linux/net/netfilter/xt_CHECKSUM.c
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   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
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