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   1 /*
   2  *  ebt_arp
   3  *
   4  *      Authors:
   5  *      Bart De Schuymer <bdschuym@pandora.be>
   6  *      Tim Gardner <timg@tpi.com>
   7  *
   8  *  April, 2002
   9  *
  10  */
  11
  12 #include <linux/netfilter_bridge/ebtables.h>
  13 #include <linux/netfilter_bridge/ebt_arp.h>
  14 #include <linux/if_arp.h>
  15 #include <linux/if_ether.h>
  16 #include <linux/module.h>
  17
  18 static int ebt_filter_arp(const struct sk_buff *skb, const struct net_device *in,
  19    const struct net_device *out, const void *data, unsigned int datalen)
  20 {
  21         struct ebt_arp_info *info = (struct ebt_arp_info *)data;
  22         struct arphdr _arph, *ah;
  23
  24         ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
  25         if (ah == NULL)
  26                 return EBT_NOMATCH;
  27         if (info->bitmask & EBT_ARP_OPCODE && FWINV(info->opcode !=
  28            ah->ar_op, EBT_ARP_OPCODE))
  29                 return EBT_NOMATCH;
  30         if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype !=
  31            ah->ar_hrd, EBT_ARP_HTYPE))
  32                 return EBT_NOMATCH;
  33         if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype !=
  34            ah->ar_pro, EBT_ARP_PTYPE))
  35                 return EBT_NOMATCH;
  36
  37         if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP)) {
  38                 __be32 saddr, daddr, *sap, *dap;
  39
  40                 if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
  41                         return EBT_NOMATCH;
  42                 sap = skb_header_pointer(skb, sizeof(struct arphdr) +
  43                                         ah->ar_hln, sizeof(saddr),
  44                                         &saddr);
  45                 if (sap == NULL)
  46                         return EBT_NOMATCH;
  47                 dap = skb_header_pointer(skb, sizeof(struct arphdr) +
  48                                         2*ah->ar_hln+sizeof(saddr),
  49                                         sizeof(daddr), &daddr);
  50                 if (dap == NULL)
  51                         return EBT_NOMATCH;
  52                 if (info->bitmask & EBT_ARP_SRC_IP &&
  53                     FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP))
  54                         return EBT_NOMATCH;
  55                 if (info->bitmask & EBT_ARP_DST_IP &&
  56                     FWINV(info->daddr != (*dap & info->dmsk), EBT_ARP_DST_IP))
  57                         return EBT_NOMATCH;
  58                 if (info->bitmask & EBT_ARP_GRAT &&
  59                     FWINV(*dap != *sap, EBT_ARP_GRAT))
  60                         return EBT_NOMATCH;
  61         }
  62
  63         if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
  64                 unsigned char _mac[ETH_ALEN], *mp;
  65                 uint8_t verdict, i;
  66
  67                 if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
  68                         return EBT_NOMATCH;
  69                 if (info->bitmask & EBT_ARP_SRC_MAC) {
  70                         mp = skb_header_pointer(skb, sizeof(struct arphdr),
  71                                                 sizeof(_mac), &_mac);
  72                         if (mp == NULL)
  73                                 return EBT_NOMATCH;
  74                         verdict = 0;
  75                         for (i = 0; i < 6; i++)
  76                                 verdict |= (mp[i] ^ info->smaddr[i]) &
  77                                        info->smmsk[i];
  78                         if (FWINV(verdict != 0, EBT_ARP_SRC_MAC))
  79                                 return EBT_NOMATCH;
  80                 }
  81
  82                 if (info->bitmask & EBT_ARP_DST_MAC) {
  83                         mp = skb_header_pointer(skb, sizeof(struct arphdr) +
  84                                                 ah->ar_hln + ah->ar_pln,
  85                                                 sizeof(_mac), &_mac);
  86                         if (mp == NULL)
  87                                 return EBT_NOMATCH;
  88                         verdict = 0;
  89                         for (i = 0; i < 6; i++)
  90                                 verdict |= (mp[i] ^ info->dmaddr[i]) &
  91                                         info->dmmsk[i];
  92                         if (FWINV(verdict != 0, EBT_ARP_DST_MAC))
  93                                 return EBT_NOMATCH;
  94                 }
  95         }
  96
  97         return EBT_MATCH;
  98 }
  99
 100 static int ebt_arp_check(const char *tablename, unsigned int hookmask,
 101    const struct ebt_entry *e, void *data, unsigned int datalen)
 102 {
 103         struct ebt_arp_info *info = (struct ebt_arp_info *)data;
 104
 105         if (datalen != EBT_ALIGN(sizeof(struct ebt_arp_info)))
 106                 return -EINVAL;
 107         if ((e->ethproto != htons(ETH_P_ARP) &&
 108            e->ethproto != htons(ETH_P_RARP)) ||
 109            e->invflags & EBT_IPROTO)
 110                 return -EINVAL;
 111         if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
 112                 return -EINVAL;
 113         return 0;
 114 }
 115
 116 static struct ebt_match filter_arp =
 117 {
 118         .name           = EBT_ARP_MATCH,
 119         .match          = ebt_filter_arp,
 120         .check          = ebt_arp_check,
 121         .me             = THIS_MODULE,
 122 };
 123
 124 static int __init ebt_arp_init(void)
 125 {
 126         return ebt_register_match(&filter_arp);
 127 }
 128
 129 static void __exit ebt_arp_fini(void)
 130 {
 131         ebt_unregister_match(&filter_arp);
 132 }
 133
 134 module_init(ebt_arp_init);
 135 module_exit(ebt_arp_fini);
 136 MODULE_LICENSE("GPL");