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("IPv6 headers match");
  27 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  28
  29 static int
  30 ipv6header_match(const struct sk_buff *skb,
  31                  const struct net_device *in,
  32                  const struct net_device *out,
  33                  const struct xt_match *match,
  34                  const void *matchinfo,
  35                  int offset,
  36                  unsigned int protoff,
  37                  int *hotdrop)
  38 {
  39         const struct ip6t_ipv6header_info *info = matchinfo;
  40         unsigned int temp;
  41         int len;
  42         u8 nexthdr;
  43         unsigned int ptr;
  44
  45         /* Make sure this isn't an evil packet */
  46
  47         /* type of the 1st exthdr */
  48         nexthdr = skb->nh.ipv6h->nexthdr;
  49         /* pointer to the 1st exthdr */
  50         ptr = sizeof(struct ipv6hdr);
  51         /* available length */
  52         len = skb->len - ptr;
  53         temp = 0;
  54
  55         while (ip6t_ext_hdr(nexthdr)) {
  56                 struct ipv6_opt_hdr _hdr, *hp;
  57                 int hdrlen;
  58
  59                 /* Is there enough space for the next ext header? */
  60                 if (len < (int)sizeof(struct ipv6_opt_hdr))
  61                         return 0;
  62                 /* No more exthdr -> evaluate */
  63                 if (nexthdr == NEXTHDR_NONE) {
  64                         temp |= MASK_NONE;
  65                         break;
  66                 }
  67                 /* ESP -> evaluate */
  68                 if (nexthdr == NEXTHDR_ESP) {
  69                         temp |= MASK_ESP;
  70                         break;
  71                 }
  72
  73                 hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
  74                 BUG_ON(hp == NULL);
  75
  76                 /* Calculate the header length */
  77                 if (nexthdr == NEXTHDR_FRAGMENT) {
  78                         hdrlen = 8;
  79                 } else if (nexthdr == NEXTHDR_AUTH)
  80                         hdrlen = (hp->hdrlen + 2) << 2;
  81                 else
  82                         hdrlen = ipv6_optlen(hp);
  83
  84                 /* set the flag */
  85                 switch (nexthdr) {
  86                 case NEXTHDR_HOP:
  87                         temp |= MASK_HOPOPTS;
  88                         break;
  89                 case NEXTHDR_ROUTING:
  90                         temp |= MASK_ROUTING;
  91                         break;
  92                 case NEXTHDR_FRAGMENT:
  93                         temp |= MASK_FRAGMENT;
  94                         break;
  95                 case NEXTHDR_AUTH:
  96                         temp |= MASK_AH;
  97                         break;
  98                 case NEXTHDR_DEST:
  99                         temp |= MASK_DSTOPTS;
 100                         break;
 101                 default:
 102                         return 0;
 103                         break;
 104                 }
 105
 106                 nexthdr = hp->nexthdr;
 107                 len -= hdrlen;
 108                 ptr += hdrlen;
 109                 if (ptr > skb->len)
 110                         break;
 111         }
 112
 113         if ((nexthdr != NEXTHDR_NONE) && (nexthdr != NEXTHDR_ESP))
 114                 temp |= MASK_PROTO;
 115
 116         if (info->modeflag)
 117                 return !((temp ^ info->matchflags ^ info->invflags)
 118                          & info->matchflags);
 119         else {
 120                 if (info->invflags)
 121                         return temp != info->matchflags;
 122                 else
 123                         return temp == info->matchflags;
 124         }
 125 }
 126
 127 static int
 128 ipv6header_checkentry(const char *tablename,
 129                       const void *ip,
 130                       const struct xt_match *match,
 131                       void *matchinfo,
 132                       unsigned int hook_mask)
 133 {
 134         const struct ip6t_ipv6header_info *info = matchinfo;
 135
 136         /* invflags is 0 or 0xff in hard mode */
 137         if ((!info->modeflag) && info->invflags != 0x00 &&
 138             info->invflags != 0xFF)
 139                 return 0;
 140
 141         return 1;
 142 }
 143
 144 static struct xt_match ip6t_ipv6header_match = {
 145         .name           = "ipv6header",
 146         .family         = AF_INET6,
 147         .match          = &ipv6header_match,
 148         .matchsize      = sizeof(struct ip6t_ipv6header_info),
 149         .checkentry     = &ipv6header_checkentry,
 150         .destroy        = NULL,
 151         .me             = THIS_MODULE,
 152 };
 153
 154 static int __init ipv6header_init(void)
 155 {
 156         return xt_register_match(&ip6t_ipv6header_match);
 157 }
 158
 159 static void __exit ipv6header_exit(void)
 160 {
 161         xt_unregister_match(&ip6t_ipv6header_match);
 162 }
 163
 164 module_init(ipv6header_init);
 165 module_exit(ipv6header_exit);