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// SPDX-License-Identifier: GPL-2.0-only
/* iptables module for the packet checksum mangling
*
* (C) 2002 by Harald Welte <laforge@netfilter.org>
* (C) 2010 Red Hat, Inc.
*
* Author: Michael S. Tsirkin <mst@redhat.com>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_CHECKSUM.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Michael S. Tsirkin <mst@redhat.com>");
MODULE_DESCRIPTION("Xtables: checksum modification");
MODULE_ALIAS("ipt_CHECKSUM");
MODULE_ALIAS("ip6t_CHECKSUM");
static unsigned int
checksum_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
if (skb->ip_summed == CHECKSUM_PARTIAL && !skb_is_gso(skb))
skb_checksum_help(skb);
return XT_CONTINUE;
}
static int checksum_tg_check(const struct xt_tgchk_param *par)
{
const struct xt_CHECKSUM_info *einfo = par->targinfo;
const struct ip6t_ip6 *i6 = par->entryinfo;
const struct ipt_ip *i4 = par->entryinfo;
if (einfo->operation & ~XT_CHECKSUM_OP_FILL) {
pr_info_ratelimited("unsupported CHECKSUM operation %x\n",
einfo->operation);
return -EINVAL;
}
if (!einfo->operation)
return -EINVAL;
switch (par->family) {
case NFPROTO_IPV4:
if (i4->proto == IPPROTO_UDP &&
(i4->invflags & XT_INV_PROTO) == 0)
return 0;
break;
case NFPROTO_IPV6:
if ((i6->flags & IP6T_F_PROTO) &&
i6->proto == IPPROTO_UDP &&
(i6->invflags & XT_INV_PROTO) == 0)
return 0;
break;
}
pr_warn_once("CHECKSUM should be avoided. If really needed, restrict with \"-p udp\" and only use in OUTPUT\n");
return 0;
}
static struct xt_target checksum_tg_reg __read_mostly = {
.name = "CHECKSUM",
.family = NFPROTO_UNSPEC,
.target = checksum_tg,
.targetsize = sizeof(struct xt_CHECKSUM_info),
.table = "mangle",
.checkentry = checksum_tg_check,
.me = THIS_MODULE,
};
static int __init checksum_tg_init(void)
{
return xt_register_target(&checksum_tg_reg);
}
static void __exit checksum_tg_exit(void)
{
xt_unregister_target(&checksum_tg_reg);
}
module_init(checksum_tg_init);
module_exit(checksum_tg_exit);
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