From e6a4b8c7dfa4c88e9971d69bf703864aa6e36ba5 Mon Sep 17 00:00:00 2001
From: Artur Grabowski <art@cvs.openbsd.org>
Date: Tue, 1 Apr 2003 23:42:25 +0000
Subject: When using bpf(4) in immediate mode, and using kevent(2) to receive
 notification of packet arrival, the usermode application isn't notified until
 a second packet arrives.

This is because KNOTE() calls filt_bpfread() before bd_slen has been
updated with the newly arrived packet length, so it looks like there
is no data there.

Moving the bpf_wakeup() call for immediate mode to after bd_slen is set
fixes it.

From: wayne@epipe.com.au in pr 3175
---
 sys/net/bpf.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/sys/net/bpf.c b/sys/net/bpf.c
index 707609ad872..b502837083b 100644
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bpf.c,v 1.33 2002/06/06 21:34:16 provos Exp $	*/
+/*	$OpenBSD: bpf.c,v 1.34 2003/04/01 23:42:24 art Exp $	*/
 /*	$NetBSD: bpf.c,v 1.33 1997/02/21 23:59:35 thorpej Exp $	*/
 
 /*
@@ -1163,13 +1163,6 @@ bpf_catchpacket(d, pkt, pktlen, snaplen, cpfn)
 		bpf_wakeup(d);
 		curlen = 0;
 	}
-	else if (d->bd_immediate) {
-		/*
-		 * Immediate mode is set.  A packet arrived so any
-		 * reads should be woken up.
-		 */
-		bpf_wakeup(d);
-	}
 
 	/*
 	 * Append the bpf header.
@@ -1186,6 +1179,14 @@ bpf_catchpacket(d, pkt, pktlen, snaplen, cpfn)
 	(*cpfn)(pkt, (u_char *)hp + hdrlen, (hp->bh_caplen = totlen - hdrlen));
 	d->bd_slen = curlen + totlen;
 
+	if (d->bd_immediate) {
+		/*
+		 * Immediate mode is set.  A packet arrived so any
+		 * reads should be woken up.
+		 */
+		bpf_wakeup(d);
+	}
+
 	if (d->bd_rdStart && (d->bd_rtout + d->bd_rdStart < ticks)) {
 		/*
 		 * we could be selecting on the bpf, and we
-- 
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