1 /*
2 * ebt_arpreply
3 *
4 * Authors:
5 * Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
6 * Bart De Schuymer <bdschuym@pandora.be>
7 *
8 * August, 2003
9 *
10 */
11 #include <linux/if_arp.h>
12 #include <net/arp.h>
13 #include <linux/module.h>
14 #include <linux/netfilter/x_tables.h>
15 #include <linux/netfilter_bridge/ebtables.h>
16 #include <linux/netfilter_bridge/ebt_arpreply.h>
17
18 static unsigned int
ebt_arpreply_tg(struct sk_buff * skb,const struct xt_action_param * par)19 ebt_arpreply_tg(struct sk_buff *skb, const struct xt_action_param *par)
20 {
21 const struct ebt_arpreply_info *info = par->targinfo;
22 const __be32 *siptr, *diptr;
23 __be32 _sip, _dip;
24 const struct arphdr *ap;
25 struct arphdr _ah;
26 const unsigned char *shp;
27 unsigned char _sha[ETH_ALEN];
28
29 ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
30 if (ap == NULL)
31 return EBT_DROP;
32
33 if (ap->ar_op != htons(ARPOP_REQUEST) ||
34 ap->ar_hln != ETH_ALEN ||
35 ap->ar_pro != htons(ETH_P_IP) ||
36 ap->ar_pln != 4)
37 return EBT_CONTINUE;
38
39 shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha);
40 if (shp == NULL)
41 return EBT_DROP;
42
43 siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN,
44 sizeof(_sip), &_sip);
45 if (siptr == NULL)
46 return EBT_DROP;
47
48 diptr = skb_header_pointer(skb,
49 sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip),
50 sizeof(_dip), &_dip);
51 if (diptr == NULL)
52 return EBT_DROP;
53
54 arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr, (struct net_device *)par->in,
55 *diptr, shp, info->mac, shp);
56
57 return info->target;
58 }
59
ebt_arpreply_tg_check(const struct xt_tgchk_param * par)60 static int ebt_arpreply_tg_check(const struct xt_tgchk_param *par)
61 {
62 const struct ebt_arpreply_info *info = par->targinfo;
63 const struct ebt_entry *e = par->entryinfo;
64
65 if (BASE_CHAIN && info->target == EBT_RETURN)
66 return -EINVAL;
67 if (e->ethproto != htons(ETH_P_ARP) ||
68 e->invflags & EBT_IPROTO)
69 return -EINVAL;
70 return 0;
71 }
72
73 static struct xt_target ebt_arpreply_tg_reg __read_mostly = {
74 .name = "arpreply",
75 .revision = 0,
76 .family = NFPROTO_BRIDGE,
77 .table = "nat",
78 .hooks = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING),
79 .target = ebt_arpreply_tg,
80 .checkentry = ebt_arpreply_tg_check,
81 .targetsize = sizeof(struct ebt_arpreply_info),
82 .me = THIS_MODULE,
83 };
84
ebt_arpreply_init(void)85 static int __init ebt_arpreply_init(void)
86 {
87 return xt_register_target(&ebt_arpreply_tg_reg);
88 }
89
ebt_arpreply_fini(void)90 static void __exit ebt_arpreply_fini(void)
91 {
92 xt_unregister_target(&ebt_arpreply_tg_reg);
93 }
94
95 module_init(ebt_arpreply_init);
96 module_exit(ebt_arpreply_fini);
97 MODULE_DESCRIPTION("Ebtables: ARP reply target");
98 MODULE_LICENSE("GPL");
99