git.oblomov.eu Git - linux-2.6/blob - 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                 const struct ipv6_opt_hdr *hp;
  53                 struct ipv6_opt_hdr _hdr;
  54                 int hdrlen;
  55
  56                 /* Is there enough space for the next ext header? */
  57                 if (len < (int)sizeof(struct ipv6_opt_hdr))
  58                         return false;
  59                 /* No more exthdr -> evaluate */
  60                 if (nexthdr == NEXTHDR_NONE) {
  61                         temp |= MASK_NONE;
  62                         break;
  63                 }
  64                 /* ESP -> evaluate */
  65                 if (nexthdr == NEXTHDR_ESP) {
  66                         temp |= MASK_ESP;
  67                         break;
  68                 }
  69
  70                 hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
  71                 BUG_ON(hp == NULL);
  72
  73                 /* Calculate the header length */
  74                 if (nexthdr == NEXTHDR_FRAGMENT)
  75                         hdrlen = 8;
  76                 else if (nexthdr == NEXTHDR_AUTH)
  77                         hdrlen = (hp->hdrlen + 2) << 2;
  78                 else
  79                         hdrlen = ipv6_optlen(hp);
  80
  81                 /* set the flag */
  82                 switch (nexthdr) {
  83                 case NEXTHDR_HOP:
  84                         temp |= MASK_HOPOPTS;
  85                         break;
  86                 case NEXTHDR_ROUTING:
  87                         temp |= MASK_ROUTING;
  88                         break;
  89                 case NEXTHDR_FRAGMENT:
  90                         temp |= MASK_FRAGMENT;
  91                         break;
  92                 case NEXTHDR_AUTH:
  93                         temp |= MASK_AH;
  94                         break;
  95                 case NEXTHDR_DEST:
  96                         temp |= MASK_DSTOPTS;
  97                         break;
  98                 default:
  99                         return false;
 100                         break;
 101                 }
 102
 103                 nexthdr = hp->nexthdr;
 104                 len -= hdrlen;
 105                 ptr += hdrlen;
 106                 if (ptr > skb->len)
 107                         break;
 108         }
 109
 110         if (nexthdr != NEXTHDR_NONE && nexthdr != NEXTHDR_ESP)
 111                 temp |= MASK_PROTO;
 112
 113         if (info->modeflag)
 114                 return !((temp ^ info->matchflags ^ info->invflags)
 115                          & info->matchflags);
 116         else {
 117                 if (info->invflags)
 118                         return temp != info->matchflags;
 119                 else
 120                         return temp == info->matchflags;
 121         }
 122 }
 123
 124 static bool
 125 ipv6header_mt6_check(const char *tablename, const void *ip,
 126                      const struct xt_match *match, void *matchinfo,
 127                      unsigned int hook_mask)
 128 {
 129         const struct ip6t_ipv6header_info *info = matchinfo;
 130
 131         /* invflags is 0 or 0xff in hard mode */
 132         if ((!info->modeflag) && info->invflags != 0x00 &&
 133             info->invflags != 0xFF)
 134                 return false;
 135
 136         return true;
 137 }
 138
 139 static struct xt_match ipv6header_mt6_reg __read_mostly = {
 140         .name           = "ipv6header",
 141         .family         = AF_INET6,
 142         .match          = ipv6header_mt6,
 143         .matchsize      = sizeof(struct ip6t_ipv6header_info),
 144         .checkentry     = ipv6header_mt6_check,
 145         .destroy        = NULL,
 146         .me             = THIS_MODULE,
 147 };
 148
 149 static int __init ipv6header_mt6_init(void)
 150 {
 151         return xt_register_match(&ipv6header_mt6_reg);
 152 }
 153
 154 static void __exit ipv6header_mt6_exit(void)
 155 {
 156         xt_unregister_match(&ipv6header_mt6_reg);
 157 }
 158
 159 module_init(ipv6header_mt6_init);
 160 module_exit(ipv6header_mt6_exit);