xref: /openbsd/sys/net/pf_osfp.c (revision 1821443c) 
1 /*	$OpenBSD: pf_osfp.c,v 1.3 2003/08/27 18:23:36 frantzen 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 #endif /* _KERNEL */
25 #include <sys/mbuf.h>
26 
27 #include <netinet/in.h>
28 #include <netinet/in_systm.h>
29 #include <netinet/ip.h>
30 #include <netinet/tcp.h>
31 
32 #include <net/if.h>
33 #include <net/pfvar.h>
34 
35 #ifdef INET6
36 #include <netinet/ip6.h>
37 #endif /* INET6 */
38 
39 
40 #ifdef _KERNEL
41 # define DPFPRINTF(format, x...)		\
42 	if (pf_status.debug >= PF_DEBUG_NOISY)	\
43 		printf(format , ##x)
44 typedef struct pool pool_t;
45 
46 #else
47 /* Userland equivalents so we can lend code to tcpdump et al. */
48 
49 # include <arpa/inet.h>
50 # include <errno.h>
51 # include <stdio.h>
52 # include <stdlib.h>
53 # define pool_t			int
54 # define pool_get(pool, flags)	malloc(*(pool))
55 # define pool_put(pool, item)	free(item)
56 # define pool_init(pool, size, a, ao, f, m, p)	(*(pool)) = (size)
57 
58 # ifdef PFDEBUG
59 #  include <stdarg.h>
60 #  define DPFPRINTF(format, x...)	fprintf(stderr, format , ##x)
61 # else
62 #  define DPFPRINTF(format, x...)	((void)0)
63 # endif /* PFDEBUG */
64 #endif /* _KERNEL */
65 
66 
67 SLIST_HEAD(pf_osfp_list, pf_os_fingerprint) pf_osfp_list;
68 pool_t pf_osfp_entry_pl;
69 pool_t pf_osfp_pl;
70 
71 struct pf_os_fingerprint	*pf_osfp_find(struct pf_osfp_list *,
72 				    struct pf_os_fingerprint *, u_int8_t);
73 struct pf_os_fingerprint	*pf_osfp_find_exact(struct pf_osfp_list *,
74 				    struct pf_os_fingerprint *);
75 void				 pf_osfp_insert(struct pf_osfp_list *,
76 				    struct pf_os_fingerprint *);
77 
78 
79 #ifdef _KERNEL
80 /*
81  * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only)
82  * Returns the list of possible OSes.
83  */
84 struct pf_osfp_enlist *
85 pf_osfp_fingerprint(struct pf_pdesc *pd, struct mbuf *m, int off,
86     const struct tcphdr *tcp)
87 {
88 	struct ip *ip;
89 	char hdr[60];
90 
91 	/* XXX don't have a fingerprint database for IPv6 :-( */
92 	if (pd->af != PF_INET || pd->proto != IPPROTO_TCP || (tcp->th_off << 2)
93 	    < sizeof(*tcp))
94 		return (NULL);
95 
96 	ip = mtod(m, struct ip *);
97 	if (!pf_pull_hdr(m, off, hdr, tcp->th_off << 2, NULL, NULL, pd->af))
98 		return (NULL);
99 
100 	return (pf_osfp_fingerprint_hdr(ip, (struct tcphdr *)hdr));
101 }
102 #endif /* _KERNEL */
103 
104 struct pf_osfp_enlist *
105 pf_osfp_fingerprint_hdr(const struct ip *ip, const struct tcphdr *tcp)
106 {
107 	struct pf_os_fingerprint fp, *fpresult;
108 	int cnt, optlen = 0;
109 	u_int8_t *optp;
110 
111 	if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN || (ip->ip_off &
112 	    htons(IP_OFFMASK)))
113 		return (NULL);
114 
115 	memset(&fp, 0, sizeof(fp));
116 
117 	fp.fp_psize = ntohs(ip->ip_len);
118 	fp.fp_ttl = ip->ip_ttl;
119 	if (ip->ip_off & htons(IP_DF))
120 		fp.fp_flags |= PF_OSFP_DF;
121 	fp.fp_wsize = ntohs(tcp->th_win);
122 
123 
124 	cnt = (tcp->th_off << 2) - sizeof(*tcp);
125 	optp = (caddr_t)tcp + sizeof(*tcp);
126 	for (; cnt > 0; cnt -= optlen, optp += optlen) {
127 		if (*optp == TCPOPT_EOL)
128 			break;
129 
130 		fp.fp_optcnt++;
131 		if (*optp == TCPOPT_NOP) {
132 			fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) |
133 			    PF_OSFP_TCPOPT_NOP;
134 			optlen = 1;
135 		} else {
136 			if (cnt < 2)
137 				return (NULL);
138 			optlen = optp[1];
139 			if (optlen > cnt || optlen < 2)
140 				return (NULL);
141 			switch (*optp) {
142 			case TCPOPT_MAXSEG:
143 				if (optlen >= TCPOLEN_MAXSEG)
144 					memcpy(&fp.fp_mss, &optp[2],
145 					    sizeof(fp.fp_mss));
146 				fp.fp_tcpopts = (fp.fp_tcpopts <<
147 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS;
148 				NTOHS(fp.fp_mss);
149 				break;
150 			case TCPOPT_WINDOW:
151 				if (optlen >= TCPOLEN_WINDOW)
152 					memcpy(&fp.fp_wscale, &optp[2],
153 					    sizeof(fp.fp_wscale));
154 				NTOHS(fp.fp_wscale);
155 				fp.fp_tcpopts = (fp.fp_tcpopts <<
156 				    PF_OSFP_TCPOPT_BITS) |
157 				    PF_OSFP_TCPOPT_WSCALE;
158 				break;
159 			case TCPOPT_SACK_PERMITTED:
160 				fp.fp_tcpopts = (fp.fp_tcpopts <<
161 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK;
162 				break;
163 			case TCPOPT_TIMESTAMP:
164 				if (optlen >= TCPOLEN_TIMESTAMP) {
165 					u_int32_t ts;
166 					memcpy(&ts, &optp[2], sizeof(ts));
167 					if (ts == 0)
168 						fp.fp_flags |= PF_OSFP_TS0;
169 
170 				}
171 				fp.fp_tcpopts = (fp.fp_tcpopts <<
172 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS;
173 				break;
174 			default:
175 				return (NULL);
176 			}
177 		}
178 		optlen = MAX(optlen, 1);	/* paranoia */
179 	}
180 
181 	DPFPRINTF("fingerprinted %s:%d  %d:%d:%d:%d:%llx (%d) "
182 	    "(TS=%s,M=%s%d,W=%s%d)\n",
183 	    inet_ntoa(ip->ip_src), ntohs(tcp->th_sport),
184 	    fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0,
185 	    fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt,
186 	    (fp.fp_flags & PF_OSFP_TS0) ? "0" : "",
187 	    (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
188 	    (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
189 	    fp.fp_mss,
190 	    (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
191 	    (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
192 	    fp.fp_wscale);
193 
194 	if ((fpresult = pf_osfp_find(&pf_osfp_list, &fp,
195 	    PF_OSFP_MAXTTL_OFFSET)))
196 		return (&fpresult->fp_oses);
197 	return (NULL);
198 }
199 
200 /* Match a fingerprint ID against a list of OSes */
201 int
202 pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os)
203 {
204 	struct pf_osfp_entry *entry;
205 	int os_class, os_version, os_subtype;
206 	int en_class, en_version, en_subtype;
207 
208 	if (os == PF_OSFP_ANY)
209 		return (1);
210 	if (list == NULL) {
211 		DPFPRINTF("osfp no match against %x\n", os);
212 		return (os == PF_OSFP_UNKNOWN);
213 	}
214 	PF_OSFP_UNPACK(os, os_class, os_version, os_subtype);
215 	SLIST_FOREACH(entry, list, fp_entry) {
216 		PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype);
217 		if ((os_class == PF_OSFP_ANY || en_class == os_class) &&
218 		    (os_version == PF_OSFP_ANY || en_version == os_version) &&
219 		    (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) {
220 			DPFPRINTF("osfp matched %s %s %s  %x==%x\n",
221 			    entry->fp_class_nm, entry->fp_version_nm,
222 			    entry->fp_subtype_nm, os, entry->fp_os);
223 			return (1);
224 		}
225 	}
226 	DPFPRINTF("fingerprint 0x%x didn't match\n", os);
227 	return (0);
228 }
229 
230 /* Initialize the OS fingerprint system */
231 void
232 pf_osfp_initialize(void)
233 {
234 	pool_init(&pf_osfp_entry_pl, sizeof(struct pf_osfp_entry), 0, 0, 0,
235 	    "pfosfpen", NULL);
236 	pool_init(&pf_osfp_pl, sizeof(struct pf_os_fingerprint), 0, 0, 0,
237 	    "pfosfp", NULL);
238 	SLIST_INIT(&pf_osfp_list);
239 }
240 
241 /* Flush the fingerprint list */
242 void
243 pf_osfp_flush(void)
244 {
245 	struct pf_os_fingerprint *fp;
246 	struct pf_osfp_entry *entry;
247 
248 	while ((fp = SLIST_FIRST(&pf_osfp_list))) {
249 		SLIST_REMOVE_HEAD(&pf_osfp_list, fp_next);
250 		while ((entry = SLIST_FIRST(&fp->fp_oses))) {
251 			SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry);
252 			pool_put(&pf_osfp_entry_pl, entry);
253 		}
254 		pool_put(&pf_osfp_pl, fp);
255 	}
256 }
257 
258 
259 /* Add a fingerprint */
260 int
261 pf_osfp_add(struct pf_osfp_ioctl *fpioc)
262 {
263 	struct pf_os_fingerprint *fp, fpadd;
264 	struct pf_osfp_entry *entry;
265 
266 	memset(&fpadd, 0, sizeof(fpadd));
267 	fpadd.fp_tcpopts = fpioc->fp_tcpopts;
268 	fpadd.fp_wsize = fpioc->fp_wsize;
269 	fpadd.fp_psize = fpioc->fp_psize;
270 	fpadd.fp_mss = fpioc->fp_mss;
271 	fpadd.fp_flags = fpioc->fp_flags;
272 	fpadd.fp_optcnt = fpioc->fp_optcnt;
273 	fpadd.fp_wscale = fpioc->fp_wscale;
274 	fpadd.fp_ttl = fpioc->fp_ttl;
275 
276 	DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d "
277 	    "(TS=%s,M=%s%d,W=%s%d) %x\n",
278 	    fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm,
279 	    fpioc->fp_os.fp_subtype_nm,
280 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" :
281 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" :
282 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" :
283 	    (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "",
284 	    fpadd.fp_wsize,
285 	    fpadd.fp_ttl,
286 	    (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0,
287 	    (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" :
288 	    (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "",
289 	    fpadd.fp_psize,
290 	    (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt,
291 	    (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "",
292 	    (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
293 	    (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
294 	    fpadd.fp_mss,
295 	    (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
296 	    (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
297 	    fpadd.fp_wscale,
298 	    fpioc->fp_os.fp_os);
299 
300 
301 	if ((fp = pf_osfp_find_exact(&pf_osfp_list, &fpadd))) {
302 		 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
303 			if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os))
304 				return (EEXIST);
305 		}
306 		if ((entry = pool_get(&pf_osfp_entry_pl, PR_NOWAIT)) == NULL)
307 			return (ENOMEM);
308 	} else {
309 		if ((fp = pool_get(&pf_osfp_pl, PR_NOWAIT)) == NULL)
310 			return (ENOMEM);
311 		memset(fp, 0, sizeof(*fp));
312 		fp->fp_tcpopts = fpioc->fp_tcpopts;
313 		fp->fp_wsize = fpioc->fp_wsize;
314 		fp->fp_psize = fpioc->fp_psize;
315 		fp->fp_mss = fpioc->fp_mss;
316 		fp->fp_flags = fpioc->fp_flags;
317 		fp->fp_optcnt = fpioc->fp_optcnt;
318 		fp->fp_wscale = fpioc->fp_wscale;
319 		fp->fp_ttl = fpioc->fp_ttl;
320 		SLIST_INIT(&fp->fp_oses);
321 		if ((entry = pool_get(&pf_osfp_entry_pl, PR_NOWAIT)) == NULL) {
322 			pool_put(&pf_osfp_pl, fp);
323 			return (ENOMEM);
324 		}
325 		pf_osfp_insert(&pf_osfp_list, fp);
326 	}
327 	memcpy(entry, &fpioc->fp_os, sizeof(*entry));
328 
329 	/* Make sure the strings are NUL terminated */
330 	entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0';
331 	entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0';
332 	entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0';
333 
334 	SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry);
335 
336 #ifdef PFDEBUG
337 	if ((fp = pf_osfp_validate()))
338 		printf("Invalid fingerprint list\n");
339 #endif /* PFDEBUG */
340 	return (0);
341 }
342 
343 
344 /* Find a fingerprint in the list */
345 struct pf_os_fingerprint *
346 pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find,
347     u_int8_t ttldiff)
348 {
349 	struct pf_os_fingerprint *f;
350 
351 #define MATCH_INT(_MOD, _DC, _field)					\
352 	if ((f->fp_flags & _DC) == 0) {					\
353 		if ((f->fp_flags & _MOD) == 0) {			\
354 			if (f->_field != find->_field)			\
355 				continue;				\
356 		} else {						\
357 			if (f->_field == 0 || find->_field % f->_field)	\
358 				continue;				\
359 		}							\
360 	}
361 
362 	SLIST_FOREACH(f, list, fp_next) {
363 		if (f->fp_tcpopts != find->fp_tcpopts ||
364 		    f->fp_optcnt != find->fp_optcnt ||
365 		    f->fp_ttl < find->fp_ttl ||
366 		    f->fp_ttl - find->fp_ttl > ttldiff ||
367 		    (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) !=
368 		    (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)))
369 			continue;
370 
371 		MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize)
372 		MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss)
373 		MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale)
374 		if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) {
375 			if (f->fp_flags & PF_OSFP_WSIZE_MSS) {
376 				if (find->fp_mss == 0)
377 					continue;
378 
379 /* Some "smart" NAT devices and DSL routers will tweak the MSS size and
380  * will set it to whatever is suitable for the link type.
381  */
382 #define SMART_MSS	1460
383 				if ((find->fp_wsize % find->fp_mss ||
384 				    find->fp_wsize / find->fp_mss !=
385 				    f->fp_wsize) &&
386 				    (find->fp_wsize % SMART_MSS ||
387 				    find->fp_wsize / SMART_MSS !=
388 				    f->fp_wsize))
389 					continue;
390 			} else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
391 				if (find->fp_mss == 0)
392 					continue;
393 
394 #define MTUOFF	(sizeof(struct ip) + sizeof(struct tcphdr))
395 #define SMART_MTU	(SMART_MSS + MTUOFF)
396 				if ((find->fp_wsize % (find->fp_mss + MTUOFF) ||
397 				    find->fp_wsize / (find->fp_mss + MTUOFF) !=
398 				    f->fp_wsize) &&
399 				    (find->fp_wsize % SMART_MTU ||
400 				    find->fp_wsize / SMART_MTU !=
401 				    f->fp_wsize))
402 					continue;
403 			} else if (f->fp_flags & PF_OSFP_WSIZE_MOD) {
404 				if (f->fp_wsize == 0 || find->fp_wsize %
405 				    f->fp_wsize)
406 					continue;
407 			} else {
408 				if (f->fp_wsize != find->fp_wsize)
409 					continue;
410 			}
411 		}
412 		return (f);
413 	}
414 
415 	return (NULL);
416 }
417 
418 /* Find an exact fingerprint in the list */
419 struct pf_os_fingerprint *
420 pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find)
421 {
422 	struct pf_os_fingerprint *f;
423 
424 	SLIST_FOREACH(f, list, fp_next) {
425 		if (f->fp_tcpopts == find->fp_tcpopts &&
426 		    f->fp_wsize == find->fp_wsize &&
427 		    f->fp_psize == find->fp_psize &&
428 		    f->fp_mss == find->fp_mss &&
429 		    f->fp_flags == find->fp_flags &&
430 		    f->fp_optcnt == find->fp_optcnt &&
431 		    f->fp_wscale == find->fp_wscale &&
432 		    f->fp_ttl == find->fp_ttl)
433 			return (f);
434 	}
435 
436 	return (NULL);
437 }
438 
439 /* Insert a fingerprint into the list */
440 void
441 pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins)
442 {
443 	struct pf_os_fingerprint *f, *prev = NULL;
444 
445 	/* XXX need to go semi tree based.  can key on tcp options */
446 
447 	SLIST_FOREACH(f, list, fp_next)
448 		prev = f;
449 	if (prev)
450 		SLIST_INSERT_AFTER(prev, ins, fp_next);
451 	else
452 		SLIST_INSERT_HEAD(list, ins, fp_next);
453 }
454 
455 /* Fill a fingerprint by its number (from an ioctl) */
456 int
457 pf_osfp_get(struct pf_osfp_ioctl *fpioc)
458 {
459 	struct pf_os_fingerprint *fp;
460 	struct pf_osfp_entry *entry;
461 	int num = fpioc->fp_getnum;
462 	int i = 0;
463 
464 
465 	memset(fpioc, 0, sizeof(*fpioc));
466 	SLIST_FOREACH(fp, &pf_osfp_list, fp_next) {
467 		SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
468 			if (i++ == num) {
469 				fpioc->fp_mss = fp->fp_mss;
470 				fpioc->fp_wsize = fp->fp_wsize;
471 				fpioc->fp_flags = fp->fp_flags;
472 				fpioc->fp_psize = fp->fp_psize;
473 				fpioc->fp_ttl = fp->fp_ttl;
474 				fpioc->fp_wscale = fp->fp_wscale;
475 				fpioc->fp_getnum = num;
476 				memcpy(&fpioc->fp_os, entry,
477 				    sizeof(fpioc->fp_os));
478 				return (0);
479 			}
480 		}
481 	}
482 
483 	return (EBUSY);
484 }
485 
486 
487 /* Validate that each signature is reachable */
488 struct pf_os_fingerprint *
489 pf_osfp_validate(void)
490 {
491 	struct pf_os_fingerprint *f, *f2, find;
492 
493 	SLIST_FOREACH(f, &pf_osfp_list, fp_next) {
494 		memcpy(&find, f, sizeof(find));
495 
496 		/* We do a few MSS/th_win percolations to make things unique */
497 		if (find.fp_mss == 0)
498 			find.fp_mss = 128;
499 		if (f->fp_flags & PF_OSFP_WSIZE_MSS)
500 			find.fp_wsize *= find.fp_mss, 1;
501 		else if (f->fp_flags & PF_OSFP_WSIZE_MTU)
502 			find.fp_wsize *= (find.fp_mss + 40);
503 		else if (f->fp_flags & PF_OSFP_WSIZE_MOD)
504 			find.fp_wsize *= 2;
505 		if (f != (f2 = pf_osfp_find(&pf_osfp_list, &find, 0))) {
506 			if (f2)
507 				printf("Found \"%s %s %s\" instead of "
508 				    "\"%s %s %s\"\n",
509 				    SLIST_FIRST(&f2->fp_oses)->fp_class_nm,
510 				    SLIST_FIRST(&f2->fp_oses)->fp_version_nm,
511 				    SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm,
512 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
513 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
514 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
515 			else
516 				printf("Couldn't find \"%s %s %s\"\n",
517 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
518 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
519 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
520 			return (f);
521 		}
522 	}
523 	return (NULL);
524 }
525