/*
   *	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 <asm/uaccess.h>
  #include <asm/system.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 <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>

  
  /*
   *	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_t *wait, unsigned mode, int sync,
  				  void *key)
  {
  	unsigned long bits = (unsigned long)key;
  
  	/*
  	 * Avoid a wakeup if event not interesting for us
  	 */
  	if (bits && !(bits & (POLLIN | POLLERR)))
  		return 0;
  	return autoremove_wake_function(wait, mode, sync, key);
  }

  /*
   * Wait for a packet..
   */
  static int wait_for_packet(struct sock *sk, int *err, long *timeo_p)
  {
  	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 (!skb_queue_empty(&sk->sk_receive_queue))
  		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;
  }
  
  /**

   *	__skb_recv_datagram - Receive a datagram skbuff

   *	@sk: socket
   *	@flags: MSG_ flags

   *	@peeked: returns non-zero if this packet has been seen before

   *	@err: error code returned

   *
   *	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)
   *
   *	* 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_recv_datagram(struct sock *sk, unsigned flags,
  				    int *peeked, int *err)

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

  	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);

  
  	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)

  		 */

  		unsigned long cpu_flags;
  
  		spin_lock_irqsave(&sk->sk_receive_queue.lock, cpu_flags);
  		skb = skb_peek(&sk->sk_receive_queue);
  		if (skb) {
  			*peeked = skb->peeked;
  			if (flags & MSG_PEEK) {
  				skb->peeked = 1;

  				atomic_inc(&skb->users);

  			} else
  				__skb_unlink(skb, &sk->sk_receive_queue);
  		}
  		spin_unlock_irqrestore(&sk->sk_receive_queue.lock, cpu_flags);

  
  		if (skb)
  			return skb;
  
  		/* User doesn't want to wait */
  		error = -EAGAIN;
  		if (!timeo)
  			goto no_packet;
  
  	} while (!wait_for_packet(sk, err, &timeo));
  
  	return NULL;
  
  no_packet:
  	*err = error;
  	return NULL;
  }

  EXPORT_SYMBOL(__skb_recv_datagram);
  
  struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags,
  				  int noblock, int *err)
  {
  	int peeked;
  
  	return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
  				   &peeked, 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)
  {

  	bool slow;

  	if (likely(atomic_read(&skb->users) == 1))
  		smp_rmb();
  	else if (likely(!atomic_dec_and_test(&skb->users)))
  		return;

  	slow = lock_sock_fast(sk);

  	skb_orphan(skb);
  	sk_mem_reclaim_partial(sk);

  	unlock_sock_fast(sk, slow);

  	/* skb is now orphaned, can be freed outside of locked section */

  	trace_kfree_skb(skb, skb_free_datagram_locked);

  	__kfree_skb(skb);

  }
  EXPORT_SYMBOL(skb_free_datagram_locked);

  
  /**

   *	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 = 0;

  	if (flags & MSG_PEEK) {

  		err = -ENOENT;

  		spin_lock_bh(&sk->sk_receive_queue.lock);
  		if (skb == skb_peek(&sk->sk_receive_queue)) {
  			__skb_unlink(skb, &sk->sk_receive_queue);
  			atomic_dec(&skb->users);

  			err = 0;

  		}
  		spin_unlock_bh(&sk->sk_receive_queue.lock);
  	}

  	kfree_skb(skb);

  	atomic_inc(&sk->sk_drops);

  	sk_mem_reclaim_partial(sk);

  	return err;

  }

  EXPORT_SYMBOL(skb_kill_datagram);
  
  /**

   *	skb_copy_datagram_iovec - Copy a datagram to an iovec.

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

   *	@to: io vector to copy to

   *	@len: amount of data to copy from buffer to iovec

   *
   *	Note: the iovec is modified during the copy.
   */
  int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,
  			    struct iovec *to, int len)
  {

  	int start = skb_headlen(skb);
  	int i, copy = start - offset;

  	struct sk_buff *frag_iter;

  	trace_skb_copy_datagram_iovec(skb, len);

  	/* Copy header. */
  	if (copy > 0) {
  		if (copy > len)
  			copy = len;
  		if (memcpy_toiovec(to, skb->data + offset, 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) {
  			int err;
  			u8  *vaddr;

  			struct page *page = skb_frag_page(frag);

  
  			if (copy > len)
  				copy = len;

  			vaddr = kmap(page);

  			err = memcpy_toiovec(to, vaddr + frag->page_offset +
  					     offset - start, copy);

  			kunmap(page);

  			if (err)
  				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_iovec(frag_iter,
  						    offset - start,
  						    to, 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_iovec);

  /**

   *	skb_copy_datagram_const_iovec - Copy a datagram to an iovec.
   *	@skb: buffer to copy
   *	@offset: offset in the buffer to start copying from
   *	@to: io vector to copy to
   *	@to_offset: offset in the io vector to start copying to
   *	@len: amount of data to copy from buffer to iovec
   *
   *	Returns 0 or -EFAULT.
   *	Note: the iovec is not modified during the copy.
   */
  int skb_copy_datagram_const_iovec(const struct sk_buff *skb, int offset,
  				  const struct iovec *to, int to_offset,
  				  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 (memcpy_toiovecend(to, skb->data + offset, to_offset, copy))
  			goto fault;
  		if ((len -= copy) == 0)
  			return 0;
  		offset += copy;
  		to_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) {
  			int err;
  			u8  *vaddr;

  			struct page *page = skb_frag_page(frag);

  
  			if (copy > len)
  				copy = len;
  			vaddr = kmap(page);
  			err = memcpy_toiovecend(to, vaddr + frag->page_offset +
  						offset - start, to_offset, copy);
  			kunmap(page);
  			if (err)
  				goto fault;
  			if (!(len -= copy))
  				return 0;
  			offset += copy;
  			to_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_const_iovec(frag_iter,
  							  offset - start,
  							  to, to_offset,
  							  copy))
  				goto fault;
  			if ((len -= copy) == 0)
  				return 0;
  			offset += copy;
  			to_offset += copy;

  		}

  		start = end;

  	}
  	if (!len)
  		return 0;
  
  fault:
  	return -EFAULT;
  }
  EXPORT_SYMBOL(skb_copy_datagram_const_iovec);
  
  /**

   *	skb_copy_datagram_from_iovec - Copy a datagram from an iovec.
   *	@skb: buffer to copy
   *	@offset: offset in the buffer to start copying to
   *	@from: io vector to copy to

   *	@from_offset: offset in the io vector to start copying from

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

   *	Note: the iovec is not modified during the copy.

   */
  int skb_copy_datagram_from_iovec(struct sk_buff *skb, int offset,

  				 const struct iovec *from, int from_offset,
  				 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 (memcpy_fromiovecend(skb->data + offset, from, from_offset,
  					copy))

  			goto fault;
  		if ((len -= copy) == 0)
  			return 0;
  		offset += copy;

  		from_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) {
  			int err;
  			u8  *vaddr;

  			struct page *page = skb_frag_page(frag);

  
  			if (copy > len)
  				copy = len;
  			vaddr = kmap(page);

  			err = memcpy_fromiovecend(vaddr + frag->page_offset +
  						  offset - start,
  						  from, from_offset, copy);

  			kunmap(page);
  			if (err)
  				goto fault;
  
  			if (!(len -= copy))
  				return 0;
  			offset += copy;

  			from_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_iovec(frag_iter,
  							 offset - start,
  							 from,
  							 from_offset,
  							 copy))
  				goto fault;
  			if ((len -= copy) == 0)
  				return 0;
  			offset += copy;
  			from_offset += copy;

  		}

  		start = end;

  	}
  	if (!len)
  		return 0;
  
  fault:
  	return -EFAULT;
  }
  EXPORT_SYMBOL(skb_copy_datagram_from_iovec);

  static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
  				      u8 __user *to, int len,

  				      __wsum *csump)

  {

  	int start = skb_headlen(skb);

  	int i, copy = start - offset;

  	struct sk_buff *frag_iter;
  	int pos = 0;

  
  	/* Copy header. */
  	if (copy > 0) {
  		int err = 0;
  		if (copy > len)
  			copy = len;
  		*csump = csum_and_copy_to_user(skb->data + offset, to, copy,
  					       *csump, &err);
  		if (err)
  			goto fault;
  		if ((len -= copy) == 0)
  			return 0;
  		offset += copy;
  		to += copy;
  		pos = copy;
  	}
  
  	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) {

  			__wsum csum2;

  			int err = 0;
  			u8  *vaddr;

  			struct page *page = skb_frag_page(frag);

  
  			if (copy > len)
  				copy = len;
  			vaddr = kmap(page);
  			csum2 = csum_and_copy_to_user(vaddr +

  							frag->page_offset +
  							offset - start,

  						      to, copy, 0, &err);
  			kunmap(page);
  			if (err)
  				goto fault;
  			*csump = csum_block_add(*csump, csum2, pos);
  			if (!(len -= copy))
  				return 0;
  			offset += copy;
  			to += copy;
  			pos += 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) {
  			__wsum csum2 = 0;
  			if (copy > len)
  				copy = len;
  			if (skb_copy_and_csum_datagram(frag_iter,
  						       offset - start,
  						       to, copy,
  						       &csum2))
  				goto fault;
  			*csump = csum_block_add(*csump, csum2, pos);
  			if ((len -= copy) == 0)
  				return 0;
  			offset += copy;
  			to += copy;
  			pos += copy;

  		}

  		start = end;

  	}
  	if (!len)
  		return 0;
  
  fault:
  	return -EFAULT;
  }

  __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)

  {

  	__sum16 sum;

  	sum = csum_fold(skb_checksum(skb, 0, len, skb->csum));

  	if (likely(!sum)) {

  		if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))

  			netdev_rx_csum_fault(skb->dev);
  		skb->ip_summed = CHECKSUM_UNNECESSARY;
  	}
  	return sum;
  }

  EXPORT_SYMBOL(__skb_checksum_complete_head);
  
  __sum16 __skb_checksum_complete(struct sk_buff *skb)
  {
  	return __skb_checksum_complete_head(skb, skb->len);
  }

  EXPORT_SYMBOL(__skb_checksum_complete);

  /**
   *	skb_copy_and_csum_datagram_iovec - Copy and checkum skb to user iovec.

   *	@skb: skbuff
   *	@hlen: hardware length

   *	@iov: io vector

   *

   *	Caller _must_ check that skb will fit to this iovec.
   *
   *	Returns: 0       - success.
   *		 -EINVAL - checksum failure.
   *		 -EFAULT - fault during copy. Beware, in this case iovec
   *			   can be modified!
   */

  int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,

  				     int hlen, struct iovec *iov)
  {

  	__wsum csum;

  	int chunk = skb->len - hlen;

  	if (!chunk)
  		return 0;

  	/* Skip filled elements.
  	 * Pretty silly, look at memcpy_toiovec, though 8)
  	 */
  	while (!iov->iov_len)
  		iov++;
  
  	if (iov->iov_len < chunk) {

  		if (__skb_checksum_complete(skb))

  			goto csum_error;
  		if (skb_copy_datagram_iovec(skb, hlen, iov, chunk))
  			goto fault;
  	} else {
  		csum = csum_partial(skb->data, hlen, skb->csum);
  		if (skb_copy_and_csum_datagram(skb, hlen, iov->iov_base,
  					       chunk, &csum))
  			goto fault;

  		if (csum_fold(csum))

  			goto csum_error;

  		if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))

  			netdev_rx_csum_fault(skb->dev);

  		iov->iov_len -= chunk;
  		iov->iov_base += chunk;
  	}
  	return 0;
  csum_error:
  	return -EINVAL;
  fault:
  	return -EFAULT;
  }

  EXPORT_SYMBOL(skb_copy_and_csum_datagram_iovec);

  
  /**
   * 	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.
   */
  unsigned int datagram_poll(struct file *file, struct socket *sock,
  			   poll_table *wait)
  {
  	struct sock *sk = sock->sk;
  	unsigned int mask;

  	sock_poll_wait(file, sk_sleep(sk), wait);

  	mask = 0;
  
  	/* exceptional events? */
  	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
  		mask |= POLLERR;

  	if (sk->sk_shutdown & RCV_SHUTDOWN)

  		mask |= POLLRDHUP | POLLIN | POLLRDNORM;

  	if (sk->sk_shutdown == SHUTDOWN_MASK)
  		mask |= POLLHUP;
  
  	/* readable? */

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

  		mask |= POLLIN | POLLRDNORM;
  
  	/* Connection-based need to check for termination and startup */
  	if (connection_based(sk)) {
  		if (sk->sk_state == TCP_CLOSE)
  			mask |= POLLHUP;
  		/* connection hasn't started yet? */
  		if (sk->sk_state == TCP_SYN_SENT)
  			return mask;
  	}
  
  	/* writable? */
  	if (sock_writeable(sk))
  		mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
  	else
  		set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
  
  	return mask;
  }

  EXPORT_SYMBOL(datagram_poll);