linux/net/bridge/netfilter/ebt_among.c
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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#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
  18static 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        memcpy(((char *) cmp) + 2, mac, 6);
  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
  52static 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
  70static 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
 101static 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
 131static bool
 132ebt_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
 175static 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
 206static 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
 216static int __init ebt_among_init(void)
 217{
 218        return xt_register_match(&ebt_among_mt_reg);
 219}
 220
 221static void __exit ebt_among_fini(void)
 222{
 223        xt_unregister_match(&ebt_among_mt_reg);
 224}
 225
 226module_init(ebt_among_init);
 227module_exit(ebt_among_fini);
 228MODULE_DESCRIPTION("Ebtables: Combined MAC/IP address list matching");
 229MODULE_LICENSE("GPL");
 230