ip6t_frag.c

linux-2.6.15.6

/* Kernel module to match FRAG parameters. */

/* (C) 2001-2002 Andras Kis-Szabo <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ipv6.h>
#include <linux/types.h>
#include <net/checksum.h>
#include <net/ipv6.h>

#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter_ipv6/ip6t_frag.h>

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("IPv6 FRAG match");
MODULE_AUTHOR("Andras Kis-Szabo <[e-mail]>");

#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif

/* Returns 1 if the id is matched by the range, 0 otherwise */
static inline int
id_match(u_int32_t min, u_int32_t max, u_int32_t id, int invert)
{
       int r=0;
       DEBUGP("frag id_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',
              min,id,max);
       r=(id >= min && id <= max) ^ invert;
       DEBUGP(" result %s\n",r? "PASS" : "FAILED");
       return r;
}

static int
match(const struct sk_buff *skb,
      const struct net_device *in,
      const struct net_device *out,
      const void *matchinfo,
      int offset,
      unsigned int protoff,
      int *hotdrop)
{
       struct frag_hdr _frag, *fh;
       const struct ip6t_frag *fraginfo = matchinfo;
       unsigned int ptr;

	if (ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT) < 0)
		return 0;

	fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
	if (fh == NULL){
		*hotdrop = 1;
		return 0;
	}

       DEBUGP("INFO %04X ", fh->frag_off);
       DEBUGP("OFFSET %04X ", ntohs(fh->frag_off) & ~0x7);
       DEBUGP("RES %02X %04X", fh->reserved, ntohs(fh->frag_off) & 0x6);
       DEBUGP("MF %04X ", fh->frag_off & htons(IP6_MF));
       DEBUGP("ID %u %08X\n", ntohl(fh->identification),
	      ntohl(fh->identification));

       DEBUGP("IPv6 FRAG id %02X ",
       		(id_match(fraginfo->ids[0], fraginfo->ids[1],
                           ntohl(fh->identification),
                           !!(fraginfo->invflags & IP6T_FRAG_INV_IDS))));
       DEBUGP("res %02X %02X%04X %02X ", 
       		(fraginfo->flags & IP6T_FRAG_RES), fh->reserved,
		ntohs(fh->frag_off) & 0x6,
       		!((fraginfo->flags & IP6T_FRAG_RES)
			&& (fh->reserved || (ntohs(fh->frag_off) & 0x06))));
       DEBUGP("first %02X %02X %02X ", 
       		(fraginfo->flags & IP6T_FRAG_FST),
		ntohs(fh->frag_off) & ~0x7,
       		!((fraginfo->flags & IP6T_FRAG_FST)
			&& (ntohs(fh->frag_off) & ~0x7)));
       DEBUGP("mf %02X %02X %02X ", 
       		(fraginfo->flags & IP6T_FRAG_MF),
		ntohs(fh->frag_off) & IP6_MF,
       		!((fraginfo->flags & IP6T_FRAG_MF)
			&& !((ntohs(fh->frag_off) & IP6_MF))));
       DEBUGP("last %02X %02X %02X\n", 
       		(fraginfo->flags & IP6T_FRAG_NMF),
		ntohs(fh->frag_off) & IP6_MF,
       		!((fraginfo->flags & IP6T_FRAG_NMF)
			&& (ntohs(fh->frag_off) & IP6_MF)));

       return (fh != NULL)
       		&&
       		(id_match(fraginfo->ids[0], fraginfo->ids[1],
			  ntohl(fh->identification),
                           !!(fraginfo->invflags & IP6T_FRAG_INV_IDS)))
		&&
		!((fraginfo->flags & IP6T_FRAG_RES)
			&& (fh->reserved || (ntohs(fh->frag_off) & 0x6)))
		&&
		!((fraginfo->flags & IP6T_FRAG_FST)
			&& (ntohs(fh->frag_off) & ~0x7))
		&&
		!((fraginfo->flags & IP6T_FRAG_MF)
			&& !(ntohs(fh->frag_off) & IP6_MF))
		&&
		!((fraginfo->flags & IP6T_FRAG_NMF)
			&& (ntohs(fh->frag_off) & IP6_MF));
}

/* Called when user tries to insert an entry of this type. */
static int
checkentry(const char *tablename,
          const struct ip6t_ip6 *ip,
          void *matchinfo,
          unsigned int matchinfosize,
          unsigned int hook_mask)
{
       const struct ip6t_frag *fraginfo = matchinfo;

       if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_frag))) {
              DEBUGP("ip6t_frag: matchsize %u != %u\n",
                      matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_frag)));
              return 0;
       }
       if (fraginfo->invflags & ~IP6T_FRAG_INV_MASK) {
              DEBUGP("ip6t_frag: unknown flags %X\n",
                      fraginfo->invflags);
              return 0;
       }

       return 1;
}

static struct ip6t_match frag_match = {
	.name		= "frag",
	.match		= &match,
	.checkentry	= &checkentry,
	.me		= THIS_MODULE,
};

static int __init init(void)
{
       return ip6t_register_match(&frag_match);
}

static void __exit cleanup(void)
{
       ip6t_unregister_match(&frag_match);
}

module_init(init);
module_exit(cleanup);