[NETFILTER]: Add new iptables TTL target
This new iptables target allows manipulation of the TTL of an IPv4 packet.
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netfilter_ipv4/ipt_TTL.h b/include/linux/netfilter_ipv4/ipt_TTL.h
new file mode 100644
index 0000000..ee6611e
--- /dev/null
+++ b/include/linux/netfilter_ipv4/ipt_TTL.h
@@ -0,0 +1,21 @@
+/* TTL modification module for IP tables
+ * (C) 2000 by Harald Welte <laforge@netfilter.org> */
+
+#ifndef _IPT_TTL_H
+#define _IPT_TTL_H
+
+enum {
+ IPT_TTL_SET = 0,
+ IPT_TTL_INC,
+ IPT_TTL_DEC
+};
+
+#define IPT_TTL_MAXMODE IPT_TTL_DEC
+
+struct ipt_TTL_info {
+ u_int8_t mode;
+ u_int8_t ttl;
+};
+
+
+#endif
diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index c4213f3..e046f55 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -664,6 +664,20 @@
To compile it as a module, choose M here. If unsure, say N.
+config IP_NF_TARGET_TTL
+ tristate 'TTL target support'
+ depends on IP_NF_MANGLE
+ help
+ This option adds a `TTL' target, which enables the user to modify
+ the TTL value of the IP header.
+
+ While it is safe to decrement/lower the TTL, this target also enables
+ functionality to increment and set the TTL value of the IP header to
+ arbitrary values. This is EXTREMELY DANGEROUS since you can easily
+ create immortal packets that loop forever on the network.
+
+ To compile it as a module, choose M here. If unsure, say N.
+
config IP_NF_TARGET_CONNMARK
tristate 'CONNMARK target support'
depends on IP_NF_CONNTRACK_MARK && IP_NF_MANGLE
diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile
index 89cae69..a7bd38f 100644
--- a/net/ipv4/netfilter/Makefile
+++ b/net/ipv4/netfilter/Makefile
@@ -85,6 +85,7 @@
obj-$(CONFIG_IP_NF_TARGET_TCPMSS) += ipt_TCPMSS.o
obj-$(CONFIG_IP_NF_TARGET_NOTRACK) += ipt_NOTRACK.o
obj-$(CONFIG_IP_NF_TARGET_CLUSTERIP) += ipt_CLUSTERIP.o
+obj-$(CONFIG_IP_NF_TARGET_TTL) += ipt_TTL.o
# generic ARP tables
obj-$(CONFIG_IP_NF_ARPTABLES) += arp_tables.o
diff --git a/net/ipv4/netfilter/ipt_TTL.c b/net/ipv4/netfilter/ipt_TTL.c
new file mode 100644
index 0000000..b9ae6a9
--- /dev/null
+++ b/net/ipv4/netfilter/ipt_TTL.c
@@ -0,0 +1,119 @@
+/* TTL modification target for IP tables
+ * (C) 2000,2005 by Harald Welte <laforge@netfilter.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/ip.h>
+#include <net/checksum.h>
+
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_TTL.h>
+
+MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
+MODULE_DESCRIPTION("IP tables TTL modification module");
+MODULE_LICENSE("GPL");
+
+static unsigned int
+ipt_ttl_target(struct sk_buff **pskb, const struct net_device *in,
+ const struct net_device *out, unsigned int hooknum,
+ const void *targinfo, void *userinfo)
+{
+ struct iphdr *iph;
+ const struct ipt_TTL_info *info = targinfo;
+ u_int16_t diffs[2];
+ int new_ttl;
+
+ if (!skb_make_writable(pskb, (*pskb)->len))
+ return NF_DROP;
+
+ iph = (*pskb)->nh.iph;
+
+ switch (info->mode) {
+ case IPT_TTL_SET:
+ new_ttl = info->ttl;
+ break;
+ case IPT_TTL_INC:
+ new_ttl = iph->ttl + info->ttl;
+ if (new_ttl > 255)
+ new_ttl = 255;
+ break;
+ case IPT_TTL_DEC:
+ new_ttl = iph->ttl - info->ttl;
+ if (new_ttl < 0)
+ new_ttl = 0;
+ break;
+ default:
+ new_ttl = iph->ttl;
+ break;
+ }
+
+ if (new_ttl != iph->ttl) {
+ diffs[0] = htons(((unsigned)iph->ttl) << 8) ^ 0xFFFF;
+ iph->ttl = new_ttl;
+ diffs[1] = htons(((unsigned)iph->ttl) << 8);
+ iph->check = csum_fold(csum_partial((char *)diffs,
+ sizeof(diffs),
+ iph->check^0xFFFF));
+ }
+
+ return IPT_CONTINUE;
+}
+
+static int ipt_ttl_checkentry(const char *tablename,
+ const struct ipt_entry *e,
+ void *targinfo,
+ unsigned int targinfosize,
+ unsigned int hook_mask)
+{
+ struct ipt_TTL_info *info = targinfo;
+
+ if (targinfosize != IPT_ALIGN(sizeof(struct ipt_TTL_info))) {
+ printk(KERN_WARNING "ipt_TTL: targinfosize %u != %Zu\n",
+ targinfosize,
+ IPT_ALIGN(sizeof(struct ipt_TTL_info)));
+ return 0;
+ }
+
+ if (strcmp(tablename, "mangle")) {
+ printk(KERN_WARNING "ipt_TTL: can only be called from "
+ "\"mangle\" table, not \"%s\"\n", tablename);
+ return 0;
+ }
+
+ if (info->mode > IPT_TTL_MAXMODE) {
+ printk(KERN_WARNING "ipt_TTL: invalid or unknown Mode %u\n",
+ info->mode);
+ return 0;
+ }
+
+ if ((info->mode != IPT_TTL_SET) && (info->ttl == 0))
+ return 0;
+
+ return 1;
+}
+
+static struct ipt_target ipt_TTL = {
+ .name = "TTL",
+ .target = ipt_ttl_target,
+ .checkentry = ipt_ttl_checkentry,
+ .me = THIS_MODULE,
+};
+
+static int __init init(void)
+{
+ return ipt_register_target(&ipt_TTL);
+}
+
+static void __exit fini(void)
+{
+ ipt_unregister_target(&ipt_TTL);
+}
+
+module_init(init);
+module_exit(fini);