From aedcf384bff416d37094d3a5d5316b19b1f86667 Mon Sep 17 00:00:00 2001
From: Sepherosa Ziehau <sephe@dragonflybsd.org>
Date: Sun, 30 Jul 2006 09:39:27 +0000
Subject: [PATCH] Rather than calling mircotime() in catchpacket(), make
 catchpacket() take a timeval indicating when the packet was captured. Move
 microtime() to the calling functions and grab the timestamp as soon as we
 know that we're going to call catchpacket at least once.

This means that we call microtime() once per matched packet, as
opposed to once per matched packet per bpf listener. It also means
that we return the same timestamp to all bpf listeners, rather than
slightly different ones.

It would be more accurate to call microtime() even earlier for all
packets, but microtime() can be costly, so this didn't seem like a good idea.

Obtained-from: FreeBSD (dwmalone@freebsd.org)
Remined-and-Reviewed-by: joerg
---
 sys/net/bpf.c | 33 +++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/sys/net/bpf.c b/sys/net/bpf.c
index b21b257ca1..5457498031 100644
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -38,7 +38,7 @@
  *      @(#)bpf.c	8.2 (Berkeley) 3/28/94
  *
  * $FreeBSD: src/sys/net/bpf.c,v 1.59.2.12 2002/04/14 21:41:48 luigi Exp $
- * $DragonFly: src/sys/net/bpf.c,v 1.31 2006/07/28 02:17:40 dillon Exp $
+ * $DragonFly: src/sys/net/bpf.c,v 1.32 2006/07/30 09:39:27 sephe Exp $
  */
 
 #include "use_bpf.h"
@@ -103,7 +103,8 @@ static int	bpf_setif(struct bpf_d *, struct ifreq *);
 static void	bpf_timed_out(void *);
 static void	bpf_wakeup(struct bpf_d *);
 static void	catchpacket(struct bpf_d *, u_char *, u_int, u_int,
-			    void (*)(const void *, void *, size_t));
+			    void (*)(const void *, void *, size_t),
+			    const struct timeval *);
 static void	reset_d(struct bpf_d *);
 static int	bpf_setf(struct bpf_d *, struct bpf_program *);
 static int	bpf_getdltlist(struct bpf_d *, struct bpf_dltlist *);
@@ -1022,6 +1023,8 @@ void
 bpf_tap(struct bpf_if *bp, u_char *pkt, u_int pktlen)
 {
 	struct bpf_d *d;
+	struct timeval tv;
+	int gottime = 0;
 	u_int slen;
 
 	/*
@@ -1032,8 +1035,13 @@ bpf_tap(struct bpf_if *bp, u_char *pkt, u_int pktlen)
 	SLIST_FOREACH(d, &bp->bif_dlist, bd_next) {
 		++d->bd_rcount;
 		slen = bpf_filter(d->bd_filter, pkt, pktlen, pktlen);
-		if (slen != 0)
-			catchpacket(d, pkt, pktlen, slen, ovbcopy);
+		if (slen != 0) {
+			if (!gottime) {
+				microtime(&tv);
+				gottime = 1;
+			}
+			catchpacket(d, pkt, pktlen, slen, ovbcopy, &tv);
+		}
 	}
 }
 
@@ -1072,6 +1080,8 @@ bpf_mtap(struct bpf_if *bp, struct mbuf *m)
 	struct bpf_d *d;
 	u_int pktlen, slen;
 	struct mbuf *m0;
+	struct timeval tv;
+	int gottime = 0;
 
 	/* Don't compute pktlen, if no descriptor is attached. */
 	if (SLIST_EMPTY(&bp->bif_dlist))
@@ -1086,8 +1096,14 @@ bpf_mtap(struct bpf_if *bp, struct mbuf *m)
 			continue;
 		++d->bd_rcount;
 		slen = bpf_filter(d->bd_filter, (u_char *)m, pktlen, 0);
-		if (slen != 0)
-			catchpacket(d, (u_char *)m, pktlen, slen, bpf_mcopy);
+		if (slen != 0) {
+			if (!gottime) {
+				microtime(&tv);
+				gottime = 1;
+			}
+			catchpacket(d, (u_char *)m, pktlen, slen, bpf_mcopy,
+				    &tv);
+		}
 	}
 }
 
@@ -1134,7 +1150,8 @@ bpf_ptap(struct bpf_if *bp, struct mbuf *m, const void *data, u_int dlen)
  */
 static void
 catchpacket(struct bpf_d *d, u_char *pkt, u_int pktlen, u_int snaplen,
-	    void (*cpfn)(const void *, void *, size_t))
+	    void (*cpfn)(const void *, void *, size_t),
+	    const struct timeval *tv)
 {
 	struct bpf_hdr *hp;
 	int totlen, curlen;
@@ -1183,7 +1200,7 @@ catchpacket(struct bpf_d *d, u_char *pkt, u_int pktlen, u_int snaplen,
 	 * Append the bpf header.
 	 */
 	hp = (struct bpf_hdr *)(d->bd_sbuf + curlen);
-	microtime(&hp->bh_tstamp);
+	hp->bh_tstamp = *tv;
 	hp->bh_datalen = pktlen;
 	hp->bh_hdrlen = hdrlen;
 	/*
-- 
2.41.0