xref: /openbsd/sys/net/pf_osfp.c (revision a6445c1d)
1 /*	$OpenBSD: pf_osfp.c,v 1.29 2014/07/22 11:06:10 mpi Exp $ */
2 
3 /*
4  * Copyright (c) 2003 Mike Frantzen <frantzen@w4g.org>
5  *
6  * Permission to use, copy, modify, and distribute this software for any
7  * purpose with or without fee is hereby granted, provided that the above
8  * copyright notice and this permission notice appear in all copies.
9  *
10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17  *
18  */
19 
20 #include <sys/param.h>
21 #include <sys/socket.h>
22 #ifdef _KERNEL
23 # include <sys/systm.h>
24 #include <sys/pool.h>
25 #endif /* _KERNEL */
26 #include <sys/mbuf.h>
27 #include <sys/syslog.h>
28 
29 #include <netinet/in.h>
30 #include <netinet/ip.h>
31 #include <netinet/tcp.h>
32 
33 #include <net/if.h>
34 #include <net/pfvar.h>
35 
36 #include <netinet/ip6.h>
37 
38 
39 #ifdef _KERNEL
40 typedef struct pool pool_t;
41 
42 #else
43 /* Userland equivalents so we can lend code to tcpdump et al. */
44 
45 # include <arpa/inet.h>
46 # include <errno.h>
47 # include <stdio.h>
48 # include <stdlib.h>
49 # include <string.h>
50 # include <netdb.h>
51 # define pool_t			int
52 # define pool_get(pool, flags)	malloc(*(pool))
53 # define pool_put(pool, item)	free(item)
54 # define pool_init(pool, size, a, ao, f, m, p)	(*(pool)) = (size)
55 
56 # ifdef PFDEBUG
57 #  include <sys/stdarg.h>	/* for DPFPRINTF() */
58 # endif /* PFDEBUG */
59 
60 #endif /* _KERNEL */
61 
62 
63 SLIST_HEAD(pf_osfp_list, pf_os_fingerprint) pf_osfp_list;
64 pool_t pf_osfp_entry_pl;
65 pool_t pf_osfp_pl;
66 
67 struct pf_os_fingerprint	*pf_osfp_find(struct pf_osfp_list *,
68 				    struct pf_os_fingerprint *, u_int8_t);
69 struct pf_os_fingerprint	*pf_osfp_find_exact(struct pf_osfp_list *,
70 				    struct pf_os_fingerprint *);
71 void				 pf_osfp_insert(struct pf_osfp_list *,
72 				    struct pf_os_fingerprint *);
73 
74 
75 #ifdef _KERNEL
76 /*
77  * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only)
78  * Returns the list of possible OSes.
79  */
80 struct pf_osfp_enlist *
81 pf_osfp_fingerprint(struct pf_pdesc *pd)
82 {
83 	struct tcphdr	*th = pd->hdr.tcp;
84 	struct ip	*ip = NULL;
85 	struct ip6_hdr	*ip6 = NULL;
86 	char		 hdr[60];
87 
88 	if (pd->proto != IPPROTO_TCP)
89 		return (NULL);
90 
91 	switch (pd->af) {
92 	case AF_INET:
93 		ip = mtod(pd->m, struct ip *);
94 		break;
95 	case AF_INET6:
96 		ip6 = mtod(pd->m, struct ip6_hdr *);
97 		break;
98 	}
99 	if (!pf_pull_hdr(pd->m, pd->off, hdr, th->th_off << 2, NULL, NULL,
100 	    pd->af))
101 		return (NULL);
102 
103 	return (pf_osfp_fingerprint_hdr(ip, ip6, (struct tcphdr *)hdr));
104 }
105 #endif /* _KERNEL */
106 
107 struct pf_osfp_enlist *
108 pf_osfp_fingerprint_hdr(const struct ip *ip, const struct ip6_hdr *ip6,
109     const struct tcphdr *tcp)
110 {
111 	struct pf_os_fingerprint fp, *fpresult;
112 	int cnt, optlen = 0;
113 	const u_int8_t *optp;
114 #ifdef _KERNEL
115 	char srcname[128];
116 #else
117 	char srcname[NI_MAXHOST];
118 #endif
119 
120 	if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN)
121 		return (NULL);
122 	if (ip) {
123 		if ((ip->ip_off & htons(IP_OFFMASK)) != 0)
124 			return (NULL);
125 	}
126 
127 	memset(&fp, 0, sizeof(fp));
128 
129 	if (ip) {
130 #ifndef _KERNEL
131 		struct sockaddr_in sin;
132 #endif
133 
134 		fp.fp_psize = ntohs(ip->ip_len);
135 		fp.fp_ttl = ip->ip_ttl;
136 		if (ip->ip_off & htons(IP_DF))
137 			fp.fp_flags |= PF_OSFP_DF;
138 #ifdef _KERNEL
139 		inet_ntop(AF_INET, &ip->ip_src, srcname, sizeof(srcname));
140 #else
141 		memset(&sin, 0, sizeof(sin));
142 		sin.sin_family = AF_INET;
143 		sin.sin_len = sizeof(struct sockaddr_in);
144 		sin.sin_addr = ip->ip_src;
145 		(void)getnameinfo((struct sockaddr *)&sin,
146 		    sizeof(struct sockaddr_in), srcname, sizeof(srcname),
147 		    NULL, 0, NI_NUMERICHOST);
148 #endif
149 	}
150 #ifdef INET6
151 	else if (ip6) {
152 #ifndef _KERNEL
153 		struct sockaddr_in6 sin6;
154 #endif
155 
156 		/* jumbo payload? */
157 		fp.fp_psize = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen);
158 		fp.fp_ttl = ip6->ip6_hlim;
159 		fp.fp_flags |= PF_OSFP_DF;
160 		fp.fp_flags |= PF_OSFP_INET6;
161 #ifdef _KERNEL
162 		inet_ntop(AF_INET6, &ip6->ip6_src, srcname, sizeof(srcname));
163 #else
164 		memset(&sin6, 0, sizeof(sin6));
165 		sin6.sin6_family = AF_INET6;
166 		sin6.sin6_len = sizeof(struct sockaddr_in6);
167 		sin6.sin6_addr = ip6->ip6_src;
168 		(void)getnameinfo((struct sockaddr *)&sin6,
169 		    sizeof(struct sockaddr_in6), srcname, sizeof(srcname),
170 		    NULL, 0, NI_NUMERICHOST);
171 #endif
172 	}
173 #endif
174 	else
175 		return (NULL);
176 	fp.fp_wsize = ntohs(tcp->th_win);
177 
178 
179 	cnt = (tcp->th_off << 2) - sizeof(*tcp);
180 	optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp));
181 	for (; cnt > 0; cnt -= optlen, optp += optlen) {
182 		if (*optp == TCPOPT_EOL)
183 			break;
184 
185 		fp.fp_optcnt++;
186 		if (*optp == TCPOPT_NOP) {
187 			fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) |
188 			    PF_OSFP_TCPOPT_NOP;
189 			optlen = 1;
190 		} else {
191 			if (cnt < 2)
192 				return (NULL);
193 			optlen = optp[1];
194 			if (optlen > cnt || optlen < 2)
195 				return (NULL);
196 			switch (*optp) {
197 			case TCPOPT_MAXSEG:
198 				if (optlen >= TCPOLEN_MAXSEG)
199 					memcpy(&fp.fp_mss, &optp[2],
200 					    sizeof(fp.fp_mss));
201 				fp.fp_tcpopts = (fp.fp_tcpopts <<
202 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS;
203 				NTOHS(fp.fp_mss);
204 				break;
205 			case TCPOPT_WINDOW:
206 				if (optlen >= TCPOLEN_WINDOW)
207 					memcpy(&fp.fp_wscale, &optp[2],
208 					    sizeof(fp.fp_wscale));
209 				fp.fp_tcpopts = (fp.fp_tcpopts <<
210 				    PF_OSFP_TCPOPT_BITS) |
211 				    PF_OSFP_TCPOPT_WSCALE;
212 				break;
213 			case TCPOPT_SACK_PERMITTED:
214 				fp.fp_tcpopts = (fp.fp_tcpopts <<
215 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK;
216 				break;
217 			case TCPOPT_TIMESTAMP:
218 				if (optlen >= TCPOLEN_TIMESTAMP) {
219 					u_int32_t ts;
220 					memcpy(&ts, &optp[2], sizeof(ts));
221 					if (ts == 0)
222 						fp.fp_flags |= PF_OSFP_TS0;
223 
224 				}
225 				fp.fp_tcpopts = (fp.fp_tcpopts <<
226 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS;
227 				break;
228 			default:
229 				return (NULL);
230 			}
231 		}
232 		optlen = MAX(optlen, 1);	/* paranoia */
233 	}
234 
235 	DPFPRINTF(LOG_NOTICE,
236 	    "fingerprinted %s:%d  %d:%d:%d:%d:%llx (%d) "
237 	    "(TS=%s,M=%s%d,W=%s%d)",
238 	    srcname, ntohs(tcp->th_sport),
239 	    fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0,
240 	    fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt,
241 	    (fp.fp_flags & PF_OSFP_TS0) ? "0" : "",
242 	    (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
243 	    (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
244 	    fp.fp_mss,
245 	    (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
246 	    (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
247 	    fp.fp_wscale);
248 
249 	if ((fpresult = pf_osfp_find(&pf_osfp_list, &fp,
250 	    PF_OSFP_MAXTTL_OFFSET)))
251 		return (&fpresult->fp_oses);
252 	return (NULL);
253 }
254 
255 /* Match a fingerprint ID against a list of OSes */
256 int
257 pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os)
258 {
259 	struct pf_osfp_entry *entry;
260 	int os_class, os_version, os_subtype;
261 	int en_class, en_version, en_subtype;
262 
263 	if (os == PF_OSFP_ANY)
264 		return (1);
265 	if (list == NULL) {
266 		DPFPRINTF(LOG_NOTICE, "osfp no match against %x", os);
267 		return (os == PF_OSFP_UNKNOWN);
268 	}
269 	PF_OSFP_UNPACK(os, os_class, os_version, os_subtype);
270 	SLIST_FOREACH(entry, list, fp_entry) {
271 		PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype);
272 		if ((os_class == PF_OSFP_ANY || en_class == os_class) &&
273 		    (os_version == PF_OSFP_ANY || en_version == os_version) &&
274 		    (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) {
275 			DPFPRINTF(LOG_NOTICE,
276 			    "osfp matched %s %s %s  %x==%x",
277 			    entry->fp_class_nm, entry->fp_version_nm,
278 			    entry->fp_subtype_nm, os, entry->fp_os);
279 			return (1);
280 		}
281 	}
282 	DPFPRINTF(LOG_NOTICE, "fingerprint 0x%x didn't match", os);
283 	return (0);
284 }
285 
286 /* Initialize the OS fingerprint system */
287 void
288 pf_osfp_initialize(void)
289 {
290 	pool_init(&pf_osfp_entry_pl, sizeof(struct pf_osfp_entry), 0, 0, 0,
291 	    "pfosfpen", &pool_allocator_nointr);
292 	pool_init(&pf_osfp_pl, sizeof(struct pf_os_fingerprint), 0, 0, 0,
293 	    "pfosfp", &pool_allocator_nointr);
294 	SLIST_INIT(&pf_osfp_list);
295 }
296 
297 /* Flush the fingerprint list */
298 void
299 pf_osfp_flush(void)
300 {
301 	struct pf_os_fingerprint *fp;
302 	struct pf_osfp_entry *entry;
303 
304 	while ((fp = SLIST_FIRST(&pf_osfp_list))) {
305 		SLIST_REMOVE_HEAD(&pf_osfp_list, fp_next);
306 		while ((entry = SLIST_FIRST(&fp->fp_oses))) {
307 			SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry);
308 			pool_put(&pf_osfp_entry_pl, entry);
309 		}
310 		pool_put(&pf_osfp_pl, fp);
311 	}
312 }
313 
314 
315 /* Add a fingerprint */
316 int
317 pf_osfp_add(struct pf_osfp_ioctl *fpioc)
318 {
319 	struct pf_os_fingerprint *fp, fpadd;
320 	struct pf_osfp_entry *entry;
321 
322 	memset(&fpadd, 0, sizeof(fpadd));
323 	fpadd.fp_tcpopts = fpioc->fp_tcpopts;
324 	fpadd.fp_wsize = fpioc->fp_wsize;
325 	fpadd.fp_psize = fpioc->fp_psize;
326 	fpadd.fp_mss = fpioc->fp_mss;
327 	fpadd.fp_flags = fpioc->fp_flags;
328 	fpadd.fp_optcnt = fpioc->fp_optcnt;
329 	fpadd.fp_wscale = fpioc->fp_wscale;
330 	fpadd.fp_ttl = fpioc->fp_ttl;
331 
332 	DPFPRINTF(LOG_DEBUG,
333 	    "adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d "
334 	    "(TS=%s,M=%s%d,W=%s%d) %x",
335 	    fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm,
336 	    fpioc->fp_os.fp_subtype_nm,
337 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" :
338 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" :
339 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" :
340 	    (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "",
341 	    fpadd.fp_wsize,
342 	    fpadd.fp_ttl,
343 	    (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0,
344 	    (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" :
345 	    (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "",
346 	    fpadd.fp_psize,
347 	    (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt,
348 	    (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "",
349 	    (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
350 	    (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
351 	    fpadd.fp_mss,
352 	    (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
353 	    (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
354 	    fpadd.fp_wscale,
355 	    fpioc->fp_os.fp_os);
356 
357 	if ((fp = pf_osfp_find_exact(&pf_osfp_list, &fpadd))) {
358 		 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
359 			if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os))
360 				return (EEXIST);
361 		}
362 		if ((entry = pool_get(&pf_osfp_entry_pl,
363 		    PR_WAITOK|PR_LIMITFAIL)) == NULL)
364 			return (ENOMEM);
365 	} else {
366 		if ((fp = pool_get(&pf_osfp_pl,
367 		    PR_WAITOK|PR_ZERO|PR_LIMITFAIL)) == NULL)
368 			return (ENOMEM);
369 		fp->fp_tcpopts = fpioc->fp_tcpopts;
370 		fp->fp_wsize = fpioc->fp_wsize;
371 		fp->fp_psize = fpioc->fp_psize;
372 		fp->fp_mss = fpioc->fp_mss;
373 		fp->fp_flags = fpioc->fp_flags;
374 		fp->fp_optcnt = fpioc->fp_optcnt;
375 		fp->fp_wscale = fpioc->fp_wscale;
376 		fp->fp_ttl = fpioc->fp_ttl;
377 		SLIST_INIT(&fp->fp_oses);
378 		if ((entry = pool_get(&pf_osfp_entry_pl,
379 		    PR_WAITOK|PR_LIMITFAIL)) == NULL) {
380 			pool_put(&pf_osfp_pl, fp);
381 			return (ENOMEM);
382 		}
383 		pf_osfp_insert(&pf_osfp_list, fp);
384 	}
385 	memcpy(entry, &fpioc->fp_os, sizeof(*entry));
386 
387 	/* Make sure the strings are NUL terminated */
388 	entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0';
389 	entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0';
390 	entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0';
391 
392 	SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry);
393 
394 #ifdef PFDEBUG
395 	if ((fp = pf_osfp_validate()))
396 		DPFPRINTF(LOG_NOTICE,
397 		    "Invalid fingerprint list");
398 #endif /* PFDEBUG */
399 	return (0);
400 }
401 
402 
403 /* Find a fingerprint in the list */
404 struct pf_os_fingerprint *
405 pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find,
406     u_int8_t ttldiff)
407 {
408 	struct pf_os_fingerprint *f;
409 
410 #define MATCH_INT(_MOD, _DC, _field)					\
411 	if ((f->fp_flags & _DC) == 0) {					\
412 		if ((f->fp_flags & _MOD) == 0) {			\
413 			if (f->_field != find->_field)			\
414 				continue;				\
415 		} else {						\
416 			if (f->_field == 0 || find->_field % f->_field)	\
417 				continue;				\
418 		}							\
419 	}
420 
421 	SLIST_FOREACH(f, list, fp_next) {
422 		if (f->fp_tcpopts != find->fp_tcpopts ||
423 		    f->fp_optcnt != find->fp_optcnt ||
424 		    f->fp_ttl < find->fp_ttl ||
425 		    f->fp_ttl - find->fp_ttl > ttldiff ||
426 		    (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) !=
427 		    (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)))
428 			continue;
429 
430 		MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize)
431 		MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss)
432 		MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale)
433 		if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) {
434 			if (f->fp_flags & PF_OSFP_WSIZE_MSS) {
435 				if (find->fp_mss == 0)
436 					continue;
437 
438 /* Some "smart" NAT devices and DSL routers will tweak the MSS size and
439  * will set it to whatever is suitable for the link type.
440  */
441 #define SMART_MSS	1460
442 				if ((find->fp_wsize % find->fp_mss ||
443 				    find->fp_wsize / find->fp_mss !=
444 				    f->fp_wsize) &&
445 				    (find->fp_wsize % SMART_MSS ||
446 				    find->fp_wsize / SMART_MSS !=
447 				    f->fp_wsize))
448 					continue;
449 			} else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
450 				if (find->fp_mss == 0)
451 					continue;
452 
453 #define MTUOFF	(sizeof(struct ip) + sizeof(struct tcphdr))
454 #define SMART_MTU	(SMART_MSS + MTUOFF)
455 				if ((find->fp_wsize % (find->fp_mss + MTUOFF) ||
456 				    find->fp_wsize / (find->fp_mss + MTUOFF) !=
457 				    f->fp_wsize) &&
458 				    (find->fp_wsize % SMART_MTU ||
459 				    find->fp_wsize / SMART_MTU !=
460 				    f->fp_wsize))
461 					continue;
462 			} else if (f->fp_flags & PF_OSFP_WSIZE_MOD) {
463 				if (f->fp_wsize == 0 || find->fp_wsize %
464 				    f->fp_wsize)
465 					continue;
466 			} else {
467 				if (f->fp_wsize != find->fp_wsize)
468 					continue;
469 			}
470 		}
471 		return (f);
472 	}
473 
474 	return (NULL);
475 }
476 
477 /* Find an exact fingerprint in the list */
478 struct pf_os_fingerprint *
479 pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find)
480 {
481 	struct pf_os_fingerprint *f;
482 
483 	SLIST_FOREACH(f, list, fp_next) {
484 		if (f->fp_tcpopts == find->fp_tcpopts &&
485 		    f->fp_wsize == find->fp_wsize &&
486 		    f->fp_psize == find->fp_psize &&
487 		    f->fp_mss == find->fp_mss &&
488 		    f->fp_flags == find->fp_flags &&
489 		    f->fp_optcnt == find->fp_optcnt &&
490 		    f->fp_wscale == find->fp_wscale &&
491 		    f->fp_ttl == find->fp_ttl)
492 			return (f);
493 	}
494 
495 	return (NULL);
496 }
497 
498 /* Insert a fingerprint into the list */
499 void
500 pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins)
501 {
502 	struct pf_os_fingerprint *f, *prev = NULL;
503 
504 	/* XXX need to go semi tree based.  can key on tcp options */
505 
506 	SLIST_FOREACH(f, list, fp_next)
507 		prev = f;
508 	if (prev)
509 		SLIST_INSERT_AFTER(prev, ins, fp_next);
510 	else
511 		SLIST_INSERT_HEAD(list, ins, fp_next);
512 }
513 
514 /* Fill a fingerprint by its number (from an ioctl) */
515 int
516 pf_osfp_get(struct pf_osfp_ioctl *fpioc)
517 {
518 	struct pf_os_fingerprint *fp;
519 	struct pf_osfp_entry *entry;
520 	int num = fpioc->fp_getnum;
521 	int i = 0;
522 
523 
524 	memset(fpioc, 0, sizeof(*fpioc));
525 	SLIST_FOREACH(fp, &pf_osfp_list, fp_next) {
526 		SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
527 			if (i++ == num) {
528 				fpioc->fp_mss = fp->fp_mss;
529 				fpioc->fp_wsize = fp->fp_wsize;
530 				fpioc->fp_flags = fp->fp_flags;
531 				fpioc->fp_psize = fp->fp_psize;
532 				fpioc->fp_ttl = fp->fp_ttl;
533 				fpioc->fp_wscale = fp->fp_wscale;
534 				fpioc->fp_getnum = num;
535 				memcpy(&fpioc->fp_os, entry,
536 				    sizeof(fpioc->fp_os));
537 				return (0);
538 			}
539 		}
540 	}
541 
542 	return (EBUSY);
543 }
544 
545 
546 /* Validate that each signature is reachable */
547 struct pf_os_fingerprint *
548 pf_osfp_validate(void)
549 {
550 	struct pf_os_fingerprint *f, *f2, find;
551 
552 	SLIST_FOREACH(f, &pf_osfp_list, fp_next) {
553 		memcpy(&find, f, sizeof(find));
554 
555 		/* We do a few MSS/th_win percolations to make things unique */
556 		if (find.fp_mss == 0)
557 			find.fp_mss = 128;
558 		if (f->fp_flags & PF_OSFP_WSIZE_MSS)
559 			find.fp_wsize *= find.fp_mss;
560 		else if (f->fp_flags & PF_OSFP_WSIZE_MTU)
561 			find.fp_wsize *= (find.fp_mss + 40);
562 		else if (f->fp_flags & PF_OSFP_WSIZE_MOD)
563 			find.fp_wsize *= 2;
564 		if (f != (f2 = pf_osfp_find(&pf_osfp_list, &find, 0))) {
565 			if (f2)
566 				DPFPRINTF(LOG_NOTICE,
567 				    "Found \"%s %s %s\" instead of "
568 				    "\"%s %s %s\"\n",
569 				    SLIST_FIRST(&f2->fp_oses)->fp_class_nm,
570 				    SLIST_FIRST(&f2->fp_oses)->fp_version_nm,
571 				    SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm,
572 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
573 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
574 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
575 			else
576 				DPFPRINTF(LOG_NOTICE,
577 				    "Couldn't find \"%s %s %s\"\n",
578 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
579 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
580 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
581 			return (f);
582 		}
583 	}
584 	return (NULL);
585 }
586