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         int err;
  69
  70         err = ipv6_find_hdr(skb, &ptr, match->data, NULL);
  71         if (err < 0) {
  72                 if (err != -ENOENT)
  73                         *hotdrop = 1;
  74                 return 0;
  75         }
  76
  77         oh = skb_header_pointer(skb, ptr, sizeof(_optsh), &_optsh);
  78         if (oh == NULL) {
  79                 *hotdrop = 1;
  80                 return 0;
  81         }
  82
  83         hdrlen = ipv6_optlen(oh);
  84         if (skb->len - ptr < hdrlen) {
  85                 /* Packet smaller than it's length field */
  86                 return 0;
  87         }
  88
  89         DEBUGP("IPv6 OPTS LEN %u %u ", hdrlen, oh->hdrlen);
  90
  91         DEBUGP("len %02X %04X %02X ",
  92                optinfo->hdrlen, hdrlen,
  93                (!(optinfo->flags & IP6T_OPTS_LEN) ||
  94                 ((optinfo->hdrlen == hdrlen) ^
  95                  !!(optinfo->invflags & IP6T_OPTS_INV_LEN))));
  96
  97         ret = (oh != NULL) &&
  98               (!(optinfo->flags & IP6T_OPTS_LEN) ||
  99                ((optinfo->hdrlen == hdrlen) ^
 100                 !!(optinfo->invflags & IP6T_OPTS_INV_LEN)));
 101
 102         ptr += 2;
 103         hdrlen -= 2;
 104         if (!(optinfo->flags & IP6T_OPTS_OPTS)) {
 105                 return ret;
 106         } else if (optinfo->flags & IP6T_OPTS_NSTRICT) {
 107                 DEBUGP("Not strict - not implemented");
 108         } else {
 109                 DEBUGP("Strict ");
 110                 DEBUGP("#%d ", optinfo->optsnr);
 111                 for (temp = 0; temp < optinfo->optsnr; temp++) {
 112                         /* type field exists ? */
 113                         if (hdrlen < 1)
 114                                 break;
 115                         tp = skb_header_pointer(skb, ptr, sizeof(_opttype),
 116                                                 &_opttype);
 117                         if (tp == NULL)
 118                                 break;
 119
 120                         /* Type check */
 121                         if (*tp != (optinfo->opts[temp] & 0xFF00) >> 8) {
 122                                 DEBUGP("Tbad %02X %02X\n",
 123                                        *tp,
 124                                        (optinfo->opts[temp] & 0xFF00) >> 8);
 125                                 return 0;
 126                         } else {
 127                                 DEBUGP("Tok ");
 128                         }
 129                         /* Length check */
 130                         if (*tp) {
 131                                 u16 spec_len;
 132
 133                                 /* length field exists ? */
 134                                 if (hdrlen < 2)
 135                                         break;
 136                                 lp = skb_header_pointer(skb, ptr + 1,
 137                                                         sizeof(_optlen),
 138                                                         &_optlen);
 139                                 if (lp == NULL)
 140                                         break;
 141                                 spec_len = optinfo->opts[temp] & 0x00FF;
 142
 143                                 if (spec_len != 0x00FF && spec_len != *lp) {
 144                                         DEBUGP("Lbad %02X %04X\n", *lp,
 145                                                spec_len);
 146                                         return 0;
 147                                 }
 148                                 DEBUGP("Lok ");
 149                                 optlen = *lp + 2;
 150                         } else {
 151                                 DEBUGP("Pad1\n");
 152                                 optlen = 1;
 153                         }
 154
 155                         /* Step to the next */
 156                         DEBUGP("len%04X \n", optlen);
 157
 158                         if ((ptr > skb->len - optlen || hdrlen < optlen) &&
 159                             (temp < optinfo->optsnr - 1)) {
 160                                 DEBUGP("new pointer is too large! \n");
 161                                 break;
 162                         }
 163                         ptr += optlen;
 164                         hdrlen -= optlen;
 165                 }
 166                 if (temp == optinfo->optsnr)
 167                         return ret;
 168                 else
 169                         return 0;
 170         }
 171
 172         return 0;
 173 }
 174
 175 /* Called when user tries to insert an entry of this type. */
 176 static int
 177 checkentry(const char *tablename,
 178            const void *entry,
 179            const struct xt_match *match,
 180            void *matchinfo,
 181            unsigned int hook_mask)
 182 {
 183         const struct ip6t_opts *optsinfo = matchinfo;
 184
 185         if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) {
 186                 DEBUGP("ip6t_opts: unknown flags %X\n", optsinfo->invflags);
 187                 return 0;
 188         }
 189         return 1;
 190 }
 191
 192 static struct xt_match opts_match[] = {
 193         {
 194                 .name           = "hbh",
 195                 .family         = AF_INET6,
 196                 .match          = match,
 197                 .matchsize      = sizeof(struct ip6t_opts),
 198                 .checkentry     = checkentry,
 199                 .me             = THIS_MODULE,
 200                 .data           = NEXTHDR_HOP,
 201         },
 202         {
 203                 .name           = "dst",
 204                 .family         = AF_INET6,
 205                 .match          = match,
 206                 .matchsize      = sizeof(struct ip6t_opts),
 207                 .checkentry     = checkentry,
 208                 .me             = THIS_MODULE,
 209                 .data           = NEXTHDR_DEST,
 210         },
 211 };
 212
 213 static int __init ip6t_hbh_init(void)
 214 {
 215         return xt_register_matches(opts_match, ARRAY_SIZE(opts_match));
 216 }
 217
 218 static void __exit ip6t_hbh_fini(void)
 219 {
 220         xt_unregister_matches(opts_match, ARRAY_SIZE(opts_match));
 221 }
 222
 223 module_init(ip6t_hbh_init);
 224 module_exit(ip6t_hbh_fini);