net/bridge/netfilter/ebt_arp.c

   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 #include <linux/if_arp.h>
  12 #include <linux/if_ether.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_arp.h>
  17
  18 static bool
  19 ebt_arp_mt(const struct sk_buff *skb, struct xt_action_param *par)
  20 {
  21         const struct ebt_arp_info *info = par->matchinfo;
  22         const struct arphdr *ah;
  23         struct arphdr _arph;
  24
  25         ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
  26         if (ah == NULL)
  27                 return false;
  28         if (info->bitmask & EBT_ARP_OPCODE && FWINV(info->opcode !=
  29            ah->ar_op, EBT_ARP_OPCODE))
  30                 return false;
  31         if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype !=
  32            ah->ar_hrd, EBT_ARP_HTYPE))
  33                 return false;
  34         if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype !=
  35            ah->ar_pro, EBT_ARP_PTYPE))
  36                 return false;
  37
  38         if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP | EBT_ARP_GRAT)) {
  39                 const __be32 *sap, *dap;
  40                 __be32 saddr, daddr;
  41
  42                 if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
  43                         return false;
  44                 sap = skb_header_pointer(skb, sizeof(struct arphdr) +
  45                                         ah->ar_hln, sizeof(saddr),
  46                                         &saddr);
  47                 if (sap == NULL)
  48                         return false;
  49                 dap = skb_header_pointer(skb, sizeof(struct arphdr) +
  50                                         2*ah->ar_hln+sizeof(saddr),
  51                                         sizeof(daddr), &daddr);
  52                 if (dap == NULL)
  53                         return false;
  54                 if (info->bitmask & EBT_ARP_SRC_IP &&
  55                     FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP))
  56                         return false;
  57                 if (info->bitmask & EBT_ARP_DST_IP &&
  58                     FWINV(info->daddr != (*dap & info->dmsk), EBT_ARP_DST_IP))
  59                         return false;
  60                 if (info->bitmask & EBT_ARP_GRAT &&
  61                     FWINV(*dap != *sap, EBT_ARP_GRAT))
  62                         return false;
  63         }
  64
  65         if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
  66                 const unsigned char *mp;
  67                 unsigned char _mac[ETH_ALEN];
  68                 uint8_t verdict, i;
  69
  70                 if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
  71                         return false;
  72                 if (info->bitmask & EBT_ARP_SRC_MAC) {
  73                         mp = skb_header_pointer(skb, sizeof(struct arphdr),
  74                                                 sizeof(_mac), &_mac);
  75                         if (mp == NULL)
  76                                 return false;
  77                         verdict = 0;
  78                         for (i = 0; i < 6; i++)
  79                                 verdict |= (mp[i] ^ info->smaddr[i]) &
  80                                        info->smmsk[i];
  81                         if (FWINV(verdict != 0, EBT_ARP_SRC_MAC))
  82                                 return false;
  83                 }
  84
  85                 if (info->bitmask & EBT_ARP_DST_MAC) {
  86                         mp = skb_header_pointer(skb, sizeof(struct arphdr) +
  87                                                 ah->ar_hln + ah->ar_pln,
  88                                                 sizeof(_mac), &_mac);
  89                         if (mp == NULL)
  90                                 return false;
  91                         verdict = 0;
  92                         for (i = 0; i < 6; i++)
  93                                 verdict |= (mp[i] ^ info->dmaddr[i]) &
  94                                         info->dmmsk[i];
  95                         if (FWINV(verdict != 0, EBT_ARP_DST_MAC))
  96                                 return false;
  97                 }
  98         }
  99
 100         return true;
 101 }
 102
 103 static int ebt_arp_mt_check(const struct xt_mtchk_param *par)
 104 {
 105         const struct ebt_arp_info *info = par->matchinfo;
 106         const struct ebt_entry *e = par->entryinfo;
 107
 108         if ((e->ethproto != htons(ETH_P_ARP) &&
 109            e->ethproto != htons(ETH_P_RARP)) ||
 110            e->invflags & EBT_IPROTO)
 111                 return -EINVAL;
 112         if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
 113                 return -EINVAL;
 114         return 0;
 115 }
 116
 117 static struct xt_match ebt_arp_mt_reg __read_mostly = {
 118         .name           = "arp",
 119         .revision       = 0,
 120         .family         = NFPROTO_BRIDGE,
 121         .match          = ebt_arp_mt,
 122         .checkentry     = ebt_arp_mt_check,
 123         .matchsize      = sizeof(struct ebt_arp_info),
 124         .me             = THIS_MODULE,
 125 };
 126
 127 static int __init ebt_arp_init(void)
 128 {
 129         return xt_register_match(&ebt_arp_mt_reg);
 130 }
 131
 132 static void __exit ebt_arp_fini(void)
 133 {
 134         xt_unregister_match(&ebt_arp_mt_reg);
 135 }
 136
 137 module_init(ebt_arp_init);
 138 module_exit(ebt_arp_fini);
 139 MODULE_DESCRIPTION("Ebtables: ARP protocol packet match");
 140 MODULE_LICENSE("GPL");