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 xt_match_param *par)
  31 {
  32         const struct ip6t_ipv6header_info *info = par->matchinfo;
  33         unsigned int temp;
  34         int len;
  35         u8 nexthdr;
  36         unsigned int ptr;
  37
  38         /* Make sure this isn't an evil packet */
  39
  40         /* type of the 1st exthdr */
  41         nexthdr = ipv6_hdr(skb)->nexthdr;
  42         /* pointer to the 1st exthdr */
  43         ptr = sizeof(struct ipv6hdr);
  44         /* available length */
  45         len = skb->len - ptr;
  46         temp = 0;
  47
  48         while (ip6t_ext_hdr(nexthdr)) {
  49                 const struct ipv6_opt_hdr *hp;
  50                 struct ipv6_opt_hdr _hdr;
  51                 int hdrlen;
  52
  53                 /* No more exthdr -> evaluate */
  54                 if (nexthdr == NEXTHDR_NONE) {
  55                         temp |= MASK_NONE;
  56                         break;
  57                 }
  58                 /* Is there enough space for the next ext header? */
  59                 if (len < (int)sizeof(struct ipv6_opt_hdr))
  60                         return false;
  61                 /* ESP -> evaluate */
  62                 if (nexthdr == NEXTHDR_ESP) {
  63                         temp |= MASK_ESP;
  64                         break;
  65                 }
  66
  67                 hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
  68                 BUG_ON(hp == NULL);
  69
  70                 /* Calculate the header length */
  71                 if (nexthdr == NEXTHDR_FRAGMENT)
  72                         hdrlen = 8;
  73                 else if (nexthdr == NEXTHDR_AUTH)
  74                         hdrlen = (hp->hdrlen + 2) << 2;
  75                 else
  76                         hdrlen = ipv6_optlen(hp);
  77
  78                 /* set the flag */
  79                 switch (nexthdr) {
  80                 case NEXTHDR_HOP:
  81                         temp |= MASK_HOPOPTS;
  82                         break;
  83                 case NEXTHDR_ROUTING:
  84                         temp |= MASK_ROUTING;
  85                         break;
  86                 case NEXTHDR_FRAGMENT:
  87                         temp |= MASK_FRAGMENT;
  88                         break;
  89                 case NEXTHDR_AUTH:
  90                         temp |= MASK_AH;
  91                         break;
  92                 case NEXTHDR_DEST:
  93                         temp |= MASK_DSTOPTS;
  94                         break;
  95                 default:
  96                         return false;
  97                         break;
  98                 }
  99
 100                 nexthdr = hp->nexthdr;
 101                 len -= hdrlen;
 102                 ptr += hdrlen;
 103                 if (ptr > skb->len)
 104                         break;
 105         }
 106
 107         if (nexthdr != NEXTHDR_NONE && nexthdr != NEXTHDR_ESP)
 108                 temp |= MASK_PROTO;
 109
 110         if (info->modeflag)
 111                 return !((temp ^ info->matchflags ^ info->invflags)
 112                          & info->matchflags);
 113         else {
 114                 if (info->invflags)
 115                         return temp != info->matchflags;
 116                 else
 117                         return temp == info->matchflags;
 118         }
 119 }
 120
 121 static bool ipv6header_mt6_check(const struct xt_mtchk_param *par)
 122 {
 123         const struct ip6t_ipv6header_info *info = par->matchinfo;
 124
 125         /* invflags is 0 or 0xff in hard mode */
 126         if ((!info->modeflag) && info->invflags != 0x00 &&
 127             info->invflags != 0xFF)
 128                 return false;
 129
 130         return true;
 131 }
 132
 133 static struct xt_match ipv6header_mt6_reg __read_mostly = {
 134         .name           = "ipv6header",
 135         .family         = NFPROTO_IPV6,
 136         .match          = ipv6header_mt6,
 137         .matchsize      = sizeof(struct ip6t_ipv6header_info),
 138         .checkentry     = ipv6header_mt6_check,
 139         .destroy        = NULL,
 140         .me             = THIS_MODULE,
 141 };
 142
 143 static int __init ipv6header_mt6_init(void)
 144 {
 145         return xt_register_match(&ipv6header_mt6_reg);
 146 }
 147
 148 static void __exit ipv6header_mt6_exit(void)
 149 {
 150         xt_unregister_match(&ipv6header_mt6_reg);
 151 }
 152
 153 module_init(ipv6header_mt6_init);
 154 module_exit(ipv6header_mt6_exit);