1/* 2 * ebt_snat 3 * 4 * Authors: 5 * Bart De Schuymer <bdschuym@pandora.be> 6 * 7 * June, 2002 8 * 9 */ 10 11#include <linux/netfilter_bridge/ebtables.h> 12#include <linux/netfilter_bridge/ebt_nat.h> 13#include <linux/module.h> 14#include <net/sock.h> 15#include <linux/if_arp.h> 16#include <net/arp.h> 17 18static int ebt_target_snat(struct sk_buff **pskb, unsigned int hooknr, 19 const struct net_device *in, const struct net_device *out, 20 const void *data, unsigned int datalen) 21{ 22 struct ebt_nat_info *info = (struct ebt_nat_info *) data; 23 24 if (skb_shared(*pskb) || skb_cloned(*pskb)) { 25 struct sk_buff *nskb; 26 27 nskb = skb_copy(*pskb, GFP_ATOMIC); 28 if (!nskb) 29 return NF_DROP; 30 if ((*pskb)->sk) 31 skb_set_owner_w(nskb, (*pskb)->sk); 32 kfree_skb(*pskb); 33 *pskb = nskb; 34 } 35 memcpy(eth_hdr(*pskb)->h_source, info->mac, ETH_ALEN); 36 if (!(info->target & NAT_ARP_BIT) && 37 eth_hdr(*pskb)->h_proto == htons(ETH_P_ARP)) { 38 struct arphdr _ah, *ap; 39 40 ap = skb_header_pointer(*pskb, 0, sizeof(_ah), &_ah); 41 if (ap == NULL) 42 return EBT_DROP; 43 if (ap->ar_hln != ETH_ALEN) 44 goto out; 45 if (skb_store_bits(*pskb, sizeof(_ah), info->mac,ETH_ALEN)) 46 return EBT_DROP; 47 } 48out: 49 return info->target | ~EBT_VERDICT_BITS; 50} 51 52static int ebt_target_snat_check(const char *tablename, unsigned int hookmask, 53 const struct ebt_entry *e, void *data, unsigned int datalen) 54{ 55 struct ebt_nat_info *info = (struct ebt_nat_info *) data; 56 int tmp; 57 58 if (datalen != EBT_ALIGN(sizeof(struct ebt_nat_info))) 59 return -EINVAL; 60 tmp = info->target | ~EBT_VERDICT_BITS; 61 if (BASE_CHAIN && tmp == EBT_RETURN) 62 return -EINVAL; 63 CLEAR_BASE_CHAIN_BIT; 64 if (strcmp(tablename, "nat")) 65 return -EINVAL; 66 if (hookmask & ~(1 << NF_BR_POST_ROUTING)) 67 return -EINVAL; 68 69 if (tmp < -NUM_STANDARD_TARGETS || tmp >= 0) 70 return -EINVAL; 71 tmp = info->target | EBT_VERDICT_BITS; 72 if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT) 73 return -EINVAL; 74 return 0; 75} 76 77static struct ebt_target snat = 78{ 79 .name = EBT_SNAT_TARGET, 80 .target = ebt_target_snat, 81 .check = ebt_target_snat_check, 82 .me = THIS_MODULE, 83}; 84 85static int __init ebt_snat_init(void) 86{ 87 return ebt_register_target(&snat); 88} 89 90static void __exit ebt_snat_fini(void) 91{ 92 ebt_unregister_target(&snat); 93} 94 95module_init(ebt_snat_init); 96module_exit(ebt_snat_fini); 97MODULE_LICENSE("GPL"); 98