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