xref: /freebsd/sys/netpfil/pf/pf_osfp.c (revision 4d846d26) 
1 /*-
2  * SPDX-License-Identifier: ISC
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  *	$OpenBSD: pf_osfp.c,v 1.14 2008/06/12 18:17:01 henning Exp $
19  */
20 
21 #include <sys/cdefs.h>
22 __FBSDID("$FreeBSD$");
23 
24 #include "opt_inet6.h"
25 
26 #include <sys/param.h>
27 #include <sys/kernel.h>
28 #include <sys/lock.h>
29 #include <sys/mbuf.h>
30 #include <sys/socket.h>
31 
32 #include <netinet/in.h>
33 #include <netinet/ip.h>
34 #include <netinet/tcp.h>
35 
36 #include <net/if.h>
37 #include <net/vnet.h>
38 #include <net/pfvar.h>
39 
40 #ifdef INET6
41 #include <netinet/ip6.h>
42 #endif
43 
44 static MALLOC_DEFINE(M_PFOSFP, "pf_osfp", "pf(4) operating system fingerprints");
45 #define	DPFPRINTF(format, x...)		\
46 	if (V_pf_status.debug >= PF_DEBUG_NOISY)	\
47 		printf(format , ##x)
48 
49 SLIST_HEAD(pf_osfp_list, pf_os_fingerprint);
50 VNET_DEFINE_STATIC(struct pf_osfp_list,	pf_osfp_list) =
51 	SLIST_HEAD_INITIALIZER();
52 #define	V_pf_osfp_list			VNET(pf_osfp_list)
53 
54 static struct pf_osfp_enlist	*pf_osfp_fingerprint_hdr(const struct ip *,
55 				    const struct ip6_hdr *,
56 				    const struct tcphdr *);
57 static struct pf_os_fingerprint	*pf_osfp_find(struct pf_osfp_list *,
58 				    struct pf_os_fingerprint *, u_int8_t);
59 static struct pf_os_fingerprint	*pf_osfp_find_exact(struct pf_osfp_list *,
60 				    struct pf_os_fingerprint *);
61 static void			 pf_osfp_insert(struct pf_osfp_list *,
62 				    struct pf_os_fingerprint *);
63 #ifdef PFDEBUG
64 static struct pf_os_fingerprint	*pf_osfp_validate(void);
65 #endif
66 
67 /*
68  * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only)
69  * Returns the list of possible OSes.
70  */
71 struct pf_osfp_enlist *
72 pf_osfp_fingerprint(struct pf_pdesc *pd, struct mbuf *m, int off,
73     const struct tcphdr *tcp)
74 {
75 	struct ip *ip;
76 	struct ip6_hdr *ip6;
77 	char hdr[60];
78 
79 	if ((pd->af != PF_INET && pd->af != PF_INET6) ||
80 	    pd->proto != IPPROTO_TCP || (tcp->th_off << 2) < sizeof(*tcp))
81 		return (NULL);
82 
83 	if (pd->af == PF_INET) {
84 		ip = mtod(m, struct ip *);
85 		ip6 = (struct ip6_hdr *)NULL;
86 	} else {
87 		ip = (struct ip *)NULL;
88 		ip6 = mtod(m, struct ip6_hdr *);
89 	}
90 	if (!pf_pull_hdr(m, off, hdr, tcp->th_off << 2, NULL, NULL,
91 	    pd->af)) return (NULL);
92 
93 	return (pf_osfp_fingerprint_hdr(ip, ip6, (struct tcphdr *)hdr));
94 }
95 
96 static struct pf_osfp_enlist *
97 pf_osfp_fingerprint_hdr(const struct ip *ip, const struct ip6_hdr *ip6, const struct tcphdr *tcp)
98 {
99 	struct pf_os_fingerprint fp, *fpresult;
100 	int cnt, optlen = 0;
101 	const u_int8_t *optp;
102 #ifdef INET6
103 	char srcname[INET6_ADDRSTRLEN];
104 #else
105 	char srcname[INET_ADDRSTRLEN];
106 #endif
107 
108 	if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN)
109 		return (NULL);
110 	if (ip) {
111 		if ((ip->ip_off & htons(IP_OFFMASK)) != 0)
112 			return (NULL);
113 	}
114 
115 	memset(&fp, 0, sizeof(fp));
116 
117 	if (ip) {
118 		fp.fp_psize = ntohs(ip->ip_len);
119 		fp.fp_ttl = ip->ip_ttl;
120 		if (ip->ip_off & htons(IP_DF))
121 			fp.fp_flags |= PF_OSFP_DF;
122 		inet_ntoa_r(ip->ip_src, srcname);
123 	}
124 #ifdef INET6
125 	else if (ip6) {
126 		/* jumbo payload? */
127 		fp.fp_psize = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen);
128 		fp.fp_ttl = ip6->ip6_hlim;
129 		fp.fp_flags |= PF_OSFP_DF;
130 		fp.fp_flags |= PF_OSFP_INET6;
131 		ip6_sprintf(srcname, (const struct in6_addr *)&ip6->ip6_src);
132 	}
133 #endif
134 	else
135 		return (NULL);
136 	fp.fp_wsize = ntohs(tcp->th_win);
137 
138 	cnt = (tcp->th_off << 2) - sizeof(*tcp);
139 	optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp));
140 	for (; cnt > 0; cnt -= optlen, optp += optlen) {
141 		if (*optp == TCPOPT_EOL)
142 			break;
143 
144 		fp.fp_optcnt++;
145 		if (*optp == TCPOPT_NOP) {
146 			fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) |
147 			    PF_OSFP_TCPOPT_NOP;
148 			optlen = 1;
149 		} else {
150 			if (cnt < 2)
151 				return (NULL);
152 			optlen = optp[1];
153 			if (optlen > cnt || optlen < 2)
154 				return (NULL);
155 			switch (*optp) {
156 			case TCPOPT_MAXSEG:
157 				if (optlen >= TCPOLEN_MAXSEG)
158 					memcpy(&fp.fp_mss, &optp[2],
159 					    sizeof(fp.fp_mss));
160 				fp.fp_tcpopts = (fp.fp_tcpopts <<
161 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS;
162 				NTOHS(fp.fp_mss);
163 				break;
164 			case TCPOPT_WINDOW:
165 				if (optlen >= TCPOLEN_WINDOW)
166 					memcpy(&fp.fp_wscale, &optp[2],
167 					    sizeof(fp.fp_wscale));
168 				NTOHS(fp.fp_wscale);
169 				fp.fp_tcpopts = (fp.fp_tcpopts <<
170 				    PF_OSFP_TCPOPT_BITS) |
171 				    PF_OSFP_TCPOPT_WSCALE;
172 				break;
173 			case TCPOPT_SACK_PERMITTED:
174 				fp.fp_tcpopts = (fp.fp_tcpopts <<
175 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK;
176 				break;
177 			case TCPOPT_TIMESTAMP:
178 				if (optlen >= TCPOLEN_TIMESTAMP) {
179 					u_int32_t ts;
180 					memcpy(&ts, &optp[2], sizeof(ts));
181 					if (ts == 0)
182 						fp.fp_flags |= PF_OSFP_TS0;
183 				}
184 				fp.fp_tcpopts = (fp.fp_tcpopts <<
185 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS;
186 				break;
187 			default:
188 				return (NULL);
189 			}
190 		}
191 		optlen = MAX(optlen, 1);	/* paranoia */
192 	}
193 
194 	DPFPRINTF("fingerprinted %s:%d  %d:%d:%d:%d:%llx (%d) "
195 	    "(TS=%s,M=%s%d,W=%s%d)\n",
196 	    srcname, ntohs(tcp->th_sport),
197 	    fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0,
198 	    fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt,
199 	    (fp.fp_flags & PF_OSFP_TS0) ? "0" : "",
200 	    (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
201 	    (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
202 	    fp.fp_mss,
203 	    (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
204 	    (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
205 	    fp.fp_wscale);
206 
207 	if ((fpresult = pf_osfp_find(&V_pf_osfp_list, &fp,
208 	    PF_OSFP_MAXTTL_OFFSET)))
209 		return (&fpresult->fp_oses);
210 	return (NULL);
211 }
212 
213 /* Match a fingerprint ID against a list of OSes */
214 int
215 pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os)
216 {
217 	struct pf_osfp_entry *entry;
218 	int os_class, os_version, os_subtype;
219 	int en_class, en_version, en_subtype;
220 
221 	if (os == PF_OSFP_ANY)
222 		return (1);
223 	if (list == NULL) {
224 		DPFPRINTF("osfp no match against %x\n", os);
225 		return (os == PF_OSFP_UNKNOWN);
226 	}
227 	PF_OSFP_UNPACK(os, os_class, os_version, os_subtype);
228 	SLIST_FOREACH(entry, list, fp_entry) {
229 		PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype);
230 		if ((os_class == PF_OSFP_ANY || en_class == os_class) &&
231 		    (os_version == PF_OSFP_ANY || en_version == os_version) &&
232 		    (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) {
233 			DPFPRINTF("osfp matched %s %s %s  %x==%x\n",
234 			    entry->fp_class_nm, entry->fp_version_nm,
235 			    entry->fp_subtype_nm, os, entry->fp_os);
236 			return (1);
237 		}
238 	}
239 	DPFPRINTF("fingerprint 0x%x didn't match\n", os);
240 	return (0);
241 }
242 
243 /* Flush the fingerprint list */
244 void
245 pf_osfp_flush(void)
246 {
247 	struct pf_os_fingerprint *fp;
248 	struct pf_osfp_entry *entry;
249 
250 	while ((fp = SLIST_FIRST(&V_pf_osfp_list))) {
251 		SLIST_REMOVE_HEAD(&V_pf_osfp_list, fp_next);
252 		while ((entry = SLIST_FIRST(&fp->fp_oses))) {
253 			SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry);
254 			free(entry, M_PFOSFP);
255 		}
256 		free(fp, M_PFOSFP);
257 	}
258 }
259 
260 /* Add a fingerprint */
261 int
262 pf_osfp_add(struct pf_osfp_ioctl *fpioc)
263 {
264 	struct pf_os_fingerprint *fp, fpadd;
265 	struct pf_osfp_entry *entry;
266 
267 	PF_RULES_WASSERT();
268 
269 	memset(&fpadd, 0, sizeof(fpadd));
270 	fpadd.fp_tcpopts = fpioc->fp_tcpopts;
271 	fpadd.fp_wsize = fpioc->fp_wsize;
272 	fpadd.fp_psize = fpioc->fp_psize;
273 	fpadd.fp_mss = fpioc->fp_mss;
274 	fpadd.fp_flags = fpioc->fp_flags;
275 	fpadd.fp_optcnt = fpioc->fp_optcnt;
276 	fpadd.fp_wscale = fpioc->fp_wscale;
277 	fpadd.fp_ttl = fpioc->fp_ttl;
278 
279 #if 0	/* XXX RYAN wants to fix logging */
280 	DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d "
281 	    "(TS=%s,M=%s%d,W=%s%d) %x\n",
282 	    fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm,
283 	    fpioc->fp_os.fp_subtype_nm,
284 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" :
285 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" :
286 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" :
287 	    (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "",
288 	    fpadd.fp_wsize,
289 	    fpadd.fp_ttl,
290 	    (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0,
291 	    (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" :
292 	    (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "",
293 	    fpadd.fp_psize,
294 	    (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt,
295 	    (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "",
296 	    (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
297 	    (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
298 	    fpadd.fp_mss,
299 	    (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
300 	    (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
301 	    fpadd.fp_wscale,
302 	    fpioc->fp_os.fp_os);
303 #endif
304 
305 	if ((fp = pf_osfp_find_exact(&V_pf_osfp_list, &fpadd))) {
306 		 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
307 			if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os))
308 				return (EEXIST);
309 		}
310 		if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT))
311 		    == NULL)
312 			return (ENOMEM);
313 	} else {
314 		if ((fp = malloc(sizeof(*fp), M_PFOSFP, M_ZERO | M_NOWAIT))
315 		    == NULL)
316 			return (ENOMEM);
317 		fp->fp_tcpopts = fpioc->fp_tcpopts;
318 		fp->fp_wsize = fpioc->fp_wsize;
319 		fp->fp_psize = fpioc->fp_psize;
320 		fp->fp_mss = fpioc->fp_mss;
321 		fp->fp_flags = fpioc->fp_flags;
322 		fp->fp_optcnt = fpioc->fp_optcnt;
323 		fp->fp_wscale = fpioc->fp_wscale;
324 		fp->fp_ttl = fpioc->fp_ttl;
325 		SLIST_INIT(&fp->fp_oses);
326 		if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT))
327 		    == NULL) {
328 			free(fp, M_PFOSFP);
329 			return (ENOMEM);
330 		}
331 		pf_osfp_insert(&V_pf_osfp_list, fp);
332 	}
333 	memcpy(entry, &fpioc->fp_os, sizeof(*entry));
334 
335 	/* Make sure the strings are NUL terminated */
336 	entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0';
337 	entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0';
338 	entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0';
339 
340 	SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry);
341 
342 #ifdef PFDEBUG
343 	if ((fp = pf_osfp_validate()))
344 		printf("Invalid fingerprint list\n");
345 #endif /* PFDEBUG */
346 	return (0);
347 }
348 
349 /* Find a fingerprint in the list */
350 static struct pf_os_fingerprint *
351 pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find,
352     u_int8_t ttldiff)
353 {
354 	struct pf_os_fingerprint *f;
355 
356 #define	MATCH_INT(_MOD, _DC, _field)					\
357 	if ((f->fp_flags & _DC) == 0) {					\
358 		if ((f->fp_flags & _MOD) == 0) {			\
359 			if (f->_field != find->_field)			\
360 				continue;				\
361 		} else {						\
362 			if (f->_field == 0 || find->_field % f->_field)	\
363 				continue;				\
364 		}							\
365 	}
366 
367 	SLIST_FOREACH(f, list, fp_next) {
368 		if (f->fp_tcpopts != find->fp_tcpopts ||
369 		    f->fp_optcnt != find->fp_optcnt ||
370 		    f->fp_ttl < find->fp_ttl ||
371 		    f->fp_ttl - find->fp_ttl > ttldiff ||
372 		    (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) !=
373 		    (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)))
374 			continue;
375 
376 		MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize)
377 		MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss)
378 		MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale)
379 		if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) {
380 			if (f->fp_flags & PF_OSFP_WSIZE_MSS) {
381 				if (find->fp_mss == 0)
382 					continue;
383 
384 /*
385  * Some "smart" NAT devices and DSL routers will tweak the MSS size and
386  * will set it to whatever is suitable for the link type.
387  */
388 #define	SMART_MSS	1460
389 				if ((find->fp_wsize % find->fp_mss ||
390 				    find->fp_wsize / find->fp_mss !=
391 				    f->fp_wsize) &&
392 				    (find->fp_wsize % SMART_MSS ||
393 				    find->fp_wsize / SMART_MSS !=
394 				    f->fp_wsize))
395 					continue;
396 			} else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
397 				if (find->fp_mss == 0)
398 					continue;
399 
400 #define	MTUOFF		(sizeof(struct ip) + sizeof(struct tcphdr))
401 #define	SMART_MTU	(SMART_MSS + MTUOFF)
402 				if ((find->fp_wsize % (find->fp_mss + MTUOFF) ||
403 				    find->fp_wsize / (find->fp_mss + MTUOFF) !=
404 				    f->fp_wsize) &&
405 				    (find->fp_wsize % SMART_MTU ||
406 				    find->fp_wsize / SMART_MTU !=
407 				    f->fp_wsize))
408 					continue;
409 			} else if (f->fp_flags & PF_OSFP_WSIZE_MOD) {
410 				if (f->fp_wsize == 0 || find->fp_wsize %
411 				    f->fp_wsize)
412 					continue;
413 			} else {
414 				if (f->fp_wsize != find->fp_wsize)
415 					continue;
416 			}
417 		}
418 		return (f);
419 	}
420 
421 	return (NULL);
422 }
423 
424 /* Find an exact fingerprint in the list */
425 static struct pf_os_fingerprint *
426 pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find)
427 {
428 	struct pf_os_fingerprint *f;
429 
430 	SLIST_FOREACH(f, list, fp_next) {
431 		if (f->fp_tcpopts == find->fp_tcpopts &&
432 		    f->fp_wsize == find->fp_wsize &&
433 		    f->fp_psize == find->fp_psize &&
434 		    f->fp_mss == find->fp_mss &&
435 		    f->fp_flags == find->fp_flags &&
436 		    f->fp_optcnt == find->fp_optcnt &&
437 		    f->fp_wscale == find->fp_wscale &&
438 		    f->fp_ttl == find->fp_ttl)
439 			return (f);
440 	}
441 
442 	return (NULL);
443 }
444 
445 /* Insert a fingerprint into the list */
446 static void
447 pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins)
448 {
449 	struct pf_os_fingerprint *f, *prev = NULL;
450 
451 	/* XXX need to go semi tree based.  can key on tcp options */
452 
453 	SLIST_FOREACH(f, list, fp_next)
454 		prev = f;
455 	if (prev)
456 		SLIST_INSERT_AFTER(prev, ins, fp_next);
457 	else
458 		SLIST_INSERT_HEAD(list, ins, fp_next);
459 }
460 
461 /* Fill a fingerprint by its number (from an ioctl) */
462 int
463 pf_osfp_get(struct pf_osfp_ioctl *fpioc)
464 {
465 	struct pf_os_fingerprint *fp;
466 	struct pf_osfp_entry *entry;
467 	int num = fpioc->fp_getnum;
468 	int i = 0;
469 
470 	memset(fpioc, 0, sizeof(*fpioc));
471 	SLIST_FOREACH(fp, &V_pf_osfp_list, fp_next) {
472 		SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
473 			if (i++ == num) {
474 				fpioc->fp_mss = fp->fp_mss;
475 				fpioc->fp_wsize = fp->fp_wsize;
476 				fpioc->fp_flags = fp->fp_flags;
477 				fpioc->fp_psize = fp->fp_psize;
478 				fpioc->fp_ttl = fp->fp_ttl;
479 				fpioc->fp_wscale = fp->fp_wscale;
480 				fpioc->fp_getnum = num;
481 				memcpy(&fpioc->fp_os, entry,
482 				    sizeof(fpioc->fp_os));
483 				return (0);
484 			}
485 		}
486 	}
487 
488 	return (EBUSY);
489 }
490 
491 #ifdef PFDEBUG
492 /* Validate that each signature is reachable */
493 static struct pf_os_fingerprint *
494 pf_osfp_validate(void)
495 {
496 	struct pf_os_fingerprint *f, *f2, find;
497 
498 	SLIST_FOREACH(f, &V_pf_osfp_list, fp_next) {
499 		memcpy(&find, f, sizeof(find));
500 
501 		/* We do a few MSS/th_win percolations to make things unique */
502 		if (find.fp_mss == 0)
503 			find.fp_mss = 128;
504 		if (f->fp_flags & PF_OSFP_WSIZE_MSS)
505 			find.fp_wsize *= find.fp_mss;
506 		else if (f->fp_flags & PF_OSFP_WSIZE_MTU)
507 			find.fp_wsize *= (find.fp_mss + 40);
508 		else if (f->fp_flags & PF_OSFP_WSIZE_MOD)
509 			find.fp_wsize *= 2;
510 		if (f != (f2 = pf_osfp_find(&V_pf_osfp_list, &find, 0))) {
511 			if (f2)
512 				printf("Found \"%s %s %s\" instead of "
513 				    "\"%s %s %s\"\n",
514 				    SLIST_FIRST(&f2->fp_oses)->fp_class_nm,
515 				    SLIST_FIRST(&f2->fp_oses)->fp_version_nm,
516 				    SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm,
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 			else
521 				printf("Couldn't find \"%s %s %s\"\n",
522 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
523 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
524 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
525 			return (f);
526 		}
527 	}
528 	return (NULL);
529 }
530 #endif /* PFDEBUG */
531