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

   1 /*
   2  *  ebt_snat
   3  *
   4  *      Authors:
   5  *      Bart De Schuymer <bdschuym@pandora.be>
   6  *
   7  *  June, 2002
   8  *
   9  */
  10
  11 #include <linux/netfilter.h>
  12 #include <linux/netfilter_bridge/ebtables.h>
  13 #include <linux/netfilter_bridge/ebt_nat.h>
  14 #include <linux/module.h>
  15 #include <net/sock.h>
  16 #include <linux/if_arp.h>
  17 #include <net/arp.h>
  18
  19 static int ebt_target_snat(struct sk_buff *skb, unsigned int hooknr,
  20    const struct net_device *in, const struct net_device *out,
  21    const void *data, unsigned int datalen)
  22 {
  23         struct ebt_nat_info *info = (struct ebt_nat_info *) data;
  24
  25         if (!skb_make_writable(skb, 0))
  26                 return EBT_DROP;
  27
  28         memcpy(eth_hdr(skb)->h_source, info->mac, ETH_ALEN);
  29         if (!(info->target & NAT_ARP_BIT) &&
  30             eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
  31                 struct arphdr _ah, *ap;
  32
  33                 ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
  34                 if (ap == NULL)
  35                         return EBT_DROP;
  36                 if (ap->ar_hln != ETH_ALEN)
  37                         goto out;
  38                 if (skb_store_bits(skb, sizeof(_ah), info->mac,ETH_ALEN))
  39                         return EBT_DROP;
  40         }
  41 out:
  42         return info->target | ~EBT_VERDICT_BITS;
  43 }
  44
  45 static int ebt_target_snat_check(const char *tablename, unsigned int hookmask,
  46    const struct ebt_entry *e, void *data, unsigned int datalen)
  47 {
  48         struct ebt_nat_info *info = (struct ebt_nat_info *) data;
  49         int tmp;
  50
  51         if (datalen != EBT_ALIGN(sizeof(struct ebt_nat_info)))
  52                 return -EINVAL;
  53         tmp = info->target | ~EBT_VERDICT_BITS;
  54         if (BASE_CHAIN && tmp == EBT_RETURN)
  55                 return -EINVAL;
  56         CLEAR_BASE_CHAIN_BIT;
  57         if (strcmp(tablename, "nat"))
  58                 return -EINVAL;
  59         if (hookmask & ~(1 << NF_BR_POST_ROUTING))
  60                 return -EINVAL;
  61
  62         if (tmp < -NUM_STANDARD_TARGETS || tmp >= 0)
  63                 return -EINVAL;
  64         tmp = info->target | EBT_VERDICT_BITS;
  65         if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT)
  66                 return -EINVAL;
  67         return 0;
  68 }
  69
  70 static struct ebt_target snat =
  71 {
  72         .name           = EBT_SNAT_TARGET,
  73         .target         = ebt_target_snat,
  74         .check          = ebt_target_snat_check,
  75         .me             = THIS_MODULE,
  76 };
  77
  78 static int __init ebt_snat_init(void)
  79 {
  80         return ebt_register_target(&snat);
  81 }
  82
  83 static void __exit ebt_snat_fini(void)
  84 {
  85         ebt_unregister_target(&snat);
  86 }
  87
  88 module_init(ebt_snat_init);
  89 module_exit(ebt_snat_fini);
  90 MODULE_LICENSE("GPL");