# net/core/datagram.c

#   - remove spurious spaces and tabs at end of lines
#   - make sure if, while, for, switch has a space before the opening '('
#   - make sure no line has more than 80 chars
#   - move initializations to the declaration line where possible
#   - bitwise, logical and arithmetic operators have spaces before and after,
#     improving readability of complex expressions
#   - use named initializations in structs
#   - transform existing function comments into kernel-doc style
#   - minor size optimizations
# 
# Sizes:
# Before:
#    text    data     bss     dec     hex filename
#    2736       0       0    2736     ab0 net/core/datagram.o
# After:
#    2720       0       0    2720     aa0 net/core/datagram.o

net/core/datagram.c

 /*
  *	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.
+ *	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@redhat.com>. (datagram_poll() from old udp.c code)
+ *	Authors:	Alan Cox <alan@redhat.com>. (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.
+ *		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.
@@ -48,18 +57,15 @@
 /*
  *	Is a socket 'connection oriented' ?
  */
- 
 static inline int connection_based(struct sock *sk)
 {
-	return (sk->type==SOCK_SEQPACKET || sk->type==SOCK_STREAM);
+	return sk->type == SOCK_SEQPACKET || sk->type == SOCK_STREAM;
 }
 
-
 /*
  * Wait for a packet..
  */
-
-static int wait_for_packet(struct sock * sk, int *err, long *timeo_p)
+static int wait_for_packet(struct sock *sk, int *err, long *timeo_p)
 {
 	int error;
 
@@ -74,51 +80,57 @@ static int wait_for_packet(struct sock * sk, int *err, long *timeo_p)
 		goto out_err;
 
 	if (!skb_queue_empty(&sk->receive_queue))
-		goto ready;
+		goto out;
 
 	/* Socket shut down? */
 	if (sk->shutdown & RCV_SHUTDOWN)
 		goto out_noerr;
 
-	/* Sequenced packets can come disconnected. If so we report the problem */
+	/* Sequenced packets can come disconnected.
+	 * If so we report the problem
+	 */
 	error = -ENOTCONN;
-	if(connection_based(sk) && !(sk->state==TCP_ESTABLISHED || sk->state==TCP_LISTEN))
+	if (connection_based(sk) && !(sk->state == TCP_ESTABLISHED ||
+				      sk->state == TCP_LISTEN))
 		goto out_err;
 
 	/* handle signals */
 	if (signal_pending(current))
 		goto interrupted;
 
+	error = 0;
 	*timeo_p = schedule_timeout(*timeo_p);
-
-ready:
+out:
 	current->state = TASK_RUNNING;
 	remove_wait_queue(sk->sleep, &wait);
-	return 0;
-
+	return error;
 interrupted:
 	error = sock_intr_errno(*timeo_p);
 out_err:
 	*err = error;
-out:
-	current->state = TASK_RUNNING;
-	remove_wait_queue(sk->sleep, &wait);
-	return error;
+	goto out;
 out_noerr:
 	*err = 0;
 	error = 1;
 	goto out;
 }
 
-/*
- *	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.
+/**
+ *	skb_recv_datagram - Receive a datagram skbuff
+ *	@sk - socket
+ *	@flags - MSG_ flags
+ *	@noblock - blocking operation?
+ *	@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)
+ *	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
@@ -132,36 +144,35 @@ static int wait_for_packet(struct sock * sk, int *err, long *timeo_p)
  *	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 noblock, int *err)
+struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags,
+				  int noblock, int *err)
 {
-	int error;
 	struct sk_buff *skb;
 	long timeo;
-
 	/* Caller is allowed not to check sk->err before skb_recv_datagram() */
-	error = sock_error(sk);
+	int error = sock_error(sk);
+
 	if (error)
 		goto no_packet;
 
 	timeo = sock_rcvtimeo(sk, noblock);
 
 	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 corrent in any case. 8)
+		/* 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 corrent in any case. 8)
 		 */
-		if (flags & MSG_PEEK)
-		{
+		if (flags & MSG_PEEK) {
 			unsigned long cpu_flags;
 
 			spin_lock_irqsave(&sk->receive_queue.lock, cpu_flags);
 			skb = skb_peek(&sk->receive_queue);
-			if(skb!=NULL)
+			if (skb)
 				atomic_inc(&skb->users);
-			spin_unlock_irqrestore(&sk->receive_queue.lock, cpu_flags);
+			spin_unlock_irqrestore(&sk->receive_queue.lock,
+					       cpu_flags);
 		} else
 			skb = skb_dequeue(&sk->receive_queue);
 
@@ -173,7 +184,7 @@ struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock,
 		if (!timeo)
 			goto no_packet;
 
-	} while (wait_for_packet(sk, err, &timeo) == 0);
+	} while (!wait_for_packet(sk, err, &timeo));
 
 	return NULL;
 
@@ -182,7 +193,7 @@ struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock,
 	return NULL;
 }
 
-void skb_free_datagram(struct sock * sk, struct sk_buff *skb)
+void skb_free_datagram(struct sock *sk, struct sk_buff *skb)
 {
 	kfree_skb(skb);
 }
@@ -190,26 +201,33 @@ void skb_free_datagram(struct sock * sk, struct sk_buff *skb)
 /*
  *	Copy a datagram to a linear buffer.
  */
-
 int skb_copy_datagram(const struct sk_buff *skb, int offset, char *to, int size)
 {
-	struct iovec iov = { to, size };
+	struct iovec iov = {
+		iov_base: to,
+		iov_len:  size,
+	};
 
 	return skb_copy_datagram_iovec(skb, offset, &iov, size);
 }
 
-/*
- *	Copy a datagram to an iovec.
+/**
+ *	skb_copy_datagram_iovec - Copy a datagram to an iovec.
+ *	@skb - buffer to copy
+ *	@offset - offset in the buffer to start copying from
+ *	@iovec - 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 skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,
+			    struct iovec *to, int len)
 {
-	int i, copy;
 	int start = skb->len - skb->data_len;
+	int i, copy = start - offset;
 
 	/* Copy header. */
-	if ((copy = start-offset) > 0) {
+	if (copy > 0) {
 		if (copy > len)
 			copy = len;
 		if (memcpy_toiovec(to, skb->data + offset, copy))
@@ -220,13 +238,13 @@ int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset, struct iovec
 	}
 
 	/* Copy paged appendix. Hmm... why does this look so complicated? */
-	for (i=0; i<skb_shinfo(skb)->nr_frags; i++) {
+	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		int end;
 
-		BUG_TRAP(start <= offset+len);
+		BUG_TRAP(start <= offset + len);
 
 		end = start + skb_shinfo(skb)->frags[i].size;
-		if ((copy = end-offset) > 0) {
+		if ((copy = end - offset) > 0) {
 			int err;
 			u8  *vaddr;
 			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
@@ -236,7 +254,7 @@ int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset, struct iovec
 				copy = len;
 			vaddr = kmap(page);
 			err = memcpy_toiovec(to, vaddr + frag->page_offset +
-					     offset-start, copy);
+					     offset - start, copy);
 			kunmap(page);
 			if (err)
 				goto fault;
@@ -248,18 +266,20 @@ int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset, struct iovec
 	}
 
 	if (skb_shinfo(skb)->frag_list) {
-		struct sk_buff *list;
+		struct sk_buff *list = skb_shinfo(skb)->frag_list;
 
-		for (list = skb_shinfo(skb)->frag_list; list; list=list->next) {
+		for (; list; list = list->next) {
 			int end;
 
-			BUG_TRAP(start <= offset+len);
+			BUG_TRAP(start <= offset + len);
 
 			end = start + list->len;
-			if ((copy = end-offset) > 0) {
+			if ((copy = end - offset) > 0) {
 				if (copy > len)
 					copy = len;
-				if (skb_copy_datagram_iovec(list, offset-start, to, copy))
+				if (skb_copy_datagram_iovec(list,
+							    offset - start,
+							    to, copy))
 					goto fault;
 				if ((len -= copy) == 0)
 					return 0;
@@ -268,25 +288,27 @@ int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset, struct iovec
 			start = end;
 		}
 	}
-	if (len == 0)
+	if (!len)
 		return 0;
 
 fault:
 	return -EFAULT;
 }
 
-int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, u8 *to, int len, unsigned int *csump)
+int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
+			       u8 *to, int len, unsigned int *csump)
 {
-	int i, copy;
 	int start = skb->len - skb->data_len;
 	int pos = 0;
+	int i, copy = start - offset;
 
 	/* Copy header. */
-	if ((copy = start-offset) > 0) {
+	if (copy > 0) {
 		int err = 0;
 		if (copy > len)
 			copy = len;
-		*csump = csum_and_copy_to_user(skb->data+offset, to, copy, *csump, &err);
+		*csump = csum_and_copy_to_user(skb->data + offset, to, copy,
+					       *csump, &err);
 		if (err)
 			goto fault;
 		if ((len -= copy) == 0)
@@ -296,13 +318,13 @@ int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, u8 *to, in
 		pos = copy;
 	}
 
-	for (i=0; i<skb_shinfo(skb)->nr_frags; i++) {
+	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		int end;
 
-		BUG_TRAP(start <= offset+len);
+		BUG_TRAP(start <= offset + len);
 
 		end = start + skb_shinfo(skb)->frags[i].size;
-		if ((copy = end-offset) > 0) {
+		if ((copy = end - offset) > 0) {
 			unsigned int csum2;
 			int err = 0;
 			u8  *vaddr;
@@ -312,8 +334,10 @@ int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, u8 *to, in
 			if (copy > len)
 				copy = len;
 			vaddr = kmap(page);
-			csum2 = csum_and_copy_to_user(vaddr + frag->page_offset +
-						      offset-start, to, copy, 0, &err);
+			csum2 = csum_and_copy_to_user(vaddr +
+							frag->page_offset +
+							offset - start,
+						      to, copy, 0, &err);
 			kunmap(page);
 			if (err)
 				goto fault;
@@ -328,19 +352,22 @@ int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, u8 *to, in
 	}
 
 	if (skb_shinfo(skb)->frag_list) {
-		struct sk_buff *list;
+		struct sk_buff *list = skb_shinfo(skb)->frag_list;
 
-		for (list = skb_shinfo(skb)->frag_list; list; list=list->next) {
+		for (; list; list=list->next) {
 			int end;
 
-			BUG_TRAP(start <= offset+len);
+			BUG_TRAP(start <= offset + len);
 
 			end = start + list->len;
-			if ((copy = end-offset) > 0) {
+			if ((copy = end - offset) > 0) {
 				unsigned int csum2 = 0;
 				if (copy > len)
 					copy = len;
-				if (skb_copy_and_csum_datagram(list, offset-start, to, copy, &csum2))
+				if (skb_copy_and_csum_datagram(list,
+							       offset - start,
+							       to, copy,
+							       &csum2))
 					goto fault;
 				*csump = csum_block_add(*csump, csum2, pos);
 				if ((len -= copy) == 0)
@@ -352,39 +379,48 @@ int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, u8 *to, in
 			start = end;
 		}
 	}
-	if (len == 0)
+	if (!len)
 		return 0;
 
 fault:
 	return -EFAULT;
 }
 
-/* Copy and checkum skb to user iovec. 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!
+/**
+ *	skb_copy_and_csum_datagram_iovec - Copy and checkum skb to user iovec.
+ *	@skb - skbuff
+ *	@hlen - hardware length
+ *	@iovec - 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(const struct sk_buff *skb, int hlen, struct iovec *iov)
+int skb_copy_and_csum_datagram_iovec(const struct sk_buff *skb,
+				     int hlen, struct iovec *iov)
 {
 	unsigned int csum;
 	int chunk = skb->len - hlen;
 
-	/* Skip filled elements. Pretty silly, look at memcpy_toiovec, though 8) */
-	while (iov->iov_len == 0)
+	/* Skip filled elements.
+	 * Pretty silly, look at memcpy_toiovec, though 8)
+	 */
+	while (!iov->iov_len)
 		iov++;
 
 	if (iov->iov_len < chunk) {
-		if ((unsigned short)csum_fold(skb_checksum(skb, 0, chunk+hlen, skb->csum)))
+		if ((unsigned short)csum_fold(skb_checksum(skb, 0, chunk + hlen,
+							   skb->csum)))
 			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))
+		if (skb_copy_and_csum_datagram(skb, hlen, iov->iov_base,
+					       chunk, &csum))
 			goto fault;
 		if ((unsigned short)csum_fold(csum))
 			goto csum_error;
@@ -392,17 +428,18 @@ int skb_copy_and_csum_datagram_iovec(const struct sk_buff *skb, int hlen, struct
 		iov->iov_base += chunk;
 	}
 	return 0;
-
 csum_error:
 	return -EINVAL;
-
 fault:
 	return -EFAULT;
 }
 
-
-
-/*
+/**
+ * 	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.
@@ -411,8 +448,8 @@ int skb_copy_and_csum_datagram_iovec(const struct sk_buff *skb, int hlen, struct
  *	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)
+unsigned int datagram_poll(struct file *file, struct socket *sock,
+			   poll_table *wait)
 {
 	struct sock *sk = sock->sk;
 	unsigned int mask;
@@ -427,12 +464,13 @@ unsigned int datagram_poll(struct file * file, struct socket *sock, poll_table *
 		mask |= POLLHUP;
 
 	/* readable? */
-	if (!skb_queue_empty(&sk->receive_queue) || (sk->shutdown&RCV_SHUTDOWN))
+	if (!skb_queue_empty(&sk->receive_queue) ||
+	    (sk->shutdown & RCV_SHUTDOWN))
 		mask |= POLLIN | POLLRDNORM;
 
 	/* Connection-based need to check for termination and startup */
 	if (connection_based(sk)) {
-		if (sk->state==TCP_CLOSE)
+		if (sk->state == TCP_CLOSE)
 			mask |= POLLHUP;
 		/* connection hasn't started yet? */
 		if (sk->state == TCP_SYN_SENT)