// SPDX-License-Identifier: GPL-2.0

  /*
   *	SUCS NET3:
   *
   *	Generic datagram handling routines. These are generic for all
   *	protocols. Possibly a generic IP version on top of these would
   *	make sense. Not tonight however 8-).
   *	This is used because UDP, RAW, PACKET, DDP, IPX, AX.25 and
   *	NetROM layer all have identical poll code and mostly
   *	identical recvmsg() code. So we share it here. The poll was
   *	shared before but buried in udp.c so I moved it.
   *

   *	Authors:	Alan Cox <alan@lxorguk.ukuu.org.uk>. (datagram_poll() from old

   *						     udp.c code)
   *
   *	Fixes:
   *		Alan Cox	:	NULL return from skb_peek_copy()
   *					understood
   *		Alan Cox	:	Rewrote skb_read_datagram to avoid the
   *					skb_peek_copy stuff.
   *		Alan Cox	:	Added support for SOCK_SEQPACKET.
   *					IPX can no longer use the SO_TYPE hack
   *					but AX.25 now works right, and SPX is
   *					feasible.
   *		Alan Cox	:	Fixed write poll of non IP protocol
   *					crash.
   *		Florian  La Roche:	Changed for my new skbuff handling.
   *		Darryl Miles	:	Fixed non-blocking SOCK_SEQPACKET.
   *		Linus Torvalds	:	BSD semantic fixes.
   *		Alan Cox	:	Datagram iovec handling
   *		Darryl Miles	:	Fixed non-blocking SOCK_STREAM.
   *		Alan Cox	:	POSIXisms
   *		Pete Wyckoff    :       Unconnected accept() fix.
   *
   */
  
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/kernel.h>

  #include <linux/uaccess.h>

  #include <linux/mm.h>
  #include <linux/interrupt.h>
  #include <linux/errno.h>
  #include <linux/sched.h>
  #include <linux/inet.h>

  #include <linux/netdevice.h>
  #include <linux/rtnetlink.h>
  #include <linux/poll.h>
  #include <linux/highmem.h>

  #include <linux/spinlock.h>

  #include <linux/slab.h>

  #include <linux/pagemap.h>

  #include <linux/uio.h>

  #include <linux/indirect_call_wrapper.h>

  
  #include <net/protocol.h>
  #include <linux/skbuff.h>

  #include <net/checksum.h>
  #include <net/sock.h>
  #include <net/tcp_states.h>

  #include <trace/events/skb.h>

  #include <net/busy_poll.h>

  #include "datagram.h"

  /*
   *	Is a socket 'connection oriented' ?
   */
  static inline int connection_based(struct sock *sk)
  {
  	return sk->sk_type == SOCK_SEQPACKET || sk->sk_type == SOCK_STREAM;
  }

  static int receiver_wake_function(wait_queue_entry_t *wait, unsigned int mode, int sync,

  				  void *key)
  {

  	/*
  	 * Avoid a wakeup if event not interesting for us
  	 */

  	if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR)))

  		return 0;
  	return autoremove_wake_function(wait, mode, sync, key);
  }

  /*

   * Wait for the last received packet to be different from skb

   */

  int __skb_wait_for_more_packets(struct sock *sk, struct sk_buff_head *queue,
  				int *err, long *timeo_p,

  				const struct sk_buff *skb)

  {
  	int error;

  	DEFINE_WAIT_FUNC(wait, receiver_wake_function);

  	prepare_to_wait_exclusive(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

  
  	/* Socket errors? */
  	error = sock_error(sk);
  	if (error)
  		goto out_err;

  	if (READ_ONCE(queue->prev) != skb)

  		goto out;
  
  	/* Socket shut down? */
  	if (sk->sk_shutdown & RCV_SHUTDOWN)
  		goto out_noerr;
  
  	/* Sequenced packets can come disconnected.
  	 * If so we report the problem
  	 */
  	error = -ENOTCONN;
  	if (connection_based(sk) &&
  	    !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN))
  		goto out_err;
  
  	/* handle signals */
  	if (signal_pending(current))
  		goto interrupted;
  
  	error = 0;
  	*timeo_p = schedule_timeout(*timeo_p);
  out:

  	finish_wait(sk_sleep(sk), &wait);

  	return error;
  interrupted:
  	error = sock_intr_errno(*timeo_p);
  out_err:
  	*err = error;
  	goto out;
  out_noerr:
  	*err = 0;
  	error = 1;
  	goto out;
  }

  EXPORT_SYMBOL(__skb_wait_for_more_packets);

  static struct sk_buff *skb_set_peeked(struct sk_buff *skb)

  {
  	struct sk_buff *nskb;
  
  	if (skb->peeked)

  		return skb;

  
  	/* We have to unshare an skb before modifying it. */
  	if (!skb_shared(skb))
  		goto done;
  
  	nskb = skb_clone(skb, GFP_ATOMIC);
  	if (!nskb)

  		return ERR_PTR(-ENOMEM);

  
  	skb->prev->next = nskb;
  	skb->next->prev = nskb;
  	nskb->prev = skb->prev;
  	nskb->next = skb->next;
  
  	consume_skb(skb);
  	skb = nskb;
  
  done:
  	skb->peeked = 1;

  	return skb;

  }

  struct sk_buff *__skb_try_recv_from_queue(struct sock *sk,
  					  struct sk_buff_head *queue,
  					  unsigned int flags,

  					  int *off, int *err,

  					  struct sk_buff **last)
  {

  	bool peek_at_off = false;

  	struct sk_buff *skb;

  	int _off = 0;
  
  	if (unlikely(flags & MSG_PEEK && *off >= 0)) {
  		peek_at_off = true;
  		_off = *off;
  	}

  
  	*last = queue->prev;
  	skb_queue_walk(queue, skb) {
  		if (flags & MSG_PEEK) {

  			if (peek_at_off && _off >= skb->len &&
  			    (_off || skb->peeked)) {

  				_off -= skb->len;

  				continue;
  			}
  			if (!skb->len) {
  				skb = skb_set_peeked(skb);

  				if (IS_ERR(skb)) {

  					*err = PTR_ERR(skb);

  					return NULL;

  				}
  			}

  			refcount_inc(&skb->users);

  		} else {
  			__skb_unlink(skb, queue);

  		}

  		*off = _off;

  		return skb;
  	}
  	return NULL;
  }

  /**

   *	__skb_try_recv_datagram - Receive a datagram skbuff

   *	@sk: socket

   *	@queue: socket queue from which to receive

   *	@flags: MSG\_ flags

   *	@off: an offset in bytes to peek skb from. Returns an offset
   *	      within an skb where data actually starts

   *	@err: error code returned

   *	@last: set to last peeked message to inform the wait function
   *	       what to look for when peeking

   *
   *	Get a datagram skbuff, understands the peeking, nonblocking wakeups
   *	and possible races. This replaces identical code in packet, raw and
   *	udp, as well as the IPX AX.25 and Appletalk. It also finally fixes
   *	the long standing peek and read race for datagram sockets. If you
   *	alter this routine remember it must be re-entrant.
   *

   *	This function will lock the socket if a skb is returned, so
   *	the caller needs to unlock the socket in that case (usually by

   *	calling skb_free_datagram). Returns NULL with @err set to

   *	-EAGAIN if no data was available or to some other value if an
   *	error was detected.

   *
   *	* It does not lock socket since today. This function is
   *	* free of race conditions. This measure should/can improve
   *	* significantly datagram socket latencies at high loads,
   *	* when data copying to user space takes lots of time.
   *	* (BTW I've just killed the last cli() in IP/IPv6/core/netlink/packet
   *	*  8) Great win.)
   *	*			                    --ANK (980729)
   *
   *	The order of the tests when we find no data waiting are specified
   *	quite explicitly by POSIX 1003.1g, don't change them without having
   *	the standard around please.
   */

  struct sk_buff *__skb_try_recv_datagram(struct sock *sk,
  					struct sk_buff_head *queue,

  					unsigned int flags, int *off, int *err,

  					struct sk_buff **last)

  {

  	struct sk_buff *skb;

  	unsigned long cpu_flags;

  	/*
  	 * Caller is allowed not to check sk->sk_err before skb_recv_datagram()
  	 */
  	int error = sock_error(sk);
  
  	if (error)
  		goto no_packet;

  	do {
  		/* Again only user level code calls this function, so nothing
  		 * interrupt level will suddenly eat the receive_queue.
  		 *
  		 * Look at current nfs client by the way...

  		 * However, this function was correct in any case. 8)

  		 */

  		spin_lock_irqsave(&queue->lock, cpu_flags);

  		skb = __skb_try_recv_from_queue(sk, queue, flags, off, &error,
  						last);

  		spin_unlock_irqrestore(&queue->lock, cpu_flags);

  		if (error)
  			goto no_packet;

  		if (skb)
  			return skb;

  
  		if (!sk_can_busy_loop(sk))
  			break;
  
  		sk_busy_loop(sk, flags & MSG_DONTWAIT);

  	} while (READ_ONCE(queue->prev) != *last);

  	error = -EAGAIN;

  no_packet:
  	*err = error;
  	return NULL;
  }
  EXPORT_SYMBOL(__skb_try_recv_datagram);

  struct sk_buff *__skb_recv_datagram(struct sock *sk,
  				    struct sk_buff_head *sk_queue,

  				    unsigned int flags, int *off, int *err)

  {
  	struct sk_buff *skb, *last;
  	long timeo;

  	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
  
  	do {

  		skb = __skb_try_recv_datagram(sk, sk_queue, flags, off, err,
  					      &last);

  		if (skb)
  			return skb;

  		if (*err != -EAGAIN)

  			break;
  	} while (timeo &&

  		 !__skb_wait_for_more_packets(sk, sk_queue, err,
  					      &timeo, last));

  	return NULL;
  }

  EXPORT_SYMBOL(__skb_recv_datagram);

  struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags,

  				  int noblock, int *err)
  {

  	int off = 0;

  	return __skb_recv_datagram(sk, &sk->sk_receive_queue,
  				   flags | (noblock ? MSG_DONTWAIT : 0),

  				   &off, err);

  }

  EXPORT_SYMBOL(skb_recv_datagram);

  
  void skb_free_datagram(struct sock *sk, struct sk_buff *skb)
  {

  	consume_skb(skb);

  	sk_mem_reclaim_partial(sk);

  }

  EXPORT_SYMBOL(skb_free_datagram);

  void __skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb, int len)

  {

  	bool slow;

  	if (!skb_unref(skb)) {

  		sk_peek_offset_bwd(sk, len);

  		return;

  	}

  	slow = lock_sock_fast(sk);

  	sk_peek_offset_bwd(sk, len);

  	skb_orphan(skb);
  	sk_mem_reclaim_partial(sk);

  	unlock_sock_fast(sk, slow);

  	/* skb is now orphaned, can be freed outside of locked section */
  	__kfree_skb(skb);

  }

  EXPORT_SYMBOL(__skb_free_datagram_locked);

  int __sk_queue_drop_skb(struct sock *sk, struct sk_buff_head *sk_queue,
  			struct sk_buff *skb, unsigned int flags,

  			void (*destructor)(struct sock *sk,
  					   struct sk_buff *skb))

  {
  	int err = 0;
  
  	if (flags & MSG_PEEK) {
  		err = -ENOENT;

  		spin_lock_bh(&sk_queue->lock);

  		if (skb->next) {

  			__skb_unlink(skb, sk_queue);

  			refcount_dec(&skb->users);

  			if (destructor)
  				destructor(sk, skb);

  			err = 0;
  		}

  		spin_unlock_bh(&sk_queue->lock);

  	}
  
  	atomic_inc(&sk->sk_drops);
  	return err;
  }
  EXPORT_SYMBOL(__sk_queue_drop_skb);

  /**

   *	skb_kill_datagram - Free a datagram skbuff forcibly
   *	@sk: socket
   *	@skb: datagram skbuff

   *	@flags: MSG\_ flags

   *
   *	This function frees a datagram skbuff that was received by
   *	skb_recv_datagram.  The flags argument must match the one
   *	used for skb_recv_datagram.
   *
   *	If the MSG_PEEK flag is set, and the packet is still on the
   *	receive queue of the socket, it will be taken off the queue
   *	before it is freed.
   *
   *	This function currently only disables BH when acquiring the
   *	sk_receive_queue lock.  Therefore it must not be used in a
   *	context where that lock is acquired in an IRQ context.

   *
   *	It returns 0 if the packet was removed by us.

   */

  int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)

  {

  	int err = __sk_queue_drop_skb(sk, &sk->sk_receive_queue, skb, flags,
  				      NULL);

  	kfree_skb(skb);
  	sk_mem_reclaim_partial(sk);

  	return err;

  }

  EXPORT_SYMBOL(skb_kill_datagram);

  INDIRECT_CALLABLE_DECLARE(static size_t simple_copy_to_iter(const void *addr,
  						size_t bytes,
  						void *data __always_unused,
  						struct iov_iter *i));

  static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
  			       struct iov_iter *to, int len, bool fault_short,
  			       size_t (*cb)(const void *, size_t, void *,
  					    struct iov_iter *), void *data)

  {
  	int start = skb_headlen(skb);

  	int i, copy = start - offset, start_off = offset, n;

  	struct sk_buff *frag_iter;

  	/* Copy header. */
  	if (copy > 0) {
  		if (copy > len)
  			copy = len;

  		n = INDIRECT_CALL_1(cb, simple_copy_to_iter,
  				    skb->data + offset, copy, data, to);

  		offset += n;
  		if (n != copy)

  			goto short_copy;
  		if ((len -= copy) == 0)
  			return 0;

  	}
  
  	/* Copy paged appendix. Hmm... why does this look so complicated? */
  	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
  		int end;
  		const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
  
  		WARN_ON(start > offset + len);
  
  		end = start + skb_frag_size(frag);
  		if ((copy = end - offset) > 0) {

  			struct page *page = skb_frag_page(frag);
  			u8 *vaddr = kmap(page);

  			if (copy > len)
  				copy = len;

  			n = INDIRECT_CALL_1(cb, simple_copy_to_iter,
  					vaddr + skb_frag_off(frag) + offset - start,
  					copy, data, to);

  			kunmap(page);

  			offset += n;
  			if (n != copy)

  				goto short_copy;
  			if (!(len -= copy))
  				return 0;

  		}
  		start = end;
  	}
  
  	skb_walk_frags(skb, frag_iter) {
  		int end;
  
  		WARN_ON(start > offset + len);
  
  		end = start + frag_iter->len;
  		if ((copy = end - offset) > 0) {
  			if (copy > len)
  				copy = len;

  			if (__skb_datagram_iter(frag_iter, offset - start,

  						to, copy, fault_short, cb, data))

  				goto fault;
  			if ((len -= copy) == 0)
  				return 0;
  			offset += copy;
  		}
  		start = end;
  	}
  	if (!len)
  		return 0;
  
  	/* This is not really a user copy fault, but rather someone
  	 * gave us a bogus length on the skb.  We should probably
  	 * print a warning here as it may indicate a kernel bug.
  	 */
  
  fault:

  	iov_iter_revert(to, offset - start_off);

  	return -EFAULT;
  
  short_copy:

  	if (fault_short || iov_iter_count(to))

  		goto fault;
  
  	return 0;
  }

  /**
   *	skb_copy_and_hash_datagram_iter - Copy datagram to an iovec iterator
   *          and update a hash.
   *	@skb: buffer to copy
   *	@offset: offset in the buffer to start copying from
   *	@to: iovec iterator to copy to
   *	@len: amount of data to copy from buffer to iovec
   *      @hash: hash request to update
   */
  int skb_copy_and_hash_datagram_iter(const struct sk_buff *skb, int offset,
  			   struct iov_iter *to, int len,
  			   struct ahash_request *hash)
  {
  	return __skb_datagram_iter(skb, offset, to, len, true,
  			hash_and_copy_to_iter, hash);
  }
  EXPORT_SYMBOL(skb_copy_and_hash_datagram_iter);

  static size_t simple_copy_to_iter(const void *addr, size_t bytes,
  		void *data __always_unused, struct iov_iter *i)
  {
  	return copy_to_iter(addr, bytes, i);
  }
  
  /**
   *	skb_copy_datagram_iter - Copy a datagram to an iovec iterator.
   *	@skb: buffer to copy
   *	@offset: offset in the buffer to start copying from
   *	@to: iovec iterator to copy to
   *	@len: amount of data to copy from buffer to iovec
   */
  int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
  			   struct iov_iter *to, int len)
  {
  	trace_skb_copy_datagram_iovec(skb, len);
  	return __skb_datagram_iter(skb, offset, to, len, false,
  			simple_copy_to_iter, NULL);
  }

  EXPORT_SYMBOL(skb_copy_datagram_iter);
  
  /**

   *	skb_copy_datagram_from_iter - Copy a datagram from an iov_iter.

   *	@skb: buffer to copy
   *	@offset: offset in the buffer to start copying to

   *	@from: the copy source

   *	@len: amount of data to copy to buffer from iovec
   *
   *	Returns 0 or -EFAULT.

   */

  int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
  				 struct iov_iter *from,
  				 int len)
  {
  	int start = skb_headlen(skb);
  	int i, copy = start - offset;
  	struct sk_buff *frag_iter;
  
  	/* Copy header. */
  	if (copy > 0) {
  		if (copy > len)
  			copy = len;
  		if (copy_from_iter(skb->data + offset, copy, from) != copy)
  			goto fault;
  		if ((len -= copy) == 0)
  			return 0;
  		offset += copy;
  	}
  
  	/* Copy paged appendix. Hmm... why does this look so complicated? */
  	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
  		int end;
  		const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
  
  		WARN_ON(start > offset + len);
  
  		end = start + skb_frag_size(frag);
  		if ((copy = end - offset) > 0) {
  			size_t copied;
  
  			if (copy > len)
  				copy = len;
  			copied = copy_page_from_iter(skb_frag_page(frag),

  					  skb_frag_off(frag) + offset - start,

  					  copy, from);
  			if (copied != copy)
  				goto fault;
  
  			if (!(len -= copy))
  				return 0;
  			offset += copy;
  		}
  		start = end;
  	}
  
  	skb_walk_frags(skb, frag_iter) {
  		int end;
  
  		WARN_ON(start > offset + len);
  
  		end = start + frag_iter->len;
  		if ((copy = end - offset) > 0) {
  			if (copy > len)
  				copy = len;
  			if (skb_copy_datagram_from_iter(frag_iter,
  							offset - start,
  							from, copy))
  				goto fault;
  			if ((len -= copy) == 0)
  				return 0;
  			offset += copy;
  		}
  		start = end;
  	}
  	if (!len)
  		return 0;
  
  fault:
  	return -EFAULT;
  }
  EXPORT_SYMBOL(skb_copy_datagram_from_iter);

  int __zerocopy_sg_from_iter(struct sock *sk, struct sk_buff *skb,
  			    struct iov_iter *from, size_t length)

  {

  	int frag = skb_shinfo(skb)->nr_frags;

  	while (length && iov_iter_count(from)) {

  		struct page *pages[MAX_SKB_FRAGS];

  		struct page *last_head = NULL;

  		size_t start;
  		ssize_t copied;
  		unsigned long truesize;

  		int refs, n = 0;

  
  		if (frag == MAX_SKB_FRAGS)
  			return -EMSGSIZE;

  		copied = iov_iter_get_pages(from, pages, length,

  					    MAX_SKB_FRAGS - frag, &start);
  		if (copied < 0)
  			return -EFAULT;
  
  		iov_iter_advance(from, copied);

  		length -= copied;

  
  		truesize = PAGE_ALIGN(copied + start);
  		skb->data_len += copied;
  		skb->len += copied;
  		skb->truesize += truesize;

  		if (sk && sk->sk_type == SOCK_STREAM) {

  			sk_wmem_queued_add(sk, truesize);

  			sk_mem_charge(sk, truesize);
  		} else {
  			refcount_add(truesize, &skb->sk->sk_wmem_alloc);
  		}

  		for (refs = 0; copied != 0; start = 0) {

  			int size = min_t(int, copied, PAGE_SIZE - start);

  			struct page *head = compound_head(pages[n]);
  
  			start += (pages[n] - head) << PAGE_SHIFT;

  			copied -= size;
  			n++;

  			if (frag) {
  				skb_frag_t *last = &skb_shinfo(skb)->frags[frag - 1];
  
  				if (head == skb_frag_page(last) &&
  				    start == skb_frag_off(last) + skb_frag_size(last)) {
  					skb_frag_size_add(last, size);
  					/* We combined this page, we need to release
  					 * a reference. Since compound pages refcount
  					 * is shared among many pages, batch the refcount
  					 * adjustments to limit false sharing.
  					 */
  					last_head = head;
  					refs++;
  					continue;
  				}
  			}
  			if (refs) {
  				page_ref_sub(last_head, refs);
  				refs = 0;
  			}
  			skb_fill_page_desc(skb, frag++, head, start, size);

  		}

  		if (refs)
  			page_ref_sub(last_head, refs);

  	}
  	return 0;
  }

  EXPORT_SYMBOL(__zerocopy_sg_from_iter);
  
  /**
   *	zerocopy_sg_from_iter - Build a zerocopy datagram from an iov_iter
   *	@skb: buffer to copy
   *	@from: the source to copy from
   *
   *	The function will first copy up to headlen, and then pin the userspace
   *	pages and build frags through them.
   *
   *	Returns 0, -EFAULT or -EMSGSIZE.
   */
  int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from)
  {
  	int copy = min_t(int, skb_headlen(skb), iov_iter_count(from));
  
  	/* copy up to skb headlen */
  	if (skb_copy_datagram_from_iter(skb, 0, from, copy))
  		return -EFAULT;
  
  	return __zerocopy_sg_from_iter(NULL, skb, from, ~0U);
  }

  EXPORT_SYMBOL(zerocopy_sg_from_iter);

  /**
   *	skb_copy_and_csum_datagram_iter - Copy datagram to an iovec iterator
   *          and update a checksum.
   *	@skb: buffer to copy
   *	@offset: offset in the buffer to start copying from
   *	@to: iovec iterator to copy to
   *	@len: amount of data to copy from buffer to iovec
   *      @csump: checksum pointer
   */

  static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,

  				      struct iov_iter *to, int len,

  				      __wsum *csump)

  {

  	return __skb_datagram_iter(skb, offset, to, len, true,
  			csum_and_copy_to_iter, csump);

  }
  
  /**

   *	skb_copy_and_csum_datagram_msg - Copy and checksum skb to user iovec.

   *	@skb: skbuff
   *	@hlen: hardware length

   *	@msg: destination

   *

   *	Caller _must_ check that skb will fit to this iovec.
   *
   *	Returns: 0       - success.
   *		 -EINVAL - checksum failure.

   *		 -EFAULT - fault during copy.

   */

  int skb_copy_and_csum_datagram_msg(struct sk_buff *skb,
  				   int hlen, struct msghdr *msg)

  {

  	__wsum csum;

  	int chunk = skb->len - hlen;

  	if (!chunk)
  		return 0;

  	if (msg_data_left(msg) < chunk) {

  		if (__skb_checksum_complete(skb))

  			return -EINVAL;

  		if (skb_copy_datagram_msg(skb, hlen, msg, chunk))

  			goto fault;
  	} else {
  		csum = csum_partial(skb->data, hlen, skb->csum);

  		if (skb_copy_and_csum_datagram(skb, hlen, &msg->msg_iter,

  					       chunk, &csum))
  			goto fault;

  
  		if (csum_fold(csum)) {
  			iov_iter_revert(&msg->msg_iter, chunk);
  			return -EINVAL;
  		}

  		if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
  		    !skb->csum_complete_sw)

  			netdev_rx_csum_fault(NULL, skb);

  	}
  	return 0;

  fault:
  	return -EFAULT;
  }

  EXPORT_SYMBOL(skb_copy_and_csum_datagram_msg);

  
  /**
   * 	datagram_poll - generic datagram poll

   *	@file: file struct

   *	@sock: socket

   *	@wait: poll table

   *
   *	Datagram poll: Again totally generic. This also handles
   *	sequenced packet sockets providing the socket receive queue
   *	is only ever holding data ready to receive.
   *

   *	Note: when you *don't* use this routine for this protocol,

   *	and you use a different write policy from sock_writeable()
   *	then please supply your own write_space callback.
   */

  __poll_t datagram_poll(struct file *file, struct socket *sock,
  			   poll_table *wait)

  {
  	struct sock *sk = sock->sk;

  	__poll_t mask;

  	sock_poll_wait(file, sock, wait);

  	mask = 0;

  
  	/* exceptional events? */

  	if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue))

  		mask |= EPOLLERR |
  			(sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? EPOLLPRI : 0);

  	if (sk->sk_shutdown & RCV_SHUTDOWN)

  		mask |= EPOLLRDHUP | EPOLLIN | EPOLLRDNORM;

  	if (sk->sk_shutdown == SHUTDOWN_MASK)

  		mask |= EPOLLHUP;

  
  	/* readable? */

  	if (!skb_queue_empty_lockless(&sk->sk_receive_queue))

  		mask |= EPOLLIN | EPOLLRDNORM;

  
  	/* Connection-based need to check for termination and startup */
  	if (connection_based(sk)) {
  		if (sk->sk_state == TCP_CLOSE)

  			mask |= EPOLLHUP;

  		/* connection hasn't started yet? */
  		if (sk->sk_state == TCP_SYN_SENT)
  			return mask;
  	}
  
  	/* writable? */
  	if (sock_writeable(sk))

  		mask |= EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND;

  	else

  		sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);

  
  	return mask;
  }

  EXPORT_SYMBOL(datagram_poll);