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   1 /*
   2  *  ebt_among
   3  *
   4  *      Authors:
   5  *      Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
   6  *
   7  *  August, 2003
   8  *
   9  */
  10
  11 #include <linux/netfilter_bridge/ebtables.h>
  12 #include <linux/netfilter_bridge/ebt_among.h>
  13 #include <linux/ip.h>
  14 #include <linux/if_arp.h>
  15 #include <linux/module.h>
  16
  17 static int ebt_mac_wormhash_contains(const struct ebt_mac_wormhash *wh,
  18                                      const char *mac, __be32 ip)
  19 {
  20         /* You may be puzzled as to how this code works.
  21          * Some tricks were used, refer to
  22          *      include/linux/netfilter_bridge/ebt_among.h
  23          * as there you can find a solution of this mystery.
  24          */
  25         const struct ebt_mac_wormhash_tuple *p;
  26         int start, limit, i;
  27         uint32_t cmp[2] = { 0, 0 };
  28         int key = ((const unsigned char *)mac)[5];
  29
  30         memcpy(((char *) cmp) + 2, mac, 6);
  31         start = wh->table[key];
  32         limit = wh->table[key + 1];
  33         if (ip) {
  34                 for (i = start; i < limit; i++) {
  35                         p = &wh->pool[i];
  36                         if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0]) {
  37                                 if (p->ip == 0 || p->ip == ip) {
  38                                         return 1;
  39                                 }
  40                         }
  41                 }
  42         } else {
  43                 for (i = start; i < limit; i++) {
  44                         p = &wh->pool[i];
  45                         if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0]) {
  46                                 if (p->ip == 0) {
  47                                         return 1;
  48                                 }
  49                         }
  50                 }
  51         }
  52         return 0;
  53 }
  54
  55 static int ebt_mac_wormhash_check_integrity(const struct ebt_mac_wormhash
  56                                             *wh)
  57 {
  58         int i;
  59
  60         for (i = 0; i < 256; i++) {
  61                 if (wh->table[i] > wh->table[i + 1])
  62                         return -0x100 - i;
  63                 if (wh->table[i] < 0)
  64                         return -0x200 - i;
  65                 if (wh->table[i] > wh->poolsize)
  66                         return -0x300 - i;
  67         }
  68         if (wh->table[256] > wh->poolsize)
  69                 return -0xc00;
  70         return 0;
  71 }
  72
  73 static int get_ip_dst(const struct sk_buff *skb, __be32 *addr)
  74 {
  75         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
  76                 const struct iphdr *ih;
  77                 struct iphdr _iph;
  78
  79                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
  80                 if (ih == NULL)
  81                         return -1;
  82                 *addr = ih->daddr;
  83         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
  84                 const struct arphdr *ah;
  85                 struct arphdr _arph;
  86                 const __be32 *bp;
  87                 __be32 buf;
  88
  89                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
  90                 if (ah == NULL ||
  91                     ah->ar_pln != sizeof(__be32) ||
  92                     ah->ar_hln != ETH_ALEN)
  93                         return -1;
  94                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
  95                                         2 * ETH_ALEN + sizeof(__be32),
  96                                         sizeof(__be32), &buf);
  97                 if (bp == NULL)
  98                         return -1;
  99                 *addr = *bp;
 100         }
 101         return 0;
 102 }
 103
 104 static int get_ip_src(const struct sk_buff *skb, __be32 *addr)
 105 {
 106         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
 107                 const struct iphdr *ih;
 108                 struct iphdr _iph;
 109
 110                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
 111                 if (ih == NULL)
 112                         return -1;
 113                 *addr = ih->saddr;
 114         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
 115                 const struct arphdr *ah;
 116                 struct arphdr _arph;
 117                 const __be32 *bp;
 118                 __be32 buf;
 119
 120                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
 121                 if (ah == NULL ||
 122                     ah->ar_pln != sizeof(__be32) ||
 123                     ah->ar_hln != ETH_ALEN)
 124                         return -1;
 125                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
 126                                         ETH_ALEN, sizeof(__be32), &buf);
 127                 if (bp == NULL)
 128                         return -1;
 129                 *addr = *bp;
 130         }
 131         return 0;
 132 }
 133
 134 static int ebt_filter_among(const struct sk_buff *skb,
 135                             const struct net_device *in,
 136                             const struct net_device *out, const void *data,
 137                             unsigned int datalen)
 138 {
 139         const struct ebt_among_info *info = data;
 140         const char *dmac, *smac;
 141         const struct ebt_mac_wormhash *wh_dst, *wh_src;
 142         __be32 dip = 0, sip = 0;
 143
 144         wh_dst = ebt_among_wh_dst(info);
 145         wh_src = ebt_among_wh_src(info);
 146
 147         if (wh_src) {
 148                 smac = eth_hdr(skb)->h_source;
 149                 if (get_ip_src(skb, &sip))
 150                         return EBT_NOMATCH;
 151                 if (!(info->bitmask & EBT_AMONG_SRC_NEG)) {
 152                         /* we match only if it contains */
 153                         if (!ebt_mac_wormhash_contains(wh_src, smac, sip))
 154                                 return EBT_NOMATCH;
 155                 } else {
 156                         /* we match only if it DOES NOT contain */
 157                         if (ebt_mac_wormhash_contains(wh_src, smac, sip))
 158                                 return EBT_NOMATCH;
 159                 }
 160         }
 161
 162         if (wh_dst) {
 163                 dmac = eth_hdr(skb)->h_dest;
 164                 if (get_ip_dst(skb, &dip))
 165                         return EBT_NOMATCH;
 166                 if (!(info->bitmask & EBT_AMONG_DST_NEG)) {
 167                         /* we match only if it contains */
 168                         if (!ebt_mac_wormhash_contains(wh_dst, dmac, dip))
 169                                 return EBT_NOMATCH;
 170                 } else {
 171                         /* we match only if it DOES NOT contain */
 172                         if (ebt_mac_wormhash_contains(wh_dst, dmac, dip))
 173                                 return EBT_NOMATCH;
 174                 }
 175         }
 176
 177         return EBT_MATCH;
 178 }
 179
 180 static int ebt_among_check(const char *tablename, unsigned int hookmask,
 181                            const struct ebt_entry *e, void *data,
 182                            unsigned int datalen)
 183 {
 184         const struct ebt_among_info *info = data;
 185         int expected_length = sizeof(struct ebt_among_info);
 186         const struct ebt_mac_wormhash *wh_dst, *wh_src;
 187         int err;
 188
 189         wh_dst = ebt_among_wh_dst(info);
 190         wh_src = ebt_among_wh_src(info);
 191         expected_length += ebt_mac_wormhash_size(wh_dst);
 192         expected_length += ebt_mac_wormhash_size(wh_src);
 193
 194         if (datalen != EBT_ALIGN(expected_length)) {
 195                 printk(KERN_WARNING
 196                        "ebtables: among: wrong size: %d "
 197                        "against expected %d, rounded to %Zd\n",
 198                        datalen, expected_length,
 199                        EBT_ALIGN(expected_length));
 200                 return -EINVAL;
 201         }
 202         if (wh_dst && (err = ebt_mac_wormhash_check_integrity(wh_dst))) {
 203                 printk(KERN_WARNING
 204                        "ebtables: among: dst integrity fail: %x\n", -err);
 205                 return -EINVAL;
 206         }
 207         if (wh_src && (err = ebt_mac_wormhash_check_integrity(wh_src))) {
 208                 printk(KERN_WARNING
 209                        "ebtables: among: src integrity fail: %x\n", -err);
 210                 return -EINVAL;
 211         }
 212         return 0;
 213 }
 214
 215 static struct ebt_match filter_among __read_mostly = {
 216         .name           = EBT_AMONG_MATCH,
 217         .match          = ebt_filter_among,
 218         .check          = ebt_among_check,
 219         .matchsize      = -1, /* special case */
 220         .me             = THIS_MODULE,
 221 };
 222
 223 static int __init ebt_among_init(void)
 224 {
 225         return ebt_register_match(&filter_among);
 226 }
 227
 228 static void __exit ebt_among_fini(void)
 229 {
 230         ebt_unregister_match(&filter_among);
 231 }
 232
 233 module_init(ebt_among_init);
 234 module_exit(ebt_among_fini);
 235 MODULE_DESCRIPTION("Ebtables: Combined MAC/IP address list matching");
 236 MODULE_LICENSE("GPL");