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                         if (skb_has_frag_list(head)) {
 144                                 err = skb_unclone(head, GFP_ATOMIC);
 145                                 if (err) {
 146                                         STRP_STATS_INCR(strp->stats.mem_fail);
 147                                         desc->error = err;
 148                                         return 0;
 149                                 }
 150                         }
 151
 152                         if (unlikely(skb_shinfo(head)->frag_list)) {
 153                                 /* We can't append to an sk_buff that already
 154                                  * has a frag_list. We create a new head, point
 155                                  * the frag_list of that to the old head, and
 156                                  * then are able to use the old head->next for
 157                                  * appending to the message.
 158                                  */
 159                                 if (WARN_ON(head->next)) {
 160                                         desc->error = -EINVAL;
 161                                         return 0;
 162                                 }
 163
 164                                 skb = alloc_skb(0, GFP_ATOMIC);
 165                                 if (!skb) {
 166                                         STRP_STATS_INCR(strp->stats.mem_fail);
 167                                         desc->error = -ENOMEM;
 168                                         return 0;
 169                                 }
 170                                 skb->len = head->len;
 171                                 skb->data_len = head->len;
 172                                 skb->truesize = head->truesize;
 173                                 *_strp_msg(skb) = *_strp_msg(head);
 174                                 strp->skb_nextp = &head->next;
 175                                 skb_shinfo(skb)->frag_list = head;
 176                                 strp->skb_head = skb;
 177                                 head = skb;
 178                         } else {
 179                                 strp->skb_nextp =
 180                                     &skb_shinfo(head)->frag_list;
 181                         }
 182                 }
 183         }
 184
 185         while (eaten < orig_len) {
 186                 /* Always clone since we will consume something */
 187                 skb = skb_clone(orig_skb, GFP_ATOMIC);
 188                 if (!skb) {
 189                         STRP_STATS_INCR(strp->stats.mem_fail);
 190                         desc->error = -ENOMEM;
 191                         break;
 192                 }
 193
 194                 cand_len = orig_len - eaten;
 195
 196                 head = strp->skb_head;
 197                 if (!head) {
 198                         head = skb;
 199                         strp->skb_head = head;
 200                         /* Will set skb_nextp on next packet if needed */
 201                         strp->skb_nextp = NULL;
 202                         stm = _strp_msg(head);
 203                         memset(stm, 0, sizeof(*stm));
 204                         stm->strp.offset = orig_offset + eaten;
 205                 } else {
 206                         /* Unclone if we are appending to an skb that we
 207                          * already share a frag_list with.
 208                          */
 209                         if (skb_has_frag_list(skb)) {
 210                                 err = skb_unclone(skb, GFP_ATOMIC);
 211                                 if (err) {
 212                                         STRP_STATS_INCR(strp->stats.mem_fail);
 213                                         desc->error = err;
 214                                         break;
 215                                 }
 216                         }
 217
 218                         stm = _strp_msg(head);
 219                         *strp->skb_nextp = skb;
 220                         strp->skb_nextp = &skb->next;
 221                         head->data_len += skb->len;
 222                         head->len += skb->len;
 223                         head->truesize += skb->truesize;
 224                 }
 225
 226                 if (!stm->strp.full_len) {
 227                         ssize_t len;
 228
 229                         len = (*strp->cb.parse_msg)(strp, head);
 230
 231                         if (!len) {
 232                                 /* Need more header to determine length */
 233                                 if (!stm->accum_len) {
 234                                         /* Start RX timer for new message */
 235                                         strp_start_timer(strp, timeo);
 236                                 }
 237                                 stm->accum_len += cand_len;
 238                                 eaten += cand_len;
 239                                 STRP_STATS_INCR(strp->stats.need_more_hdr);
 240                                 WARN_ON(eaten != orig_len);
 241                                 break;
 242                         } else if (len < 0) {
 243                                 if (len == -ESTRPIPE && stm->accum_len) {
 244                                         len = -ENODATA;
 245                                         strp->unrecov_intr = 1;
 246                                 } else {
 247                                         strp->interrupted = 1;
 248                                 }
 249                                 strp_parser_err(strp, len, desc);
 250                                 break;
 251                         } else if (len > max_msg_size) {
 252                                 /* Message length exceeds maximum allowed */
 253                                 STRP_STATS_INCR(strp->stats.msg_too_big);
 254                                 strp_parser_err(strp, -EMSGSIZE, desc);
 255                                 break;
 256                         } else if (len <= (ssize_t)head->len -
 257                                           skb->len - stm->strp.offset) {
 258                                 /* Length must be into new skb (and also
 259                                  * greater than zero)
 260                                  */
 261                                 STRP_STATS_INCR(strp->stats.bad_hdr_len);
 262                                 strp_parser_err(strp, -EPROTO, desc);
 263                                 break;
 264                         }
 265
 266                         stm->strp.full_len = len;
 267                 }
 268
 269                 extra = (ssize_t)(stm->accum_len + cand_len) -
 270                         stm->strp.full_len;
 271
 272                 if (extra < 0) {
 273                         /* Message not complete yet. */
 274                         if (stm->strp.full_len - stm->accum_len >
 275                             strp_peek_len(strp)) {
 276                                 /* Don't have the whole message in the socket
 277                                  * buffer. Set strp->need_bytes to wait for
 278                                  * the rest of the message. Also, set "early
 279                                  * eaten" since we've already buffered the skb
 280                                  * but don't consume yet per strp_read_sock.
 281                                  */
 282
 283                                 if (!stm->accum_len) {
 284                                         /* Start RX timer for new message */
 285                                         strp_start_timer(strp, timeo);
 286                                 }
 287
 288                                 stm->accum_len += cand_len;
 289                                 eaten += cand_len;
 290                                 strp->need_bytes = stm->strp.full_len -
 291                                                        stm->accum_len;
 292                                 STRP_STATS_ADD(strp->stats.bytes, cand_len);
 293                                 desc->count = 0; /* Stop reading socket */
 294                                 break;
 295                         }
 296                         stm->accum_len += cand_len;
 297                         eaten += cand_len;
 298                         WARN_ON(eaten != orig_len);
 299                         break;
 300                 }
 301
 302                 /* Positive extra indicates ore bytes than needed for the
 303                  * message
 304                  */
 305
 306                 WARN_ON(extra > cand_len);
 307
 308                 eaten += (cand_len - extra);
 309
 310                 /* Hurray, we have a new message! */
 311                 cancel_delayed_work(&strp->msg_timer_work);
 312                 strp->skb_head = NULL;
 313                 strp->need_bytes = 0;
 314                 STRP_STATS_INCR(strp->stats.msgs);
 315
 316                 /* Give skb to upper layer */
 317                 strp->cb.rcv_msg(strp, head);
 318
 319                 if (unlikely(strp->paused)) {
 320                         /* Upper layer paused strp */
 321                         break;
 322                 }
 323         }
 324
 325         if (cloned_orig)
 326                 kfree_skb(orig_skb);
 327
 328         STRP_STATS_ADD(strp->stats.bytes, eaten);
 329
 330         return eaten;
 331 }
 332
 333 int strp_process(struct strparser *strp, struct sk_buff *orig_skb,
 334                  unsigned int orig_offset, size_t orig_len,
 335                  size_t max_msg_size, long timeo)
 336 {
 337         read_descriptor_t desc; /* Dummy arg to strp_recv */
 338
 339         desc.arg.data = strp;
 340
 341         return __strp_recv(&desc, orig_skb, orig_offset, orig_len,
 342                            max_msg_size, timeo);
 343 }
 344 EXPORT_SYMBOL_GPL(strp_process);
 345
 346 static int strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
 347                      unsigned int orig_offset, size_t orig_len)
 348 {
 349         struct strparser *strp = (struct strparser *)desc->arg.data;
 350
 351         return __strp_recv(desc, orig_skb, orig_offset, orig_len,
 352                            strp->sk->sk_rcvbuf, strp->sk->sk_rcvtimeo);
 353 }
 354
 355 static int default_read_sock_done(struct strparser *strp, int err)
 356 {
 357         return err;
 358 }
 359
 360 /* Called with lock held on lower socket */
 361 static int strp_read_sock(struct strparser *strp)
 362 {
 363         struct socket *sock = strp->sk->sk_socket;
 364         read_descriptor_t desc;
 365
 366         if (unlikely(!sock || !sock->ops || !sock->ops->read_sock))
 367                 return -EBUSY;
 368
 369         desc.arg.data = strp;
 370         desc.error = 0;
 371         desc.count = 1; /* give more than one skb per call */
 372
 373         /* sk should be locked here, so okay to do read_sock */
 374         sock->ops->read_sock(strp->sk, &desc, strp_recv);
 375
 376         desc.error = strp->cb.read_sock_done(strp, desc.error);
 377
 378         return desc.error;
 379 }
 380
 381 /* Lower sock lock held */
 382 void strp_data_ready(struct strparser *strp)
 383 {
 384         if (unlikely(strp->stopped) || strp->paused)
 385                 return;
 386
 387         /* This check is needed to synchronize with do_strp_work.
 388          * do_strp_work acquires a process lock (lock_sock) whereas
 389          * the lock held here is bh_lock_sock. The two locks can be
 390          * held by different threads at the same time, but bh_lock_sock
 391          * allows a thread in BH context to safely check if the process
 392          * lock is held. In this case, if the lock is held, queue work.
 393          */
 394         if (sock_owned_by_user_nocheck(strp->sk)) {
 395                 queue_work(strp_wq, &strp->work);
 396                 return;
 397         }
 398
 399         if (strp->need_bytes) {
 400                 if (strp_peek_len(strp) < strp->need_bytes)
 401                         return;
 402         }
 403
 404         if (strp_read_sock(strp) == -ENOMEM)
 405                 queue_work(strp_wq, &strp->work);
 406 }
 407 EXPORT_SYMBOL_GPL(strp_data_ready);
 408
 409 static void do_strp_work(struct strparser *strp)
 410 {
 411         /* We need the read lock to synchronize with strp_data_ready. We
 412          * need the socket lock for calling strp_read_sock.
 413          */
 414         strp->cb.lock(strp);
 415
 416         if (unlikely(strp->stopped))
 417                 goto out;
 418
 419         if (strp->paused)
 420                 goto out;
 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");