net/bridge/netfilter/ebt_among.c

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