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.
12 * Authors: Alan Cox <alan@lxorguk.ukuu.org.uk>. (datagram_poll() from old
16 * Alan Cox : NULL return from skb_peek_copy()
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
24 * Alan Cox : Fixed write poll of non IP protocol
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.
36 #include <linux/module.h>
37 #include <linux/types.h>
38 #include <linux/kernel.h>
39 #include <asm/uaccess.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 #include <linux/uio.h>
54 #include <net/protocol.h>
55 #include <linux/skbuff.h>
57 #include <net/checksum.h>
59 #include <net/tcp_states.h>
60 #include <trace/events/skb.h>
61 #include <net/busy_poll.h>
64 * Is a socket 'connection oriented' ?
66 static inline int connection_based(struct sock
*sk
)
68 return sk
->sk_type
== SOCK_SEQPACKET
|| sk
->sk_type
== SOCK_STREAM
;
71 static int receiver_wake_function(wait_queue_t
*wait
, unsigned int mode
, int sync
,
74 unsigned long bits
= (unsigned long)key
;
77 * Avoid a wakeup if event not interesting for us
79 if (bits
&& !(bits
& (POLLIN
| POLLERR
)))
81 return autoremove_wake_function(wait
, mode
, sync
, key
);
84 * Wait for the last received packet to be different from skb
86 static int wait_for_more_packets(struct sock
*sk
, int *err
, long *timeo_p
,
87 const struct sk_buff
*skb
)
90 DEFINE_WAIT_FUNC(wait
, receiver_wake_function
);
92 prepare_to_wait_exclusive(sk_sleep(sk
), &wait
, TASK_INTERRUPTIBLE
);
95 error
= sock_error(sk
);
99 if (sk
->sk_receive_queue
.prev
!= skb
)
102 /* Socket shut down? */
103 if (sk
->sk_shutdown
& RCV_SHUTDOWN
)
106 /* Sequenced packets can come disconnected.
107 * If so we report the problem
110 if (connection_based(sk
) &&
111 !(sk
->sk_state
== TCP_ESTABLISHED
|| sk
->sk_state
== TCP_LISTEN
))
115 if (signal_pending(current
))
119 *timeo_p
= schedule_timeout(*timeo_p
);
121 finish_wait(sk_sleep(sk
), &wait
);
124 error
= sock_intr_errno(*timeo_p
);
134 static int skb_set_peeked(struct sk_buff
*skb
)
136 struct sk_buff
*nskb
;
141 /* We have to unshare an skb before modifying it. */
142 if (!skb_shared(skb
))
145 nskb
= skb_clone(skb
, GFP_ATOMIC
);
149 skb
->prev
->next
= nskb
;
150 skb
->next
->prev
= nskb
;
151 nskb
->prev
= skb
->prev
;
152 nskb
->next
= skb
->next
;
164 * __skb_recv_datagram - Receive a datagram skbuff
167 * @peeked: returns non-zero if this packet has been seen before
168 * @off: an offset in bytes to peek skb from. Returns an offset
169 * within an skb where data actually starts
170 * @err: error code returned
172 * Get a datagram skbuff, understands the peeking, nonblocking wakeups
173 * and possible races. This replaces identical code in packet, raw and
174 * udp, as well as the IPX AX.25 and Appletalk. It also finally fixes
175 * the long standing peek and read race for datagram sockets. If you
176 * alter this routine remember it must be re-entrant.
178 * This function will lock the socket if a skb is returned, so the caller
179 * needs to unlock the socket in that case (usually by calling
182 * * It does not lock socket since today. This function is
183 * * free of race conditions. This measure should/can improve
184 * * significantly datagram socket latencies at high loads,
185 * * when data copying to user space takes lots of time.
186 * * (BTW I've just killed the last cli() in IP/IPv6/core/netlink/packet
190 * The order of the tests when we find no data waiting are specified
191 * quite explicitly by POSIX 1003.1g, don't change them without having
192 * the standard around please.
194 struct sk_buff
*__skb_recv_datagram(struct sock
*sk
, unsigned int flags
,
195 int *peeked
, int *off
, int *err
)
197 struct sk_buff_head
*queue
= &sk
->sk_receive_queue
;
198 struct sk_buff
*skb
, *last
;
199 unsigned long cpu_flags
;
202 * Caller is allowed not to check sk->sk_err before skb_recv_datagram()
204 int error
= sock_error(sk
);
209 timeo
= sock_rcvtimeo(sk
, flags
& MSG_DONTWAIT
);
212 /* Again only user level code calls this function, so nothing
213 * interrupt level will suddenly eat the receive_queue.
215 * Look at current nfs client by the way...
216 * However, this function was correct in any case. 8)
220 last
= (struct sk_buff
*)queue
;
221 spin_lock_irqsave(&queue
->lock
, cpu_flags
);
222 skb_queue_walk(queue
, skb
) {
224 *peeked
= skb
->peeked
;
225 if (flags
& MSG_PEEK
) {
226 if (_off
>= skb
->len
&& (skb
->len
|| _off
||
232 error
= skb_set_peeked(skb
);
236 atomic_inc(&skb
->users
);
238 __skb_unlink(skb
, queue
);
240 spin_unlock_irqrestore(&queue
->lock
, cpu_flags
);
244 spin_unlock_irqrestore(&queue
->lock
, cpu_flags
);
246 if (sk_can_busy_loop(sk
) &&
247 sk_busy_loop(sk
, flags
& MSG_DONTWAIT
))
250 /* User doesn't want to wait */
255 } while (!wait_for_more_packets(sk
, err
, &timeo
, last
));
260 spin_unlock_irqrestore(&queue
->lock
, cpu_flags
);
265 EXPORT_SYMBOL(__skb_recv_datagram
);
267 struct sk_buff
*skb_recv_datagram(struct sock
*sk
, unsigned int flags
,
268 int noblock
, int *err
)
272 return __skb_recv_datagram(sk
, flags
| (noblock
? MSG_DONTWAIT
: 0),
275 EXPORT_SYMBOL(skb_recv_datagram
);
277 void skb_free_datagram(struct sock
*sk
, struct sk_buff
*skb
)
280 sk_mem_reclaim_partial(sk
);
282 EXPORT_SYMBOL(skb_free_datagram
);
284 void skb_free_datagram_locked(struct sock
*sk
, struct sk_buff
*skb
)
288 if (likely(atomic_read(&skb
->users
) == 1))
290 else if (likely(!atomic_dec_and_test(&skb
->users
)))
293 slow
= lock_sock_fast(sk
);
295 sk_mem_reclaim_partial(sk
);
296 unlock_sock_fast(sk
, slow
);
298 /* skb is now orphaned, can be freed outside of locked section */
301 EXPORT_SYMBOL(skb_free_datagram_locked
);
304 * skb_kill_datagram - Free a datagram skbuff forcibly
306 * @skb: datagram skbuff
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.
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.
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.
321 * It returns 0 if the packet was removed by us.
324 int skb_kill_datagram(struct sock
*sk
, struct sk_buff
*skb
, unsigned int flags
)
328 if (flags
& MSG_PEEK
) {
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
);
336 spin_unlock_bh(&sk
->sk_receive_queue
.lock
);
340 atomic_inc(&sk
->sk_drops
);
341 sk_mem_reclaim_partial(sk
);
345 EXPORT_SYMBOL(skb_kill_datagram
);
348 * skb_copy_datagram_iter - Copy a datagram to an iovec iterator.
349 * @skb: buffer to copy
350 * @offset: offset in the buffer to start copying from
351 * @to: iovec iterator to copy to
352 * @len: amount of data to copy from buffer to iovec
354 int skb_copy_datagram_iter(const struct sk_buff
*skb
, int offset
,
355 struct iov_iter
*to
, int len
)
357 int start
= skb_headlen(skb
);
358 int i
, copy
= start
- offset
;
359 struct sk_buff
*frag_iter
;
361 trace_skb_copy_datagram_iovec(skb
, len
);
367 if (copy_to_iter(skb
->data
+ offset
, copy
, to
) != copy
)
369 if ((len
-= copy
) == 0)
374 /* Copy paged appendix. Hmm... why does this look so complicated? */
375 for (i
= 0; i
< skb_shinfo(skb
)->nr_frags
; i
++) {
377 const skb_frag_t
*frag
= &skb_shinfo(skb
)->frags
[i
];
379 WARN_ON(start
> offset
+ len
);
381 end
= start
+ skb_frag_size(frag
);
382 if ((copy
= end
- offset
) > 0) {
385 if (copy_page_to_iter(skb_frag_page(frag
),
386 frag
->page_offset
+ offset
-
387 start
, copy
, to
) != copy
)
396 skb_walk_frags(skb
, frag_iter
) {
399 WARN_ON(start
> offset
+ len
);
401 end
= start
+ frag_iter
->len
;
402 if ((copy
= end
- offset
) > 0) {
405 if (skb_copy_datagram_iter(frag_iter
, offset
- start
,
408 if ((len
-= copy
) == 0)
417 /* This is not really a user copy fault, but rather someone
418 * gave us a bogus length on the skb. We should probably
419 * print a warning here as it may indicate a kernel bug.
426 if (iov_iter_count(to
))
431 EXPORT_SYMBOL(skb_copy_datagram_iter
);
434 * skb_copy_datagram_from_iter - Copy a datagram from an iov_iter.
435 * @skb: buffer to copy
436 * @offset: offset in the buffer to start copying to
437 * @from: the copy source
438 * @len: amount of data to copy to buffer from iovec
440 * Returns 0 or -EFAULT.
442 int skb_copy_datagram_from_iter(struct sk_buff
*skb
, int offset
,
443 struct iov_iter
*from
,
446 int start
= skb_headlen(skb
);
447 int i
, copy
= start
- offset
;
448 struct sk_buff
*frag_iter
;
454 if (copy_from_iter(skb
->data
+ offset
, copy
, from
) != copy
)
456 if ((len
-= copy
) == 0)
461 /* Copy paged appendix. Hmm... why does this look so complicated? */
462 for (i
= 0; i
< skb_shinfo(skb
)->nr_frags
; i
++) {
464 const skb_frag_t
*frag
= &skb_shinfo(skb
)->frags
[i
];
466 WARN_ON(start
> offset
+ len
);
468 end
= start
+ skb_frag_size(frag
);
469 if ((copy
= end
- offset
) > 0) {
474 copied
= copy_page_from_iter(skb_frag_page(frag
),
475 frag
->page_offset
+ offset
- start
,
487 skb_walk_frags(skb
, frag_iter
) {
490 WARN_ON(start
> offset
+ len
);
492 end
= start
+ frag_iter
->len
;
493 if ((copy
= end
- offset
) > 0) {
496 if (skb_copy_datagram_from_iter(frag_iter
,
500 if ((len
-= copy
) == 0)
512 EXPORT_SYMBOL(skb_copy_datagram_from_iter
);
515 * zerocopy_sg_from_iter - Build a zerocopy datagram from an iov_iter
516 * @skb: buffer to copy
517 * @from: the source to copy from
519 * The function will first copy up to headlen, and then pin the userspace
520 * pages and build frags through them.
522 * Returns 0, -EFAULT or -EMSGSIZE.
524 int zerocopy_sg_from_iter(struct sk_buff
*skb
, struct iov_iter
*from
)
526 int len
= iov_iter_count(from
);
527 int copy
= min_t(int, skb_headlen(skb
), len
);
530 /* copy up to skb headlen */
531 if (skb_copy_datagram_from_iter(skb
, 0, from
, copy
))
534 while (iov_iter_count(from
)) {
535 struct page
*pages
[MAX_SKB_FRAGS
];
538 unsigned long truesize
;
541 if (frag
== MAX_SKB_FRAGS
)
544 copied
= iov_iter_get_pages(from
, pages
, ~0U,
545 MAX_SKB_FRAGS
- frag
, &start
);
549 iov_iter_advance(from
, copied
);
551 truesize
= PAGE_ALIGN(copied
+ start
);
552 skb
->data_len
+= copied
;
554 skb
->truesize
+= truesize
;
555 atomic_add(truesize
, &skb
->sk
->sk_wmem_alloc
);
557 int size
= min_t(int, copied
, PAGE_SIZE
- start
);
558 skb_fill_page_desc(skb
, frag
++, pages
[n
], start
, size
);
566 EXPORT_SYMBOL(zerocopy_sg_from_iter
);
568 static int skb_copy_and_csum_datagram(const struct sk_buff
*skb
, int offset
,
569 struct iov_iter
*to
, int len
,
572 int start
= skb_headlen(skb
);
573 int i
, copy
= start
- offset
;
574 struct sk_buff
*frag_iter
;
582 n
= csum_and_copy_to_iter(skb
->data
+ offset
, copy
, csump
, to
);
585 if ((len
-= copy
) == 0)
591 for (i
= 0; i
< skb_shinfo(skb
)->nr_frags
; i
++) {
593 const skb_frag_t
*frag
= &skb_shinfo(skb
)->frags
[i
];
595 WARN_ON(start
> offset
+ len
);
597 end
= start
+ skb_frag_size(frag
);
598 if ((copy
= end
- offset
) > 0) {
600 struct page
*page
= skb_frag_page(frag
);
601 u8
*vaddr
= kmap(page
);
605 n
= csum_and_copy_to_iter(vaddr
+ frag
->page_offset
+
606 offset
- start
, copy
,
611 *csump
= csum_block_add(*csump
, csum2
, pos
);
620 skb_walk_frags(skb
, frag_iter
) {
623 WARN_ON(start
> offset
+ len
);
625 end
= start
+ frag_iter
->len
;
626 if ((copy
= end
- offset
) > 0) {
630 if (skb_copy_and_csum_datagram(frag_iter
,
635 *csump
= csum_block_add(*csump
, csum2
, pos
);
636 if ((len
-= copy
) == 0)
650 __sum16
__skb_checksum_complete_head(struct sk_buff
*skb
, int len
)
654 sum
= csum_fold(skb_checksum(skb
, 0, len
, skb
->csum
));
656 if (unlikely(skb
->ip_summed
== CHECKSUM_COMPLETE
) &&
657 !skb
->csum_complete_sw
)
658 netdev_rx_csum_fault(skb
->dev
);
660 if (!skb_shared(skb
))
661 skb
->csum_valid
= !sum
;
664 EXPORT_SYMBOL(__skb_checksum_complete_head
);
666 __sum16
__skb_checksum_complete(struct sk_buff
*skb
)
671 csum
= skb_checksum(skb
, 0, skb
->len
, 0);
673 /* skb->csum holds pseudo checksum */
674 sum
= csum_fold(csum_add(skb
->csum
, csum
));
676 if (unlikely(skb
->ip_summed
== CHECKSUM_COMPLETE
) &&
677 !skb
->csum_complete_sw
)
678 netdev_rx_csum_fault(skb
->dev
);
681 if (!skb_shared(skb
)) {
682 /* Save full packet checksum */
684 skb
->ip_summed
= CHECKSUM_COMPLETE
;
685 skb
->csum_complete_sw
= 1;
686 skb
->csum_valid
= !sum
;
691 EXPORT_SYMBOL(__skb_checksum_complete
);
694 * skb_copy_and_csum_datagram_msg - Copy and checksum skb to user iovec.
696 * @hlen: hardware length
699 * Caller _must_ check that skb will fit to this iovec.
701 * Returns: 0 - success.
702 * -EINVAL - checksum failure.
703 * -EFAULT - fault during copy.
705 int skb_copy_and_csum_datagram_msg(struct sk_buff
*skb
,
706 int hlen
, struct msghdr
*msg
)
709 int chunk
= skb
->len
- hlen
;
714 if (msg_data_left(msg
) < chunk
) {
715 if (__skb_checksum_complete(skb
))
717 if (skb_copy_datagram_msg(skb
, hlen
, msg
, chunk
))
720 csum
= csum_partial(skb
->data
, hlen
, skb
->csum
);
721 if (skb_copy_and_csum_datagram(skb
, hlen
, &msg
->msg_iter
,
726 if (unlikely(skb
->ip_summed
== CHECKSUM_COMPLETE
))
727 netdev_rx_csum_fault(skb
->dev
);
735 EXPORT_SYMBOL(skb_copy_and_csum_datagram_msg
);
738 * datagram_poll - generic datagram poll
743 * Datagram poll: Again totally generic. This also handles
744 * sequenced packet sockets providing the socket receive queue
745 * is only ever holding data ready to receive.
747 * Note: when you _don't_ use this routine for this protocol,
748 * and you use a different write policy from sock_writeable()
749 * then please supply your own write_space callback.
751 unsigned int datagram_poll(struct file
*file
, struct socket
*sock
,
754 struct sock
*sk
= sock
->sk
;
757 sock_poll_wait(file
, sk_sleep(sk
), wait
);
760 /* exceptional events? */
761 if (sk
->sk_err
|| !skb_queue_empty(&sk
->sk_error_queue
))
763 (sock_flag(sk
, SOCK_SELECT_ERR_QUEUE
) ? POLLPRI
: 0);
765 if (sk
->sk_shutdown
& RCV_SHUTDOWN
)
766 mask
|= POLLRDHUP
| POLLIN
| POLLRDNORM
;
767 if (sk
->sk_shutdown
== SHUTDOWN_MASK
)
771 if (!skb_queue_empty(&sk
->sk_receive_queue
))
772 mask
|= POLLIN
| POLLRDNORM
;
774 /* Connection-based need to check for termination and startup */
775 if (connection_based(sk
)) {
776 if (sk
->sk_state
== TCP_CLOSE
)
778 /* connection hasn't started yet? */
779 if (sk
->sk_state
== TCP_SYN_SENT
)
784 if (sock_writeable(sk
))
785 mask
|= POLLOUT
| POLLWRNORM
| POLLWRBAND
;
787 set_bit(SOCK_ASYNC_NOSPACE
, &sk
->sk_socket
->flags
);
791 EXPORT_SYMBOL(datagram_poll
);