LXR linux/net/ipv6/netfilter/ip6t

   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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  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
  21MODULE_LICENSE("GPL");
  22MODULE_DESCRIPTION("Xtables: IPv6 fragment match");
  23MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
  24
  25/* Returns 1 if the id is matched by the range, 0 otherwise */
  26static inline bool
  27id_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
  28{
  29        bool r;
  30        pr_debug("id_match:%c 0x%x <= 0x%x <= 0x%x\n", 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
  37static bool
  38frag_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  39{
  40        struct frag_hdr _frag;
  41        const struct frag_hdr *fh;
  42        const struct ip6t_frag *fraginfo = par->matchinfo;
  43        unsigned int ptr = 0;
  44        int err;
  45
  46        err = ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL, NULL);
  47        if (err < 0) {
  48                if (err != -ENOENT)
  49                        par->hotdrop = true;
  50                return false;
  51        }
  52
  53        fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
  54        if (fh == NULL) {
  55                par->hotdrop = true;
  56                return false;
  57        }
  58
  59        pr_debug("INFO %04X ", fh->frag_off);
  60        pr_debug("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
  61        pr_debug("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
  62        pr_debug("MF %04X ", fh->frag_off & htons(IP6_MF));
  63        pr_debug("ID %u %08X\n", ntohl(fh->identification),
  64                 ntohl(fh->identification));
  65
  66        pr_debug("IPv6 FRAG id %02X ",
  67                 id_match(fraginfo->ids[0], fraginfo->ids[1],
  68                          ntohl(fh->identification),
  69                          !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)));
  70        pr_debug("res %02X %02X%04X %02X ",
  71                 fraginfo->flags & IP6T_FRAG_RES, fh->reserved,
  72                 ntohs(fh->frag_off) & 0x6,
  73                 !((fraginfo->flags & IP6T_FRAG_RES) &&
  74                   (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
  75        pr_debug("first %02X %02X %02X ",
  76                 fraginfo->flags & IP6T_FRAG_FST,
  77                 ntohs(fh->frag_off) & ~0x7,
  78                 !((fraginfo->flags & IP6T_FRAG_FST) &&
  79                   (ntohs(fh->frag_off) & ~0x7)));
  80        pr_debug("mf %02X %02X %02X ",
  81                 fraginfo->flags & IP6T_FRAG_MF,
  82                 ntohs(fh->frag_off) & IP6_MF,
  83                 !((fraginfo->flags & IP6T_FRAG_MF) &&
  84                   !((ntohs(fh->frag_off) & IP6_MF))));
  85        pr_debug("last %02X %02X %02X\n",
  86                 fraginfo->flags & IP6T_FRAG_NMF,
  87                 ntohs(fh->frag_off) & IP6_MF,
  88                 !((fraginfo->flags & IP6T_FRAG_NMF) &&
  89                   (ntohs(fh->frag_off) & IP6_MF)));
  90
  91        return (fh != NULL) &&
  92                id_match(fraginfo->ids[0], fraginfo->ids[1],
  93                         ntohl(fh->identification),
  94                         !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)) &&
  95                !((fraginfo->flags & IP6T_FRAG_RES) &&
  96                  (fh->reserved || (ntohs(fh->frag_off) & 0x6))) &&
  97                !((fraginfo->flags & IP6T_FRAG_FST) &&
  98                  (ntohs(fh->frag_off) & ~0x7)) &&
  99                !((fraginfo->flags & IP6T_FRAG_MF) &&
 100                  !(ntohs(fh->frag_off) & IP6_MF)) &&
 101                !((fraginfo->flags & IP6T_FRAG_NMF) &&
 102                  (ntohs(fh->frag_off) & IP6_MF));
 103}
 104
 105static int frag_mt6_check(const struct xt_mtchk_param *par)
 106{
 107        const struct ip6t_frag *fraginfo = par->matchinfo;
 108
 109        if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
 110                pr_debug("unknown flags %X\n", fraginfo->invflags);
 111                return -EINVAL;
 112        }
 113        return 0;
 114}
 115
 116static struct xt_match frag_mt6_reg __read_mostly = {
 117        .name           = "frag",
 118        .family         = NFPROTO_IPV6,
 119        .match          = frag_mt6,
 120        .matchsize      = sizeof(struct ip6t_frag),
 121        .checkentry     = frag_mt6_check,
 122        .me             = THIS_MODULE,
 123};
 124
 125static int __init frag_mt6_init(void)
 126{
 127        return xt_register_match(&frag_mt6_reg);
 128}
 129
 130static void __exit frag_mt6_exit(void)
 131{
 132        xt_unregister_match(&frag_mt6_reg);
 133}
 134
 135module_init(frag_mt6_init);
 136module_exit(frag_mt6_exit);
 137