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("Xtables: IPv6 fragment match");
  23 MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  24
  25 /* Returns 1 if the id is matched by the range, 0 otherwise */
  26 static inline bool
  27 id_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
  28 {
  29         bool r;
  30         pr_debug("frag id_match:%c 0x%x <= 0x%x <= 0x%x", invert ? '!' : ' ',
  31                  min, id, max);
  32         r = (id >= min && id <= max) ^ invert;
  33         pr_debug(" result %s\n", r ? "PASS" : "FAILED");
  34         return r;
  35 }
  36
  37 static bool
  38 frag_mt6(const struct sk_buff *skb, const struct net_device *in,
  39          const struct net_device *out, const struct xt_match *match,
  40          const void *matchinfo, int offset, unsigned int protoff,
  41          bool *hotdrop)
  42 {
  43         struct frag_hdr _frag;
  44         const struct frag_hdr *fh;
  45         const struct ip6t_frag *fraginfo = matchinfo;
  46         unsigned int ptr;
  47         int err;
  48
  49         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL);
  50         if (err < 0) {
  51                 if (err != -ENOENT)
  52                         *hotdrop = true;
  53                 return false;
  54         }
  55
  56         fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
  57         if (fh == NULL) {
  58                 *hotdrop = true;
  59                 return false;
  60         }
  61
  62         pr_debug("INFO %04X ", fh->frag_off);
  63         pr_debug("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
  64         pr_debug("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
  65         pr_debug("MF %04X ", fh->frag_off & htons(IP6_MF));
  66         pr_debug("ID %u %08X\n", ntohl(fh->identification),
  67                  ntohl(fh->identification));
  68
  69         pr_debug("IPv6 FRAG id %02X ",
  70                  id_match(fraginfo->ids[0], fraginfo->ids[1],
  71                           ntohl(fh->identification),
  72                           !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)));
  73         pr_debug("res %02X %02X%04X %02X ",
  74                  fraginfo->flags & IP6T_FRAG_RES, fh->reserved,
  75                  ntohs(fh->frag_off) & 0x6,
  76                  !((fraginfo->flags & IP6T_FRAG_RES)
  77                    && (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
  78         pr_debug("first %02X %02X %02X ",
  79                  fraginfo->flags & IP6T_FRAG_FST,
  80                  ntohs(fh->frag_off) & ~0x7,
  81                  !((fraginfo->flags & IP6T_FRAG_FST)
  82                    && (ntohs(fh->frag_off) & ~0x7)));
  83         pr_debug("mf %02X %02X %02X ",
  84                  fraginfo->flags & IP6T_FRAG_MF,
  85                  ntohs(fh->frag_off) & IP6_MF,
  86                  !((fraginfo->flags & IP6T_FRAG_MF)
  87                    && !((ntohs(fh->frag_off) & IP6_MF))));
  88         pr_debug("last %02X %02X %02X\n",
  89                  fraginfo->flags & IP6T_FRAG_NMF,
  90                  ntohs(fh->frag_off) & IP6_MF,
  91                  !((fraginfo->flags & IP6T_FRAG_NMF)
  92                    && (ntohs(fh->frag_off) & IP6_MF)));
  93
  94         return (fh != NULL)
  95                &&
  96                id_match(fraginfo->ids[0], fraginfo->ids[1],
  97                         ntohl(fh->identification),
  98                         !!(fraginfo->invflags & IP6T_FRAG_INV_IDS))
  99                &&
 100                !((fraginfo->flags & IP6T_FRAG_RES)
 101                  && (fh->reserved || (ntohs(fh->frag_off) & 0x6)))
 102                &&
 103                !((fraginfo->flags & IP6T_FRAG_FST)
 104                  && (ntohs(fh->frag_off) & ~0x7))
 105                &&
 106                !((fraginfo->flags & IP6T_FRAG_MF)
 107                  && !(ntohs(fh->frag_off) & IP6_MF))
 108                &&
 109                !((fraginfo->flags & IP6T_FRAG_NMF)
 110                  && (ntohs(fh->frag_off) & IP6_MF));
 111 }
 112
 113 /* Called when user tries to insert an entry of this type. */
 114 static bool
 115 frag_mt6_check(const char *tablename, const void *ip,
 116                const struct xt_match *match, void *matchinfo,
 117                unsigned int hook_mask)
 118 {
 119         const struct ip6t_frag *fraginfo = matchinfo;
 120
 121         if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
 122                 pr_debug("ip6t_frag: unknown flags %X\n", fraginfo->invflags);
 123                 return false;
 124         }
 125         return true;
 126 }
 127
 128 static struct xt_match frag_mt6_reg __read_mostly = {
 129         .name           = "frag",
 130         .family         = AF_INET6,
 131         .match          = frag_mt6,
 132         .matchsize      = sizeof(struct ip6t_frag),
 133         .checkentry     = frag_mt6_check,
 134         .me             = THIS_MODULE,
 135 };
 136
 137 static int __init frag_mt6_init(void)
 138 {
 139         return xt_register_match(&frag_mt6_reg);
 140 }
 141
 142 static void __exit frag_mt6_exit(void)
 143 {
 144         xt_unregister_match(&frag_mt6_reg);
 145 }
 146
 147 module_init(frag_mt6_init);
 148 module_exit(frag_mt6_exit);