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 #include <linux/if_arp.h>
  12 #include <net/arp.h>
  13 #include <linux/module.h>
  14 #include <linux/netfilter/x_tables.h>
  15 #include <linux/netfilter_bridge/ebtables.h>
  16 #include <linux/netfilter_bridge/ebt_arpreply.h>
  17
  18 static unsigned int
  19 ebt_arpreply_tg(struct sk_buff *skb, const struct xt_target_param *par)
  20 {
  21         const struct ebt_arpreply_info *info = par->targinfo;
  22         const __be32 *siptr, *diptr;
  23         __be32 _sip, _dip;
  24         const struct arphdr *ap;
  25         struct arphdr _ah;
  26         const unsigned char *shp;
  27         unsigned char _sha[ETH_ALEN];
  28
  29         ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
  30         if (ap == NULL)
  31                 return EBT_DROP;
  32
  33         if (ap->ar_op != htons(ARPOP_REQUEST) ||
  34             ap->ar_hln != ETH_ALEN ||
  35             ap->ar_pro != htons(ETH_P_IP) ||
  36             ap->ar_pln != 4)
  37                 return EBT_CONTINUE;
  38
  39         shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha);
  40         if (shp == NULL)
  41                 return EBT_DROP;
  42
  43         siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN,
  44                                    sizeof(_sip), &_sip);
  45         if (siptr == NULL)
  46                 return EBT_DROP;
  47
  48         diptr = skb_header_pointer(skb,
  49                                    sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip),
  50                                    sizeof(_dip), &_dip);
  51         if (diptr == NULL)
  52                 return EBT_DROP;
  53
  54         arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr, (struct net_device *)par->in,
  55                  *diptr, shp, info->mac, shp);
  56
  57         return info->target;
  58 }
  59
  60 static bool ebt_arpreply_tg_check(const struct xt_tgchk_param *par)
  61 {
  62         const struct ebt_arpreply_info *info = par->targinfo;
  63         const struct ebt_entry *e = par->entryinfo;
  64
  65         if (BASE_CHAIN && info->target == EBT_RETURN)
  66                 return false;
  67         if (e->ethproto != htons(ETH_P_ARP) ||
  68             e->invflags & EBT_IPROTO)
  69                 return false;
  70         return true;
  71 }
  72
  73 static struct xt_target ebt_arpreply_tg_reg __read_mostly = {
  74         .name           = "arpreply",
  75         .revision       = 0,
  76         .family         = NFPROTO_BRIDGE,
  77         .table          = "nat",
  78         .hooks          = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING),
  79         .target         = ebt_arpreply_tg,
  80         .checkentry     = ebt_arpreply_tg_check,
  81         .targetsize     = XT_ALIGN(sizeof(struct ebt_arpreply_info)),
  82         .me             = THIS_MODULE,
  83 };
  84
  85 static int __init ebt_arpreply_init(void)
  86 {
  87         return xt_register_target(&ebt_arpreply_tg_reg);
  88 }
  89
  90 static void __exit ebt_arpreply_fini(void)
  91 {
  92         xt_unregister_target(&ebt_arpreply_tg_reg);
  93 }
  94
  95 module_init(ebt_arpreply_init);
  96 module_exit(ebt_arpreply_fini);
  97 MODULE_DESCRIPTION("Ebtables: ARP reply target");
  98 MODULE_LICENSE("GPL");