xref: /freebsd/sys/netpfil/pf/pf_osfp.c (revision a03411e84728e9b267056fd31c7d1d9d1dc1b01e) 
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 #include "opt_inet6.h"
23 
24 #include <sys/param.h>
25 #include <sys/kernel.h>
26 #include <sys/lock.h>
27 #include <sys/mbuf.h>
28 #include <sys/socket.h>
29 
30 #include <netinet/in.h>
31 #include <netinet/ip.h>
32 #include <netinet/tcp.h>
33 
34 #include <net/if.h>
35 #include <net/vnet.h>
36 #include <net/pfvar.h>
37 
38 #ifdef INET6
39 #include <netinet/ip6.h>
40 #endif
41 
42 static MALLOC_DEFINE(M_PFOSFP, "pf_osfp", "pf(4) operating system fingerprints");
43 #define	DPFPRINTF(format, x...)		\
44 	if (V_pf_status.debug >= PF_DEBUG_NOISY)	\
45 		printf(format , ##x)
46 
47 SLIST_HEAD(pf_osfp_list, pf_os_fingerprint);
48 VNET_DEFINE_STATIC(struct pf_osfp_list,	pf_osfp_list) =
49 	SLIST_HEAD_INITIALIZER();
50 #define	V_pf_osfp_list			VNET(pf_osfp_list)
51 
52 static struct pf_osfp_enlist	*pf_osfp_fingerprint_hdr(const struct ip *,
53 				    const struct ip6_hdr *,
54 				    const struct tcphdr *);
55 static struct pf_os_fingerprint	*pf_osfp_find(struct pf_osfp_list *,
56 				    struct pf_os_fingerprint *, u_int8_t);
57 static struct pf_os_fingerprint	*pf_osfp_find_exact(struct pf_osfp_list *,
58 				    struct pf_os_fingerprint *);
59 static void			 pf_osfp_insert(struct pf_osfp_list *,
60 				    struct pf_os_fingerprint *);
61 #ifdef PFDEBUG
62 static struct pf_os_fingerprint	*pf_osfp_validate(void);
63 #endif
64 
65 /*
66  * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only)
67  * Returns the list of possible OSes.
68  */
69 struct pf_osfp_enlist *
70 pf_osfp_fingerprint(struct pf_pdesc *pd, struct mbuf *m, int off,
71     const struct tcphdr *tcp)
72 {
73 	struct ip *ip;
74 	struct ip6_hdr *ip6;
75 	char hdr[60];
76 
77 	if ((pd->af != PF_INET && pd->af != PF_INET6) ||
78 	    pd->proto != IPPROTO_TCP || (tcp->th_off << 2) < sizeof(*tcp))
79 		return (NULL);
80 
81 	if (pd->af == PF_INET) {
82 		ip = mtod(m, struct ip *);
83 		ip6 = (struct ip6_hdr *)NULL;
84 	} else {
85 		ip = (struct ip *)NULL;
86 		ip6 = mtod(m, struct ip6_hdr *);
87 	}
88 	if (!pf_pull_hdr(m, off, hdr, tcp->th_off << 2, NULL, NULL,
89 	    pd->af)) return (NULL);
90 
91 	return (pf_osfp_fingerprint_hdr(ip, ip6, (struct tcphdr *)hdr));
92 }
93 
94 static struct pf_osfp_enlist *
95 pf_osfp_fingerprint_hdr(const struct ip *ip, const struct ip6_hdr *ip6, const struct tcphdr *tcp)
96 {
97 	struct pf_os_fingerprint fp, *fpresult;
98 	int cnt, optlen = 0;
99 	const u_int8_t *optp;
100 #ifdef INET6
101 	char srcname[INET6_ADDRSTRLEN];
102 #else
103 	char srcname[INET_ADDRSTRLEN];
104 #endif
105 
106 	if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN)
107 		return (NULL);
108 	if (ip) {
109 		if ((ip->ip_off & htons(IP_OFFMASK)) != 0)
110 			return (NULL);
111 	}
112 
113 	memset(&fp, 0, sizeof(fp));
114 
115 	if (ip) {
116 		fp.fp_psize = ntohs(ip->ip_len);
117 		fp.fp_ttl = ip->ip_ttl;
118 		if (ip->ip_off & htons(IP_DF))
119 			fp.fp_flags |= PF_OSFP_DF;
120 		inet_ntoa_r(ip->ip_src, srcname);
121 	}
122 #ifdef INET6
123 	else if (ip6) {
124 		/* jumbo payload? */
125 		fp.fp_psize = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen);
126 		fp.fp_ttl = ip6->ip6_hlim;
127 		fp.fp_flags |= PF_OSFP_DF;
128 		fp.fp_flags |= PF_OSFP_INET6;
129 		ip6_sprintf(srcname, (const struct in6_addr *)&ip6->ip6_src);
130 	}
131 #endif
132 	else
133 		return (NULL);
134 	fp.fp_wsize = ntohs(tcp->th_win);
135 
136 	cnt = (tcp->th_off << 2) - sizeof(*tcp);
137 	optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp));
138 	for (; cnt > 0; cnt -= optlen, optp += optlen) {
139 		if (*optp == TCPOPT_EOL)
140 			break;
141 
142 		fp.fp_optcnt++;
143 		if (*optp == TCPOPT_NOP) {
144 			fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) |
145 			    PF_OSFP_TCPOPT_NOP;
146 			optlen = 1;
147 		} else {
148 			if (cnt < 2)
149 				return (NULL);
150 			optlen = optp[1];
151 			if (optlen > cnt || optlen < 2)
152 				return (NULL);
153 			switch (*optp) {
154 			case TCPOPT_MAXSEG:
155 				if (optlen >= TCPOLEN_MAXSEG)
156 					memcpy(&fp.fp_mss, &optp[2],
157 					    sizeof(fp.fp_mss));
158 				fp.fp_tcpopts = (fp.fp_tcpopts <<
159 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS;
160 				NTOHS(fp.fp_mss);
161 				break;
162 			case TCPOPT_WINDOW:
163 				if (optlen >= TCPOLEN_WINDOW)
164 					memcpy(&fp.fp_wscale, &optp[2],
165 					    sizeof(fp.fp_wscale));
166 				NTOHS(fp.fp_wscale);
167 				fp.fp_tcpopts = (fp.fp_tcpopts <<
168 				    PF_OSFP_TCPOPT_BITS) |
169 				    PF_OSFP_TCPOPT_WSCALE;
170 				break;
171 			case TCPOPT_SACK_PERMITTED:
172 				fp.fp_tcpopts = (fp.fp_tcpopts <<
173 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK;
174 				break;
175 			case TCPOPT_TIMESTAMP:
176 				if (optlen >= TCPOLEN_TIMESTAMP) {
177 					u_int32_t ts;
178 					memcpy(&ts, &optp[2], sizeof(ts));
179 					if (ts == 0)
180 						fp.fp_flags |= PF_OSFP_TS0;
181 				}
182 				fp.fp_tcpopts = (fp.fp_tcpopts <<
183 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS;
184 				break;
185 			default:
186 				return (NULL);
187 			}
188 		}
189 		optlen = MAX(optlen, 1);	/* paranoia */
190 	}
191 
192 	DPFPRINTF("fingerprinted %s:%d  %d:%d:%d:%d:%llx (%d) "
193 	    "(TS=%s,M=%s%d,W=%s%d)\n",
194 	    srcname, ntohs(tcp->th_sport),
195 	    fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0,
196 	    fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt,
197 	    (fp.fp_flags & PF_OSFP_TS0) ? "0" : "",
198 	    (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
199 	    (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
200 	    fp.fp_mss,
201 	    (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
202 	    (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
203 	    fp.fp_wscale);
204 
205 	if ((fpresult = pf_osfp_find(&V_pf_osfp_list, &fp,
206 	    PF_OSFP_MAXTTL_OFFSET)))
207 		return (&fpresult->fp_oses);
208 	return (NULL);
209 }
210 
211 /* Match a fingerprint ID against a list of OSes */
212 int
213 pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os)
214 {
215 	struct pf_osfp_entry *entry;
216 	int os_class, os_version, os_subtype;
217 	int en_class, en_version, en_subtype;
218 
219 	if (os == PF_OSFP_ANY)
220 		return (1);
221 	if (list == NULL) {
222 		DPFPRINTF("osfp no match against %x\n", os);
223 		return (os == PF_OSFP_UNKNOWN);
224 	}
225 	PF_OSFP_UNPACK(os, os_class, os_version, os_subtype);
226 	SLIST_FOREACH(entry, list, fp_entry) {
227 		PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype);
228 		if ((os_class == PF_OSFP_ANY || en_class == os_class) &&
229 		    (os_version == PF_OSFP_ANY || en_version == os_version) &&
230 		    (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) {
231 			DPFPRINTF("osfp matched %s %s %s  %x==%x\n",
232 			    entry->fp_class_nm, entry->fp_version_nm,
233 			    entry->fp_subtype_nm, os, entry->fp_os);
234 			return (1);
235 		}
236 	}
237 	DPFPRINTF("fingerprint 0x%x didn't match\n", os);
238 	return (0);
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(&V_pf_osfp_list))) {
249 		SLIST_REMOVE_HEAD(&V_pf_osfp_list, fp_next);
250 		while ((entry = SLIST_FIRST(&fp->fp_oses))) {
251 			SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry);
252 			free(entry, M_PFOSFP);
253 		}
254 		free(fp, M_PFOSFP);
255 	}
256 }
257 
258 /* Add a fingerprint */
259 int
260 pf_osfp_add(struct pf_osfp_ioctl *fpioc)
261 {
262 	struct pf_os_fingerprint *fp, fpadd;
263 	struct pf_osfp_entry *entry;
264 
265 	PF_RULES_WASSERT();
266 
267 	memset(&fpadd, 0, sizeof(fpadd));
268 	fpadd.fp_tcpopts = fpioc->fp_tcpopts;
269 	fpadd.fp_wsize = fpioc->fp_wsize;
270 	fpadd.fp_psize = fpioc->fp_psize;
271 	fpadd.fp_mss = fpioc->fp_mss;
272 	fpadd.fp_flags = fpioc->fp_flags;
273 	fpadd.fp_optcnt = fpioc->fp_optcnt;
274 	fpadd.fp_wscale = fpioc->fp_wscale;
275 	fpadd.fp_ttl = fpioc->fp_ttl;
276 
277 #if 0	/* XXX RYAN wants to fix logging */
278 	DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d "
279 	    "(TS=%s,M=%s%d,W=%s%d) %x\n",
280 	    fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm,
281 	    fpioc->fp_os.fp_subtype_nm,
282 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" :
283 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" :
284 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" :
285 	    (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "",
286 	    fpadd.fp_wsize,
287 	    fpadd.fp_ttl,
288 	    (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0,
289 	    (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" :
290 	    (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "",
291 	    fpadd.fp_psize,
292 	    (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt,
293 	    (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "",
294 	    (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
295 	    (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
296 	    fpadd.fp_mss,
297 	    (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
298 	    (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
299 	    fpadd.fp_wscale,
300 	    fpioc->fp_os.fp_os);
301 #endif
302 
303 	if ((fp = pf_osfp_find_exact(&V_pf_osfp_list, &fpadd))) {
304 		 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
305 			if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os))
306 				return (EEXIST);
307 		}
308 		if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT))
309 		    == NULL)
310 			return (ENOMEM);
311 	} else {
312 		if ((fp = malloc(sizeof(*fp), M_PFOSFP, M_ZERO | M_NOWAIT))
313 		    == NULL)
314 			return (ENOMEM);
315 		fp->fp_tcpopts = fpioc->fp_tcpopts;
316 		fp->fp_wsize = fpioc->fp_wsize;
317 		fp->fp_psize = fpioc->fp_psize;
318 		fp->fp_mss = fpioc->fp_mss;
319 		fp->fp_flags = fpioc->fp_flags;
320 		fp->fp_optcnt = fpioc->fp_optcnt;
321 		fp->fp_wscale = fpioc->fp_wscale;
322 		fp->fp_ttl = fpioc->fp_ttl;
323 		SLIST_INIT(&fp->fp_oses);
324 		if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT))
325 		    == NULL) {
326 			free(fp, M_PFOSFP);
327 			return (ENOMEM);
328 		}
329 		pf_osfp_insert(&V_pf_osfp_list, fp);
330 	}
331 	memcpy(entry, &fpioc->fp_os, sizeof(*entry));
332 
333 	/* Make sure the strings are NUL terminated */
334 	entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0';
335 	entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0';
336 	entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0';
337 
338 	SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry);
339 
340 #ifdef PFDEBUG
341 	if ((fp = pf_osfp_validate()))
342 		printf("Invalid fingerprint list\n");
343 #endif /* PFDEBUG */
344 	return (0);
345 }
346 
347 /* Find a fingerprint in the list */
348 static struct pf_os_fingerprint *
349 pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find,
350     u_int8_t ttldiff)
351 {
352 	struct pf_os_fingerprint *f;
353 
354 #define	MATCH_INT(_MOD, _DC, _field)					\
355 	if ((f->fp_flags & _DC) == 0) {					\
356 		if ((f->fp_flags & _MOD) == 0) {			\
357 			if (f->_field != find->_field)			\
358 				continue;				\
359 		} else {						\
360 			if (f->_field == 0 || find->_field % f->_field)	\
361 				continue;				\
362 		}							\
363 	}
364 
365 	SLIST_FOREACH(f, list, fp_next) {
366 		if (f->fp_tcpopts != find->fp_tcpopts ||
367 		    f->fp_optcnt != find->fp_optcnt ||
368 		    f->fp_ttl < find->fp_ttl ||
369 		    f->fp_ttl - find->fp_ttl > ttldiff ||
370 		    (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) !=
371 		    (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)))
372 			continue;
373 
374 		MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize)
375 		MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss)
376 		MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale)
377 		if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) {
378 			if (f->fp_flags & PF_OSFP_WSIZE_MSS) {
379 				if (find->fp_mss == 0)
380 					continue;
381 
382 /*
383  * Some "smart" NAT devices and DSL routers will tweak the MSS size and
384  * will set it to whatever is suitable for the link type.
385  */
386 #define	SMART_MSS	1460
387 				if ((find->fp_wsize % find->fp_mss ||
388 				    find->fp_wsize / find->fp_mss !=
389 				    f->fp_wsize) &&
390 				    (find->fp_wsize % SMART_MSS ||
391 				    find->fp_wsize / SMART_MSS !=
392 				    f->fp_wsize))
393 					continue;
394 			} else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
395 				if (find->fp_mss == 0)
396 					continue;
397 
398 #define	MTUOFF		(sizeof(struct ip) + sizeof(struct tcphdr))
399 #define	SMART_MTU	(SMART_MSS + MTUOFF)
400 				if ((find->fp_wsize % (find->fp_mss + MTUOFF) ||
401 				    find->fp_wsize / (find->fp_mss + MTUOFF) !=
402 				    f->fp_wsize) &&
403 				    (find->fp_wsize % SMART_MTU ||
404 				    find->fp_wsize / SMART_MTU !=
405 				    f->fp_wsize))
406 					continue;
407 			} else if (f->fp_flags & PF_OSFP_WSIZE_MOD) {
408 				if (f->fp_wsize == 0 || find->fp_wsize %
409 				    f->fp_wsize)
410 					continue;
411 			} else {
412 				if (f->fp_wsize != find->fp_wsize)
413 					continue;
414 			}
415 		}
416 		return (f);
417 	}
418 
419 	return (NULL);
420 }
421 
422 /* Find an exact fingerprint in the list */
423 static struct pf_os_fingerprint *
424 pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find)
425 {
426 	struct pf_os_fingerprint *f;
427 
428 	SLIST_FOREACH(f, list, fp_next) {
429 		if (f->fp_tcpopts == find->fp_tcpopts &&
430 		    f->fp_wsize == find->fp_wsize &&
431 		    f->fp_psize == find->fp_psize &&
432 		    f->fp_mss == find->fp_mss &&
433 		    f->fp_flags == find->fp_flags &&
434 		    f->fp_optcnt == find->fp_optcnt &&
435 		    f->fp_wscale == find->fp_wscale &&
436 		    f->fp_ttl == find->fp_ttl)
437 			return (f);
438 	}
439 
440 	return (NULL);
441 }
442 
443 /* Insert a fingerprint into the list */
444 static void
445 pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins)
446 {
447 	struct pf_os_fingerprint *f, *prev = NULL;
448 
449 	/* XXX need to go semi tree based.  can key on tcp options */
450 
451 	SLIST_FOREACH(f, list, fp_next)
452 		prev = f;
453 	if (prev)
454 		SLIST_INSERT_AFTER(prev, ins, fp_next);
455 	else
456 		SLIST_INSERT_HEAD(list, ins, fp_next);
457 }
458 
459 /* Fill a fingerprint by its number (from an ioctl) */
460 int
461 pf_osfp_get(struct pf_osfp_ioctl *fpioc)
462 {
463 	struct pf_os_fingerprint *fp;
464 	struct pf_osfp_entry *entry;
465 	int num = fpioc->fp_getnum;
466 	int i = 0;
467 
468 	memset(fpioc, 0, sizeof(*fpioc));
469 	SLIST_FOREACH(fp, &V_pf_osfp_list, fp_next) {
470 		SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
471 			if (i++ == num) {
472 				fpioc->fp_mss = fp->fp_mss;
473 				fpioc->fp_wsize = fp->fp_wsize;
474 				fpioc->fp_flags = fp->fp_flags;
475 				fpioc->fp_psize = fp->fp_psize;
476 				fpioc->fp_ttl = fp->fp_ttl;
477 				fpioc->fp_wscale = fp->fp_wscale;
478 				fpioc->fp_getnum = num;
479 				memcpy(&fpioc->fp_os, entry,
480 				    sizeof(fpioc->fp_os));
481 				return (0);
482 			}
483 		}
484 	}
485 
486 	return (EBUSY);
487 }
488 
489 #ifdef PFDEBUG
490 /* Validate that each signature is reachable */
491 static struct pf_os_fingerprint *
492 pf_osfp_validate(void)
493 {
494 	struct pf_os_fingerprint *f, *f2, find;
495 
496 	SLIST_FOREACH(f, &V_pf_osfp_list, fp_next) {
497 		memcpy(&find, f, sizeof(find));
498 
499 		/* We do a few MSS/th_win percolations to make things unique */
500 		if (find.fp_mss == 0)
501 			find.fp_mss = 128;
502 		if (f->fp_flags & PF_OSFP_WSIZE_MSS)
503 			find.fp_wsize *= find.fp_mss;
504 		else if (f->fp_flags & PF_OSFP_WSIZE_MTU)
505 			find.fp_wsize *= (find.fp_mss + 40);
506 		else if (f->fp_flags & PF_OSFP_WSIZE_MOD)
507 			find.fp_wsize *= 2;
508 		if (f != (f2 = pf_osfp_find(&V_pf_osfp_list, &find, 0))) {
509 			if (f2)
510 				printf("Found \"%s %s %s\" instead of "
511 				    "\"%s %s %s\"\n",
512 				    SLIST_FIRST(&f2->fp_oses)->fp_class_nm,
513 				    SLIST_FIRST(&f2->fp_oses)->fp_version_nm,
514 				    SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm,
515 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
516 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
517 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
518 			else
519 				printf("Couldn't find \"%s %s %s\"\n",
520 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
521 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
522 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
523 			return (f);
524 		}
525 	}
526 	return (NULL);
527 }
528 #endif /* PFDEBUG */
529