Harald Welte's ttl stuff.
This patch adds two new modules to the netfilter CVS patch-o-matic system:
A TTL match and a TTL target for setting/incrementing/decrementing the TTL.
diff --git a/extensions/libipt_TTL.c b/extensions/libipt_TTL.c
new file mode 100644
index 0000000..c125bdf
--- /dev/null
+++ b/extensions/libipt_TTL.c
@@ -0,0 +1,163 @@
+/* Shared library add-on to iptables for the TTL target
+ * (C) 2000 by Harald Welte <laforge@gnumonks.org>
+ *
+ * Version: 1.2
+ *
+ * This program is distributed under the terms of GNU GPL
+ */
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <iptables.h>
+
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_TTL.h>
+
+#define IPT_TTL_USED 1
+
+static void init(struct ipt_entry_target *t, unsigned int *nfcache)
+{
+}
+
+static void help(void)
+{
+ printf(
+"TTL target v%s options\n"
+" --ttl-set value Set TTL to <value>\n"
+" --ttl-dec value Decrement TTL by <value>\n"
+" --ttl-inc value Increment TTL by <value>\n"
+, NETFILTER_VERSION);
+}
+
+static int parse(int c, char **argv, int invert, unsigned int *flags,
+ const struct ipt_entry *entry,
+ struct ipt_entry_target **target)
+{
+ struct ipt_TTL_info *info = (struct ipt_TTL_info *) (*target)->data;
+ u_int8_t value;
+
+ if (*flags & IPT_TTL_USED) {
+ exit_error(PARAMETER_PROBLEM,
+ "Can't specify TTL option twice");
+ }
+
+ if (!optarg)
+ exit_error(PARAMETER_PROBLEM,
+ "TTL: You must specify a value");
+
+ if (check_inverse(optarg, &invert))
+ exit_error(PARAMETER_PROBLEM,
+ "TTL: unexpected `!'");
+
+ value = atoi(optarg);
+
+ switch (c) {
+
+ case '1':
+ info->mode = IPT_TTL_SET;
+ break;
+
+ case '2':
+ if (value == 0) {
+ exit_error(PARAMETER_PROBLEM,
+ "TTL: decreasing by 0?");
+ }
+
+ info->mode = IPT_TTL_DEC;
+ break;
+
+ case '3':
+ if (value == 0) {
+ exit_error(PARAMETER_PROBLEM,
+ "TTL: increasing by 0?");
+ }
+
+ info->mode = IPT_TTL_INC;
+ break;
+
+ default:
+ return 0;
+
+ }
+
+ info->ttl = value;
+ *flags |= IPT_TTL_USED;
+
+ return 1;
+}
+
+static void final_check(unsigned int flags)
+{
+ if (!(flags & IPT_TTL_USED))
+ exit_error(PARAMETER_PROBLEM,
+ "TTL: You must specify an action");
+}
+
+static void save(const struct ipt_ip *ip,
+ const struct ipt_entry_target *target)
+{
+ const struct ipt_TTL_info *info =
+ (struct ipt_TTL_info *) target->data;
+
+ switch (info->mode) {
+ case IPT_TTL_SET:
+ printf("--ttl-set ");
+ break;
+ case IPT_TTL_DEC:
+ printf("--ttl-dec ");
+ break;
+
+ case IPT_TTL_INC:
+ printf("--ttl-inc ");
+ break;
+ }
+ printf("%u ", info->ttl);
+}
+
+static void print(const struct ipt_ip *ip,
+ const struct ipt_entry_target *target, int numeric)
+{
+ const struct ipt_TTL_info *info =
+ (struct ipt_TTL_info *) target->data;
+
+ printf("TTL ");
+ switch (info->mode) {
+ case IPT_TTL_SET:
+ printf("set to ");
+ break;
+ case IPT_TTL_DEC:
+ printf("decrement by ");
+ break;
+ case IPT_TTL_INC:
+ printf("increment by ");
+ break;
+ }
+ printf("%u ", info->ttl);
+}
+
+static struct option opts[] = {
+ { "ttl-set", 1, 0, '1' },
+ { "ttl-dec", 1, 0, '2' },
+ { "ttl-inc", 1, 0, '3' },
+ { 0 }
+};
+
+struct iptables_target TTL = { NULL,
+ "TTL",
+ NETFILTER_VERSION,
+ IPT_ALIGN(sizeof(struct ipt_TTL_info)),
+ IPT_ALIGN(sizeof(struct ipt_TTL_info)),
+ &help,
+ &init,
+ &parse,
+ &final_check,
+ &print,
+ &save,
+ opts
+};
+
+void _init(void)
+{
+ register_target(&TTL);
+}