[net-next-2.6.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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
#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 void xt_osf_finger_free_rcu(struct rcu_head *rcu_head)
{
	struct xt_osf_finger *f = container_of(rcu_head, struct xt_osf_finger, rcu_head);

	kfree(f);
}

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);
		call_rcu(&sf->rcu_head, xt_osf_finger_free_rcu);

		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;

	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) {
		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)) {
			int foptsize, optnum;

			/*
			 * 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(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(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(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);
			call_rcu(&f->rcu_head, xt_osf_finger_free_rcu);
		}
	}
	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_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
	16	* along with this program; if not, write to the Free Software
	17	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	18	*/
8bee4bad	19	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11eeef41 EP	20	#include <linux/module.h>
	21	#include <linux/kernel.h>
	22
	23	#include <linux/if.h>
	24	#include <linux/inetdevice.h>
	25	#include <linux/ip.h>
	26	#include <linux/list.h>
	27	#include <linux/rculist.h>
	28	#include <linux/skbuff.h>
	29	#include <linux/slab.h>
	30	#include <linux/tcp.h>
	31
	32	#include <net/ip.h>
	33	#include <net/tcp.h>
	34
	35	#include <linux/netfilter/nfnetlink.h>
	36	#include <linux/netfilter/x_tables.h>
	37	#include <net/netfilter/nf_log.h>
	38	#include <linux/netfilter/xt_osf.h>
	39
	40	struct xt_osf_finger {
	41	struct rcu_head rcu_head;
	42	struct list_head finger_entry;
	43	struct xt_osf_user_finger finger;
	44	};
	45
	46	enum osf_fmatch_states {
	47	/* Packet does not match the fingerprint */
	48	FMATCH_WRONG = 0,
	49	/* Packet matches the fingerprint */
	50	FMATCH_OK,
	51	/* Options do not match the fingerprint, but header does */
	52	FMATCH_OPT_WRONG,
	53	};
	54
	55	/*
	56	* Indexed by dont-fragment bit.
	57	* It is the only constant value in the fingerprint.
	58	*/
	59	static struct list_head xt_osf_fingers[2];
	60
	61	static const struct nla_policy xt_osf_policy[OSF_ATTR_MAX + 1] = {
	62	[OSF_ATTR_FINGER] = { .len = sizeof(struct xt_osf_user_finger) },
	63	};
	64
	65	static void xt_osf_finger_free_rcu(struct rcu_head *rcu_head)
	66	{
	67	struct xt_osf_finger *f = container_of(rcu_head, struct xt_osf_finger, rcu_head);
	68
	69	kfree(f);
	70	}
	71
	72	static int xt_osf_add_callback(struct sock ctnl, struct sk_buff skb,
39938324 PM	73	const struct nlmsghdr *nlh,
39938324 PM	74	const struct nlattr * const osf_attrs[])
11eeef41 EP	75	{
	76	struct xt_osf_user_finger *f;
	77	struct xt_osf_finger kf = NULL, sf;
	78	int err = 0;
	79
	80	if (!osf_attrs[OSF_ATTR_FINGER])
	81	return -EINVAL;
	82
	83	if (!(nlh->nlmsg_flags & NLM_F_CREATE))
	84	return -EINVAL;
	85
	86	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
	87
	88	kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL);
	89	if (!kf)
	90	return -ENOMEM;
	91
	92	memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger));
	93
	94	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
	95	if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
	96	continue;
	97
	98	kfree(kf);
	99	kf = NULL;
	100
	101	if (nlh->nlmsg_flags & NLM_F_EXCL)
	102	err = -EEXIST;
	103	break;
	104	}
	105
	106	/*
	107	* We are protected by nfnl mutex.
	108	*/
	109	if (kf)
	110	list_add_tail_rcu(&kf->finger_entry, &xt_osf_fingers[!!f->df]);
	111
	112	return err;
	113	}
	114
	115	static int xt_osf_remove_callback(struct sock ctnl, struct sk_buff skb,
39938324 PM	116	const struct nlmsghdr *nlh,
39938324 PM	117	const struct nlattr * const osf_attrs[])
11eeef41 EP	118	{
	119	struct xt_osf_user_finger *f;
	120	struct xt_osf_finger *sf;
d667b9cf	121	int err = -ENOENT;
11eeef41 EP	122
	123	if (!osf_attrs[OSF_ATTR_FINGER])
	124	return -EINVAL;
	125
	126	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
	127
	128	list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
	129	if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
	130	continue;
	131
	132	/*
	133	* We are protected by nfnl mutex.
	134	*/
	135	list_del_rcu(&sf->finger_entry);
	136	call_rcu(&sf->rcu_head, xt_osf_finger_free_rcu);
	137
	138	err = 0;
	139	break;
	140	}
	141
	142	return err;
	143	}
	144
	145	static const struct nfnl_callback xt_osf_nfnetlink_callbacks[OSF_MSG_MAX] = {
	146	[OSF_MSG_ADD] = {
	147	.call = xt_osf_add_callback,
	148	.attr_count = OSF_ATTR_MAX,
	149	.policy = xt_osf_policy,
	150	},
	151	[OSF_MSG_REMOVE] = {
	152	.call = xt_osf_remove_callback,
	153	.attr_count = OSF_ATTR_MAX,
	154	.policy = xt_osf_policy,
	155	},
	156	};
	157
	158	static const struct nfnetlink_subsystem xt_osf_nfnetlink = {
	159	.name = "osf",
	160	.subsys_id = NFNL_SUBSYS_OSF,
	161	.cb_count = OSF_MSG_MAX,
	162	.cb = xt_osf_nfnetlink_callbacks,
	163	};
	164
	165	static inline int xt_osf_ttl(const struct sk_buff skb, const struct xt_osf_info info,
	166	unsigned char f_ttl)
	167	{
	168	const struct iphdr *ip = ip_hdr(skb);
	169
	170	if (info->flags & XT_OSF_TTL) {
	171	if (info->ttl == XT_OSF_TTL_TRUE)
	172	return ip->ttl == f_ttl;
	173	if (info->ttl == XT_OSF_TTL_NOCHECK)
	174	return 1;
	175	else if (ip->ttl <= f_ttl)
	176	return 1;
	177	else {
	178	struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
	179	int ret = 0;
	180
	181	for_ifa(in_dev) {
	182	if (inet_ifa_match(ip->saddr, ifa)) {
	183	ret = (ip->ttl == f_ttl);
	184	break;
	185	}
186	}
187	endfor_ifa(in_dev);
188
189	return ret;
190	}
191	}
192
193	return ip->ttl == f_ttl;
194	}
195
4b560b44	196	static bool
62fc8051	197	xt_osf_match_packet(const struct sk_buff skb, struct xt_action_param p)
11eeef41 EP	198	{
	199	const struct xt_osf_info *info = p->matchinfo;
	200	const struct iphdr *ip = ip_hdr(skb);
	201	const struct tcphdr *tcp;
	202	struct tcphdr _tcph;
	203	int fmatch = FMATCH_WRONG, fcount = 0;
	204	unsigned int optsize = 0, check_WSS = 0;
	205	u16 window, totlen, mss = 0;
	206	bool df;
	207	const unsigned char optp = NULL, _optp = NULL;
	208	unsigned char opts[MAX_IPOPTLEN];
	209	const struct xt_osf_finger *kf;
	210	const struct xt_osf_user_finger *f;
	211
	212	if (!info)
	213	return false;
	214
	215	tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
	216	if (!tcp)
	217	return false;
	218
	219	if (!tcp->syn)
	220	return false;
	221
	222	totlen = ntohs(ip->tot_len);
	223	df = ntohs(ip->frag_off) & IP_DF;
	224	window = ntohs(tcp->window);
	225
	226	if (tcp->doff * 4 > sizeof(struct tcphdr)) {
	227	optsize = tcp->doff * 4 - sizeof(struct tcphdr);
	228
	229	_optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) +
	230	sizeof(struct tcphdr), optsize, opts);
	231	}
	232
	233	rcu_read_lock();
	234	list_for_each_entry_rcu(kf, &xt_osf_fingers[df], finger_entry) {
	235	f = &kf->finger;
	236
	237	if (!(info->flags & XT_OSF_LOG) && strcmp(info->genre, f->genre))
	238	continue;
	239
	240	optp = _optp;
	241	fmatch = FMATCH_WRONG;
	242
	243	if (totlen == f->ss && xt_osf_ttl(skb, info, f->ttl)) {
	244	int foptsize, optnum;
	245
	246	/*
	247	* Should not happen if userspace parser was written correctly.
	248	*/
	249	if (f->wss.wc >= OSF_WSS_MAX)
	250	continue;
	251
	252	/* Check options */
	253
	254	foptsize = 0;
	255	for (optnum = 0; optnum < f->opt_num; ++optnum)
	256	foptsize += f->opt[optnum].length;
	257
	258	if (foptsize > MAX_IPOPTLEN \|\|
	259	optsize > MAX_IPOPTLEN \|\|
	260	optsize != foptsize)
	261	continue;
262
263	check_WSS = f->wss.wc;
264
265	for (optnum = 0; optnum < f->opt_num; ++optnum) {
266	if (f->opt[optnum].kind == (*optp)) {
267	__u32 len = f->opt[optnum].length;
268	const __u8 *optend = optp + len;
269	int loop_cont = 0;
270
271	fmatch = FMATCH_OK;
272
273	switch (*optp) {
274	case OSFOPT_MSS:
275	mss = optp[3];
276	mss <<= 8;
277	mss \|= optp[2];
278
279	mss = ntohs(mss);
280	break;
281	case OSFOPT_TS:
282	loop_cont = 1;
283	break;
284	}
285
286	optp = optend;
287	} else
288	fmatch = FMATCH_OPT_WRONG;
289
290	if (fmatch != FMATCH_OK)
291	break;
292	}
293
294	if (fmatch != FMATCH_OPT_WRONG) {
295	fmatch = FMATCH_WRONG;
296
297	switch (check_WSS) {
298	case OSF_WSS_PLAIN:
299	if (f->wss.val == 0 \|\| window == f->wss.val)
300	fmatch = FMATCH_OK;
301	break;
302	case OSF_WSS_MSS:
303	/*
304	* Some smart modems decrease mangle MSS to
305	* SMART_MSS_2, so we check standard, decreased
306	* and the one provided in the fingerprint MSS
307	* values.
308	*/
309	#define SMART_MSS_1 1460
310	#define SMART_MSS_2 1448
311	if (window == f->wss.val * mss \|\|
312	window == f->wss.val * SMART_MSS_1 \|\|
313	window == f->wss.val * SMART_MSS_2)
314	fmatch = FMATCH_OK;
315	break;
316	case OSF_WSS_MTU:
317	if (window == f->wss.val * (mss + 40) \|\|
318	window == f->wss.val * (SMART_MSS_1 + 40) \|\|
319	window == f->wss.val * (SMART_MSS_2 + 40))
320	fmatch = FMATCH_OK;
321	break;
322	case OSF_WSS_MODULO:
323	if ((window % f->wss.val) == 0)
324	fmatch = FMATCH_OK;
325	break;
326	}
327	}
328
329	if (fmatch != FMATCH_OK)
330	continue;
331
332	fcount++;
333
334	if (info->flags & XT_OSF_LOG)
aa6a03eb PM	335	nf_log_packet(p->family, p->hooknum, skb,
aa6a03eb PM	336	p->in, p->out, NULL,
7f635d0d	337	"%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n",
11eeef41 EP	338	f->genre, f->version, f->subtype,
	339	&ip->saddr, ntohs(tcp->source),
	340	&ip->daddr, ntohs(tcp->dest),
	341	f->ttl - ip->ttl);
	342
	343	if ((info->flags & XT_OSF_LOG) &&
	344	info->loglevel == XT_OSF_LOGLEVEL_FIRST)
	345	break;
	346	}
	347	}
	348	rcu_read_unlock();
	349
	350	if (!fcount && (info->flags & XT_OSF_LOG))
aa6a03eb	351	nf_log_packet(p->family, p->hooknum, skb, p->in, p->out, NULL,
7f635d0d	352	"Remote OS is not known: %pI4:%u -> %pI4:%u\n",
11eeef41 EP	353	&ip->saddr, ntohs(tcp->source),
	354	&ip->daddr, ntohs(tcp->dest));
	355
	356	if (fcount)
	357	fmatch = FMATCH_OK;
	358
	359	return fmatch == FMATCH_OK;
	360	}
	361
	362	static struct xt_match xt_osf_match = {
	363	.name = "osf",
	364	.revision = 0,
	365	.family = NFPROTO_IPV4,
	366	.proto = IPPROTO_TCP,
	367	.hooks = (1 << NF_INET_LOCAL_IN) \|
	368	(1 << NF_INET_PRE_ROUTING) \|
	369	(1 << NF_INET_FORWARD),
	370	.match = xt_osf_match_packet,
	371	.matchsize = sizeof(struct xt_osf_info),
	372	.me = THIS_MODULE,
	373	};
	374
	375	static int __init xt_osf_init(void)
	376	{
	377	int err = -EINVAL;
	378	int i;
	379
	380	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i)
	381	INIT_LIST_HEAD(&xt_osf_fingers[i]);
	382
	383	err = nfnetlink_subsys_register(&xt_osf_nfnetlink);
	384	if (err < 0) {
8bee4bad	385	pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err);
11eeef41 EP	386	goto err_out_exit;
	387	}
	388
	389	err = xt_register_match(&xt_osf_match);
	390	if (err) {
8bee4bad JE	391	pr_err("Failed to register OS fingerprint "
8bee4bad JE	392	"matching module (%d)\n", err);
11eeef41 EP	393	goto err_out_remove;
	394	}
	395
	396	return 0;
	397
	398	err_out_remove:
	399	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
	400	err_out_exit:
	401	return err;
	402	}
	403
	404	static void __exit xt_osf_fini(void)
	405	{
	406	struct xt_osf_finger *f;
	407	int i;
	408
	409	nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
	410	xt_unregister_match(&xt_osf_match);
	411
	412	rcu_read_lock();
	413	for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i) {
	414
	415	list_for_each_entry_rcu(f, &xt_osf_fingers[i], finger_entry) {
	416	list_del_rcu(&f->finger_entry);
	417	call_rcu(&f->rcu_head, xt_osf_finger_free_rcu);
	418	}
	419	}
	420	rcu_read_unlock();
	421
	422	rcu_barrier();
	423	}
	424
	425	module_init(xt_osf_init);
	426	module_exit(xt_osf_fini);
	427
	428	MODULE_LICENSE("GPL");
	429	MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
	430	MODULE_DESCRIPTION("Passive OS fingerprint matching.");
	431	MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_OSF);