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_ipv6/ip6_tables.h>
  22 #include <linux/netfilter_ipv6/ip6t_ipv6header.h>
  23
  24 MODULE_LICENSE("GPL");
  25 MODULE_DESCRIPTION("IPv6 headers match");
  26 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  27
  28 static int
  29 ipv6header_match(const struct sk_buff *skb,
  30                  const struct net_device *in,
  31                  const struct net_device *out,
  32                  const void *matchinfo,
  33                  int offset,
  34                  unsigned int protoff,
  35                  int *hotdrop)
  36 {
  37         const struct ip6t_ipv6header_info *info = matchinfo;
  38         unsigned int temp;
  39         int len;
  40         u8 nexthdr;
  41         unsigned int ptr;
  42
  43         /* Make sure this isn't an evil packet */
  44
  45         /* type of the 1st exthdr */
  46         nexthdr = skb->nh.ipv6h->nexthdr;
  47         /* pointer to the 1st exthdr */
  48         ptr = sizeof(struct ipv6hdr);
  49         /* available length */
  50         len = skb->len - ptr;
  51         temp = 0;
  52
  53         while (ip6t_ext_hdr(nexthdr)) {
  54                 struct ipv6_opt_hdr _hdr, *hp;
  55                 int hdrlen;
  56
  57                 /* Is there enough space for the next ext header? */
  58                 if (len < (int)sizeof(struct ipv6_opt_hdr))
  59                         return 0;
  60                 /* No more exthdr -> evaluate */
  61                 if (nexthdr == NEXTHDR_NONE) {
  62                         temp |= MASK_NONE;
  63                         break;
  64                 }
  65                 /* ESP -> evaluate */
  66                 if (nexthdr == NEXTHDR_ESP) {
  67                         temp |= MASK_ESP;
  68                         break;
  69                 }
  70
  71                 hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
  72                 BUG_ON(hp == NULL);
  73
  74                 /* Calculate the header length */
  75                 if (nexthdr == NEXTHDR_FRAGMENT) {
  76                         hdrlen = 8;
  77                 } else if (nexthdr == NEXTHDR_AUTH)
  78                         hdrlen = (hp->hdrlen+2)<<2;
  79                 else
  80                         hdrlen = ipv6_optlen(hp);
  81
  82                 /* set the flag */
  83                 switch (nexthdr){
  84                         case NEXTHDR_HOP:
  85                                 temp |= MASK_HOPOPTS;
  86                                 break;
  87                         case NEXTHDR_ROUTING:
  88                                 temp |= MASK_ROUTING;
  89                                 break;
  90                         case NEXTHDR_FRAGMENT:
  91                                 temp |= MASK_FRAGMENT;
  92                                 break;
  93                         case NEXTHDR_AUTH:
  94                                 temp |= MASK_AH;
  95                                 break;
  96                         case NEXTHDR_DEST:
  97                                 temp |= MASK_DSTOPTS;
  98                                 break;
  99                         default:
 100                                 return 0;
 101                                 break;
 102                 }
 103
 104                 nexthdr = hp->nexthdr;
 105                 len -= hdrlen;
 106                 ptr += hdrlen;
 107                 if (ptr > skb->len)
 108                         break;
 109         }
 110
 111         if ( (nexthdr != NEXTHDR_NONE ) && (nexthdr != NEXTHDR_ESP) )
 112                 temp |= MASK_PROTO;
 113
 114         if (info->modeflag)
 115                 return !((temp ^ info->matchflags ^ info->invflags)
 116                          & info->matchflags);
 117         else {
 118                 if (info->invflags)
 119                         return temp != info->matchflags;
 120                 else
 121                         return temp == info->matchflags;
 122         }
 123 }
 124
 125 static int
 126 ipv6header_checkentry(const char *tablename,
 127                       const struct ip6t_ip6 *ip,
 128                       void *matchinfo,
 129                       unsigned int matchsize,
 130                       unsigned int hook_mask)
 131 {
 132         const struct ip6t_ipv6header_info *info = matchinfo;
 133
 134         /* Check for obvious errors */
 135         /* This match is valid in all hooks! */
 136         if (matchsize != IP6T_ALIGN(sizeof(struct ip6t_ipv6header_info)))
 137                 return 0;
 138
 139         /* invflags is 0 or 0xff in hard mode */
 140         if ((!info->modeflag) && info->invflags != 0x00
 141                               && info->invflags != 0xFF)
 142                 return 0;
 143
 144         return 1;
 145 }
 146
 147 static struct ip6t_match ip6t_ipv6header_match = {
 148         .name           = "ipv6header",
 149         .match          = &ipv6header_match,
 150         .checkentry     = &ipv6header_checkentry,
 151         .destroy        = NULL,
 152         .me             = THIS_MODULE,
 153 };
 154
 155 static int  __init ipv6header_init(void)
 156 {
 157         return ip6t_register_match(&ip6t_ipv6header_match);
 158 }
 159
 160 static void __exit ipv6header_exit(void)
 161 {
 162         ip6t_unregister_match(&ip6t_ipv6header_match);
 163 }
 164
 165 module_init(ipv6header_init);
 166 module_exit(ipv6header_exit);
 167