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/export.h>
  18 #include <linux/init.h>
  19 #include <linux/net.h>
  20 #include <linux/netdevice.h>
  21 #include <linux/poll.h>
  22 #include <linux/rculist.h>
  23 #include <linux/skbuff.h>
  24 #include <linux/socket.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/workqueue.h>
  27 #include <net/strparser.h>
  28 #include <net/netns/generic.h>
  29 #include <net/sock.h>
  30
  31 static struct workqueue_struct *strp_wq;
  32
  33 struct _strp_msg {
  34         /* Internal cb structure. struct strp_msg must be first for passing
  35          * to upper layer.
  36          */
  37         struct strp_msg strp;
  38         int accum_len;
  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                 if (unlikely(orig_offset)) {
 119                         /* Getting data with a non-zero offset when a message is
 120                          * in progress is not expected. If it does happen, we
 121                          * need to clone and pull since we can't deal with
 122                          * offsets in the skbs for a message expect in the head.
 123                          */
 124                         orig_skb = skb_clone(orig_skb, GFP_ATOMIC);
 125                         if (!orig_skb) {
 126                                 STRP_STATS_INCR(strp->stats.mem_fail);
 127                                 desc->error = -ENOMEM;
 128                                 return 0;
 129                         }
 130                         if (!pskb_pull(orig_skb, orig_offset)) {
 131                                 STRP_STATS_INCR(strp->stats.mem_fail);
 132                                 kfree_skb(orig_skb);
 133                                 desc->error = -ENOMEM;
 134                                 return 0;
 135                         }
 136                         cloned_orig = true;
 137                         orig_offset = 0;
 138                 }
 139
 140                 if (!strp->skb_nextp) {
 141                         /* We are going to append to the frags_list of head.
 142                          * Need to unshare the frag_list.
 143                          */
 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                         if (unlikely(skb_shinfo(head)->frag_list)) {
 152                                 /* We can't append to an sk_buff that already
 153                                  * has a frag_list. We create a new head, point
 154                                  * the frag_list of that to the old head, and
 155                                  * then are able to use the old head->next for
 156                                  * appending to the message.
 157                                  */
 158                                 if (WARN_ON(head->next)) {
 159                                         desc->error = -EINVAL;
 160                                         return 0;
 161                                 }
 162
 163                                 skb = alloc_skb(0, GFP_ATOMIC);
 164                                 if (!skb) {
 165                                         STRP_STATS_INCR(strp->stats.mem_fail);
 166                                         desc->error = -ENOMEM;
 167                                         return 0;
 168                                 }
 169                                 skb->len = head->len;
 170                                 skb->data_len = head->len;
 171                                 skb->truesize = head->truesize;
 172                                 *_strp_msg(skb) = *_strp_msg(head);
 173                                 strp->skb_nextp = &head->next;
 174                                 skb_shinfo(skb)->frag_list = head;
 175                                 strp->skb_head = skb;
 176                                 head = skb;
 177                         } else {
 178                                 strp->skb_nextp =
 179                                     &skb_shinfo(head)->frag_list;
 180                         }
 181                 }
 182         }
 183
 184         while (eaten < orig_len) {
 185                 /* Always clone since we will consume something */
 186                 skb = skb_clone(orig_skb, GFP_ATOMIC);
 187                 if (!skb) {
 188                         STRP_STATS_INCR(strp->stats.mem_fail);
 189                         desc->error = -ENOMEM;
 190                         break;
 191                 }
 192
 193                 cand_len = orig_len - eaten;
 194
 195                 head = strp->skb_head;
 196                 if (!head) {
 197                         head = skb;
 198                         strp->skb_head = head;
 199                         /* Will set skb_nextp on next packet if needed */
 200                         strp->skb_nextp = NULL;
 201                         stm = _strp_msg(head);
 202                         memset(stm, 0, sizeof(*stm));
 203                         stm->strp.offset = orig_offset + eaten;
 204                 } else {
 205                         /* Unclone if we are appending to an skb that we
 206                          * already share a frag_list with.
 207                          */
 208                         if (skb_has_frag_list(skb)) {
 209                                 err = skb_unclone(skb, GFP_ATOMIC);
 210                                 if (err) {
 211                                         STRP_STATS_INCR(strp->stats.mem_fail);
 212                                         desc->error = err;
 213                                         break;
 214                                 }
 215                         }
 216
 217                         stm = _strp_msg(head);
 218                         *strp->skb_nextp = skb;
 219                         strp->skb_nextp = &skb->next;
 220                         head->data_len += skb->len;
 221                         head->len += skb->len;
 222                         head->truesize += skb->truesize;
 223                 }
 224
 225                 if (!stm->strp.full_len) {
 226                         ssize_t len;
 227
 228                         len = (*strp->cb.parse_msg)(strp, head);
 229
 230                         if (!len) {
 231                                 /* Need more header to determine length */
 232                                 if (!stm->accum_len) {
 233                                         /* Start RX timer for new message */
 234                                         strp_start_timer(strp, timeo);
 235                                 }
 236                                 stm->accum_len += cand_len;
 237                                 eaten += cand_len;
 238                                 STRP_STATS_INCR(strp->stats.need_more_hdr);
 239                                 WARN_ON(eaten != orig_len);
 240                                 break;
 241                         } else if (len < 0) {
 242                                 if (len == -ESTRPIPE && stm->accum_len) {
 243                                         len = -ENODATA;
 244                                         strp->unrecov_intr = 1;
 245                                 } else {
 246                                         strp->interrupted = 1;
 247                                 }
 248                                 strp_parser_err(strp, len, desc);
 249                                 break;
 250                         } else if (len > max_msg_size) {
 251                                 /* Message length exceeds maximum allowed */
 252                                 STRP_STATS_INCR(strp->stats.msg_too_big);
 253                                 strp_parser_err(strp, -EMSGSIZE, desc);
 254                                 break;
 255                         } else if (len <= (ssize_t)head->len -
 256                                           skb->len - stm->strp.offset) {
 257                                 /* Length must be into new skb (and also
 258                                  * greater than zero)
 259                                  */
 260                                 STRP_STATS_INCR(strp->stats.bad_hdr_len);
 261                                 strp_parser_err(strp, -EPROTO, desc);
 262                                 break;
 263                         }
 264
 265                         stm->strp.full_len = len;
 266                 }
 267
 268                 extra = (ssize_t)(stm->accum_len + cand_len) -
 269                         stm->strp.full_len;
 270
 271                 if (extra < 0) {
 272                         /* Message not complete yet. */
 273                         if (stm->strp.full_len - stm->accum_len >
 274                             strp_peek_len(strp)) {
 275                                 /* Don't have the whole message in the socket
 276                                  * buffer. Set strp->need_bytes to wait for
 277                                  * the rest of the message. Also, set "early
 278                                  * eaten" since we've already buffered the skb
 279                                  * but don't consume yet per strp_read_sock.
 280                                  */
 281
 282                                 if (!stm->accum_len) {
 283                                         /* Start RX timer for new message */
 284                                         strp_start_timer(strp, timeo);
 285                                 }
 286
 287                                 stm->accum_len += cand_len;
 288                                 eaten += cand_len;
 289                                 strp->need_bytes = stm->strp.full_len -
 290                                                        stm->accum_len;
 291                                 STRP_STATS_ADD(strp->stats.bytes, cand_len);
 292                                 desc->count = 0; /* Stop reading socket */
 293                                 break;
 294                         }
 295                         stm->accum_len += cand_len;
 296                         eaten += cand_len;
 297                         WARN_ON(eaten != orig_len);
 298                         break;
 299                 }
 300
 301                 /* Positive extra indicates more bytes than needed for the
 302                  * message
 303                  */
 304
 305                 WARN_ON(extra > cand_len);
 306
 307                 eaten += (cand_len - extra);
 308
 309                 /* Hurray, we have a new message! */
 310                 cancel_delayed_work(&strp->msg_timer_work);
 311                 strp->skb_head = NULL;
 312                 strp->need_bytes = 0;
 313                 STRP_STATS_INCR(strp->stats.msgs);
 314
 315                 /* Give skb to upper layer */
 316                 strp->cb.rcv_msg(strp, head);
 317
 318                 if (unlikely(strp->paused)) {
 319                         /* Upper layer paused strp */
 320                         break;
 321                 }
 322         }
 323
 324         if (cloned_orig)
 325                 kfree_skb(orig_skb);
 326
 327         STRP_STATS_ADD(strp->stats.bytes, eaten);
 328
 329         return eaten;
 330 }
 331
 332 int strp_process(struct strparser *strp, struct sk_buff *orig_skb,
 333                  unsigned int orig_offset, size_t orig_len,
 334                  size_t max_msg_size, long timeo)
 335 {
 336         read_descriptor_t desc; /* Dummy arg to strp_recv */
 337
 338         desc.arg.data = strp;
 339
 340         return __strp_recv(&desc, orig_skb, orig_offset, orig_len,
 341                            max_msg_size, timeo);
 342 }
 343 EXPORT_SYMBOL_GPL(strp_process);
 344
 345 static int strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
 346                      unsigned int orig_offset, size_t orig_len)
 347 {
 348         struct strparser *strp = (struct strparser *)desc->arg.data;
 349
 350         return __strp_recv(desc, orig_skb, orig_offset, orig_len,
 351                            strp->sk->sk_rcvbuf, strp->sk->sk_rcvtimeo);
 352 }
 353
 354 static int default_read_sock_done(struct strparser *strp, int err)
 355 {
 356         return err;
 357 }
 358
 359 /* Called with lock held on lower socket */
 360 static int strp_read_sock(struct strparser *strp)
 361 {
 362         struct socket *sock = strp->sk->sk_socket;
 363         read_descriptor_t desc;
 364
 365         if (unlikely(!sock || !sock->ops || !sock->ops->read_sock))
 366                 return -EBUSY;
 367
 368         desc.arg.data = strp;
 369         desc.error = 0;
 370         desc.count = 1; /* give more than one skb per call */
 371
 372         /* sk should be locked here, so okay to do read_sock */
 373         sock->ops->read_sock(strp->sk, &desc, strp_recv);
 374
 375         desc.error = strp->cb.read_sock_done(strp, desc.error);
 376
 377         return desc.error;
 378 }
 379
 380 /* Lower sock lock held */
 381 void strp_data_ready(struct strparser *strp)
 382 {
 383         if (unlikely(strp->stopped) || strp->paused)
 384                 return;
 385
 386         /* This check is needed to synchronize with do_strp_work.
 387          * do_strp_work acquires a process lock (lock_sock) whereas
 388          * the lock held here is bh_lock_sock. The two locks can be
 389          * held by different threads at the same time, but bh_lock_sock
 390          * allows a thread in BH context to safely check if the process
 391          * lock is held. In this case, if the lock is held, queue work.
 392          */
 393         if (sock_owned_by_user_nocheck(strp->sk)) {
 394                 queue_work(strp_wq, &strp->work);
 395                 return;
 396         }
 397
 398         if (strp->need_bytes) {
 399                 if (strp_peek_len(strp) < strp->need_bytes)
 400                         return;
 401         }
 402
 403         if (strp_read_sock(strp) == -ENOMEM)
 404                 queue_work(strp_wq, &strp->work);
 405 }
 406 EXPORT_SYMBOL_GPL(strp_data_ready);
 407
 408 static void do_strp_work(struct strparser *strp)
 409 {
 410         /* We need the read lock to synchronize with strp_data_ready. We
 411          * need the socket lock for calling strp_read_sock.
 412          */
 413         strp->cb.lock(strp);
 414
 415         if (unlikely(strp->stopped))
 416                 goto out;
 417
 418         if (strp->paused)
 419                 goto out;
 420
 421         if (strp_read_sock(strp) == -ENOMEM)
 422                 queue_work(strp_wq, &strp->work);
 423
 424 out:
 425         strp->cb.unlock(strp);
 426 }
 427
 428 static void strp_work(struct work_struct *w)
 429 {
 430         do_strp_work(container_of(w, struct strparser, work));
 431 }
 432
 433 static void strp_msg_timeout(struct work_struct *w)
 434 {
 435         struct strparser *strp = container_of(w, struct strparser,
 436                                               msg_timer_work.work);
 437
 438         /* Message assembly timed out */
 439         STRP_STATS_INCR(strp->stats.msg_timeouts);
 440         strp->cb.lock(strp);
 441         strp->cb.abort_parser(strp, -ETIMEDOUT);
 442         strp->cb.unlock(strp);
 443 }
 444
 445 static void strp_sock_lock(struct strparser *strp)
 446 {
 447         lock_sock(strp->sk);
 448 }
 449
 450 static void strp_sock_unlock(struct strparser *strp)
 451 {
 452         release_sock(strp->sk);
 453 }
 454
 455 int strp_init(struct strparser *strp, struct sock *sk,
 456               const struct strp_callbacks *cb)
 457 {
 458
 459         if (!cb || !cb->rcv_msg || !cb->parse_msg)
 460                 return -EINVAL;
 461
 462         /* The sk (sock) arg determines the mode of the stream parser.
 463          *
 464          * If the sock is set then the strparser is in receive callback mode.
 465          * The upper layer calls strp_data_ready to kick receive processing
 466          * and strparser calls the read_sock function on the socket to
 467          * get packets.
 468          *
 469          * If the sock is not set then the strparser is in general mode.
 470          * The upper layer calls strp_process for each skb to be parsed.
 471          */
 472
 473         if (!sk) {
 474                 if (!cb->lock || !cb->unlock)
 475                         return -EINVAL;
 476         }
 477
 478         memset(strp, 0, sizeof(*strp));
 479
 480         strp->sk = sk;
 481
 482         strp->cb.lock = cb->lock ? : strp_sock_lock;
 483         strp->cb.unlock = cb->unlock ? : strp_sock_unlock;
 484         strp->cb.rcv_msg = cb->rcv_msg;
 485         strp->cb.parse_msg = cb->parse_msg;
 486         strp->cb.read_sock_done = cb->read_sock_done ? : default_read_sock_done;
 487         strp->cb.abort_parser = cb->abort_parser ? : strp_abort_strp;
 488
 489         INIT_DELAYED_WORK(&strp->msg_timer_work, strp_msg_timeout);
 490         INIT_WORK(&strp->work, strp_work);
 491
 492         return 0;
 493 }
 494 EXPORT_SYMBOL_GPL(strp_init);
 495
 496 /* Sock process lock held (lock_sock) */
 497 void __strp_unpause(struct strparser *strp)
 498 {
 499         strp->paused = 0;
 500
 501         if (strp->need_bytes) {
 502                 if (strp_peek_len(strp) < strp->need_bytes)
 503                         return;
 504         }
 505         strp_read_sock(strp);
 506 }
 507 EXPORT_SYMBOL_GPL(__strp_unpause);
 508
 509 void strp_unpause(struct strparser *strp)
 510 {
 511         strp->paused = 0;
 512
 513         /* Sync setting paused with RX work */
 514         smp_mb();
 515
 516         queue_work(strp_wq, &strp->work);
 517 }
 518 EXPORT_SYMBOL_GPL(strp_unpause);
 519
 520 /* strp must already be stopped so that strp_recv will no longer be called.
 521  * Note that strp_done is not called with the lower socket held.
 522  */
 523 void strp_done(struct strparser *strp)
 524 {
 525         WARN_ON(!strp->stopped);
 526
 527         cancel_delayed_work_sync(&strp->msg_timer_work);
 528         cancel_work_sync(&strp->work);
 529
 530         if (strp->skb_head) {
 531                 kfree_skb(strp->skb_head);
 532                 strp->skb_head = NULL;
 533         }
 534 }
 535 EXPORT_SYMBOL_GPL(strp_done);
 536
 537 void strp_stop(struct strparser *strp)
 538 {
 539         strp->stopped = 1;
 540 }
 541 EXPORT_SYMBOL_GPL(strp_stop);
 542
 543 void strp_check_rcv(struct strparser *strp)
 544 {
 545         queue_work(strp_wq, &strp->work);
 546 }
 547 EXPORT_SYMBOL_GPL(strp_check_rcv);
 548
 549 static int __init strp_dev_init(void)
 550 {
 551         strp_wq = create_singlethread_workqueue("kstrp");
 552         if (unlikely(!strp_wq))
 553                 return -ENOMEM;
 554
 555         return 0;
 556 }
 557 device_initcall(strp_dev_init);