Initial file dump from open source releaseHEADmaster

1 files changed, 787 insertions, 0 deletions

diff --git a/net/core/datagram.c b/net/core/datagram.c
new file mode 100644
index 00000000..b71423db
--- /dev/null
+++ b/net/core/datagram.c
@@ -0,0 +1,787 @@
+/*
+ *	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 <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 int 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 the last received packet to be different from skb
+ */
+static int wait_for_more_packets(struct sock *sk, 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 (sk->sk_receive_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;
+}
+
+/**
+ *	__skb_recv_datagram - Receive a datagram skbuff
+ *	@sk: socket
+ *	@flags: MSG_ flags
+ *	@peeked: returns non-zero if this packet has been seen before
+ *	@off: an offset in bytes to peek skb from. Returns an offset
+ *	      within an skb where data actually starts
+ *	@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 int flags,
+				    int *peeked, int *off, int *err)
+{
+	struct sk_buff *skb, *last;
+	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;
+		struct sk_buff_head *queue = &sk->sk_receive_queue;
+		int _off = *off;
+
+		last = (struct sk_buff *)queue;
+		spin_lock_irqsave(&queue->lock, cpu_flags);
+		skb_queue_walk(queue, skb) {
+			last = skb;
+			*peeked = skb->peeked;
+			if (flags & MSG_PEEK) {
+				if (_off >= skb->len && (skb->len || _off ||
+							 skb->peeked)) {
+					_off -= skb->len;
+					continue;
+				}
+				skb->peeked = 1;
+				atomic_inc(&skb->users);
+			} else
+				__skb_unlink(skb, queue);
+
+			spin_unlock_irqrestore(&queue->lock, cpu_flags);
+			*off = _off;
+			return skb;
+		}
+		spin_unlock_irqrestore(&queue->lock, cpu_flags);
+
+		/* User doesn't want to wait */
+		error = -EAGAIN;
+		if (!timeo)
+			goto no_packet;
+
+	} while (!wait_for_more_packets(sk, err, &timeo, last));
+
+	return NULL;
+
+no_packet:
+	*err = error;
+	return NULL;
+}
+EXPORT_SYMBOL(__skb_recv_datagram);
+
+struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags,
+				  int noblock, int *err)
+{
+	int peeked, off = 0;
+
+	return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
+				   &peeked, &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)
+{
+	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 */
+	__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 |
+			(sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0);
+
+	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);