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 **pskb, 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         struct sk_buff *skb = *pskb;
  27
  28         ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
  29         if (ap == NULL)
  30                 return EBT_DROP;
  31
  32         if (ap->ar_op != htons(ARPOP_REQUEST) ||
  33             ap->ar_hln != ETH_ALEN ||
  34             ap->ar_pro != htons(ETH_P_IP) ||
  35             ap->ar_pln != 4)
  36                 return EBT_CONTINUE;
  37
  38         shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha);
  39         if (shp == NULL)
  40                 return EBT_DROP;
  41
  42         siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN,
  43                                    sizeof(_sip), &_sip);
  44         if (siptr == NULL)
  45                 return EBT_DROP;
  46
  47         diptr = skb_header_pointer(skb,
  48                                    sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip),
  49                                    sizeof(_dip), &_dip);
  50         if (diptr == NULL)
  51                 return EBT_DROP;
  52
  53         arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr, (struct net_device *)in,
  54                  *diptr, shp, info->mac, shp);
  55
  56         return info->target;
  57 }
  58
  59 static int ebt_target_reply_check(const char *tablename, unsigned int hookmask,
  60    const struct ebt_entry *e, void *data, unsigned int datalen)
  61 {
  62         struct ebt_arpreply_info *info = (struct ebt_arpreply_info *)data;
  63
  64         if (datalen != EBT_ALIGN(sizeof(struct ebt_arpreply_info)))
  65                 return -EINVAL;
  66         if (BASE_CHAIN && info->target == EBT_RETURN)
  67                 return -EINVAL;
  68         if (e->ethproto != htons(ETH_P_ARP) ||
  69             e->invflags & EBT_IPROTO)
  70                 return -EINVAL;
  71         CLEAR_BASE_CHAIN_BIT;
  72         if (strcmp(tablename, "nat") || hookmask & ~(1 << NF_BR_PRE_ROUTING))
  73                 return -EINVAL;
  74         return 0;
  75 }
  76
  77 static struct ebt_target reply_target =
  78 {
  79         .name           = EBT_ARPREPLY_TARGET,
  80         .target         = ebt_target_reply,
  81         .check          = ebt_target_reply_check,
  82         .me             = THIS_MODULE,
  83 };
  84
  85 static int __init ebt_arpreply_init(void)
  86 {
  87         return ebt_register_target(&reply_target);
  88 }
  89
  90 static void __exit ebt_arpreply_fini(void)
  91 {
  92         ebt_unregister_target(&reply_target);
  93 }
  94
  95 module_init(ebt_arpreply_init);
  96 module_exit(ebt_arpreply_fini);
  97 MODULE_LICENSE("GPL");