net/netfilter/xt_CHECKSUM.c

   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
  19 MODULE_LICENSE("GPL");
  20 MODULE_AUTHOR("Michael S. Tsirkin <mst@redhat.com>");
  21 MODULE_DESCRIPTION("Xtables: checksum modification");
  22 MODULE_ALIAS("ipt_CHECKSUM");
  23 MODULE_ALIAS("ip6t_CHECKSUM");
  24
  25 static unsigned int
  26 checksum_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
  34 static 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
  49 static 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
  59 static int __init checksum_tg_init(void)
  60 {
  61         return xt_register_target(&checksum_tg_reg);
  62 }
  63
  64 static void __exit checksum_tg_exit(void)
  65 {
  66         xt_unregister_target(&checksum_tg_reg);
  67 }
  68
  69 module_init(checksum_tg_init);
  70 module_exit(checksum_tg_exit);