1 /*
2 * netfilter module for userspace packet logging daemons
3 *
4 * (C) 2000-2004 by Harald Welte <laforge@netfilter.org>
5 * (C) 1999-2001 Paul `Rusty' Russell
6 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 *
12 * This module accepts two parameters:
13 *
14 * nlbufsiz:
15 * The parameter specifies how big the buffer for each netlink multicast
16 * group is. e.g. If you say nlbufsiz=8192, up to eight kb of packets will
17 * get accumulated in the kernel until they are sent to userspace. It is
18 * NOT possible to allocate more than 128kB, and it is strongly discouraged,
19 * because atomically allocating 128kB inside the network rx softirq is not
20 * reliable. Please also keep in mind that this buffer size is allocated for
21 * each nlgroup you are using, so the total kernel memory usage increases
22 * by that factor.
23 *
24 * Actually you should use nlbufsiz a bit smaller than PAGE_SIZE, since
25 * nlbufsiz is used with alloc_skb, which adds another
26 * sizeof(struct skb_shared_info). Use NLMSG_GOODSIZE instead.
27 *
28 * flushtimeout:
29 * Specify, after how many hundredths of a second the queue should be
30 * flushed even if it is not full yet.
31 */
32
33 #include <linux/module.h>
34 #include <linux/spinlock.h>
35 #include <linux/socket.h>
36 #include <linux/skbuff.h>
37 #include <linux/kernel.h>
38 #include <linux/timer.h>
39 #include <linux/netlink.h>
40 #include <linux/netdevice.h>
41 #include <linux/mm.h>
42 #include <linux/moduleparam.h>
43 #include <linux/netfilter.h>
44 #include <linux/netfilter/x_tables.h>
45 #include <linux/netfilter_ipv4/ipt_ULOG.h>
46 #include <net/netfilter/nf_log.h>
47 #include <net/sock.h>
48 #include <linux/bitops.h>
49 #include <asm/unaligned.h>
50
51 MODULE_LICENSE("GPL");
52 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
53 MODULE_DESCRIPTION("Xtables: packet logging to netlink using ULOG");
54 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NFLOG);
55
56 #define ULOG_NL_EVENT 111 /* Harald's favorite number */
57 #define ULOG_MAXNLGROUPS 32 /* numer of nlgroups */
58
59 #define PRINTR(format, args...) do { if (net_ratelimit()) printk(format , ## args); } while (0)
60
61 static unsigned int nlbufsiz = NLMSG_GOODSIZE;
62 module_param(nlbufsiz, uint, 0400);
63 MODULE_PARM_DESC(nlbufsiz, "netlink buffer size");
64
65 static unsigned int flushtimeout = 10;
66 module_param(flushtimeout, uint, 0600);
67 MODULE_PARM_DESC(flushtimeout, "buffer flush timeout (hundredths of a second)");
68
69 static int nflog = 1;
70 module_param(nflog, bool, 0400);
71 MODULE_PARM_DESC(nflog, "register as internal netfilter logging module");
72
73 /* global data structures */
74
75 typedef struct {
76 unsigned int qlen; /* number of nlmsgs' in the skb */
77 struct nlmsghdr *lastnlh; /* netlink header of last msg in skb */
78 struct sk_buff *skb; /* the pre-allocated skb */
79 struct timer_list timer; /* the timer function */
80 } ulog_buff_t;
81
82 static ulog_buff_t ulog_buffers[ULOG_MAXNLGROUPS]; /* array of buffers */
83
84 static struct sock *nflognl; /* our socket */
85 static DEFINE_SPINLOCK(ulog_lock); /* spinlock */
86
87 /* send one ulog_buff_t to userspace */
ulog_send(unsigned int nlgroupnum)88 static void ulog_send(unsigned int nlgroupnum)
89 {
90 ulog_buff_t *ub = &ulog_buffers[nlgroupnum];
91
92 if (timer_pending(&ub->timer)) {
93 pr_debug("ipt_ULOG: ulog_send: timer was pending, deleting\n");
94 del_timer(&ub->timer);
95 }
96
97 if (!ub->skb) {
98 pr_debug("ipt_ULOG: ulog_send: nothing to send\n");
99 return;
100 }
101
102 /* last nlmsg needs NLMSG_DONE */
103 if (ub->qlen > 1)
104 ub->lastnlh->nlmsg_type = NLMSG_DONE;
105
106 NETLINK_CB(ub->skb).dst_group = nlgroupnum + 1;
107 pr_debug("ipt_ULOG: throwing %d packets to netlink group %u\n",
108 ub->qlen, nlgroupnum + 1);
109 netlink_broadcast(nflognl, ub->skb, 0, nlgroupnum + 1, GFP_ATOMIC);
110
111 ub->qlen = 0;
112 ub->skb = NULL;
113 ub->lastnlh = NULL;
114 }
115
116
117 /* timer function to flush queue in flushtimeout time */
ulog_timer(unsigned long data)118 static void ulog_timer(unsigned long data)
119 {
120 pr_debug("ipt_ULOG: timer function called, calling ulog_send\n");
121
122 /* lock to protect against somebody modifying our structure
123 * from ipt_ulog_target at the same time */
124 spin_lock_bh(&ulog_lock);
125 ulog_send(data);
126 spin_unlock_bh(&ulog_lock);
127 }
128
ulog_alloc_skb(unsigned int size)129 static struct sk_buff *ulog_alloc_skb(unsigned int size)
130 {
131 struct sk_buff *skb;
132 unsigned int n;
133
134 /* alloc skb which should be big enough for a whole
135 * multipart message. WARNING: has to be <= 131000
136 * due to slab allocator restrictions */
137
138 n = max(size, nlbufsiz);
139 skb = alloc_skb(n, GFP_ATOMIC);
140 if (!skb) {
141 PRINTR("ipt_ULOG: can't alloc whole buffer %ub!\n", n);
142
143 if (n > size) {
144 /* try to allocate only as much as we need for
145 * current packet */
146
147 skb = alloc_skb(size, GFP_ATOMIC);
148 if (!skb)
149 PRINTR("ipt_ULOG: can't even allocate %ub\n",
150 size);
151 }
152 }
153
154 return skb;
155 }
156
ipt_ulog_packet(unsigned int hooknum,const struct sk_buff * skb,const struct net_device * in,const struct net_device * out,const struct ipt_ulog_info * loginfo,const char * prefix)157 static void ipt_ulog_packet(unsigned int hooknum,
158 const struct sk_buff *skb,
159 const struct net_device *in,
160 const struct net_device *out,
161 const struct ipt_ulog_info *loginfo,
162 const char *prefix)
163 {
164 ulog_buff_t *ub;
165 ulog_packet_msg_t *pm;
166 size_t size, copy_len;
167 struct nlmsghdr *nlh;
168 struct timeval tv;
169
170 /* ffs == find first bit set, necessary because userspace
171 * is already shifting groupnumber, but we need unshifted.
172 * ffs() returns [1..32], we need [0..31] */
173 unsigned int groupnum = ffs(loginfo->nl_group) - 1;
174
175 /* calculate the size of the skb needed */
176 if (loginfo->copy_range == 0 || loginfo->copy_range > skb->len)
177 copy_len = skb->len;
178 else
179 copy_len = loginfo->copy_range;
180
181 size = NLMSG_SPACE(sizeof(*pm) + copy_len);
182
183 ub = &ulog_buffers[groupnum];
184
185 spin_lock_bh(&ulog_lock);
186
187 if (!ub->skb) {
188 if (!(ub->skb = ulog_alloc_skb(size)))
189 goto alloc_failure;
190 } else if (ub->qlen >= loginfo->qthreshold ||
191 size > skb_tailroom(ub->skb)) {
192 /* either the queue len is too high or we don't have
193 * enough room in nlskb left. send it to userspace. */
194
195 ulog_send(groupnum);
196
197 if (!(ub->skb = ulog_alloc_skb(size)))
198 goto alloc_failure;
199 }
200
201 pr_debug("ipt_ULOG: qlen %d, qthreshold %Zu\n", ub->qlen,
202 loginfo->qthreshold);
203
204 /* NLMSG_PUT contains a hidden goto nlmsg_failure !!! */
205 nlh = NLMSG_PUT(ub->skb, 0, ub->qlen, ULOG_NL_EVENT,
206 sizeof(*pm)+copy_len);
207 ub->qlen++;
208
209 pm = NLMSG_DATA(nlh);
210
211 /* We might not have a timestamp, get one */
212 if (skb->tstamp.tv64 == 0)
213 __net_timestamp((struct sk_buff *)skb);
214
215 /* copy hook, prefix, timestamp, payload, etc. */
216 pm->data_len = copy_len;
217 tv = ktime_to_timeval(skb->tstamp);
218 put_unaligned(tv.tv_sec, &pm->timestamp_sec);
219 put_unaligned(tv.tv_usec, &pm->timestamp_usec);
220 put_unaligned(skb->mark, &pm->mark);
221 pm->hook = hooknum;
222 if (prefix != NULL)
223 strncpy(pm->prefix, prefix, sizeof(pm->prefix));
224 else if (loginfo->prefix[0] != '\0')
225 strncpy(pm->prefix, loginfo->prefix, sizeof(pm->prefix));
226 else
227 *(pm->prefix) = '\0';
228
229 if (in && in->hard_header_len > 0
230 && skb->mac_header != skb->network_header
231 && in->hard_header_len <= ULOG_MAC_LEN) {
232 memcpy(pm->mac, skb_mac_header(skb), in->hard_header_len);
233 pm->mac_len = in->hard_header_len;
234 } else
235 pm->mac_len = 0;
236
237 if (in)
238 strncpy(pm->indev_name, in->name, sizeof(pm->indev_name));
239 else
240 pm->indev_name[0] = '\0';
241
242 if (out)
243 strncpy(pm->outdev_name, out->name, sizeof(pm->outdev_name));
244 else
245 pm->outdev_name[0] = '\0';
246
247 /* copy_len <= skb->len, so can't fail. */
248 if (skb_copy_bits(skb, 0, pm->payload, copy_len) < 0)
249 BUG();
250
251 /* check if we are building multi-part messages */
252 if (ub->qlen > 1)
253 ub->lastnlh->nlmsg_flags |= NLM_F_MULTI;
254
255 ub->lastnlh = nlh;
256
257 /* if timer isn't already running, start it */
258 if (!timer_pending(&ub->timer)) {
259 ub->timer.expires = jiffies + flushtimeout * HZ / 100;
260 add_timer(&ub->timer);
261 }
262
263 /* if threshold is reached, send message to userspace */
264 if (ub->qlen >= loginfo->qthreshold) {
265 if (loginfo->qthreshold > 1)
266 nlh->nlmsg_type = NLMSG_DONE;
267 ulog_send(groupnum);
268 }
269
270 spin_unlock_bh(&ulog_lock);
271
272 return;
273
274 nlmsg_failure:
275 PRINTR("ipt_ULOG: error during NLMSG_PUT\n");
276
277 alloc_failure:
278 PRINTR("ipt_ULOG: Error building netlink message\n");
279
280 spin_unlock_bh(&ulog_lock);
281 }
282
283 static unsigned int
ulog_tg(struct sk_buff * skb,const struct xt_target_param * par)284 ulog_tg(struct sk_buff *skb, const struct xt_target_param *par)
285 {
286 ipt_ulog_packet(par->hooknum, skb, par->in, par->out,
287 par->targinfo, NULL);
288 return XT_CONTINUE;
289 }
290
ipt_logfn(u_int8_t pf,unsigned int hooknum,const struct sk_buff * skb,const struct net_device * in,const struct net_device * out,const struct nf_loginfo * li,const char * prefix)291 static void ipt_logfn(u_int8_t pf,
292 unsigned int hooknum,
293 const struct sk_buff *skb,
294 const struct net_device *in,
295 const struct net_device *out,
296 const struct nf_loginfo *li,
297 const char *prefix)
298 {
299 struct ipt_ulog_info loginfo;
300
301 if (!li || li->type != NF_LOG_TYPE_ULOG) {
302 loginfo.nl_group = ULOG_DEFAULT_NLGROUP;
303 loginfo.copy_range = 0;
304 loginfo.qthreshold = ULOG_DEFAULT_QTHRESHOLD;
305 loginfo.prefix[0] = '\0';
306 } else {
307 loginfo.nl_group = li->u.ulog.group;
308 loginfo.copy_range = li->u.ulog.copy_len;
309 loginfo.qthreshold = li->u.ulog.qthreshold;
310 strlcpy(loginfo.prefix, prefix, sizeof(loginfo.prefix));
311 }
312
313 ipt_ulog_packet(hooknum, skb, in, out, &loginfo, prefix);
314 }
315
ulog_tg_check(const struct xt_tgchk_param * par)316 static bool ulog_tg_check(const struct xt_tgchk_param *par)
317 {
318 const struct ipt_ulog_info *loginfo = par->targinfo;
319
320 if (loginfo->prefix[sizeof(loginfo->prefix) - 1] != '\0') {
321 pr_debug("ipt_ULOG: prefix term %i\n",
322 loginfo->prefix[sizeof(loginfo->prefix) - 1]);
323 return false;
324 }
325 if (loginfo->qthreshold > ULOG_MAX_QLEN) {
326 pr_debug("ipt_ULOG: queue threshold %Zu > MAX_QLEN\n",
327 loginfo->qthreshold);
328 return false;
329 }
330 return true;
331 }
332
333 #ifdef CONFIG_COMPAT
334 struct compat_ipt_ulog_info {
335 compat_uint_t nl_group;
336 compat_size_t copy_range;
337 compat_size_t qthreshold;
338 char prefix[ULOG_PREFIX_LEN];
339 };
340
ulog_tg_compat_from_user(void * dst,void * src)341 static void ulog_tg_compat_from_user(void *dst, void *src)
342 {
343 const struct compat_ipt_ulog_info *cl = src;
344 struct ipt_ulog_info l = {
345 .nl_group = cl->nl_group,
346 .copy_range = cl->copy_range,
347 .qthreshold = cl->qthreshold,
348 };
349
350 memcpy(l.prefix, cl->prefix, sizeof(l.prefix));
351 memcpy(dst, &l, sizeof(l));
352 }
353
ulog_tg_compat_to_user(void __user * dst,void * src)354 static int ulog_tg_compat_to_user(void __user *dst, void *src)
355 {
356 const struct ipt_ulog_info *l = src;
357 struct compat_ipt_ulog_info cl = {
358 .nl_group = l->nl_group,
359 .copy_range = l->copy_range,
360 .qthreshold = l->qthreshold,
361 };
362
363 memcpy(cl.prefix, l->prefix, sizeof(cl.prefix));
364 return copy_to_user(dst, &cl, sizeof(cl)) ? -EFAULT : 0;
365 }
366 #endif /* CONFIG_COMPAT */
367
368 static struct xt_target ulog_tg_reg __read_mostly = {
369 .name = "ULOG",
370 .family = NFPROTO_IPV4,
371 .target = ulog_tg,
372 .targetsize = sizeof(struct ipt_ulog_info),
373 .checkentry = ulog_tg_check,
374 #ifdef CONFIG_COMPAT
375 .compatsize = sizeof(struct compat_ipt_ulog_info),
376 .compat_from_user = ulog_tg_compat_from_user,
377 .compat_to_user = ulog_tg_compat_to_user,
378 #endif
379 .me = THIS_MODULE,
380 };
381
382 static struct nf_logger ipt_ulog_logger = {
383 .name = "ipt_ULOG",
384 .logfn = ipt_logfn,
385 .me = THIS_MODULE,
386 };
387
ulog_tg_init(void)388 static int __init ulog_tg_init(void)
389 {
390 int ret, i;
391
392 pr_debug("ipt_ULOG: init module\n");
393
394 if (nlbufsiz > 128*1024) {
395 printk("Netlink buffer has to be <= 128kB\n");
396 return -EINVAL;
397 }
398
399 /* initialize ulog_buffers */
400 for (i = 0; i < ULOG_MAXNLGROUPS; i++)
401 setup_timer(&ulog_buffers[i].timer, ulog_timer, i);
402
403 nflognl = netlink_kernel_create(&init_net,
404 NETLINK_NFLOG, ULOG_MAXNLGROUPS, NULL,
405 NULL, THIS_MODULE);
406 if (!nflognl)
407 return -ENOMEM;
408
409 ret = xt_register_target(&ulog_tg_reg);
410 if (ret < 0) {
411 netlink_kernel_release(nflognl);
412 return ret;
413 }
414 if (nflog)
415 nf_log_register(NFPROTO_IPV4, &ipt_ulog_logger);
416
417 return 0;
418 }
419
ulog_tg_exit(void)420 static void __exit ulog_tg_exit(void)
421 {
422 ulog_buff_t *ub;
423 int i;
424
425 pr_debug("ipt_ULOG: cleanup_module\n");
426
427 if (nflog)
428 nf_log_unregister(&ipt_ulog_logger);
429 xt_unregister_target(&ulog_tg_reg);
430 netlink_kernel_release(nflognl);
431
432 /* remove pending timers and free allocated skb's */
433 for (i = 0; i < ULOG_MAXNLGROUPS; i++) {
434 ub = &ulog_buffers[i];
435 if (timer_pending(&ub->timer)) {
436 pr_debug("timer was pending, deleting\n");
437 del_timer(&ub->timer);
438 }
439
440 if (ub->skb) {
441 kfree_skb(ub->skb);
442 ub->skb = NULL;
443 }
444 }
445 }
446
447 module_init(ulog_tg_init);
448 module_exit(ulog_tg_exit);
449