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 int
  35 type_match(u_int8_t min, u_int8_t max, u_int8_t type, int invert)
  36 {
  37         int ret;
  38
  39         ret = (type >= min && type <= max) ^ invert;
  40         return ret;
  41 }
  42
  43 static int
  44 match(const struct sk_buff *skb,
  45          const struct net_device *in,
  46          const struct net_device *out,
  47          const struct xt_match *match,
  48          const void *matchinfo,
  49          int offset,
  50          unsigned int protoff,
  51          int *hotdrop)
  52 {
  53         struct ip6_mh _mh, *mh;
  54         const struct ip6t_mh *mhinfo = matchinfo;
  55
  56         /* Must not be a fragment. */
  57         if (offset)
  58                 return 0;
  59
  60         mh = skb_header_pointer(skb, protoff, sizeof(_mh), &_mh);
  61         if (mh == NULL) {
  62                 /* We've been asked to examine this packet, and we
  63                    can't.  Hence, no choice but to drop. */
  64                 duprintf("Dropping evil MH tinygram.\n");
  65                 *hotdrop = 1;
  66                 return 0;
  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 int
  75 mh_checkentry(const char *tablename,
  76               const void *entry,
  77               const struct xt_match *match,
  78               void *matchinfo,
  79               unsigned int hook_mask)
  80 {
  81         const struct ip6t_mh *mhinfo = matchinfo;
  82
  83         /* Must specify no unknown invflags */
  84         return !(mhinfo->invflags & ~IP6T_MH_INV_MASK);
  85 }
  86
  87 static struct xt_match mh_match = {
  88         .name           = "mh",
  89         .family         = AF_INET6,
  90         .checkentry     = mh_checkentry,
  91         .match          = match,
  92         .matchsize      = sizeof(struct ip6t_mh),
  93         .proto          = IPPROTO_MH,
  94         .me             = THIS_MODULE,
  95 };
  96
  97 static int __init ip6t_mh_init(void)
  98 {
  99         return xt_register_match(&mh_match);
 100 }
 101
 102 static void __exit ip6t_mh_fini(void)
 103 {
 104         xt_unregister_match(&mh_match);
 105 }
 106
 107 module_init(ip6t_mh_init);
 108 module_exit(ip6t_mh_fini);