Jan Engelhardt | 563d36e | 2009-02-18 18:38:40 +0100 | [diff] [blame] | 1 | /* |
| 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 | */ |
| 12 | |
| 13 | #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 | |
| 23 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); |
| 24 | MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>"); |
| 25 | MODULE_DESCRIPTION("Xtables: Hoplimit/TTL Limit field modification target"); |
| 26 | MODULE_LICENSE("GPL"); |
| 27 | |
| 28 | static unsigned int |
| 29 | ttl_tg(struct sk_buff *skb, const struct xt_target_param *par) |
| 30 | { |
| 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) { |
| 41 | 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; |
| 57 | } |
| 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 | |
| 68 | static unsigned int |
| 69 | hl_tg6(struct sk_buff *skb, const struct xt_target_param *par) |
| 70 | { |
| 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) { |
| 81 | 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; |
| 97 | } |
| 98 | |
| 99 | ip6h->hop_limit = new_hl; |
| 100 | |
| 101 | return XT_CONTINUE; |
| 102 | } |
| 103 | |
| 104 | static bool ttl_tg_check(const struct xt_tgchk_param *par) |
| 105 | { |
| 106 | const struct ipt_TTL_info *info = par->targinfo; |
| 107 | |
| 108 | if (info->mode > IPT_TTL_MAXMODE) { |
| 109 | printk(KERN_WARNING "ipt_TTL: invalid or unknown Mode %u\n", |
| 110 | info->mode); |
| 111 | return false; |
| 112 | } |
| 113 | if (info->mode != IPT_TTL_SET && info->ttl == 0) |
| 114 | return false; |
| 115 | return true; |
| 116 | } |
| 117 | |
| 118 | static bool hl_tg6_check(const struct xt_tgchk_param *par) |
| 119 | { |
| 120 | const struct ip6t_HL_info *info = par->targinfo; |
| 121 | |
| 122 | if (info->mode > IP6T_HL_MAXMODE) { |
| 123 | printk(KERN_WARNING "ip6t_HL: invalid or unknown Mode %u\n", |
| 124 | info->mode); |
| 125 | return false; |
| 126 | } |
| 127 | if (info->mode != IP6T_HL_SET && info->hop_limit == 0) { |
| 128 | printk(KERN_WARNING "ip6t_HL: increment/decrement doesn't " |
| 129 | "make sense with value 0\n"); |
| 130 | return false; |
| 131 | } |
| 132 | return true; |
| 133 | } |
| 134 | |
| 135 | static struct xt_target hl_tg_reg[] __read_mostly = { |
| 136 | { |
| 137 | .name = "TTL", |
| 138 | .revision = 0, |
| 139 | .family = NFPROTO_IPV4, |
| 140 | .target = ttl_tg, |
| 141 | .targetsize = sizeof(struct ipt_TTL_info), |
| 142 | .table = "mangle", |
| 143 | .checkentry = ttl_tg_check, |
| 144 | .me = THIS_MODULE, |
| 145 | }, |
| 146 | { |
| 147 | .name = "HL", |
| 148 | .revision = 0, |
| 149 | .family = NFPROTO_IPV6, |
| 150 | .target = hl_tg6, |
| 151 | .targetsize = sizeof(struct ip6t_HL_info), |
| 152 | .table = "mangle", |
| 153 | .checkentry = hl_tg6_check, |
| 154 | .me = THIS_MODULE, |
| 155 | }, |
| 156 | }; |
| 157 | |
| 158 | static int __init hl_tg_init(void) |
| 159 | { |
| 160 | return xt_register_targets(hl_tg_reg, ARRAY_SIZE(hl_tg_reg)); |
| 161 | } |
| 162 | |
| 163 | static void __exit hl_tg_exit(void) |
| 164 | { |
| 165 | xt_unregister_targets(hl_tg_reg, ARRAY_SIZE(hl_tg_reg)); |
| 166 | } |
| 167 | |
| 168 | module_init(hl_tg_init); |
| 169 | module_exit(hl_tg_exit); |
| 170 | MODULE_ALIAS("ipt_TTL"); |
| 171 | MODULE_ALIAS("ip6t_HL"); |