1/* iptables module for the packet checksum mangling
2 *
3 * (C) 2002 by Harald Welte <laforge@netfilter.org>
4 * (C) 2010 Red Hat, Inc.
5 *
6 * Author: Michael S. Tsirkin <mst@redhat.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11*/
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13#include <linux/module.h>
14#include <linux/skbuff.h>
15
16#include <linux/netfilter/x_tables.h>
17#include <linux/netfilter/xt_CHECKSUM.h>
18
19MODULE_LICENSE("GPL");
20MODULE_AUTHOR("Michael S. Tsirkin <mst@redhat.com>");
21MODULE_DESCRIPTION("Xtables: checksum modification");
22MODULE_ALIAS("ipt_CHECKSUM");
23MODULE_ALIAS("ip6t_CHECKSUM");
24
25static unsigned int
26checksum_tg(struct sk_buff *skb, const struct xt_action_param *par)
27{
28	if (skb->ip_summed == CHECKSUM_PARTIAL)
29		skb_checksum_help(skb);
30
31	return XT_CONTINUE;
32}
33
34static int checksum_tg_check(const struct xt_tgchk_param *par)
35{
36	const struct xt_CHECKSUM_info *einfo = par->targinfo;
37
38	if (einfo->operation & ~XT_CHECKSUM_OP_FILL) {
39		pr_info("unsupported CHECKSUM operation %x\n", einfo->operation);
40		return -EINVAL;
41	}
42	if (!einfo->operation) {
43		pr_info("no CHECKSUM operation enabled\n");
44		return -EINVAL;
45	}
46	return 0;
47}
48
49static struct xt_target checksum_tg_reg __read_mostly = {
50	.name		= "CHECKSUM",
51	.family		= NFPROTO_UNSPEC,
52	.target		= checksum_tg,
53	.targetsize	= sizeof(struct xt_CHECKSUM_info),
54	.table		= "mangle",
55	.checkentry	= checksum_tg_check,
56	.me		= THIS_MODULE,
57};
58
59static int __init checksum_tg_init(void)
60{
61	return xt_register_target(&checksum_tg_reg);
62}
63
64static void __exit checksum_tg_exit(void)
65{
66	xt_unregister_target(&checksum_tg_reg);
67}
68
69module_init(checksum_tg_init);
70module_exit(checksum_tg_exit);
71