net/ipv6/netfilter/ip6t_hbh.c

   1 /* Kernel module to match Hop-by-Hop and Destination parameters. */
   2
   3 /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/skbuff.h>
  12 #include <linux/ipv6.h>
  13 #include <linux/types.h>
  14 #include <net/checksum.h>
  15 #include <net/ipv6.h>
  16
  17 #include <asm/byteorder.h>
  18
  19 #include <linux/netfilter_ipv6/ip6_tables.h>
  20 #include <linux/netfilter_ipv6/ip6t_opts.h>
  21
  22 MODULE_LICENSE("GPL");
  23 MODULE_DESCRIPTION("IPv6 opts match");
  24 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  25 MODULE_ALIAS("ip6t_dst");
  26
  27 #if 0
  28 #define DEBUGP printk
  29 #else
  30 #define DEBUGP(format, args...)
  31 #endif
  32
  33 /*
  34  *  (Type & 0xC0) >> 6
  35  *      0       -> ignorable
  36  *      1       -> must drop the packet
  37  *      2       -> send ICMP PARM PROB regardless and drop packet
  38  *      3       -> Send ICMP if not a multicast address and drop packet
  39  *  (Type & 0x20) >> 5
  40  *      0       -> invariant
  41  *      1       -> can change the routing
  42  *  (Type & 0x1F) Type
  43  *      0       -> Pad1 (only 1 byte!)
  44  *      1       -> PadN LENGTH info (total length = length + 2)
  45  *      C0 | 2  -> JUMBO 4 x x x x ( xxxx > 64k )
  46  *      5       -> RTALERT 2 x x
  47  */
  48
  49 static int
  50 match(const struct sk_buff *skb,
  51       const struct net_device *in,
  52       const struct net_device *out,
  53       const struct xt_match *match,
  54       const void *matchinfo,
  55       int offset,
  56       unsigned int protoff,
  57       int *hotdrop)
  58 {
  59         struct ipv6_opt_hdr _optsh, *oh;
  60         const struct ip6t_opts *optinfo = matchinfo;
  61         unsigned int temp;
  62         unsigned int ptr;
  63         unsigned int hdrlen = 0;
  64         unsigned int ret = 0;
  65         u8 _opttype, *tp = NULL;
  66         u8 _optlen, *lp = NULL;
  67         unsigned int optlen;
  68
  69         if (ipv6_find_hdr(skb, &ptr, match->data, NULL) < 0)
  70                 return 0;
  71
  72         oh = skb_header_pointer(skb, ptr, sizeof(_optsh), &_optsh);
  73         if (oh == NULL) {
  74                 *hotdrop = 1;
  75                 return 0;
  76         }
  77
  78         hdrlen = ipv6_optlen(oh);
  79         if (skb->len - ptr < hdrlen) {
  80                 /* Packet smaller than it's length field */
  81                 return 0;
  82         }
  83
  84         DEBUGP("IPv6 OPTS LEN %u %u ", hdrlen, oh->hdrlen);
  85
  86         DEBUGP("len %02X %04X %02X ",
  87                optinfo->hdrlen, hdrlen,
  88                (!(optinfo->flags & IP6T_OPTS_LEN) ||
  89                 ((optinfo->hdrlen == hdrlen) ^
  90                  !!(optinfo->invflags & IP6T_OPTS_INV_LEN))));
  91
  92         ret = (oh != NULL) &&
  93               (!(optinfo->flags & IP6T_OPTS_LEN) ||
  94                ((optinfo->hdrlen == hdrlen) ^
  95                 !!(optinfo->invflags & IP6T_OPTS_INV_LEN)));
  96
  97         ptr += 2;
  98         hdrlen -= 2;
  99         if (!(optinfo->flags & IP6T_OPTS_OPTS)) {
 100                 return ret;
 101         } else if (optinfo->flags & IP6T_OPTS_NSTRICT) {
 102                 DEBUGP("Not strict - not implemented");
 103         } else {
 104                 DEBUGP("Strict ");
 105                 DEBUGP("#%d ", optinfo->optsnr);
 106                 for (temp = 0; temp < optinfo->optsnr; temp++) {
 107                         /* type field exists ? */
 108                         if (hdrlen < 1)
 109                                 break;
 110                         tp = skb_header_pointer(skb, ptr, sizeof(_opttype),
 111                                                 &_opttype);
 112                         if (tp == NULL)
 113                                 break;
 114
 115                         /* Type check */
 116                         if (*tp != (optinfo->opts[temp] & 0xFF00) >> 8) {
 117                                 DEBUGP("Tbad %02X %02X\n",
 118                                        *tp,
 119                                        (optinfo->opts[temp] & 0xFF00) >> 8);
 120                                 return 0;
 121                         } else {
 122                                 DEBUGP("Tok ");
 123                         }
 124                         /* Length check */
 125                         if (*tp) {
 126                                 u16 spec_len;
 127
 128                                 /* length field exists ? */
 129                                 if (hdrlen < 2)
 130                                         break;
 131                                 lp = skb_header_pointer(skb, ptr + 1,
 132                                                         sizeof(_optlen),
 133                                                         &_optlen);
 134                                 if (lp == NULL)
 135                                         break;
 136                                 spec_len = optinfo->opts[temp] & 0x00FF;
 137
 138                                 if (spec_len != 0x00FF && spec_len != *lp) {
 139                                         DEBUGP("Lbad %02X %04X\n", *lp,
 140                                                spec_len);
 141                                         return 0;
 142                                 }
 143                                 DEBUGP("Lok ");
 144                                 optlen = *lp + 2;
 145                         } else {
 146                                 DEBUGP("Pad1\n");
 147                                 optlen = 1;
 148                         }
 149
 150                         /* Step to the next */
 151                         DEBUGP("len%04X \n", optlen);
 152
 153                         if ((ptr > skb->len - optlen || hdrlen < optlen) &&
 154                             (temp < optinfo->optsnr - 1)) {
 155                                 DEBUGP("new pointer is too large! \n");
 156                                 break;
 157                         }
 158                         ptr += optlen;
 159                         hdrlen -= optlen;
 160                 }
 161                 if (temp == optinfo->optsnr)
 162                         return ret;
 163                 else
 164                         return 0;
 165         }
 166
 167         return 0;
 168 }
 169
 170 /* Called when user tries to insert an entry of this type. */
 171 static int
 172 checkentry(const char *tablename,
 173            const void *entry,
 174            const struct xt_match *match,
 175            void *matchinfo,
 176            unsigned int hook_mask)
 177 {
 178         const struct ip6t_opts *optsinfo = matchinfo;
 179
 180         if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) {
 181                 DEBUGP("ip6t_opts: unknown flags %X\n", optsinfo->invflags);
 182                 return 0;
 183         }
 184         return 1;
 185 }
 186
 187 static struct xt_match opts_match[] = {
 188         {
 189                 .name           = "hbh",
 190                 .family         = AF_INET6,
 191                 .match          = match,
 192                 .matchsize      = sizeof(struct ip6t_opts),
 193                 .checkentry     = checkentry,
 194                 .me             = THIS_MODULE,
 195                 .data           = NEXTHDR_HOP,
 196         },
 197         {
 198                 .name           = "dst",
 199                 .family         = AF_INET6,
 200                 .match          = match,
 201                 .matchsize      = sizeof(struct ip6t_opts),
 202                 .checkentry     = checkentry,
 203                 .me             = THIS_MODULE,
 204                 .data           = NEXTHDR_DEST,
 205         },
 206 };
 207
 208 static int __init ip6t_hbh_init(void)
 209 {
 210         return xt_register_matches(opts_match, ARRAY_SIZE(opts_match));
 211 }
 212
 213 static void __exit ip6t_hbh_fini(void)
 214 {
 215         xt_unregister_matches(opts_match, ARRAY_SIZE(opts_match));
 216 }
 217
 218 module_init(ip6t_hbh_init);
 219 module_exit(ip6t_hbh_fini);