net/ipv4/netfilter/ipt_NOTRACK.c

   1 /* This is a module which is used for setting up fake conntracks
   2  * on packets so that they are not seen by the conntrack/NAT code.
   3  */
   4 #include <linux/module.h>
   5 #include <linux/skbuff.h>
   6
   7 #include <linux/netfilter_ipv4/ip_tables.h>
   8 #include <linux/netfilter_ipv4/ip_conntrack.h>
   9
  10 static unsigned int
  11 target(struct sk_buff **pskb,
  12        const struct net_device *in,
  13        const struct net_device *out,
  14        unsigned int hooknum,
  15        const void *targinfo,
  16        void *userinfo)
  17 {
  18         /* Previously seen (loopback)? Ignore. */
  19         if ((*pskb)->nfct != NULL)
  20                 return IPT_CONTINUE;
  21
  22         /* Attach fake conntrack entry.
  23            If there is a real ct entry correspondig to this packet,
  24            it'll hang aroun till timing out. We don't deal with it
  25            for performance reasons. JK */
  26         (*pskb)->nfct = &ip_conntrack_untracked.ct_general;
  27         (*pskb)->nfctinfo = IP_CT_NEW;
  28         nf_conntrack_get((*pskb)->nfct);
  29
  30         return IPT_CONTINUE;
  31 }
  32
  33 static int
  34 checkentry(const char *tablename,
  35            const struct ipt_entry *e,
  36            void *targinfo,
  37            unsigned int targinfosize,
  38            unsigned int hook_mask)
  39 {
  40         if (targinfosize != 0) {
  41                 printk(KERN_WARNING "NOTRACK: targinfosize %u != 0\n",
  42                        targinfosize);
  43                 return 0;
  44         }
  45
  46         if (strcmp(tablename, "raw") != 0) {
  47                 printk(KERN_WARNING "NOTRACK: can only be called from \"raw\" table, not \"%s\"\n", tablename);
  48                 return 0;
  49         }
  50
  51         return 1;
  52 }
  53
  54 static struct ipt_target ipt_notrack_reg = {
  55         .name = "NOTRACK",
  56         .target = target,
  57         .checkentry = checkentry,
  58         .me = THIS_MODULE
  59 };
  60
  61 static int __init init(void)
  62 {
  63         if (ipt_register_target(&ipt_notrack_reg))
  64                 return -EINVAL;
  65
  66         return 0;
  67 }
  68
  69 static void __exit fini(void)
  70 {
  71         ipt_unregister_target(&ipt_notrack_reg);
  72 }
  73
  74 module_init(init);
  75 module_exit(fini);
  76 MODULE_LICENSE("GPL");