Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* module that allows mangling of the arp payload */ |
2 | #include <linux/module.h> | |
2ca7b0ac | 3 | #include <linux/netfilter.h> |
1da177e4 LT |
4 | #include <linux/netfilter_arp/arpt_mangle.h> |
5 | #include <net/sock.h> | |
6 | ||
7 | MODULE_LICENSE("GPL"); | |
8 | MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>"); | |
9 | MODULE_DESCRIPTION("arptables arp payload mangle target"); | |
10 | ||
11 | static unsigned int | |
3db05fea | 12 | target(struct sk_buff *skb, |
c4986734 PM |
13 | const struct net_device *in, const struct net_device *out, |
14 | unsigned int hooknum, const struct xt_target *target, | |
fe1cb108 | 15 | const void *targinfo) |
1da177e4 LT |
16 | { |
17 | const struct arpt_mangle *mangle = targinfo; | |
18 | struct arphdr *arp; | |
19 | unsigned char *arpptr; | |
20 | int pln, hln; | |
21 | ||
eb1197bc | 22 | if (!skb_make_writable(skb, skb->len)) |
2ca7b0ac | 23 | return NF_DROP; |
1da177e4 | 24 | |
3db05fea HX |
25 | arp = arp_hdr(skb); |
26 | arpptr = skb_network_header(skb) + sizeof(*arp); | |
1da177e4 LT |
27 | pln = arp->ar_pln; |
28 | hln = arp->ar_hln; | |
29 | /* We assume that pln and hln were checked in the match */ | |
30 | if (mangle->flags & ARPT_MANGLE_SDEV) { | |
31 | if (ARPT_DEV_ADDR_LEN_MAX < hln || | |
3db05fea | 32 | (arpptr + hln > skb_tail_pointer(skb))) |
1da177e4 LT |
33 | return NF_DROP; |
34 | memcpy(arpptr, mangle->src_devaddr, hln); | |
35 | } | |
36 | arpptr += hln; | |
37 | if (mangle->flags & ARPT_MANGLE_SIP) { | |
38 | if (ARPT_MANGLE_ADDR_LEN_MAX < pln || | |
3db05fea | 39 | (arpptr + pln > skb_tail_pointer(skb))) |
1da177e4 LT |
40 | return NF_DROP; |
41 | memcpy(arpptr, &mangle->u_s.src_ip, pln); | |
42 | } | |
43 | arpptr += pln; | |
44 | if (mangle->flags & ARPT_MANGLE_TDEV) { | |
45 | if (ARPT_DEV_ADDR_LEN_MAX < hln || | |
3db05fea | 46 | (arpptr + hln > skb_tail_pointer(skb))) |
1da177e4 LT |
47 | return NF_DROP; |
48 | memcpy(arpptr, mangle->tgt_devaddr, hln); | |
49 | } | |
50 | arpptr += hln; | |
51 | if (mangle->flags & ARPT_MANGLE_TIP) { | |
52 | if (ARPT_MANGLE_ADDR_LEN_MAX < pln || | |
3db05fea | 53 | (arpptr + pln > skb_tail_pointer(skb))) |
1da177e4 LT |
54 | return NF_DROP; |
55 | memcpy(arpptr, &mangle->u_t.tgt_ip, pln); | |
56 | } | |
57 | return mangle->target; | |
58 | } | |
59 | ||
e1931b78 | 60 | static bool |
c4986734 | 61 | checkentry(const char *tablename, const void *e, const struct xt_target *target, |
e905a9ed | 62 | void *targinfo, unsigned int hook_mask) |
1da177e4 LT |
63 | { |
64 | const struct arpt_mangle *mangle = targinfo; | |
65 | ||
66 | if (mangle->flags & ~ARPT_MANGLE_MASK || | |
67 | !(mangle->flags & ARPT_MANGLE_MASK)) | |
e1931b78 | 68 | return false; |
1da177e4 LT |
69 | |
70 | if (mangle->target != NF_DROP && mangle->target != NF_ACCEPT && | |
71 | mangle->target != ARPT_CONTINUE) | |
e1931b78 JE |
72 | return false; |
73 | return true; | |
1da177e4 LT |
74 | } |
75 | ||
9f15c530 | 76 | static struct arpt_target arpt_mangle_reg __read_mostly = { |
aa83c1ab PM |
77 | .name = "mangle", |
78 | .target = target, | |
79 | .targetsize = sizeof(struct arpt_mangle), | |
80 | .checkentry = checkentry, | |
81 | .me = THIS_MODULE, | |
1da177e4 LT |
82 | }; |
83 | ||
65b4b4e8 | 84 | static int __init arpt_mangle_init(void) |
1da177e4 LT |
85 | { |
86 | if (arpt_register_target(&arpt_mangle_reg)) | |
87 | return -EINVAL; | |
88 | ||
89 | return 0; | |
90 | } | |
91 | ||
65b4b4e8 | 92 | static void __exit arpt_mangle_fini(void) |
1da177e4 LT |
93 | { |
94 | arpt_unregister_target(&arpt_mangle_reg); | |
95 | } | |
96 | ||
65b4b4e8 AM |
97 | module_init(arpt_mangle_init); |
98 | module_exit(arpt_mangle_fini); |