1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * ebt_snat |
4 | * |
5 | * Authors: |
6 | * Bart De Schuymer <bdschuym@pandora.be> |
7 | * |
8 | * June, 2002 |
9 | * |
10 | */ |
11 | #include <linux/module.h> |
12 | #include <net/sock.h> |
13 | #include <linux/if_arp.h> |
14 | #include <net/arp.h> |
15 | #include <linux/netfilter.h> |
16 | #include <linux/netfilter/x_tables.h> |
17 | #include <linux/netfilter_bridge/ebtables.h> |
18 | #include <linux/netfilter_bridge/ebt_nat.h> |
19 | |
20 | static unsigned int |
21 | ebt_snat_tg(struct sk_buff *skb, const struct xt_action_param *par) |
22 | { |
23 | const struct ebt_nat_info *info = par->targinfo; |
24 | |
25 | if (skb_ensure_writable(skb, write_len: 0)) |
26 | return EBT_DROP; |
27 | |
28 | ether_addr_copy(dst: eth_hdr(skb)->h_source, src: info->mac); |
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, offset: 0, len: sizeof(_ah), buffer: &_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, offset: sizeof(_ah), from: info->mac, ETH_ALEN)) |
40 | return EBT_DROP; |
41 | } |
42 | out: |
43 | return info->target | ~EBT_VERDICT_BITS; |
44 | } |
45 | |
46 | static int ebt_snat_tg_check(const struct xt_tgchk_param *par) |
47 | { |
48 | const struct ebt_nat_info *info = par->targinfo; |
49 | int tmp; |
50 | |
51 | tmp = info->target | ~EBT_VERDICT_BITS; |
52 | if (BASE_CHAIN && tmp == EBT_RETURN) |
53 | return -EINVAL; |
54 | |
55 | if (ebt_invalid_target(target: tmp)) |
56 | return -EINVAL; |
57 | tmp = info->target | EBT_VERDICT_BITS; |
58 | if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT) |
59 | return -EINVAL; |
60 | return 0; |
61 | } |
62 | |
63 | static struct xt_target ebt_snat_tg_reg __read_mostly = { |
64 | .name = "snat" , |
65 | .revision = 0, |
66 | .family = NFPROTO_BRIDGE, |
67 | .table = "nat" , |
68 | .hooks = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_POST_ROUTING), |
69 | .target = ebt_snat_tg, |
70 | .checkentry = ebt_snat_tg_check, |
71 | .targetsize = sizeof(struct ebt_nat_info), |
72 | .me = THIS_MODULE, |
73 | }; |
74 | |
75 | static int __init ebt_snat_init(void) |
76 | { |
77 | return xt_register_target(target: &ebt_snat_tg_reg); |
78 | } |
79 | |
80 | static void __exit ebt_snat_fini(void) |
81 | { |
82 | xt_unregister_target(target: &ebt_snat_tg_reg); |
83 | } |
84 | |
85 | module_init(ebt_snat_init); |
86 | module_exit(ebt_snat_fini); |
87 | MODULE_DESCRIPTION("Ebtables: Source MAC address translation" ); |
88 | MODULE_LICENSE("GPL" ); |
89 | |