xt_CHECKSUM.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/* iptables module for the packet checksum mangling
  3 *
  4 * (C) 2002 by Harald Welte <laforge@netfilter.org>
  5 * (C) 2010 Red Hat, Inc.
  6 *
  7 * Author: Michael S. Tsirkin <mst@redhat.com>
  8*/
  9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 10#include <linux/module.h>
 11#include <linux/skbuff.h>
 12
 13#include <linux/netfilter/x_tables.h>
 14#include <linux/netfilter/xt_CHECKSUM.h>
 15
 16#include <linux/netfilter_ipv4/ip_tables.h>
 17#include <linux/netfilter_ipv6/ip6_tables.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 && !skb_is_gso(skb))
 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	const struct ip6t_ip6 *i6 = par->entryinfo;
 38	const struct ipt_ip *i4 = par->entryinfo;
 39
 40	if (einfo->operation & ~XT_CHECKSUM_OP_FILL) {
 41		pr_info_ratelimited("unsupported CHECKSUM operation %x\n",
 42				    einfo->operation);
 43		return -EINVAL;
 44	}
 45	if (!einfo->operation)
 46		return -EINVAL;
 47
 48	switch (par->family) {
 49	case NFPROTO_IPV4:
 50		if (i4->proto == IPPROTO_UDP &&
 51		    (i4->invflags & XT_INV_PROTO) == 0)
 52			return 0;
 53		break;
 54	case NFPROTO_IPV6:
 55		if ((i6->flags & IP6T_F_PROTO) &&
 56		    i6->proto == IPPROTO_UDP &&
 57		    (i6->invflags & XT_INV_PROTO) == 0)
 58			return 0;
 59		break;
 60	}
 61
 62	pr_warn_once("CHECKSUM should be avoided.  If really needed, restrict with \"-p udp\" and only use in OUTPUT\n");
 63	return 0;
 64}
 65
 66static struct xt_target checksum_tg_reg[] __read_mostly = {
 67	{
 68		.name		= "CHECKSUM",
 69		.family		= NFPROTO_IPV4,
 70		.target		= checksum_tg,
 71		.targetsize	= sizeof(struct xt_CHECKSUM_info),
 72		.table		= "mangle",
 73		.checkentry	= checksum_tg_check,
 74		.me		= THIS_MODULE,
 75	},
 76#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 77	{
 78		.name		= "CHECKSUM",
 79		.family		= NFPROTO_IPV6,
 80		.target		= checksum_tg,
 81		.targetsize	= sizeof(struct xt_CHECKSUM_info),
 82		.table		= "mangle",
 83		.checkentry	= checksum_tg_check,
 84		.me		= THIS_MODULE,
 85	},
 86#endif
 87};
 88
 89static int __init checksum_tg_init(void)
 90{
 91	return xt_register_targets(checksum_tg_reg, ARRAY_SIZE(checksum_tg_reg));
 92}
 93
 94static void __exit checksum_tg_exit(void)
 95{
 96	xt_unregister_targets(checksum_tg_reg, ARRAY_SIZE(checksum_tg_reg));
 97}
 98
 99module_init(checksum_tg_init);
100module_exit(checksum_tg_exit);