net/ipv6/netfilter/ip6t_dst.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 #define HOPBYHOP        0
  23
  24 MODULE_LICENSE("GPL");
  25 #if HOPBYHOP
  26 MODULE_DESCRIPTION("IPv6 HbH match");
  27 #else
  28 MODULE_DESCRIPTION("IPv6 DST match");
  29 #endif
  30 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  31
  32 #if 0
  33 #define DEBUGP printk
  34 #else
  35 #define DEBUGP(format, args...)
  36 #endif
  37
  38 /*
  39  *  (Type & 0xC0) >> 6
  40  *      0       -> ignorable
  41  *      1       -> must drop the packet
  42  *      2       -> send ICMP PARM PROB regardless and drop packet
  43  *      3       -> Send ICMP if not a multicast address and drop packet
  44  *  (Type & 0x20) >> 5
  45  *      0       -> invariant
  46  *      1       -> can change the routing
  47  *  (Type & 0x1F) Type
  48  *      0       -> Pad1 (only 1 byte!)
  49  *      1       -> PadN LENGTH info (total length = length + 2)
  50  *      C0 | 2  -> JUMBO 4 x x x x ( xxxx > 64k )
  51  *      5       -> RTALERT 2 x x
  52  */
  53
  54 static int
  55 match(const struct sk_buff *skb,
  56       const struct net_device *in,
  57       const struct net_device *out,
  58       const struct xt_match *match,
  59       const void *matchinfo,
  60       int offset,
  61       unsigned int protoff,
  62       int *hotdrop)
  63 {
  64         struct ipv6_opt_hdr _optsh, *oh;
  65         const struct ip6t_opts *optinfo = matchinfo;
  66         unsigned int temp;
  67         unsigned int ptr;
  68         unsigned int hdrlen = 0;
  69         unsigned int ret = 0;
  70         u8 _opttype, *tp = NULL;
  71         u8 _optlen, *lp = NULL;
  72         unsigned int optlen;
  73
  74 #if HOPBYHOP
  75         if (ipv6_find_hdr(skb, &ptr, NEXTHDR_HOP, NULL) < 0)
  76 #else
  77         if (ipv6_find_hdr(skb, &ptr, NEXTHDR_DEST, NULL) < 0)
  78 #endif
  79                 return 0;
  80
  81         oh = skb_header_pointer(skb, ptr, sizeof(_optsh), &_optsh);
  82         if (oh == NULL) {
  83                 *hotdrop = 1;
  84                 return 0;
  85         }
  86
  87         hdrlen = ipv6_optlen(oh);
  88         if (skb->len - ptr < hdrlen) {
  89                 /* Packet smaller than it's length field */
  90                 return 0;
  91         }
  92
  93         DEBUGP("IPv6 OPTS LEN %u %u ", hdrlen, oh->hdrlen);
  94
  95         DEBUGP("len %02X %04X %02X ",
  96                optinfo->hdrlen, hdrlen,
  97                (!(optinfo->flags & IP6T_OPTS_LEN) ||
  98                 ((optinfo->hdrlen == hdrlen) ^
  99                  !!(optinfo->invflags & IP6T_OPTS_INV_LEN))));
 100
 101         ret = (oh != NULL) &&
 102               (!(optinfo->flags & IP6T_OPTS_LEN) ||
 103                ((optinfo->hdrlen == hdrlen) ^
 104                 !!(optinfo->invflags & IP6T_OPTS_INV_LEN)));
 105
 106         ptr += 2;
 107         hdrlen -= 2;
 108         if (!(optinfo->flags & IP6T_OPTS_OPTS)) {
 109                 return ret;
 110         } else if (optinfo->flags & IP6T_OPTS_NSTRICT) {
 111                 DEBUGP("Not strict - not implemented");
 112         } else {
 113                 DEBUGP("Strict ");
 114                 DEBUGP("#%d ", optinfo->optsnr);
 115                 for (temp = 0; temp < optinfo->optsnr; temp++) {
 116                         /* type field exists ? */
 117                         if (hdrlen < 1)
 118                                 break;
 119                         tp = skb_header_pointer(skb, ptr, sizeof(_opttype),
 120                                                 &_opttype);
 121                         if (tp == NULL)
 122                                 break;
 123
 124                         /* Type check */
 125                         if (*tp != (optinfo->opts[temp] & 0xFF00) >> 8) {
 126                                 DEBUGP("Tbad %02X %02X\n",
 127                                        *tp,
 128                                        (optinfo->opts[temp] & 0xFF00) >> 8);
 129                                 return 0;
 130                         } else {
 131                                 DEBUGP("Tok ");
 132                         }
 133                         /* Length check */
 134                         if (*tp) {
 135                                 u16 spec_len;
 136
 137                                 /* length field exists ? */
 138                                 if (hdrlen < 2)
 139                                         break;
 140                                 lp = skb_header_pointer(skb, ptr + 1,
 141                                                         sizeof(_optlen),
 142                                                         &_optlen);
 143                                 if (lp == NULL)
 144                                         break;
 145                                 spec_len = optinfo->opts[temp] & 0x00FF;
 146
 147                                 if (spec_len != 0x00FF && spec_len != *lp) {
 148                                         DEBUGP("Lbad %02X %04X\n", *lp,
 149                                                spec_len);
 150                                         return 0;
 151                                 }
 152                                 DEBUGP("Lok ");
 153                                 optlen = *lp + 2;
 154                         } else {
 155                                 DEBUGP("Pad1\n");
 156                                 optlen = 1;
 157                         }
 158
 159                         /* Step to the next */
 160                         DEBUGP("len%04X \n", optlen);
 161
 162                         if ((ptr > skb->len - optlen || hdrlen < optlen) &&
 163                             (temp < optinfo->optsnr - 1)) {
 164                                 DEBUGP("new pointer is too large! \n");
 165                                 break;
 166                         }
 167                         ptr += optlen;
 168                         hdrlen -= optlen;
 169                 }
 170                 if (temp == optinfo->optsnr)
 171                         return ret;
 172                 else
 173                         return 0;
 174         }
 175
 176         return 0;
 177 }
 178
 179 /* Called when user tries to insert an entry of this type. */
 180 static int
 181 checkentry(const char *tablename,
 182            const void *info,
 183            const struct xt_match *match,
 184            void *matchinfo,
 185            unsigned int matchinfosize,
 186            unsigned int hook_mask)
 187 {
 188         const struct ip6t_opts *optsinfo = matchinfo;
 189
 190         if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) {
 191                 DEBUGP("ip6t_opts: unknown flags %X\n", optsinfo->invflags);
 192                 return 0;
 193         }
 194         return 1;
 195 }
 196
 197 static struct ip6t_match opts_match = {
 198 #if HOPBYHOP
 199         .name           = "hbh",
 200 #else
 201         .name           = "dst",
 202 #endif
 203         .match          = match,
 204         .matchsize      = sizeof(struct ip6t_opts),
 205         .checkentry     = checkentry,
 206         .me             = THIS_MODULE,
 207 };
 208
 209 static int __init ip6t_dst_init(void)
 210 {
 211         return ip6t_register_match(&opts_match);
 212 }
 213
 214 static void __exit ip6t_dst_fini(void)
 215 {
 216         ip6t_unregister_match(&opts_match);
 217 }
 218
 219 module_init(ip6t_dst_init);
 220 module_exit(ip6t_dst_fini);