net/bridge/netfilter/ebt_among.c

   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, uint32_t 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, uint32_t *addr)
  74 {
  75         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
  76                 struct iphdr _iph, *ih;
  77
  78                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
  79                 if (ih == NULL)
  80                         return -1;
  81                 *addr = ih->daddr;
  82         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
  83                 struct arphdr _arph, *ah;
  84                 uint32_t buf, *bp;
  85
  86                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
  87                 if (ah == NULL ||
  88                     ah->ar_pln != sizeof(uint32_t) ||
  89                     ah->ar_hln != ETH_ALEN)
  90                         return -1;
  91                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
  92                                         2 * ETH_ALEN + sizeof(uint32_t),
  93                                         sizeof(uint32_t), &buf);
  94                 if (bp == NULL)
  95                         return -1;
  96                 *addr = *bp;
  97         }
  98         return 0;
  99 }
 100
 101 static int get_ip_src(const struct sk_buff *skb, uint32_t *addr)
 102 {
 103         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
 104                 struct iphdr _iph, *ih;
 105
 106                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
 107                 if (ih == NULL)
 108                         return -1;
 109                 *addr = ih->saddr;
 110         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
 111                 struct arphdr _arph, *ah;
 112                 uint32_t buf, *bp;
 113
 114                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
 115                 if (ah == NULL ||
 116                     ah->ar_pln != sizeof(uint32_t) ||
 117                     ah->ar_hln != ETH_ALEN)
 118                         return -1;
 119                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
 120                                         ETH_ALEN, sizeof(uint32_t), &buf);
 121                 if (bp == NULL)
 122                         return -1;
 123                 *addr = *bp;
 124         }
 125         return 0;
 126 }
 127
 128 static int ebt_filter_among(const struct sk_buff *skb,
 129                             const struct net_device *in,
 130                             const struct net_device *out, const void *data,
 131                             unsigned int datalen)
 132 {
 133         struct ebt_among_info *info = (struct ebt_among_info *) data;
 134         const char *dmac, *smac;
 135         const struct ebt_mac_wormhash *wh_dst, *wh_src;
 136         uint32_t dip = 0, sip = 0;
 137
 138         wh_dst = ebt_among_wh_dst(info);
 139         wh_src = ebt_among_wh_src(info);
 140
 141         if (wh_src) {
 142                 smac = eth_hdr(skb)->h_source;
 143                 if (get_ip_src(skb, &sip))
 144                         return EBT_NOMATCH;
 145                 if (!(info->bitmask & EBT_AMONG_SRC_NEG)) {
 146                         /* we match only if it contains */
 147                         if (!ebt_mac_wormhash_contains(wh_src, smac, sip))
 148                                 return EBT_NOMATCH;
 149                 } else {
 150                         /* we match only if it DOES NOT contain */
 151                         if (ebt_mac_wormhash_contains(wh_src, smac, sip))
 152                                 return EBT_NOMATCH;
 153                 }
 154         }
 155
 156         if (wh_dst) {
 157                 dmac = eth_hdr(skb)->h_dest;
 158                 if (get_ip_dst(skb, &dip))
 159                         return EBT_NOMATCH;
 160                 if (!(info->bitmask & EBT_AMONG_DST_NEG)) {
 161                         /* we match only if it contains */
 162                         if (!ebt_mac_wormhash_contains(wh_dst, dmac, dip))
 163                                 return EBT_NOMATCH;
 164                 } else {
 165                         /* we match only if it DOES NOT contain */
 166                         if (ebt_mac_wormhash_contains(wh_dst, dmac, dip))
 167                                 return EBT_NOMATCH;
 168                 }
 169         }
 170
 171         return EBT_MATCH;
 172 }
 173
 174 static int ebt_among_check(const char *tablename, unsigned int hookmask,
 175                            const struct ebt_entry *e, void *data,
 176                            unsigned int datalen)
 177 {
 178         struct ebt_among_info *info = (struct ebt_among_info *) data;
 179         int expected_length = sizeof(struct ebt_among_info);
 180         const struct ebt_mac_wormhash *wh_dst, *wh_src;
 181         int err;
 182
 183         wh_dst = ebt_among_wh_dst(info);
 184         wh_src = ebt_among_wh_src(info);
 185         expected_length += ebt_mac_wormhash_size(wh_dst);
 186         expected_length += ebt_mac_wormhash_size(wh_src);
 187
 188         if (datalen != EBT_ALIGN(expected_length)) {
 189                 printk(KERN_WARNING
 190                        "ebtables: among: wrong size: %d"
 191                        "against expected %d, rounded to %Zd\n",
 192                        datalen, expected_length,
 193                        EBT_ALIGN(expected_length));
 194                 return -EINVAL;
 195         }
 196         if (wh_dst && (err = ebt_mac_wormhash_check_integrity(wh_dst))) {
 197                 printk(KERN_WARNING
 198                        "ebtables: among: dst integrity fail: %x\n", -err);
 199                 return -EINVAL;
 200         }
 201         if (wh_src && (err = ebt_mac_wormhash_check_integrity(wh_src))) {
 202                 printk(KERN_WARNING
 203                        "ebtables: among: src integrity fail: %x\n", -err);
 204                 return -EINVAL;
 205         }
 206         return 0;
 207 }
 208
 209 static struct ebt_match filter_among = {
 210         .name           = EBT_AMONG_MATCH,
 211         .match          = ebt_filter_among,
 212         .check          = ebt_among_check,
 213         .me             = THIS_MODULE,
 214 };
 215
 216 static int __init init(void)
 217 {
 218         return ebt_register_match(&filter_among);
 219 }
 220
 221 static void __exit fini(void)
 222 {
 223         ebt_unregister_match(&filter_among);
 224 }
 225
 226 module_init(init);
 227 module_exit(fini);
 228 MODULE_LICENSE("GPL");