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TOMOYO Linux Cross Reference
Linux/net/core/datagram.c

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  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 #include <linux/pagemap.h>
 52 
 53 #include <net/protocol.h>
 54 #include <linux/skbuff.h>
 55 
 56 #include <net/checksum.h>
 57 #include <net/sock.h>
 58 #include <net/tcp_states.h>
 59 #include <trace/events/skb.h>
 60 #include <net/busy_poll.h>
 61 
 62 /*
 63  *      Is a socket 'connection oriented' ?
 64  */
 65 static inline int connection_based(struct sock *sk)
 66 {
 67         return sk->sk_type == SOCK_SEQPACKET || sk->sk_type == SOCK_STREAM;
 68 }
 69 
 70 static int receiver_wake_function(wait_queue_t *wait, unsigned int mode, int sync,
 71                                   void *key)
 72 {
 73         unsigned long bits = (unsigned long)key;
 74 
 75         /*
 76          * Avoid a wakeup if event not interesting for us
 77          */
 78         if (bits && !(bits & (POLLIN | POLLERR)))
 79                 return 0;
 80         return autoremove_wake_function(wait, mode, sync, key);
 81 }
 82 /*
 83  * Wait for the last received packet to be different from skb
 84  */
 85 static int wait_for_more_packets(struct sock *sk, int *err, long *timeo_p,
 86                                  const struct sk_buff *skb)
 87 {
 88         int error;
 89         DEFINE_WAIT_FUNC(wait, receiver_wake_function);
 90 
 91         prepare_to_wait_exclusive(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 92 
 93         /* Socket errors? */
 94         error = sock_error(sk);
 95         if (error)
 96                 goto out_err;
 97 
 98         if (sk->sk_receive_queue.prev != skb)
 99                 goto out;
100 
101         /* Socket shut down? */
102         if (sk->sk_shutdown & RCV_SHUTDOWN)
103                 goto out_noerr;
104 
105         /* Sequenced packets can come disconnected.
106          * If so we report the problem
107          */
108         error = -ENOTCONN;
109         if (connection_based(sk) &&
110             !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN))
111                 goto out_err;
112 
113         /* handle signals */
114         if (signal_pending(current))
115                 goto interrupted;
116 
117         error = 0;
118         *timeo_p = schedule_timeout(*timeo_p);
119 out:
120         finish_wait(sk_sleep(sk), &wait);
121         return error;
122 interrupted:
123         error = sock_intr_errno(*timeo_p);
124 out_err:
125         *err = error;
126         goto out;
127 out_noerr:
128         *err = 0;
129         error = 1;
130         goto out;
131 }
132 
133 static struct sk_buff *skb_set_peeked(struct sk_buff *skb)
134 {
135         struct sk_buff *nskb;
136 
137         if (skb->peeked)
138                 return skb;
139 
140         /* We have to unshare an skb before modifying it. */
141         if (!skb_shared(skb))
142                 goto done;
143 
144         nskb = skb_clone(skb, GFP_ATOMIC);
145         if (!nskb)
146                 return ERR_PTR(-ENOMEM);
147 
148         skb->prev->next = nskb;
149         skb->next->prev = nskb;
150         nskb->prev = skb->prev;
151         nskb->next = skb->next;
152 
153         consume_skb(skb);
154         skb = nskb;
155 
156 done:
157         skb->peeked = 1;
158 
159         return skb;
160 }
161 
162 /**
163  *      __skb_recv_datagram - Receive a datagram skbuff
164  *      @sk: socket
165  *      @flags: MSG_ flags
166  *      @peeked: returns non-zero if this packet has been seen before
167  *      @off: an offset in bytes to peek skb from. Returns an offset
168  *            within an skb where data actually starts
169  *      @err: error code returned
170  *
171  *      Get a datagram skbuff, understands the peeking, nonblocking wakeups
172  *      and possible races. This replaces identical code in packet, raw and
173  *      udp, as well as the IPX AX.25 and Appletalk. It also finally fixes
174  *      the long standing peek and read race for datagram sockets. If you
175  *      alter this routine remember it must be re-entrant.
176  *
177  *      This function will lock the socket if a skb is returned, so the caller
178  *      needs to unlock the socket in that case (usually by calling
179  *      skb_free_datagram)
180  *
181  *      * It does not lock socket since today. This function is
182  *      * free of race conditions. This measure should/can improve
183  *      * significantly datagram socket latencies at high loads,
184  *      * when data copying to user space takes lots of time.
185  *      * (BTW I've just killed the last cli() in IP/IPv6/core/netlink/packet
186  *      *  8) Great win.)
187  *      *                                           --ANK (980729)
188  *
189  *      The order of the tests when we find no data waiting are specified
190  *      quite explicitly by POSIX 1003.1g, don't change them without having
191  *      the standard around please.
192  */
193 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
194                                     int *peeked, int *off, int *err)
195 {
196         struct sk_buff_head *queue = &sk->sk_receive_queue;
197         struct sk_buff *skb, *last;
198         unsigned long cpu_flags;
199         long timeo;
200         /*
201          * Caller is allowed not to check sk->sk_err before skb_recv_datagram()
202          */
203         int error = sock_error(sk);
204 
205         if (error)
206                 goto no_packet;
207 
208         timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
209 
210         do {
211                 /* Again only user level code calls this function, so nothing
212                  * interrupt level will suddenly eat the receive_queue.
213                  *
214                  * Look at current nfs client by the way...
215                  * However, this function was correct in any case. 8)
216                  */
217                 int _off = *off;
218 
219                 last = (struct sk_buff *)queue;
220                 spin_lock_irqsave(&queue->lock, cpu_flags);
221                 skb_queue_walk(queue, skb) {
222                         last = skb;
223                         *peeked = skb->peeked;
224                         if (flags & MSG_PEEK) {
225                                 if (_off >= skb->len && (skb->len || _off ||
226                                                          skb->peeked)) {
227                                         _off -= skb->len;
228                                         continue;
229                                 }
230 
231                                 skb = skb_set_peeked(skb);
232                                 error = PTR_ERR(skb);
233                                 if (IS_ERR(skb))
234                                         goto unlock_err;
235 
236                                 atomic_inc(&skb->users);
237                         } else
238                                 __skb_unlink(skb, queue);
239 
240                         spin_unlock_irqrestore(&queue->lock, cpu_flags);
241                         *off = _off;
242                         return skb;
243                 }
244                 spin_unlock_irqrestore(&queue->lock, cpu_flags);
245 
246                 if (sk_can_busy_loop(sk) &&
247                     sk_busy_loop(sk, flags & MSG_DONTWAIT))
248                         continue;
249 
250                 /* User doesn't want to wait */
251                 error = -EAGAIN;
252                 if (!timeo)
253                         goto no_packet;
254 
255         } while (!wait_for_more_packets(sk, err, &timeo, last));
256 
257         return NULL;
258 
259 unlock_err:
260         spin_unlock_irqrestore(&queue->lock, cpu_flags);
261 no_packet:
262         *err = error;
263         return NULL;
264 }
265 EXPORT_SYMBOL(__skb_recv_datagram);
266 
267 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags,
268                                   int noblock, int *err)
269 {
270         int peeked, off = 0;
271 
272         return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
273                                    &peeked, &off, err);
274 }
275 EXPORT_SYMBOL(skb_recv_datagram);
276 
277 void skb_free_datagram(struct sock *sk, struct sk_buff *skb)
278 {
279         consume_skb(skb);
280         sk_mem_reclaim_partial(sk);
281 }
282 EXPORT_SYMBOL(skb_free_datagram);
283 
284 void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb)
285 {
286         bool slow;
287 
288         if (likely(atomic_read(&skb->users) == 1))
289                 smp_rmb();
290         else if (likely(!atomic_dec_and_test(&skb->users)))
291                 return;
292 
293         slow = lock_sock_fast(sk);
294         skb_orphan(skb);
295         sk_mem_reclaim_partial(sk);
296         unlock_sock_fast(sk, slow);
297 
298         /* skb is now orphaned, can be freed outside of locked section */
299         __kfree_skb(skb);
300 }
301 EXPORT_SYMBOL(skb_free_datagram_locked);
302 
303 /**
304  *      skb_kill_datagram - Free a datagram skbuff forcibly
305  *      @sk: socket
306  *      @skb: datagram skbuff
307  *      @flags: MSG_ flags
308  *
309  *      This function frees a datagram skbuff that was received by
310  *      skb_recv_datagram.  The flags argument must match the one
311  *      used for skb_recv_datagram.
312  *
313  *      If the MSG_PEEK flag is set, and the packet is still on the
314  *      receive queue of the socket, it will be taken off the queue
315  *      before it is freed.
316  *
317  *      This function currently only disables BH when acquiring the
318  *      sk_receive_queue lock.  Therefore it must not be used in a
319  *      context where that lock is acquired in an IRQ context.
320  *
321  *      It returns 0 if the packet was removed by us.
322  */
323 
324 int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)
325 {
326         int err = 0;
327 
328         if (flags & MSG_PEEK) {
329                 err = -ENOENT;
330                 spin_lock_bh(&sk->sk_receive_queue.lock);
331                 if (skb == skb_peek(&sk->sk_receive_queue)) {
332                         __skb_unlink(skb, &sk->sk_receive_queue);
333                         atomic_dec(&skb->users);
334                         err = 0;
335                 }
336                 spin_unlock_bh(&sk->sk_receive_queue.lock);
337         }
338 
339         kfree_skb(skb);
340         atomic_inc(&sk->sk_drops);
341         sk_mem_reclaim_partial(sk);
342 
343         return err;
344 }
345 EXPORT_SYMBOL(skb_kill_datagram);
346 
347 /**
348  *      skb_copy_datagram_iovec - Copy a datagram to an iovec.
349  *      @skb: buffer to copy
350  *      @offset: offset in the buffer to start copying from
351  *      @to: io vector to copy to
352  *      @len: amount of data to copy from buffer to iovec
353  *
354  *      Note: the iovec is modified during the copy.
355  */
356 int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,
357                             struct iovec *to, int len)
358 {
359         int start = skb_headlen(skb);
360         int i, copy = start - offset;
361         struct sk_buff *frag_iter;
362 
363         trace_skb_copy_datagram_iovec(skb, len);
364 
365         /* Copy header. */
366         if (copy > 0) {
367                 if (copy > len)
368                         copy = len;
369                 if (memcpy_toiovec(to, skb->data + offset, copy))
370                         goto fault;
371                 if ((len -= copy) == 0)
372                         return 0;
373                 offset += copy;
374         }
375 
376         /* Copy paged appendix. Hmm... why does this look so complicated? */
377         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
378                 int end;
379                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
380 
381                 WARN_ON(start > offset + len);
382 
383                 end = start + skb_frag_size(frag);
384                 if ((copy = end - offset) > 0) {
385                         int err;
386                         u8  *vaddr;
387                         struct page *page = skb_frag_page(frag);
388 
389                         if (copy > len)
390                                 copy = len;
391                         vaddr = kmap(page);
392                         err = memcpy_toiovec(to, vaddr + frag->page_offset +
393                                              offset - start, copy);
394                         kunmap(page);
395                         if (err)
396                                 goto fault;
397                         if (!(len -= copy))
398                                 return 0;
399                         offset += copy;
400                 }
401                 start = end;
402         }
403 
404         skb_walk_frags(skb, frag_iter) {
405                 int end;
406 
407                 WARN_ON(start > offset + len);
408 
409                 end = start + frag_iter->len;
410                 if ((copy = end - offset) > 0) {
411                         if (copy > len)
412                                 copy = len;
413                         if (skb_copy_datagram_iovec(frag_iter,
414                                                     offset - start,
415                                                     to, copy))
416                                 goto fault;
417                         if ((len -= copy) == 0)
418                                 return 0;
419                         offset += copy;
420                 }
421                 start = end;
422         }
423         if (!len)
424                 return 0;
425 
426 fault:
427         return -EFAULT;
428 }
429 EXPORT_SYMBOL(skb_copy_datagram_iovec);
430 
431 /**
432  *      skb_copy_datagram_const_iovec - Copy a datagram to an iovec.
433  *      @skb: buffer to copy
434  *      @offset: offset in the buffer to start copying from
435  *      @to: io vector to copy to
436  *      @to_offset: offset in the io vector to start copying to
437  *      @len: amount of data to copy from buffer to iovec
438  *
439  *      Returns 0 or -EFAULT.
440  *      Note: the iovec is not modified during the copy.
441  */
442 int skb_copy_datagram_const_iovec(const struct sk_buff *skb, int offset,
443                                   const struct iovec *to, int to_offset,
444                                   int len)
445 {
446         int start = skb_headlen(skb);
447         int i, copy = start - offset;
448         struct sk_buff *frag_iter;
449 
450         /* Copy header. */
451         if (copy > 0) {
452                 if (copy > len)
453                         copy = len;
454                 if (memcpy_toiovecend(to, skb->data + offset, to_offset, copy))
455                         goto fault;
456                 if ((len -= copy) == 0)
457                         return 0;
458                 offset += copy;
459                 to_offset += copy;
460         }
461 
462         /* Copy paged appendix. Hmm... why does this look so complicated? */
463         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
464                 int end;
465                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
466 
467                 WARN_ON(start > offset + len);
468 
469                 end = start + skb_frag_size(frag);
470                 if ((copy = end - offset) > 0) {
471                         int err;
472                         u8  *vaddr;
473                         struct page *page = skb_frag_page(frag);
474 
475                         if (copy > len)
476                                 copy = len;
477                         vaddr = kmap(page);
478                         err = memcpy_toiovecend(to, vaddr + frag->page_offset +
479                                                 offset - start, to_offset, copy);
480                         kunmap(page);
481                         if (err)
482                                 goto fault;
483                         if (!(len -= copy))
484                                 return 0;
485                         offset += copy;
486                         to_offset += copy;
487                 }
488                 start = end;
489         }
490 
491         skb_walk_frags(skb, frag_iter) {
492                 int end;
493 
494                 WARN_ON(start > offset + len);
495 
496                 end = start + frag_iter->len;
497                 if ((copy = end - offset) > 0) {
498                         if (copy > len)
499                                 copy = len;
500                         if (skb_copy_datagram_const_iovec(frag_iter,
501                                                           offset - start,
502                                                           to, to_offset,
503                                                           copy))
504                                 goto fault;
505                         if ((len -= copy) == 0)
506                                 return 0;
507                         offset += copy;
508                         to_offset += copy;
509                 }
510                 start = end;
511         }
512         if (!len)
513                 return 0;
514 
515 fault:
516         return -EFAULT;
517 }
518 EXPORT_SYMBOL(skb_copy_datagram_const_iovec);
519 
520 /**
521  *      skb_copy_datagram_from_iovec - Copy a datagram from an iovec.
522  *      @skb: buffer to copy
523  *      @offset: offset in the buffer to start copying to
524  *      @from: io vector to copy to
525  *      @from_offset: offset in the io vector to start copying from
526  *      @len: amount of data to copy to buffer from iovec
527  *
528  *      Returns 0 or -EFAULT.
529  *      Note: the iovec is not modified during the copy.
530  */
531 int skb_copy_datagram_from_iovec(struct sk_buff *skb, int offset,
532                                  const struct iovec *from, int from_offset,
533                                  int len)
534 {
535         int start = skb_headlen(skb);
536         int i, copy = start - offset;
537         struct sk_buff *frag_iter;
538 
539         /* Copy header. */
540         if (copy > 0) {
541                 if (copy > len)
542                         copy = len;
543                 if (memcpy_fromiovecend(skb->data + offset, from, from_offset,
544                                         copy))
545                         goto fault;
546                 if ((len -= copy) == 0)
547                         return 0;
548                 offset += copy;
549                 from_offset += copy;
550         }
551 
552         /* Copy paged appendix. Hmm... why does this look so complicated? */
553         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
554                 int end;
555                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
556 
557                 WARN_ON(start > offset + len);
558 
559                 end = start + skb_frag_size(frag);
560                 if ((copy = end - offset) > 0) {
561                         int err;
562                         u8  *vaddr;
563                         struct page *page = skb_frag_page(frag);
564 
565                         if (copy > len)
566                                 copy = len;
567                         vaddr = kmap(page);
568                         err = memcpy_fromiovecend(vaddr + frag->page_offset +
569                                                   offset - start,
570                                                   from, from_offset, copy);
571                         kunmap(page);
572                         if (err)
573                                 goto fault;
574 
575                         if (!(len -= copy))
576                                 return 0;
577                         offset += copy;
578                         from_offset += copy;
579                 }
580                 start = end;
581         }
582 
583         skb_walk_frags(skb, frag_iter) {
584                 int end;
585 
586                 WARN_ON(start > offset + len);
587 
588                 end = start + frag_iter->len;
589                 if ((copy = end - offset) > 0) {
590                         if (copy > len)
591                                 copy = len;
592                         if (skb_copy_datagram_from_iovec(frag_iter,
593                                                          offset - start,
594                                                          from,
595                                                          from_offset,
596                                                          copy))
597                                 goto fault;
598                         if ((len -= copy) == 0)
599                                 return 0;
600                         offset += copy;
601                         from_offset += copy;
602                 }
603                 start = end;
604         }
605         if (!len)
606                 return 0;
607 
608 fault:
609         return -EFAULT;
610 }
611 EXPORT_SYMBOL(skb_copy_datagram_from_iovec);
612 
613 /**
614  *      zerocopy_sg_from_iovec - Build a zerocopy datagram from an iovec
615  *      @skb: buffer to copy
616  *      @from: io vector to copy to
617  *      @offset: offset in the io vector to start copying from
618  *      @count: amount of vectors to copy to buffer from
619  *
620  *      The function will first copy up to headlen, and then pin the userspace
621  *      pages and build frags through them.
622  *
623  *      Returns 0, -EFAULT or -EMSGSIZE.
624  *      Note: the iovec is not modified during the copy
625  */
626 int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
627                                   int offset, size_t count)
628 {
629         int len = iov_length(from, count) - offset;
630         int copy = min_t(int, skb_headlen(skb), len);
631         int size;
632         int i = 0;
633 
634         /* copy up to skb headlen */
635         if (skb_copy_datagram_from_iovec(skb, 0, from, offset, copy))
636                 return -EFAULT;
637 
638         if (len == copy)
639                 return 0;
640 
641         offset += copy;
642         while (count--) {
643                 struct page *page[MAX_SKB_FRAGS];
644                 int num_pages;
645                 unsigned long base;
646                 unsigned long truesize;
647 
648                 /* Skip over from offset and copied */
649                 if (offset >= from->iov_len) {
650                         offset -= from->iov_len;
651                         ++from;
652                         continue;
653                 }
654                 len = from->iov_len - offset;
655                 base = (unsigned long)from->iov_base + offset;
656                 size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT;
657                 if (i + size > MAX_SKB_FRAGS)
658                         return -EMSGSIZE;
659                 num_pages = get_user_pages_fast(base, size, 0, &page[i]);
660                 if (num_pages != size) {
661                         release_pages(&page[i], num_pages, 0);
662                         return -EFAULT;
663                 }
664                 truesize = size * PAGE_SIZE;
665                 skb->data_len += len;
666                 skb->len += len;
667                 skb->truesize += truesize;
668                 atomic_add(truesize, &skb->sk->sk_wmem_alloc);
669                 while (len) {
670                         int off = base & ~PAGE_MASK;
671                         int size = min_t(int, len, PAGE_SIZE - off);
672                         skb_fill_page_desc(skb, i, page[i], off, size);
673                         base += size;
674                         len -= size;
675                         i++;
676                 }
677                 offset = 0;
678                 ++from;
679         }
680         return 0;
681 }
682 EXPORT_SYMBOL(zerocopy_sg_from_iovec);
683 
684 static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
685                                       u8 __user *to, int len,
686                                       __wsum *csump)
687 {
688         int start = skb_headlen(skb);
689         int i, copy = start - offset;
690         struct sk_buff *frag_iter;
691         int pos = 0;
692 
693         /* Copy header. */
694         if (copy > 0) {
695                 int err = 0;
696                 if (copy > len)
697                         copy = len;
698                 *csump = csum_and_copy_to_user(skb->data + offset, to, copy,
699                                                *csump, &err);
700                 if (err)
701                         goto fault;
702                 if ((len -= copy) == 0)
703                         return 0;
704                 offset += copy;
705                 to += copy;
706                 pos = copy;
707         }
708 
709         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
710                 int end;
711                 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
712 
713                 WARN_ON(start > offset + len);
714 
715                 end = start + skb_frag_size(frag);
716                 if ((copy = end - offset) > 0) {
717                         __wsum csum2;
718                         int err = 0;
719                         u8  *vaddr;
720                         struct page *page = skb_frag_page(frag);
721 
722                         if (copy > len)
723                                 copy = len;
724                         vaddr = kmap(page);
725                         csum2 = csum_and_copy_to_user(vaddr +
726                                                         frag->page_offset +
727                                                         offset - start,
728                                                       to, copy, 0, &err);
729                         kunmap(page);
730                         if (err)
731                                 goto fault;
732                         *csump = csum_block_add(*csump, csum2, pos);
733                         if (!(len -= copy))
734                                 return 0;
735                         offset += copy;
736                         to += copy;
737                         pos += copy;
738                 }
739                 start = end;
740         }
741 
742         skb_walk_frags(skb, frag_iter) {
743                 int end;
744 
745                 WARN_ON(start > offset + len);
746 
747                 end = start + frag_iter->len;
748                 if ((copy = end - offset) > 0) {
749                         __wsum csum2 = 0;
750                         if (copy > len)
751                                 copy = len;
752                         if (skb_copy_and_csum_datagram(frag_iter,
753                                                        offset - start,
754                                                        to, copy,
755                                                        &csum2))
756                                 goto fault;
757                         *csump = csum_block_add(*csump, csum2, pos);
758                         if ((len -= copy) == 0)
759                                 return 0;
760                         offset += copy;
761                         to += copy;
762                         pos += copy;
763                 }
764                 start = end;
765         }
766         if (!len)
767                 return 0;
768 
769 fault:
770         return -EFAULT;
771 }
772 
773 __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)
774 {
775         __sum16 sum;
776 
777         sum = csum_fold(skb_checksum(skb, 0, len, skb->csum));
778         if (likely(!sum)) {
779                 if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
780                         netdev_rx_csum_fault(skb->dev);
781                 if (!skb_shared(skb))
782                         skb->ip_summed = CHECKSUM_UNNECESSARY;
783         }
784         return sum;
785 }
786 EXPORT_SYMBOL(__skb_checksum_complete_head);
787 
788 __sum16 __skb_checksum_complete(struct sk_buff *skb)
789 {
790         return __skb_checksum_complete_head(skb, skb->len);
791 }
792 EXPORT_SYMBOL(__skb_checksum_complete);
793 
794 /**
795  *      skb_copy_and_csum_datagram_iovec - Copy and checkum skb to user iovec.
796  *      @skb: skbuff
797  *      @hlen: hardware length
798  *      @iov: io vector
799  *      @len: amount of data to copy from skb to iov
800  *
801  *      Caller _must_ check that skb will fit to this iovec.
802  *
803  *      Returns: 0       - success.
804  *               -EINVAL - checksum failure.
805  *               -EFAULT - fault during copy. Beware, in this case iovec
806  *                         can be modified!
807  */
808 int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
809                                      int hlen, struct iovec *iov, int len)
810 {
811         __wsum csum;
812         int chunk = skb->len - hlen;
813 
814         if (chunk > len)
815                 chunk = len;
816 
817         if (!chunk)
818                 return 0;
819 
820         /* Skip filled elements.
821          * Pretty silly, look at memcpy_toiovec, though 8)
822          */
823         while (!iov->iov_len)
824                 iov++;
825 
826         if (iov->iov_len < chunk) {
827                 if (__skb_checksum_complete(skb))
828                         goto csum_error;
829                 if (skb_copy_datagram_iovec(skb, hlen, iov, chunk))
830                         goto fault;
831         } else {
832                 csum = csum_partial(skb->data, hlen, skb->csum);
833                 if (skb_copy_and_csum_datagram(skb, hlen, iov->iov_base,
834                                                chunk, &csum))
835                         goto fault;
836                 if (csum_fold(csum))
837                         goto csum_error;
838                 if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
839                         netdev_rx_csum_fault(skb->dev);
840                 iov->iov_len -= chunk;
841                 iov->iov_base += chunk;
842         }
843         return 0;
844 csum_error:
845         return -EINVAL;
846 fault:
847         return -EFAULT;
848 }
849 EXPORT_SYMBOL(skb_copy_and_csum_datagram_iovec);
850 
851 /**
852  *      datagram_poll - generic datagram poll
853  *      @file: file struct
854  *      @sock: socket
855  *      @wait: poll table
856  *
857  *      Datagram poll: Again totally generic. This also handles
858  *      sequenced packet sockets providing the socket receive queue
859  *      is only ever holding data ready to receive.
860  *
861  *      Note: when you _don't_ use this routine for this protocol,
862  *      and you use a different write policy from sock_writeable()
863  *      then please supply your own write_space callback.
864  */
865 unsigned int datagram_poll(struct file *file, struct socket *sock,
866                            poll_table *wait)
867 {
868         struct sock *sk = sock->sk;
869         unsigned int mask;
870 
871         sock_poll_wait(file, sk_sleep(sk), wait);
872         mask = 0;
873 
874         /* exceptional events? */
875         if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
876                 mask |= POLLERR |
877                         (sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0);
878 
879         if (sk->sk_shutdown & RCV_SHUTDOWN)
880                 mask |= POLLRDHUP | POLLIN | POLLRDNORM;
881         if (sk->sk_shutdown == SHUTDOWN_MASK)
882                 mask |= POLLHUP;
883 
884         /* readable? */
885         if (!skb_queue_empty(&sk->sk_receive_queue))
886                 mask |= POLLIN | POLLRDNORM;
887 
888         /* Connection-based need to check for termination and startup */
889         if (connection_based(sk)) {
890                 if (sk->sk_state == TCP_CLOSE)
891                         mask |= POLLHUP;
892                 /* connection hasn't started yet? */
893                 if (sk->sk_state == TCP_SYN_SENT)
894                         return mask;
895         }
896 
897         /* writable? */
898         if (sock_writeable(sk))
899                 mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
900         else
901                 set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
902 
903         return mask;
904 }
905 EXPORT_SYMBOL(datagram_poll);
906 

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