blob: 1535e87ed9bd4fa47a7f431afab82320cf5e8530 [file] [log] [blame]
Jan Engelhardt563d36e2009-02-18 18:38:40 +01001/*
2 * TTL modification target for IP tables
3 * (C) 2000,2005 by Harald Welte <laforge@netfilter.org>
4 *
5 * Hop Limit modification target for ip6tables
6 * Maciej Soltysiak <solt@dns.toxicfilms.tv>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 */
Jan Engelhardt8bee4ba2010-03-17 16:04:40 +010012#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
Jan Engelhardt563d36e2009-02-18 18:38:40 +010013#include <linux/module.h>
14#include <linux/skbuff.h>
15#include <linux/ip.h>
16#include <linux/ipv6.h>
17#include <net/checksum.h>
18
19#include <linux/netfilter/x_tables.h>
20#include <linux/netfilter_ipv4/ipt_TTL.h>
21#include <linux/netfilter_ipv6/ip6t_HL.h>
22
23MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
24MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>");
25MODULE_DESCRIPTION("Xtables: Hoplimit/TTL Limit field modification target");
26MODULE_LICENSE("GPL");
27
28static unsigned int
Jan Engelhardt4b560b42009-07-05 19:43:26 +020029ttl_tg(struct sk_buff *skb, const struct xt_action_param *par)
Jan Engelhardt563d36e2009-02-18 18:38:40 +010030{
31 struct iphdr *iph;
32 const struct ipt_TTL_info *info = par->targinfo;
33 int new_ttl;
34
35 if (!skb_make_writable(skb, skb->len))
36 return NF_DROP;
37
38 iph = ip_hdr(skb);
39
40 switch (info->mode) {
Joe Perches181b1e92011-07-01 09:43:06 +000041 case IPT_TTL_SET:
42 new_ttl = info->ttl;
43 break;
44 case IPT_TTL_INC:
45 new_ttl = iph->ttl + info->ttl;
46 if (new_ttl > 255)
47 new_ttl = 255;
48 break;
49 case IPT_TTL_DEC:
50 new_ttl = iph->ttl - info->ttl;
51 if (new_ttl < 0)
52 new_ttl = 0;
53 break;
54 default:
55 new_ttl = iph->ttl;
56 break;
Jan Engelhardt563d36e2009-02-18 18:38:40 +010057 }
58
59 if (new_ttl != iph->ttl) {
60 csum_replace2(&iph->check, htons(iph->ttl << 8),
61 htons(new_ttl << 8));
62 iph->ttl = new_ttl;
63 }
64
65 return XT_CONTINUE;
66}
67
68static unsigned int
Jan Engelhardt4b560b42009-07-05 19:43:26 +020069hl_tg6(struct sk_buff *skb, const struct xt_action_param *par)
Jan Engelhardt563d36e2009-02-18 18:38:40 +010070{
71 struct ipv6hdr *ip6h;
72 const struct ip6t_HL_info *info = par->targinfo;
73 int new_hl;
74
75 if (!skb_make_writable(skb, skb->len))
76 return NF_DROP;
77
78 ip6h = ipv6_hdr(skb);
79
80 switch (info->mode) {
Joe Perches181b1e92011-07-01 09:43:06 +000081 case IP6T_HL_SET:
82 new_hl = info->hop_limit;
83 break;
84 case IP6T_HL_INC:
85 new_hl = ip6h->hop_limit + info->hop_limit;
86 if (new_hl > 255)
87 new_hl = 255;
88 break;
89 case IP6T_HL_DEC:
90 new_hl = ip6h->hop_limit - info->hop_limit;
91 if (new_hl < 0)
92 new_hl = 0;
93 break;
94 default:
95 new_hl = ip6h->hop_limit;
96 break;
Jan Engelhardt563d36e2009-02-18 18:38:40 +010097 }
98
99 ip6h->hop_limit = new_hl;
100
101 return XT_CONTINUE;
102}
103
Jan Engelhardt135367b2010-03-19 17:16:42 +0100104static int ttl_tg_check(const struct xt_tgchk_param *par)
Jan Engelhardt563d36e2009-02-18 18:38:40 +0100105{
106 const struct ipt_TTL_info *info = par->targinfo;
107
108 if (info->mode > IPT_TTL_MAXMODE) {
Jan Engelhardt8bee4ba2010-03-17 16:04:40 +0100109 pr_info("TTL: invalid or unknown mode %u\n", info->mode);
Jan Engelhardt4a5a5c72010-03-19 17:32:59 +0100110 return -EINVAL;
Jan Engelhardt563d36e2009-02-18 18:38:40 +0100111 }
112 if (info->mode != IPT_TTL_SET && info->ttl == 0)
Jan Engelhardtd6b00a52010-03-25 16:34:45 +0100113 return -EINVAL;
114 return 0;
Jan Engelhardt563d36e2009-02-18 18:38:40 +0100115}
116
Jan Engelhardt135367b2010-03-19 17:16:42 +0100117static int hl_tg6_check(const struct xt_tgchk_param *par)
Jan Engelhardt563d36e2009-02-18 18:38:40 +0100118{
119 const struct ip6t_HL_info *info = par->targinfo;
120
121 if (info->mode > IP6T_HL_MAXMODE) {
Jan Engelhardt8bee4ba2010-03-17 16:04:40 +0100122 pr_info("invalid or unknown mode %u\n", info->mode);
Jan Engelhardtd6b00a52010-03-25 16:34:45 +0100123 return -EINVAL;
Jan Engelhardt563d36e2009-02-18 18:38:40 +0100124 }
125 if (info->mode != IP6T_HL_SET && info->hop_limit == 0) {
Jan Engelhardt8bee4ba2010-03-17 16:04:40 +0100126 pr_info("increment/decrement does not "
Jan Engelhardt563d36e2009-02-18 18:38:40 +0100127 "make sense with value 0\n");
Jan Engelhardtd6b00a52010-03-25 16:34:45 +0100128 return -EINVAL;
Jan Engelhardt563d36e2009-02-18 18:38:40 +0100129 }
Jan Engelhardtd6b00a52010-03-25 16:34:45 +0100130 return 0;
Jan Engelhardt563d36e2009-02-18 18:38:40 +0100131}
132
133static struct xt_target hl_tg_reg[] __read_mostly = {
134 {
135 .name = "TTL",
136 .revision = 0,
137 .family = NFPROTO_IPV4,
138 .target = ttl_tg,
139 .targetsize = sizeof(struct ipt_TTL_info),
140 .table = "mangle",
141 .checkentry = ttl_tg_check,
142 .me = THIS_MODULE,
143 },
144 {
145 .name = "HL",
146 .revision = 0,
147 .family = NFPROTO_IPV6,
148 .target = hl_tg6,
149 .targetsize = sizeof(struct ip6t_HL_info),
150 .table = "mangle",
151 .checkentry = hl_tg6_check,
152 .me = THIS_MODULE,
153 },
154};
155
156static int __init hl_tg_init(void)
157{
158 return xt_register_targets(hl_tg_reg, ARRAY_SIZE(hl_tg_reg));
159}
160
161static void __exit hl_tg_exit(void)
162{
163 xt_unregister_targets(hl_tg_reg, ARRAY_SIZE(hl_tg_reg));
164}
165
166module_init(hl_tg_init);
167module_exit(hl_tg_exit);
168MODULE_ALIAS("ipt_TTL");
169MODULE_ALIAS("ip6t_HL");