| /* |
| * ebt_among |
| * |
| * Authors: |
| * Grzegorz Borowiak <grzes@gnu.univ.gda.pl> |
| * |
| * August, 2003 |
| * |
| */ |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| #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 int 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)) { |
| pr_info("wrong size: %d against expected %d, rounded to %Zd\n", |
| em->match_size, expected_length, |
| EBT_ALIGN(expected_length)); |
| return -EINVAL; |
| } |
| if (wh_dst && (err = ebt_mac_wormhash_check_integrity(wh_dst))) { |
| pr_info("dst integrity fail: %x\n", -err); |
| return -EINVAL; |
| } |
| if (wh_src && (err = ebt_mac_wormhash_check_integrity(wh_src))) { |
| pr_info("src integrity fail: %x\n", -err); |
| return -EINVAL; |
| } |
| return 0; |
| } |
| |
| 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"); |