net/netfilter/xt_length.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Kernel module to match packet length. */
   3 /* (C) 1999-2001 James Morris <jmorros@intercode.com.au>
   4  */
   5
   6 #include <linux/module.h>
   7 #include <linux/skbuff.h>
   8 #include <linux/ipv6.h>
   9 #include <net/ip.h>
  10
  11 #include <linux/netfilter/xt_length.h>
  12 #include <linux/netfilter/x_tables.h>
  13
  14 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
  15 MODULE_DESCRIPTION("Xtables: Packet length (Layer3,4,5) match");
  16 MODULE_LICENSE("GPL");
  17 MODULE_ALIAS("ipt_length");
  18 MODULE_ALIAS("ip6t_length");
  19
  20 static bool
  21 length_mt(const struct sk_buff *skb, struct xt_action_param *par)
  22 {
  23         const struct xt_length_info *info = par->matchinfo;
  24         u32 pktlen = skb_ip_totlen(skb);
  25
  26         return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
  27 }
  28
  29 static bool
  30 length_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  31 {
  32         const struct xt_length_info *info = par->matchinfo;
  33         u32 pktlen = skb->len;
  34
  35         return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
  36 }
  37
  38 static struct xt_match length_mt_reg[] __read_mostly = {
  39         {
  40                 .name           = "length",
  41                 .family         = NFPROTO_IPV4,
  42                 .match          = length_mt,
  43                 .matchsize      = sizeof(struct xt_length_info),
  44                 .me             = THIS_MODULE,
  45         },
  46         {
  47                 .name           = "length",
  48                 .family         = NFPROTO_IPV6,
  49                 .match          = length_mt6,
  50                 .matchsize      = sizeof(struct xt_length_info),
  51                 .me             = THIS_MODULE,
  52         },
  53 };
  54
  55 static int __init length_mt_init(void)
  56 {
  57         return xt_register_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
  58 }
  59
  60 static void __exit length_mt_exit(void)
  61 {
  62         xt_unregister_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
  63 }
  64
  65 module_init(length_mt_init);
  66 module_exit(length_mt_exit);