| /* |
| * ebt_snat |
| * |
| * Authors: |
| * Bart De Schuymer <bdschuym@pandora.be> |
| * |
| * June, 2002 |
| * |
| */ |
| #include <linux/module.h> |
| #include <net/sock.h> |
| #include <linux/if_arp.h> |
| #include <net/arp.h> |
| #include <linux/netfilter.h> |
| #include <linux/netfilter/x_tables.h> |
| #include <linux/netfilter_bridge/ebtables.h> |
| #include <linux/netfilter_bridge/ebt_nat.h> |
| |
| static unsigned int ebt_target_snat(struct sk_buff *skb, unsigned int hooknr, |
| const struct net_device *in, const struct net_device *out, |
| const void *data, unsigned int datalen) |
| { |
| const struct ebt_nat_info *info = data; |
| |
| if (!skb_make_writable(skb, 0)) |
| return EBT_DROP; |
| |
| memcpy(eth_hdr(skb)->h_source, info->mac, ETH_ALEN); |
| if (!(info->target & NAT_ARP_BIT) && |
| eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) { |
| const struct arphdr *ap; |
| struct arphdr _ah; |
| |
| ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah); |
| if (ap == NULL) |
| return EBT_DROP; |
| if (ap->ar_hln != ETH_ALEN) |
| goto out; |
| if (skb_store_bits(skb, sizeof(_ah), info->mac,ETH_ALEN)) |
| return EBT_DROP; |
| } |
| out: |
| return info->target | ~EBT_VERDICT_BITS; |
| } |
| |
| static bool ebt_target_snat_check(const char *tablename, unsigned int hookmask, |
| const struct ebt_entry *e, void *data, unsigned int datalen) |
| { |
| const struct ebt_nat_info *info = data; |
| int tmp; |
| |
| tmp = info->target | ~EBT_VERDICT_BITS; |
| if (BASE_CHAIN && tmp == EBT_RETURN) |
| return false; |
| CLEAR_BASE_CHAIN_BIT; |
| if (strcmp(tablename, "nat")) |
| return false; |
| if (hookmask & ~(1 << NF_BR_POST_ROUTING)) |
| return false; |
| |
| if (tmp < -NUM_STANDARD_TARGETS || tmp >= 0) |
| return false; |
| tmp = info->target | EBT_VERDICT_BITS; |
| if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT) |
| return false; |
| return true; |
| } |
| |
| static struct ebt_target snat __read_mostly = { |
| .name = EBT_SNAT_TARGET, |
| .target = ebt_target_snat, |
| .check = ebt_target_snat_check, |
| .targetsize = XT_ALIGN(sizeof(struct ebt_nat_info)), |
| .me = THIS_MODULE, |
| }; |
| |
| static int __init ebt_snat_init(void) |
| { |
| return ebt_register_target(&snat); |
| } |
| |
| static void __exit ebt_snat_fini(void) |
| { |
| ebt_unregister_target(&snat); |
| } |
| |
| module_init(ebt_snat_init); |
| module_exit(ebt_snat_fini); |
| MODULE_DESCRIPTION("Ebtables: Source MAC address translation"); |
| MODULE_LICENSE("GPL"); |