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/x_tables.h>
  18 #include <linux/netfilter_ipv6/ip6_tables.h>
  19 #include <linux/netfilter_ipv6/ip6t_frag.h>
  20
  21 MODULE_LICENSE("GPL");
  22 MODULE_DESCRIPTION("IPv6 FRAG match");
  23 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  24
  25 #if 0
  26 #define DEBUGP printk
  27 #else
  28 #define DEBUGP(format, args...)
  29 #endif
  30
  31 /* Returns 1 if the id is matched by the range, 0 otherwise */
  32 static inline bool
  33 id_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
  34 {
  35         bool r;
  36         DEBUGP("frag id_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ',
  37                min, id, max);
  38         r = (id >= min && id <= max) ^ invert;
  39         DEBUGP(" result %s\n", r ? "PASS" : "FAILED");
  40         return r;
  41 }
  42
  43 static bool
  44 match(const struct sk_buff *skb,
  45       const struct net_device *in,
  46       const struct net_device *out,
  47       const struct xt_match *match,
  48       const void *matchinfo,
  49       int offset,
  50       unsigned int protoff,
  51       bool *hotdrop)
  52 {
  53         struct frag_hdr _frag;
  54         const struct frag_hdr *fh;
  55         const struct ip6t_frag *fraginfo = matchinfo;
  56         unsigned int ptr;
  57         int err;
  58
  59         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL);
  60         if (err < 0) {
  61                 if (err != -ENOENT)
  62                         *hotdrop = true;
  63                 return false;
  64         }
  65
  66         fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
  67         if (fh == NULL) {
  68                 *hotdrop = true;
  69                 return false;
  70         }
  71
  72         DEBUGP("INFO %04X ", fh->frag_off);
  73         DEBUGP("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
  74         DEBUGP("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
  75         DEBUGP("MF %04X ", fh->frag_off & htons(IP6_MF));
  76         DEBUGP("ID %u %08X\n", ntohl(fh->identification),
  77                ntohl(fh->identification));
  78
  79         DEBUGP("IPv6 FRAG id %02X ",
  80                (id_match(fraginfo->ids[0], fraginfo->ids[1],
  81                          ntohl(fh->identification),
  82                          !!(fraginfo->invflags & IP6T_FRAG_INV_IDS))));
  83         DEBUGP("res %02X %02X%04X %02X ",
  84                (fraginfo->flags & IP6T_FRAG_RES), fh->reserved,
  85                ntohs(fh->frag_off) & 0x6,
  86                !((fraginfo->flags & IP6T_FRAG_RES)
  87                  && (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
  88         DEBUGP("first %02X %02X %02X ",
  89                (fraginfo->flags & IP6T_FRAG_FST),
  90                ntohs(fh->frag_off) & ~0x7,
  91                !((fraginfo->flags & IP6T_FRAG_FST)
  92                  && (ntohs(fh->frag_off) & ~0x7)));
  93         DEBUGP("mf %02X %02X %02X ",
  94                (fraginfo->flags & IP6T_FRAG_MF),
  95                ntohs(fh->frag_off) & IP6_MF,
  96                !((fraginfo->flags & IP6T_FRAG_MF)
  97                  && !((ntohs(fh->frag_off) & IP6_MF))));
  98         DEBUGP("last %02X %02X %02X\n",
  99                (fraginfo->flags & IP6T_FRAG_NMF),
 100                ntohs(fh->frag_off) & IP6_MF,
 101                !((fraginfo->flags & IP6T_FRAG_NMF)
 102                  && (ntohs(fh->frag_off) & IP6_MF)));
 103
 104         return (fh != NULL)
 105                &&
 106                (id_match(fraginfo->ids[0], fraginfo->ids[1],
 107                          ntohl(fh->identification),
 108                          !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)))
 109                &&
 110                !((fraginfo->flags & IP6T_FRAG_RES)
 111                  && (fh->reserved || (ntohs(fh->frag_off) & 0x6)))
 112                &&
 113                !((fraginfo->flags & IP6T_FRAG_FST)
 114                  && (ntohs(fh->frag_off) & ~0x7))
 115                &&
 116                !((fraginfo->flags & IP6T_FRAG_MF)
 117                  && !(ntohs(fh->frag_off) & IP6_MF))
 118                &&
 119                !((fraginfo->flags & IP6T_FRAG_NMF)
 120                  && (ntohs(fh->frag_off) & IP6_MF));
 121 }
 122
 123 /* Called when user tries to insert an entry of this type. */
 124 static bool
 125 checkentry(const char *tablename,
 126            const void *ip,
 127            const struct xt_match *match,
 128            void *matchinfo,
 129            unsigned int hook_mask)
 130 {
 131         const struct ip6t_frag *fraginfo = matchinfo;
 132
 133         if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
 134                 DEBUGP("ip6t_frag: unknown flags %X\n", fraginfo->invflags);
 135                 return false;
 136         }
 137         return true;
 138 }
 139
 140 static struct xt_match frag_match = {
 141         .name           = "frag",
 142         .family         = AF_INET6,
 143         .match          = match,
 144         .matchsize      = sizeof(struct ip6t_frag),
 145         .checkentry     = checkentry,
 146         .me             = THIS_MODULE,
 147 };
 148
 149 static int __init ip6t_frag_init(void)
 150 {
 151         return xt_register_match(&frag_match);
 152 }
 153
 154 static void __exit ip6t_frag_fini(void)
 155 {
 156         xt_unregister_match(&frag_match);
 157 }
 158
 159 module_init(ip6t_frag_init);
 160 module_exit(ip6t_frag_fini);