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