1 /* 2 * ebt_snat 3 * 4 * Authors: 5 * Bart De Schuymer <bdschuym@pandora.be> 6 * 7 * June, 2002 8 * 9 */ 10 #include <linux/module.h> 11 #include <net/sock.h> 12 #include <linux/if_arp.h> 13 #include <net/arp.h> 14 #include <linux/netfilter.h> 15 #include <linux/netfilter/x_tables.h> 16 #include <linux/netfilter_bridge/ebtables.h> 17 #include <linux/netfilter_bridge/ebt_nat.h> 18 19 static unsigned int 20 ebt_snat_tg(struct sk_buff *skb, const struct xt_action_param *par) 21 { 22 const struct ebt_nat_info *info = par->targinfo; 23 24 if (!skb_make_writable(skb, 0)) 25 return EBT_DROP; 26 27 ether_addr_copy(eth_hdr(skb)->h_source, info->mac); 28 if (!(info->target & NAT_ARP_BIT) && 29 eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) { 30 const struct arphdr *ap; 31 struct arphdr _ah; 32 33 ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah); 34 if (ap == NULL) 35 return EBT_DROP; 36 if (ap->ar_hln != ETH_ALEN) 37 goto out; 38 if (skb_store_bits(skb, sizeof(_ah), info->mac, ETH_ALEN)) 39 return EBT_DROP; 40 } 41 out: 42 return info->target | ~EBT_VERDICT_BITS; 43 } 44 45 static int ebt_snat_tg_check(const struct xt_tgchk_param *par) 46 { 47 const struct ebt_nat_info *info = par->targinfo; 48 int tmp; 49 50 tmp = info->target | ~EBT_VERDICT_BITS; 51 if (BASE_CHAIN && tmp == EBT_RETURN) 52 return -EINVAL; 53 54 if (tmp < -NUM_STANDARD_TARGETS || tmp >= 0) 55 return -EINVAL; 56 tmp = info->target | EBT_VERDICT_BITS; 57 if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT) 58 return -EINVAL; 59 return 0; 60 } 61 62 static struct xt_target ebt_snat_tg_reg __read_mostly = { 63 .name = "snat", 64 .revision = 0, 65 .family = NFPROTO_BRIDGE, 66 .table = "nat", 67 .hooks = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_POST_ROUTING), 68 .target = ebt_snat_tg, 69 .checkentry = ebt_snat_tg_check, 70 .targetsize = sizeof(struct ebt_nat_info), 71 .me = THIS_MODULE, 72 }; 73 74 static int __init ebt_snat_init(void) 75 { 76 return xt_register_target(&ebt_snat_tg_reg); 77 } 78 79 static void __exit ebt_snat_fini(void) 80 { 81 xt_unregister_target(&ebt_snat_tg_reg); 82 } 83 84 module_init(ebt_snat_init); 85 module_exit(ebt_snat_fini); 86 MODULE_DESCRIPTION("Ebtables: Source MAC address translation"); 87 MODULE_LICENSE("GPL"); 88