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_rx_msg {
  33         /* Internal cb structure. struct strp_rx_msg must be first for passing
  34          * to upper layer.
  35          */
  36         struct strp_rx_msg strp;
  37         int accum_len;
  38         int early_eaten;
  39 };
  40
  41 static inline struct _strp_rx_msg *_strp_rx_msg(struct sk_buff *skb)
  42 {
  43         return (struct _strp_rx_msg *)((void *)skb->cb +
  44                 offsetof(struct qdisc_skb_cb, data));
  45 }
  46
  47 /* Lower lock held */
  48 static void strp_abort_rx_strp(struct strparser *strp, int err)
  49 {
  50         struct sock *csk = strp->sk;
  51
  52         /* Unrecoverable error in receive */
  53
  54         del_timer(&strp->rx_msg_timer);
  55
  56         if (strp->rx_stopped)
  57                 return;
  58
  59         strp->rx_stopped = 1;
  60
  61         /* Report an error on the lower socket */
  62         csk->sk_err = err;
  63         csk->sk_error_report(csk);
  64 }
  65
  66 static void strp_start_rx_timer(struct strparser *strp)
  67 {
  68         if (strp->sk->sk_rcvtimeo)
  69                 mod_timer(&strp->rx_msg_timer, strp->sk->sk_rcvtimeo);
  70 }
  71
  72 /* Lower lock held */
  73 static void strp_parser_err(struct strparser *strp, int err,
  74                             read_descriptor_t *desc)
  75 {
  76         desc->error = err;
  77         kfree_skb(strp->rx_skb_head);
  78         strp->rx_skb_head = NULL;
  79         strp->cb.abort_parser(strp, err);
  80 }
  81
  82 static inline int strp_peek_len(struct strparser *strp)
  83 {
  84         struct socket *sock = strp->sk->sk_socket;
  85
  86         return sock->ops->peek_len(sock);
  87 }
  88
  89 /* Lower socket lock held */
  90 static int strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
  91                      unsigned int orig_offset, size_t orig_len)
  92 {
  93         struct strparser *strp = (struct strparser *)desc->arg.data;
  94         struct _strp_rx_msg *rxm;
  95         struct sk_buff *head, *skb;
  96         size_t eaten = 0, cand_len;
  97         ssize_t extra;
  98         int err;
  99         bool cloned_orig = false;
 100
 101         if (strp->rx_paused)
 102                 return 0;
 103
 104         head = strp->rx_skb_head;
 105         if (head) {
 106                 /* Message already in progress */
 107
 108                 rxm = _strp_rx_msg(head);
 109                 if (unlikely(rxm->early_eaten)) {
 110                         /* Already some number of bytes on the receive sock
 111                          * data saved in rx_skb_head, just indicate they
 112                          * are consumed.
 113                          */
 114                         eaten = orig_len <= rxm->early_eaten ?
 115                                 orig_len : rxm->early_eaten;
 116                         rxm->early_eaten -= eaten;
 117
 118                         return eaten;
 119                 }
 120
 121                 if (unlikely(orig_offset)) {
 122                         /* Getting data with a non-zero offset when a message is
 123                          * in progress is not expected. If it does happen, we
 124                          * need to clone and pull since we can't deal with
 125                          * offsets in the skbs for a message expect in the head.
 126                          */
 127                         orig_skb = skb_clone(orig_skb, GFP_ATOMIC);
 128                         if (!orig_skb) {
 129                                 STRP_STATS_INCR(strp->stats.rx_mem_fail);
 130                                 desc->error = -ENOMEM;
 131                                 return 0;
 132                         }
 133                         if (!pskb_pull(orig_skb, orig_offset)) {
 134                                 STRP_STATS_INCR(strp->stats.rx_mem_fail);
 135                                 kfree_skb(orig_skb);
 136                                 desc->error = -ENOMEM;
 137                                 return 0;
 138                         }
 139                         cloned_orig = true;
 140                         orig_offset = 0;
 141                 }
 142
 143                 if (!strp->rx_skb_nextp) {
 144                         /* We are going to append to the frags_list of head.
 145                          * Need to unshare the frag_list.
 146                          */
 147                         err = skb_unclone(head, GFP_ATOMIC);
 148                         if (err) {
 149                                 STRP_STATS_INCR(strp->stats.rx_mem_fail);
 150                                 desc->error = err;
 151                                 return 0;
 152                         }
 153
 154                         if (unlikely(skb_shinfo(head)->frag_list)) {
 155                                 /* We can't append to an sk_buff that already
 156                                  * has a frag_list. We create a new head, point
 157                                  * the frag_list of that to the old head, and
 158                                  * then are able to use the old head->next for
 159                                  * appending to the message.
 160                                  */
 161                                 if (WARN_ON(head->next)) {
 162                                         desc->error = -EINVAL;
 163                                         return 0;
 164                                 }
 165
 166                                 skb = alloc_skb(0, GFP_ATOMIC);
 167                                 if (!skb) {
 168                                         STRP_STATS_INCR(strp->stats.rx_mem_fail);
 169                                         desc->error = -ENOMEM;
 170                                         return 0;
 171                                 }
 172                                 skb->len = head->len;
 173                                 skb->data_len = head->len;
 174                                 skb->truesize = head->truesize;
 175                                 *_strp_rx_msg(skb) = *_strp_rx_msg(head);
 176                                 strp->rx_skb_nextp = &head->next;
 177                                 skb_shinfo(skb)->frag_list = head;
 178                                 strp->rx_skb_head = skb;
 179                                 head = skb;
 180                         } else {
 181                                 strp->rx_skb_nextp =
 182                                     &skb_shinfo(head)->frag_list;
 183                         }
 184                 }
 185         }
 186
 187         while (eaten < orig_len) {
 188                 /* Always clone since we will consume something */
 189                 skb = skb_clone(orig_skb, GFP_ATOMIC);
 190                 if (!skb) {
 191                         STRP_STATS_INCR(strp->stats.rx_mem_fail);
 192                         desc->error = -ENOMEM;
 193                         break;
 194                 }
 195
 196                 cand_len = orig_len - eaten;
 197
 198                 head = strp->rx_skb_head;
 199                 if (!head) {
 200                         head = skb;
 201                         strp->rx_skb_head = head;
 202                         /* Will set rx_skb_nextp on next packet if needed */
 203                         strp->rx_skb_nextp = NULL;
 204                         rxm = _strp_rx_msg(head);
 205                         memset(rxm, 0, sizeof(*rxm));
 206                         rxm->strp.offset = orig_offset + eaten;
 207                 } else {
 208                         /* Unclone since we may be appending to an skb that we
 209                          * already share a frag_list with.
 210                          */
 211                         err = skb_unclone(skb, GFP_ATOMIC);
 212                         if (err) {
 213                                 STRP_STATS_INCR(strp->stats.rx_mem_fail);
 214                                 desc->error = err;
 215                                 break;
 216                         }
 217
 218                         rxm = _strp_rx_msg(head);
 219                         *strp->rx_skb_nextp = skb;
 220                         strp->rx_skb_nextp = &skb->next;
 221                         head->data_len += skb->len;
 222                         head->len += skb->len;
 223                         head->truesize += skb->truesize;
 224                 }
 225
 226                 if (!rxm->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 (!rxm->accum_len) {
 234                                         /* Start RX timer for new message */
 235                                         strp_start_rx_timer(strp);
 236                                 }
 237                                 rxm->accum_len += cand_len;
 238                                 eaten += cand_len;
 239                                 STRP_STATS_INCR(strp->stats.rx_need_more_hdr);
 240                                 WARN_ON(eaten != orig_len);
 241                                 break;
 242                         } else if (len < 0) {
 243                                 if (len == -ESTRPIPE && rxm->accum_len) {
 244                                         len = -ENODATA;
 245                                         strp->rx_unrecov_intr = 1;
 246                                 } else {
 247                                         strp->rx_interrupted = 1;
 248                                 }
 249                                 strp_parser_err(strp, len, desc);
 250                                 break;
 251                         } else if (len > strp->sk->sk_rcvbuf) {
 252                                 /* Message length exceeds maximum allowed */
 253                                 STRP_STATS_INCR(strp->stats.rx_msg_too_big);
 254                                 strp_parser_err(strp, -EMSGSIZE, desc);
 255                                 break;
 256                         } else if (len <= (ssize_t)head->len -
 257                                           skb->len - rxm->strp.offset) {
 258                                 /* Length must be into new skb (and also
 259                                  * greater than zero)
 260                                  */
 261                                 STRP_STATS_INCR(strp->stats.rx_bad_hdr_len);
 262                                 strp_parser_err(strp, -EPROTO, desc);
 263                                 break;
 264                         }
 265
 266                         rxm->strp.full_len = len;
 267                 }
 268
 269                 extra = (ssize_t)(rxm->accum_len + cand_len) -
 270                         rxm->strp.full_len;
 271
 272                 if (extra < 0) {
 273                         /* Message not complete yet. */
 274                         if (rxm->strp.full_len - rxm->accum_len >
 275                             strp_peek_len(strp)) {
 276                                 /* Don't have the whole messages in the socket
 277                                  * buffer. Set strp->rx_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 (!rxm->accum_len) {
 284                                         /* Start RX timer for new message */
 285                                         strp_start_rx_timer(strp);
 286                                 }
 287
 288                                 strp->rx_need_bytes = rxm->strp.full_len -
 289                                                        rxm->accum_len;
 290                                 rxm->accum_len += cand_len;
 291                                 rxm->early_eaten = cand_len;
 292                                 STRP_STATS_ADD(strp->stats.rx_bytes, cand_len);
 293                                 desc->count = 0; /* Stop reading socket */
 294                                 break;
 295                         }
 296                         rxm->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                 del_timer(&strp->rx_msg_timer);
 312                 strp->rx_skb_head = NULL;
 313                 STRP_STATS_INCR(strp->stats.rx_msgs);
 314
 315                 /* Give skb to upper layer */
 316                 strp->cb.rcv_msg(strp, head);
 317
 318                 if (unlikely(strp->rx_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.rx_bytes, eaten);
 328
 329         return eaten;
 330 }
 331
 332 static int default_read_sock_done(struct strparser *strp, int err)
 333 {
 334         return err;
 335 }
 336
 337 /* Called with lock held on lower socket */
 338 static int strp_read_sock(struct strparser *strp)
 339 {
 340         struct socket *sock = strp->sk->sk_socket;
 341         read_descriptor_t desc;
 342
 343         desc.arg.data = strp;
 344         desc.error = 0;
 345         desc.count = 1; /* give more than one skb per call */
 346
 347         /* sk should be locked here, so okay to do read_sock */
 348         sock->ops->read_sock(strp->sk, &desc, strp_recv);
 349
 350         desc.error = strp->cb.read_sock_done(strp, desc.error);
 351
 352         return desc.error;
 353 }
 354
 355 /* Lower sock lock held */
 356 void strp_data_ready(struct strparser *strp)
 357 {
 358         if (unlikely(strp->rx_stopped))
 359                 return;
 360
 361         /* This check is needed to synchronize with do_strp_rx_work.
 362          * do_strp_rx_work acquires a process lock (lock_sock) whereas
 363          * the lock held here is bh_lock_sock. The two locks can be
 364          * held by different threads at the same time, but bh_lock_sock
 365          * allows a thread in BH context to safely check if the process
 366          * lock is held. In this case, if the lock is held, queue work.
 367          */
 368         if (sock_owned_by_user(strp->sk)) {
 369                 queue_work(strp_wq, &strp->rx_work);
 370                 return;
 371         }
 372
 373         if (strp->rx_paused)
 374                 return;
 375
 376         if (strp->rx_need_bytes) {
 377                 if (strp_peek_len(strp) >= strp->rx_need_bytes)
 378                         strp->rx_need_bytes = 0;
 379                 else
 380                         return;
 381         }
 382
 383         if (strp_read_sock(strp) == -ENOMEM)
 384                 queue_work(strp_wq, &strp->rx_work);
 385 }
 386 EXPORT_SYMBOL_GPL(strp_data_ready);
 387
 388 static void do_strp_rx_work(struct strparser *strp)
 389 {
 390         read_descriptor_t rd_desc;
 391         struct sock *csk = strp->sk;
 392
 393         /* We need the read lock to synchronize with strp_data_ready. We
 394          * need the socket lock for calling strp_read_sock.
 395          */
 396         lock_sock(csk);
 397
 398         if (unlikely(strp->rx_stopped))
 399                 goto out;
 400
 401         if (strp->rx_paused)
 402                 goto out;
 403
 404         rd_desc.arg.data = strp;
 405
 406         if (strp_read_sock(strp) == -ENOMEM)
 407                 queue_work(strp_wq, &strp->rx_work);
 408
 409 out:
 410         release_sock(csk);
 411 }
 412
 413 static void strp_rx_work(struct work_struct *w)
 414 {
 415         do_strp_rx_work(container_of(w, struct strparser, rx_work));
 416 }
 417
 418 static void strp_rx_msg_timeout(unsigned long arg)
 419 {
 420         struct strparser *strp = (struct strparser *)arg;
 421
 422         /* Message assembly timed out */
 423         STRP_STATS_INCR(strp->stats.rx_msg_timeouts);
 424         lock_sock(strp->sk);
 425         strp->cb.abort_parser(strp, ETIMEDOUT);
 426         release_sock(strp->sk);
 427 }
 428
 429 int strp_init(struct strparser *strp, struct sock *csk,
 430               struct strp_callbacks *cb)
 431 {
 432         struct socket *sock = csk->sk_socket;
 433
 434         if (!cb || !cb->rcv_msg || !cb->parse_msg)
 435                 return -EINVAL;
 436
 437         if (!sock->ops->read_sock || !sock->ops->peek_len)
 438                 return -EAFNOSUPPORT;
 439
 440         memset(strp, 0, sizeof(*strp));
 441
 442         strp->sk = csk;
 443
 444         setup_timer(&strp->rx_msg_timer, strp_rx_msg_timeout,
 445                     (unsigned long)strp);
 446
 447         INIT_WORK(&strp->rx_work, strp_rx_work);
 448
 449         strp->cb.rcv_msg = cb->rcv_msg;
 450         strp->cb.parse_msg = cb->parse_msg;
 451         strp->cb.read_sock_done = cb->read_sock_done ? : default_read_sock_done;
 452         strp->cb.abort_parser = cb->abort_parser ? : strp_abort_rx_strp;
 453
 454         return 0;
 455 }
 456 EXPORT_SYMBOL_GPL(strp_init);
 457
 458 void strp_unpause(struct strparser *strp)
 459 {
 460         strp->rx_paused = 0;
 461
 462         /* Sync setting rx_paused with RX work */
 463         smp_mb();
 464
 465         queue_work(strp_wq, &strp->rx_work);
 466 }
 467 EXPORT_SYMBOL_GPL(strp_unpause);
 468
 469 /* strp must already be stopped so that strp_recv will no longer be called.
 470  * Note that strp_done is not called with the lower socket held.
 471  */
 472 void strp_done(struct strparser *strp)
 473 {
 474         WARN_ON(!strp->rx_stopped);
 475
 476         del_timer_sync(&strp->rx_msg_timer);
 477         cancel_work_sync(&strp->rx_work);
 478
 479         if (strp->rx_skb_head) {
 480                 kfree_skb(strp->rx_skb_head);
 481                 strp->rx_skb_head = NULL;
 482         }
 483 }
 484 EXPORT_SYMBOL_GPL(strp_done);
 485
 486 void strp_stop(struct strparser *strp)
 487 {
 488         strp->rx_stopped = 1;
 489 }
 490 EXPORT_SYMBOL_GPL(strp_stop);
 491
 492 void strp_check_rcv(struct strparser *strp)
 493 {
 494         queue_work(strp_wq, &strp->rx_work);
 495 }
 496 EXPORT_SYMBOL_GPL(strp_check_rcv);
 497
 498 static int __init strp_mod_init(void)
 499 {
 500         strp_wq = create_singlethread_workqueue("kstrp");
 501
 502         return 0;
 503 }
 504
 505 static void __exit strp_mod_exit(void)
 506 {
 507         destroy_workqueue(strp_wq);
 508 }
 509 module_init(strp_mod_init);
 510 module_exit(strp_mod_exit);
 511 MODULE_LICENSE("GPL");