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 #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
  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("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
  37 static bool
  38 frag_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;
  44         int err;
  45
  46         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, 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
 105 static 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
 116 static 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
 125 static int __init frag_mt6_init(void)
 126 {
 127         return xt_register_match(&frag_mt6_reg);
 128 }
 129
 130 static void __exit frag_mt6_exit(void)
 131 {
 132         xt_unregister_match(&frag_mt6_reg);
 133 }
 134
 135 module_init(frag_mt6_init);
 136 module_exit(frag_mt6_exit);