Implement the -z (zero counters) option for the various bpf counters.

Add necessary changes to the kernel for this (basically introduce a
bpf_zero_counters() function).  As well, update the man page.

MFC after:	1 month
Discussed with:	rwatson

2 files changed, 9 insertions, 1 deletions

diff --git a/usr.bin/netstat/bpf.c b/usr.bin/netstat/bpf.c
index 4455d04..2ffeacb 100644
--- a/usr.bin/netstat/bpf.c
+++ b/usr.bin/netstat/bpf.c
@@ -91,10 +91,17 @@ bpf_flags(struct xbpf_d *bd, char *flagbuf)
 void
 bpf_stats(char *ifname)
 {
-	struct xbpf_d *d, *bd;
+	struct xbpf_d *d, *bd, zerostat;
 	char *pname, flagbuf[12];
 	size_t size;
 
+	if (zflag) {
+		bzero(&zerostat, sizeof(zerostat));
+		if (sysctlbyname("net.bpf.stats", NULL, NULL,
+		    &zerostat, sizeof(zerostat)) < 0)
+			warn("failed to zero bpf counters");
+		return;
+	}
 	if (sysctlbyname("net.bpf.stats", NULL, &size,
 	    NULL, 0) < 0) {
 		warn("net.bpf.stats");
diff --git a/usr.bin/netstat/netstat.1 b/usr.bin/netstat/netstat.1
index f78b29f..71af7aa 100644
--- a/usr.bin/netstat/netstat.1
+++ b/usr.bin/netstat/netstat.1
@@ -198,6 +198,7 @@ The network manages a private pool of memory buffers.
 .Bk -words
 .Nm
 .Fl B
+.Op Fl z
 .Op Fl I Ar interface
 .Ek
 .Xc