net/strparser/strparser.c

   1 /*
   2  * Stream Parser
   3  *
   4  * Copyright (c) 2016 Tom Herbert <tom@herbertland.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2
   8  * as published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/bpf.h>
  12 #include <linux/errno.h>
  13 #include <linux/errqueue.h>
  14 #include <linux/file.h>
  15 #include <linux/in.h>
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18 #include <linux/net.h>
  19 #include <linux/netdevice.h>
  20 #include <linux/poll.h>
  21 #include <linux/rculist.h>
  22 #include <linux/skbuff.h>
  23 #include <linux/socket.h>
  24 #include <linux/uaccess.h>
  25 #include <linux/workqueue.h>
  26 #include <net/strparser.h>
  27 #include <net/netns/generic.h>
  28 #include <net/sock.h>
  29
  30 static struct workqueue_struct *strp_wq;
  31
  32 struct _strp_msg {
  33         /* Internal cb structure. struct strp_msg must be first for passing
  34          * to upper layer.
  35          */
  36         struct strp_msg strp;
  37         int accum_len;
  38         int early_eaten;
  39 };
  40
  41 static inline struct _strp_msg *_strp_msg(struct sk_buff *skb)
  42 {
  43         return (struct _strp_msg *)((void *)skb->cb +
  44                 offsetof(struct qdisc_skb_cb, data));
  45 }
  46
  47 /* Lower lock held */
  48 static void strp_abort_strp(struct strparser *strp, int err)
  49 {
  50         /* Unrecoverable error in receive */
  51
  52         cancel_delayed_work(&strp->msg_timer_work);
  53
  54         if (strp->stopped)
  55                 return;
  56
  57         strp->stopped = 1;
  58
  59         if (strp->sk) {
  60                 struct sock *sk = strp->sk;
  61
  62                 /* Report an error on the lower socket */
  63                 sk->sk_err = -err;
  64                 sk->sk_error_report(sk);
  65         }
  66 }
  67
  68 static void strp_start_timer(struct strparser *strp, long timeo)
  69 {
  70         if (timeo && timeo != LONG_MAX)
  71                 mod_delayed_work(strp_wq, &strp->msg_timer_work, timeo);
  72 }
  73
  74 /* Lower lock held */
  75 static void strp_parser_err(struct strparser *strp, int err,
  76                             read_descriptor_t *desc)
  77 {
  78         desc->error = err;
  79         kfree_skb(strp->skb_head);
  80         strp->skb_head = NULL;
  81         strp->cb.abort_parser(strp, err);
  82 }
  83
  84 static inline int strp_peek_len(struct strparser *strp)
  85 {
  86         if (strp->sk) {
  87                 struct socket *sock = strp->sk->sk_socket;
  88
  89                 return sock->ops->peek_len(sock);
  90         }
  91
  92         /* If we don't have an associated socket there's nothing to peek.
  93          * Return int max to avoid stopping the strparser.
  94          */
  95
  96         return INT_MAX;
  97 }
  98
  99 /* Lower socket lock held */
 100 static int __strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
 101                        unsigned int orig_offset, size_t orig_len,
 102                        size_t max_msg_size, long timeo)
 103 {
 104         struct strparser *strp = (struct strparser *)desc->arg.data;
 105         struct _strp_msg *stm;
 106         struct sk_buff *head, *skb;
 107         size_t eaten = 0, cand_len;
 108         ssize_t extra;
 109         int err;
 110         bool cloned_orig = false;
 111
 112         if (strp->paused)
 113                 return 0;
 114
 115         head = strp->skb_head;
 116         if (head) {
 117                 /* Message already in progress */
 118
 119                 stm = _strp_msg(head);
 120                 if (unlikely(stm->early_eaten)) {
 121                         /* Already some number of bytes on the receive sock
 122                          * data saved in skb_head, just indicate they
 123                          * are consumed.
 124                          */
 125                         eaten = orig_len <= stm->early_eaten ?
 126                                 orig_len : stm->early_eaten;
 127                         stm->early_eaten -= eaten;
 128
 129                         return eaten;
 130                 }
 131
 132                 if (unlikely(orig_offset)) {
 133                         /* Getting data with a non-zero offset when a message is
 134                          * in progress is not expected. If it does happen, we
 135                          * need to clone and pull since we can't deal with
 136                          * offsets in the skbs for a message expect in the head.
 137                          */
 138                         orig_skb = skb_clone(orig_skb, GFP_ATOMIC);
 139                         if (!orig_skb) {
 140                                 STRP_STATS_INCR(strp->stats.mem_fail);
 141                                 desc->error = -ENOMEM;
 142                                 return 0;
 143                         }
 144                         if (!pskb_pull(orig_skb, orig_offset)) {
 145                                 STRP_STATS_INCR(strp->stats.mem_fail);
 146                                 kfree_skb(orig_skb);
 147                                 desc->error = -ENOMEM;
 148                                 return 0;
 149                         }
 150                         cloned_orig = true;
 151                         orig_offset = 0;
 152                 }
 153
 154                 if (!strp->skb_nextp) {
 155                         /* We are going to append to the frags_list of head.
 156                          * Need to unshare the frag_list.
 157                          */
 158                         err = skb_unclone(head, GFP_ATOMIC);
 159                         if (err) {
 160                                 STRP_STATS_INCR(strp->stats.mem_fail);
 161                                 desc->error = err;
 162                                 return 0;
 163                         }
 164
 165                         if (unlikely(skb_shinfo(head)->frag_list)) {
 166                                 /* We can't append to an sk_buff that already
 167                                  * has a frag_list. We create a new head, point
 168                                  * the frag_list of that to the old head, and
 169                                  * then are able to use the old head->next for
 170                                  * appending to the message.
 171                                  */
 172                                 if (WARN_ON(head->next)) {
 173                                         desc->error = -EINVAL;
 174                                         return 0;
 175                                 }
 176
 177                                 skb = alloc_skb(0, GFP_ATOMIC);
 178                                 if (!skb) {
 179                                         STRP_STATS_INCR(strp->stats.mem_fail);
 180                                         desc->error = -ENOMEM;
 181                                         return 0;
 182                                 }
 183                                 skb->len = head->len;
 184                                 skb->data_len = head->len;
 185                                 skb->truesize = head->truesize;
 186                                 *_strp_msg(skb) = *_strp_msg(head);
 187                                 strp->skb_nextp = &head->next;
 188                                 skb_shinfo(skb)->frag_list = head;
 189                                 strp->skb_head = skb;
 190                                 head = skb;
 191                         } else {
 192                                 strp->skb_nextp =
 193                                     &skb_shinfo(head)->frag_list;
 194                         }
 195                 }
 196         }
 197
 198         while (eaten < orig_len) {
 199                 /* Always clone since we will consume something */
 200                 skb = skb_clone(orig_skb, GFP_ATOMIC);
 201                 if (!skb) {
 202                         STRP_STATS_INCR(strp->stats.mem_fail);
 203                         desc->error = -ENOMEM;
 204                         break;
 205                 }
 206
 207                 cand_len = orig_len - eaten;
 208
 209                 head = strp->skb_head;
 210                 if (!head) {
 211                         head = skb;
 212                         strp->skb_head = head;
 213                         /* Will set skb_nextp on next packet if needed */
 214                         strp->skb_nextp = NULL;
 215                         stm = _strp_msg(head);
 216                         memset(stm, 0, sizeof(*stm));
 217                         stm->strp.offset = orig_offset + eaten;
 218                 } else {
 219                         /* Unclone since we may be appending to an skb that we
 220                          * already share a frag_list with.
 221                          */
 222                         err = skb_unclone(skb, GFP_ATOMIC);
 223                         if (err) {
 224                                 STRP_STATS_INCR(strp->stats.mem_fail);
 225                                 desc->error = err;
 226                                 break;
 227                         }
 228
 229                         stm = _strp_msg(head);
 230                         *strp->skb_nextp = skb;
 231                         strp->skb_nextp = &skb->next;
 232                         head->data_len += skb->len;
 233                         head->len += skb->len;
 234                         head->truesize += skb->truesize;
 235                 }
 236
 237                 if (!stm->strp.full_len) {
 238                         ssize_t len;
 239
 240                         len = (*strp->cb.parse_msg)(strp, head);
 241
 242                         if (!len) {
 243                                 /* Need more header to determine length */
 244                                 if (!stm->accum_len) {
 245                                         /* Start RX timer for new message */
 246                                         strp_start_timer(strp, timeo);
 247                                 }
 248                                 stm->accum_len += cand_len;
 249                                 eaten += cand_len;
 250                                 STRP_STATS_INCR(strp->stats.need_more_hdr);
 251                                 WARN_ON(eaten != orig_len);
 252                                 break;
 253                         } else if (len < 0) {
 254                                 if (len == -ESTRPIPE && stm->accum_len) {
 255                                         len = -ENODATA;
 256                                         strp->unrecov_intr = 1;
 257                                 } else {
 258                                         strp->interrupted = 1;
 259                                 }
 260                                 strp_parser_err(strp, len, desc);
 261                                 break;
 262                         } else if (len > max_msg_size) {
 263                                 /* Message length exceeds maximum allowed */
 264                                 STRP_STATS_INCR(strp->stats.msg_too_big);
 265                                 strp_parser_err(strp, -EMSGSIZE, desc);
 266                                 break;
 267                         } else if (len <= (ssize_t)head->len -
 268                                           skb->len - stm->strp.offset) {
 269                                 /* Length must be into new skb (and also
 270                                  * greater than zero)
 271                                  */
 272                                 STRP_STATS_INCR(strp->stats.bad_hdr_len);
 273                                 strp_parser_err(strp, -EPROTO, desc);
 274                                 break;
 275                         }
 276
 277                         stm->strp.full_len = len;
 278                 }
 279
 280                 extra = (ssize_t)(stm->accum_len + cand_len) -
 281                         stm->strp.full_len;
 282
 283                 if (extra < 0) {
 284                         /* Message not complete yet. */
 285                         if (stm->strp.full_len - stm->accum_len >
 286                             strp_peek_len(strp)) {
 287                                 /* Don't have the whole message in the socket
 288                                  * buffer. Set strp->need_bytes to wait for
 289                                  * the rest of the message. Also, set "early
 290                                  * eaten" since we've already buffered the skb
 291                                  * but don't consume yet per strp_read_sock.
 292                                  */
 293
 294                                 if (!stm->accum_len) {
 295                                         /* Start RX timer for new message */
 296                                         strp_start_timer(strp, timeo);
 297                                 }
 298
 299                                 stm->accum_len += cand_len;
 300                                 strp->need_bytes = stm->strp.full_len -
 301                                                        stm->accum_len;
 302                                 stm->early_eaten = cand_len;
 303                                 STRP_STATS_ADD(strp->stats.bytes, cand_len);
 304                                 desc->count = 0; /* Stop reading socket */
 305                                 break;
 306                         }
 307                         stm->accum_len += cand_len;
 308                         eaten += cand_len;
 309                         WARN_ON(eaten != orig_len);
 310                         break;
 311                 }
 312
 313                 /* Positive extra indicates ore bytes than needed for the
 314                  * message
 315                  */
 316
 317                 WARN_ON(extra > cand_len);
 318
 319                 eaten += (cand_len - extra);
 320
 321                 /* Hurray, we have a new message! */
 322                 cancel_delayed_work(&strp->msg_timer_work);
 323                 strp->skb_head = NULL;
 324                 strp->need_bytes = 0;
 325                 STRP_STATS_INCR(strp->stats.msgs);
 326
 327                 /* Give skb to upper layer */
 328                 strp->cb.rcv_msg(strp, head);
 329
 330                 if (unlikely(strp->paused)) {
 331                         /* Upper layer paused strp */
 332                         break;
 333                 }
 334         }
 335
 336         if (cloned_orig)
 337                 kfree_skb(orig_skb);
 338
 339         STRP_STATS_ADD(strp->stats.bytes, eaten);
 340
 341         return eaten;
 342 }
 343
 344 int strp_process(struct strparser *strp, struct sk_buff *orig_skb,
 345                  unsigned int orig_offset, size_t orig_len,
 346                  size_t max_msg_size, long timeo)
 347 {
 348         read_descriptor_t desc; /* Dummy arg to strp_recv */
 349
 350         desc.arg.data = strp;
 351
 352         return __strp_recv(&desc, orig_skb, orig_offset, orig_len,
 353                            max_msg_size, timeo);
 354 }
 355 EXPORT_SYMBOL_GPL(strp_process);
 356
 357 static int strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
 358                      unsigned int orig_offset, size_t orig_len)
 359 {
 360         struct strparser *strp = (struct strparser *)desc->arg.data;
 361
 362         return __strp_recv(desc, orig_skb, orig_offset, orig_len,
 363                            strp->sk->sk_rcvbuf, strp->sk->sk_rcvtimeo);
 364 }
 365
 366 static int default_read_sock_done(struct strparser *strp, int err)
 367 {
 368         return err;
 369 }
 370
 371 /* Called with lock held on lower socket */
 372 static int strp_read_sock(struct strparser *strp)
 373 {
 374         struct socket *sock = strp->sk->sk_socket;
 375         read_descriptor_t desc;
 376
 377         if (unlikely(!sock || !sock->ops || !sock->ops->read_sock))
 378                 return -EBUSY;
 379
 380         desc.arg.data = strp;
 381         desc.error = 0;
 382         desc.count = 1; /* give more than one skb per call */
 383
 384         /* sk should be locked here, so okay to do read_sock */
 385         sock->ops->read_sock(strp->sk, &desc, strp_recv);
 386
 387         desc.error = strp->cb.read_sock_done(strp, desc.error);
 388
 389         return desc.error;
 390 }
 391
 392 /* Lower sock lock held */
 393 void strp_data_ready(struct strparser *strp)
 394 {
 395         if (unlikely(strp->stopped))
 396                 return;
 397
 398         /* This check is needed to synchronize with do_strp_work.
 399          * do_strp_work acquires a process lock (lock_sock) whereas
 400          * the lock held here is bh_lock_sock. The two locks can be
 401          * held by different threads at the same time, but bh_lock_sock
 402          * allows a thread in BH context to safely check if the process
 403          * lock is held. In this case, if the lock is held, queue work.
 404          */
 405         if (sock_owned_by_user_nocheck(strp->sk)) {
 406                 queue_work(strp_wq, &strp->work);
 407                 return;
 408         }
 409
 410         if (strp->paused)
 411                 return;
 412
 413         if (strp->need_bytes) {
 414                 if (strp_peek_len(strp) < strp->need_bytes)
 415                         return;
 416         }
 417
 418         if (strp_read_sock(strp) == -ENOMEM)
 419                 queue_work(strp_wq, &strp->work);
 420 }
 421 EXPORT_SYMBOL_GPL(strp_data_ready);
 422
 423 static void do_strp_work(struct strparser *strp)
 424 {
 425         read_descriptor_t rd_desc;
 426
 427         /* We need the read lock to synchronize with strp_data_ready. We
 428          * need the socket lock for calling strp_read_sock.
 429          */
 430         strp->cb.lock(strp);
 431
 432         if (unlikely(strp->stopped))
 433                 goto out;
 434
 435         if (strp->paused)
 436                 goto out;
 437
 438         rd_desc.arg.data = strp;
 439
 440         if (strp_read_sock(strp) == -ENOMEM)
 441                 queue_work(strp_wq, &strp->work);
 442
 443 out:
 444         strp->cb.unlock(strp);
 445 }
 446
 447 static void strp_work(struct work_struct *w)
 448 {
 449         do_strp_work(container_of(w, struct strparser, work));
 450 }
 451
 452 static void strp_msg_timeout(struct work_struct *w)
 453 {
 454         struct strparser *strp = container_of(w, struct strparser,
 455                                               msg_timer_work.work);
 456
 457         /* Message assembly timed out */
 458         STRP_STATS_INCR(strp->stats.msg_timeouts);
 459         strp->cb.lock(strp);
 460         strp->cb.abort_parser(strp, -ETIMEDOUT);
 461         strp->cb.unlock(strp);
 462 }
 463
 464 static void strp_sock_lock(struct strparser *strp)
 465 {
 466         lock_sock(strp->sk);
 467 }
 468
 469 static void strp_sock_unlock(struct strparser *strp)
 470 {
 471         release_sock(strp->sk);
 472 }
 473
 474 int strp_init(struct strparser *strp, struct sock *sk,
 475               const struct strp_callbacks *cb)
 476 {
 477
 478         if (!cb || !cb->rcv_msg || !cb->parse_msg)
 479                 return -EINVAL;
 480
 481         /* The sk (sock) arg determines the mode of the stream parser.
 482          *
 483          * If the sock is set then the strparser is in receive callback mode.
 484          * The upper layer calls strp_data_ready to kick receive processing
 485          * and strparser calls the read_sock function on the socket to
 486          * get packets.
 487          *
 488          * If the sock is not set then the strparser is in general mode.
 489          * The upper layer calls strp_process for each skb to be parsed.
 490          */
 491
 492         if (!sk) {
 493                 if (!cb->lock || !cb->unlock)
 494                         return -EINVAL;
 495         }
 496
 497         memset(strp, 0, sizeof(*strp));
 498
 499         strp->sk = sk;
 500
 501         strp->cb.lock = cb->lock ? : strp_sock_lock;
 502         strp->cb.unlock = cb->unlock ? : strp_sock_unlock;
 503         strp->cb.rcv_msg = cb->rcv_msg;
 504         strp->cb.parse_msg = cb->parse_msg;
 505         strp->cb.read_sock_done = cb->read_sock_done ? : default_read_sock_done;
 506         strp->cb.abort_parser = cb->abort_parser ? : strp_abort_strp;
 507
 508         INIT_DELAYED_WORK(&strp->msg_timer_work, strp_msg_timeout);
 509         INIT_WORK(&strp->work, strp_work);
 510
 511         return 0;
 512 }
 513 EXPORT_SYMBOL_GPL(strp_init);
 514
 515 /* Sock process lock held (lock_sock) */
 516 void __strp_unpause(struct strparser *strp)
 517 {
 518         strp->paused = 0;
 519
 520         if (strp->need_bytes) {
 521                 if (strp_peek_len(strp) < strp->need_bytes)
 522                         return;
 523         }
 524         strp_read_sock(strp);
 525 }
 526 EXPORT_SYMBOL_GPL(__strp_unpause);
 527
 528 void strp_unpause(struct strparser *strp)
 529 {
 530         strp->paused = 0;
 531
 532         /* Sync setting paused with RX work */
 533         smp_mb();
 534
 535         queue_work(strp_wq, &strp->work);
 536 }
 537 EXPORT_SYMBOL_GPL(strp_unpause);
 538
 539 /* strp must already be stopped so that strp_recv will no longer be called.
 540  * Note that strp_done is not called with the lower socket held.
 541  */
 542 void strp_done(struct strparser *strp)
 543 {
 544         WARN_ON(!strp->stopped);
 545
 546         cancel_delayed_work_sync(&strp->msg_timer_work);
 547         cancel_work_sync(&strp->work);
 548
 549         if (strp->skb_head) {
 550                 kfree_skb(strp->skb_head);
 551                 strp->skb_head = NULL;
 552         }
 553 }
 554 EXPORT_SYMBOL_GPL(strp_done);
 555
 556 void strp_stop(struct strparser *strp)
 557 {
 558         strp->stopped = 1;
 559 }
 560 EXPORT_SYMBOL_GPL(strp_stop);
 561
 562 void strp_check_rcv(struct strparser *strp)
 563 {
 564         queue_work(strp_wq, &strp->work);
 565 }
 566 EXPORT_SYMBOL_GPL(strp_check_rcv);
 567
 568 static int __init strp_mod_init(void)
 569 {
 570         strp_wq = create_singlethread_workqueue("kstrp");
 571
 572         return 0;
 573 }
 574
 575 static void __exit strp_mod_exit(void)
 576 {
 577         destroy_workqueue(strp_wq);
 578 }
 579 module_init(strp_mod_init);
 580 module_exit(strp_mod_exit);
 581 MODULE_LICENSE("GPL");