Index: bpf.c
===================================================================
RCS file: /home/ncvs/src/sys/net/bpf.c,v
retrieving revision 1.130
diff -u -p -r1.130 bpf.c
--- bpf.c	5 Jul 2004 16:28:31 -0000	1.130
+++ bpf.c	8 Sep 2004 09:22:09 -0000
@@ -347,6 +347,7 @@ bpfopen(dev, flags, fmt, td)
 	d->bd_bufsize = bpf_bufsize;
 	d->bd_sig = SIGIO;
 	d->bd_seesent = 1;
+	d->bd_tstamp = BPF_TSTAMP_MICROTIME;
 #ifdef MAC
 	mac_init_bpfdesc(d);
 	mac_create_bpfdesc(td->td_ucred, d);
@@ -629,6 +630,7 @@ reset_d(d)
  *  BIOCSHDRCMPLT	Set "header already complete" flag
  *  BIOCGSEESENT	Get "see packets sent" flag
  *  BIOCSSEESENT	Set "see packets sent" flag
+ *  BIOCSTSTAMP		Set "timestamp preference" flag
  */
 /* ARGSUSED */
 static	int
@@ -880,6 +882,13 @@ bpfioctl(dev, cmd, addr, flags, td)
 		d->bd_seesent = *(u_int *)addr;
 		break;
 
+	/*
+	 * Set "timestamp preference" flag
+	 */
+	case BIOCSTSTAMP:
+		d->bd_tstamp = *(u_int *)addr;
+		break;
+
 	case FIONBIO:		/* Non-blocking I/O */
 		break;
 
@@ -1331,7 +1340,14 @@ catchpacket(d, pkt, pktlen, snaplen, cpf
 	 * Append the bpf header.
 	 */
 	hp = (struct bpf_hdr *)(d->bd_sbuf + curlen);
-	microtime(&hp->bh_tstamp);
+	/*
+	 * Only prepend a timestamp if instructed to do so.
+	 * getmicrotime() is less accurate but potentially faster.
+	 */
+	if (d->bd_tstamp == BPF_TSTAMP_MICROTIME)
+		microtime(&hp->bh_tstamp);
+	else if (d->bd_tstamp == BPF_TSTAMP_GETMICROTIME)
+		getmicrotime(&hp->bh_tstamp);
 	hp->bh_datalen = pktlen;
 	hp->bh_hdrlen = hdrlen;
 	/*
Index: bpf.h
===================================================================
RCS file: /home/ncvs/src/sys/net/bpf.h,v
retrieving revision 1.36
diff -u -p -r1.36 bpf.h
--- bpf.h	30 May 2004 17:03:48 -0000	1.36
+++ bpf.h	8 Sep 2004 09:15:35 -0000
@@ -113,6 +113,7 @@ struct bpf_version {
 #define BIOCSSEESENT	_IOW('B',119, u_int)
 #define	BIOCSDLT	_IOW('B',120, u_int)
 #define	BIOCGDLTLIST	_IOWR('B',121, struct bpf_dltlist)
+#define	BIOCSTSTAMP	_IOW('B',122, u_int)
 
 /*
  * Structure prepended to each packet.
@@ -491,4 +492,13 @@ u_int	 bpf_filter(const struct bpf_insn 
  */
 #define BPF_MEMWORDS 16
 
+/*
+ * Defines to specify timestamping preference for a BPF instance.
+ * BPF_TSTAMP_MICROTIME is the default when none is specified.
+ * Other settings may increase BPF capture performance under load.
+ */
+#define BPF_TSTAMP_NONE			0x00	/* Don't timestamp packets */
+#define BPF_TSTAMP_MICROTIME		0x01	/* Use microtime() (slower) */
+#define BPF_TSTAMP_GETMICROTIME		0x02	/* Use getmicrotime() */
+
 #endif /* _NET_BPF_H_ */
Index: bpfdesc.h
===================================================================
RCS file: /home/ncvs/src/sys/net/bpfdesc.h,v
retrieving revision 1.27
diff -u -p -r1.27 bpfdesc.h
--- bpfdesc.h	7 Apr 2004 20:46:11 -0000	1.27
+++ bpfdesc.h	8 Sep 2004 09:17:16 -0000
@@ -73,6 +73,7 @@ struct bpf_d {
 	u_char		bd_promisc;	/* true if listening promiscuously */
 	u_char		bd_state;	/* idle, waiting, or timed out */
 	u_char		bd_immediate;	/* true to return on packet arrival */
+	u_char		bd_tstamp;	/* timestamping preferences */
 	int		bd_hdrcmplt;	/* false to fill in src lladdr automatically */
 	int		bd_seesent;	/* true if bpf should see sent packets */
 	int		bd_async;	/* non-zero if packet reception should generate signal */