LXR linux/net/bridge/netfilter/ebt

   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
  18static unsigned int
  19ebt_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
  60static 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
  73static 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
  85static int __init ebt_arpreply_init(void)
  86{
  87        return xt_register_target(&ebt_arpreply_tg_reg);
  88}
  89
  90static void __exit ebt_arpreply_fini(void)
  91{
  92        xt_unregister_target(&ebt_arpreply_tg_reg);
  93}
  94
  95module_init(ebt_arpreply_init);
  96module_exit(ebt_arpreply_fini);
  97MODULE_DESCRIPTION("Ebtables: ARP reply target");
  98MODULE_LICENSE("GPL");
  99