From: guy <guy>
Date: Sat, 26 Feb 2005 21:58:05 +0000 (+0000)
Subject: On the platforms where we do in-kernel filtering and can read more than
X-Git-Tag: libpcap-0.9.1~81
X-Git-Url: https://git.tcpdump.org/libpcap/commitdiff_plain/16889bae3e84aaaf62e2c9f6dd478fdadbb953f1

On the platforms where we do in-kernel filtering and can read more than
one packet from the kernel at a time, when the filter is changed, clear
the libpcap buffer to discard packets read from the kernel before the
filter was changed.
---

diff --git a/pcap-bpf.c b/pcap-bpf.c
index 1c61f7a1..b29d6c44 100644
--- a/pcap-bpf.c
+++ b/pcap-bpf.c
@@ -20,7 +20,7 @@
  */
 #ifndef lint
 static const char rcsid[] _U_ =
-    "@(#) $Header: /tcpdump/master/libpcap/pcap-bpf.c,v 1.85 2005-02-24 08:59:38 guy Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/pcap-bpf.c,v 1.86 2005-02-26 21:58:05 guy Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -1077,6 +1077,14 @@ pcap_setfilter_bpf(pcap_t *p, struct bpf_program *fp)
 		return (-1);
 	}
 	p->md.use_bpf = 1;	/* filtering in the kernel */
+
+	/*
+	 * Discard any previously-received packets, as they might have
+	 * passed whatever filter was formerly in effect, but might
+	 * not pass this filter (BIOCSETF discards packets buffered
+	 * in the kernel, so you can lose packets in any case).
+	 */
+	p->cc = 0;
 	return (0);
 }
 
diff --git a/pcap-pf.c b/pcap-pf.c
index fe21c803..23f01535 100644
--- a/pcap-pf.c
+++ b/pcap-pf.c
@@ -24,7 +24,7 @@
 
 #ifndef lint
 static const char rcsid[] _U_ =
-    "@(#) $Header: /tcpdump/master/libpcap/pcap-pf.c,v 1.90 2004-12-15 00:25:09 guy Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/pcap-pf.c,v 1.91 2005-02-26 21:58:06 guy Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -567,6 +567,16 @@ pcap_setfilter_pf(pcap_t *p, struct bpf_program *fp)
 			 */
 			fprintf(stderr, "tcpdump: Using kernel BPF filter\n");
 			p->md.use_bpf = 1;
+
+			/*
+			 * Discard any previously-received packets,
+			 * as they might have passed whatever filter
+			 * was formerly in effect, but might not pass
+			 * this filter (BIOCSETF discards packets buffered
+			 * in the kernel, so you can lose packets in any
+			 * case).
+			 */
+			p->cc = 0;
 			return (0);
 		}
 
diff --git a/pcap-win32.c b/pcap-win32.c
index 7f45a730..f6e37cf0 100644
--- a/pcap-win32.c
+++ b/pcap-win32.c
@@ -32,7 +32,7 @@
 
 #ifndef lint
 static const char rcsid[] _U_ =
-    "@(#) $Header: /tcpdump/master/libpcap/pcap-win32.c,v 1.24 2004-12-17 20:41:59 guy Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/pcap-win32.c,v 1.25 2005-02-26 21:58:06 guy Exp $ (LBL)";
 #endif
 
 #include <pcap-int.h>
@@ -631,10 +631,22 @@ static int
 pcap_setfilter_win32_npf(pcap_t *p, struct bpf_program *fp)
 {
 	if(PacketSetBpf(p->adapter,fp)==FALSE){
-		/* kernel filter not installed. */
+		/*
+		 * Kernel filter not installed.
+		 * XXX - fall back on userland filtering, as is done
+		 * on other platforms?
+		 */
 		snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "Driver error: cannot set bpf filter: %s", pcap_win32strerror());
 		return (-1);
 	}
+
+	/*
+	 * Discard any previously-received packets, as they might have
+	 * passed whatever filter was formerly in effect, but might
+	 * not pass this filter (BIOCSETF discards packets buffered
+	 * in the kernel, so you can lose packets in any case).
+	 */
+	p->cc = 0;
 	return (0);
 }