net/ipv6/netfilter/ip6t_ipv6header.c

   1 /* ipv6header match - matches IPv6 packets based
   2    on whether they contain certain headers */
   3
   4 /* Original idea: Brad Chapman
   5  * Rewritten by: Andras Kis-Szabo <kisza@sch.bme.hu> */
   6
   7 /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/ipv6.h>
  17 #include <linux/types.h>
  18 #include <net/checksum.h>
  19 #include <net/ipv6.h>
  20
  21 #include <linux/netfilter/x_tables.h>
  22 #include <linux/netfilter_ipv6/ip6_tables.h>
  23 #include <linux/netfilter_ipv6/ip6t_ipv6header.h>
  24
  25 MODULE_LICENSE("GPL");
  26 MODULE_DESCRIPTION("Xtables: IPv6 header types match");
  27 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  28
  29 static bool
  30 ipv6header_mt6(const struct sk_buff *skb, const struct net_device *in,
  31                const struct net_device *out, const struct xt_match *match,
  32                const void *matchinfo, int offset, unsigned int protoff,
  33                bool *hotdrop)
  34 {
  35         const struct ip6t_ipv6header_info *info = matchinfo;
  36         unsigned int temp;
  37         int len;
  38         u8 nexthdr;
  39         unsigned int ptr;
  40
  41         /* Make sure this isn't an evil packet */
  42
  43         /* type of the 1st exthdr */
  44         nexthdr = ipv6_hdr(skb)->nexthdr;
  45         /* pointer to the 1st exthdr */
  46         ptr = sizeof(struct ipv6hdr);
  47         /* available length */
  48         len = skb->len - ptr;
  49         temp = 0;
  50
  51         while (ip6t_ext_hdr(nexthdr)) {
  52                 struct ipv6_opt_hdr _hdr, *hp;
  53                 int hdrlen;
  54
  55                 /* Is there enough space for the next ext header? */
  56                 if (len < (int)sizeof(struct ipv6_opt_hdr))
  57                         return false;
  58                 /* No more exthdr -> evaluate */
  59                 if (nexthdr == NEXTHDR_NONE) {
  60                         temp |= MASK_NONE;
  61                         break;
  62                 }
  63                 /* ESP -> evaluate */
  64                 if (nexthdr == NEXTHDR_ESP) {
  65                         temp |= MASK_ESP;
  66                         break;
  67                 }
  68
  69                 hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
  70                 BUG_ON(hp == NULL);
  71
  72                 /* Calculate the header length */
  73                 if (nexthdr == NEXTHDR_FRAGMENT)
  74                         hdrlen = 8;
  75                 else if (nexthdr == NEXTHDR_AUTH)
  76                         hdrlen = (hp->hdrlen + 2) << 2;
  77                 else
  78                         hdrlen = ipv6_optlen(hp);
  79
  80                 /* set the flag */
  81                 switch (nexthdr) {
  82                 case NEXTHDR_HOP:
  83                         temp |= MASK_HOPOPTS;
  84                         break;
  85                 case NEXTHDR_ROUTING:
  86                         temp |= MASK_ROUTING;
  87                         break;
  88                 case NEXTHDR_FRAGMENT:
  89                         temp |= MASK_FRAGMENT;
  90                         break;
  91                 case NEXTHDR_AUTH:
  92                         temp |= MASK_AH;
  93                         break;
  94                 case NEXTHDR_DEST:
  95                         temp |= MASK_DSTOPTS;
  96                         break;
  97                 default:
  98                         return false;
  99                         break;
 100                 }
 101
 102                 nexthdr = hp->nexthdr;
 103                 len -= hdrlen;
 104                 ptr += hdrlen;
 105                 if (ptr > skb->len)
 106                         break;
 107         }
 108
 109         if (nexthdr != NEXTHDR_NONE && nexthdr != NEXTHDR_ESP)
 110                 temp |= MASK_PROTO;
 111
 112         if (info->modeflag)
 113                 return !((temp ^ info->matchflags ^ info->invflags)
 114                          & info->matchflags);
 115         else {
 116                 if (info->invflags)
 117                         return temp != info->matchflags;
 118                 else
 119                         return temp == info->matchflags;
 120         }
 121 }
 122
 123 static bool
 124 ipv6header_mt6_check(const char *tablename, const void *ip,
 125                      const struct xt_match *match, void *matchinfo,
 126                      unsigned int hook_mask)
 127 {
 128         const struct ip6t_ipv6header_info *info = matchinfo;
 129
 130         /* invflags is 0 or 0xff in hard mode */
 131         if ((!info->modeflag) && info->invflags != 0x00 &&
 132             info->invflags != 0xFF)
 133                 return false;
 134
 135         return true;
 136 }
 137
 138 static struct xt_match ipv6header_mt6_reg __read_mostly = {
 139         .name           = "ipv6header",
 140         .family         = AF_INET6,
 141         .match          = ipv6header_mt6,
 142         .matchsize      = sizeof(struct ip6t_ipv6header_info),
 143         .checkentry     = ipv6header_mt6_check,
 144         .destroy        = NULL,
 145         .me             = THIS_MODULE,
 146 };
 147
 148 static int __init ipv6header_mt6_init(void)
 149 {
 150         return xt_register_match(&ipv6header_mt6_reg);
 151 }
 152
 153 static void __exit ipv6header_mt6_exit(void)
 154 {
 155         xt_unregister_match(&ipv6header_mt6_reg);
 156 }
 157
 158 module_init(ipv6header_mt6_init);
 159 module_exit(ipv6header_mt6_exit);