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 the last received packet to be different from skb
  82  */
  83 static int wait_for_more_packets(struct sock *sk, int *err, long *timeo_p,
  84                                  const struct sk_buff *skb)
  85 {
  86         int error;
  87         DEFINE_WAIT_FUNC(wait, receiver_wake_function);
  88
  89         prepare_to_wait_exclusive(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
  90
  91         /* Socket errors? */
  92         error = sock_error(sk);
  93         if (error)
  94                 goto out_err;
  95
  96         if (sk->sk_receive_queue.prev != skb)
  97                 goto out;
  98
  99         /* Socket shut down? */
 100         if (sk->sk_shutdown & RCV_SHUTDOWN)
 101                 goto out_noerr;
 102
 103         /* Sequenced packets can come disconnected.
 104          * If so we report the problem
 105          */
 106         error = -ENOTCONN;
 107         if (connection_based(sk) &&
 108             !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN))
 109                 goto out_err;
 110
 111         /* handle signals */
 112         if (signal_pending(current))
 113                 goto interrupted;
 114
 115         error = 0;
 116         *timeo_p = schedule_timeout(*timeo_p);
 117 out:
 118         finish_wait(sk_sleep(sk), &wait);
 119         return error;
 120 interrupted:
 121         error = sock_intr_errno(*timeo_p);
 122 out_err:
 123         *err = error;
 124         goto out;
 125 out_noerr:
 126         *err = 0;
 127         error = 1;
 128         goto out;
 129 }
 130
 131 /**
 132  *      __skb_recv_datagram - Receive a datagram skbuff
 133  *      @sk: socket
 134  *      @flags: MSG_ flags
 135  *      @peeked: returns non-zero if this packet has been seen before
 136  *      @off: an offset in bytes to peek skb from. Returns an offset
 137  *            within an skb where data actually starts
 138  *      @err: error code returned
 139  *
 140  *      Get a datagram skbuff, understands the peeking, nonblocking wakeups
 141  *      and possible races. This replaces identical code in packet, raw and
 142  *      udp, as well as the IPX AX.25 and Appletalk. It also finally fixes
 143  *      the long standing peek and read race for datagram sockets. If you
 144  *      alter this routine remember it must be re-entrant.
 145  *
 146  *      This function will lock the socket if a skb is returned, so the caller
 147  *      needs to unlock the socket in that case (usually by calling
 148  *      skb_free_datagram)
 149  *
 150  *      * It does not lock socket since today. This function is
 151  *      * free of race conditions. This measure should/can improve
 152  *      * significantly datagram socket latencies at high loads,
 153  *      * when data copying to user space takes lots of time.
 154  *      * (BTW I've just killed the last cli() in IP/IPv6/core/netlink/packet
 155  *      *  8) Great win.)
 156  *      *                                           --ANK (980729)
 157  *
 158  *      The order of the tests when we find no data waiting are specified
 159  *      quite explicitly by POSIX 1003.1g, don't change them without having
 160  *      the standard around please.
 161  */
 162 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
 163                                     int *peeked, int *off, int *err)
 164 {
 165         struct sk_buff *skb, *last;
 166         long timeo;
 167         /*
 168          * Caller is allowed not to check sk->sk_err before skb_recv_datagram()
 169          */
 170         int error = sock_error(sk);
 171
 172         if (error)
 173                 goto no_packet;
 174
 175         timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 176
 177         do {
 178                 /* Again only user level code calls this function, so nothing
 179                  * interrupt level will suddenly eat the receive_queue.
 180                  *
 181                  * Look at current nfs client by the way...
 182                  * However, this function was correct in any case. 8)
 183                  */
 184                 unsigned long cpu_flags;
 185                 struct sk_buff_head *queue = &sk->sk_receive_queue;
 186                 int _off = *off;
 187
 188                 last = (struct sk_buff *)queue;
 189                 spin_lock_irqsave(&queue->lock, cpu_flags);
 190                 skb_queue_walk(queue, skb) {
 191                         last = skb;
 192                         *peeked = skb->peeked;
 193                         if (flags & MSG_PEEK) {
 194                                 if (_off >= skb->len && (skb->len || _off ||
 195                                                          skb->peeked)) {
 196                                         _off -= skb->len;
 197                                         continue;
 198                                 }
 199                                 skb->peeked = 1;
 200                                 atomic_inc(&skb->users);
 201                         } else
 202                                 __skb_unlink(skb, queue);
 203
 204                         spin_unlock_irqrestore(&queue->lock, cpu_flags);
 205                         *off = _off;
 206                         return skb;
 207                 }
 208                 spin_unlock_irqrestore(&queue->lock, cpu_flags);
 209
 210                 /* User doesn't want to wait */
 211                 error = -EAGAIN;
 212                 if (!timeo)
 213                         goto no_packet;
 214
 215         } while (!wait_for_more_packets(sk, err, &timeo, last));
 216
 217         return NULL;
 218
 219 no_packet:
 220         *err = error;
 221         return NULL;
 222 }
 223 EXPORT_SYMBOL(__skb_recv_datagram);
 224
 225 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags,
 226                                   int noblock, int *err)
 227 {
 228         int peeked, off = 0;
 229
 230         return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
 231                                    &peeked, &off, err);
 232 }
 233 EXPORT_SYMBOL(skb_recv_datagram);
 234
 235 void skb_free_datagram(struct sock *sk, struct sk_buff *skb)
 236 {
 237         consume_skb(skb);
 238         sk_mem_reclaim_partial(sk);
 239 }
 240 EXPORT_SYMBOL(skb_free_datagram);
 241
 242 void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb)
 243 {
 244         bool slow;
 245
 246         if (likely(atomic_read(&skb->users) == 1))
 247                 smp_rmb();
 248         else if (likely(!atomic_dec_and_test(&skb->users)))
 249                 return;
 250
 251         slow = lock_sock_fast(sk);
 252         skb_orphan(skb);
 253         sk_mem_reclaim_partial(sk);
 254         unlock_sock_fast(sk, slow);
 255
 256         /* skb is now orphaned, can be freed outside of locked section */
 257         __kfree_skb(skb);
 258 }
 259 EXPORT_SYMBOL(skb_free_datagram_locked);
 260
 261 /**
 262  *      skb_kill_datagram - Free a datagram skbuff forcibly
 263  *      @sk: socket
 264  *      @skb: datagram skbuff
 265  *      @flags: MSG_ flags
 266  *
 267  *      This function frees a datagram skbuff that was received by
 268  *      skb_recv_datagram.  The flags argument must match the one
 269  *      used for skb_recv_datagram.
 270  *
 271  *      If the MSG_PEEK flag is set, and the packet is still on the
 272  *      receive queue of the socket, it will be taken off the queue
 273  *      before it is freed.
 274  *
 275  *      This function currently only disables BH when acquiring the
 276  *      sk_receive_queue lock.  Therefore it must not be used in a
 277  *      context where that lock is acquired in an IRQ context.
 278  *
 279  *      It returns 0 if the packet was removed by us.
 280  */
 281
 282 int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)
 283 {
 284         int err = 0;
 285
 286         if (flags & MSG_PEEK) {
 287                 err = -ENOENT;
 288                 spin_lock_bh(&sk->sk_receive_queue.lock);
 289                 if (skb == skb_peek(&sk->sk_receive_queue)) {
 290                         __skb_unlink(skb, &sk->sk_receive_queue);
 291                         atomic_dec(&skb->users);
 292                         err = 0;
 293                 }
 294                 spin_unlock_bh(&sk->sk_receive_queue.lock);
 295         }
 296
 297         kfree_skb(skb);
 298         atomic_inc(&sk->sk_drops);
 299         sk_mem_reclaim_partial(sk);
 300
 301         return err;
 302 }
 303 EXPORT_SYMBOL(skb_kill_datagram);
 304
 305 /**
 306  *      skb_copy_datagram_iovec - Copy a datagram to an iovec.
 307  *      @skb: buffer to copy
 308  *      @offset: offset in the buffer to start copying from
 309  *      @to: io vector to copy to
 310  *      @len: amount of data to copy from buffer to iovec
 311  *
 312  *      Note: the iovec is modified during the copy.
 313  */
 314 int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,
 315                             struct iovec *to, int len)
 316 {
 317         int start = skb_headlen(skb);
 318         int i, copy = start - offset;
 319         struct sk_buff *frag_iter;
 320
 321         trace_skb_copy_datagram_iovec(skb, len);
 322
 323         /* Copy header. */
 324         if (copy > 0) {
 325                 if (copy > len)
 326                         copy = len;
 327                 if (memcpy_toiovec(to, skb->data + offset, copy))
 328                         goto fault;
 329                 if ((len -= copy) == 0)
 330                         return 0;
 331                 offset += copy;
 332         }
 333
 334         /* Copy paged appendix. Hmm... why does this look so complicated? */
 335         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 336                 int end;
 337                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 338
 339                 WARN_ON(start > offset + len);
 340
 341                 end = start + skb_frag_size(frag);
 342                 if ((copy = end - offset) > 0) {
 343                         int err;
 344                         u8  *vaddr;
 345                         struct page *page = skb_frag_page(frag);
 346
 347                         if (copy > len)
 348                                 copy = len;
 349                         vaddr = kmap(page);
 350                         err = memcpy_toiovec(to, vaddr + frag->page_offset +
 351                                              offset - start, copy);
 352                         kunmap(page);
 353                         if (err)
 354                                 goto fault;
 355                         if (!(len -= copy))
 356                                 return 0;
 357                         offset += copy;
 358                 }
 359                 start = end;
 360         }
 361
 362         skb_walk_frags(skb, frag_iter) {
 363                 int end;
 364
 365                 WARN_ON(start > offset + len);
 366
 367                 end = start + frag_iter->len;
 368                 if ((copy = end - offset) > 0) {
 369                         if (copy > len)
 370                                 copy = len;
 371                         if (skb_copy_datagram_iovec(frag_iter,
 372                                                     offset - start,
 373                                                     to, copy))
 374                                 goto fault;
 375                         if ((len -= copy) == 0)
 376                                 return 0;
 377                         offset += copy;
 378                 }
 379                 start = end;
 380         }
 381         if (!len)
 382                 return 0;
 383
 384 fault:
 385         return -EFAULT;
 386 }
 387 EXPORT_SYMBOL(skb_copy_datagram_iovec);
 388
 389 /**
 390  *      skb_copy_datagram_const_iovec - Copy a datagram to an iovec.
 391  *      @skb: buffer to copy
 392  *      @offset: offset in the buffer to start copying from
 393  *      @to: io vector to copy to
 394  *      @to_offset: offset in the io vector to start copying to
 395  *      @len: amount of data to copy from buffer to iovec
 396  *
 397  *      Returns 0 or -EFAULT.
 398  *      Note: the iovec is not modified during the copy.
 399  */
 400 int skb_copy_datagram_const_iovec(const struct sk_buff *skb, int offset,
 401                                   const struct iovec *to, int to_offset,
 402                                   int len)
 403 {
 404         int start = skb_headlen(skb);
 405         int i, copy = start - offset;
 406         struct sk_buff *frag_iter;
 407
 408         /* Copy header. */
 409         if (copy > 0) {
 410                 if (copy > len)
 411                         copy = len;
 412                 if (memcpy_toiovecend(to, skb->data + offset, to_offset, copy))
 413                         goto fault;
 414                 if ((len -= copy) == 0)
 415                         return 0;
 416                 offset += copy;
 417                 to_offset += copy;
 418         }
 419
 420         /* Copy paged appendix. Hmm... why does this look so complicated? */
 421         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 422                 int end;
 423                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 424
 425                 WARN_ON(start > offset + len);
 426
 427                 end = start + skb_frag_size(frag);
 428                 if ((copy = end - offset) > 0) {
 429                         int err;
 430                         u8  *vaddr;
 431                         struct page *page = skb_frag_page(frag);
 432
 433                         if (copy > len)
 434                                 copy = len;
 435                         vaddr = kmap(page);
 436                         err = memcpy_toiovecend(to, vaddr + frag->page_offset +
 437                                                 offset - start, to_offset, copy);
 438                         kunmap(page);
 439                         if (err)
 440                                 goto fault;
 441                         if (!(len -= copy))
 442                                 return 0;
 443                         offset += copy;
 444                         to_offset += copy;
 445                 }
 446                 start = end;
 447         }
 448
 449         skb_walk_frags(skb, frag_iter) {
 450                 int end;
 451
 452                 WARN_ON(start > offset + len);
 453
 454                 end = start + frag_iter->len;
 455                 if ((copy = end - offset) > 0) {
 456                         if (copy > len)
 457                                 copy = len;
 458                         if (skb_copy_datagram_const_iovec(frag_iter,
 459                                                           offset - start,
 460                                                           to, to_offset,
 461                                                           copy))
 462                                 goto fault;
 463                         if ((len -= copy) == 0)
 464                                 return 0;
 465                         offset += copy;
 466                         to_offset += copy;
 467                 }
 468                 start = end;
 469         }
 470         if (!len)
 471                 return 0;
 472
 473 fault:
 474         return -EFAULT;
 475 }
 476 EXPORT_SYMBOL(skb_copy_datagram_const_iovec);
 477
 478 /**
 479  *      skb_copy_datagram_from_iovec - Copy a datagram from an iovec.
 480  *      @skb: buffer to copy
 481  *      @offset: offset in the buffer to start copying to
 482  *      @from: io vector to copy to
 483  *      @from_offset: offset in the io vector to start copying from
 484  *      @len: amount of data to copy to buffer from iovec
 485  *
 486  *      Returns 0 or -EFAULT.
 487  *      Note: the iovec is not modified during the copy.
 488  */
 489 int skb_copy_datagram_from_iovec(struct sk_buff *skb, int offset,
 490                                  const struct iovec *from, int from_offset,
 491                                  int len)
 492 {
 493         int start = skb_headlen(skb);
 494         int i, copy = start - offset;
 495         struct sk_buff *frag_iter;
 496
 497         /* Copy header. */
 498         if (copy > 0) {
 499                 if (copy > len)
 500                         copy = len;
 501                 if (memcpy_fromiovecend(skb->data + offset, from, from_offset,
 502                                         copy))
 503                         goto fault;
 504                 if ((len -= copy) == 0)
 505                         return 0;
 506                 offset += copy;
 507                 from_offset += copy;
 508         }
 509
 510         /* Copy paged appendix. Hmm... why does this look so complicated? */
 511         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 512                 int end;
 513                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 514
 515                 WARN_ON(start > offset + len);
 516
 517                 end = start + skb_frag_size(frag);
 518                 if ((copy = end - offset) > 0) {
 519                         int err;
 520                         u8  *vaddr;
 521                         struct page *page = skb_frag_page(frag);
 522
 523                         if (copy > len)
 524                                 copy = len;
 525                         vaddr = kmap(page);
 526                         err = memcpy_fromiovecend(vaddr + frag->page_offset +
 527                                                   offset - start,
 528                                                   from, from_offset, copy);
 529                         kunmap(page);
 530                         if (err)
 531                                 goto fault;
 532
 533                         if (!(len -= copy))
 534                                 return 0;
 535                         offset += copy;
 536                         from_offset += copy;
 537                 }
 538                 start = end;
 539         }
 540
 541         skb_walk_frags(skb, frag_iter) {
 542                 int end;
 543
 544                 WARN_ON(start > offset + len);
 545
 546                 end = start + frag_iter->len;
 547                 if ((copy = end - offset) > 0) {
 548                         if (copy > len)
 549                                 copy = len;
 550                         if (skb_copy_datagram_from_iovec(frag_iter,
 551                                                          offset - start,
 552                                                          from,
 553                                                          from_offset,
 554                                                          copy))
 555                                 goto fault;
 556                         if ((len -= copy) == 0)
 557                                 return 0;
 558                         offset += copy;
 559                         from_offset += copy;
 560                 }
 561                 start = end;
 562         }
 563         if (!len)
 564                 return 0;
 565
 566 fault:
 567         return -EFAULT;
 568 }
 569 EXPORT_SYMBOL(skb_copy_datagram_from_iovec);
 570
 571 static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
 572                                       u8 __user *to, int len,
 573                                       __wsum *csump)
 574 {
 575         int start = skb_headlen(skb);
 576         int i, copy = start - offset;
 577         struct sk_buff *frag_iter;
 578         int pos = 0;
 579
 580         /* Copy header. */
 581         if (copy > 0) {
 582                 int err = 0;
 583                 if (copy > len)
 584                         copy = len;
 585                 *csump = csum_and_copy_to_user(skb->data + offset, to, copy,
 586                                                *csump, &err);
 587                 if (err)
 588                         goto fault;
 589                 if ((len -= copy) == 0)
 590                         return 0;
 591                 offset += copy;
 592                 to += copy;
 593                 pos = copy;
 594         }
 595
 596         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 597                 int end;
 598                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 599
 600                 WARN_ON(start > offset + len);
 601
 602                 end = start + skb_frag_size(frag);
 603                 if ((copy = end - offset) > 0) {
 604                         __wsum csum2;
 605                         int err = 0;
 606                         u8  *vaddr;
 607                         struct page *page = skb_frag_page(frag);
 608
 609                         if (copy > len)
 610                                 copy = len;
 611                         vaddr = kmap(page);
 612                         csum2 = csum_and_copy_to_user(vaddr +
 613                                                         frag->page_offset +
 614                                                         offset - start,
 615                                                       to, copy, 0, &err);
 616                         kunmap(page);
 617                         if (err)
 618                                 goto fault;
 619                         *csump = csum_block_add(*csump, csum2, pos);
 620                         if (!(len -= copy))
 621                                 return 0;
 622                         offset += copy;
 623                         to += copy;
 624                         pos += copy;
 625                 }
 626                 start = end;
 627         }
 628
 629         skb_walk_frags(skb, frag_iter) {
 630                 int end;
 631
 632                 WARN_ON(start > offset + len);
 633
 634                 end = start + frag_iter->len;
 635                 if ((copy = end - offset) > 0) {
 636                         __wsum csum2 = 0;
 637                         if (copy > len)
 638                                 copy = len;
 639                         if (skb_copy_and_csum_datagram(frag_iter,
 640                                                        offset - start,
 641                                                        to, copy,
 642                                                        &csum2))
 643                                 goto fault;
 644                         *csump = csum_block_add(*csump, csum2, pos);
 645                         if ((len -= copy) == 0)
 646                                 return 0;
 647                         offset += copy;
 648                         to += copy;
 649                         pos += copy;
 650                 }
 651                 start = end;
 652         }
 653         if (!len)
 654                 return 0;
 655
 656 fault:
 657         return -EFAULT;
 658 }
 659
 660 __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)
 661 {
 662         __sum16 sum;
 663
 664         sum = csum_fold(skb_checksum(skb, 0, len, skb->csum));
 665         if (likely(!sum)) {
 666                 if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
 667                         netdev_rx_csum_fault(skb->dev);
 668                 skb->ip_summed = CHECKSUM_UNNECESSARY;
 669         }
 670         return sum;
 671 }
 672 EXPORT_SYMBOL(__skb_checksum_complete_head);
 673
 674 __sum16 __skb_checksum_complete(struct sk_buff *skb)
 675 {
 676         return __skb_checksum_complete_head(skb, skb->len);
 677 }
 678 EXPORT_SYMBOL(__skb_checksum_complete);
 679
 680 /**
 681  *      skb_copy_and_csum_datagram_iovec - Copy and checkum skb to user iovec.
 682  *      @skb: skbuff
 683  *      @hlen: hardware length
 684  *      @iov: io vector
 685  *
 686  *      Caller _must_ check that skb will fit to this iovec.
 687  *
 688  *      Returns: 0       - success.
 689  *               -EINVAL - checksum failure.
 690  *               -EFAULT - fault during copy. Beware, in this case iovec
 691  *                         can be modified!
 692  */
 693 int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
 694                                      int hlen, struct iovec *iov)
 695 {
 696         __wsum csum;
 697         int chunk = skb->len - hlen;
 698
 699         if (!chunk)
 700                 return 0;
 701
 702         /* Skip filled elements.
 703          * Pretty silly, look at memcpy_toiovec, though 8)
 704          */
 705         while (!iov->iov_len)
 706                 iov++;
 707
 708         if (iov->iov_len < chunk) {
 709                 if (__skb_checksum_complete(skb))
 710                         goto csum_error;
 711                 if (skb_copy_datagram_iovec(skb, hlen, iov, chunk))
 712                         goto fault;
 713         } else {
 714                 csum = csum_partial(skb->data, hlen, skb->csum);
 715                 if (skb_copy_and_csum_datagram(skb, hlen, iov->iov_base,
 716                                                chunk, &csum))
 717                         goto fault;
 718                 if (csum_fold(csum))
 719                         goto csum_error;
 720                 if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
 721                         netdev_rx_csum_fault(skb->dev);
 722                 iov->iov_len -= chunk;
 723                 iov->iov_base += chunk;
 724         }
 725         return 0;
 726 csum_error:
 727         return -EINVAL;
 728 fault:
 729         return -EFAULT;
 730 }
 731 EXPORT_SYMBOL(skb_copy_and_csum_datagram_iovec);
 732
 733 /**
 734  *      datagram_poll - generic datagram poll
 735  *      @file: file struct
 736  *      @sock: socket
 737  *      @wait: poll table
 738  *
 739  *      Datagram poll: Again totally generic. This also handles
 740  *      sequenced packet sockets providing the socket receive queue
 741  *      is only ever holding data ready to receive.
 742  *
 743  *      Note: when you _don't_ use this routine for this protocol,
 744  *      and you use a different write policy from sock_writeable()
 745  *      then please supply your own write_space callback.
 746  */
 747 unsigned int datagram_poll(struct file *file, struct socket *sock,
 748                            poll_table *wait)
 749 {
 750         struct sock *sk = sock->sk;
 751         unsigned int mask;
 752
 753         sock_poll_wait(file, sk_sleep(sk), wait);
 754         mask = 0;
 755
 756         /* exceptional events? */
 757         if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
 758                 mask |= POLLERR |
 759                         (sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0);
 760
 761         if (sk->sk_shutdown & RCV_SHUTDOWN)
 762                 mask |= POLLRDHUP | POLLIN | POLLRDNORM;
 763         if (sk->sk_shutdown == SHUTDOWN_MASK)
 764                 mask |= POLLHUP;
 765
 766         /* readable? */
 767         if (!skb_queue_empty(&sk->sk_receive_queue))
 768                 mask |= POLLIN | POLLRDNORM;
 769
 770         /* Connection-based need to check for termination and startup */
 771         if (connection_based(sk)) {
 772                 if (sk->sk_state == TCP_CLOSE)
 773                         mask |= POLLHUP;
 774                 /* connection hasn't started yet? */
 775                 if (sk->sk_state == TCP_SYN_SENT)
 776                         return mask;
 777         }
 778
 779         /* writable? */
 780         if (sock_writeable(sk))
 781                 mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
 782         else
 783                 set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
 784
 785         return mask;
 786 }
 787 EXPORT_SYMBOL(datagram_poll);