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