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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 | /* * TTL modification target for IP tables * (C) 2000,2005 by Harald Welte <laforge@netfilter.org> * * Hop Limit modification target for ip6tables * Maciej Soltysiak <solt@dns.toxicfilms.tv> * * 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. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <linux/ipv6.h> #include <net/checksum.h> #include <linux/netfilter/x_tables.h> #include <linux/netfilter_ipv4/ipt_TTL.h> #include <linux/netfilter_ipv6/ip6t_HL.h> MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>"); MODULE_DESCRIPTION("Xtables: Hoplimit/TTL Limit field modification target"); MODULE_LICENSE("GPL"); static unsigned int ttl_tg(struct sk_buff *skb, const struct xt_action_param *par) { struct iphdr *iph; const struct ipt_TTL_info *info = par->targinfo; int new_ttl; if (!skb_make_writable(skb, skb->len)) return NF_DROP; iph = ip_hdr(skb); 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) { csum_replace2(&iph->check, htons(iph->ttl << 8), htons(new_ttl << 8)); iph->ttl = new_ttl; } return XT_CONTINUE; } static unsigned int hl_tg6(struct sk_buff *skb, const struct xt_action_param *par) { struct ipv6hdr *ip6h; const struct ip6t_HL_info *info = par->targinfo; int new_hl; if (!skb_make_writable(skb, skb->len)) return NF_DROP; ip6h = ipv6_hdr(skb); switch (info->mode) { case IP6T_HL_SET: new_hl = info->hop_limit; break; case IP6T_HL_INC: new_hl = ip6h->hop_limit + info->hop_limit; if (new_hl > 255) new_hl = 255; break; case IP6T_HL_DEC: new_hl = ip6h->hop_limit - info->hop_limit; if (new_hl < 0) new_hl = 0; break; default: new_hl = ip6h->hop_limit; break; } ip6h->hop_limit = new_hl; return XT_CONTINUE; } static int ttl_tg_check(const struct xt_tgchk_param *par) { const struct ipt_TTL_info *info = par->targinfo; if (info->mode > IPT_TTL_MAXMODE) return -EINVAL; if (info->mode != IPT_TTL_SET && info->ttl == 0) return -EINVAL; return 0; } static int hl_tg6_check(const struct xt_tgchk_param *par) { const struct ip6t_HL_info *info = par->targinfo; if (info->mode > IP6T_HL_MAXMODE) return -EINVAL; if (info->mode != IP6T_HL_SET && info->hop_limit == 0) return -EINVAL; return 0; } static struct xt_target hl_tg_reg[] __read_mostly = { { .name = "TTL", .revision = 0, .family = NFPROTO_IPV4, .target = ttl_tg, .targetsize = sizeof(struct ipt_TTL_info), .table = "mangle", .checkentry = ttl_tg_check, .me = THIS_MODULE, }, { .name = "HL", .revision = 0, .family = NFPROTO_IPV6, .target = hl_tg6, .targetsize = sizeof(struct ip6t_HL_info), .table = "mangle", .checkentry = hl_tg6_check, .me = THIS_MODULE, }, }; static int __init hl_tg_init(void) { return xt_register_targets(hl_tg_reg, ARRAY_SIZE(hl_tg_reg)); } static void __exit hl_tg_exit(void) { xt_unregister_targets(hl_tg_reg, ARRAY_SIZE(hl_tg_reg)); } module_init(hl_tg_init); module_exit(hl_tg_exit); MODULE_ALIAS("ipt_TTL"); MODULE_ALIAS("ip6t_HL"); |