net/ipv6/netfilter/ip6t_frag.c

   1 /* Kernel module to match FRAG 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 <linux/netfilter_ipv6/ip6_tables.h>
  18 #include <linux/netfilter_ipv6/ip6t_frag.h>
  19
  20 MODULE_LICENSE("GPL");
  21 MODULE_DESCRIPTION("IPv6 FRAG match");
  22 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  23
  24 #if 0
  25 #define DEBUGP printk
  26 #else
  27 #define DEBUGP(format, args...)
  28 #endif
  29
  30 /* Returns 1 if the id is matched by the range, 0 otherwise */
  31 static inline int
  32 id_match(u_int32_t min, u_int32_t max, u_int32_t id, int invert)
  33 {
  34         int r = 0;
  35         DEBUGP("frag id_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ',
  36                min, id, max);
  37         r = (id >= min && id <= max) ^ invert;
  38         DEBUGP(" result %s\n", r ? "PASS" : "FAILED");
  39         return r;
  40 }
  41
  42 static int
  43 match(const struct sk_buff *skb,
  44       const struct net_device *in,
  45       const struct net_device *out,
  46       const struct xt_match *match,
  47       const void *matchinfo,
  48       int offset,
  49       unsigned int protoff,
  50       int *hotdrop)
  51 {
  52         struct frag_hdr _frag, *fh;
  53         const struct ip6t_frag *fraginfo = matchinfo;
  54         unsigned int ptr;
  55
  56         if (ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL) < 0)
  57                 return 0;
  58
  59         fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
  60         if (fh == NULL) {
  61                 *hotdrop = 1;
  62                 return 0;
  63         }
  64
  65         DEBUGP("INFO %04X ", fh->frag_off);
  66         DEBUGP("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
  67         DEBUGP("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
  68         DEBUGP("MF %04X ", fh->frag_off & htons(IP6_MF));
  69         DEBUGP("ID %u %08X\n", ntohl(fh->identification),
  70                ntohl(fh->identification));
  71
  72         DEBUGP("IPv6 FRAG id %02X ",
  73                (id_match(fraginfo->ids[0], fraginfo->ids[1],
  74                          ntohl(fh->identification),
  75                          !!(fraginfo->invflags & IP6T_FRAG_INV_IDS))));
  76         DEBUGP("res %02X %02X%04X %02X ",
  77                (fraginfo->flags & IP6T_FRAG_RES), fh->reserved,
  78                ntohs(fh->frag_off) & 0x6,
  79                !((fraginfo->flags & IP6T_FRAG_RES)
  80                  && (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
  81         DEBUGP("first %02X %02X %02X ",
  82                (fraginfo->flags & IP6T_FRAG_FST),
  83                ntohs(fh->frag_off) & ~0x7,
  84                !((fraginfo->flags & IP6T_FRAG_FST)
  85                  && (ntohs(fh->frag_off) & ~0x7)));
  86         DEBUGP("mf %02X %02X %02X ",
  87                (fraginfo->flags & IP6T_FRAG_MF),
  88                ntohs(fh->frag_off) & IP6_MF,
  89                !((fraginfo->flags & IP6T_FRAG_MF)
  90                  && !((ntohs(fh->frag_off) & IP6_MF))));
  91         DEBUGP("last %02X %02X %02X\n",
  92                (fraginfo->flags & IP6T_FRAG_NMF),
  93                ntohs(fh->frag_off) & IP6_MF,
  94                !((fraginfo->flags & IP6T_FRAG_NMF)
  95                  && (ntohs(fh->frag_off) & IP6_MF)));
  96
  97         return (fh != NULL)
  98                &&
  99                (id_match(fraginfo->ids[0], fraginfo->ids[1],
 100                          ntohl(fh->identification),
 101                          !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)))
 102                &&
 103                !((fraginfo->flags & IP6T_FRAG_RES)
 104                  && (fh->reserved || (ntohs(fh->frag_off) & 0x6)))
 105                &&
 106                !((fraginfo->flags & IP6T_FRAG_FST)
 107                  && (ntohs(fh->frag_off) & ~0x7))
 108                &&
 109                !((fraginfo->flags & IP6T_FRAG_MF)
 110                  && !(ntohs(fh->frag_off) & IP6_MF))
 111                &&
 112                !((fraginfo->flags & IP6T_FRAG_NMF)
 113                  && (ntohs(fh->frag_off) & IP6_MF));
 114 }
 115
 116 /* Called when user tries to insert an entry of this type. */
 117 static int
 118 checkentry(const char *tablename,
 119            const void *ip,
 120            const struct xt_match *match,
 121            void *matchinfo,
 122            unsigned int matchinfosize,
 123            unsigned int hook_mask)
 124 {
 125         const struct ip6t_frag *fraginfo = matchinfo;
 126
 127         if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
 128                 DEBUGP("ip6t_frag: unknown flags %X\n", fraginfo->invflags);
 129                 return 0;
 130         }
 131         return 1;
 132 }
 133
 134 static struct ip6t_match frag_match = {
 135         .name           = "frag",
 136         .match          = match,
 137         .matchsize      = sizeof(struct ip6t_frag),
 138         .checkentry     = checkentry,
 139         .me             = THIS_MODULE,
 140 };
 141
 142 static int __init init(void)
 143 {
 144         return ip6t_register_match(&frag_match);
 145 }
 146
 147 static void __exit cleanup(void)
 148 {
 149         ip6t_unregister_match(&frag_match);
 150 }
 151
 152 module_init(init);
 153 module_exit(cleanup);