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git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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kernel
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linux
[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>
authored by
Harald Welte
and committed by
David S. Miller
5f2c3b91
29e4f8b3
+21
include/linux/netfilter_ipv4/ipt_TTL.h
+21
include/linux/netfilter_ipv4/ipt_TTL.h
···
···
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/* TTL modification module for IP tables
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* (C) 2000 by Harald Welte <laforge@netfilter.org> */
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#ifndef _IPT_TTL_H
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#define _IPT_TTL_H
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enum {
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IPT_TTL_SET = 0,
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IPT_TTL_INC,
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IPT_TTL_DEC
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};
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#define IPT_TTL_MAXMODE IPT_TTL_DEC
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struct ipt_TTL_info {
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u_int8_t mode;
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u_int8_t ttl;
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};
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#endif
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net/ipv4/netfilter/Kconfig
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net/ipv4/netfilter/Kconfig
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To compile it as a module, choose M here. If unsure, say N.
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config IP_NF_TARGET_TTL
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tristate 'TTL target support'
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depends on IP_NF_MANGLE
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help
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This option adds a `TTL' target, which enables the user to modify
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the TTL value of the IP header.
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While it is safe to decrement/lower the TTL, this target also enables
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functionality to increment and set the TTL value of the IP header to
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arbitrary values. This is EXTREMELY DANGEROUS since you can easily
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create immortal packets that loop forever on the network.
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To compile it as a module, choose M here. If unsure, say N.
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config IP_NF_TARGET_CONNMARK
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tristate 'CONNMARK target support'
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depends on IP_NF_CONNTRACK_MARK && IP_NF_MANGLE
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net/ipv4/netfilter/Makefile
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net/ipv4/netfilter/Makefile
+119
net/ipv4/netfilter/ipt_TTL.c
+119
net/ipv4/netfilter/ipt_TTL.c
···
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/* TTL modification target for IP tables
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* (C) 2000,2005 by Harald Welte <laforge@netfilter.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/ip.h>
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#include <net/checksum.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/netfilter_ipv4/ipt_TTL.h>
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MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
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MODULE_DESCRIPTION("IP tables TTL modification module");
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MODULE_LICENSE("GPL");
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static unsigned int
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ipt_ttl_target(struct sk_buff **pskb, const struct net_device *in,
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const struct net_device *out, unsigned int hooknum,
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const void *targinfo, void *userinfo)
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{
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struct iphdr *iph;
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const struct ipt_TTL_info *info = targinfo;
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u_int16_t diffs[2];
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int new_ttl;
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if (!skb_make_writable(pskb, (*pskb)->len))
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return NF_DROP;
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iph = (*pskb)->nh.iph;
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switch (info->mode) {
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case IPT_TTL_SET:
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new_ttl = info->ttl;
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break;
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case IPT_TTL_INC:
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new_ttl = iph->ttl + info->ttl;
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if (new_ttl > 255)
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new_ttl = 255;
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break;
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case IPT_TTL_DEC:
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new_ttl = iph->ttl - info->ttl;
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if (new_ttl < 0)
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new_ttl = 0;
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break;
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default:
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new_ttl = iph->ttl;
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break;
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}
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if (new_ttl != iph->ttl) {
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diffs[0] = htons(((unsigned)iph->ttl) << 8) ^ 0xFFFF;
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iph->ttl = new_ttl;
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diffs[1] = htons(((unsigned)iph->ttl) << 8);
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iph->check = csum_fold(csum_partial((char *)diffs,
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sizeof(diffs),
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iph->check^0xFFFF));
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}
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return IPT_CONTINUE;
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}
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static int ipt_ttl_checkentry(const char *tablename,
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const struct ipt_entry *e,
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void *targinfo,
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unsigned int targinfosize,
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unsigned int hook_mask)
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{
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struct ipt_TTL_info *info = targinfo;
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if (targinfosize != IPT_ALIGN(sizeof(struct ipt_TTL_info))) {
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printk(KERN_WARNING "ipt_TTL: targinfosize %u != %Zu\n",
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targinfosize,
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IPT_ALIGN(sizeof(struct ipt_TTL_info)));
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return 0;
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}
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if (strcmp(tablename, "mangle")) {
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printk(KERN_WARNING "ipt_TTL: can only be called from "
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"\"mangle\" table, not \"%s\"\n", tablename);
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return 0;
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}
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if (info->mode > IPT_TTL_MAXMODE) {
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printk(KERN_WARNING "ipt_TTL: invalid or unknown Mode %u\n",
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info->mode);
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return 0;
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}
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if ((info->mode != IPT_TTL_SET) && (info->ttl == 0))
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return 0;
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return 1;
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}
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static struct ipt_target ipt_TTL = {
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.name = "TTL",
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.target = ipt_ttl_target,
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.checkentry = ipt_ttl_checkentry,
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.me = THIS_MODULE,
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};
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static int __init init(void)
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{
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return ipt_register_target(&ipt_TTL);
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}
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static void __exit fini(void)
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{
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ipt_unregister_target(&ipt_TTL);
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}
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module_init(init);
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module_exit(fini);