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 since we may be appending to an skb that we
 205                          * already share a frag_list with.
 206                          */
 207                         err = skb_unclone(skb, GFP_ATOMIC);
 208                         if (err) {
 209                                 STRP_STATS_INCR(strp->stats.mem_fail);
 210                                 desc->error = err;
 211                                 break;
 212                         }
 213
 214                         stm = _strp_msg(head);
 215                         *strp->skb_nextp = skb;
 216                         strp->skb_nextp = &skb->next;
 217                         head->data_len += skb->len;
 218                         head->len += skb->len;
 219                         head->truesize += skb->truesize;
 220                 }
 221
 222                 if (!stm->strp.full_len) {
 223                         ssize_t len;
 224
 225                         len = (*strp->cb.parse_msg)(strp, head);
 226
 227                         if (!len) {
 228                                 /* Need more header to determine length */
 229                                 if (!stm->accum_len) {
 230                                         /* Start RX timer for new message */
 231                                         strp_start_timer(strp, timeo);
 232                                 }
 233                                 stm->accum_len += cand_len;
 234                                 eaten += cand_len;
 235                                 STRP_STATS_INCR(strp->stats.need_more_hdr);
 236                                 WARN_ON(eaten != orig_len);
 237                                 break;
 238                         } else if (len < 0) {
 239                                 if (len == -ESTRPIPE && stm->accum_len) {
 240                                         len = -ENODATA;
 241                                         strp->unrecov_intr = 1;
 242                                 } else {
 243                                         strp->interrupted = 1;
 244                                 }
 245                                 strp_parser_err(strp, len, desc);
 246                                 break;
 247                         } else if (len > max_msg_size) {
 248                                 /* Message length exceeds maximum allowed */
 249                                 STRP_STATS_INCR(strp->stats.msg_too_big);
 250                                 strp_parser_err(strp, -EMSGSIZE, desc);
 251                                 break;
 252                         } else if (len <= (ssize_t)head->len -
 253                                           skb->len - stm->strp.offset) {
 254                                 /* Length must be into new skb (and also
 255                                  * greater than zero)
 256                                  */
 257                                 STRP_STATS_INCR(strp->stats.bad_hdr_len);
 258                                 strp_parser_err(strp, -EPROTO, desc);
 259                                 break;
 260                         }
 261
 262                         stm->strp.full_len = len;
 263                 }
 264
 265                 extra = (ssize_t)(stm->accum_len + cand_len) -
 266                         stm->strp.full_len;
 267
 268                 if (extra < 0) {
 269                         /* Message not complete yet. */
 270                         if (stm->strp.full_len - stm->accum_len >
 271                             strp_peek_len(strp)) {
 272                                 /* Don't have the whole message in the socket
 273                                  * buffer. Set strp->need_bytes to wait for
 274                                  * the rest of the message. Also, set "early
 275                                  * eaten" since we've already buffered the skb
 276                                  * but don't consume yet per strp_read_sock.
 277                                  */
 278
 279                                 if (!stm->accum_len) {
 280                                         /* Start RX timer for new message */
 281                                         strp_start_timer(strp, timeo);
 282                                 }
 283
 284                                 stm->accum_len += cand_len;
 285                                 eaten += cand_len;
 286                                 strp->need_bytes = stm->strp.full_len -
 287                                                        stm->accum_len;
 288                                 STRP_STATS_ADD(strp->stats.bytes, cand_len);
 289                                 desc->count = 0; /* Stop reading socket */
 290                                 break;
 291                         }
 292                         stm->accum_len += cand_len;
 293                         eaten += cand_len;
 294                         WARN_ON(eaten != orig_len);
 295                         break;
 296                 }
 297
 298                 /* Positive extra indicates ore bytes than needed for the
 299                  * message
 300                  */
 301
 302                 WARN_ON(extra > cand_len);
 303
 304                 eaten += (cand_len - extra);
 305
 306                 /* Hurray, we have a new message! */
 307                 cancel_delayed_work(&strp->msg_timer_work);
 308                 strp->skb_head = NULL;
 309                 strp->need_bytes = 0;
 310                 STRP_STATS_INCR(strp->stats.msgs);
 311
 312                 /* Give skb to upper layer */
 313                 strp->cb.rcv_msg(strp, head);
 314
 315                 if (unlikely(strp->paused)) {
 316                         /* Upper layer paused strp */
 317                         break;
 318                 }
 319         }
 320
 321         if (cloned_orig)
 322                 kfree_skb(orig_skb);
 323
 324         STRP_STATS_ADD(strp->stats.bytes, eaten);
 325
 326         return eaten;
 327 }
 328
 329 int strp_process(struct strparser *strp, struct sk_buff *orig_skb,
 330                  unsigned int orig_offset, size_t orig_len,
 331                  size_t max_msg_size, long timeo)
 332 {
 333         read_descriptor_t desc; /* Dummy arg to strp_recv */
 334
 335         desc.arg.data = strp;
 336
 337         return __strp_recv(&desc, orig_skb, orig_offset, orig_len,
 338                            max_msg_size, timeo);
 339 }
 340 EXPORT_SYMBOL_GPL(strp_process);
 341
 342 static int strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
 343                      unsigned int orig_offset, size_t orig_len)
 344 {
 345         struct strparser *strp = (struct strparser *)desc->arg.data;
 346
 347         return __strp_recv(desc, orig_skb, orig_offset, orig_len,
 348                            strp->sk->sk_rcvbuf, strp->sk->sk_rcvtimeo);
 349 }
 350
 351 static int default_read_sock_done(struct strparser *strp, int err)
 352 {
 353         return err;
 354 }
 355
 356 /* Called with lock held on lower socket */
 357 static int strp_read_sock(struct strparser *strp)
 358 {
 359         struct socket *sock = strp->sk->sk_socket;
 360         read_descriptor_t desc;
 361
 362         if (unlikely(!sock || !sock->ops || !sock->ops->read_sock))
 363                 return -EBUSY;
 364
 365         desc.arg.data = strp;
 366         desc.error = 0;
 367         desc.count = 1; /* give more than one skb per call */
 368
 369         /* sk should be locked here, so okay to do read_sock */
 370         sock->ops->read_sock(strp->sk, &desc, strp_recv);
 371
 372         desc.error = strp->cb.read_sock_done(strp, desc.error);
 373
 374         return desc.error;
 375 }
 376
 377 /* Lower sock lock held */
 378 void strp_data_ready(struct strparser *strp)
 379 {
 380         if (unlikely(strp->stopped) || strp->paused)
 381                 return;
 382
 383         /* This check is needed to synchronize with do_strp_work.
 384          * do_strp_work acquires a process lock (lock_sock) whereas
 385          * the lock held here is bh_lock_sock. The two locks can be
 386          * held by different threads at the same time, but bh_lock_sock
 387          * allows a thread in BH context to safely check if the process
 388          * lock is held. In this case, if the lock is held, queue work.
 389          */
 390         if (sock_owned_by_user_nocheck(strp->sk)) {
 391                 queue_work(strp_wq, &strp->work);
 392                 return;
 393         }
 394
 395         if (strp->need_bytes) {
 396                 if (strp_peek_len(strp) < strp->need_bytes)
 397                         return;
 398         }
 399
 400         if (strp_read_sock(strp) == -ENOMEM)
 401                 queue_work(strp_wq, &strp->work);
 402 }
 403 EXPORT_SYMBOL_GPL(strp_data_ready);
 404
 405 static void do_strp_work(struct strparser *strp)
 406 {
 407         read_descriptor_t rd_desc;
 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         rd_desc.arg.data = strp;
 421
 422         if (strp_read_sock(strp) == -ENOMEM)
 423                 queue_work(strp_wq, &strp->work);
 424
 425 out:
 426         strp->cb.unlock(strp);
 427 }
 428
 429 static void strp_work(struct work_struct *w)
 430 {
 431         do_strp_work(container_of(w, struct strparser, work));
 432 }
 433
 434 static void strp_msg_timeout(struct work_struct *w)
 435 {
 436         struct strparser *strp = container_of(w, struct strparser,
 437                                               msg_timer_work.work);
 438
 439         /* Message assembly timed out */
 440         STRP_STATS_INCR(strp->stats.msg_timeouts);
 441         strp->cb.lock(strp);
 442         strp->cb.abort_parser(strp, -ETIMEDOUT);
 443         strp->cb.unlock(strp);
 444 }
 445
 446 static void strp_sock_lock(struct strparser *strp)
 447 {
 448         lock_sock(strp->sk);
 449 }
 450
 451 static void strp_sock_unlock(struct strparser *strp)
 452 {
 453         release_sock(strp->sk);
 454 }
 455
 456 int strp_init(struct strparser *strp, struct sock *sk,
 457               const struct strp_callbacks *cb)
 458 {
 459
 460         if (!cb || !cb->rcv_msg || !cb->parse_msg)
 461                 return -EINVAL;
 462
 463         /* The sk (sock) arg determines the mode of the stream parser.
 464          *
 465          * If the sock is set then the strparser is in receive callback mode.
 466          * The upper layer calls strp_data_ready to kick receive processing
 467          * and strparser calls the read_sock function on the socket to
 468          * get packets.
 469          *
 470          * If the sock is not set then the strparser is in general mode.
 471          * The upper layer calls strp_process for each skb to be parsed.
 472          */
 473
 474         if (!sk) {
 475                 if (!cb->lock || !cb->unlock)
 476                         return -EINVAL;
 477         }
 478
 479         memset(strp, 0, sizeof(*strp));
 480
 481         strp->sk = sk;
 482
 483         strp->cb.lock = cb->lock ? : strp_sock_lock;
 484         strp->cb.unlock = cb->unlock ? : strp_sock_unlock;
 485         strp->cb.rcv_msg = cb->rcv_msg;
 486         strp->cb.parse_msg = cb->parse_msg;
 487         strp->cb.read_sock_done = cb->read_sock_done ? : default_read_sock_done;
 488         strp->cb.abort_parser = cb->abort_parser ? : strp_abort_strp;
 489
 490         INIT_DELAYED_WORK(&strp->msg_timer_work, strp_msg_timeout);
 491         INIT_WORK(&strp->work, strp_work);
 492
 493         return 0;
 494 }
 495 EXPORT_SYMBOL_GPL(strp_init);
 496
 497 /* Sock process lock held (lock_sock) */
 498 void __strp_unpause(struct strparser *strp)
 499 {
 500         strp->paused = 0;
 501
 502         if (strp->need_bytes) {
 503                 if (strp_peek_len(strp) < strp->need_bytes)
 504                         return;
 505         }
 506         strp_read_sock(strp);
 507 }
 508 EXPORT_SYMBOL_GPL(__strp_unpause);
 509
 510 void strp_unpause(struct strparser *strp)
 511 {
 512         strp->paused = 0;
 513
 514         /* Sync setting paused with RX work */
 515         smp_mb();
 516
 517         queue_work(strp_wq, &strp->work);
 518 }
 519 EXPORT_SYMBOL_GPL(strp_unpause);
 520
 521 /* strp must already be stopped so that strp_recv will no longer be called.
 522  * Note that strp_done is not called with the lower socket held.
 523  */
 524 void strp_done(struct strparser *strp)
 525 {
 526         WARN_ON(!strp->stopped);
 527
 528         cancel_delayed_work_sync(&strp->msg_timer_work);
 529         cancel_work_sync(&strp->work);
 530
 531         if (strp->skb_head) {
 532                 kfree_skb(strp->skb_head);
 533                 strp->skb_head = NULL;
 534         }
 535 }
 536 EXPORT_SYMBOL_GPL(strp_done);
 537
 538 void strp_stop(struct strparser *strp)
 539 {
 540         strp->stopped = 1;
 541 }
 542 EXPORT_SYMBOL_GPL(strp_stop);
 543
 544 void strp_check_rcv(struct strparser *strp)
 545 {
 546         queue_work(strp_wq, &strp->work);
 547 }
 548 EXPORT_SYMBOL_GPL(strp_check_rcv);
 549
 550 static int __init strp_mod_init(void)
 551 {
 552         strp_wq = create_singlethread_workqueue("kstrp");
 553
 554         return 0;
 555 }
 556
 557 static void __exit strp_mod_exit(void)
 558 {
 559         destroy_workqueue(strp_wq);
 560 }
 561 module_init(strp_mod_init);
 562 module_exit(strp_mod_exit);
 563 MODULE_LICENSE("GPL");