1// SPDX-License-Identifier: GPL-2.0
2/*
3 * SUCS NET3:
4 *
5 * Generic datagram handling routines. These are generic for all
6 * protocols. Possibly a generic IP version on top of these would
7 * make sense. Not tonight however 8-).
8 * This is used because UDP, RAW, PACKET, DDP, IPX, AX.25 and
9 * NetROM layer all have identical poll code and mostly
10 * identical recvmsg() code. So we share it here. The poll was
11 * shared before but buried in udp.c so I moved it.
12 *
13 * Authors: Alan Cox <alan@lxorguk.ukuu.org.uk>. (datagram_poll() from old
14 * udp.c code)
15 *
16 * Fixes:
17 * Alan Cox : NULL return from skb_peek_copy()
18 * understood
19 * Alan Cox : Rewrote skb_read_datagram to avoid the
20 * skb_peek_copy stuff.
21 * Alan Cox : Added support for SOCK_SEQPACKET.
22 * IPX can no longer use the SO_TYPE hack
23 * but AX.25 now works right, and SPX is
24 * feasible.
25 * Alan Cox : Fixed write poll of non IP protocol
26 * crash.
27 * Florian La Roche: Changed for my new skbuff handling.
28 * Darryl Miles : Fixed non-blocking SOCK_SEQPACKET.
29 * Linus Torvalds : BSD semantic fixes.
30 * Alan Cox : Datagram iovec handling
31 * Darryl Miles : Fixed non-blocking SOCK_STREAM.
32 * Alan Cox : POSIXisms
33 * Pete Wyckoff : Unconnected accept() fix.
34 *
35 */
36
37#include <linux/module.h>
38#include <linux/types.h>
39#include <linux/kernel.h>
40#include <linux/uaccess.h>
41#include <linux/mm.h>
42#include <linux/interrupt.h>
43#include <linux/errno.h>
44#include <linux/sched.h>
45#include <linux/inet.h>
46#include <linux/netdevice.h>
47#include <linux/rtnetlink.h>
48#include <linux/poll.h>
49#include <linux/highmem.h>
50#include <linux/spinlock.h>
51#include <linux/slab.h>
52#include <linux/pagemap.h>
53#include <linux/iov_iter.h>
54#include <linux/indirect_call_wrapper.h>
55
56#include <net/protocol.h>
57#include <linux/skbuff.h>
58
59#include <net/checksum.h>
60#include <net/sock.h>
61#include <net/tcp_states.h>
62#include <trace/events/skb.h>
63#include <net/busy_poll.h>
64#include <crypto/hash.h>
65
66/*
67 * Is a socket 'connection oriented' ?
68 */
69static inline int connection_based(struct sock *sk)
70{
71 return sk->sk_type == SOCK_SEQPACKET || sk->sk_type == SOCK_STREAM;
72}
73
74static int receiver_wake_function(wait_queue_entry_t *wait, unsigned int mode, int sync,
75 void *key)
76{
77 /*
78 * Avoid a wakeup if event not interesting for us
79 */
80 if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR)))
81 return 0;
82 return autoremove_wake_function(wq_entry: wait, mode, sync, key);
83}
84/*
85 * Wait for the last received packet to be different from skb
86 */
87int __skb_wait_for_more_packets(struct sock *sk, struct sk_buff_head *queue,
88 int *err, long *timeo_p,
89 const struct sk_buff *skb)
90{
91 int error;
92 DEFINE_WAIT_FUNC(wait, receiver_wake_function);
93
94 prepare_to_wait_exclusive(wq_head: sk_sleep(sk), wq_entry: &wait, TASK_INTERRUPTIBLE);
95
96 /* Socket errors? */
97 error = sock_error(sk);
98 if (error)
99 goto out_err;
100
101 if (READ_ONCE(queue->prev) != skb)
102 goto out;
103
104 /* Socket shut down? */
105 if (sk->sk_shutdown & RCV_SHUTDOWN)
106 goto out_noerr;
107
108 /* Sequenced packets can come disconnected.
109 * If so we report the problem
110 */
111 error = -ENOTCONN;
112 if (connection_based(sk) &&
113 !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN))
114 goto out_err;
115
116 /* handle signals */
117 if (signal_pending(current))
118 goto interrupted;
119
120 error = 0;
121 *timeo_p = schedule_timeout(timeout: *timeo_p);
122out:
123 finish_wait(wq_head: sk_sleep(sk), wq_entry: &wait);
124 return error;
125interrupted:
126 error = sock_intr_errno(timeo: *timeo_p);
127out_err:
128 *err = error;
129 goto out;
130out_noerr:
131 *err = 0;
132 error = 1;
133 goto out;
134}
135EXPORT_SYMBOL(__skb_wait_for_more_packets);
136
137static struct sk_buff *skb_set_peeked(struct sk_buff *skb)
138{
139 struct sk_buff *nskb;
140
141 if (skb->peeked)
142 return skb;
143
144 /* We have to unshare an skb before modifying it. */
145 if (!skb_shared(skb))
146 goto done;
147
148 nskb = skb_clone(skb, GFP_ATOMIC);
149 if (!nskb)
150 return ERR_PTR(error: -ENOMEM);
151
152 skb->prev->next = nskb;
153 skb->next->prev = nskb;
154 nskb->prev = skb->prev;
155 nskb->next = skb->next;
156
157 consume_skb(skb);
158 skb = nskb;
159
160done:
161 skb->peeked = 1;
162
163 return skb;
164}
165
166struct sk_buff *__skb_try_recv_from_queue(struct sock *sk,
167 struct sk_buff_head *queue,
168 unsigned int flags,
169 int *off, int *err,
170 struct sk_buff **last)
171{
172 bool peek_at_off = false;
173 struct sk_buff *skb;
174 int _off = 0;
175
176 if (unlikely(flags & MSG_PEEK && *off >= 0)) {
177 peek_at_off = true;
178 _off = *off;
179 }
180
181 *last = queue->prev;
182 skb_queue_walk(queue, skb) {
183 if (flags & MSG_PEEK) {
184 if (peek_at_off && _off >= skb->len &&
185 (_off || skb->peeked)) {
186 _off -= skb->len;
187 continue;
188 }
189 if (!skb->len) {
190 skb = skb_set_peeked(skb);
191 if (IS_ERR(ptr: skb)) {
192 *err = PTR_ERR(ptr: skb);
193 return NULL;
194 }
195 }
196 refcount_inc(r: &skb->users);
197 } else {
198 __skb_unlink(skb, list: queue);
199 }
200 *off = _off;
201 return skb;
202 }
203 return NULL;
204}
205
206/**
207 * __skb_try_recv_datagram - Receive a datagram skbuff
208 * @sk: socket
209 * @queue: socket queue from which to receive
210 * @flags: MSG\_ flags
211 * @off: an offset in bytes to peek skb from. Returns an offset
212 * within an skb where data actually starts
213 * @err: error code returned
214 * @last: set to last peeked message to inform the wait function
215 * what to look for when peeking
216 *
217 * Get a datagram skbuff, understands the peeking, nonblocking wakeups
218 * and possible races. This replaces identical code in packet, raw and
219 * udp, as well as the IPX AX.25 and Appletalk. It also finally fixes
220 * the long standing peek and read race for datagram sockets. If you
221 * alter this routine remember it must be re-entrant.
222 *
223 * This function will lock the socket if a skb is returned, so
224 * the caller needs to unlock the socket in that case (usually by
225 * calling skb_free_datagram). Returns NULL with @err set to
226 * -EAGAIN if no data was available or to some other value if an
227 * error was detected.
228 *
229 * * It does not lock socket since today. This function is
230 * * free of race conditions. This measure should/can improve
231 * * significantly datagram socket latencies at high loads,
232 * * when data copying to user space takes lots of time.
233 * * (BTW I've just killed the last cli() in IP/IPv6/core/netlink/packet
234 * * 8) Great win.)
235 * * --ANK (980729)
236 *
237 * The order of the tests when we find no data waiting are specified
238 * quite explicitly by POSIX 1003.1g, don't change them without having
239 * the standard around please.
240 */
241struct sk_buff *__skb_try_recv_datagram(struct sock *sk,
242 struct sk_buff_head *queue,
243 unsigned int flags, int *off, int *err,
244 struct sk_buff **last)
245{
246 struct sk_buff *skb;
247 unsigned long cpu_flags;
248 /*
249 * Caller is allowed not to check sk->sk_err before skb_recv_datagram()
250 */
251 int error = sock_error(sk);
252
253 if (error)
254 goto no_packet;
255
256 do {
257 /* Again only user level code calls this function, so nothing
258 * interrupt level will suddenly eat the receive_queue.
259 *
260 * Look at current nfs client by the way...
261 * However, this function was correct in any case. 8)
262 */
263 spin_lock_irqsave(&queue->lock, cpu_flags);
264 skb = __skb_try_recv_from_queue(sk, queue, flags, off, err: &error,
265 last);
266 spin_unlock_irqrestore(lock: &queue->lock, flags: cpu_flags);
267 if (error)
268 goto no_packet;
269 if (skb)
270 return skb;
271
272 if (!sk_can_busy_loop(sk))
273 break;
274
275 sk_busy_loop(sk, nonblock: flags & MSG_DONTWAIT);
276 } while (READ_ONCE(queue->prev) != *last);
277
278 error = -EAGAIN;
279
280no_packet:
281 *err = error;
282 return NULL;
283}
284EXPORT_SYMBOL(__skb_try_recv_datagram);
285
286struct sk_buff *__skb_recv_datagram(struct sock *sk,
287 struct sk_buff_head *sk_queue,
288 unsigned int flags, int *off, int *err)
289{
290 struct sk_buff *skb, *last;
291 long timeo;
292
293 timeo = sock_rcvtimeo(sk, noblock: flags & MSG_DONTWAIT);
294
295 do {
296 skb = __skb_try_recv_datagram(sk, sk_queue, flags, off, err,
297 &last);
298 if (skb)
299 return skb;
300
301 if (*err != -EAGAIN)
302 break;
303 } while (timeo &&
304 !__skb_wait_for_more_packets(sk, sk_queue, err,
305 &timeo, last));
306
307 return NULL;
308}
309EXPORT_SYMBOL(__skb_recv_datagram);
310
311struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags,
312 int *err)
313{
314 int off = 0;
315
316 return __skb_recv_datagram(sk, &sk->sk_receive_queue, flags,
317 &off, err);
318}
319EXPORT_SYMBOL(skb_recv_datagram);
320
321void skb_free_datagram(struct sock *sk, struct sk_buff *skb)
322{
323 consume_skb(skb);
324}
325EXPORT_SYMBOL(skb_free_datagram);
326
327void __skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb, int len)
328{
329 bool slow;
330
331 if (!skb_unref(skb)) {
332 sk_peek_offset_bwd(sk, val: len);
333 return;
334 }
335
336 slow = lock_sock_fast(sk);
337 sk_peek_offset_bwd(sk, val: len);
338 skb_orphan(skb);
339 unlock_sock_fast(sk, slow);
340
341 /* skb is now orphaned, can be freed outside of locked section */
342 __kfree_skb(skb);
343}
344EXPORT_SYMBOL(__skb_free_datagram_locked);
345
346int __sk_queue_drop_skb(struct sock *sk, struct sk_buff_head *sk_queue,
347 struct sk_buff *skb, unsigned int flags,
348 void (*destructor)(struct sock *sk,
349 struct sk_buff *skb))
350{
351 int err = 0;
352
353 if (flags & MSG_PEEK) {
354 err = -ENOENT;
355 spin_lock_bh(lock: &sk_queue->lock);
356 if (skb->next) {
357 __skb_unlink(skb, list: sk_queue);
358 refcount_dec(r: &skb->users);
359 if (destructor)
360 destructor(sk, skb);
361 err = 0;
362 }
363 spin_unlock_bh(lock: &sk_queue->lock);
364 }
365
366 atomic_inc(v: &sk->sk_drops);
367 return err;
368}
369EXPORT_SYMBOL(__sk_queue_drop_skb);
370
371/**
372 * skb_kill_datagram - Free a datagram skbuff forcibly
373 * @sk: socket
374 * @skb: datagram skbuff
375 * @flags: MSG\_ flags
376 *
377 * This function frees a datagram skbuff that was received by
378 * skb_recv_datagram. The flags argument must match the one
379 * used for skb_recv_datagram.
380 *
381 * If the MSG_PEEK flag is set, and the packet is still on the
382 * receive queue of the socket, it will be taken off the queue
383 * before it is freed.
384 *
385 * This function currently only disables BH when acquiring the
386 * sk_receive_queue lock. Therefore it must not be used in a
387 * context where that lock is acquired in an IRQ context.
388 *
389 * It returns 0 if the packet was removed by us.
390 */
391
392int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)
393{
394 int err = __sk_queue_drop_skb(sk, &sk->sk_receive_queue, skb, flags,
395 NULL);
396
397 kfree_skb(skb);
398 return err;
399}
400EXPORT_SYMBOL(skb_kill_datagram);
401
402INDIRECT_CALLABLE_DECLARE(static size_t simple_copy_to_iter(const void *addr,
403 size_t bytes,
404 void *data __always_unused,
405 struct iov_iter *i));
406
407static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
408 struct iov_iter *to, int len, bool fault_short,
409 size_t (*cb)(const void *, size_t, void *,
410 struct iov_iter *), void *data)
411{
412 int start = skb_headlen(skb);
413 int i, copy = start - offset, start_off = offset, n;
414 struct sk_buff *frag_iter;
415
416 /* Copy header. */
417 if (copy > 0) {
418 if (copy > len)
419 copy = len;
420 n = INDIRECT_CALL_1(cb, simple_copy_to_iter,
421 skb->data + offset, copy, data, to);
422 offset += n;
423 if (n != copy)
424 goto short_copy;
425 if ((len -= copy) == 0)
426 return 0;
427 }
428
429 /* Copy paged appendix. Hmm... why does this look so complicated? */
430 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
431 int end;
432 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
433
434 WARN_ON(start > offset + len);
435
436 end = start + skb_frag_size(frag);
437 if ((copy = end - offset) > 0) {
438 struct page *page = skb_frag_page(frag);
439 u8 *vaddr = kmap(page);
440
441 if (copy > len)
442 copy = len;
443 n = INDIRECT_CALL_1(cb, simple_copy_to_iter,
444 vaddr + skb_frag_off(frag) + offset - start,
445 copy, data, to);
446 kunmap(page);
447 offset += n;
448 if (n != copy)
449 goto short_copy;
450 if (!(len -= copy))
451 return 0;
452 }
453 start = end;
454 }
455
456 skb_walk_frags(skb, frag_iter) {
457 int end;
458
459 WARN_ON(start > offset + len);
460
461 end = start + frag_iter->len;
462 if ((copy = end - offset) > 0) {
463 if (copy > len)
464 copy = len;
465 if (__skb_datagram_iter(skb: frag_iter, offset: offset - start,
466 to, len: copy, fault_short, cb, data))
467 goto fault;
468 if ((len -= copy) == 0)
469 return 0;
470 offset += copy;
471 }
472 start = end;
473 }
474 if (!len)
475 return 0;
476
477 /* This is not really a user copy fault, but rather someone
478 * gave us a bogus length on the skb. We should probably
479 * print a warning here as it may indicate a kernel bug.
480 */
481
482fault:
483 iov_iter_revert(i: to, bytes: offset - start_off);
484 return -EFAULT;
485
486short_copy:
487 if (fault_short || iov_iter_count(i: to))
488 goto fault;
489
490 return 0;
491}
492
493static size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
494 struct iov_iter *i)
495{
496#ifdef CONFIG_CRYPTO_HASH
497 struct ahash_request *hash = hashp;
498 struct scatterlist sg;
499 size_t copied;
500
501 copied = copy_to_iter(addr, bytes, i);
502 sg_init_one(&sg, addr, copied);
503 ahash_request_set_crypt(req: hash, src: &sg, NULL, nbytes: copied);
504 crypto_ahash_update(req: hash);
505 return copied;
506#else
507 return 0;
508#endif
509}
510
511/**
512 * skb_copy_and_hash_datagram_iter - Copy datagram to an iovec iterator
513 * and update a hash.
514 * @skb: buffer to copy
515 * @offset: offset in the buffer to start copying from
516 * @to: iovec iterator to copy to
517 * @len: amount of data to copy from buffer to iovec
518 * @hash: hash request to update
519 */
520int skb_copy_and_hash_datagram_iter(const struct sk_buff *skb, int offset,
521 struct iov_iter *to, int len,
522 struct ahash_request *hash)
523{
524 return __skb_datagram_iter(skb, offset, to, len, fault_short: true,
525 cb: hash_and_copy_to_iter, data: hash);
526}
527EXPORT_SYMBOL(skb_copy_and_hash_datagram_iter);
528
529static size_t simple_copy_to_iter(const void *addr, size_t bytes,
530 void *data __always_unused, struct iov_iter *i)
531{
532 return copy_to_iter(addr, bytes, i);
533}
534
535/**
536 * skb_copy_datagram_iter - Copy a datagram to an iovec iterator.
537 * @skb: buffer to copy
538 * @offset: offset in the buffer to start copying from
539 * @to: iovec iterator to copy to
540 * @len: amount of data to copy from buffer to iovec
541 */
542int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
543 struct iov_iter *to, int len)
544{
545 trace_skb_copy_datagram_iovec(skb, len);
546 return __skb_datagram_iter(skb, offset, to, len, fault_short: false,
547 cb: simple_copy_to_iter, NULL);
548}
549EXPORT_SYMBOL(skb_copy_datagram_iter);
550
551/**
552 * skb_copy_datagram_from_iter - Copy a datagram from an iov_iter.
553 * @skb: buffer to copy
554 * @offset: offset in the buffer to start copying to
555 * @from: the copy source
556 * @len: amount of data to copy to buffer from iovec
557 *
558 * Returns 0 or -EFAULT.
559 */
560int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
561 struct iov_iter *from,
562 int len)
563{
564 int start = skb_headlen(skb);
565 int i, copy = start - offset;
566 struct sk_buff *frag_iter;
567
568 /* Copy header. */
569 if (copy > 0) {
570 if (copy > len)
571 copy = len;
572 if (copy_from_iter(addr: skb->data + offset, bytes: copy, i: from) != copy)
573 goto fault;
574 if ((len -= copy) == 0)
575 return 0;
576 offset += copy;
577 }
578
579 /* Copy paged appendix. Hmm... why does this look so complicated? */
580 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
581 int end;
582 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
583
584 WARN_ON(start > offset + len);
585
586 end = start + skb_frag_size(frag);
587 if ((copy = end - offset) > 0) {
588 size_t copied;
589
590 if (copy > len)
591 copy = len;
592 copied = copy_page_from_iter(page: skb_frag_page(frag),
593 offset: skb_frag_off(frag) + offset - start,
594 bytes: copy, i: from);
595 if (copied != copy)
596 goto fault;
597
598 if (!(len -= copy))
599 return 0;
600 offset += copy;
601 }
602 start = end;
603 }
604
605 skb_walk_frags(skb, frag_iter) {
606 int end;
607
608 WARN_ON(start > offset + len);
609
610 end = start + frag_iter->len;
611 if ((copy = end - offset) > 0) {
612 if (copy > len)
613 copy = len;
614 if (skb_copy_datagram_from_iter(skb: frag_iter,
615 offset: offset - start,
616 from, len: copy))
617 goto fault;
618 if ((len -= copy) == 0)
619 return 0;
620 offset += copy;
621 }
622 start = end;
623 }
624 if (!len)
625 return 0;
626
627fault:
628 return -EFAULT;
629}
630EXPORT_SYMBOL(skb_copy_datagram_from_iter);
631
632int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk,
633 struct sk_buff *skb, struct iov_iter *from,
634 size_t length)
635{
636 int frag;
637
638 if (msg && msg->msg_ubuf && msg->sg_from_iter)
639 return msg->sg_from_iter(sk, skb, from, length);
640
641 frag = skb_shinfo(skb)->nr_frags;
642
643 while (length && iov_iter_count(i: from)) {
644 struct page *head, *last_head = NULL;
645 struct page *pages[MAX_SKB_FRAGS];
646 int refs, order, n = 0;
647 size_t start;
648 ssize_t copied;
649 unsigned long truesize;
650
651 if (frag == MAX_SKB_FRAGS)
652 return -EMSGSIZE;
653
654 copied = iov_iter_get_pages2(i: from, pages, maxsize: length,
655 MAX_SKB_FRAGS - frag, start: &start);
656 if (copied < 0)
657 return -EFAULT;
658
659 length -= copied;
660
661 truesize = PAGE_ALIGN(copied + start);
662 skb->data_len += copied;
663 skb->len += copied;
664 skb->truesize += truesize;
665 if (sk && sk->sk_type == SOCK_STREAM) {
666 sk_wmem_queued_add(sk, val: truesize);
667 if (!skb_zcopy_pure(skb))
668 sk_mem_charge(sk, size: truesize);
669 } else {
670 refcount_add(i: truesize, r: &skb->sk->sk_wmem_alloc);
671 }
672
673 head = compound_head(pages[n]);
674 order = compound_order(page: head);
675
676 for (refs = 0; copied != 0; start = 0) {
677 int size = min_t(int, copied, PAGE_SIZE - start);
678
679 if (pages[n] - head > (1UL << order) - 1) {
680 head = compound_head(pages[n]);
681 order = compound_order(page: head);
682 }
683
684 start += (pages[n] - head) << PAGE_SHIFT;
685 copied -= size;
686 n++;
687 if (frag) {
688 skb_frag_t *last = &skb_shinfo(skb)->frags[frag - 1];
689
690 if (head == skb_frag_page(frag: last) &&
691 start == skb_frag_off(frag: last) + skb_frag_size(frag: last)) {
692 skb_frag_size_add(frag: last, delta: size);
693 /* We combined this page, we need to release
694 * a reference. Since compound pages refcount
695 * is shared among many pages, batch the refcount
696 * adjustments to limit false sharing.
697 */
698 last_head = head;
699 refs++;
700 continue;
701 }
702 }
703 if (refs) {
704 page_ref_sub(page: last_head, nr: refs);
705 refs = 0;
706 }
707 skb_fill_page_desc_noacc(skb, i: frag++, page: head, off: start, size);
708 }
709 if (refs)
710 page_ref_sub(page: last_head, nr: refs);
711 }
712 return 0;
713}
714EXPORT_SYMBOL(__zerocopy_sg_from_iter);
715
716/**
717 * zerocopy_sg_from_iter - Build a zerocopy datagram from an iov_iter
718 * @skb: buffer to copy
719 * @from: the source to copy from
720 *
721 * The function will first copy up to headlen, and then pin the userspace
722 * pages and build frags through them.
723 *
724 * Returns 0, -EFAULT or -EMSGSIZE.
725 */
726int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from)
727{
728 int copy = min_t(int, skb_headlen(skb), iov_iter_count(from));
729
730 /* copy up to skb headlen */
731 if (skb_copy_datagram_from_iter(skb, 0, from, copy))
732 return -EFAULT;
733
734 return __zerocopy_sg_from_iter(NULL, NULL, skb, from, ~0U);
735}
736EXPORT_SYMBOL(zerocopy_sg_from_iter);
737
738static __always_inline
739size_t copy_to_user_iter_csum(void __user *iter_to, size_t progress,
740 size_t len, void *from, void *priv2)
741{
742 __wsum next, *csum = priv2;
743
744 next = csum_and_copy_to_user(src: from + progress, dst: iter_to, len);
745 *csum = csum_block_add(csum: *csum, csum2: next, offset: progress);
746 return next ? 0 : len;
747}
748
749static __always_inline
750size_t memcpy_to_iter_csum(void *iter_to, size_t progress,
751 size_t len, void *from, void *priv2)
752{
753 __wsum *csum = priv2;
754 __wsum next = csum_partial_copy_nocheck(src: from, dst: iter_to, len);
755
756 *csum = csum_block_add(csum: *csum, csum2: next, offset: progress);
757 return 0;
758}
759
760struct csum_state {
761 __wsum csum;
762 size_t off;
763};
764
765static size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
766 struct iov_iter *i)
767{
768 struct csum_state *csstate = _csstate;
769 __wsum sum;
770
771 if (WARN_ON_ONCE(i->data_source))
772 return 0;
773 if (unlikely(iov_iter_is_discard(i))) {
774 // can't use csum_memcpy() for that one - data is not copied
775 csstate->csum = csum_block_add(csum: csstate->csum,
776 csum2: csum_partial(buff: addr, len: bytes, sum: 0),
777 offset: csstate->off);
778 csstate->off += bytes;
779 return bytes;
780 }
781
782 sum = csum_shift(sum: csstate->csum, offset: csstate->off);
783
784 bytes = iterate_and_advance2(iter: i, len: bytes, priv: (void *)addr, priv2: &sum,
785 ustep: copy_to_user_iter_csum,
786 step: memcpy_to_iter_csum);
787 csstate->csum = csum_shift(sum, offset: csstate->off);
788 csstate->off += bytes;
789 return bytes;
790}
791
792/**
793 * skb_copy_and_csum_datagram - Copy datagram to an iovec iterator
794 * and update a checksum.
795 * @skb: buffer to copy
796 * @offset: offset in the buffer to start copying from
797 * @to: iovec iterator to copy to
798 * @len: amount of data to copy from buffer to iovec
799 * @csump: checksum pointer
800 */
801static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
802 struct iov_iter *to, int len,
803 __wsum *csump)
804{
805 struct csum_state csdata = { .csum = *csump };
806 int ret;
807
808 ret = __skb_datagram_iter(skb, offset, to, len, fault_short: true,
809 cb: csum_and_copy_to_iter, data: &csdata);
810 if (ret)
811 return ret;
812
813 *csump = csdata.csum;
814 return 0;
815}
816
817/**
818 * skb_copy_and_csum_datagram_msg - Copy and checksum skb to user iovec.
819 * @skb: skbuff
820 * @hlen: hardware length
821 * @msg: destination
822 *
823 * Caller _must_ check that skb will fit to this iovec.
824 *
825 * Returns: 0 - success.
826 * -EINVAL - checksum failure.
827 * -EFAULT - fault during copy.
828 */
829int skb_copy_and_csum_datagram_msg(struct sk_buff *skb,
830 int hlen, struct msghdr *msg)
831{
832 __wsum csum;
833 int chunk = skb->len - hlen;
834
835 if (!chunk)
836 return 0;
837
838 if (msg_data_left(msg) < chunk) {
839 if (__skb_checksum_complete(skb))
840 return -EINVAL;
841 if (skb_copy_datagram_msg(from: skb, offset: hlen, msg, size: chunk))
842 goto fault;
843 } else {
844 csum = csum_partial(buff: skb->data, len: hlen, sum: skb->csum);
845 if (skb_copy_and_csum_datagram(skb, offset: hlen, to: &msg->msg_iter,
846 len: chunk, csump: &csum))
847 goto fault;
848
849 if (csum_fold(sum: csum)) {
850 iov_iter_revert(i: &msg->msg_iter, bytes: chunk);
851 return -EINVAL;
852 }
853
854 if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
855 !skb->csum_complete_sw)
856 netdev_rx_csum_fault(NULL, skb);
857 }
858 return 0;
859fault:
860 return -EFAULT;
861}
862EXPORT_SYMBOL(skb_copy_and_csum_datagram_msg);
863
864/**
865 * datagram_poll - generic datagram poll
866 * @file: file struct
867 * @sock: socket
868 * @wait: poll table
869 *
870 * Datagram poll: Again totally generic. This also handles
871 * sequenced packet sockets providing the socket receive queue
872 * is only ever holding data ready to receive.
873 *
874 * Note: when you *don't* use this routine for this protocol,
875 * and you use a different write policy from sock_writeable()
876 * then please supply your own write_space callback.
877 */
878__poll_t datagram_poll(struct file *file, struct socket *sock,
879 poll_table *wait)
880{
881 struct sock *sk = sock->sk;
882 __poll_t mask;
883 u8 shutdown;
884
885 sock_poll_wait(filp: file, sock, p: wait);
886 mask = 0;
887
888 /* exceptional events? */
889 if (READ_ONCE(sk->sk_err) ||
890 !skb_queue_empty_lockless(list: &sk->sk_error_queue))
891 mask |= EPOLLERR |
892 (sock_flag(sk, flag: SOCK_SELECT_ERR_QUEUE) ? EPOLLPRI : 0);
893
894 shutdown = READ_ONCE(sk->sk_shutdown);
895 if (shutdown & RCV_SHUTDOWN)
896 mask |= EPOLLRDHUP | EPOLLIN | EPOLLRDNORM;
897 if (shutdown == SHUTDOWN_MASK)
898 mask |= EPOLLHUP;
899
900 /* readable? */
901 if (!skb_queue_empty_lockless(list: &sk->sk_receive_queue))
902 mask |= EPOLLIN | EPOLLRDNORM;
903
904 /* Connection-based need to check for termination and startup */
905 if (connection_based(sk)) {
906 int state = READ_ONCE(sk->sk_state);
907
908 if (state == TCP_CLOSE)
909 mask |= EPOLLHUP;
910 /* connection hasn't started yet? */
911 if (state == TCP_SYN_SENT)
912 return mask;
913 }
914
915 /* writable? */
916 if (sock_writeable(sk))
917 mask |= EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND;
918 else
919 sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
920
921 return mask;
922}
923EXPORT_SYMBOL(datagram_poll);
924

source code of linux/net/core/datagram.c