diff --git a/extensions/.u32-test b/extensions/.u32-test
new file mode 100755
index 0000000..77d8a00
--- /dev/null
+++ b/extensions/.u32-test
@@ -0,0 +1,3 @@
+#!/bin/sh
+# True if u32 is applied.
+[ -f $KERNEL_DIR/include/linux/netfilter_ipv4/ipt_u32.h ] && echo u32
diff --git a/extensions/libipt_u32.c b/extensions/libipt_u32.c
new file mode 100644
index 0000000..788413c
--- /dev/null
+++ b/extensions/libipt_u32.c
@@ -0,0 +1,272 @@
+/* Shared library add-on to iptables to add u32 matching,
+ * generalized matching on values found at packet offsets
+ *
+ * Detailed doc is in the kernel module source
+ * net/ipv4/netfilter/ipt_u32.c
+ *
+ * (C) 2002 by Don Cohen <don-netf@isis.cs3-inc.com>
+ * Released under the terms of GNU GPL v2
+ */
+#include <stdio.h>
+#include <netdb.h>
+#include <string.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <iptables.h>
+#include <linux/netfilter_ipv4/ipt_u32.h>
+#include <errno.h>
+#include <ctype.h>
+
+/* Function which prints out usage message. */
+static void
+help(void)
+{
+	printf( "u32 v%s options:\n"
+		" --u32 tests\n"
+		" tests := location = value | tests && location = value\n"
+		" value := range | value , range\n"
+		" range := number | number : number\n"
+		" location := number | location operator number\n"
+		" operator := & | << | >> | @\n"
+		,IPTABLES_VERSION);
+}
+
+/* defined in /usr/include/getopt.h maybe in man getopt */
+static struct option opts[] = {
+	{ "u32", 1, 0, '1' },
+	{ 0 }
+};
+
+/* Initialize the match. */
+static void
+init(struct ipt_entry_match *m, unsigned int *nfcache)
+{
+	*nfcache |= NFC_UNKNOWN;
+}
+
+/* shared printing code */
+static void print_u32(struct ipt_u32 *data)
+{
+	unsigned int testind;
+
+	for (testind=0; testind < data->ntests; testind++) {
+		if (testind) printf("&&");
+		{
+			unsigned int i;
+
+			printf("0x%x", data->tests[testind].location[0].number);
+			for (i = 1; i < data->tests[testind].nnums; i++) {
+				switch (data->tests[testind].location[i].nextop) {
+				case IPT_U32_AND: printf("&"); break;
+				case IPT_U32_LEFTSH: printf("<<"); break;
+				case IPT_U32_RIGHTSH: printf(">>"); break;
+				case IPT_U32_AT: printf("@"); break;
+				}
+				printf("0x%x", data->tests[testind].location[i].number);
+			}
+			printf("=");
+			for (i = 0; i < data->tests[testind].nvalues; i++) {
+				if (i) printf(",");
+				if (data->tests[testind].value[i].min
+				    == data->tests[testind].value[i].max)
+					printf("0x%x", data->tests[testind].value[i].min);
+				else printf("0x%x:0x%x", data->tests[testind].value[i].min,
+					    data->tests[testind].value[i].max);
+			}
+		}
+	}
+	printf(" ");
+}
+
+/* string_to_number is not quite what we need here ... */
+u_int32_t parse_number(char **s, int pos)
+{
+	u_int32_t number;
+	char *end;
+	errno = 0;
+
+	number = strtol(*s, &end, 0);
+	if (end == *s)
+		exit_error(PARAMETER_PROBLEM, 
+			   "u32: at char %d expected number", pos);
+	if (errno)
+		exit_error(PARAMETER_PROBLEM, 
+			   "u32: at char %d error reading number", pos);
+	*s = end;
+	return number;
+}
+
+/* Function which parses command options; returns true if it ate an option */
+static int
+parse(int c, char **argv, int invert, unsigned int *flags,
+      const struct ipt_entry *entry,
+      unsigned int *nfcache,
+      struct ipt_entry_match **match)
+{
+	struct ipt_u32 *data = (struct ipt_u32 *)(*match)->data;
+	char *arg = argv[optind-1]; /* the argument string */
+	char *start = arg;
+	int state=0, testind=0, locind=0, valind=0;
+
+	if (c != '1') return 0;
+	/* states: 0 = looking for numbers and operations, 1 = looking for ranges */
+	while (1) { /* read next operand/number or range */
+		while (isspace(*arg)) 
+			arg++;  /* skip white space */
+		if (! *arg) { /* end of argument found */
+			if (state == 0)
+				exit_error(PARAMETER_PROBLEM, 
+					   "u32: input ended in location spec");
+			if (valind == 0)
+				exit_error(PARAMETER_PROBLEM, 
+					   "u32: test ended with no value spec");
+			data->tests[testind].nnums = locind;
+			data->tests[testind].nvalues = valind;
+			testind++;
+			data->ntests=testind;
+			if (testind > U32MAXSIZE)
+				exit_error(PARAMETER_PROBLEM, 
+					   "u32: at char %d too many &&'s",
+					   arg-start);
+			/* debugging 
+			   print_u32(data);printf("\n");
+			   exit_error(PARAMETER_PROBLEM, "debugging output done"); */
+			return 1;
+		}
+		if (state == 0) {
+			/* reading location: read a number if nothing read yet,
+			   otherwise either op number or = to end location spec */	 
+			if (*arg == '=') {
+				if (locind == 0)
+					exit_error(PARAMETER_PROBLEM,
+						   "u32: at char %d location spec missing", arg-start);
+				else {
+					arg++; 
+					state=1;
+				}
+			}
+			else {
+				if (locind) { /* need op before number */
+					if (*arg == '&') {
+						data->tests[testind].location[locind].nextop = IPT_U32_AND;
+					}
+					else if (*arg == '<') {
+						arg++;
+						if (*arg != '<')
+							exit_error(PARAMETER_PROBLEM,
+								   "u32: at char %d a second < expected", arg-start);
+						data->tests[testind].location[locind].nextop = IPT_U32_LEFTSH;
+					}
+					else if (*arg == '>') {
+						arg++;
+						if (*arg != '>')
+							exit_error(PARAMETER_PROBLEM,
+								   "u32: at char %d a second > expected", arg-start);
+						data->tests[testind].location[locind].nextop = IPT_U32_RIGHTSH;
+					}
+					else if (*arg == '@') {
+						data->tests[testind].location[locind].nextop = IPT_U32_AT;
+					}
+					else exit_error(PARAMETER_PROBLEM,
+							"u32: at char %d operator expected", arg-start);
+					arg++;
+				}
+				/* now a number; string_to_number skips white space? */
+				data->tests[testind].location[locind].number =
+					parse_number(&arg, arg-start);
+				locind++;
+				if (locind > U32MAXSIZE)
+					exit_error(PARAMETER_PROBLEM,
+						   "u32: at char %d too many operators", arg-start);
+			}
+		}
+		else {
+			/* state 1 - reading values: read a range if nothing read yet,
+			   otherwise either ,range or && to end test spec */
+			if (*arg == '&') {
+				arg++;
+				if (*arg != '&')
+					exit_error(PARAMETER_PROBLEM,
+						   "u32: at char %d a second & expected", arg-start);
+				if (valind == 0)
+					exit_error(PARAMETER_PROBLEM,
+						   "u32: at char %d value spec missing", arg-start);
+				else {
+					data->tests[testind].nnums = locind;
+					data->tests[testind].nvalues = valind;
+					testind++;
+					if (testind > U32MAXSIZE)
+						exit_error(PARAMETER_PROBLEM,
+							   "u32: at char %d too many &&'s", arg-start);
+					arg++; state=0; locind=0; valind=0;
+				}
+			}
+			else { /* read value range */
+				if (valind) { /* need , before number */
+					if (*arg != ',')
+						exit_error(PARAMETER_PROBLEM,
+							   "u32: at char %d expected , or &&", arg-start);
+					arg++;
+				}
+				data->tests[testind].value[valind].min = parse_number(&arg, arg-start);
+				while (isspace(*arg)) 
+					arg++;  /* another place white space could be */
+				if (*arg==':') {
+					arg++;
+					data->tests[testind].value[valind].max
+						= parse_number(&arg, arg-start);
+				}
+				else data->tests[testind].value[valind].max
+					     = data->tests[testind].value[valind].min;
+				valind++;
+				if (valind > U32MAXSIZE)
+					exit_error(PARAMETER_PROBLEM,
+						   "u32: at char %d too many ,'s", arg-start);
+			}
+		}
+	}
+}
+
+/* Final check; must specify something. */
+static void
+final_check(unsigned int flags)
+{
+}
+
+/* Prints out the matchinfo. */
+static void
+print(const struct ipt_ip *ip,
+      const struct ipt_entry_match *match,
+      int numeric)
+{
+	printf("u32 ");
+	print_u32((struct ipt_u32 *)match->data);
+}
+
+/* Saves the union ipt_matchinfo in parsable form to stdout. */
+static void save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
+{
+	printf("--u32 ");
+	print_u32((struct ipt_u32 *)match->data);
+}
+
+struct iptables_match u32
+= { NULL,
+    "u32",
+    IPTABLES_VERSION,
+    IPT_ALIGN(sizeof(struct ipt_u32)),
+    IPT_ALIGN(sizeof(struct ipt_u32)),
+    &help,
+    &init,
+    &parse,
+    &final_check,
+    &print,
+    &save,
+    opts
+};
+
+void
+_init(void)
+{
+	register_match(&u32);
+}