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