net/core/datagram.c

   1 /*
   2  *      SUCS NET3:
   3  *
   4  *      Generic datagram handling routines. These are generic for all
   5  *      protocols. Possibly a generic IP version on top of these would
   6  *      make sense. Not tonight however 8-).
   7  *      This is used because UDP, RAW, PACKET, DDP, IPX, AX.25 and
   8  *      NetROM layer all have identical poll code and mostly
   9  *      identical recvmsg() code. So we share it here. The poll was
  10  *      shared before but buried in udp.c so I moved it.
  11  *
  12  *      Authors:        Alan Cox <alan@lxorguk.ukuu.org.uk>. (datagram_poll() from old
  13  *                                                   udp.c code)
  14  *
  15  *      Fixes:
  16  *              Alan Cox        :       NULL return from skb_peek_copy()
  17  *                                      understood
  18  *              Alan Cox        :       Rewrote skb_read_datagram to avoid the
  19  *                                      skb_peek_copy stuff.
  20  *              Alan Cox        :       Added support for SOCK_SEQPACKET.
  21  *                                      IPX can no longer use the SO_TYPE hack
  22  *                                      but AX.25 now works right, and SPX is
  23  *                                      feasible.
  24  *              Alan Cox        :       Fixed write poll of non IP protocol
  25  *                                      crash.
  26  *              Florian  La Roche:      Changed for my new skbuff handling.
  27  *              Darryl Miles    :       Fixed non-blocking SOCK_SEQPACKET.
  28  *              Linus Torvalds  :       BSD semantic fixes.
  29  *              Alan Cox        :       Datagram iovec handling
  30  *              Darryl Miles    :       Fixed non-blocking SOCK_STREAM.
  31  *              Alan Cox        :       POSIXisms
  32  *              Pete Wyckoff    :       Unconnected accept() fix.
  33  *
  34  */
  35
  36 #include <linux/module.h>
  37 #include <linux/types.h>
  38 #include <linux/kernel.h>
  39 #include <asm/uaccess.h>
  40 #include <linux/mm.h>
  41 #include <linux/interrupt.h>
  42 #include <linux/errno.h>
  43 #include <linux/sched.h>
  44 #include <linux/inet.h>
  45 #include <linux/netdevice.h>
  46 #include <linux/rtnetlink.h>
  47 #include <linux/poll.h>
  48 #include <linux/highmem.h>
  49 #include <linux/spinlock.h>
  50 #include <linux/slab.h>
  51
  52 #include <net/protocol.h>
  53 #include <linux/skbuff.h>
  54
  55 #include <net/checksum.h>
  56 #include <net/sock.h>
  57 #include <net/tcp_states.h>
  58 #include <trace/events/skb.h>
  59
  60 /*
  61  *      Is a socket 'connection oriented' ?
  62  */
  63 static inline int connection_based(struct sock *sk)
  64 {
  65         return sk->sk_type == SOCK_SEQPACKET || sk->sk_type == SOCK_STREAM;
  66 }
  67
  68 static int receiver_wake_function(wait_queue_t *wait, unsigned int mode, int sync,
  69                                   void *key)
  70 {
  71         unsigned long bits = (unsigned long)key;
  72
  73         /*
  74          * Avoid a wakeup if event not interesting for us
  75          */
  76         if (bits && !(bits & (POLLIN | POLLERR)))
  77                 return 0;
  78         return autoremove_wake_function(wait, mode, sync, key);
  79 }
  80 /*
  81  * Wait for a packet..
  82  */
  83 static int wait_for_packet(struct sock *sk, int *err, long *timeo_p)
  84 {
  85         int error;
  86         DEFINE_WAIT_FUNC(wait, receiver_wake_function);
  87
  88         prepare_to_wait_exclusive(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
  89
  90         /* Socket errors? */
  91         error = sock_error(sk);
  92         if (error)
  93                 goto out_err;
  94
  95         if (!skb_queue_empty(&sk->sk_receive_queue))
  96                 goto out;
  97
  98         /* Socket shut down? */
  99         if (sk->sk_shutdown & RCV_SHUTDOWN)
 100                 goto out_noerr;
 101
 102         /* Sequenced packets can come disconnected.
 103          * If so we report the problem
 104          */
 105         error = -ENOTCONN;
 106         if (connection_based(sk) &&
 107             !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN))
 108                 goto out_err;
 109
 110         /* handle signals */
 111         if (signal_pending(current))
 112                 goto interrupted;
 113
 114         error = 0;
 115         *timeo_p = schedule_timeout(*timeo_p);
 116 out:
 117         finish_wait(sk_sleep(sk), &wait);
 118         return error;
 119 interrupted:
 120         error = sock_intr_errno(*timeo_p);
 121 out_err:
 122         *err = error;
 123         goto out;
 124 out_noerr:
 125         *err = 0;
 126         error = 1;
 127         goto out;
 128 }
 129
 130 /**
 131  *      __skb_recv_datagram - Receive a datagram skbuff
 132  *      @sk: socket
 133  *      @flags: MSG_ flags
 134  *      @off: an offset in bytes to peek skb from. Returns an offset
 135  *            within an skb where data actually starts
 136  *      @peeked: returns non-zero if this packet has been seen before
 137  *      @err: error code returned
 138  *
 139  *      Get a datagram skbuff, understands the peeking, nonblocking wakeups
 140  *      and possible races. This replaces identical code in packet, raw and
 141  *      udp, as well as the IPX AX.25 and Appletalk. It also finally fixes
 142  *      the long standing peek and read race for datagram sockets. If you
 143  *      alter this routine remember it must be re-entrant.
 144  *
 145  *      This function will lock the socket if a skb is returned, so the caller
 146  *      needs to unlock the socket in that case (usually by calling
 147  *      skb_free_datagram)
 148  *
 149  *      * It does not lock socket since today. This function is
 150  *      * free of race conditions. This measure should/can improve
 151  *      * significantly datagram socket latencies at high loads,
 152  *      * when data copying to user space takes lots of time.
 153  *      * (BTW I've just killed the last cli() in IP/IPv6/core/netlink/packet
 154  *      *  8) Great win.)
 155  *      *                                           --ANK (980729)
 156  *
 157  *      The order of the tests when we find no data waiting are specified
 158  *      quite explicitly by POSIX 1003.1g, don't change them without having
 159  *      the standard around please.
 160  */
 161 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
 162                                     int *peeked, int *off, int *err)
 163 {
 164         struct sk_buff *skb;
 165         long timeo;
 166         /*
 167          * Caller is allowed not to check sk->sk_err before skb_recv_datagram()
 168          */
 169         int error = sock_error(sk);
 170
 171         if (error)
 172                 goto no_packet;
 173
 174         timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 175
 176         do {
 177                 /* Again only user level code calls this function, so nothing
 178                  * interrupt level will suddenly eat the receive_queue.
 179                  *
 180                  * Look at current nfs client by the way...
 181                  * However, this function was correct in any case. 8)
 182                  */
 183                 unsigned long cpu_flags;
 184                 struct sk_buff_head *queue = &sk->sk_receive_queue;
 185
 186                 spin_lock_irqsave(&queue->lock, cpu_flags);
 187                 skb_queue_walk(queue, skb) {
 188                         *peeked = skb->peeked;
 189                         if (flags & MSG_PEEK) {
 190                                 if (*off >= skb->len) {
 191                                         *off -= skb->len;
 192                                         continue;
 193                                 }
 194                                 skb->peeked = 1;
 195                                 atomic_inc(&skb->users);
 196                         } else
 197                                 __skb_unlink(skb, queue);
 198
 199                         spin_unlock_irqrestore(&queue->lock, cpu_flags);
 200                         return skb;
 201                 }
 202                 spin_unlock_irqrestore(&queue->lock, cpu_flags);
 203
 204                 /* User doesn't want to wait */
 205                 error = -EAGAIN;
 206                 if (!timeo)
 207                         goto no_packet;
 208
 209         } while (!wait_for_packet(sk, err, &timeo));
 210
 211         return NULL;
 212
 213 no_packet:
 214         *err = error;
 215         return NULL;
 216 }
 217 EXPORT_SYMBOL(__skb_recv_datagram);
 218
 219 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags,
 220                                   int noblock, int *err)
 221 {
 222         int peeked, off = 0;
 223
 224         return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
 225                                    &peeked, &off, err);
 226 }
 227 EXPORT_SYMBOL(skb_recv_datagram);
 228
 229 void skb_free_datagram(struct sock *sk, struct sk_buff *skb)
 230 {
 231         consume_skb(skb);
 232         sk_mem_reclaim_partial(sk);
 233 }
 234 EXPORT_SYMBOL(skb_free_datagram);
 235
 236 void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb)
 237 {
 238         bool slow;
 239
 240         if (likely(atomic_read(&skb->users) == 1))
 241                 smp_rmb();
 242         else if (likely(!atomic_dec_and_test(&skb->users)))
 243                 return;
 244
 245         slow = lock_sock_fast(sk);
 246         skb_orphan(skb);
 247         sk_mem_reclaim_partial(sk);
 248         unlock_sock_fast(sk, slow);
 249
 250         /* skb is now orphaned, can be freed outside of locked section */
 251         __kfree_skb(skb);
 252 }
 253 EXPORT_SYMBOL(skb_free_datagram_locked);
 254
 255 /**
 256  *      skb_kill_datagram - Free a datagram skbuff forcibly
 257  *      @sk: socket
 258  *      @skb: datagram skbuff
 259  *      @flags: MSG_ flags
 260  *
 261  *      This function frees a datagram skbuff that was received by
 262  *      skb_recv_datagram.  The flags argument must match the one
 263  *      used for skb_recv_datagram.
 264  *
 265  *      If the MSG_PEEK flag is set, and the packet is still on the
 266  *      receive queue of the socket, it will be taken off the queue
 267  *      before it is freed.
 268  *
 269  *      This function currently only disables BH when acquiring the
 270  *      sk_receive_queue lock.  Therefore it must not be used in a
 271  *      context where that lock is acquired in an IRQ context.
 272  *
 273  *      It returns 0 if the packet was removed by us.
 274  */
 275
 276 int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)
 277 {
 278         int err = 0;
 279
 280         if (flags & MSG_PEEK) {
 281                 err = -ENOENT;
 282                 spin_lock_bh(&sk->sk_receive_queue.lock);
 283                 if (skb == skb_peek(&sk->sk_receive_queue)) {
 284                         __skb_unlink(skb, &sk->sk_receive_queue);
 285                         atomic_dec(&skb->users);
 286                         err = 0;
 287                 }
 288                 spin_unlock_bh(&sk->sk_receive_queue.lock);
 289         }
 290
 291         kfree_skb(skb);
 292         atomic_inc(&sk->sk_drops);
 293         sk_mem_reclaim_partial(sk);
 294
 295         return err;
 296 }
 297 EXPORT_SYMBOL(skb_kill_datagram);
 298
 299 /**
 300  *      skb_copy_datagram_iovec - Copy a datagram to an iovec.
 301  *      @skb: buffer to copy
 302  *      @offset: offset in the buffer to start copying from
 303  *      @to: io vector to copy to
 304  *      @len: amount of data to copy from buffer to iovec
 305  *
 306  *      Note: the iovec is modified during the copy.
 307  */
 308 int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,
 309                             struct iovec *to, int len)
 310 {
 311         int start = skb_headlen(skb);
 312         int i, copy = start - offset;
 313         struct sk_buff *frag_iter;
 314
 315         trace_skb_copy_datagram_iovec(skb, len);
 316
 317         /* Copy header. */
 318         if (copy > 0) {
 319                 if (copy > len)
 320                         copy = len;
 321                 if (memcpy_toiovec(to, skb->data + offset, copy))
 322                         goto fault;
 323                 if ((len -= copy) == 0)
 324                         return 0;
 325                 offset += copy;
 326         }
 327
 328         /* Copy paged appendix. Hmm... why does this look so complicated? */
 329         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 330                 int end;
 331                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 332
 333                 WARN_ON(start > offset + len);
 334
 335                 end = start + skb_frag_size(frag);
 336                 if ((copy = end - offset) > 0) {
 337                         int err;
 338                         u8  *vaddr;
 339                         struct page *page = skb_frag_page(frag);
 340
 341                         if (copy > len)
 342                                 copy = len;
 343                         vaddr = kmap(page);
 344                         err = memcpy_toiovec(to, vaddr + frag->page_offset +
 345                                              offset - start, copy);
 346                         kunmap(page);
 347                         if (err)
 348                                 goto fault;
 349                         if (!(len -= copy))
 350                                 return 0;
 351                         offset += copy;
 352                 }
 353                 start = end;
 354         }
 355
 356         skb_walk_frags(skb, frag_iter) {
 357                 int end;
 358
 359                 WARN_ON(start > offset + len);
 360
 361                 end = start + frag_iter->len;
 362                 if ((copy = end - offset) > 0) {
 363                         if (copy > len)
 364                                 copy = len;
 365                         if (skb_copy_datagram_iovec(frag_iter,
 366                                                     offset - start,
 367                                                     to, copy))
 368                                 goto fault;
 369                         if ((len -= copy) == 0)
 370                                 return 0;
 371                         offset += copy;
 372                 }
 373                 start = end;
 374         }
 375         if (!len)
 376                 return 0;
 377
 378 fault:
 379         return -EFAULT;
 380 }
 381 EXPORT_SYMBOL(skb_copy_datagram_iovec);
 382
 383 /**
 384  *      skb_copy_datagram_const_iovec - Copy a datagram to an iovec.
 385  *      @skb: buffer to copy
 386  *      @offset: offset in the buffer to start copying from
 387  *      @to: io vector to copy to
 388  *      @to_offset: offset in the io vector to start copying to
 389  *      @len: amount of data to copy from buffer to iovec
 390  *
 391  *      Returns 0 or -EFAULT.
 392  *      Note: the iovec is not modified during the copy.
 393  */
 394 int skb_copy_datagram_const_iovec(const struct sk_buff *skb, int offset,
 395                                   const struct iovec *to, int to_offset,
 396                                   int len)
 397 {
 398         int start = skb_headlen(skb);
 399         int i, copy = start - offset;
 400         struct sk_buff *frag_iter;
 401
 402         /* Copy header. */
 403         if (copy > 0) {
 404                 if (copy > len)
 405                         copy = len;
 406                 if (memcpy_toiovecend(to, skb->data + offset, to_offset, copy))
 407                         goto fault;
 408                 if ((len -= copy) == 0)
 409                         return 0;
 410                 offset += copy;
 411                 to_offset += copy;
 412         }
 413
 414         /* Copy paged appendix. Hmm... why does this look so complicated? */
 415         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 416                 int end;
 417                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 418
 419                 WARN_ON(start > offset + len);
 420
 421                 end = start + skb_frag_size(frag);
 422                 if ((copy = end - offset) > 0) {
 423                         int err;
 424                         u8  *vaddr;
 425                         struct page *page = skb_frag_page(frag);
 426
 427                         if (copy > len)
 428                                 copy = len;
 429                         vaddr = kmap(page);
 430                         err = memcpy_toiovecend(to, vaddr + frag->page_offset +
 431                                                 offset - start, to_offset, copy);
 432                         kunmap(page);
 433                         if (err)
 434                                 goto fault;
 435                         if (!(len -= copy))
 436                                 return 0;
 437                         offset += copy;
 438                         to_offset += copy;
 439                 }
 440                 start = end;
 441         }
 442
 443         skb_walk_frags(skb, frag_iter) {
 444                 int end;
 445
 446                 WARN_ON(start > offset + len);
 447
 448                 end = start + frag_iter->len;
 449                 if ((copy = end - offset) > 0) {
 450                         if (copy > len)
 451                                 copy = len;
 452                         if (skb_copy_datagram_const_iovec(frag_iter,
 453                                                           offset - start,
 454                                                           to, to_offset,
 455                                                           copy))
 456                                 goto fault;
 457                         if ((len -= copy) == 0)
 458                                 return 0;
 459                         offset += copy;
 460                         to_offset += copy;
 461                 }
 462                 start = end;
 463         }
 464         if (!len)
 465                 return 0;
 466
 467 fault:
 468         return -EFAULT;
 469 }
 470 EXPORT_SYMBOL(skb_copy_datagram_const_iovec);
 471
 472 /**
 473  *      skb_copy_datagram_from_iovec - Copy a datagram from an iovec.
 474  *      @skb: buffer to copy
 475  *      @offset: offset in the buffer to start copying to
 476  *      @from: io vector to copy to
 477  *      @from_offset: offset in the io vector to start copying from
 478  *      @len: amount of data to copy to buffer from iovec
 479  *
 480  *      Returns 0 or -EFAULT.
 481  *      Note: the iovec is not modified during the copy.
 482  */
 483 int skb_copy_datagram_from_iovec(struct sk_buff *skb, int offset,
 484                                  const struct iovec *from, int from_offset,
 485                                  int len)
 486 {
 487         int start = skb_headlen(skb);
 488         int i, copy = start - offset;
 489         struct sk_buff *frag_iter;
 490
 491         /* Copy header. */
 492         if (copy > 0) {
 493                 if (copy > len)
 494                         copy = len;
 495                 if (memcpy_fromiovecend(skb->data + offset, from, from_offset,
 496                                         copy))
 497                         goto fault;
 498                 if ((len -= copy) == 0)
 499                         return 0;
 500                 offset += copy;
 501                 from_offset += copy;
 502         }
 503
 504         /* Copy paged appendix. Hmm... why does this look so complicated? */
 505         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 506                 int end;
 507                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 508
 509                 WARN_ON(start > offset + len);
 510
 511                 end = start + skb_frag_size(frag);
 512                 if ((copy = end - offset) > 0) {
 513                         int err;
 514                         u8  *vaddr;
 515                         struct page *page = skb_frag_page(frag);
 516
 517                         if (copy > len)
 518                                 copy = len;
 519                         vaddr = kmap(page);
 520                         err = memcpy_fromiovecend(vaddr + frag->page_offset +
 521                                                   offset - start,
 522                                                   from, from_offset, copy);
 523                         kunmap(page);
 524                         if (err)
 525                                 goto fault;
 526
 527                         if (!(len -= copy))
 528                                 return 0;
 529                         offset += copy;
 530                         from_offset += copy;
 531                 }
 532                 start = end;
 533         }
 534
 535         skb_walk_frags(skb, frag_iter) {
 536                 int end;
 537
 538                 WARN_ON(start > offset + len);
 539
 540                 end = start + frag_iter->len;
 541                 if ((copy = end - offset) > 0) {
 542                         if (copy > len)
 543                                 copy = len;
 544                         if (skb_copy_datagram_from_iovec(frag_iter,
 545                                                          offset - start,
 546                                                          from,
 547                                                          from_offset,
 548                                                          copy))
 549                                 goto fault;
 550                         if ((len -= copy) == 0)
 551                                 return 0;
 552                         offset += copy;
 553                         from_offset += copy;
 554                 }
 555                 start = end;
 556         }
 557         if (!len)
 558                 return 0;
 559
 560 fault:
 561         return -EFAULT;
 562 }
 563 EXPORT_SYMBOL(skb_copy_datagram_from_iovec);
 564
 565 static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
 566                                       u8 __user *to, int len,
 567                                       __wsum *csump)
 568 {
 569         int start = skb_headlen(skb);
 570         int i, copy = start - offset;
 571         struct sk_buff *frag_iter;
 572         int pos = 0;
 573
 574         /* Copy header. */
 575         if (copy > 0) {
 576                 int err = 0;
 577                 if (copy > len)
 578                         copy = len;
 579                 *csump = csum_and_copy_to_user(skb->data + offset, to, copy,
 580                                                *csump, &err);
 581                 if (err)
 582                         goto fault;
 583                 if ((len -= copy) == 0)
 584                         return 0;
 585                 offset += copy;
 586                 to += copy;
 587                 pos = copy;
 588         }
 589
 590         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 591                 int end;
 592                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 593
 594                 WARN_ON(start > offset + len);
 595
 596                 end = start + skb_frag_size(frag);
 597                 if ((copy = end - offset) > 0) {
 598                         __wsum csum2;
 599                         int err = 0;
 600                         u8  *vaddr;
 601                         struct page *page = skb_frag_page(frag);
 602
 603                         if (copy > len)
 604                                 copy = len;
 605                         vaddr = kmap(page);
 606                         csum2 = csum_and_copy_to_user(vaddr +
 607                                                         frag->page_offset +
 608                                                         offset - start,
 609                                                       to, copy, 0, &err);
 610                         kunmap(page);
 611                         if (err)
 612                                 goto fault;
 613                         *csump = csum_block_add(*csump, csum2, pos);
 614                         if (!(len -= copy))
 615                                 return 0;
 616                         offset += copy;
 617                         to += copy;
 618                         pos += copy;
 619                 }
 620                 start = end;
 621         }
 622
 623         skb_walk_frags(skb, frag_iter) {
 624                 int end;
 625
 626                 WARN_ON(start > offset + len);
 627
 628                 end = start + frag_iter->len;
 629                 if ((copy = end - offset) > 0) {
 630                         __wsum csum2 = 0;
 631                         if (copy > len)
 632                                 copy = len;
 633                         if (skb_copy_and_csum_datagram(frag_iter,
 634                                                        offset - start,
 635                                                        to, copy,
 636                                                        &csum2))
 637                                 goto fault;
 638                         *csump = csum_block_add(*csump, csum2, pos);
 639                         if ((len -= copy) == 0)
 640                                 return 0;
 641                         offset += copy;
 642                         to += copy;
 643                         pos += copy;
 644                 }
 645                 start = end;
 646         }
 647         if (!len)
 648                 return 0;
 649
 650 fault:
 651         return -EFAULT;
 652 }
 653
 654 __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)
 655 {
 656         __sum16 sum;
 657
 658         sum = csum_fold(skb_checksum(skb, 0, len, skb->csum));
 659         if (likely(!sum)) {
 660                 if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
 661                         netdev_rx_csum_fault(skb->dev);
 662                 skb->ip_summed = CHECKSUM_UNNECESSARY;
 663         }
 664         return sum;
 665 }
 666 EXPORT_SYMBOL(__skb_checksum_complete_head);
 667
 668 __sum16 __skb_checksum_complete(struct sk_buff *skb)
 669 {
 670         return __skb_checksum_complete_head(skb, skb->len);
 671 }
 672 EXPORT_SYMBOL(__skb_checksum_complete);
 673
 674 /**
 675  *      skb_copy_and_csum_datagram_iovec - Copy and checkum skb to user iovec.
 676  *      @skb: skbuff
 677  *      @hlen: hardware length
 678  *      @iov: io vector
 679  *
 680  *      Caller _must_ check that skb will fit to this iovec.
 681  *
 682  *      Returns: 0       - success.
 683  *               -EINVAL - checksum failure.
 684  *               -EFAULT - fault during copy. Beware, in this case iovec
 685  *                         can be modified!
 686  */
 687 int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
 688                                      int hlen, struct iovec *iov)
 689 {
 690         __wsum csum;
 691         int chunk = skb->len - hlen;
 692
 693         if (!chunk)
 694                 return 0;
 695
 696         /* Skip filled elements.
 697          * Pretty silly, look at memcpy_toiovec, though 8)
 698          */
 699         while (!iov->iov_len)
 700                 iov++;
 701
 702         if (iov->iov_len < chunk) {
 703                 if (__skb_checksum_complete(skb))
 704                         goto csum_error;
 705                 if (skb_copy_datagram_iovec(skb, hlen, iov, chunk))
 706                         goto fault;
 707         } else {
 708                 csum = csum_partial(skb->data, hlen, skb->csum);
 709                 if (skb_copy_and_csum_datagram(skb, hlen, iov->iov_base,
 710                                                chunk, &csum))
 711                         goto fault;
 712                 if (csum_fold(csum))
 713                         goto csum_error;
 714                 if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
 715                         netdev_rx_csum_fault(skb->dev);
 716                 iov->iov_len -= chunk;
 717                 iov->iov_base += chunk;
 718         }
 719         return 0;
 720 csum_error:
 721         return -EINVAL;
 722 fault:
 723         return -EFAULT;
 724 }
 725 EXPORT_SYMBOL(skb_copy_and_csum_datagram_iovec);
 726
 727 /**
 728  *      datagram_poll - generic datagram poll
 729  *      @file: file struct
 730  *      @sock: socket
 731  *      @wait: poll table
 732  *
 733  *      Datagram poll: Again totally generic. This also handles
 734  *      sequenced packet sockets providing the socket receive queue
 735  *      is only ever holding data ready to receive.
 736  *
 737  *      Note: when you _don't_ use this routine for this protocol,
 738  *      and you use a different write policy from sock_writeable()
 739  *      then please supply your own write_space callback.
 740  */
 741 unsigned int datagram_poll(struct file *file, struct socket *sock,
 742                            poll_table *wait)
 743 {
 744         struct sock *sk = sock->sk;
 745         unsigned int mask;
 746
 747         sock_poll_wait(file, sk_sleep(sk), wait);
 748         mask = 0;
 749
 750         /* exceptional events? */
 751         if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
 752                 mask |= POLLERR;
 753         if (sk->sk_shutdown & RCV_SHUTDOWN)
 754                 mask |= POLLRDHUP | POLLIN | POLLRDNORM;
 755         if (sk->sk_shutdown == SHUTDOWN_MASK)
 756                 mask |= POLLHUP;
 757
 758         /* readable? */
 759         if (!skb_queue_empty(&sk->sk_receive_queue))
 760                 mask |= POLLIN | POLLRDNORM;
 761
 762         /* Connection-based need to check for termination and startup */
 763         if (connection_based(sk)) {
 764                 if (sk->sk_state == TCP_CLOSE)
 765                         mask |= POLLHUP;
 766                 /* connection hasn't started yet? */
 767                 if (sk->sk_state == TCP_SYN_SENT)
 768                         return mask;
 769         }
 770
 771         /* writable? */
 772         if (sock_writeable(sk))
 773                 mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
 774         else
 775                 set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
 776
 777         return mask;
 778 }
 779 EXPORT_SYMBOL(datagram_poll);