From fba3cfdef21945e2fcc20b90c782c736577520b8 Mon Sep 17 00:00:00 2001
From: John Polstra <jdp@FreeBSD.org>
Date: Sun, 17 Dec 2000 20:50:22 +0000
Subject: [PATCH] Fix bug: a read() on a bpf device which was in non-blocking
 mode and had no data available returned 0.  Now it returns -1 with errno set
 to EWOULDBLOCK (== EAGAIN) as it should.  This fix makes the bpf device
 usable in threaded programs.

Reviewed by:	bde
---
 sys/net/bpf.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/sys/net/bpf.c b/sys/net/bpf.c
index d2eaa39dffe..12e375e37e9 100644
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -500,11 +500,12 @@ bpfread(dev, uio, ioflag)
 			return (ENXIO);
 		}
 
-		if (ioflag & IO_NDELAY)
-			error = EWOULDBLOCK;
-		else
-			error = BPF_SLEEP((caddr_t)d, PRINET|PCATCH, "bpf",
-					  d->bd_rtout);
+		if (ioflag & IO_NDELAY) {
+			splx(s);
+			return (EWOULDBLOCK);
+		}
+		error = BPF_SLEEP((caddr_t)d, PRINET|PCATCH, "bpf",
+				  d->bd_rtout);
 		if (error == EINTR || error == ERESTART) {
 			splx(s);
 			return (error);