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 #include <linux/types.h>
  15 #include <linux/module.h>
  16 #include <net/ip.h>
  17 #include <linux/ipv6.h>
  18 #include <net/ipv6.h>
  19 #include <net/mip6.h>
  20
  21 #include <linux/netfilter/x_tables.h>
  22 #include <linux/netfilter_ipv6/ip6t_mh.h>
  23
  24 MODULE_DESCRIPTION("Xtables: IPv6 Mobility Header match");
  25 MODULE_LICENSE("GPL");
  26
  27 #ifdef DEBUG_IP_FIREWALL_USER
  28 #define duprintf(format, args...) printk(format , ## args)
  29 #else
  30 #define duprintf(format, args...)
  31 #endif
  32
  33 /* Returns 1 if the type is matched by the range, 0 otherwise */
  34 static inline bool
  35 type_match(u_int8_t min, u_int8_t max, u_int8_t type, bool invert)
  36 {
  37         return (type >= min && type <= max) ^ invert;
  38 }
  39
  40 static bool
  41 mh_mt6(const struct sk_buff *skb, const struct net_device *in,
  42        const struct net_device *out, const struct xt_match *match,
  43        const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
  44 {
  45         struct ip6_mh _mh;
  46         const struct ip6_mh *mh;
  47         const struct ip6t_mh *mhinfo = matchinfo;
  48
  49         /* Must not be a fragment. */
  50         if (offset)
  51                 return false;
  52
  53         mh = skb_header_pointer(skb, protoff, sizeof(_mh), &_mh);
  54         if (mh == NULL) {
  55                 /* We've been asked to examine this packet, and we
  56                    can't.  Hence, no choice but to drop. */
  57                 duprintf("Dropping evil MH tinygram.\n");
  58                 *hotdrop = true;
  59                 return false;
  60         }
  61
  62         if (mh->ip6mh_proto != IPPROTO_NONE) {
  63                 duprintf("Dropping invalid MH Payload Proto: %u\n",
  64                          mh->ip6mh_proto);
  65                 *hotdrop = true;
  66                 return false;
  67         }
  68
  69         return type_match(mhinfo->types[0], mhinfo->types[1], mh->ip6mh_type,
  70                           !!(mhinfo->invflags & IP6T_MH_INV_TYPE));
  71 }
  72
  73 /* Called when user tries to insert an entry of this type. */
  74 static bool
  75 mh_mt6_check(const char *tablename, const void *entry,
  76              const struct xt_match *match, void *matchinfo,
  77              unsigned int hook_mask)
  78 {
  79         const struct ip6t_mh *mhinfo = matchinfo;
  80
  81         /* Must specify no unknown invflags */
  82         return !(mhinfo->invflags & ~IP6T_MH_INV_MASK);
  83 }
  84
  85 static struct xt_match mh_mt6_reg __read_mostly = {
  86         .name           = "mh",
  87         .family         = AF_INET6,
  88         .checkentry     = mh_mt6_check,
  89         .match          = mh_mt6,
  90         .matchsize      = sizeof(struct ip6t_mh),
  91         .proto          = IPPROTO_MH,
  92         .me             = THIS_MODULE,
  93 };
  94
  95 static int __init mh_mt6_init(void)
  96 {
  97         return xt_register_match(&mh_mt6_reg);
  98 }
  99
 100 static void __exit mh_mt6_exit(void)
 101 {
 102         xt_unregister_match(&mh_mt6_reg);
 103 }
 104
 105 module_init(mh_mt6_init);
 106 module_exit(mh_mt6_exit);