linux/net/ipv4/tcp_bpf.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/* Copyright (c) 2017 - 2018 Covalent IO, Inc. http://covalent.io */
   3
   4#include <linux/skmsg.h>
   5#include <linux/filter.h>
   6#include <linux/bpf.h>
   7#include <linux/init.h>
   8#include <linux/wait.h>
   9
  10#include <net/inet_common.h>
  11#include <net/tls.h>
  12
  13static int bpf_tcp_ingress(struct sock *sk, struct sk_psock *psock,
  14                           struct sk_msg *msg, u32 apply_bytes, int flags)
  15{
  16        bool apply = apply_bytes;
  17        struct scatterlist *sge;
  18        u32 size, copied = 0;
  19        struct sk_msg *tmp;
  20        int i, ret = 0;
  21
  22        tmp = kzalloc(sizeof(*tmp), __GFP_NOWARN | GFP_KERNEL);
  23        if (unlikely(!tmp))
  24                return -ENOMEM;
  25
  26        lock_sock(sk);
  27        tmp->sg.start = msg->sg.start;
  28        i = msg->sg.start;
  29        do {
  30                sge = sk_msg_elem(msg, i);
  31                size = (apply && apply_bytes < sge->length) ?
  32                        apply_bytes : sge->length;
  33                if (!sk_wmem_schedule(sk, size)) {
  34                        if (!copied)
  35                                ret = -ENOMEM;
  36                        break;
  37                }
  38
  39                sk_mem_charge(sk, size);
  40                sk_msg_xfer(tmp, msg, i, size);
  41                copied += size;
  42                if (sge->length)
  43                        get_page(sk_msg_page(tmp, i));
  44                sk_msg_iter_var_next(i);
  45                tmp->sg.end = i;
  46                if (apply) {
  47                        apply_bytes -= size;
  48                        if (!apply_bytes)
  49                                break;
  50                }
  51        } while (i != msg->sg.end);
  52
  53        if (!ret) {
  54                msg->sg.start = i;
  55                sk_psock_queue_msg(psock, tmp);
  56                sk_psock_data_ready(sk, psock);
  57        } else {
  58                sk_msg_free(sk, tmp);
  59                kfree(tmp);
  60        }
  61
  62        release_sock(sk);
  63        return ret;
  64}
  65
  66static int tcp_bpf_push(struct sock *sk, struct sk_msg *msg, u32 apply_bytes,
  67                        int flags, bool uncharge)
  68{
  69        bool apply = apply_bytes;
  70        struct scatterlist *sge;
  71        struct page *page;
  72        int size, ret = 0;
  73        u32 off;
  74
  75        while (1) {
  76                bool has_tx_ulp;
  77
  78                sge = sk_msg_elem(msg, msg->sg.start);
  79                size = (apply && apply_bytes < sge->length) ?
  80                        apply_bytes : sge->length;
  81                off  = sge->offset;
  82                page = sg_page(sge);
  83
  84                tcp_rate_check_app_limited(sk);
  85retry:
  86                has_tx_ulp = tls_sw_has_ctx_tx(sk);
  87                if (has_tx_ulp) {
  88                        flags |= MSG_SENDPAGE_NOPOLICY;
  89                        ret = kernel_sendpage_locked(sk,
  90                                                     page, off, size, flags);
  91                } else {
  92                        ret = do_tcp_sendpages(sk, page, off, size, flags);
  93                }
  94
  95                if (ret <= 0)
  96                        return ret;
  97                if (apply)
  98                        apply_bytes -= ret;
  99                msg->sg.size -= ret;
 100                sge->offset += ret;
 101                sge->length -= ret;
 102                if (uncharge)
 103                        sk_mem_uncharge(sk, ret);
 104                if (ret != size) {
 105                        size -= ret;
 106                        off  += ret;
 107                        goto retry;
 108                }
 109                if (!sge->length) {
 110                        put_page(page);
 111                        sk_msg_iter_next(msg, start);
 112                        sg_init_table(sge, 1);
 113                        if (msg->sg.start == msg->sg.end)
 114                                break;
 115                }
 116                if (apply && !apply_bytes)
 117                        break;
 118        }
 119
 120        return 0;
 121}
 122
 123static int tcp_bpf_push_locked(struct sock *sk, struct sk_msg *msg,
 124                               u32 apply_bytes, int flags, bool uncharge)
 125{
 126        int ret;
 127
 128        lock_sock(sk);
 129        ret = tcp_bpf_push(sk, msg, apply_bytes, flags, uncharge);
 130        release_sock(sk);
 131        return ret;
 132}
 133
 134int tcp_bpf_sendmsg_redir(struct sock *sk, struct sk_msg *msg,
 135                          u32 bytes, int flags)
 136{
 137        bool ingress = sk_msg_to_ingress(msg);
 138        struct sk_psock *psock = sk_psock_get(sk);
 139        int ret;
 140
 141        if (unlikely(!psock)) {
 142                sk_msg_free(sk, msg);
 143                return 0;
 144        }
 145        ret = ingress ? bpf_tcp_ingress(sk, psock, msg, bytes, flags) :
 146                        tcp_bpf_push_locked(sk, msg, bytes, flags, false);
 147        sk_psock_put(sk, psock);
 148        return ret;
 149}
 150EXPORT_SYMBOL_GPL(tcp_bpf_sendmsg_redir);
 151
 152#ifdef CONFIG_BPF_SYSCALL
 153static bool tcp_bpf_stream_read(const struct sock *sk)
 154{
 155        struct sk_psock *psock;
 156        bool empty = true;
 157
 158        rcu_read_lock();
 159        psock = sk_psock(sk);
 160        if (likely(psock))
 161                empty = list_empty(&psock->ingress_msg);
 162        rcu_read_unlock();
 163        return !empty;
 164}
 165
 166static int tcp_msg_wait_data(struct sock *sk, struct sk_psock *psock,
 167                             long timeo)
 168{
 169        DEFINE_WAIT_FUNC(wait, woken_wake_function);
 170        int ret = 0;
 171
 172        if (sk->sk_shutdown & RCV_SHUTDOWN)
 173                return 1;
 174
 175        if (!timeo)
 176                return ret;
 177
 178        add_wait_queue(sk_sleep(sk), &wait);
 179        sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
 180        ret = sk_wait_event(sk, &timeo,
 181                            !list_empty(&psock->ingress_msg) ||
 182                            !skb_queue_empty(&sk->sk_receive_queue), &wait);
 183        sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
 184        remove_wait_queue(sk_sleep(sk), &wait);
 185        return ret;
 186}
 187
 188static int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 189                    int nonblock, int flags, int *addr_len)
 190{
 191        struct sk_psock *psock;
 192        int copied, ret;
 193
 194        if (unlikely(flags & MSG_ERRQUEUE))
 195                return inet_recv_error(sk, msg, len, addr_len);
 196
 197        psock = sk_psock_get(sk);
 198        if (unlikely(!psock))
 199                return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
 200        if (!skb_queue_empty(&sk->sk_receive_queue) &&
 201            sk_psock_queue_empty(psock)) {
 202                sk_psock_put(sk, psock);
 203                return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
 204        }
 205        lock_sock(sk);
 206msg_bytes_ready:
 207        copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
 208        if (!copied) {
 209                long timeo;
 210                int data;
 211
 212                timeo = sock_rcvtimeo(sk, nonblock);
 213                data = tcp_msg_wait_data(sk, psock, timeo);
 214                if (data) {
 215                        if (!sk_psock_queue_empty(psock))
 216                                goto msg_bytes_ready;
 217                        release_sock(sk);
 218                        sk_psock_put(sk, psock);
 219                        return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
 220                }
 221                copied = -EAGAIN;
 222        }
 223        ret = copied;
 224        release_sock(sk);
 225        sk_psock_put(sk, psock);
 226        return ret;
 227}
 228
 229static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
 230                                struct sk_msg *msg, int *copied, int flags)
 231{
 232        bool cork = false, enospc = sk_msg_full(msg);
 233        struct sock *sk_redir;
 234        u32 tosend, delta = 0;
 235        int ret;
 236
 237more_data:
 238        if (psock->eval == __SK_NONE) {
 239                /* Track delta in msg size to add/subtract it on SK_DROP from
 240                 * returned to user copied size. This ensures user doesn't
 241                 * get a positive return code with msg_cut_data and SK_DROP
 242                 * verdict.
 243                 */
 244                delta = msg->sg.size;
 245                psock->eval = sk_psock_msg_verdict(sk, psock, msg);
 246                delta -= msg->sg.size;
 247        }
 248
 249        if (msg->cork_bytes &&
 250            msg->cork_bytes > msg->sg.size && !enospc) {
 251                psock->cork_bytes = msg->cork_bytes - msg->sg.size;
 252                if (!psock->cork) {
 253                        psock->cork = kzalloc(sizeof(*psock->cork),
 254                                              GFP_ATOMIC | __GFP_NOWARN);
 255                        if (!psock->cork)
 256                                return -ENOMEM;
 257                }
 258                memcpy(psock->cork, msg, sizeof(*msg));
 259                return 0;
 260        }
 261
 262        tosend = msg->sg.size;
 263        if (psock->apply_bytes && psock->apply_bytes < tosend)
 264                tosend = psock->apply_bytes;
 265
 266        switch (psock->eval) {
 267        case __SK_PASS:
 268                ret = tcp_bpf_push(sk, msg, tosend, flags, true);
 269                if (unlikely(ret)) {
 270                        *copied -= sk_msg_free(sk, msg);
 271                        break;
 272                }
 273                sk_msg_apply_bytes(psock, tosend);
 274                break;
 275        case __SK_REDIRECT:
 276                sk_redir = psock->sk_redir;
 277                sk_msg_apply_bytes(psock, tosend);
 278                if (psock->cork) {
 279                        cork = true;
 280                        psock->cork = NULL;
 281                }
 282                sk_msg_return(sk, msg, tosend);
 283                release_sock(sk);
 284                ret = tcp_bpf_sendmsg_redir(sk_redir, msg, tosend, flags);
 285                lock_sock(sk);
 286                if (unlikely(ret < 0)) {
 287                        int free = sk_msg_free_nocharge(sk, msg);
 288
 289                        if (!cork)
 290                                *copied -= free;
 291                }
 292                if (cork) {
 293                        sk_msg_free(sk, msg);
 294                        kfree(msg);
 295                        msg = NULL;
 296                        ret = 0;
 297                }
 298                break;
 299        case __SK_DROP:
 300        default:
 301                sk_msg_free_partial(sk, msg, tosend);
 302                sk_msg_apply_bytes(psock, tosend);
 303                *copied -= (tosend + delta);
 304                return -EACCES;
 305        }
 306
 307        if (likely(!ret)) {
 308                if (!psock->apply_bytes) {
 309                        psock->eval =  __SK_NONE;
 310                        if (psock->sk_redir) {
 311                                sock_put(psock->sk_redir);
 312                                psock->sk_redir = NULL;
 313                        }
 314                }
 315                if (msg &&
 316                    msg->sg.data[msg->sg.start].page_link &&
 317                    msg->sg.data[msg->sg.start].length)
 318                        goto more_data;
 319        }
 320        return ret;
 321}
 322
 323static int tcp_bpf_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
 324{
 325        struct sk_msg tmp, *msg_tx = NULL;
 326        int copied = 0, err = 0;
 327        struct sk_psock *psock;
 328        long timeo;
 329        int flags;
 330
 331        /* Don't let internal do_tcp_sendpages() flags through */
 332        flags = (msg->msg_flags & ~MSG_SENDPAGE_DECRYPTED);
 333        flags |= MSG_NO_SHARED_FRAGS;
 334
 335        psock = sk_psock_get(sk);
 336        if (unlikely(!psock))
 337                return tcp_sendmsg(sk, msg, size);
 338
 339        lock_sock(sk);
 340        timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
 341        while (msg_data_left(msg)) {
 342                bool enospc = false;
 343                u32 copy, osize;
 344
 345                if (sk->sk_err) {
 346                        err = -sk->sk_err;
 347                        goto out_err;
 348                }
 349
 350                copy = msg_data_left(msg);
 351                if (!sk_stream_memory_free(sk))
 352                        goto wait_for_sndbuf;
 353                if (psock->cork) {
 354                        msg_tx = psock->cork;
 355                } else {
 356                        msg_tx = &tmp;
 357                        sk_msg_init(msg_tx);
 358                }
 359
 360                osize = msg_tx->sg.size;
 361                err = sk_msg_alloc(sk, msg_tx, msg_tx->sg.size + copy, msg_tx->sg.end - 1);
 362                if (err) {
 363                        if (err != -ENOSPC)
 364                                goto wait_for_memory;
 365                        enospc = true;
 366                        copy = msg_tx->sg.size - osize;
 367                }
 368
 369                err = sk_msg_memcopy_from_iter(sk, &msg->msg_iter, msg_tx,
 370                                               copy);
 371                if (err < 0) {
 372                        sk_msg_trim(sk, msg_tx, osize);
 373                        goto out_err;
 374                }
 375
 376                copied += copy;
 377                if (psock->cork_bytes) {
 378                        if (size > psock->cork_bytes)
 379                                psock->cork_bytes = 0;
 380                        else
 381                                psock->cork_bytes -= size;
 382                        if (psock->cork_bytes && !enospc)
 383                                goto out_err;
 384                        /* All cork bytes are accounted, rerun the prog. */
 385                        psock->eval = __SK_NONE;
 386                        psock->cork_bytes = 0;
 387                }
 388
 389                err = tcp_bpf_send_verdict(sk, psock, msg_tx, &copied, flags);
 390                if (unlikely(err < 0))
 391                        goto out_err;
 392                continue;
 393wait_for_sndbuf:
 394                set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 395wait_for_memory:
 396                err = sk_stream_wait_memory(sk, &timeo);
 397                if (err) {
 398                        if (msg_tx && msg_tx != psock->cork)
 399                                sk_msg_free(sk, msg_tx);
 400                        goto out_err;
 401                }
 402        }
 403out_err:
 404        if (err < 0)
 405                err = sk_stream_error(sk, msg->msg_flags, err);
 406        release_sock(sk);
 407        sk_psock_put(sk, psock);
 408        return copied ? copied : err;
 409}
 410
 411static int tcp_bpf_sendpage(struct sock *sk, struct page *page, int offset,
 412                            size_t size, int flags)
 413{
 414        struct sk_msg tmp, *msg = NULL;
 415        int err = 0, copied = 0;
 416        struct sk_psock *psock;
 417        bool enospc = false;
 418
 419        psock = sk_psock_get(sk);
 420        if (unlikely(!psock))
 421                return tcp_sendpage(sk, page, offset, size, flags);
 422
 423        lock_sock(sk);
 424        if (psock->cork) {
 425                msg = psock->cork;
 426        } else {
 427                msg = &tmp;
 428                sk_msg_init(msg);
 429        }
 430
 431        /* Catch case where ring is full and sendpage is stalled. */
 432        if (unlikely(sk_msg_full(msg)))
 433                goto out_err;
 434
 435        sk_msg_page_add(msg, page, size, offset);
 436        sk_mem_charge(sk, size);
 437        copied = size;
 438        if (sk_msg_full(msg))
 439                enospc = true;
 440        if (psock->cork_bytes) {
 441                if (size > psock->cork_bytes)
 442                        psock->cork_bytes = 0;
 443                else
 444                        psock->cork_bytes -= size;
 445                if (psock->cork_bytes && !enospc)
 446                        goto out_err;
 447                /* All cork bytes are accounted, rerun the prog. */
 448                psock->eval = __SK_NONE;
 449                psock->cork_bytes = 0;
 450        }
 451
 452        err = tcp_bpf_send_verdict(sk, psock, msg, &copied, flags);
 453out_err:
 454        release_sock(sk);
 455        sk_psock_put(sk, psock);
 456        return copied ? copied : err;
 457}
 458
 459enum {
 460        TCP_BPF_IPV4,
 461        TCP_BPF_IPV6,
 462        TCP_BPF_NUM_PROTS,
 463};
 464
 465enum {
 466        TCP_BPF_BASE,
 467        TCP_BPF_TX,
 468        TCP_BPF_NUM_CFGS,
 469};
 470
 471static struct proto *tcpv6_prot_saved __read_mostly;
 472static DEFINE_SPINLOCK(tcpv6_prot_lock);
 473static struct proto tcp_bpf_prots[TCP_BPF_NUM_PROTS][TCP_BPF_NUM_CFGS];
 474
 475static void tcp_bpf_rebuild_protos(struct proto prot[TCP_BPF_NUM_CFGS],
 476                                   struct proto *base)
 477{
 478        prot[TCP_BPF_BASE]                      = *base;
 479        prot[TCP_BPF_BASE].unhash               = sock_map_unhash;
 480        prot[TCP_BPF_BASE].close                = sock_map_close;
 481        prot[TCP_BPF_BASE].recvmsg              = tcp_bpf_recvmsg;
 482        prot[TCP_BPF_BASE].stream_memory_read   = tcp_bpf_stream_read;
 483
 484        prot[TCP_BPF_TX]                        = prot[TCP_BPF_BASE];
 485        prot[TCP_BPF_TX].sendmsg                = tcp_bpf_sendmsg;
 486        prot[TCP_BPF_TX].sendpage               = tcp_bpf_sendpage;
 487}
 488
 489static void tcp_bpf_check_v6_needs_rebuild(struct proto *ops)
 490{
 491        if (unlikely(ops != smp_load_acquire(&tcpv6_prot_saved))) {
 492                spin_lock_bh(&tcpv6_prot_lock);
 493                if (likely(ops != tcpv6_prot_saved)) {
 494                        tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV6], ops);
 495                        smp_store_release(&tcpv6_prot_saved, ops);
 496                }
 497                spin_unlock_bh(&tcpv6_prot_lock);
 498        }
 499}
 500
 501static int __init tcp_bpf_v4_build_proto(void)
 502{
 503        tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV4], &tcp_prot);
 504        return 0;
 505}
 506late_initcall(tcp_bpf_v4_build_proto);
 507
 508static int tcp_bpf_assert_proto_ops(struct proto *ops)
 509{
 510        /* In order to avoid retpoline, we make assumptions when we call
 511         * into ops if e.g. a psock is not present. Make sure they are
 512         * indeed valid assumptions.
 513         */
 514        return ops->recvmsg  == tcp_recvmsg &&
 515               ops->sendmsg  == tcp_sendmsg &&
 516               ops->sendpage == tcp_sendpage ? 0 : -ENOTSUPP;
 517}
 518
 519int tcp_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
 520{
 521        int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
 522        int config = psock->progs.msg_parser   ? TCP_BPF_TX   : TCP_BPF_BASE;
 523
 524        if (restore) {
 525                if (inet_csk_has_ulp(sk)) {
 526                        /* TLS does not have an unhash proto in SW cases,
 527                         * but we need to ensure we stop using the sock_map
 528                         * unhash routine because the associated psock is being
 529                         * removed. So use the original unhash handler.
 530                         */
 531                        WRITE_ONCE(sk->sk_prot->unhash, psock->saved_unhash);
 532                        tcp_update_ulp(sk, psock->sk_proto, psock->saved_write_space);
 533                } else {
 534                        sk->sk_write_space = psock->saved_write_space;
 535                        /* Pairs with lockless read in sk_clone_lock() */
 536                        WRITE_ONCE(sk->sk_prot, psock->sk_proto);
 537                }
 538                return 0;
 539        }
 540
 541        if (inet_csk_has_ulp(sk))
 542                return -EINVAL;
 543
 544        if (sk->sk_family == AF_INET6) {
 545                if (tcp_bpf_assert_proto_ops(psock->sk_proto))
 546                        return -EINVAL;
 547
 548                tcp_bpf_check_v6_needs_rebuild(psock->sk_proto);
 549        }
 550
 551        /* Pairs with lockless read in sk_clone_lock() */
 552        WRITE_ONCE(sk->sk_prot, &tcp_bpf_prots[family][config]);
 553        return 0;
 554}
 555EXPORT_SYMBOL_GPL(tcp_bpf_update_proto);
 556
 557/* If a child got cloned from a listening socket that had tcp_bpf
 558 * protocol callbacks installed, we need to restore the callbacks to
 559 * the default ones because the child does not inherit the psock state
 560 * that tcp_bpf callbacks expect.
 561 */
 562void tcp_bpf_clone(const struct sock *sk, struct sock *newsk)
 563{
 564        int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
 565        struct proto *prot = newsk->sk_prot;
 566
 567        if (prot == &tcp_bpf_prots[family][TCP_BPF_BASE])
 568                newsk->sk_prot = sk->sk_prot_creator;
 569}
 570#endif /* CONFIG_BPF_SYSCALL */
 571