Don't double-count received packets on Linux systems that support the

PACKET_STATISTICS getsockopt() argument on PF_PACKET sockets.

diff --git a/pcap-int.h b/pcap-int.h
index 927510e44bb492fe12d463ff2ad9314d11c37657..49fa3ef52f6f31cd21572ca495ac0659d4a920e8 100644 (file)
--- a/pcap-int.h
+++ b/pcap-int.h
@@ -30,7 +30,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * @(#) $Header: /tcpdump/master/libpcap/pcap-int.h,v 1.75 2005-07-07 06:55:20 guy Exp $ (LBL)
+ * @(#) $Header: /tcpdump/master/libpcap/pcap-int.h,v 1.76 2005-11-24 19:27:42 guy Exp $ (LBL)
  */
 
 #ifndef pcap_int_h
@@ -88,6 +88,7 @@ struct pcap_md {
        int     ifindex;        /* interface index of device we're bound to */
        int     lo_ifindex;     /* interface index of the loopback device */
        struct pcap *next;      /* list of open promiscuous sock_packet pcaps */
+       u_int   packets_read;   /* count of packets read with recvfrom() */
 #endif
 
 #ifdef HAVE_DAG_API

diff --git a/pcap-linux.c b/pcap-linux.c
index c66ed9860c6f7e79565d44821046664cd0f02013..219851ade2c8ac58571d6a51cf5ee00464b567a5 100644 (file)
--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -27,7 +27,7 @@
 
 #ifndef lint
 static const char rcsid[] _U_ =
-    "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.117 2005-10-08 11:30:26 guy Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.118 2005-11-24 19:27:42 guy Exp $ (LBL)";
 #endif
 
 /*
@@ -704,8 +704,18 @@ pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata)
         * here, but it's not clear that always incrementing
         * the count is more expensive than always testing a flag
         * in memory.
+        *
+        * We keep the count in "md.packets_read", and use that for
+        * "ps_recv" if we can't get the statistics from the kernel.
+        * We do that because, if we *can* get the statistics from
+        * the kernel, we use "md.stat.ps_recv" and "md.stat.ps_drop"
+        * as running counts, as reading the statistics from the
+        * kernel resets the kernel statistics, and if we directly
+        * increment "md.stat.ps_recv" here, that means it will
+        * count packets *twice* on systems where we can get kernel
+        * statistics - once here, and once in pcap_stats_linux().
         */
-       handle->md.stat.ps_recv++;
+       handle->md.packets_read++;
 
        /* Call the user supplied callback function */
        callback(userdata, &pcap_header, bp);
@@ -853,8 +863,14 @@ pcap_stats_linux(pcap_t *handle, struct pcap_stat *stats)
         *
         *      "ps_recv" doesn't include packets not yet read from
         *      the kernel by libpcap.
+        *
+        * We maintain the count of packets processed by libpcap in
+        * "md.packets_read", for reasons described in the comment
+        * at the end of pcap_read_packet().  We have no idea how many
+        * packets were dropped.
         */
-       *stats = handle->md.stat;
+       stats->ps_recv = handle->md.packets_read;
+       stats->ps_drop = 0;
        return 0;
 }