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/sha.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 #endif
  22 #include <net/mptcp.h>
  23 #include <uapi/linux/mptcp.h>
  24 #include "protocol.h"
  25 #include "mib.h"
  26
  27 static void SUBFLOW_REQ_INC_STATS(struct request_sock *req,
  28                                   enum linux_mptcp_mib_field field)
  29 {
  30         MPTCP_INC_STATS(sock_net(req_to_sk(req)), field);
  31 }
  32
  33 static void subflow_req_destructor(struct request_sock *req)
  34 {
  35         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
  36
  37         pr_debug("subflow_req=%p", subflow_req);
  38
  39         if (subflow_req->msk)
  40                 sock_put((struct sock *)subflow_req->msk);
  41
  42         mptcp_token_destroy_request(req);
  43 }
  44
  45 static void subflow_generate_hmac(u64 key1, u64 key2, u32 nonce1, u32 nonce2,
  46                                   void *hmac)
  47 {
  48         u8 msg[8];
  49
  50         put_unaligned_be32(nonce1, &msg[0]);
  51         put_unaligned_be32(nonce2, &msg[4]);
  52
  53         mptcp_crypto_hmac_sha(key1, key2, msg, 8, hmac);
  54 }
  55
  56 static bool mptcp_can_accept_new_subflow(const struct mptcp_sock *msk)
  57 {
  58         return mptcp_is_fully_established((void *)msk) &&
  59                READ_ONCE(msk->pm.accept_subflow);
  60 }
  61
  62 /* validate received token and create truncated hmac and nonce for SYN-ACK */
  63 static struct mptcp_sock *subflow_token_join_request(struct request_sock *req,
  64                                                      const struct sk_buff *skb)
  65 {
  66         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
  67         u8 hmac[SHA256_DIGEST_SIZE];
  68         struct mptcp_sock *msk;
  69         int local_id;
  70
  71         msk = mptcp_token_get_sock(sock_net(req_to_sk(req)), subflow_req->token);
  72         if (!msk) {
  73                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINNOTOKEN);
  74                 return NULL;
  75         }
  76
  77         local_id = mptcp_pm_get_local_id(msk, (struct sock_common *)req);
  78         if (local_id < 0) {
  79                 sock_put((struct sock *)msk);
  80                 return NULL;
  81         }
  82         subflow_req->local_id = local_id;
  83
  84         get_random_bytes(&subflow_req->local_nonce, sizeof(u32));
  85
  86         subflow_generate_hmac(msk->local_key, msk->remote_key,
  87                               subflow_req->local_nonce,
  88                               subflow_req->remote_nonce, hmac);
  89
  90         subflow_req->thmac = get_unaligned_be64(hmac);
  91         return msk;
  92 }
  93
  94 static int __subflow_init_req(struct request_sock *req, const struct sock *sk_listener)
  95 {
  96         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
  97
  98         subflow_req->mp_capable = 0;
  99         subflow_req->mp_join = 0;
 100         subflow_req->msk = NULL;
 101         mptcp_token_init_request(req);
 102
 103 #ifdef CONFIG_TCP_MD5SIG
 104         /* no MPTCP if MD5SIG is enabled on this socket or we may run out of
 105          * TCP option space.
 106          */
 107         if (rcu_access_pointer(tcp_sk(sk_listener)->md5sig_info))
 108                 return -EINVAL;
 109 #endif
 110
 111         return 0;
 112 }
 113
 114 static void subflow_init_req(struct request_sock *req,
 115                              const struct sock *sk_listener,
 116                              struct sk_buff *skb)
 117 {
 118         struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
 119         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 120         struct mptcp_options_received mp_opt;
 121         int ret;
 122
 123         pr_debug("subflow_req=%p, listener=%p", subflow_req, listener);
 124
 125         ret = __subflow_init_req(req, sk_listener);
 126         if (ret)
 127                 return;
 128
 129         mptcp_get_options(skb, &mp_opt);
 130
 131         if (mp_opt.mp_capable) {
 132                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVE);
 133
 134                 if (mp_opt.mp_join)
 135                         return;
 136         } else if (mp_opt.mp_join) {
 137                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNRX);
 138         }
 139
 140         if (mp_opt.mp_capable && listener->request_mptcp) {
 141                 int err, retries = 4;
 142
 143                 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
 144 again:
 145                 do {
 146                         get_random_bytes(&subflow_req->local_key, sizeof(subflow_req->local_key));
 147                 } while (subflow_req->local_key == 0);
 148
 149                 if (unlikely(req->syncookie)) {
 150                         mptcp_crypto_key_sha(subflow_req->local_key,
 151                                              &subflow_req->token,
 152                                              &subflow_req->idsn);
 153                         if (mptcp_token_exists(subflow_req->token)) {
 154                                 if (retries-- > 0)
 155                                         goto again;
 156                         } else {
 157                                 subflow_req->mp_capable = 1;
 158                         }
 159                         return;
 160                 }
 161
 162                 err = mptcp_token_new_request(req);
 163                 if (err == 0)
 164                         subflow_req->mp_capable = 1;
 165                 else if (retries-- > 0)
 166                         goto again;
 167
 168         } else if (mp_opt.mp_join && listener->request_mptcp) {
 169                 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
 170                 subflow_req->mp_join = 1;
 171                 subflow_req->backup = mp_opt.backup;
 172                 subflow_req->remote_id = mp_opt.join_id;
 173                 subflow_req->token = mp_opt.token;
 174                 subflow_req->remote_nonce = mp_opt.nonce;
 175                 subflow_req->msk = subflow_token_join_request(req, skb);
 176
 177                 if (unlikely(req->syncookie) && subflow_req->msk) {
 178                         if (mptcp_can_accept_new_subflow(subflow_req->msk))
 179                                 subflow_init_req_cookie_join_save(subflow_req, skb);
 180                 }
 181
 182                 pr_debug("token=%u, remote_nonce=%u msk=%p", subflow_req->token,
 183                          subflow_req->remote_nonce, subflow_req->msk);
 184         }
 185 }
 186
 187 int mptcp_subflow_init_cookie_req(struct request_sock *req,
 188                                   const struct sock *sk_listener,
 189                                   struct sk_buff *skb)
 190 {
 191         struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
 192         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 193         struct mptcp_options_received mp_opt;
 194         int err;
 195
 196         err = __subflow_init_req(req, sk_listener);
 197         if (err)
 198                 return err;
 199
 200         mptcp_get_options(skb, &mp_opt);
 201
 202         if (mp_opt.mp_capable && mp_opt.mp_join)
 203                 return -EINVAL;
 204
 205         if (mp_opt.mp_capable && listener->request_mptcp) {
 206                 if (mp_opt.sndr_key == 0)
 207                         return -EINVAL;
 208
 209                 subflow_req->local_key = mp_opt.rcvr_key;
 210                 err = mptcp_token_new_request(req);
 211                 if (err)
 212                         return err;
 213
 214                 subflow_req->mp_capable = 1;
 215                 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
 216         } else if (mp_opt.mp_join && listener->request_mptcp) {
 217                 if (!mptcp_token_join_cookie_init_state(subflow_req, skb))
 218                         return -EINVAL;
 219
 220                 if (mptcp_can_accept_new_subflow(subflow_req->msk))
 221                         subflow_req->mp_join = 1;
 222
 223                 subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
 224         }
 225
 226         return 0;
 227 }
 228 EXPORT_SYMBOL_GPL(mptcp_subflow_init_cookie_req);
 229
 230 static void subflow_v4_init_req(struct request_sock *req,
 231                                 const struct sock *sk_listener,
 232                                 struct sk_buff *skb)
 233 {
 234         tcp_rsk(req)->is_mptcp = 1;
 235
 236         tcp_request_sock_ipv4_ops.init_req(req, sk_listener, skb);
 237
 238         subflow_init_req(req, sk_listener, skb);
 239 }
 240
 241 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 242 static void subflow_v6_init_req(struct request_sock *req,
 243                                 const struct sock *sk_listener,
 244                                 struct sk_buff *skb)
 245 {
 246         tcp_rsk(req)->is_mptcp = 1;
 247
 248         tcp_request_sock_ipv6_ops.init_req(req, sk_listener, skb);
 249
 250         subflow_init_req(req, sk_listener, skb);
 251 }
 252 #endif
 253
 254 /* validate received truncated hmac and create hmac for third ACK */
 255 static bool subflow_thmac_valid(struct mptcp_subflow_context *subflow)
 256 {
 257         u8 hmac[SHA256_DIGEST_SIZE];
 258         u64 thmac;
 259
 260         subflow_generate_hmac(subflow->remote_key, subflow->local_key,
 261                               subflow->remote_nonce, subflow->local_nonce,
 262                               hmac);
 263
 264         thmac = get_unaligned_be64(hmac);
 265         pr_debug("subflow=%p, token=%u, thmac=%llu, subflow->thmac=%llu\n",
 266                  subflow, subflow->token,
 267                  (unsigned long long)thmac,
 268                  (unsigned long long)subflow->thmac);
 269
 270         return thmac == subflow->thmac;
 271 }
 272
 273 void mptcp_subflow_reset(struct sock *ssk)
 274 {
 275         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 276         struct sock *sk = subflow->conn;
 277
 278         tcp_send_active_reset(ssk, GFP_ATOMIC);
 279         tcp_done(ssk);
 280         if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags) &&
 281             schedule_work(&mptcp_sk(sk)->work))
 282                 sock_hold(sk);
 283 }
 284
 285 static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 286 {
 287         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 288         struct mptcp_options_received mp_opt;
 289         struct sock *parent = subflow->conn;
 290
 291         subflow->icsk_af_ops->sk_rx_dst_set(sk, skb);
 292
 293         if (inet_sk_state_load(parent) == TCP_SYN_SENT) {
 294                 inet_sk_state_store(parent, TCP_ESTABLISHED);
 295                 parent->sk_state_change(parent);
 296         }
 297
 298         /* be sure no special action on any packet other than syn-ack */
 299         if (subflow->conn_finished)
 300                 return;
 301
 302         subflow->rel_write_seq = 1;
 303         subflow->conn_finished = 1;
 304         subflow->ssn_offset = TCP_SKB_CB(skb)->seq;
 305         pr_debug("subflow=%p synack seq=%x", subflow, subflow->ssn_offset);
 306
 307         mptcp_get_options(skb, &mp_opt);
 308         if (subflow->request_mptcp) {
 309                 if (!mp_opt.mp_capable) {
 310                         MPTCP_INC_STATS(sock_net(sk),
 311                                         MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
 312                         mptcp_do_fallback(sk);
 313                         pr_fallback(mptcp_sk(subflow->conn));
 314                         goto fallback;
 315                 }
 316
 317                 subflow->mp_capable = 1;
 318                 subflow->can_ack = 1;
 319                 subflow->remote_key = mp_opt.sndr_key;
 320                 pr_debug("subflow=%p, remote_key=%llu", subflow,
 321                          subflow->remote_key);
 322                 mptcp_finish_connect(sk);
 323         } else if (subflow->request_join) {
 324                 u8 hmac[SHA256_DIGEST_SIZE];
 325
 326                 if (!mp_opt.mp_join)
 327                         goto do_reset;
 328
 329                 subflow->thmac = mp_opt.thmac;
 330                 subflow->remote_nonce = mp_opt.nonce;
 331                 pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u", subflow,
 332                          subflow->thmac, subflow->remote_nonce);
 333
 334                 if (!subflow_thmac_valid(subflow)) {
 335                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINACKMAC);
 336                         goto do_reset;
 337                 }
 338
 339                 if (!mptcp_finish_join(sk))
 340                         goto do_reset;
 341
 342                 subflow_generate_hmac(subflow->local_key, subflow->remote_key,
 343                                       subflow->local_nonce,
 344                                       subflow->remote_nonce,
 345                                       hmac);
 346                 memcpy(subflow->hmac, hmac, MPTCPOPT_HMAC_LEN);
 347
 348                 subflow->mp_join = 1;
 349                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKRX);
 350         } else if (mptcp_check_fallback(sk)) {
 351 fallback:
 352                 mptcp_rcv_space_init(mptcp_sk(parent), sk);
 353         }
 354         return;
 355
 356 do_reset:
 357         mptcp_subflow_reset(sk);
 358 }
 359
 360 static struct request_sock_ops mptcp_subflow_v4_request_sock_ops __ro_after_init;
 361 static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops __ro_after_init;
 362
 363 static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 364 {
 365         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 366
 367         pr_debug("subflow=%p", subflow);
 368
 369         /* Never answer to SYNs sent to broadcast or multicast */
 370         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 371                 goto drop;
 372
 373         return tcp_conn_request(&mptcp_subflow_v4_request_sock_ops,
 374                                 &subflow_request_sock_ipv4_ops,
 375                                 sk, skb);
 376 drop:
 377         tcp_listendrop(sk);
 378         return 0;
 379 }
 380
 381 static void subflow_v4_req_destructor(struct request_sock *req)
 382 {
 383         subflow_req_destructor(req);
 384         tcp_request_sock_ops.destructor(req);
 385 }
 386
 387 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 388 static struct request_sock_ops mptcp_subflow_v6_request_sock_ops __ro_after_init;
 389 static struct tcp_request_sock_ops subflow_request_sock_ipv6_ops __ro_after_init;
 390 static struct inet_connection_sock_af_ops subflow_v6_specific __ro_after_init;
 391 static struct inet_connection_sock_af_ops subflow_v6m_specific __ro_after_init;
 392
 393 static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 394 {
 395         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 396
 397         pr_debug("subflow=%p", subflow);
 398
 399         if (skb->protocol == htons(ETH_P_IP))
 400                 return subflow_v4_conn_request(sk, skb);
 401
 402         if (!ipv6_unicast_destination(skb))
 403                 goto drop;
 404
 405         if (ipv6_addr_v4mapped(&ipv6_hdr(skb)->saddr)) {
 406                 __IP6_INC_STATS(sock_net(sk), NULL, IPSTATS_MIB_INHDRERRORS);
 407                 return 0;
 408         }
 409
 410         return tcp_conn_request(&mptcp_subflow_v6_request_sock_ops,
 411                                 &subflow_request_sock_ipv6_ops, sk, skb);
 412
 413 drop:
 414         tcp_listendrop(sk);
 415         return 0; /* don't send reset */
 416 }
 417
 418 static void subflow_v6_req_destructor(struct request_sock *req)
 419 {
 420         subflow_req_destructor(req);
 421         tcp6_request_sock_ops.destructor(req);
 422 }
 423 #endif
 424
 425 struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
 426                                                struct sock *sk_listener,
 427                                                bool attach_listener)
 428 {
 429         if (ops->family == AF_INET)
 430                 ops = &mptcp_subflow_v4_request_sock_ops;
 431 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 432         else if (ops->family == AF_INET6)
 433                 ops = &mptcp_subflow_v6_request_sock_ops;
 434 #endif
 435
 436         return inet_reqsk_alloc(ops, sk_listener, attach_listener);
 437 }
 438 EXPORT_SYMBOL(mptcp_subflow_reqsk_alloc);
 439
 440 /* validate hmac received in third ACK */
 441 static bool subflow_hmac_valid(const struct request_sock *req,
 442                                const struct mptcp_options_received *mp_opt)
 443 {
 444         const struct mptcp_subflow_request_sock *subflow_req;
 445         u8 hmac[SHA256_DIGEST_SIZE];
 446         struct mptcp_sock *msk;
 447
 448         subflow_req = mptcp_subflow_rsk(req);
 449         msk = subflow_req->msk;
 450         if (!msk)
 451                 return false;
 452
 453         subflow_generate_hmac(msk->remote_key, msk->local_key,
 454                               subflow_req->remote_nonce,
 455                               subflow_req->local_nonce, hmac);
 456
 457         return !crypto_memneq(hmac, mp_opt->hmac, MPTCPOPT_HMAC_LEN);
 458 }
 459
 460 static void mptcp_sock_destruct(struct sock *sk)
 461 {
 462         /* if new mptcp socket isn't accepted, it is free'd
 463          * from the tcp listener sockets request queue, linked
 464          * from req->sk.  The tcp socket is released.
 465          * This calls the ULP release function which will
 466          * also remove the mptcp socket, via
 467          * sock_put(ctx->conn).
 468          *
 469          * Problem is that the mptcp socket will be in
 470          * ESTABLISHED state and will not have the SOCK_DEAD flag.
 471          * Both result in warnings from inet_sock_destruct.
 472          */
 473         if ((1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
 474                 sk->sk_state = TCP_CLOSE;
 475                 WARN_ON_ONCE(sk->sk_socket);
 476                 sock_orphan(sk);
 477         }
 478
 479         mptcp_destroy_common(mptcp_sk(sk));
 480         inet_sock_destruct(sk);
 481 }
 482
 483 static void mptcp_force_close(struct sock *sk)
 484 {
 485         inet_sk_state_store(sk, TCP_CLOSE);
 486         sk_common_release(sk);
 487 }
 488
 489 static void subflow_ulp_fallback(struct sock *sk,
 490                                  struct mptcp_subflow_context *old_ctx)
 491 {
 492         struct inet_connection_sock *icsk = inet_csk(sk);
 493
 494         mptcp_subflow_tcp_fallback(sk, old_ctx);
 495         icsk->icsk_ulp_ops = NULL;
 496         rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
 497         tcp_sk(sk)->is_mptcp = 0;
 498 }
 499
 500 static void subflow_drop_ctx(struct sock *ssk)
 501 {
 502         struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
 503
 504         if (!ctx)
 505                 return;
 506
 507         subflow_ulp_fallback(ssk, ctx);
 508         if (ctx->conn)
 509                 sock_put(ctx->conn);
 510
 511         kfree_rcu(ctx, rcu);
 512 }
 513
 514 void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow,
 515                                      struct mptcp_options_received *mp_opt)
 516 {
 517         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 518
 519         subflow->remote_key = mp_opt->sndr_key;
 520         subflow->fully_established = 1;
 521         subflow->can_ack = 1;
 522         WRITE_ONCE(msk->fully_established, true);
 523 }
 524
 525 static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 526                                           struct sk_buff *skb,
 527                                           struct request_sock *req,
 528                                           struct dst_entry *dst,
 529                                           struct request_sock *req_unhash,
 530                                           bool *own_req)
 531 {
 532         struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk);
 533         struct mptcp_subflow_request_sock *subflow_req;
 534         struct mptcp_options_received mp_opt;
 535         bool fallback, fallback_is_fatal;
 536         struct sock *new_msk = NULL;
 537         struct sock *child;
 538
 539         pr_debug("listener=%p, req=%p, conn=%p", listener, req, listener->conn);
 540
 541         /* After child creation we must look for 'mp_capable' even when options
 542          * are not parsed
 543          */
 544         mp_opt.mp_capable = 0;
 545
 546         /* hopefully temporary handling for MP_JOIN+syncookie */
 547         subflow_req = mptcp_subflow_rsk(req);
 548         fallback_is_fatal = tcp_rsk(req)->is_mptcp && subflow_req->mp_join;
 549         fallback = !tcp_rsk(req)->is_mptcp;
 550         if (fallback)
 551                 goto create_child;
 552
 553         /* if the sk is MP_CAPABLE, we try to fetch the client key */
 554         if (subflow_req->mp_capable) {
 555                 /* we can receive and accept an in-window, out-of-order pkt,
 556                  * which may not carry the MP_CAPABLE opt even on mptcp enabled
 557                  * paths: always try to extract the peer key, and fallback
 558                  * for packets missing it.
 559                  * Even OoO DSS packets coming legitly after dropped or
 560                  * reordered MPC will cause fallback, but we don't have other
 561                  * options.
 562                  */
 563                 mptcp_get_options(skb, &mp_opt);
 564                 if (!mp_opt.mp_capable) {
 565                         fallback = true;
 566                         goto create_child;
 567                 }
 568
 569                 new_msk = mptcp_sk_clone(listener->conn, &mp_opt, req);
 570                 if (!new_msk)
 571                         fallback = true;
 572         } else if (subflow_req->mp_join) {
 573                 mptcp_get_options(skb, &mp_opt);
 574                 if (!mp_opt.mp_join || !subflow_hmac_valid(req, &mp_opt) ||
 575                     !mptcp_can_accept_new_subflow(subflow_req->msk)) {
 576                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKMAC);
 577                         fallback = true;
 578                 }
 579         }
 580
 581 create_child:
 582         child = listener->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
 583                                                      req_unhash, own_req);
 584
 585         if (child && *own_req) {
 586                 struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);
 587
 588                 tcp_rsk(req)->drop_req = false;
 589
 590                 /* we need to fallback on ctx allocation failure and on pre-reqs
 591                  * checking above. In the latter scenario we additionally need
 592                  * to reset the context to non MPTCP status.
 593                  */
 594                 if (!ctx || fallback) {
 595                         if (fallback_is_fatal)
 596                                 goto dispose_child;
 597
 598                         if (fallback)
 599                                 SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
 600
 601                         subflow_drop_ctx(child);
 602                         goto out;
 603                 }
 604
 605                 if (ctx->mp_capable) {
 606                         /* this can't race with mptcp_close(), as the msk is
 607                          * not yet exposted to user-space
 608                          */
 609                         inet_sk_state_store((void *)new_msk, TCP_ESTABLISHED);
 610
 611                         /* new mpc subflow takes ownership of the newly
 612                          * created mptcp socket
 613                          */
 614                         new_msk->sk_destruct = mptcp_sock_destruct;
 615                         mptcp_pm_new_connection(mptcp_sk(new_msk), 1);
 616                         mptcp_token_accept(subflow_req, mptcp_sk(new_msk));
 617                         ctx->conn = new_msk;
 618                         new_msk = NULL;
 619
 620                         /* with OoO packets we can reach here without ingress
 621                          * mpc option
 622                          */
 623                         if (mp_opt.mp_capable)
 624                                 mptcp_subflow_fully_established(ctx, &mp_opt);
 625                 } else if (ctx->mp_join) {
 626                         struct mptcp_sock *owner;
 627
 628                         owner = subflow_req->msk;
 629                         if (!owner)
 630                                 goto dispose_child;
 631
 632                         /* move the msk reference ownership to the subflow */
 633                         subflow_req->msk = NULL;
 634                         ctx->conn = (struct sock *)owner;
 635                         if (!mptcp_finish_join(child))
 636                                 goto dispose_child;
 637
 638                         SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKRX);
 639                         tcp_rsk(req)->drop_req = true;
 640                 }
 641         }
 642
 643 out:
 644         /* dispose of the left over mptcp master, if any */
 645         if (unlikely(new_msk))
 646                 mptcp_force_close(new_msk);
 647
 648         /* check for expected invariant - should never trigger, just help
 649          * catching eariler subtle bugs
 650          */
 651         WARN_ON_ONCE(child && *own_req && tcp_sk(child)->is_mptcp &&
 652                      (!mptcp_subflow_ctx(child) ||
 653                       !mptcp_subflow_ctx(child)->conn));
 654         return child;
 655
 656 dispose_child:
 657         subflow_drop_ctx(child);
 658         tcp_rsk(req)->drop_req = true;
 659         inet_csk_prepare_for_destroy_sock(child);
 660         tcp_done(child);
 661         req->rsk_ops->send_reset(sk, skb);
 662
 663         /* The last child reference will be released by the caller */
 664         return child;
 665 }
 666
 667 static struct inet_connection_sock_af_ops subflow_specific __ro_after_init;
 668
 669 enum mapping_status {
 670         MAPPING_OK,
 671         MAPPING_INVALID,
 672         MAPPING_EMPTY,
 673         MAPPING_DATA_FIN,
 674         MAPPING_DUMMY
 675 };
 676
 677 static u64 expand_seq(u64 old_seq, u16 old_data_len, u64 seq)
 678 {
 679         if ((u32)seq == (u32)old_seq)
 680                 return old_seq;
 681
 682         /* Assume map covers data not mapped yet. */
 683         return seq | ((old_seq + old_data_len + 1) & GENMASK_ULL(63, 32));
 684 }
 685
 686 static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
 687 {
 688         pr_debug("Bad mapping: ssn=%d map_seq=%d map_data_len=%d",
 689                  ssn, subflow->map_subflow_seq, subflow->map_data_len);
 690 }
 691
 692 static bool skb_is_fully_mapped(struct sock *ssk, struct sk_buff *skb)
 693 {
 694         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 695         unsigned int skb_consumed;
 696
 697         skb_consumed = tcp_sk(ssk)->copied_seq - TCP_SKB_CB(skb)->seq;
 698         if (WARN_ON_ONCE(skb_consumed >= skb->len))
 699                 return true;
 700
 701         return skb->len - skb_consumed <= subflow->map_data_len -
 702                                           mptcp_subflow_get_map_offset(subflow);
 703 }
 704
 705 static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
 706 {
 707         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 708         u32 ssn = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
 709
 710         if (unlikely(before(ssn, subflow->map_subflow_seq))) {
 711                 /* Mapping covers data later in the subflow stream,
 712                  * currently unsupported.
 713                  */
 714                 dbg_bad_map(subflow, ssn);
 715                 return false;
 716         }
 717         if (unlikely(!before(ssn, subflow->map_subflow_seq +
 718                                   subflow->map_data_len))) {
 719                 /* Mapping does covers past subflow data, invalid */
 720                 dbg_bad_map(subflow, ssn);
 721                 return false;
 722         }
 723         return true;
 724 }
 725
 726 static enum mapping_status get_mapping_status(struct sock *ssk,
 727                                               struct mptcp_sock *msk)
 728 {
 729         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 730         struct mptcp_ext *mpext;
 731         struct sk_buff *skb;
 732         u16 data_len;
 733         u64 map_seq;
 734
 735         skb = skb_peek(&ssk->sk_receive_queue);
 736         if (!skb)
 737                 return MAPPING_EMPTY;
 738
 739         if (mptcp_check_fallback(ssk))
 740                 return MAPPING_DUMMY;
 741
 742         mpext = mptcp_get_ext(skb);
 743         if (!mpext || !mpext->use_map) {
 744                 if (!subflow->map_valid && !skb->len) {
 745                         /* the TCP stack deliver 0 len FIN pkt to the receive
 746                          * queue, that is the only 0len pkts ever expected here,
 747                          * and we can admit no mapping only for 0 len pkts
 748                          */
 749                         if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
 750                                 WARN_ONCE(1, "0len seq %d:%d flags %x",
 751                                           TCP_SKB_CB(skb)->seq,
 752                                           TCP_SKB_CB(skb)->end_seq,
 753                                           TCP_SKB_CB(skb)->tcp_flags);
 754                         sk_eat_skb(ssk, skb);
 755                         return MAPPING_EMPTY;
 756                 }
 757
 758                 if (!subflow->map_valid)
 759                         return MAPPING_INVALID;
 760
 761                 goto validate_seq;
 762         }
 763
 764         pr_debug("seq=%llu is64=%d ssn=%u data_len=%u data_fin=%d",
 765                  mpext->data_seq, mpext->dsn64, mpext->subflow_seq,
 766                  mpext->data_len, mpext->data_fin);
 767
 768         data_len = mpext->data_len;
 769         if (data_len == 0) {
 770                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX);
 771                 return MAPPING_INVALID;
 772         }
 773
 774         if (mpext->data_fin == 1) {
 775                 if (data_len == 1) {
 776                         bool updated = mptcp_update_rcv_data_fin(msk, mpext->data_seq,
 777                                                                  mpext->dsn64);
 778                         pr_debug("DATA_FIN with no payload seq=%llu", mpext->data_seq);
 779                         if (subflow->map_valid) {
 780                                 /* A DATA_FIN might arrive in a DSS
 781                                  * option before the previous mapping
 782                                  * has been fully consumed. Continue
 783                                  * handling the existing mapping.
 784                                  */
 785                                 skb_ext_del(skb, SKB_EXT_MPTCP);
 786                                 return MAPPING_OK;
 787                         } else {
 788                                 if (updated && schedule_work(&msk->work))
 789                                         sock_hold((struct sock *)msk);
 790
 791                                 return MAPPING_DATA_FIN;
 792                         }
 793                 } else {
 794                         u64 data_fin_seq = mpext->data_seq + data_len - 1;
 795
 796                         /* If mpext->data_seq is a 32-bit value, data_fin_seq
 797                          * must also be limited to 32 bits.
 798                          */
 799                         if (!mpext->dsn64)
 800                                 data_fin_seq &= GENMASK_ULL(31, 0);
 801
 802                         mptcp_update_rcv_data_fin(msk, data_fin_seq, mpext->dsn64);
 803                         pr_debug("DATA_FIN with mapping seq=%llu dsn64=%d",
 804                                  data_fin_seq, mpext->dsn64);
 805                 }
 806
 807                 /* Adjust for DATA_FIN using 1 byte of sequence space */
 808                 data_len--;
 809         }
 810
 811         if (!mpext->dsn64) {
 812                 map_seq = expand_seq(subflow->map_seq, subflow->map_data_len,
 813                                      mpext->data_seq);
 814                 pr_debug("expanded seq=%llu", subflow->map_seq);
 815         } else {
 816                 map_seq = mpext->data_seq;
 817         }
 818         WRITE_ONCE(mptcp_sk(subflow->conn)->use_64bit_ack, !!mpext->dsn64);
 819
 820         if (subflow->map_valid) {
 821                 /* Allow replacing only with an identical map */
 822                 if (subflow->map_seq == map_seq &&
 823                     subflow->map_subflow_seq == mpext->subflow_seq &&
 824                     subflow->map_data_len == data_len) {
 825                         skb_ext_del(skb, SKB_EXT_MPTCP);
 826                         return MAPPING_OK;
 827                 }
 828
 829                 /* If this skb data are fully covered by the current mapping,
 830                  * the new map would need caching, which is not supported
 831                  */
 832                 if (skb_is_fully_mapped(ssk, skb)) {
 833                         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DSSNOMATCH);
 834                         return MAPPING_INVALID;
 835                 }
 836
 837                 /* will validate the next map after consuming the current one */
 838                 return MAPPING_OK;
 839         }
 840
 841         subflow->map_seq = map_seq;
 842         subflow->map_subflow_seq = mpext->subflow_seq;
 843         subflow->map_data_len = data_len;
 844         subflow->map_valid = 1;
 845         subflow->mpc_map = mpext->mpc_map;
 846         pr_debug("new map seq=%llu subflow_seq=%u data_len=%u",
 847                  subflow->map_seq, subflow->map_subflow_seq,
 848                  subflow->map_data_len);
 849
 850 validate_seq:
 851         /* we revalidate valid mapping on new skb, because we must ensure
 852          * the current skb is completely covered by the available mapping
 853          */
 854         if (!validate_mapping(ssk, skb))
 855                 return MAPPING_INVALID;
 856
 857         skb_ext_del(skb, SKB_EXT_MPTCP);
 858         return MAPPING_OK;
 859 }
 860
 861 static void mptcp_subflow_discard_data(struct sock *ssk, struct sk_buff *skb,
 862                                        u64 limit)
 863 {
 864         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 865         bool fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
 866         u32 incr;
 867
 868         incr = limit >= skb->len ? skb->len + fin : limit;
 869
 870         pr_debug("discarding=%d len=%d seq=%d", incr, skb->len,
 871                  subflow->map_subflow_seq);
 872         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DUPDATA);
 873         tcp_sk(ssk)->copied_seq += incr;
 874         if (!before(tcp_sk(ssk)->copied_seq, TCP_SKB_CB(skb)->end_seq))
 875                 sk_eat_skb(ssk, skb);
 876         if (mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len)
 877                 subflow->map_valid = 0;
 878         if (incr)
 879                 tcp_cleanup_rbuf(ssk, incr);
 880 }
 881
 882 static bool subflow_check_data_avail(struct sock *ssk)
 883 {
 884         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 885         enum mapping_status status;
 886         struct mptcp_sock *msk;
 887         struct sk_buff *skb;
 888
 889         pr_debug("msk=%p ssk=%p data_avail=%d skb=%p", subflow->conn, ssk,
 890                  subflow->data_avail, skb_peek(&ssk->sk_receive_queue));
 891         if (!skb_peek(&ssk->sk_receive_queue))
 892                 subflow->data_avail = 0;
 893         if (subflow->data_avail)
 894                 return true;
 895
 896         msk = mptcp_sk(subflow->conn);
 897         for (;;) {
 898                 u64 ack_seq;
 899                 u64 old_ack;
 900
 901                 status = get_mapping_status(ssk, msk);
 902                 pr_debug("msk=%p ssk=%p status=%d", msk, ssk, status);
 903                 if (status == MAPPING_INVALID) {
 904                         ssk->sk_err = EBADMSG;
 905                         goto fatal;
 906                 }
 907                 if (status == MAPPING_DUMMY) {
 908                         __mptcp_do_fallback(msk);
 909                         skb = skb_peek(&ssk->sk_receive_queue);
 910                         subflow->map_valid = 1;
 911                         subflow->map_seq = READ_ONCE(msk->ack_seq);
 912                         subflow->map_data_len = skb->len;
 913                         subflow->map_subflow_seq = tcp_sk(ssk)->copied_seq -
 914                                                    subflow->ssn_offset;
 915                         subflow->data_avail = MPTCP_SUBFLOW_DATA_AVAIL;
 916                         return true;
 917                 }
 918
 919                 if (status != MAPPING_OK)
 920                         return false;
 921
 922                 skb = skb_peek(&ssk->sk_receive_queue);
 923                 if (WARN_ON_ONCE(!skb))
 924                         return false;
 925
 926                 /* if msk lacks the remote key, this subflow must provide an
 927                  * MP_CAPABLE-based mapping
 928                  */
 929                 if (unlikely(!READ_ONCE(msk->can_ack))) {
 930                         if (!subflow->mpc_map) {
 931                                 ssk->sk_err = EBADMSG;
 932                                 goto fatal;
 933                         }
 934                         WRITE_ONCE(msk->remote_key, subflow->remote_key);
 935                         WRITE_ONCE(msk->ack_seq, subflow->map_seq);
 936                         WRITE_ONCE(msk->can_ack, true);
 937                 }
 938
 939                 old_ack = READ_ONCE(msk->ack_seq);
 940                 ack_seq = mptcp_subflow_get_mapped_dsn(subflow);
 941                 pr_debug("msk ack_seq=%llx subflow ack_seq=%llx", old_ack,
 942                          ack_seq);
 943                 if (ack_seq == old_ack) {
 944                         subflow->data_avail = MPTCP_SUBFLOW_DATA_AVAIL;
 945                         break;
 946                 } else if (after64(ack_seq, old_ack)) {
 947                         subflow->data_avail = MPTCP_SUBFLOW_OOO_DATA;
 948                         break;
 949                 }
 950
 951                 /* only accept in-sequence mapping. Old values are spurious
 952                  * retransmission
 953                  */
 954                 mptcp_subflow_discard_data(ssk, skb, old_ack - ack_seq);
 955         }
 956         return true;
 957
 958 fatal:
 959         /* fatal protocol error, close the socket */
 960         /* This barrier is coupled with smp_rmb() in tcp_poll() */
 961         smp_wmb();
 962         ssk->sk_error_report(ssk);
 963         tcp_set_state(ssk, TCP_CLOSE);
 964         tcp_send_active_reset(ssk, GFP_ATOMIC);
 965         subflow->data_avail = 0;
 966         return false;
 967 }
 968
 969 bool mptcp_subflow_data_available(struct sock *sk)
 970 {
 971         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 972
 973         /* check if current mapping is still valid */
 974         if (subflow->map_valid &&
 975             mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len) {
 976                 subflow->map_valid = 0;
 977                 subflow->data_avail = 0;
 978
 979                 pr_debug("Done with mapping: seq=%u data_len=%u",
 980                          subflow->map_subflow_seq,
 981                          subflow->map_data_len);
 982         }
 983
 984         return subflow_check_data_avail(sk);
 985 }
 986
 987 /* If ssk has an mptcp parent socket, use the mptcp rcvbuf occupancy,
 988  * not the ssk one.
 989  *
 990  * In mptcp, rwin is about the mptcp-level connection data.
 991  *
 992  * Data that is still on the ssk rx queue can thus be ignored,
 993  * as far as mptcp peer is concerened that data is still inflight.
 994  * DSS ACK is updated when skb is moved to the mptcp rx queue.
 995  */
 996 void mptcp_space(const struct sock *ssk, int *space, int *full_space)
 997 {
 998         const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 999         const struct sock *sk = subflow->conn;
1000
1001         *space = tcp_space(sk);
1002         *full_space = tcp_full_space(sk);
1003 }
1004
1005 static void subflow_data_ready(struct sock *sk)
1006 {
1007         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1008         u16 state = 1 << inet_sk_state_load(sk);
1009         struct sock *parent = subflow->conn;
1010         struct mptcp_sock *msk;
1011
1012         msk = mptcp_sk(parent);
1013         if (state & TCPF_LISTEN) {
1014                 /* MPJ subflow are removed from accept queue before reaching here,
1015                  * avoid stray wakeups
1016                  */
1017                 if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue))
1018                         return;
1019
1020                 set_bit(MPTCP_DATA_READY, &msk->flags);
1021                 parent->sk_data_ready(parent);
1022                 return;
1023         }
1024
1025         WARN_ON_ONCE(!__mptcp_check_fallback(msk) && !subflow->mp_capable &&
1026                      !subflow->mp_join && !(state & TCPF_CLOSE));
1027
1028         if (mptcp_subflow_data_available(sk))
1029                 mptcp_data_ready(parent, sk);
1030 }
1031
1032 static void subflow_write_space(struct sock *sk)
1033 {
1034         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1035         struct sock *parent = subflow->conn;
1036
1037         if (!sk_stream_is_writeable(sk))
1038                 return;
1039
1040         if (sk_stream_is_writeable(parent)) {
1041                 set_bit(MPTCP_SEND_SPACE, &mptcp_sk(parent)->flags);
1042                 smp_mb__after_atomic();
1043                 /* set SEND_SPACE before sk_stream_write_space clears NOSPACE */
1044                 sk_stream_write_space(parent);
1045         }
1046 }
1047
1048 static const struct inet_connection_sock_af_ops *
1049 subflow_default_af_ops(struct sock *sk)
1050 {
1051 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1052         if (sk->sk_family == AF_INET6)
1053                 return &subflow_v6_specific;
1054 #endif
1055         return &subflow_specific;
1056 }
1057
1058 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1059 void mptcpv6_handle_mapped(struct sock *sk, bool mapped)
1060 {
1061         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1062         struct inet_connection_sock *icsk = inet_csk(sk);
1063         const struct inet_connection_sock_af_ops *target;
1064
1065         target = mapped ? &subflow_v6m_specific : subflow_default_af_ops(sk);
1066
1067         pr_debug("subflow=%p family=%d ops=%p target=%p mapped=%d",
1068                  subflow, sk->sk_family, icsk->icsk_af_ops, target, mapped);
1069
1070         if (likely(icsk->icsk_af_ops == target))
1071                 return;
1072
1073         subflow->icsk_af_ops = icsk->icsk_af_ops;
1074         icsk->icsk_af_ops = target;
1075 }
1076 #endif
1077
1078 static void mptcp_info2sockaddr(const struct mptcp_addr_info *info,
1079                                 struct sockaddr_storage *addr)
1080 {
1081         memset(addr, 0, sizeof(*addr));
1082         addr->ss_family = info->family;
1083         if (addr->ss_family == AF_INET) {
1084                 struct sockaddr_in *in_addr = (struct sockaddr_in *)addr;
1085
1086                 in_addr->sin_addr = info->addr;
1087                 in_addr->sin_port = info->port;
1088         }
1089 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1090         else if (addr->ss_family == AF_INET6) {
1091                 struct sockaddr_in6 *in6_addr = (struct sockaddr_in6 *)addr;
1092
1093                 in6_addr->sin6_addr = info->addr6;
1094                 in6_addr->sin6_port = info->port;
1095         }
1096 #endif
1097 }
1098
1099 int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
1100                             const struct mptcp_addr_info *remote)
1101 {
1102         struct mptcp_sock *msk = mptcp_sk(sk);
1103         struct mptcp_subflow_context *subflow;
1104         struct sockaddr_storage addr;
1105         int remote_id = remote->id;
1106         int local_id = loc->id;
1107         struct socket *sf;
1108         struct sock *ssk;
1109         u32 remote_token;
1110         int addrlen;
1111         int err;
1112
1113         if (!mptcp_is_fully_established(sk))
1114                 return -ENOTCONN;
1115
1116         err = mptcp_subflow_create_socket(sk, &sf);
1117         if (err)
1118                 return err;
1119
1120         ssk = sf->sk;
1121         subflow = mptcp_subflow_ctx(ssk);
1122         do {
1123                 get_random_bytes(&subflow->local_nonce, sizeof(u32));
1124         } while (!subflow->local_nonce);
1125
1126         if (!local_id) {
1127                 err = mptcp_pm_get_local_id(msk, (struct sock_common *)ssk);
1128                 if (err < 0)
1129                         goto failed;
1130
1131                 local_id = err;
1132         }
1133
1134         subflow->remote_key = msk->remote_key;
1135         subflow->local_key = msk->local_key;
1136         subflow->token = msk->token;
1137         mptcp_info2sockaddr(loc, &addr);
1138
1139         addrlen = sizeof(struct sockaddr_in);
1140 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1141         if (loc->family == AF_INET6)
1142                 addrlen = sizeof(struct sockaddr_in6);
1143 #endif
1144         ssk->sk_bound_dev_if = loc->ifindex;
1145         err = kernel_bind(sf, (struct sockaddr *)&addr, addrlen);
1146         if (err)
1147                 goto failed;
1148
1149         mptcp_crypto_key_sha(subflow->remote_key, &remote_token, NULL);
1150         pr_debug("msk=%p remote_token=%u local_id=%d remote_id=%d", msk,
1151                  remote_token, local_id, remote_id);
1152         subflow->remote_token = remote_token;
1153         subflow->local_id = local_id;
1154         subflow->remote_id = remote_id;
1155         subflow->request_join = 1;
1156         subflow->request_bkup = !!(loc->flags & MPTCP_PM_ADDR_FLAG_BACKUP);
1157         mptcp_info2sockaddr(remote, &addr);
1158
1159         err = kernel_connect(sf, (struct sockaddr *)&addr, addrlen, O_NONBLOCK);
1160         if (err && err != -EINPROGRESS)
1161                 goto failed;
1162
1163         spin_lock_bh(&msk->join_list_lock);
1164         list_add_tail(&subflow->node, &msk->join_list);
1165         spin_unlock_bh(&msk->join_list_lock);
1166
1167         return err;
1168
1169 failed:
1170         sock_release(sf);
1171         return err;
1172 }
1173
1174 int mptcp_subflow_create_socket(struct sock *sk, struct socket **new_sock)
1175 {
1176         struct mptcp_subflow_context *subflow;
1177         struct net *net = sock_net(sk);
1178         struct socket *sf;
1179         int err;
1180
1181         /* un-accepted server sockets can reach here - on bad configuration
1182          * bail early to avoid greater trouble later
1183          */
1184         if (unlikely(!sk->sk_socket))
1185                 return -EINVAL;
1186
1187         err = sock_create_kern(net, sk->sk_family, SOCK_STREAM, IPPROTO_TCP,
1188                                &sf);
1189         if (err)
1190                 return err;
1191
1192         lock_sock(sf->sk);
1193
1194         /* kernel sockets do not by default acquire net ref, but TCP timer
1195          * needs it.
1196          */
1197         sf->sk->sk_net_refcnt = 1;
1198         get_net(net);
1199 #ifdef CONFIG_PROC_FS
1200         this_cpu_add(*net->core.sock_inuse, 1);
1201 #endif
1202         err = tcp_set_ulp(sf->sk, "mptcp");
1203         release_sock(sf->sk);
1204
1205         if (err) {
1206                 sock_release(sf);
1207                 return err;
1208         }
1209
1210         /* the newly created socket really belongs to the owning MPTCP master
1211          * socket, even if for additional subflows the allocation is performed
1212          * by a kernel workqueue. Adjust inode references, so that the
1213          * procfs/diag interaces really show this one belonging to the correct
1214          * user.
1215          */
1216         SOCK_INODE(sf)->i_ino = SOCK_INODE(sk->sk_socket)->i_ino;
1217         SOCK_INODE(sf)->i_uid = SOCK_INODE(sk->sk_socket)->i_uid;
1218         SOCK_INODE(sf)->i_gid = SOCK_INODE(sk->sk_socket)->i_gid;
1219
1220         subflow = mptcp_subflow_ctx(sf->sk);
1221         pr_debug("subflow=%p", subflow);
1222
1223         *new_sock = sf;
1224         sock_hold(sk);
1225         subflow->conn = sk;
1226
1227         return 0;
1228 }
1229
1230 static struct mptcp_subflow_context *subflow_create_ctx(struct sock *sk,
1231                                                         gfp_t priority)
1232 {
1233         struct inet_connection_sock *icsk = inet_csk(sk);
1234         struct mptcp_subflow_context *ctx;
1235
1236         ctx = kzalloc(sizeof(*ctx), priority);
1237         if (!ctx)
1238                 return NULL;
1239
1240         rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
1241         INIT_LIST_HEAD(&ctx->node);
1242
1243         pr_debug("subflow=%p", ctx);
1244
1245         ctx->tcp_sock = sk;
1246
1247         return ctx;
1248 }
1249
1250 static void __subflow_state_change(struct sock *sk)
1251 {
1252         struct socket_wq *wq;
1253
1254         rcu_read_lock();
1255         wq = rcu_dereference(sk->sk_wq);
1256         if (skwq_has_sleeper(wq))
1257                 wake_up_interruptible_all(&wq->wait);
1258         rcu_read_unlock();
1259 }
1260
1261 static bool subflow_is_done(const struct sock *sk)
1262 {
1263         return sk->sk_shutdown & RCV_SHUTDOWN || sk->sk_state == TCP_CLOSE;
1264 }
1265
1266 static void subflow_state_change(struct sock *sk)
1267 {
1268         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1269         struct sock *parent = subflow->conn;
1270
1271         __subflow_state_change(sk);
1272
1273         if (subflow_simultaneous_connect(sk)) {
1274                 mptcp_do_fallback(sk);
1275                 mptcp_rcv_space_init(mptcp_sk(parent), sk);
1276                 pr_fallback(mptcp_sk(parent));
1277                 subflow->conn_finished = 1;
1278                 if (inet_sk_state_load(parent) == TCP_SYN_SENT) {
1279                         inet_sk_state_store(parent, TCP_ESTABLISHED);
1280                         parent->sk_state_change(parent);
1281                 }
1282         }
1283
1284         /* as recvmsg() does not acquire the subflow socket for ssk selection
1285          * a fin packet carrying a DSS can be unnoticed if we don't trigger
1286          * the data available machinery here.
1287          */
1288         if (mptcp_subflow_data_available(sk))
1289                 mptcp_data_ready(parent, sk);
1290
1291         if (__mptcp_check_fallback(mptcp_sk(parent)) &&
1292             !(parent->sk_shutdown & RCV_SHUTDOWN) &&
1293             !subflow->rx_eof && subflow_is_done(sk)) {
1294                 subflow->rx_eof = 1;
1295                 mptcp_subflow_eof(parent);
1296         }
1297 }
1298
1299 static int subflow_ulp_init(struct sock *sk)
1300 {
1301         struct inet_connection_sock *icsk = inet_csk(sk);
1302         struct mptcp_subflow_context *ctx;
1303         struct tcp_sock *tp = tcp_sk(sk);
1304         int err = 0;
1305
1306         /* disallow attaching ULP to a socket unless it has been
1307          * created with sock_create_kern()
1308          */
1309         if (!sk->sk_kern_sock) {
1310                 err = -EOPNOTSUPP;
1311                 goto out;
1312         }
1313
1314         ctx = subflow_create_ctx(sk, GFP_KERNEL);
1315         if (!ctx) {
1316                 err = -ENOMEM;
1317                 goto out;
1318         }
1319
1320         pr_debug("subflow=%p, family=%d", ctx, sk->sk_family);
1321
1322         tp->is_mptcp = 1;
1323         ctx->icsk_af_ops = icsk->icsk_af_ops;
1324         icsk->icsk_af_ops = subflow_default_af_ops(sk);
1325         ctx->tcp_data_ready = sk->sk_data_ready;
1326         ctx->tcp_state_change = sk->sk_state_change;
1327         ctx->tcp_write_space = sk->sk_write_space;
1328         sk->sk_data_ready = subflow_data_ready;
1329         sk->sk_write_space = subflow_write_space;
1330         sk->sk_state_change = subflow_state_change;
1331 out:
1332         return err;
1333 }
1334
1335 static void subflow_ulp_release(struct sock *sk)
1336 {
1337         struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(sk);
1338
1339         if (!ctx)
1340                 return;
1341
1342         if (ctx->conn)
1343                 sock_put(ctx->conn);
1344
1345         kfree_rcu(ctx, rcu);
1346 }
1347
1348 static void subflow_ulp_clone(const struct request_sock *req,
1349                               struct sock *newsk,
1350                               const gfp_t priority)
1351 {
1352         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
1353         struct mptcp_subflow_context *old_ctx = mptcp_subflow_ctx(newsk);
1354         struct mptcp_subflow_context *new_ctx;
1355
1356         if (!tcp_rsk(req)->is_mptcp ||
1357             (!subflow_req->mp_capable && !subflow_req->mp_join)) {
1358                 subflow_ulp_fallback(newsk, old_ctx);
1359                 return;
1360         }
1361
1362         new_ctx = subflow_create_ctx(newsk, priority);
1363         if (!new_ctx) {
1364                 subflow_ulp_fallback(newsk, old_ctx);
1365                 return;
1366         }
1367
1368         new_ctx->conn_finished = 1;
1369         new_ctx->icsk_af_ops = old_ctx->icsk_af_ops;
1370         new_ctx->tcp_data_ready = old_ctx->tcp_data_ready;
1371         new_ctx->tcp_state_change = old_ctx->tcp_state_change;
1372         new_ctx->tcp_write_space = old_ctx->tcp_write_space;
1373         new_ctx->rel_write_seq = 1;
1374         new_ctx->tcp_sock = newsk;
1375
1376         if (subflow_req->mp_capable) {
1377                 /* see comments in subflow_syn_recv_sock(), MPTCP connection
1378                  * is fully established only after we receive the remote key
1379                  */
1380                 new_ctx->mp_capable = 1;
1381                 new_ctx->local_key = subflow_req->local_key;
1382                 new_ctx->token = subflow_req->token;
1383                 new_ctx->ssn_offset = subflow_req->ssn_offset;
1384                 new_ctx->idsn = subflow_req->idsn;
1385         } else if (subflow_req->mp_join) {
1386                 new_ctx->ssn_offset = subflow_req->ssn_offset;
1387                 new_ctx->mp_join = 1;
1388                 new_ctx->fully_established = 1;
1389                 new_ctx->backup = subflow_req->backup;
1390                 new_ctx->local_id = subflow_req->local_id;
1391                 new_ctx->remote_id = subflow_req->remote_id;
1392                 new_ctx->token = subflow_req->token;
1393                 new_ctx->thmac = subflow_req->thmac;
1394         }
1395 }
1396
1397 static struct tcp_ulp_ops subflow_ulp_ops __read_mostly = {
1398         .name           = "mptcp",
1399         .owner          = THIS_MODULE,
1400         .init           = subflow_ulp_init,
1401         .release        = subflow_ulp_release,
1402         .clone          = subflow_ulp_clone,
1403 };
1404
1405 static int subflow_ops_init(struct request_sock_ops *subflow_ops)
1406 {
1407         subflow_ops->obj_size = sizeof(struct mptcp_subflow_request_sock);
1408
1409         subflow_ops->slab = kmem_cache_create(subflow_ops->slab_name,
1410                                               subflow_ops->obj_size, 0,
1411                                               SLAB_ACCOUNT |
1412                                               SLAB_TYPESAFE_BY_RCU,
1413                                               NULL);
1414         if (!subflow_ops->slab)
1415                 return -ENOMEM;
1416
1417         return 0;
1418 }
1419
1420 void __init mptcp_subflow_init(void)
1421 {
1422         mptcp_subflow_v4_request_sock_ops = tcp_request_sock_ops;
1423         mptcp_subflow_v4_request_sock_ops.slab_name = "request_sock_subflow_v4";
1424         mptcp_subflow_v4_request_sock_ops.destructor = subflow_v4_req_destructor;
1425
1426         if (subflow_ops_init(&mptcp_subflow_v4_request_sock_ops) != 0)
1427                 panic("MPTCP: failed to init subflow v4 request sock ops\n");
1428
1429         subflow_request_sock_ipv4_ops = tcp_request_sock_ipv4_ops;
1430         subflow_request_sock_ipv4_ops.init_req = subflow_v4_init_req;
1431
1432         subflow_specific = ipv4_specific;
1433         subflow_specific.conn_request = subflow_v4_conn_request;
1434         subflow_specific.syn_recv_sock = subflow_syn_recv_sock;
1435         subflow_specific.sk_rx_dst_set = subflow_finish_connect;
1436
1437 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1438         /* In struct mptcp_subflow_request_sock, we assume the TCP request sock
1439          * structures for v4 and v6 have the same size. It should not changed in
1440          * the future but better to make sure to be warned if it is no longer
1441          * the case.
1442          */
1443         BUILD_BUG_ON(sizeof(struct tcp_request_sock) != sizeof(struct tcp6_request_sock));
1444
1445         mptcp_subflow_v6_request_sock_ops = tcp6_request_sock_ops;
1446         mptcp_subflow_v6_request_sock_ops.slab_name = "request_sock_subflow_v6";
1447         mptcp_subflow_v6_request_sock_ops.destructor = subflow_v6_req_destructor;
1448
1449         if (subflow_ops_init(&mptcp_subflow_v6_request_sock_ops) != 0)
1450                 panic("MPTCP: failed to init subflow v6 request sock ops\n");
1451
1452         subflow_request_sock_ipv6_ops = tcp_request_sock_ipv6_ops;
1453         subflow_request_sock_ipv6_ops.init_req = subflow_v6_init_req;
1454
1455         subflow_v6_specific = ipv6_specific;
1456         subflow_v6_specific.conn_request = subflow_v6_conn_request;
1457         subflow_v6_specific.syn_recv_sock = subflow_syn_recv_sock;
1458         subflow_v6_specific.sk_rx_dst_set = subflow_finish_connect;
1459
1460         subflow_v6m_specific = subflow_v6_specific;
1461         subflow_v6m_specific.queue_xmit = ipv4_specific.queue_xmit;
1462         subflow_v6m_specific.send_check = ipv4_specific.send_check;
1463         subflow_v6m_specific.net_header_len = ipv4_specific.net_header_len;
1464         subflow_v6m_specific.mtu_reduced = ipv4_specific.mtu_reduced;
1465         subflow_v6m_specific.net_frag_header_len = 0;
1466 #endif
1467
1468         mptcp_diag_subflow_init(&subflow_ulp_ops);
1469
1470         if (tcp_register_ulp(&subflow_ulp_ops) != 0)
1471                 panic("MPTCP: failed to register subflows to ULP\n");
1472 }