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("ip6t_tables match for MH");
  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 match(const struct sk_buff *skb,
  42          const struct net_device *in,
  43          const struct net_device *out,
  44          const struct xt_match *match,
  45          const void *matchinfo,
  46          int offset,
  47          unsigned int protoff,
  48          bool *hotdrop)
  49 {
  50         struct ip6_mh _mh;
  51         const struct ip6_mh *mh;
  52         const struct ip6t_mh *mhinfo = matchinfo;
  53
  54         /* Must not be a fragment. */
  55         if (offset)
  56                 return false;
  57
  58         mh = skb_header_pointer(skb, protoff, sizeof(_mh), &_mh);
  59         if (mh == NULL) {
  60                 /* We've been asked to examine this packet, and we
  61                    can't.  Hence, no choice but to drop. */
  62                 duprintf("Dropping evil MH tinygram.\n");
  63                 *hotdrop = true;
  64                 return false;
  65         }
  66
  67         if (mh->ip6mh_proto != IPPROTO_NONE) {
  68                 duprintf("Dropping invalid MH Payload Proto: %u\n",
  69                          mh->ip6mh_proto);
  70                 *hotdrop = true;
  71                 return false;
  72         }
  73
  74         return type_match(mhinfo->types[0], mhinfo->types[1], mh->ip6mh_type,
  75                           !!(mhinfo->invflags & IP6T_MH_INV_TYPE));
  76 }
  77
  78 /* Called when user tries to insert an entry of this type. */
  79 static bool
  80 mh_checkentry(const char *tablename,
  81               const void *entry,
  82               const struct xt_match *match,
  83               void *matchinfo,
  84               unsigned int hook_mask)
  85 {
  86         const struct ip6t_mh *mhinfo = matchinfo;
  87
  88         /* Must specify no unknown invflags */
  89         return !(mhinfo->invflags & ~IP6T_MH_INV_MASK);
  90 }
  91
  92 static struct xt_match mh_match __read_mostly = {
  93         .name           = "mh",
  94         .family         = AF_INET6,
  95         .checkentry     = mh_checkentry,
  96         .match          = match,
  97         .matchsize      = sizeof(struct ip6t_mh),
  98         .proto          = IPPROTO_MH,
  99         .me             = THIS_MODULE,
 100 };
 101
 102 static int __init ip6t_mh_init(void)
 103 {
 104         return xt_register_match(&mh_match);
 105 }
 106
 107 static void __exit ip6t_mh_fini(void)
 108 {
 109         xt_unregister_match(&mh_match);
 110 }
 111
 112 module_init(ip6t_mh_init);
 113 module_exit(ip6t_mh_fini);