net/ipv6/netfilter/ip6t_mh.c

   1 /*
   2  * Copyright (C)2006 USAGI/WIDE Project
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * Author:
   9  *      Masahide NAKAMURA @USAGI <masahide.nakamura.cz@hitachi.com>
  10  *
  11  * Based on net/netfilter/xt_tcpudp.c
  12  *
  13  */
  14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15 #include <linux/types.h>
  16 #include <linux/module.h>
  17 #include <net/ip.h>
  18 #include <linux/ipv6.h>
  19 #include <net/ipv6.h>
  20 #include <net/mip6.h>
  21
  22 #include <linux/netfilter/x_tables.h>
  23 #include <linux/netfilter_ipv6/ip6t_mh.h>
  24
  25 MODULE_DESCRIPTION("Xtables: IPv6 Mobility Header match");
  26 MODULE_LICENSE("GPL");
  27
  28 /* Returns 1 if the type is matched by the range, 0 otherwise */
  29 static inline bool
  30 type_match(u_int8_t min, u_int8_t max, u_int8_t type, bool invert)
  31 {
  32         return (type >= min && type <= max) ^ invert;
  33 }
  34
  35 static bool mh_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  36 {
  37         struct ip6_mh _mh;
  38         const struct ip6_mh *mh;
  39         const struct ip6t_mh *mhinfo = par->matchinfo;
  40
  41         /* Must not be a fragment. */
  42         if (par->fragoff != 0)
  43                 return false;
  44
  45         mh = skb_header_pointer(skb, par->thoff, sizeof(_mh), &_mh);
  46         if (mh == NULL) {
  47                 /* We've been asked to examine this packet, and we
  48                    can't.  Hence, no choice but to drop. */
  49                 pr_debug("Dropping evil MH tinygram.\n");
  50                 par->hotdrop = true;
  51                 return false;
  52         }
  53
  54         if (mh->ip6mh_proto != IPPROTO_NONE) {
  55                 pr_debug("Dropping invalid MH Payload Proto: %u\n",
  56                          mh->ip6mh_proto);
  57                 par->hotdrop = true;
  58                 return false;
  59         }
  60
  61         return type_match(mhinfo->types[0], mhinfo->types[1], mh->ip6mh_type,
  62                           !!(mhinfo->invflags & IP6T_MH_INV_TYPE));
  63 }
  64
  65 static int mh_mt6_check(const struct xt_mtchk_param *par)
  66 {
  67         const struct ip6t_mh *mhinfo = par->matchinfo;
  68
  69         /* Must specify no unknown invflags */
  70         return (mhinfo->invflags & ~IP6T_MH_INV_MASK) ? -EINVAL : 0;
  71 }
  72
  73 static struct xt_match mh_mt6_reg __read_mostly = {
  74         .name           = "mh",
  75         .family         = NFPROTO_IPV6,
  76         .checkentry     = mh_mt6_check,
  77         .match          = mh_mt6,
  78         .matchsize      = sizeof(struct ip6t_mh),
  79         .proto          = IPPROTO_MH,
  80         .me             = THIS_MODULE,
  81 };
  82
  83 static int __init mh_mt6_init(void)
  84 {
  85         return xt_register_match(&mh_mt6_reg);
  86 }
  87
  88 static void __exit mh_mt6_exit(void)
  89 {
  90         xt_unregister_match(&mh_mt6_reg);
  91 }
  92
  93 module_init(mh_mt6_init);
  94 module_exit(mh_mt6_exit);