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