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/* Kernel module to match connection tracking information.
* Superset of Rusty's minimalistic state match.
*
* (C) 2001 Marc Boucher (marc@mbsi.ca).
*
* 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/netfilter/x_tables.h>
#include <linux/netfilter/xt_conntrack.h>
#include <net/netfilter/nf_conntrack.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
MODULE_DESCRIPTION("iptables connection tracking match module");
MODULE_ALIAS("ipt_conntrack");
static int
match(const struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
const struct xt_match *match,
const void *matchinfo,
int offset,
unsigned int protoff,
int *hotdrop)
{
const struct xt_conntrack_info *sinfo = matchinfo;
struct nf_conn *ct;
enum ip_conntrack_info ctinfo;
unsigned int statebit;
ct = nf_ct_get((struct sk_buff *)skb, &ctinfo);
#define FWINV(bool,invflg) ((bool) ^ !!(sinfo->invflags & invflg))
if (ct == &nf_conntrack_untracked)
statebit = XT_CONNTRACK_STATE_UNTRACKED;
else if (ct)
statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
else
statebit = XT_CONNTRACK_STATE_INVALID;
if (sinfo->flags & XT_CONNTRACK_STATE) {
if (ct) {
if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
statebit |= XT_CONNTRACK_STATE_SNAT;
if (test_bit(IPS_DST_NAT_BIT, &ct->status))
statebit |= XT_CONNTRACK_STATE_DNAT;
}
if (FWINV((statebit & sinfo->statemask) == 0,
XT_CONNTRACK_STATE))
return 0;
}
if (ct == NULL) {
if (sinfo->flags & ~XT_CONNTRACK_STATE)
return 0;
return 1;
}
if (sinfo->flags & XT_CONNTRACK_PROTO &&
FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
XT_CONNTRACK_PROTO))
return 0;
if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
XT_CONNTRACK_ORIGSRC))
return 0;
if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
XT_CONNTRACK_ORIGDST))
return 0;
if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
XT_CONNTRACK_REPLSRC))
return 0;
if (sinfo->flags & XT_CONNTRACK_REPLDST &&
FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
XT_CONNTRACK_REPLDST))
return 0;
if (sinfo->flags & XT_CONNTRACK_STATUS &&
FWINV((ct->status & sinfo->statusmask) == 0,
XT_CONNTRACK_STATUS))
return 0;
if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
unsigned long expires = timer_pending(&ct->timeout) ?
(ct->timeout.expires - jiffies)/HZ : 0;
if (FWINV(!(expires >= sinfo->expires_min &&
expires <= sinfo->expires_max),
XT_CONNTRACK_EXPIRES))
return 0;
}
return 1;
}
static int
checkentry(const char *tablename,
const void *ip,
const struct xt_match *match,
void *matchinfo,
unsigned int hook_mask)
{
if (nf_ct_l3proto_try_module_get(match->family) < 0) {
printk(KERN_WARNING "can't load conntrack support for "
"proto=%d\n", match->family);
return 0;
}
return 1;
}
static void destroy(const struct xt_match *match, void *matchinfo)
{
nf_ct_l3proto_module_put(match->family);
}
static struct xt_match conntrack_match = {
.name = "conntrack",
.match = match,
.checkentry = checkentry,
.destroy = destroy,
.matchsize = sizeof(struct xt_conntrack_info),
.family = AF_INET,
.me = THIS_MODULE,
};
static int __init xt_conntrack_init(void)
{
return xt_register_match(&conntrack_match);
}
static void __exit xt_conntrack_fini(void)
{
xt_unregister_match(&conntrack_match);
}
module_init(xt_conntrack_init);
module_exit(xt_conntrack_fini);
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