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 int
  33 id_match(u_int32_t min, u_int32_t max, u_int32_t id, int invert)
  34 {
  35         int r = 0;
  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 int
  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       int *hotdrop)
  52 {
  53         struct frag_hdr _frag, *fh;
  54         const struct ip6t_frag *fraginfo = matchinfo;
  55         unsigned int ptr;
  56         int err;
  57
  58         err = ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL);
  59         if (err < 0) {
  60                 if (err != -ENOENT)
  61                         *hotdrop = 1;
  62                 return 0;
  63         }
  64
  65         fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
  66         if (fh == NULL) {
  67                 *hotdrop = 1;
  68                 return 0;
  69         }
  70
  71         DEBUGP("INFO %04X ", fh->frag_off);
  72         DEBUGP("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
  73         DEBUGP("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
  74         DEBUGP("MF %04X ", fh->frag_off & htons(IP6_MF));
  75         DEBUGP("ID %u %08X\n", ntohl(fh->identification),
  76                ntohl(fh->identification));
  77
  78         DEBUGP("IPv6 FRAG id %02X ",
  79                (id_match(fraginfo->ids[0], fraginfo->ids[1],
  80                          ntohl(fh->identification),
  81                          !!(fraginfo->invflags & IP6T_FRAG_INV_IDS))));
  82         DEBUGP("res %02X %02X%04X %02X ",
  83                (fraginfo->flags & IP6T_FRAG_RES), fh->reserved,
  84                ntohs(fh->frag_off) & 0x6,
  85                !((fraginfo->flags & IP6T_FRAG_RES)
  86                  && (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
  87         DEBUGP("first %02X %02X %02X ",
  88                (fraginfo->flags & IP6T_FRAG_FST),
  89                ntohs(fh->frag_off) & ~0x7,
  90                !((fraginfo->flags & IP6T_FRAG_FST)
  91                  && (ntohs(fh->frag_off) & ~0x7)));
  92         DEBUGP("mf %02X %02X %02X ",
  93                (fraginfo->flags & IP6T_FRAG_MF),
  94                ntohs(fh->frag_off) & IP6_MF,
  95                !((fraginfo->flags & IP6T_FRAG_MF)
  96                  && !((ntohs(fh->frag_off) & IP6_MF))));
  97         DEBUGP("last %02X %02X %02X\n",
  98                (fraginfo->flags & IP6T_FRAG_NMF),
  99                ntohs(fh->frag_off) & IP6_MF,
 100                !((fraginfo->flags & IP6T_FRAG_NMF)
 101                  && (ntohs(fh->frag_off) & IP6_MF)));
 102
 103         return (fh != NULL)
 104                &&
 105                (id_match(fraginfo->ids[0], fraginfo->ids[1],
 106                          ntohl(fh->identification),
 107                          !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)))
 108                &&
 109                !((fraginfo->flags & IP6T_FRAG_RES)
 110                  && (fh->reserved || (ntohs(fh->frag_off) & 0x6)))
 111                &&
 112                !((fraginfo->flags & IP6T_FRAG_FST)
 113                  && (ntohs(fh->frag_off) & ~0x7))
 114                &&
 115                !((fraginfo->flags & IP6T_FRAG_MF)
 116                  && !(ntohs(fh->frag_off) & IP6_MF))
 117                &&
 118                !((fraginfo->flags & IP6T_FRAG_NMF)
 119                  && (ntohs(fh->frag_off) & IP6_MF));
 120 }
 121
 122 /* Called when user tries to insert an entry of this type. */
 123 static int
 124 checkentry(const char *tablename,
 125            const void *ip,
 126            const struct xt_match *match,
 127            void *matchinfo,
 128            unsigned int hook_mask)
 129 {
 130         const struct ip6t_frag *fraginfo = matchinfo;
 131
 132         if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
 133                 DEBUGP("ip6t_frag: unknown flags %X\n", fraginfo->invflags);
 134                 return 0;
 135         }
 136         return 1;
 137 }
 138
 139 static struct xt_match frag_match = {
 140         .name           = "frag",
 141         .family         = AF_INET6,
 142         .match          = match,
 143         .matchsize      = sizeof(struct ip6t_frag),
 144         .checkentry     = checkentry,
 145         .me             = THIS_MODULE,
 146 };
 147
 148 static int __init ip6t_frag_init(void)
 149 {
 150         return xt_register_match(&frag_match);
 151 }
 152
 153 static void __exit ip6t_frag_fini(void)
 154 {
 155         xt_unregister_match(&frag_match);
 156 }
 157
 158 module_init(ip6t_frag_init);
 159 module_exit(ip6t_frag_fini);