Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* module that allows mangling of the arp payload */ |
| 2 | #include <linux/module.h> |
Herbert Xu | 2ca7b0a | 2007-10-14 00:39:55 -0700 | [diff] [blame] | 3 | #include <linux/netfilter.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 |
Herbert Xu | 3db05fe | 2007-10-15 00:53:15 -0700 | [diff] [blame^] | 12 | target(struct sk_buff *skb, |
Patrick McHardy | c498673 | 2006-03-20 18:02:56 -0800 | [diff] [blame] | 13 | const struct net_device *in, const struct net_device *out, |
| 14 | unsigned int hooknum, const struct xt_target *target, |
Patrick McHardy | fe1cb10 | 2006-08-22 00:35:47 -0700 | [diff] [blame] | 15 | const void *targinfo) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 16 | { |
| 17 | const struct arpt_mangle *mangle = targinfo; |
| 18 | struct arphdr *arp; |
| 19 | unsigned char *arpptr; |
| 20 | int pln, hln; |
| 21 | |
Herbert Xu | 3db05fe | 2007-10-15 00:53:15 -0700 | [diff] [blame^] | 22 | if (skb_make_writable(skb, skb->len)) |
Herbert Xu | 2ca7b0a | 2007-10-14 00:39:55 -0700 | [diff] [blame] | 23 | return NF_DROP; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 24 | |
Herbert Xu | 3db05fe | 2007-10-15 00:53:15 -0700 | [diff] [blame^] | 25 | arp = arp_hdr(skb); |
| 26 | arpptr = skb_network_header(skb) + sizeof(*arp); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 || |
Herbert Xu | 3db05fe | 2007-10-15 00:53:15 -0700 | [diff] [blame^] | 32 | (arpptr + hln > skb_tail_pointer(skb))) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 || |
Herbert Xu | 3db05fe | 2007-10-15 00:53:15 -0700 | [diff] [blame^] | 39 | (arpptr + pln > skb_tail_pointer(skb))) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 || |
Herbert Xu | 3db05fe | 2007-10-15 00:53:15 -0700 | [diff] [blame^] | 46 | (arpptr + hln > skb_tail_pointer(skb))) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 || |
Herbert Xu | 3db05fe | 2007-10-15 00:53:15 -0700 | [diff] [blame^] | 53 | (arpptr + pln > skb_tail_pointer(skb))) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 54 | return NF_DROP; |
| 55 | memcpy(arpptr, &mangle->u_t.tgt_ip, pln); |
| 56 | } |
| 57 | return mangle->target; |
| 58 | } |
| 59 | |
Jan Engelhardt | e1931b7 | 2007-07-07 22:16:26 -0700 | [diff] [blame] | 60 | static bool |
Patrick McHardy | c498673 | 2006-03-20 18:02:56 -0800 | [diff] [blame] | 61 | checkentry(const char *tablename, const void *e, const struct xt_target *target, |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 62 | void *targinfo, unsigned int hook_mask) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 63 | { |
| 64 | const struct arpt_mangle *mangle = targinfo; |
| 65 | |
| 66 | if (mangle->flags & ~ARPT_MANGLE_MASK || |
| 67 | !(mangle->flags & ARPT_MANGLE_MASK)) |
Jan Engelhardt | e1931b7 | 2007-07-07 22:16:26 -0700 | [diff] [blame] | 68 | return false; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 69 | |
| 70 | if (mangle->target != NF_DROP && mangle->target != NF_ACCEPT && |
| 71 | mangle->target != ARPT_CONTINUE) |
Jan Engelhardt | e1931b7 | 2007-07-07 22:16:26 -0700 | [diff] [blame] | 72 | return false; |
| 73 | return true; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 74 | } |
| 75 | |
Patrick McHardy | 9f15c53 | 2007-07-07 22:22:02 -0700 | [diff] [blame] | 76 | static struct arpt_target arpt_mangle_reg __read_mostly = { |
Patrick McHardy | aa83c1a | 2006-03-20 18:01:28 -0800 | [diff] [blame] | 77 | .name = "mangle", |
| 78 | .target = target, |
| 79 | .targetsize = sizeof(struct arpt_mangle), |
| 80 | .checkentry = checkentry, |
| 81 | .me = THIS_MODULE, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 82 | }; |
| 83 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 84 | static int __init arpt_mangle_init(void) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 85 | { |
| 86 | if (arpt_register_target(&arpt_mangle_reg)) |
| 87 | return -EINVAL; |
| 88 | |
| 89 | return 0; |
| 90 | } |
| 91 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 92 | static void __exit arpt_mangle_fini(void) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 93 | { |
| 94 | arpt_unregister_target(&arpt_mangle_reg); |
| 95 | } |
| 96 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 97 | module_init(arpt_mangle_init); |
| 98 | module_exit(arpt_mangle_fini); |