release/src-rt-6.x/linux/linux-2.6/net/netfilter/xt_HL.c

   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,
  30        const struct net_device *in, const struct net_device *out,
  31        unsigned int hooknum, const struct xt_target *target,
  32        const void *targinfo)
  33 {
  34         struct iphdr *iph;
  35         const struct ipt_TTL_info *info = targinfo;
  36         int new_ttl;
  37
  38         if (!skb_make_writable(skb, skb->len))
  39                 return NF_DROP;
  40
  41         iph = ip_hdr(skb);
  42
  43         switch (info->mode) {
  44                 case IPT_TTL_SET:
  45                         new_ttl = info->ttl;
  46                         break;
  47                 case IPT_TTL_INC:
  48                         new_ttl = iph->ttl + info->ttl;
  49                         if (new_ttl > 255)
  50                                 new_ttl = 255;
  51                         break;
  52                 case IPT_TTL_DEC:
  53                         new_ttl = iph->ttl - info->ttl;
  54                         if (new_ttl < 0)
  55                                 new_ttl = 0;
  56                         break;
  57                 default:
  58                         new_ttl = iph->ttl;
  59                         break;
  60         }
  61
  62         if (new_ttl != iph->ttl) {
  63                 nf_csum_replace2(&iph->check, htons(iph->ttl << 8),
  64                                               htons(new_ttl << 8));
  65                 iph->ttl = new_ttl;
  66         }
  67
  68         return XT_CONTINUE;
  69 }
  70
  71 static unsigned int
  72 hl_tg6(struct sk_buff *skb,
  73        const struct net_device *in, const struct net_device *out,
  74        unsigned int hooknum, const struct xt_target *target,
  75        const void *targinfo)
  76 {
  77         struct ipv6hdr *ip6h;
  78         const struct ip6t_HL_info *info = targinfo;
  79         int new_hl;
  80
  81         if (!skb_make_writable(skb, skb->len))
  82                 return NF_DROP;
  83
  84         ip6h = ipv6_hdr(skb);
  85
  86         switch (info->mode) {
  87                 case IP6T_HL_SET:
  88                         new_hl = info->hop_limit;
  89                         break;
  90                 case IP6T_HL_INC:
  91                         new_hl = ip6h->hop_limit + info->hop_limit;
  92                         if (new_hl > 255)
  93                                 new_hl = 255;
  94                         break;
  95                 case IP6T_HL_DEC:
  96                         new_hl = ip6h->hop_limit - info->hop_limit;
  97                         if (new_hl < 0)
  98                                 new_hl = 0;
  99                         break;
 100                 default:
 101                         new_hl = ip6h->hop_limit;
 102                         break;
 103         }
 104
 105         ip6h->hop_limit = new_hl;
 106
 107         return XT_CONTINUE;
 108 }
 109
 110 static int ttl_tg_check(const char *tablename,
 111                         const void *e,
 112                         const struct xt_target *target,
 113                         void *targinfo,
 114                         unsigned int hook_mask)
 115 {
 116         const struct ipt_TTL_info *info = targinfo;
 117
 118         if (info->mode > IPT_TTL_MAXMODE) {
 119                 printk(KERN_WARNING "ipt_TTL: invalid or unknown Mode %u\n",
 120                         info->mode);
 121                 return 0;
 122         }
 123         if (info->mode != IPT_TTL_SET && info->ttl == 0)
 124                 return 0;
 125         return 1;
 126 }
 127
 128 static int hl_tg6_check(const char *tablename,
 129                         const void *e,
 130                         const struct xt_target *target,
 131                         void *targinfo,
 132                         unsigned int hook_mask)
 133 {
 134         const struct ip6t_HL_info *info = targinfo;
 135
 136         if (info->mode > IP6T_HL_MAXMODE) {
 137                 printk(KERN_WARNING "ip6t_HL: invalid or unknown Mode %u\n",
 138                         info->mode);
 139                 return 0;
 140         }
 141         if (info->mode != IP6T_HL_SET && info->hop_limit == 0) {
 142                 printk(KERN_WARNING "ip6t_HL: increment/decrement doesn't "
 143                         "make sense with value 0\n");
 144                 return 0;
 145         }
 146         return 1;
 147 }
 148
 149 static struct xt_target hl_tg_reg[] __read_mostly = {
 150         {
 151                 .name       = "TTL",
 152                 .revision   = 0,
 153                 .family     = AF_INET,
 154                 .target     = ttl_tg,
 155                 .targetsize = sizeof(struct ipt_TTL_info),
 156                 .table      = "mangle",
 157                 .checkentry = ttl_tg_check,
 158                 .me         = THIS_MODULE,
 159         },
 160         {
 161                 .name       = "HL",
 162                 .revision   = 0,
 163                 .family     = AF_INET6,
 164                 .target     = hl_tg6,
 165                 .targetsize = sizeof(struct ip6t_HL_info),
 166                 .table      = "mangle",
 167                 .checkentry = hl_tg6_check,
 168                 .me         = THIS_MODULE,
 169         },
 170 };
 171
 172 static int __init hl_tg_init(void)
 173 {
 174         return xt_register_targets(hl_tg_reg, ARRAY_SIZE(hl_tg_reg));
 175 }
 176
 177 static void __exit hl_tg_exit(void)
 178 {
 179         xt_unregister_targets(hl_tg_reg, ARRAY_SIZE(hl_tg_reg));
 180 }
 181
 182 module_init(hl_tg_init);
 183 module_exit(hl_tg_exit);
 184 MODULE_ALIAS("ipt_TTL");
 185 MODULE_ALIAS("ip6t_HL");