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/* Kernel module to match Hop-by-Hop and Destination 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 <asm/byteorder.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter_ipv6/ip6t_opts.h>
#define HOPBYHOP 1
MODULE_LICENSE("GPL");
#if HOPBYHOP
MODULE_DESCRIPTION("IPv6 HbH match");
#else
MODULE_DESCRIPTION("IPv6 DST match");
#endif
MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif
/*
* (Type & 0xC0) >> 6
* 0 -> ignorable
* 1 -> must drop the packet
* 2 -> send ICMP PARM PROB regardless and drop packet
* 3 -> Send ICMP if not a multicast address and drop packet
* (Type & 0x20) >> 5
* 0 -> invariant
* 1 -> can change the routing
* (Type & 0x1F) Type
* 0 -> Pad1 (only 1 byte!)
* 1 -> PadN LENGTH info (total length = length + 2)
* C0 | 2 -> JUMBO 4 x x x x ( xxxx > 64k )
* 5 -> RTALERT 2 x x
*/
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 ipv6_opt_hdr _optsh, *oh;
const struct ip6t_opts *optinfo = matchinfo;
unsigned int temp;
unsigned int len;
u8 nexthdr;
unsigned int ptr;
unsigned int hdrlen = 0;
unsigned int ret = 0;
u8 _opttype, *tp = NULL;
u8 _optlen, *lp = NULL;
unsigned int optlen;
/* 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_opts 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);
/* OPTS -> evaluate */
#if HOPBYHOP
if (nexthdr == NEXTHDR_HOP) {
temp |= MASK_HOPOPTS;
#else
if (nexthdr == NEXTHDR_DEST) {
temp |= MASK_DSTOPTS;
#endif
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_opts match: unknown nextheader %u\n",nexthdr);
return 0;
break;
}
nexthdr = hp->nexthdr;
len -= hdrlen;
ptr += hdrlen;
if ( ptr > skb->len ) {
DEBUGP("ipv6_opts: new pointer is too large! \n");
break;
}
}
/* OPTIONS header not found */
#if HOPBYHOP
if ( temp != MASK_HOPOPTS ) return 0;
#else
if ( temp != MASK_DSTOPTS ) return 0;
#endif
if (len < (int)sizeof(struct ipv6_opt_hdr)){
*hotdrop = 1;
return 0;
}
if (len < hdrlen){
/* Packet smaller than it's length field */
return 0;
}
oh = skb_header_pointer(skb, ptr, sizeof(_optsh), &_optsh);
BUG_ON(oh == NULL);
DEBUGP("IPv6 OPTS LEN %u %u ", hdrlen, oh->hdrlen);
DEBUGP("len %02X %04X %02X ",
optinfo->hdrlen, hdrlen,
(!(optinfo->flags & IP6T_OPTS_LEN) ||
((optinfo->hdrlen == hdrlen) ^
!!(optinfo->invflags & IP6T_OPTS_INV_LEN))));
ret = (oh != NULL)
&&
(!(optinfo->flags & IP6T_OPTS_LEN) ||
((optinfo->hdrlen == hdrlen) ^
!!(optinfo->invflags & IP6T_OPTS_INV_LEN)));
ptr += 2;
hdrlen -= 2;
if ( !(optinfo->flags & IP6T_OPTS_OPTS) ){
return ret;
} else if (optinfo->flags & IP6T_OPTS_NSTRICT) {
DEBUGP("Not strict - not implemented");
} else {
DEBUGP("Strict ");
DEBUGP("#%d ",optinfo->optsnr);
for(temp=0; temp<optinfo->optsnr; temp++){
/* type field exists ? */
if (hdrlen < 1)
break;
tp = skb_header_pointer(skb, ptr, sizeof(_opttype),
&_opttype);
if (tp == NULL)
break;
/* Type check */
if (*tp != (optinfo->opts[temp] & 0xFF00)>>8){
DEBUGP("Tbad %02X %02X\n",
*tp,
(optinfo->opts[temp] & 0xFF00)>>8);
return 0;
} else {
DEBUGP("Tok ");
}
/* Length check */
if (*tp) {
u16 spec_len;
/* length field exists ? */
if (hdrlen < 2)
break;
lp = skb_header_pointer(skb, ptr + 1,
sizeof(_optlen),
&_optlen);
if (lp == NULL)
break;
spec_len = optinfo->opts[temp] & 0x00FF;
if (spec_len != 0x00FF && spec_len != *lp) {
DEBUGP("Lbad %02X %04X\n", *lp,
spec_len);
return 0;
}
DEBUGP("Lok ");
optlen = *lp + 2;
} else {
DEBUGP("Pad1\n");
optlen = 1;
}
/* Step to the next */
DEBUGP("len%04X \n", optlen);
if ((ptr > skb->len - optlen || hdrlen < optlen) &&
(temp < optinfo->optsnr - 1)) {
DEBUGP("new pointer is too large! \n");
break;
}
ptr += optlen;
hdrlen -= optlen;
}
if (temp == optinfo->optsnr)
return ret;
else return 0;
}
return 0;
}
/* 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_opts *optsinfo = matchinfo;
if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_opts))) {
DEBUGP("ip6t_opts: matchsize %u != %u\n",
matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_opts)));
return 0;
}
if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) {
DEBUGP("ip6t_opts: unknown flags %X\n",
optsinfo->invflags);
return 0;
}
return 1;
}
static struct ip6t_match opts_match = {
#if HOPBYHOP
.name = "hbh",
#else
.name = "dst",
#endif
.match = &match,
.checkentry = &checkentry,
.me = THIS_MODULE,
};
static int __init init(void)
{
return ip6t_register_match(&opts_match);
}
static void __exit cleanup(void)
{
ip6t_unregister_match(&opts_match);
}
module_init(init);
module_exit(cleanup);
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