From: Vincent Bernat <bernat@luffy.cx>
Date: Mon, 2 Jan 2012 07:27:43 +0000 (+0100)
Subject: core: optimize BPF filter
X-Git-Tag: 0.5.6~4
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a2606cac2d73695d937ed686fbedd6deebb5c6f4;p=thirdparty%2Flldpd.git

core: optimize BPF filter

When monitoring high trafic interfaces, the BPF filter can become
quite important. We optimize it a bit by first checking if the
ethernet address is a multicast one. If it is not, we only have to
check for EDP.
---

diff --git a/CHANGELOG b/CHANGELOG
index 5539adf8..49744f2b 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -4,6 +4,7 @@ lldpd (0.5.6)
     + Add a whitelist for some drivers (currently: dsa and veth)
   * Fixes:
     + Compilation issues with NetSNMP 5.7 (and with earlier versions too)
+    + Small optimization of BPF filter
 
 lldpd (0.5.5)
   * Features:
diff --git a/src/interfaces.c b/src/interfaces.c
index 312189e3..c35bc840 100644
--- a/src/interfaces.c
+++ b/src/interfaces.c
@@ -46,28 +46,42 @@
 /* CDP: "ether dst 01:00:0c:cc:cc:cc" */
 /* SONMP: "ether dst 01:00:81:00:01:00" */
 /* EDP: "ether dst 00:e0:2b:00:00:00" */
-#define LLDPD_FILTER_F			\
-	{ 0x20, 0, 0, 0x00000002 },	\
-	{ 0x15, 0, 7, 0xc200000e },	\
-	{ 0x28, 0, 0, 0x00000000 },	\
-	{ 0x15, 0, 16, 0x00000180 },	\
-	{ 0x28, 0, 0, 0x0000000c },	\
-	{ 0x15, 13, 0, 0x000088cc },	\
-	{ 0x15, 0, 13, 0x00008100 },	\
-	{ 0x28, 0, 0, 0x00000010 },	\
-	{ 0x15, 10, 11, 0x000088cc },	\
-	{ 0x15, 0, 2, 0x2b000000 },	\
-	{ 0x28, 0, 0, 0x00000000 },	\
-	{ 0x15, 7, 8, 0x000000e0 },	\
-	{ 0x15, 1, 0, 0x0ccccccc },	\
-	{ 0x15, 0, 2, 0x81000100 },	\
-	{ 0x28, 0, 0, 0x00000000 },	\
-	{ 0x15, 3, 4, 0x00000100 },	\
-	{ 0x15, 0, 3, 0x52cccccc },	\
-	{ 0x28, 0, 0, 0x00000000 },	\
-	{ 0x15, 0, 1, 0x000001e0 },	\
-	{ 0x6, 0, 0, 0x0000ffff },	\
+/* For optimization purpose, we first check if the first bit of the
+   first byte is 1. if not, this can only be an EDP packet:
+
+   tcpdump -dd "(ether[0] & 1 = 1 and
+                 ((ether proto 0x88cc and ether dst 01:80:c2:00:00:0e) or
+                  (ether dst 01:e0:52:cc:cc:cc) or
+                  (ether dst 01:00:0c:cc:cc:cc) or
+                  (ether dst 01:00:81:00:01:00))) or
+                (ether dst 00:e0:2b:00:00:00)"
+*/
+
+#define LLDPD_FILTER_F				\
+	{ 0x30, 0, 0, 0x00000000 },		\
+	{ 0x54, 0, 0, 0x00000001 },		\
+	{ 0x15, 0, 14, 0x00000001 },		\
+	{ 0x28, 0, 0, 0x0000000c },		\
+	{ 0x15, 0, 4, 0x000088cc },		\
+	{ 0x20, 0, 0, 0x00000002 },		\
+	{ 0x15, 0, 2, 0xc200000e },		\
+	{ 0x28, 0, 0, 0x00000000 },		\
+	{ 0x15, 12, 13, 0x00000180 },		\
+	{ 0x20, 0, 0, 0x00000002 },		\
+	{ 0x15, 0, 2, 0x52cccccc },		\
+	{ 0x28, 0, 0, 0x00000000 },		\
+	{ 0x15, 8, 9, 0x000001e0 },		\
+	{ 0x15, 1, 0, 0x0ccccccc },		\
+	{ 0x15, 0, 2, 0x81000100 },		\
+	{ 0x28, 0, 0, 0x00000000 },		\
+	{ 0x15, 4, 5, 0x00000100 },		\
+	{ 0x20, 0, 0, 0x00000002 },		\
+	{ 0x15, 0, 3, 0x2b000000 },		\
+	{ 0x28, 0, 0, 0x00000000 },		\
+	{ 0x15, 0, 1, 0x000000e0 },		\
+	{ 0x6, 0, 0, 0x0000ffff },		\
 	{ 0x6, 0, 0, 0x00000000 },
+
 static struct sock_filter lldpd_filter_f[] = { LLDPD_FILTER_F };
 
 /* net/if.h */