Index: contrib/tcpdump/interface.h
diff -u contrib/tcpdump/interface.h:1.4.2.1 contrib/tcpdump/interface.h:1.4.2.1.6.1
--- contrib/tcpdump/interface.h:1.4.2.1	Thu Jul 26 15:30:00 2001
+++ contrib/tcpdump/interface.h	Fri Jul 12 06:29:47 2002
@@ -132,8 +132,16 @@
 extern const u_char *packetp;
 extern const u_char *snapend;
 
-/* True if  "l" bytes of "var" were captured */
-#define TTEST2(var, l) ((u_char *)&(var) <= snapend - (l))
+/*
+ * True if  "l" bytes of "var" were captured.
+ *
+ * The "snapend - (l) <= snapend" checks to make sure "l" isn't so large
+ * that "snapend - (l)" underflows.
+ *
+ * The check is for <= rather than < because "l" might be 0.
+ */
+#define TTEST2(var, l) (snapend - (l) <= snapend && \
+			(const u_char *)&(var) <= snapend - (l))
 
 /* True if "var" was captured */
 #define TTEST(var) TTEST2(var, sizeof(var))