xref: /dragonfly/sys/net/pf/pf_osfp.c (revision 6b5c5d0d) 
1 /*	$FreeBSD: src/sys/contrib/pf/net/pf_osfp.c,v 1.4 2004/06/16 23:24:00 mlaier Exp $	*/
2 /*	$OpenBSD: pf_osfp.c,v 1.9 2004/01/04 20:08:42 pvalchev Exp $ */
3 /*	$DragonFly: src/sys/net/pf/pf_osfp.c,v 1.2 2006/12/22 23:44:57 swildner Exp $ */
4 
5 /*
6  * Copyright (c) 2004 The DragonFly Project.  All rights reserved.
7  *
8  * Copyright (c) 2003 Mike Frantzen <frantzen@w4g.org>
9  *
10  * Permission to use, copy, modify, and distribute this software for any
11  * purpose with or without fee is hereby granted, provided that the above
12  * copyright notice and this permission notice appear in all copies.
13  *
14  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
15  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
16  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
17  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
18  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
19  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
20  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
21  *
22  */
23 
24 #include <sys/param.h>
25 #include <sys/socket.h>
26 #ifdef _KERNEL
27 # include <sys/systm.h>
28 # include <vm/vm_zone.h>
29 #endif /* _KERNEL */
30 #include <sys/mbuf.h>
31 
32 #include <netinet/in.h>
33 #include <netinet/in_systm.h>
34 #include <netinet/ip.h>
35 #include <netinet/tcp.h>
36 
37 #include <net/if.h>
38 #include <net/pf/pfvar.h>
39 
40 #ifdef INET6
41 #include <netinet/ip6.h>
42 #endif /* INET6 */
43 
44 
45 #ifdef _KERNEL
46 # define DPFPRINTF(format, x...)		\
47 	if (pf_status.debug >= PF_DEBUG_NOISY)	\
48 		kprintf(format , ##x)
49 typedef vm_zone_t pool_t;
50 
51 #else
52 /* Userland equivalents so we can lend code to tcpdump et al. */
53 
54 # include <arpa/inet.h>
55 # include <errno.h>
56 # include <stdio.h>
57 # include <stdlib.h>
58 # include <string.h>
59 # define pool_t			int
60 # define pool_get(pool, flags)	malloc(*(pool))
61 # define pool_put(pool, item)	free(item)
62 # define pool_init(pool, size, a, ao, f, m, p)	(*(pool)) = (size)
63 
64 # ifdef PFDEBUG
65 #  include <sys/stdarg.h>
66 #  define DPFPRINTF(format, x...)	fprintf(stderr, format , ##x)
67 # else
68 #  define DPFPRINTF(format, x...)	((void)0)
69 # endif /* PFDEBUG */
70 #endif /* _KERNEL */
71 
72 
73 SLIST_HEAD(pf_osfp_list, pf_os_fingerprint) pf_osfp_list;
74 pool_t pf_osfp_entry_pl;
75 pool_t pf_osfp_pl;
76 
77 struct pf_os_fingerprint	*pf_osfp_find(struct pf_osfp_list *,
78 				    struct pf_os_fingerprint *, u_int8_t);
79 struct pf_os_fingerprint	*pf_osfp_find_exact(struct pf_osfp_list *,
80 				    struct pf_os_fingerprint *);
81 void				 pf_osfp_insert(struct pf_osfp_list *,
82 				    struct pf_os_fingerprint *);
83 
84 
85 #ifdef _KERNEL
86 /*
87  * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only)
88  * Returns the list of possible OSes.
89  */
90 struct pf_osfp_enlist *
91 pf_osfp_fingerprint(struct pf_pdesc *pd, struct mbuf *m, int off,
92     const struct tcphdr *tcp)
93 {
94 	struct ip *ip;
95 	char hdr[60];
96 
97 	/* XXX don't have a fingerprint database for IPv6 :-( */
98 	if (pd->af != PF_INET || pd->proto != IPPROTO_TCP || (tcp->th_off << 2)
99 	    < sizeof(*tcp))
100 		return (NULL);
101 
102 	ip = mtod(m, struct ip *);
103 	if (!pf_pull_hdr(m, off, hdr, tcp->th_off << 2, NULL, NULL, pd->af))
104 		return (NULL);
105 
106 	return (pf_osfp_fingerprint_hdr(ip, (struct tcphdr *)hdr));
107 }
108 #endif /* _KERNEL */
109 
110 struct pf_osfp_enlist *
111 pf_osfp_fingerprint_hdr(const struct ip *ip, const struct tcphdr *tcp)
112 {
113 	struct pf_os_fingerprint fp, *fpresult;
114 	int cnt, optlen = 0;
115 	const u_int8_t *optp;
116 
117 	if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN || (ip->ip_off &
118 	    IP_OFFMASK))
119 		return (NULL);
120 
121 	memset(&fp, 0, sizeof(fp));
122 
123 	fp.fp_psize = ip->ip_len;
124 	fp.fp_ttl = ip->ip_ttl;
125 	if (ip->ip_off & IP_DF)
126 		fp.fp_flags |= PF_OSFP_DF;
127 	fp.fp_wsize = ntohs(tcp->th_win);
128 
129 
130 	cnt = (tcp->th_off << 2) - sizeof(*tcp);
131 	optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp));
132 	for (; cnt > 0; cnt -= optlen, optp += optlen) {
133 		if (*optp == TCPOPT_EOL)
134 			break;
135 
136 		fp.fp_optcnt++;
137 		if (*optp == TCPOPT_NOP) {
138 			fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) |
139 			    PF_OSFP_TCPOPT_NOP;
140 			optlen = 1;
141 		} else {
142 			if (cnt < 2)
143 				return (NULL);
144 			optlen = optp[1];
145 			if (optlen > cnt || optlen < 2)
146 				return (NULL);
147 			switch (*optp) {
148 			case TCPOPT_MAXSEG:
149 				if (optlen >= TCPOLEN_MAXSEG)
150 					memcpy(&fp.fp_mss, &optp[2],
151 					    sizeof(fp.fp_mss));
152 				fp.fp_tcpopts = (fp.fp_tcpopts <<
153 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS;
154 				fp.fp_mss = ntohs(fp.fp_mss);
155 				break;
156 			case TCPOPT_WINDOW:
157 				if (optlen >= TCPOLEN_WINDOW)
158 					memcpy(&fp.fp_wscale, &optp[2],
159 					    sizeof(fp.fp_wscale));
160 				fp.fp_wscale = ntohs(fp.fp_wscale);
161 				fp.fp_tcpopts = (fp.fp_tcpopts <<
162 				    PF_OSFP_TCPOPT_BITS) |
163 				    PF_OSFP_TCPOPT_WSCALE;
164 				break;
165 			case TCPOPT_SACK_PERMITTED:
166 				fp.fp_tcpopts = (fp.fp_tcpopts <<
167 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK;
168 				break;
169 			case TCPOPT_TIMESTAMP:
170 				if (optlen >= TCPOLEN_TIMESTAMP) {
171 					u_int32_t ts;
172 					memcpy(&ts, &optp[2], sizeof(ts));
173 					if (ts == 0)
174 						fp.fp_flags |= PF_OSFP_TS0;
175 
176 				}
177 				fp.fp_tcpopts = (fp.fp_tcpopts <<
178 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS;
179 				break;
180 			default:
181 				return (NULL);
182 			}
183 		}
184 		optlen = MAX(optlen, 1);	/* paranoia */
185 	}
186 
187 	DPFPRINTF("fingerprinted %s:%d  %d:%d:%d:%d:%llx (%d) "
188 	    "(TS=%s,M=%s%d,W=%s%d)\n",
189 	    inet_ntoa(ip->ip_src), ntohs(tcp->th_sport),
190 	    fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0,
191 	    fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt,
192 	    (fp.fp_flags & PF_OSFP_TS0) ? "0" : "",
193 	    (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
194 	    (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
195 	    fp.fp_mss,
196 	    (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
197 	    (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
198 	    fp.fp_wscale);
199 
200 	if ((fpresult = pf_osfp_find(&pf_osfp_list, &fp,
201 	    PF_OSFP_MAXTTL_OFFSET)))
202 		return (&fpresult->fp_oses);
203 	return (NULL);
204 }
205 
206 /* Match a fingerprint ID against a list of OSes */
207 int
208 pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os)
209 {
210 	struct pf_osfp_entry *entry;
211 	int os_class, os_version, os_subtype;
212 	int en_class, en_version, en_subtype;
213 
214 	if (os == PF_OSFP_ANY)
215 		return (1);
216 	if (list == NULL) {
217 		DPFPRINTF("osfp no match against %x\n", os);
218 		return (os == PF_OSFP_UNKNOWN);
219 	}
220 	PF_OSFP_UNPACK(os, os_class, os_version, os_subtype);
221 	SLIST_FOREACH(entry, list, fp_entry) {
222 		PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype);
223 		if ((os_class == PF_OSFP_ANY || en_class == os_class) &&
224 		    (os_version == PF_OSFP_ANY || en_version == os_version) &&
225 		    (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) {
226 			DPFPRINTF("osfp matched %s %s %s  %x==%x\n",
227 			    entry->fp_class_nm, entry->fp_version_nm,
228 			    entry->fp_subtype_nm, os, entry->fp_os);
229 			return (1);
230 		}
231 	}
232 	DPFPRINTF("fingerprint 0x%x didn't match\n", os);
233 	return (0);
234 }
235 
236 /* Initialize the OS fingerprint system */
237 int
238 pf_osfp_initialize(void)
239 {
240 	int error = 0;
241 
242 #ifdef _KERNEL
243 	do {
244 		error = ENOMEM;
245 		pf_osfp_entry_pl = pf_osfp_pl = NULL;
246 		ZONE_CREATE(pf_osfp_entry_pl, struct pf_osfp_entry, "pfospfen");
247 		ZONE_CREATE(pf_osfp_pl, struct pf_os_fingerprint, "pfosfp");
248 		error = 0;
249 	} while(0);
250 #else
251 	pool_init(&pf_osfp_entry_pl, sizeof(struct pf_osfp_entry), 0, 0, 0,
252 	    "pfosfpen", NULL);
253 	pool_init(&pf_osfp_pl, sizeof(struct pf_os_fingerprint), 0, 0, 0,
254 	    "pfosfp", NULL);
255 #endif
256 	SLIST_INIT(&pf_osfp_list);
257 
258 	return (error);
259 }
260 
261 #ifdef _KERNEL
262 void
263 pf_osfp_cleanup(void)
264 {
265 	ZONE_DESTROY(pf_osfp_entry_pl);
266 	ZONE_DESTROY(pf_osfp_pl);
267 }
268 #endif
269 
270 /* Flush the fingerprint list */
271 void
272 pf_osfp_flush(void)
273 {
274 	struct pf_os_fingerprint *fp;
275 	struct pf_osfp_entry *entry;
276 
277 	while ((fp = SLIST_FIRST(&pf_osfp_list))) {
278 		SLIST_REMOVE_HEAD(&pf_osfp_list, fp_next);
279 		while ((entry = SLIST_FIRST(&fp->fp_oses))) {
280 			SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry);
281 			pool_put(&pf_osfp_entry_pl, entry);
282 		}
283 		pool_put(&pf_osfp_pl, fp);
284 	}
285 }
286 
287 
288 /* Add a fingerprint */
289 int
290 pf_osfp_add(struct pf_osfp_ioctl *fpioc)
291 {
292 	struct pf_os_fingerprint *fp, fpadd;
293 	struct pf_osfp_entry *entry;
294 
295 	memset(&fpadd, 0, sizeof(fpadd));
296 	fpadd.fp_tcpopts = fpioc->fp_tcpopts;
297 	fpadd.fp_wsize = fpioc->fp_wsize;
298 	fpadd.fp_psize = fpioc->fp_psize;
299 	fpadd.fp_mss = fpioc->fp_mss;
300 	fpadd.fp_flags = fpioc->fp_flags;
301 	fpadd.fp_optcnt = fpioc->fp_optcnt;
302 	fpadd.fp_wscale = fpioc->fp_wscale;
303 	fpadd.fp_ttl = fpioc->fp_ttl;
304 
305 	DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d "
306 	    "(TS=%s,M=%s%d,W=%s%d) %x\n",
307 	    fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm,
308 	    fpioc->fp_os.fp_subtype_nm,
309 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" :
310 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" :
311 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" :
312 	    (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "",
313 	    fpadd.fp_wsize,
314 	    fpadd.fp_ttl,
315 	    (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0,
316 	    (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" :
317 	    (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "",
318 	    fpadd.fp_psize,
319 	    (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt,
320 	    (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "",
321 	    (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
322 	    (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
323 	    fpadd.fp_mss,
324 	    (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
325 	    (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
326 	    fpadd.fp_wscale,
327 	    fpioc->fp_os.fp_os);
328 
329 
330 	if ((fp = pf_osfp_find_exact(&pf_osfp_list, &fpadd))) {
331 		 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
332 			if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os))
333 				return (EEXIST);
334 		}
335 		if ((entry = pool_get(&pf_osfp_entry_pl, PR_NOWAIT)) == NULL)
336 			return (ENOMEM);
337 	} else {
338 		if ((fp = pool_get(&pf_osfp_pl, PR_NOWAIT)) == NULL)
339 			return (ENOMEM);
340 		memset(fp, 0, sizeof(*fp));
341 		fp->fp_tcpopts = fpioc->fp_tcpopts;
342 		fp->fp_wsize = fpioc->fp_wsize;
343 		fp->fp_psize = fpioc->fp_psize;
344 		fp->fp_mss = fpioc->fp_mss;
345 		fp->fp_flags = fpioc->fp_flags;
346 		fp->fp_optcnt = fpioc->fp_optcnt;
347 		fp->fp_wscale = fpioc->fp_wscale;
348 		fp->fp_ttl = fpioc->fp_ttl;
349 		SLIST_INIT(&fp->fp_oses);
350 		if ((entry = pool_get(&pf_osfp_entry_pl, PR_NOWAIT)) == NULL) {
351 			pool_put(&pf_osfp_pl, fp);
352 			return (ENOMEM);
353 		}
354 		pf_osfp_insert(&pf_osfp_list, fp);
355 	}
356 	memcpy(entry, &fpioc->fp_os, sizeof(*entry));
357 
358 	/* Make sure the strings are NUL terminated */
359 	entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0';
360 	entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0';
361 	entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0';
362 
363 	SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry);
364 
365 #ifdef PFDEBUG
366 	if ((fp = pf_osfp_validate()))
367 		kprintf("Invalid fingerprint list\n");
368 #endif /* PFDEBUG */
369 	return (0);
370 }
371 
372 
373 /* Find a fingerprint in the list */
374 struct pf_os_fingerprint *
375 pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find,
376     u_int8_t ttldiff)
377 {
378 	struct pf_os_fingerprint *f;
379 
380 #define MATCH_INT(_MOD, _DC, _field)					\
381 	if ((f->fp_flags & _DC) == 0) {					\
382 		if ((f->fp_flags & _MOD) == 0) {			\
383 			if (f->_field != find->_field)			\
384 				continue;				\
385 		} else {						\
386 			if (f->_field == 0 || find->_field % f->_field)	\
387 				continue;				\
388 		}							\
389 	}
390 
391 	SLIST_FOREACH(f, list, fp_next) {
392 		if (f->fp_tcpopts != find->fp_tcpopts ||
393 		    f->fp_optcnt != find->fp_optcnt ||
394 		    f->fp_ttl < find->fp_ttl ||
395 		    f->fp_ttl - find->fp_ttl > ttldiff ||
396 		    (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) !=
397 		    (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)))
398 			continue;
399 
400 		MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize)
401 		MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss)
402 		MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale)
403 		if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) {
404 			if (f->fp_flags & PF_OSFP_WSIZE_MSS) {
405 				if (find->fp_mss == 0)
406 					continue;
407 
408 /* Some "smart" NAT devices and DSL routers will tweak the MSS size and
409  * will set it to whatever is suitable for the link type.
410  */
411 #define SMART_MSS	1460
412 				if ((find->fp_wsize % find->fp_mss ||
413 				    find->fp_wsize / find->fp_mss !=
414 				    f->fp_wsize) &&
415 				    (find->fp_wsize % SMART_MSS ||
416 				    find->fp_wsize / SMART_MSS !=
417 				    f->fp_wsize))
418 					continue;
419 			} else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
420 				if (find->fp_mss == 0)
421 					continue;
422 
423 #define MTUOFF	(sizeof(struct ip) + sizeof(struct tcphdr))
424 #define SMART_MTU	(SMART_MSS + MTUOFF)
425 				if ((find->fp_wsize % (find->fp_mss + MTUOFF) ||
426 				    find->fp_wsize / (find->fp_mss + MTUOFF) !=
427 				    f->fp_wsize) &&
428 				    (find->fp_wsize % SMART_MTU ||
429 				    find->fp_wsize / SMART_MTU !=
430 				    f->fp_wsize))
431 					continue;
432 			} else if (f->fp_flags & PF_OSFP_WSIZE_MOD) {
433 				if (f->fp_wsize == 0 || find->fp_wsize %
434 				    f->fp_wsize)
435 					continue;
436 			} else {
437 				if (f->fp_wsize != find->fp_wsize)
438 					continue;
439 			}
440 		}
441 		return (f);
442 	}
443 
444 	return (NULL);
445 }
446 
447 /* Find an exact fingerprint in the list */
448 struct pf_os_fingerprint *
449 pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find)
450 {
451 	struct pf_os_fingerprint *f;
452 
453 	SLIST_FOREACH(f, list, fp_next) {
454 		if (f->fp_tcpopts == find->fp_tcpopts &&
455 		    f->fp_wsize == find->fp_wsize &&
456 		    f->fp_psize == find->fp_psize &&
457 		    f->fp_mss == find->fp_mss &&
458 		    f->fp_flags == find->fp_flags &&
459 		    f->fp_optcnt == find->fp_optcnt &&
460 		    f->fp_wscale == find->fp_wscale &&
461 		    f->fp_ttl == find->fp_ttl)
462 			return (f);
463 	}
464 
465 	return (NULL);
466 }
467 
468 /* Insert a fingerprint into the list */
469 void
470 pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins)
471 {
472 	struct pf_os_fingerprint *f, *prev = NULL;
473 
474 	/* XXX need to go semi tree based.  can key on tcp options */
475 
476 	SLIST_FOREACH(f, list, fp_next)
477 		prev = f;
478 	if (prev)
479 		SLIST_INSERT_AFTER(prev, ins, fp_next);
480 	else
481 		SLIST_INSERT_HEAD(list, ins, fp_next);
482 }
483 
484 /* Fill a fingerprint by its number (from an ioctl) */
485 int
486 pf_osfp_get(struct pf_osfp_ioctl *fpioc)
487 {
488 	struct pf_os_fingerprint *fp;
489 	struct pf_osfp_entry *entry;
490 	int num = fpioc->fp_getnum;
491 	int i = 0;
492 
493 
494 	memset(fpioc, 0, sizeof(*fpioc));
495 	SLIST_FOREACH(fp, &pf_osfp_list, fp_next) {
496 		SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
497 			if (i++ == num) {
498 				fpioc->fp_mss = fp->fp_mss;
499 				fpioc->fp_wsize = fp->fp_wsize;
500 				fpioc->fp_flags = fp->fp_flags;
501 				fpioc->fp_psize = fp->fp_psize;
502 				fpioc->fp_ttl = fp->fp_ttl;
503 				fpioc->fp_wscale = fp->fp_wscale;
504 				fpioc->fp_getnum = num;
505 				memcpy(&fpioc->fp_os, entry,
506 				    sizeof(fpioc->fp_os));
507 				return (0);
508 			}
509 		}
510 	}
511 
512 	return (EBUSY);
513 }
514 
515 
516 /* Validate that each signature is reachable */
517 struct pf_os_fingerprint *
518 pf_osfp_validate(void)
519 {
520 	struct pf_os_fingerprint *f, *f2, find;
521 
522 	SLIST_FOREACH(f, &pf_osfp_list, fp_next) {
523 		memcpy(&find, f, sizeof(find));
524 
525 		/* We do a few MSS/th_win percolations to make things unique */
526 		if (find.fp_mss == 0)
527 			find.fp_mss = 128;
528 		if (f->fp_flags & PF_OSFP_WSIZE_MSS)
529 			find.fp_wsize *= find.fp_mss, 1;
530 		else if (f->fp_flags & PF_OSFP_WSIZE_MTU)
531 			find.fp_wsize *= (find.fp_mss + 40);
532 		else if (f->fp_flags & PF_OSFP_WSIZE_MOD)
533 			find.fp_wsize *= 2;
534 		if (f != (f2 = pf_osfp_find(&pf_osfp_list, &find, 0))) {
535 			if (f2)
536 				kprintf("Found \"%s %s %s\" instead of "
537 				    "\"%s %s %s\"\n",
538 				    SLIST_FIRST(&f2->fp_oses)->fp_class_nm,
539 				    SLIST_FIRST(&f2->fp_oses)->fp_version_nm,
540 				    SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm,
541 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
542 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
543 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
544 			else
545 				kprintf("Couldn't find \"%s %s %s\"\n",
546 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
547 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
548 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
549 			return (f);
550 		}
551 	}
552 	return (NULL);
553 }
554