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DEFINITIONS
This source file includes following definitions.
- ebt_mac_wormhash_contains
- ebt_mac_wormhash_check_integrity
- get_ip_dst
- get_ip_src
- ebt_among_mt
- ebt_among_mt_check
- ebt_among_init
- ebt_among_fini
/*
* ebt_among
*
* Authors:
* Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
*
* August, 2003
*
*/
#include <linux/ip.h>
#include <linux/if_arp.h>
#include <linux/module.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_among.h>
static bool ebt_mac_wormhash_contains(const struct ebt_mac_wormhash *wh,
const char *mac, __be32 ip)
{
/* You may be puzzled as to how this code works.
* Some tricks were used, refer to
* include/linux/netfilter_bridge/ebt_among.h
* as there you can find a solution of this mystery.
*/
const struct ebt_mac_wormhash_tuple *p;
int start, limit, i;
uint32_t cmp[2] = { 0, 0 };
int key = ((const unsigned char *)mac)[5];
memcpy(((char *) cmp) + 2, mac, 6);
start = wh->table[key];
limit = wh->table[key + 1];
if (ip) {
for (i = start; i < limit; i++) {
p = &wh->pool[i];
if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0])
if (p->ip == 0 || p->ip == ip)
return true;
}
} else {
for (i = start; i < limit; i++) {
p = &wh->pool[i];
if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0])
if (p->ip == 0)
return true;
}
}
return false;
}
static int ebt_mac_wormhash_check_integrity(const struct ebt_mac_wormhash
*wh)
{
int i;
for (i = 0; i < 256; i++) {
if (wh->table[i] > wh->table[i + 1])
return -0x100 - i;
if (wh->table[i] < 0)
return -0x200 - i;
if (wh->table[i] > wh->poolsize)
return -0x300 - i;
}
if (wh->table[256] > wh->poolsize)
return -0xc00;
return 0;
}
static int get_ip_dst(const struct sk_buff *skb, __be32 *addr)
{
if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
const struct iphdr *ih;
struct iphdr _iph;
ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
if (ih == NULL)
return -1;
*addr = ih->daddr;
} else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
const struct arphdr *ah;
struct arphdr _arph;
const __be32 *bp;
__be32 buf;
ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
if (ah == NULL ||
ah->ar_pln != sizeof(__be32) ||
ah->ar_hln != ETH_ALEN)
return -1;
bp = skb_header_pointer(skb, sizeof(struct arphdr) +
2 * ETH_ALEN + sizeof(__be32),
sizeof(__be32), &buf);
if (bp == NULL)
return -1;
*addr = *bp;
}
return 0;
}
static int get_ip_src(const struct sk_buff *skb, __be32 *addr)
{
if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
const struct iphdr *ih;
struct iphdr _iph;
ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
if (ih == NULL)
return -1;
*addr = ih->saddr;
} else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
const struct arphdr *ah;
struct arphdr _arph;
const __be32 *bp;
__be32 buf;
ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
if (ah == NULL ||
ah->ar_pln != sizeof(__be32) ||
ah->ar_hln != ETH_ALEN)
return -1;
bp = skb_header_pointer(skb, sizeof(struct arphdr) +
ETH_ALEN, sizeof(__be32), &buf);
if (bp == NULL)
return -1;
*addr = *bp;
}
return 0;
}
static bool
ebt_among_mt(const struct sk_buff *skb, const struct xt_match_param *par)
{
const struct ebt_among_info *info = par->matchinfo;
const char *dmac, *smac;
const struct ebt_mac_wormhash *wh_dst, *wh_src;
__be32 dip = 0, sip = 0;
wh_dst = ebt_among_wh_dst(info);
wh_src = ebt_among_wh_src(info);
if (wh_src) {
smac = eth_hdr(skb)->h_source;
if (get_ip_src(skb, &sip))
return false;
if (!(info->bitmask & EBT_AMONG_SRC_NEG)) {
/* we match only if it contains */
if (!ebt_mac_wormhash_contains(wh_src, smac, sip))
return false;
} else {
/* we match only if it DOES NOT contain */
if (ebt_mac_wormhash_contains(wh_src, smac, sip))
return false;
}
}
if (wh_dst) {
dmac = eth_hdr(skb)->h_dest;
if (get_ip_dst(skb, &dip))
return false;
if (!(info->bitmask & EBT_AMONG_DST_NEG)) {
/* we match only if it contains */
if (!ebt_mac_wormhash_contains(wh_dst, dmac, dip))
return false;
} else {
/* we match only if it DOES NOT contain */
if (ebt_mac_wormhash_contains(wh_dst, dmac, dip))
return false;
}
}
return true;
}
static bool ebt_among_mt_check(const struct xt_mtchk_param *par)
{
const struct ebt_among_info *info = par->matchinfo;
const struct ebt_entry_match *em =
container_of(par->matchinfo, const struct ebt_entry_match, data);
int expected_length = sizeof(struct ebt_among_info);
const struct ebt_mac_wormhash *wh_dst, *wh_src;
int err;
wh_dst = ebt_among_wh_dst(info);
wh_src = ebt_among_wh_src(info);
expected_length += ebt_mac_wormhash_size(wh_dst);
expected_length += ebt_mac_wormhash_size(wh_src);
if (em->match_size != EBT_ALIGN(expected_length)) {
printk(KERN_WARNING
"ebtables: among: wrong size: %d "
"against expected %d, rounded to %Zd\n",
em->match_size, expected_length,
EBT_ALIGN(expected_length));
return false;
}
if (wh_dst && (err = ebt_mac_wormhash_check_integrity(wh_dst))) {
printk(KERN_WARNING
"ebtables: among: dst integrity fail: %x\n", -err);
return false;
}
if (wh_src && (err = ebt_mac_wormhash_check_integrity(wh_src))) {
printk(KERN_WARNING
"ebtables: among: src integrity fail: %x\n", -err);
return false;
}
return true;
}
static struct xt_match ebt_among_mt_reg __read_mostly = {
.name = "among",
.revision = 0,
.family = NFPROTO_BRIDGE,
.match = ebt_among_mt,
.checkentry = ebt_among_mt_check,
.matchsize = -1, /* special case */
.me = THIS_MODULE,
};
static int __init ebt_among_init(void)
{
return xt_register_match(&ebt_among_mt_reg);
}
static void __exit ebt_among_fini(void)
{
xt_unregister_match(&ebt_among_mt_reg);
}
module_init(ebt_among_init);
module_exit(ebt_among_fini);
MODULE_DESCRIPTION("Ebtables: Combined MAC/IP address list matching");
MODULE_LICENSE("GPL");