[linux-2.6-block.git] / net / netfilter / xt_osf.c

/*
 * Copyright (c) 2003+ Evgeniy Polyakov <zbr@ioremap.net>
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>

#include <linux/if.h>
#include <linux/inetdevice.h>
#include <linux/ip.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/tcp.h>

#include <net/ip.h>
#include <net/tcp.h>

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_log.h>
#include <linux/netfilter/xt_osf.h>

struct xt_osf_finger {
	struct rcu_head			rcu_head;
	struct list_head		finger_entry;
	struct xt_osf_user_finger	finger;
};

enum osf_fmatch_states {
	/* Packet does not match the fingerprint */
	FMATCH_WRONG = 0,
	/* Packet matches the fingerprint */
	FMATCH_OK,
	/* Options do not match the fingerprint, but header does */
	FMATCH_OPT_WRONG,
};

/*
 * Indexed by dont-fragment bit.
 * It is the only constant value in the fingerprint.
 */
static struct list_head xt_osf_fingers[2];

static const struct nla_policy xt_osf_policy[OSF_ATTR_MAX + 1] = {
	[OSF_ATTR_FINGER]	= { .len = sizeof(struct xt_osf_user_finger) },
};

static int xt_osf_add_callback(struct sock *ctnl, struct sk_buff *skb,
			       const struct nlmsghdr *nlh,
			       const struct nlattr * const osf_attrs[])
{
	struct xt_osf_user_finger *f;
	struct xt_osf_finger *kf = NULL, *sf;
	int err = 0;

	if (!osf_attrs[OSF_ATTR_FINGER])
		return -EINVAL;

	if (!(nlh->nlmsg_flags & NLM_F_CREATE))
		return -EINVAL;

	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);

	kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL);
	if (!kf)
		return -ENOMEM;

	memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger));

	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
		if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
			continue;

		kfree(kf);
		kf = NULL;

		if (nlh->nlmsg_flags & NLM_F_EXCL)
			err = -EEXIST;
		break;
	}

	/*
	 * We are protected by nfnl mutex.
	 */
	if (kf)
		list_add_tail_rcu(&kf->finger_entry, &xt_osf_fingers[!!f->df]);

	return err;
}

static int xt_osf_remove_callback(struct sock *ctnl, struct sk_buff *skb,
				  const struct nlmsghdr *nlh,
				  const struct nlattr * const osf_attrs[])
{
	struct xt_osf_user_finger *f;
	struct xt_osf_finger *sf;
	int err = -ENOENT;

	if (!osf_attrs[OSF_ATTR_FINGER])
		return -EINVAL;

	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);

	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
		if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
			continue;

		/*
		 * We are protected by nfnl mutex.
		 */
		list_del_rcu(&sf->finger_entry);
		kfree_rcu(sf, rcu_head);

		err = 0;
		break;
	}

	return err;
}

static const struct nfnl_callback xt_osf_nfnetlink_callbacks[OSF_MSG_MAX] = {
	[OSF_MSG_ADD]	= {
		.call		= xt_osf_add_callback,
		.attr_count	= OSF_ATTR_MAX,
		.policy		= xt_osf_policy,
	},
	[OSF_MSG_REMOVE]	= {
		.call		= xt_osf_remove_callback,
		.attr_count	= OSF_ATTR_MAX,
		.policy		= xt_osf_policy,
	},
};

static const struct nfnetlink_subsystem xt_osf_nfnetlink = {
	.name			= "osf",
	.subsys_id		= NFNL_SUBSYS_OSF,
	.cb_count		= OSF_MSG_MAX,
	.cb			= xt_osf_nfnetlink_callbacks,
};

static inline int xt_osf_ttl(const struct sk_buff *skb, const struct xt_osf_info *info,
			    unsigned char f_ttl)
{
	const struct iphdr *ip = ip_hdr(skb);

	if (info->flags & XT_OSF_TTL) {
		if (info->ttl == XT_OSF_TTL_TRUE)
			return ip->ttl == f_ttl;
		if (info->ttl == XT_OSF_TTL_NOCHECK)
			return 1;
		else if (ip->ttl <= f_ttl)
			return 1;
		else {
			struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
			int ret = 0;

			for_ifa(in_dev) {
				if (inet_ifa_match(ip->saddr, ifa)) {
					ret = (ip->ttl == f_ttl);
					break;
				}
			}
			endfor_ifa(in_dev);

			return ret;
		}
	}

	return ip->ttl == f_ttl;
}

static bool
xt_osf_match_packet(const struct sk_buff *skb, struct xt_action_param *p)
{
	const struct xt_osf_info *info = p->matchinfo;
	const struct iphdr *ip = ip_hdr(skb);
	const struct tcphdr *tcp;
	struct tcphdr _tcph;
	int fmatch = FMATCH_WRONG, fcount = 0;
	unsigned int optsize = 0, check_WSS = 0;
	u16 window, totlen, mss = 0;
	bool df;
	const unsigned char *optp = NULL, *_optp = NULL;
	unsigned char opts[MAX_IPOPTLEN];
	const struct xt_osf_finger *kf;
	const struct xt_osf_user_finger *f;
	struct net *net = dev_net(p->in ? p->in : p->out);

	if (!info)
		return false;

	tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
	if (!tcp)
		return false;

	if (!tcp->syn)
		return false;

	totlen = ntohs(ip->tot_len);
	df = ntohs(ip->frag_off) & IP_DF;
	window = ntohs(tcp->window);

	if (tcp->doff * 4 > sizeof(struct tcphdr)) {
		optsize = tcp->doff * 4 - sizeof(struct tcphdr);

		_optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) +
				sizeof(struct tcphdr), optsize, opts);
	}

	rcu_read_lock();
	list_for_each_entry_rcu(kf, &xt_osf_fingers[df], finger_entry) {
		int foptsize, optnum;

		f = &kf->finger;

		if (!(info->flags & XT_OSF_LOG) && strcmp(info->genre, f->genre))
			continue;

		optp = _optp;
		fmatch = FMATCH_WRONG;

		if (totlen != f->ss || !xt_osf_ttl(skb, info, f->ttl))
			continue;

		/*
		 * Should not happen if userspace parser was written correctly.
		 */
		if (f->wss.wc >= OSF_WSS_MAX)
			continue;

		/* Check options */

		foptsize = 0;
		for (optnum = 0; optnum < f->opt_num; ++optnum)
			foptsize += f->opt[optnum].length;

		if (foptsize > MAX_IPOPTLEN ||
		    optsize > MAX_IPOPTLEN ||
		    optsize != foptsize)
			continue;

		check_WSS = f->wss.wc;

		for (optnum = 0; optnum < f->opt_num; ++optnum) {
			if (f->opt[optnum].kind == (*optp)) {
				__u32 len = f->opt[optnum].length;
				const __u8 *optend = optp + len;
				int loop_cont = 0;

				fmatch = FMATCH_OK;

				switch (*optp) {
				case OSFOPT_MSS:
					mss = optp[3];
					mss <<= 8;
					mss |= optp[2];

					mss = ntohs((__force __be16)mss);
					break;
				case OSFOPT_TS:
					loop_cont = 1;
					break;
				}

				optp = optend;
			} else
				fmatch = FMATCH_OPT_WRONG;

			if (fmatch != FMATCH_OK)
				break;
		}

		if (fmatch != FMATCH_OPT_WRONG) {
			fmatch = FMATCH_WRONG;

			switch (check_WSS) {
			case OSF_WSS_PLAIN:
				if (f->wss.val == 0 || window == f->wss.val)
					fmatch = FMATCH_OK;
				break;
			case OSF_WSS_MSS:
				/*
				 * Some smart modems decrease mangle MSS to
				 * SMART_MSS_2, so we check standard, decreased
				 * and the one provided in the fingerprint MSS
				 * values.
				 */
#define SMART_MSS_1	1460
#define SMART_MSS_2	1448
				if (window == f->wss.val * mss ||
				    window == f->wss.val * SMART_MSS_1 ||
				    window == f->wss.val * SMART_MSS_2)
					fmatch = FMATCH_OK;
				break;
			case OSF_WSS_MTU:
				if (window == f->wss.val * (mss + 40) ||
				    window == f->wss.val * (SMART_MSS_1 + 40) ||
				    window == f->wss.val * (SMART_MSS_2 + 40))
					fmatch = FMATCH_OK;
				break;
			case OSF_WSS_MODULO:
				if ((window % f->wss.val) == 0)
					fmatch = FMATCH_OK;
				break;
			}
		}

		if (fmatch != FMATCH_OK)
			continue;

		fcount++;

		if (info->flags & XT_OSF_LOG)
			nf_log_packet(net, p->family, p->hooknum, skb,
				      p->in, p->out, NULL,
				      "%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n",
				      f->genre, f->version, f->subtype,
				      &ip->saddr, ntohs(tcp->source),
				      &ip->daddr, ntohs(tcp->dest),
				      f->ttl - ip->ttl);

		if ((info->flags & XT_OSF_LOG) &&
		    info->loglevel == XT_OSF_LOGLEVEL_FIRST)
			break;
	}
	rcu_read_unlock();

	if (!fcount && (info->flags & XT_OSF_LOG))
		nf_log_packet(net, p->family, p->hooknum, skb, p->in,
			      p->out, NULL,
			"Remote OS is not known: %pI4:%u -> %pI4:%u\n",
				&ip->saddr, ntohs(tcp->source),
				&ip->daddr, ntohs(tcp->dest));

	if (fcount)
		fmatch = FMATCH_OK;

	return fmatch == FMATCH_OK;
}

static struct xt_match xt_osf_match = {
	.name 		= "osf",
	.revision	= 0,
	.family		= NFPROTO_IPV4,
	.proto		= IPPROTO_TCP,
	.hooks      	= (1 << NF_INET_LOCAL_IN) |
				(1 << NF_INET_PRE_ROUTING) |
				(1 << NF_INET_FORWARD),
	.match 		= xt_osf_match_packet,
	.matchsize	= sizeof(struct xt_osf_info),
	.me		= THIS_MODULE,
};

static int __init xt_osf_init(void)
{
	int err = -EINVAL;
	int i;

	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i)
		INIT_LIST_HEAD(&xt_osf_fingers[i]);

	err = nfnetlink_subsys_register(&xt_osf_nfnetlink);
	if (err < 0) {
		pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err);
		goto err_out_exit;
	}

	err = xt_register_match(&xt_osf_match);
	if (err) {
		pr_err("Failed to register OS fingerprint "
		       "matching module (%d)\n", err);
		goto err_out_remove;
	}

	return 0;

err_out_remove:
	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
err_out_exit:
	return err;
}

static void __exit xt_osf_fini(void)
{
	struct xt_osf_finger *f;
	int i;

	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
	xt_unregister_match(&xt_osf_match);

	rcu_read_lock();
	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i) {

		list_for_each_entry_rcu(f, &xt_osf_fingers[i], finger_entry) {
			list_del_rcu(&f->finger_entry);
			kfree_rcu(f, rcu_head);
		}
	}
	rcu_read_unlock();

	rcu_barrier();
}

module_init(xt_osf_init);
module_exit(xt_osf_fini);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
MODULE_DESCRIPTION("Passive OS fingerprint matching.");
MODULE_ALIAS("ipt_osf");
MODULE_ALIAS("ip6t_osf");
MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_OSF);
Commit	Line	Data
11eeef41 EP	1	/*
	2	* Copyright (c) 2003+ Evgeniy Polyakov <zbr@ioremap.net>
	3	*
	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 as published by
	7	* the Free Software Foundation; either version 2 of the License, or
	8	* (at your option) any later version.
	9	*
	10	* This program is distributed in the hope that it will be useful,
	11	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	13	* GNU General Public License for more details.
	14	*
	15	* You should have received a copy of the GNU General Public License
e664eabd	16	* along with this program; if not, see <http://www.gnu.org/licenses/>.
11eeef41	17	*/
8bee4bad	18	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11eeef41 EP	19	#include <linux/module.h>
	20	#include <linux/kernel.h>
	21
	22	#include <linux/if.h>
	23	#include <linux/inetdevice.h>
	24	#include <linux/ip.h>
	25	#include <linux/list.h>
	26	#include <linux/rculist.h>
	27	#include <linux/skbuff.h>
	28	#include <linux/slab.h>
	29	#include <linux/tcp.h>
	30
	31	#include <net/ip.h>
	32	#include <net/tcp.h>
	33
	34	#include <linux/netfilter/nfnetlink.h>
	35	#include <linux/netfilter/x_tables.h>
	36	#include <net/netfilter/nf_log.h>
	37	#include <linux/netfilter/xt_osf.h>
	38
	39	struct xt_osf_finger {
	40	struct rcu_head rcu_head;
	41	struct list_head finger_entry;
	42	struct xt_osf_user_finger finger;
	43	};
	44
	45	enum osf_fmatch_states {
	46	/* Packet does not match the fingerprint */
	47	FMATCH_WRONG = 0,
	48	/* Packet matches the fingerprint */
	49	FMATCH_OK,
	50	/* Options do not match the fingerprint, but header does */
	51	FMATCH_OPT_WRONG,
	52	};
	53
	54	/*
	55	* Indexed by dont-fragment bit.
	56	* It is the only constant value in the fingerprint.
	57	*/
	58	static struct list_head xt_osf_fingers[2];
	59
	60	static const struct nla_policy xt_osf_policy[OSF_ATTR_MAX + 1] = {
	61	[OSF_ATTR_FINGER] = { .len = sizeof(struct xt_osf_user_finger) },
	62	};
	63
11eeef41	64	static int xt_osf_add_callback(struct sock ctnl, struct sk_buff skb,
39938324 PM	65	const struct nlmsghdr *nlh,
39938324 PM	66	const struct nlattr * const osf_attrs[])
11eeef41 EP	67	{
	68	struct xt_osf_user_finger *f;
	69	struct xt_osf_finger kf = NULL, sf;
	70	int err = 0;
	71
	72	if (!osf_attrs[OSF_ATTR_FINGER])
	73	return -EINVAL;
	74
	75	if (!(nlh->nlmsg_flags & NLM_F_CREATE))
	76	return -EINVAL;
	77
	78	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
	79
	80	kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL);
	81	if (!kf)
	82	return -ENOMEM;
	83
	84	memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger));
	85
	86	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
	87	if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
	88	continue;
	89
	90	kfree(kf);
	91	kf = NULL;
	92
	93	if (nlh->nlmsg_flags & NLM_F_EXCL)
	94	err = -EEXIST;
	95	break;
	96	}
	97
	98	/*
	99	* We are protected by nfnl mutex.
	100	*/
	101	if (kf)
	102	list_add_tail_rcu(&kf->finger_entry, &xt_osf_fingers[!!f->df]);
	103
	104	return err;
	105	}
	106
	107	static int xt_osf_remove_callback(struct sock ctnl, struct sk_buff skb,
39938324 PM	108	const struct nlmsghdr *nlh,
39938324 PM	109	const struct nlattr * const osf_attrs[])
11eeef41 EP	110	{
	111	struct xt_osf_user_finger *f;
	112	struct xt_osf_finger *sf;
d667b9cf	113	int err = -ENOENT;
11eeef41 EP	114
	115	if (!osf_attrs[OSF_ATTR_FINGER])
	116	return -EINVAL;
	117
	118	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
	119
	120	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
	121	if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
	122	continue;
	123
	124	/*
	125	* We are protected by nfnl mutex.
	126	*/
	127	list_del_rcu(&sf->finger_entry);
88b4a034	128	kfree_rcu(sf, rcu_head);
11eeef41 EP	129
	130	err = 0;
	131	break;
	132	}
	133
	134	return err;
	135	}
	136
	137	static const struct nfnl_callback xt_osf_nfnetlink_callbacks[OSF_MSG_MAX] = {
	138	[OSF_MSG_ADD] = {
	139	.call = xt_osf_add_callback,
	140	.attr_count = OSF_ATTR_MAX,
	141	.policy = xt_osf_policy,
	142	},
	143	[OSF_MSG_REMOVE] = {
	144	.call = xt_osf_remove_callback,
	145	.attr_count = OSF_ATTR_MAX,
	146	.policy = xt_osf_policy,
	147	},
	148	};
	149
	150	static const struct nfnetlink_subsystem xt_osf_nfnetlink = {
	151	.name = "osf",
	152	.subsys_id = NFNL_SUBSYS_OSF,
	153	.cb_count = OSF_MSG_MAX,
	154	.cb = xt_osf_nfnetlink_callbacks,
	155	};
	156
	157	static inline int xt_osf_ttl(const struct sk_buff skb, const struct xt_osf_info info,
	158	unsigned char f_ttl)
	159	{
	160	const struct iphdr *ip = ip_hdr(skb);
	161
	162	if (info->flags & XT_OSF_TTL) {
	163	if (info->ttl == XT_OSF_TTL_TRUE)
	164	return ip->ttl == f_ttl;
	165	if (info->ttl == XT_OSF_TTL_NOCHECK)
	166	return 1;
	167	else if (ip->ttl <= f_ttl)
	168	return 1;
	169	else {
	170	struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
	171	int ret = 0;
	172
	173	for_ifa(in_dev) {
	174	if (inet_ifa_match(ip->saddr, ifa)) {
	175	ret = (ip->ttl == f_ttl);
	176	break;
	177	}
	178	}
	179	endfor_ifa(in_dev);
	180
	181	return ret;
	182	}
	183	}
	184
	185	return ip->ttl == f_ttl;
	186	}
	187
4b560b44	188	static bool
62fc8051	189	xt_osf_match_packet(const struct sk_buff skb, struct xt_action_param p)
11eeef41 EP	190	{
	191	const struct xt_osf_info *info = p->matchinfo;
	192	const struct iphdr *ip = ip_hdr(skb);
	193	const struct tcphdr *tcp;
	194	struct tcphdr _tcph;
	195	int fmatch = FMATCH_WRONG, fcount = 0;
	196	unsigned int optsize = 0, check_WSS = 0;
	197	u16 window, totlen, mss = 0;
	198	bool df;
	199	const unsigned char optp = NULL, _optp = NULL;
	200	unsigned char opts[MAX_IPOPTLEN];
	201	const struct xt_osf_finger *kf;
	202	const struct xt_osf_user_finger *f;
30e0c6a6	203	struct net *net = dev_net(p->in ? p->in : p->out);
11eeef41 EP	204
	205	if (!info)
	206	return false;
	207
	208	tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
	209	if (!tcp)
	210	return false;
	211
	212	if (!tcp->syn)
	213	return false;
	214
	215	totlen = ntohs(ip->tot_len);
	216	df = ntohs(ip->frag_off) & IP_DF;
	217	window = ntohs(tcp->window);
	218
	219	if (tcp->doff * 4 > sizeof(struct tcphdr)) {
	220	optsize = tcp->doff * 4 - sizeof(struct tcphdr);
	221
	222	_optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) +
	223	sizeof(struct tcphdr), optsize, opts);
	224	}
	225
	226	rcu_read_lock();
	227	list_for_each_entry_rcu(kf, &xt_osf_fingers[df], finger_entry) {
372e2866 JP	228	int foptsize, optnum;
372e2866 JP	229
11eeef41 EP	230	f = &kf->finger;
	231
	232	if (!(info->flags & XT_OSF_LOG) && strcmp(info->genre, f->genre))
	233	continue;
	234
	235	optp = _optp;
	236	fmatch = FMATCH_WRONG;
	237
372e2866 JP	238	if (totlen != f->ss \|\| !xt_osf_ttl(skb, info, f->ttl))
372e2866 JP	239	continue;
11eeef41	240
372e2866 JP	241	/*
	242	* Should not happen if userspace parser was written correctly.
	243	*/
	244	if (f->wss.wc >= OSF_WSS_MAX)
	245	continue;
11eeef41	246
372e2866	247	/* Check options */
11eeef41	248
372e2866 JP	249	foptsize = 0;
	250	for (optnum = 0; optnum < f->opt_num; ++optnum)
	251	foptsize += f->opt[optnum].length;
11eeef41	252
372e2866 JP	253	if (foptsize > MAX_IPOPTLEN \|\|
	254	optsize > MAX_IPOPTLEN \|\|
	255	optsize != foptsize)
	256	continue;
11eeef41	257
372e2866	258	check_WSS = f->wss.wc;
11eeef41	259
372e2866 JP	260	for (optnum = 0; optnum < f->opt_num; ++optnum) {
	261	if (f->opt[optnum].kind == (*optp)) {
	262	__u32 len = f->opt[optnum].length;
	263	const __u8 *optend = optp + len;
	264	int loop_cont = 0;
11eeef41	265
372e2866	266	fmatch = FMATCH_OK;
11eeef41	267
372e2866 JP	268	switch (*optp) {
	269	case OSFOPT_MSS:
	270	mss = optp[3];
	271	mss <<= 8;
	272	mss \|= optp[2];
11eeef41	273
372e2866 JP	274	mss = ntohs((__force __be16)mss);
	275	break;
	276	case OSFOPT_TS:
	277	loop_cont = 1;
	278	break;
	279	}
11eeef41	280
372e2866 JP	281	optp = optend;
	282	} else
	283	fmatch = FMATCH_OPT_WRONG;
11eeef41	284
372e2866 JP	285	if (fmatch != FMATCH_OK)
	286	break;
	287	}
11eeef41	288
372e2866 JP	289	if (fmatch != FMATCH_OPT_WRONG) {
372e2866 JP	290	fmatch = FMATCH_WRONG;
11eeef41	291
372e2866 JP	292	switch (check_WSS) {
	293	case OSF_WSS_PLAIN:
	294	if (f->wss.val == 0 \|\| window == f->wss.val)
	295	fmatch = FMATCH_OK;
	296	break;
	297	case OSF_WSS_MSS:
	298	/*
	299	* Some smart modems decrease mangle MSS to
	300	* SMART_MSS_2, so we check standard, decreased
	301	* and the one provided in the fingerprint MSS
	302	* values.
	303	*/
11eeef41 EP	304	#define SMART_MSS_1 1460
11eeef41 EP	305	#define SMART_MSS_2 1448
372e2866 JP	306	if (window == f->wss.val * mss \|\|
	307	window == f->wss.val * SMART_MSS_1 \|\|
	308	window == f->wss.val * SMART_MSS_2)
	309	fmatch = FMATCH_OK;
	310	break;
	311	case OSF_WSS_MTU:
	312	if (window == f->wss.val * (mss + 40) \|\|
	313	window == f->wss.val * (SMART_MSS_1 + 40) \|\|
	314	window == f->wss.val * (SMART_MSS_2 + 40))
	315	fmatch = FMATCH_OK;
	316	break;
	317	case OSF_WSS_MODULO:
	318	if ((window % f->wss.val) == 0)
	319	fmatch = FMATCH_OK;
	320	break;
11eeef41	321	}
372e2866	322	}
11eeef41	323
372e2866 JP	324	if (fmatch != FMATCH_OK)
372e2866 JP	325	continue;
11eeef41	326
372e2866	327	fcount++;
11eeef41	328
372e2866 JP	329	if (info->flags & XT_OSF_LOG)
	330	nf_log_packet(net, p->family, p->hooknum, skb,
	331	p->in, p->out, NULL,
	332	"%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n",
	333	f->genre, f->version, f->subtype,
	334	&ip->saddr, ntohs(tcp->source),
	335	&ip->daddr, ntohs(tcp->dest),
	336	f->ttl - ip->ttl);
11eeef41	337
372e2866 JP	338	if ((info->flags & XT_OSF_LOG) &&
	339	info->loglevel == XT_OSF_LOGLEVEL_FIRST)
	340	break;
11eeef41 EP	341	}
	342	rcu_read_unlock();
	343
	344	if (!fcount && (info->flags & XT_OSF_LOG))
30e0c6a6 G	345	nf_log_packet(net, p->family, p->hooknum, skb, p->in,
30e0c6a6 G	346	p->out, NULL,
7f635d0d	347	"Remote OS is not known: %pI4:%u -> %pI4:%u\n",
11eeef41 EP	348	&ip->saddr, ntohs(tcp->source),
	349	&ip->daddr, ntohs(tcp->dest));
	350
	351	if (fcount)
	352	fmatch = FMATCH_OK;
	353
	354	return fmatch == FMATCH_OK;
	355	}
	356
	357	static struct xt_match xt_osf_match = {
	358	.name = "osf",
	359	.revision = 0,
	360	.family = NFPROTO_IPV4,
	361	.proto = IPPROTO_TCP,
	362	.hooks = (1 << NF_INET_LOCAL_IN) \|
	363	(1 << NF_INET_PRE_ROUTING) \|
	364	(1 << NF_INET_FORWARD),
	365	.match = xt_osf_match_packet,
	366	.matchsize = sizeof(struct xt_osf_info),
	367	.me = THIS_MODULE,
	368	};
	369
	370	static int __init xt_osf_init(void)
	371	{
	372	int err = -EINVAL;
	373	int i;
	374
	375	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i)
	376	INIT_LIST_HEAD(&xt_osf_fingers[i]);
	377
	378	err = nfnetlink_subsys_register(&xt_osf_nfnetlink);
	379	if (err < 0) {
8bee4bad	380	pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err);
11eeef41 EP	381	goto err_out_exit;
	382	}
	383
	384	err = xt_register_match(&xt_osf_match);
	385	if (err) {
8bee4bad JE	386	pr_err("Failed to register OS fingerprint "
8bee4bad JE	387	"matching module (%d)\n", err);
11eeef41 EP	388	goto err_out_remove;
	389	}
	390
	391	return 0;
	392
	393	err_out_remove:
	394	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
	395	err_out_exit:
	396	return err;
	397	}
	398
	399	static void __exit xt_osf_fini(void)
	400	{
	401	struct xt_osf_finger *f;
	402	int i;
	403
	404	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
	405	xt_unregister_match(&xt_osf_match);
	406
	407	rcu_read_lock();
	408	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i) {
	409
	410	list_for_each_entry_rcu(f, &xt_osf_fingers[i], finger_entry) {
	411	list_del_rcu(&f->finger_entry);
88b4a034	412	kfree_rcu(f, rcu_head);
11eeef41 EP	413	}
	414	}
	415	rcu_read_unlock();
	416
	417	rcu_barrier();
	418	}
	419
	420	module_init(xt_osf_init);
	421	module_exit(xt_osf_fini);
	422
	423	MODULE_LICENSE("GPL");
	424	MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
	425	MODULE_DESCRIPTION("Passive OS fingerprint matching.");
b8ddd9ea KT	426	MODULE_ALIAS("ipt_osf");
b8ddd9ea KT	427	MODULE_ALIAS("ip6t_osf");
11eeef41	428	MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_OSF);