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From: Jung-uk Kim <jkim@FreeBSD.org>
Date: Sat, 20 Feb 2010 00:19:21 +0000 (UTC)
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	svn-src-head@freebsd.org
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Subject: svn commit: r204105 - head/sys/net
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Author: jkim
Date: Sat Feb 20 00:19:21 2010
New Revision: 204105
URL: http://svn.freebsd.org/changeset/base/204105

Log:
  Return partially filled buffer for non-blocking read(2)
  in non-immediate mode.
  
  PR:		kern/143855

Modified:
  head/sys/net/bpf.c

Modified: head/sys/net/bpf.c
==============================================================================
--- head/sys/net/bpf.c	Sat Feb 20 00:16:44 2010	(r204104)
+++ head/sys/net/bpf.c	Sat Feb 20 00:19:21 2010	(r204105)
@@ -664,8 +664,9 @@ static	int
 bpfread(struct cdev *dev, struct uio *uio, int ioflag)
 {
 	struct bpf_d *d;
-	int timed_out;
 	int error;
+	int non_block;
+	int timed_out;
 
 	error = devfs_get_cdevpriv((void **)&d);
 	if (error != 0)
@@ -678,6 +679,8 @@ bpfread(struct cdev *dev, struct uio *ui
 	if (uio->uio_resid != d->bd_bufsize)
 		return (EINVAL);
 
+	non_block = ((ioflag & O_NONBLOCK) != 0);
+
 	BPFD_LOCK(d);
 	d->bd_pid = curthread->td_proc->p_pid;
 	if (d->bd_bufmode != BPF_BUFMODE_BUFFER) {
@@ -694,14 +697,20 @@ bpfread(struct cdev *dev, struct uio *ui
 	 * have arrived to fill the store buffer.
 	 */
 	while (d->bd_hbuf == NULL) {
-		if ((d->bd_immediate || timed_out) && d->bd_slen != 0) {
+		if (d->bd_slen != 0) {
 			/*
 			 * A packet(s) either arrived since the previous
 			 * read or arrived while we were asleep.
-			 * Rotate the buffers and return what's here.
 			 */
-			ROTATE_BUFFERS(d);
-			break;
+			if (d->bd_immediate || non_block || timed_out) {
+				/*
+				 * Rotate the buffers and return what's here
+				 * if we are in immediate mode, non-blocking
+				 * flag is set, or this descriptor timed out.
+				 */
+				ROTATE_BUFFERS(d);
+				break;
+			}
 		}
 
 		/*
@@ -715,7 +724,7 @@ bpfread(struct cdev *dev, struct uio *ui
 			return (ENXIO);
 		}
 
-		if (ioflag & O_NONBLOCK) {
+		if (non_block) {
 			BPFD_UNLOCK(d);
 			return (EWOULDBLOCK);
 		}