_offset;
1808                 new_ctx->idsn = subflow_req->idsn;
1809
1810                 /* this is the first subflow, id is always 0 */
1811                 new_ctx->local_id_valid = 1;
1812         } else if (subflow_req->mp_join) {
1813                 new_ctx->ssn_offset = subflow_req->ssn_offset;
1814                 new_ctx->mp_join = 1;
1815                 new_ctx->fully_established = 1;
1816                 new_ctx->backup = subflow_req->backup;
1817                 new_ctx->remote_id = subflow_req->remote_id;
1818                 new_ctx->token = subflow_req->token;
1819                 new_ctx->thmac = subflow_req->thmac;
1820
1821                 /* the subflow req id is valid, fetched via subflow_check_req()
1822                  * and subflow_token_join_request()
1823                  */
1824                 subflow_set_local_id(new_ctx, subflow_req->local_id);
1825         }
1826 }
1827
1828 static void tcp_release_cb_override(struct sock *ssk)
1829 {
1830         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
1831
1832         if (mptcp_subflow_has_delegated_action(subflow))
1833                 mptcp_subflow_process_delegated(ssk);
1834
1835         tcp_release_cb(ssk);
1836 }
1837
1838 static struct tcp_ulp_ops subflow_ulp_ops __read_mostly = {
1839         .name           = "mptcp",
1840         .owner          = THIS_MODULE,
1841         .init           = subflow_ulp_init,
1842         .release        = subflow_ulp_release,
1843         .clone          = subflow_ulp_clone,
1844 };
1845
1846 static int subflow_ops_init(struct request_sock_ops *subflow_ops)
1847 {
1848         subflow_ops->obj_size = sizeof(struct mptcp_subflow_request_sock);
1849         subflow_ops->slab_name = "request_sock_subflow";
1850
1851         subflow_ops->slab = kmem_cache_create(subflow_ops->slab_name,
1852                                               subflow_ops->obj_size, 0,
1853                                               SLAB_ACCOUNT |
1854                                               SLAB_TYPESAFE_BY_RCU,
1855                                               NULL);
1856         if (!subflow_ops->slab)
1857                 return -ENOMEM;
1858
1859         subflow_ops->destructor = subflow_req_destructor;
1860
1861         return 0;
1862 }
1863
1864 void __init mptcp_subflow_init(void)
1865 {
1866         mptcp_subflow_request_sock_ops = tcp_request_sock_ops;
1867         if (subflow_ops_init(&mptcp_subflow_request_sock_ops) != 0)
1868                 panic("MPTCP: failed to init subflow request sock ops\n");
1869
1870         subflow_request_sock_ipv4_ops = tcp_request_sock_ipv4_ops;
1871         subflow_request_sock_ipv4_ops.route_req = subflow_v4_route_req;
1872
1873         subflow_specific = ipv4_specific;
1874         subflow_specific.conn_request = subflow_v4_conn_request;
1875         subflow_specific.syn_recv_sock = subflow_syn_recv_sock;
1876         subflow_specific.sk_rx_dst_set = subflow_finish_connect;
1877         subflow_specific.rebuild_header = subflow_rebuild_header;
1878
1879         tcp_prot_override = tcp_prot;
1880         tcp_prot_override.release_cb = tcp_release_cb_override;
1881
1882 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1883         subflow_request_sock_ipv6_ops = tcp_request_sock_ipv6_ops;
1884         subflow_request_sock_ipv6_ops.route_req = subflow_v6_route_req;
1885
1886         subflow_v6_specific = ipv6_specific;
1887         subflow_v6_specific.conn_request = subflow_v6_conn_request;
1888         subflow_v6_specific.syn_recv_sock = subflow_syn_recv_sock;
1889         subflow_v6_specific.sk_rx_dst_set = subflow_finish_connect;
1890         subflow_v6_specific.rebuild_header = subflow_v6_rebuild_header;
1891
1892         subflow_v6m_specific = subflow_v6_specific;
1893         subflow_v6m_specific.queue_xmit = ipv4_specific.queue_xmit;
1894         subflow_v6m_specific.send_check = ipv4_specific.send_check;
1895         subflow_v6m_specific.net_header_len = ipv4_specific.net_header_len;
1896         subflow_v6m_specific.mtu_reduced = ipv4_specific.mtu_reduced;
1897         subflow_v6m_specific.net_frag_header_len = 0;
1898         subflow_v6m_specific.rebuild_header = subflow_rebuild_header;
1899
1900         tcpv6_prot_override = tcpv6_prot;
1901         tcpv6_prot_override.release_cb = tcp_release_cb_override;
1902 #endif
1903
1904         mptcp_diag_subflow_init(&subflow_ulp_ops);
1905
1906         if (tcp_register_ulp(&subflow_ulp_ops) != 0)
1907                 panic("MPTCP: failed to register subflows to ULP\n");
1908 }