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ebt_arpreply.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/ether.h>
#include <getopt.h>
#include "../include/ebtables_u.h"
#include <linux/netfilter_bridge/ebt_arpreply.h>

static int mac_supplied;

#define REPLY_MAC '1'
#define REPLY_TARGET '2'
static struct option opts[] =
{
      { "arpreply-mac" ,    required_argument, 0, REPLY_MAC    },
      { "arpreply-target" , required_argument, 0, REPLY_TARGET },
      { 0 }
};

static void print_help()
{
      printf(
      "arpreply target options:\n"
      " --arpreply-mac address           : source MAC of generated reply\n"
      " --arpreply-target target         : ACCEPT, DROP, RETURN or CONTINUE\n"
      "                                    (standard target is DROP)\n");
}

static void init(struct ebt_entry_target *target)
{
      struct ebt_arpreply_info *replyinfo =
         (struct ebt_arpreply_info *)target->data;

      replyinfo->target = EBT_DROP;
      memset(replyinfo->mac, 0, ETH_ALEN);
      mac_supplied = 0;
}

#define OPT_REPLY_MAC     0x01
#define OPT_REPLY_TARGET  0x02
static int parse(int c, char **argv, int argc,
   const struct ebt_u_entry *entry, unsigned int *flags,
   struct ebt_entry_target **target)
{
      struct ebt_arpreply_info *replyinfo =
         (struct ebt_arpreply_info *)(*target)->data;
      struct ether_addr *addr;

      switch (c) {
      case REPLY_MAC:
            check_option(flags, OPT_REPLY_MAC);
            if (!(addr = ether_aton(optarg)))
                  print_error("Problem with specified "
                              "--arpreply-mac mac");
            memcpy(replyinfo->mac, addr, ETH_ALEN);
            mac_supplied = 1;
            break;
      case REPLY_TARGET:
            check_option(flags, OPT_REPLY_TARGET);
            if (FILL_TARGET(optarg, replyinfo->target))
                  print_error("Illegal --arpreply-target target");
            break;

      default:
            return 0;
      }
      return 1;
}

static void final_check(const struct ebt_u_entry *entry,
   const struct ebt_entry_target *target, const char *name,
   unsigned int hookmask, unsigned int time)
{
      struct ebt_arpreply_info *replyinfo =
         (struct ebt_arpreply_info *)target->data;

      if (entry->ethproto != ETH_P_ARP || entry->invflags & EBT_IPROTO)
            print_error("For ARP replying the protocol must be "
                        "specified as ARP");
      if (time == 0 && mac_supplied == 0)
            print_error("No arpreply mac supplied");
      if (BASE_CHAIN && replyinfo->target == EBT_RETURN)
            print_error("--arpreply-target RETURN not allowed on "
                        "base chain");
      CLEAR_BASE_CHAIN_BIT;
      if (strcmp(name, "nat") || hookmask & ~(1 << NF_BR_PRE_ROUTING))
            print_error("arpreply only allowed in PREROUTING");
}

static void print(const struct ebt_u_entry *entry,
   const struct ebt_entry_target *target)
{
      struct ebt_arpreply_info *replyinfo =
         (struct ebt_arpreply_info *)target->data;

      printf("--arpreply-mac ");
      print_mac(replyinfo->mac);
      if (replyinfo->target == EBT_DROP)
            return;
      printf(" --arpreply-target %s", TARGET_NAME(replyinfo->target));
}

static int compare(const struct ebt_entry_target *t1,
   const struct ebt_entry_target *t2)
{
      struct ebt_arpreply_info *replyinfo1 =
         (struct ebt_arpreply_info *)t1->data;
      struct ebt_arpreply_info *replyinfo2 =
         (struct ebt_arpreply_info *)t2->data;

      return memcmp(replyinfo1->mac, replyinfo2->mac, ETH_ALEN) == 0
            && replyinfo1->target == replyinfo2->target;
}

static struct ebt_u_target arpreply_target =
{
      .name       = EBT_ARPREPLY_TARGET,
      .size       = sizeof(struct ebt_arpreply_info),
      .help       = print_help,
      .init       = init,
      .parse            = parse,
      .final_check      = final_check,
      .print            = print,
      .compare    = compare,
      .extra_ops  = opts,
};

static void _init(void) __attribute__ ((constructor));
static void _init(void)
{
      register_target(&arpreply_target);
}

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