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/* Kernel module to match FRAG parameters. */
/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
*
* 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 <kisza@sch.bme.hu>");
#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 = NULL;
const struct ip6t_frag *fraginfo = matchinfo;
unsigned int temp;
int len;
u8 nexthdr;
unsigned int ptr;
unsigned int hdrlen = 0;
/* type of the 1st exthdr */
nexthdr = skb->nh.ipv6h->nexthdr;
/* pointer to the 1st exthdr */
ptr = sizeof(struct ipv6hdr);
/* available length */
len = skb->len - ptr;
temp = 0;
while (ip6t_ext_hdr(nexthdr)) {
struct ipv6_opt_hdr _hdr, *hp;
DEBUGP("ipv6_frag header iteration \n");
/* Is there enough space for the next ext header? */
if (len < (int)sizeof(struct ipv6_opt_hdr))
return 0;
/* No more exthdr -> evaluate */
if (nexthdr == NEXTHDR_NONE) {
break;
}
/* ESP -> evaluate */
if (nexthdr == NEXTHDR_ESP) {
break;
}
hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
BUG_ON(hp == NULL);
/* Calculate the header length */
if (nexthdr == NEXTHDR_FRAGMENT) {
hdrlen = 8;
} else if (nexthdr == NEXTHDR_AUTH)
hdrlen = (hp->hdrlen+2)<<2;
else
hdrlen = ipv6_optlen(hp);
/* FRAG -> evaluate */
if (nexthdr == NEXTHDR_FRAGMENT) {
temp |= MASK_FRAGMENT;
break;
}
/* set the flag */
switch (nexthdr){
case NEXTHDR_HOP:
case NEXTHDR_ROUTING:
case NEXTHDR_FRAGMENT:
case NEXTHDR_AUTH:
case NEXTHDR_DEST:
break;
default:
DEBUGP("ipv6_frag match: unknown nextheader %u\n",nexthdr);
return 0;
break;
}
nexthdr = hp->nexthdr;
len -= hdrlen;
ptr += hdrlen;
if ( ptr > skb->len ) {
DEBUGP("ipv6_frag: new pointer too large! \n");
break;
}
}
/* FRAG header not found */
if ( temp != MASK_FRAGMENT ) return 0;
if (len < sizeof(struct frag_hdr)){
*hotdrop = 1;
return 0;
}
fh = skb_header_pointer(skb, ptr, sizeof(_frag), &_frag);
BUG_ON(fh == NULL);
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);
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