1/* Netfilter messages via netlink socket. Allows for user space
2 * protocol helpers and general trouble making from userspace.
3 *
4 * (C) 2001 by Jay Schulist <jschlst@samba.org>,
5 * (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
6 * (C) 2005,2007 by Pablo Neira Ayuso <pablo@netfilter.org>
7 *
8 * Initial netfilter messages via netlink development funded and
9 * generally made possible by Network Robots, Inc. (www.networkrobots.com)
10 *
11 * Further development of this code funded by Astaro AG (http://www.astaro.com)
12 *
13 * This software may be used and distributed according to the terms
14 * of the GNU General Public License, incorporated herein by reference.
15 */
16
17#include <linux/module.h>
18#include <linux/types.h>
19#include <linux/socket.h>
20#include <linux/kernel.h>
21#include <linux/major.h>
22#include <linux/timer.h>
23#include <linux/string.h>
24#include <linux/sockios.h>
25#include <linux/net.h>
26#include <linux/fcntl.h>
27#include <linux/skbuff.h>
28#include <asm/uaccess.h>
29#include <asm/system.h>
30#include <net/sock.h>
31#include <net/netlink.h>
32#include <linux/init.h>
33
34#include <linux/netlink.h>
35#include <linux/netfilter/nfnetlink.h>
36
37MODULE_LICENSE("GPL");
38MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
39MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
40
41static char __initdata nfversion[] = "0.30";
42
43static struct sock *nfnl = NULL;
44static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
45static DEFINE_MUTEX(nfnl_mutex);
46
47static void nfnl_lock(void)
48{
49	mutex_lock(&nfnl_mutex);
50}
51
52static int nfnl_trylock(void)
53{
54	return !mutex_trylock(&nfnl_mutex);
55}
56
57static void __nfnl_unlock(void)
58{
59	mutex_unlock(&nfnl_mutex);
60}
61
62static void nfnl_unlock(void)
63{
64	mutex_unlock(&nfnl_mutex);
65	if (nfnl->sk_receive_queue.qlen)
66		nfnl->sk_data_ready(nfnl, 0);
67}
68
69int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
70{
71	nfnl_lock();
72	if (subsys_table[n->subsys_id]) {
73		nfnl_unlock();
74		return -EBUSY;
75	}
76	subsys_table[n->subsys_id] = n;
77	nfnl_unlock();
78
79	return 0;
80}
81EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
82
83int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
84{
85	nfnl_lock();
86	subsys_table[n->subsys_id] = NULL;
87	nfnl_unlock();
88
89	return 0;
90}
91EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
92
93static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
94{
95	u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
96
97	if (subsys_id >= NFNL_SUBSYS_COUNT)
98		return NULL;
99
100	return subsys_table[subsys_id];
101}
102
103static inline struct nfnl_callback *
104nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
105{
106	u_int8_t cb_id = NFNL_MSG_TYPE(type);
107
108	if (cb_id >= ss->cb_count)
109		return NULL;
110
111	return &ss->cb[cb_id];
112}
113
114void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
115		const void *data)
116{
117	struct nfattr *nfa;
118	int size = NFA_LENGTH(attrlen);
119
120	nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
121	nfa->nfa_type = attrtype;
122	nfa->nfa_len  = size;
123	memcpy(NFA_DATA(nfa), data, attrlen);
124	memset(NFA_DATA(nfa) + attrlen, 0, NFA_ALIGN(size) - size);
125}
126EXPORT_SYMBOL_GPL(__nfa_fill);
127
128void nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
129{
130	memset(tb, 0, sizeof(struct nfattr *) * maxattr);
131
132	while (NFA_OK(nfa, len)) {
133		unsigned flavor = NFA_TYPE(nfa);
134		if (flavor && flavor <= maxattr)
135			tb[flavor-1] = nfa;
136		nfa = NFA_NEXT(nfa, len);
137	}
138}
139EXPORT_SYMBOL_GPL(nfattr_parse);
140
141/**
142 * nfnetlink_check_attributes - check and parse nfnetlink attributes
143 *
144 * subsys: nfnl subsystem for which this message is to be parsed
145 * nlmsghdr: netlink message to be checked/parsed
146 * cda: array of pointers, needs to be at least subsys->attr_count big
147 *
148 */
149static int
150nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
151			   struct nlmsghdr *nlh, struct nfattr *cda[])
152{
153	int min_len = NLMSG_SPACE(sizeof(struct nfgenmsg));
154	u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
155	u_int16_t attr_count = subsys->cb[cb_id].attr_count;
156
157	/* check attribute lengths. */
158	if (likely(nlh->nlmsg_len > min_len)) {
159		struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
160		int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
161		nfattr_parse(cda, attr_count, attr, attrlen);
162	}
163
164	/* implicit: if nlmsg_len == min_len, we return 0, and an empty
165	 * (zeroed) cda[] array. The message is valid, but empty. */
166
167	return 0;
168}
169
170int nfnetlink_has_listeners(unsigned int group)
171{
172	return netlink_has_listeners(nfnl, group);
173}
174EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
175
176int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
177{
178	int err = 0;
179
180	NETLINK_CB(skb).dst_group = group;
181	if (echo)
182		atomic_inc(&skb->users);
183	netlink_broadcast(nfnl, skb, pid, group, gfp_any());
184	if (echo)
185		err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);
186
187	return err;
188}
189EXPORT_SYMBOL_GPL(nfnetlink_send);
190
191int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
192{
193	return netlink_unicast(nfnl, skb, pid, flags);
194}
195EXPORT_SYMBOL_GPL(nfnetlink_unicast);
196
197/* Process one complete nfnetlink message. */
198static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
199{
200	struct nfnl_callback *nc;
201	struct nfnetlink_subsystem *ss;
202	int type, err;
203
204	if (security_netlink_recv(skb, CAP_NET_ADMIN))
205		return -EPERM;
206
207	/* All the messages must at least contain nfgenmsg */
208	if (nlh->nlmsg_len < NLMSG_SPACE(sizeof(struct nfgenmsg)))
209		return 0;
210
211	type = nlh->nlmsg_type;
212	ss = nfnetlink_get_subsys(type);
213	if (!ss) {
214#ifdef CONFIG_KMOD
215		/* don't call nfnl_unlock, since it would reenter
216		 * with further packet processing */
217		__nfnl_unlock();
218		request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
219		nfnl_lock();
220		ss = nfnetlink_get_subsys(type);
221		if (!ss)
222#endif
223			return -EINVAL;
224	}
225
226	nc = nfnetlink_find_client(type, ss);
227	if (!nc)
228		return -EINVAL;
229
230	{
231		u_int16_t attr_count =
232			ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
233		struct nfattr *cda[attr_count];
234
235		memset(cda, 0, sizeof(struct nfattr *) * attr_count);
236
237		err = nfnetlink_check_attributes(ss, nlh, cda);
238		if (err < 0)
239			return err;
240		return nc->call(nfnl, skb, nlh, cda);
241	}
242}
243
244static void nfnetlink_rcv(struct sock *sk, int len)
245{
246	unsigned int qlen = 0;
247
248	do {
249		if (nfnl_trylock())
250			return;
251		netlink_run_queue(sk, &qlen, nfnetlink_rcv_msg);
252		__nfnl_unlock();
253	} while (qlen);
254}
255
256static void __exit nfnetlink_exit(void)
257{
258	printk("Removing netfilter NETLINK layer.\n");
259	sock_release(nfnl->sk_socket);
260	return;
261}
262
263static int __init nfnetlink_init(void)
264{
265	printk("Netfilter messages via NETLINK v%s.\n", nfversion);
266
267	nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
268				     nfnetlink_rcv, NULL, THIS_MODULE);
269	if (!nfnl) {
270		printk(KERN_ERR "cannot initialize nfnetlink!\n");
271		return -1;
272	}
273
274	return 0;
275}
276
277module_init(nfnetlink_init);
278module_exit(nfnetlink_exit);
279