ipvs: convert lblc scheduler to rcu
[linux-3.10.git] / net / netfilter / xt_osf.c
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  */
19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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 int xt_osf_add_callback(struct sock *ctnl, struct sk_buff *skb,
66                                const struct nlmsghdr *nlh,
67                                const struct nlattr * const osf_attrs[])
68 {
69         struct xt_osf_user_finger *f;
70         struct xt_osf_finger *kf = NULL, *sf;
71         int err = 0;
72
73         if (!osf_attrs[OSF_ATTR_FINGER])
74                 return -EINVAL;
75
76         if (!(nlh->nlmsg_flags & NLM_F_CREATE))
77                 return -EINVAL;
78
79         f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
80
81         kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL);
82         if (!kf)
83                 return -ENOMEM;
84
85         memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger));
86
87         list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
88                 if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
89                         continue;
90
91                 kfree(kf);
92                 kf = NULL;
93
94                 if (nlh->nlmsg_flags & NLM_F_EXCL)
95                         err = -EEXIST;
96                 break;
97         }
98
99         /*
100          * We are protected by nfnl mutex.
101          */
102         if (kf)
103                 list_add_tail_rcu(&kf->finger_entry, &xt_osf_fingers[!!f->df]);
104
105         return err;
106 }
107
108 static int xt_osf_remove_callback(struct sock *ctnl, struct sk_buff *skb,
109                                   const struct nlmsghdr *nlh,
110                                   const struct nlattr * const osf_attrs[])
111 {
112         struct xt_osf_user_finger *f;
113         struct xt_osf_finger *sf;
114         int err = -ENOENT;
115
116         if (!osf_attrs[OSF_ATTR_FINGER])
117                 return -EINVAL;
118
119         f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
120
121         list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) {
122                 if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger)))
123                         continue;
124
125                 /*
126                  * We are protected by nfnl mutex.
127                  */
128                 list_del_rcu(&sf->finger_entry);
129                 kfree_rcu(sf, rcu_head);
130
131                 err = 0;
132                 break;
133         }
134
135         return err;
136 }
137
138 static const struct nfnl_callback xt_osf_nfnetlink_callbacks[OSF_MSG_MAX] = {
139         [OSF_MSG_ADD]   = {
140                 .call           = xt_osf_add_callback,
141                 .attr_count     = OSF_ATTR_MAX,
142                 .policy         = xt_osf_policy,
143         },
144         [OSF_MSG_REMOVE]        = {
145                 .call           = xt_osf_remove_callback,
146                 .attr_count     = OSF_ATTR_MAX,
147                 .policy         = xt_osf_policy,
148         },
149 };
150
151 static const struct nfnetlink_subsystem xt_osf_nfnetlink = {
152         .name                   = "osf",
153         .subsys_id              = NFNL_SUBSYS_OSF,
154         .cb_count               = OSF_MSG_MAX,
155         .cb                     = xt_osf_nfnetlink_callbacks,
156 };
157
158 static inline int xt_osf_ttl(const struct sk_buff *skb, const struct xt_osf_info *info,
159                             unsigned char f_ttl)
160 {
161         const struct iphdr *ip = ip_hdr(skb);
162
163         if (info->flags & XT_OSF_TTL) {
164                 if (info->ttl == XT_OSF_TTL_TRUE)
165                         return ip->ttl == f_ttl;
166                 if (info->ttl == XT_OSF_TTL_NOCHECK)
167                         return 1;
168                 else if (ip->ttl <= f_ttl)
169                         return 1;
170                 else {
171                         struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
172                         int ret = 0;
173
174                         for_ifa(in_dev) {
175                                 if (inet_ifa_match(ip->saddr, ifa)) {
176                                         ret = (ip->ttl == f_ttl);
177                                         break;
178                                 }
179                         }
180                         endfor_ifa(in_dev);
181
182                         return ret;
183                 }
184         }
185
186         return ip->ttl == f_ttl;
187 }
188
189 static bool
190 xt_osf_match_packet(const struct sk_buff *skb, struct xt_action_param *p)
191 {
192         const struct xt_osf_info *info = p->matchinfo;
193         const struct iphdr *ip = ip_hdr(skb);
194         const struct tcphdr *tcp;
195         struct tcphdr _tcph;
196         int fmatch = FMATCH_WRONG, fcount = 0;
197         unsigned int optsize = 0, check_WSS = 0;
198         u16 window, totlen, mss = 0;
199         bool df;
200         const unsigned char *optp = NULL, *_optp = NULL;
201         unsigned char opts[MAX_IPOPTLEN];
202         const struct xt_osf_finger *kf;
203         const struct xt_osf_user_finger *f;
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) {
228                 f = &kf->finger;
229
230                 if (!(info->flags & XT_OSF_LOG) && strcmp(info->genre, f->genre))
231                         continue;
232
233                 optp = _optp;
234                 fmatch = FMATCH_WRONG;
235
236                 if (totlen == f->ss && xt_osf_ttl(skb, info, f->ttl)) {
237                         int foptsize, optnum;
238
239                         /*
240                          * Should not happen if userspace parser was written correctly.
241                          */
242                         if (f->wss.wc >= OSF_WSS_MAX)
243                                 continue;
244
245                         /* Check options */
246
247                         foptsize = 0;
248                         for (optnum = 0; optnum < f->opt_num; ++optnum)
249                                 foptsize += f->opt[optnum].length;
250
251                         if (foptsize > MAX_IPOPTLEN ||
252                                 optsize > MAX_IPOPTLEN ||
253                                 optsize != foptsize)
254                                 continue;
255
256                         check_WSS = f->wss.wc;
257
258                         for (optnum = 0; optnum < f->opt_num; ++optnum) {
259                                 if (f->opt[optnum].kind == (*optp)) {
260                                         __u32 len = f->opt[optnum].length;
261                                         const __u8 *optend = optp + len;
262                                         int loop_cont = 0;
263
264                                         fmatch = FMATCH_OK;
265
266                                         switch (*optp) {
267                                         case OSFOPT_MSS:
268                                                 mss = optp[3];
269                                                 mss <<= 8;
270                                                 mss |= optp[2];
271
272                                                 mss = ntohs((__force __be16)mss);
273                                                 break;
274                                         case OSFOPT_TS:
275                                                 loop_cont = 1;
276                                                 break;
277                                         }
278
279                                         optp = optend;
280                                 } else
281                                         fmatch = FMATCH_OPT_WRONG;
282
283                                 if (fmatch != FMATCH_OK)
284                                         break;
285                         }
286
287                         if (fmatch != FMATCH_OPT_WRONG) {
288                                 fmatch = FMATCH_WRONG;
289
290                                 switch (check_WSS) {
291                                 case OSF_WSS_PLAIN:
292                                         if (f->wss.val == 0 || window == f->wss.val)
293                                                 fmatch = FMATCH_OK;
294                                         break;
295                                 case OSF_WSS_MSS:
296                                         /*
297                                          * Some smart modems decrease mangle MSS to 
298                                          * SMART_MSS_2, so we check standard, decreased
299                                          * and the one provided in the fingerprint MSS
300                                          * values.
301                                          */
302 #define SMART_MSS_1     1460
303 #define SMART_MSS_2     1448
304                                         if (window == f->wss.val * mss ||
305                                             window == f->wss.val * SMART_MSS_1 ||
306                                             window == f->wss.val * SMART_MSS_2)
307                                                 fmatch = FMATCH_OK;
308                                         break;
309                                 case OSF_WSS_MTU:
310                                         if (window == f->wss.val * (mss + 40) ||
311                                             window == f->wss.val * (SMART_MSS_1 + 40) ||
312                                             window == f->wss.val * (SMART_MSS_2 + 40))
313                                                 fmatch = FMATCH_OK;
314                                         break;
315                                 case OSF_WSS_MODULO:
316                                         if ((window % f->wss.val) == 0)
317                                                 fmatch = FMATCH_OK;
318                                         break;
319                                 }
320                         }
321
322                         if (fmatch != FMATCH_OK)
323                                 continue;
324
325                         fcount++;
326
327                         if (info->flags & XT_OSF_LOG)
328                                 nf_log_packet(p->family, p->hooknum, skb,
329                                         p->in, p->out, NULL,
330                                         "%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n",
331                                         f->genre, f->version, f->subtype,
332                                         &ip->saddr, ntohs(tcp->source),
333                                         &ip->daddr, ntohs(tcp->dest),
334                                         f->ttl - ip->ttl);
335
336                         if ((info->flags & XT_OSF_LOG) &&
337                             info->loglevel == XT_OSF_LOGLEVEL_FIRST)
338                                 break;
339                 }
340         }
341         rcu_read_unlock();
342
343         if (!fcount && (info->flags & XT_OSF_LOG))
344                 nf_log_packet(p->family, p->hooknum, skb, p->in, p->out, NULL,
345                         "Remote OS is not known: %pI4:%u -> %pI4:%u\n",
346                                 &ip->saddr, ntohs(tcp->source),
347                                 &ip->daddr, ntohs(tcp->dest));
348
349         if (fcount)
350                 fmatch = FMATCH_OK;
351
352         return fmatch == FMATCH_OK;
353 }
354
355 static struct xt_match xt_osf_match = {
356         .name           = "osf",
357         .revision       = 0,
358         .family         = NFPROTO_IPV4,
359         .proto          = IPPROTO_TCP,
360         .hooks          = (1 << NF_INET_LOCAL_IN) |
361                                 (1 << NF_INET_PRE_ROUTING) |
362                                 (1 << NF_INET_FORWARD),
363         .match          = xt_osf_match_packet,
364         .matchsize      = sizeof(struct xt_osf_info),
365         .me             = THIS_MODULE,
366 };
367
368 static int __init xt_osf_init(void)
369 {
370         int err = -EINVAL;
371         int i;
372
373         for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i)
374                 INIT_LIST_HEAD(&xt_osf_fingers[i]);
375
376         err = nfnetlink_subsys_register(&xt_osf_nfnetlink);
377         if (err < 0) {
378                 pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err);
379                 goto err_out_exit;
380         }
381
382         err = xt_register_match(&xt_osf_match);
383         if (err) {
384                 pr_err("Failed to register OS fingerprint "
385                        "matching module (%d)\n", err);
386                 goto err_out_remove;
387         }
388
389         return 0;
390
391 err_out_remove:
392         nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
393 err_out_exit:
394         return err;
395 }
396
397 static void __exit xt_osf_fini(void)
398 {
399         struct xt_osf_finger *f;
400         int i;
401
402         nfnetlink_subsys_unregister(&xt_osf_nfnetlink);
403         xt_unregister_match(&xt_osf_match);
404
405         rcu_read_lock();
406         for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i) {
407
408                 list_for_each_entry_rcu(f, &xt_osf_fingers[i], finger_entry) {
409                         list_del_rcu(&f->finger_entry);
410                         kfree_rcu(f, rcu_head);
411                 }
412         }
413         rcu_read_unlock();
414
415         rcu_barrier();
416 }
417
418 module_init(xt_osf_init);
419 module_exit(xt_osf_fini);
420
421 MODULE_LICENSE("GPL");
422 MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
423 MODULE_DESCRIPTION("Passive OS fingerprint matching.");
424 MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_OSF);