net/bridge/netfilter/ebt_arpreply.c

   1 /*
   2  *  ebt_arpreply
   3  *
   4  *      Authors:
   5  *      Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
   6  *      Bart De Schuymer <bdschuym@pandora.be>
   7  *
   8  *  August, 2003
   9  *
  10  */
  11
  12 #include <linux/netfilter_bridge/ebtables.h>
  13 #include <linux/netfilter_bridge/ebt_arpreply.h>
  14 #include <linux/if_arp.h>
  15 #include <net/arp.h>
  16 #include <linux/module.h>
  17
  18 static int ebt_target_reply(struct sk_buff *skb, unsigned int hooknr,
  19    const struct net_device *in, const struct net_device *out,
  20    const void *data, unsigned int datalen)
  21 {
  22         struct ebt_arpreply_info *info = (struct ebt_arpreply_info *)data;
  23         __be32 _sip, *siptr, _dip, *diptr;
  24         struct arphdr _ah, *ap;
  25         unsigned char _sha[ETH_ALEN], *shp;
  26
  27         ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
  28         if (ap == NULL)
  29                 return EBT_DROP;
  30
  31         if (ap->ar_op != htons(ARPOP_REQUEST) ||
  32             ap->ar_hln != ETH_ALEN ||
  33             ap->ar_pro != htons(ETH_P_IP) ||
  34             ap->ar_pln != 4)
  35                 return EBT_CONTINUE;
  36
  37         shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha);
  38         if (shp == NULL)
  39                 return EBT_DROP;
  40
  41         siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN,
  42                                    sizeof(_sip), &_sip);
  43         if (siptr == NULL)
  44                 return EBT_DROP;
  45
  46         diptr = skb_header_pointer(skb,
  47                                    sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip),
  48                                    sizeof(_dip), &_dip);
  49         if (diptr == NULL)
  50                 return EBT_DROP;
  51
  52         arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr, (struct net_device *)in,
  53                  *diptr, shp, info->mac, shp);
  54
  55         return info->target;
  56 }
  57
  58 static int ebt_target_reply_check(const char *tablename, unsigned int hookmask,
  59    const struct ebt_entry *e, void *data, unsigned int datalen)
  60 {
  61         struct ebt_arpreply_info *info = (struct ebt_arpreply_info *)data;
  62
  63         if (datalen != EBT_ALIGN(sizeof(struct ebt_arpreply_info)))
  64                 return -EINVAL;
  65         if (BASE_CHAIN && info->target == EBT_RETURN)
  66                 return -EINVAL;
  67         if (e->ethproto != htons(ETH_P_ARP) ||
  68             e->invflags & EBT_IPROTO)
  69                 return -EINVAL;
  70         CLEAR_BASE_CHAIN_BIT;
  71         if (strcmp(tablename, "nat") || hookmask & ~(1 << NF_BR_PRE_ROUTING))
  72                 return -EINVAL;
  73         return 0;
  74 }
  75
  76 static struct ebt_target reply_target =
  77 {
  78         .name           = EBT_ARPREPLY_TARGET,
  79         .target         = ebt_target_reply,
  80         .check          = ebt_target_reply_check,
  81         .me             = THIS_MODULE,
  82 };
  83
  84 static int __init ebt_arpreply_init(void)
  85 {
  86         return ebt_register_target(&reply_target);
  87 }
  88
  89 static void __exit ebt_arpreply_fini(void)
  90 {
  91         ebt_unregister_target(&reply_target);
  92 }
  93
  94 module_init(ebt_arpreply_init);
  95 module_exit(ebt_arpreply_fini);
  96 MODULE_LICENSE("GPL");