xref: /freebsd/sys/netpfil/pf/pf_osfp.c (revision 4e462178745853ecc014c13f82f89cfe39b83e9c) 
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 
139 	cnt = (tcp->th_off << 2) - sizeof(*tcp);
140 	optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp));
141 	for (; cnt > 0; cnt -= optlen, optp += optlen) {
142 		if (*optp == TCPOPT_EOL)
143 			break;
144 
145 		fp.fp_optcnt++;
146 		if (*optp == TCPOPT_NOP) {
147 			fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) |
148 			    PF_OSFP_TCPOPT_NOP;
149 			optlen = 1;
150 		} else {
151 			if (cnt < 2)
152 				return (NULL);
153 			optlen = optp[1];
154 			if (optlen > cnt || optlen < 2)
155 				return (NULL);
156 			switch (*optp) {
157 			case TCPOPT_MAXSEG:
158 				if (optlen >= TCPOLEN_MAXSEG)
159 					memcpy(&fp.fp_mss, &optp[2],
160 					    sizeof(fp.fp_mss));
161 				fp.fp_tcpopts = (fp.fp_tcpopts <<
162 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS;
163 				NTOHS(fp.fp_mss);
164 				break;
165 			case TCPOPT_WINDOW:
166 				if (optlen >= TCPOLEN_WINDOW)
167 					memcpy(&fp.fp_wscale, &optp[2],
168 					    sizeof(fp.fp_wscale));
169 				NTOHS(fp.fp_wscale);
170 				fp.fp_tcpopts = (fp.fp_tcpopts <<
171 				    PF_OSFP_TCPOPT_BITS) |
172 				    PF_OSFP_TCPOPT_WSCALE;
173 				break;
174 			case TCPOPT_SACK_PERMITTED:
175 				fp.fp_tcpopts = (fp.fp_tcpopts <<
176 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK;
177 				break;
178 			case TCPOPT_TIMESTAMP:
179 				if (optlen >= TCPOLEN_TIMESTAMP) {
180 					u_int32_t ts;
181 					memcpy(&ts, &optp[2], sizeof(ts));
182 					if (ts == 0)
183 						fp.fp_flags |= PF_OSFP_TS0;
184 
185 				}
186 				fp.fp_tcpopts = (fp.fp_tcpopts <<
187 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS;
188 				break;
189 			default:
190 				return (NULL);
191 			}
192 		}
193 		optlen = MAX(optlen, 1);	/* paranoia */
194 	}
195 
196 	DPFPRINTF("fingerprinted %s:%d  %d:%d:%d:%d:%llx (%d) "
197 	    "(TS=%s,M=%s%d,W=%s%d)\n",
198 	    srcname, ntohs(tcp->th_sport),
199 	    fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0,
200 	    fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt,
201 	    (fp.fp_flags & PF_OSFP_TS0) ? "0" : "",
202 	    (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
203 	    (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
204 	    fp.fp_mss,
205 	    (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
206 	    (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
207 	    fp.fp_wscale);
208 
209 	if ((fpresult = pf_osfp_find(&V_pf_osfp_list, &fp,
210 	    PF_OSFP_MAXTTL_OFFSET)))
211 		return (&fpresult->fp_oses);
212 	return (NULL);
213 }
214 
215 /* Match a fingerprint ID against a list of OSes */
216 int
217 pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os)
218 {
219 	struct pf_osfp_entry *entry;
220 	int os_class, os_version, os_subtype;
221 	int en_class, en_version, en_subtype;
222 
223 	if (os == PF_OSFP_ANY)
224 		return (1);
225 	if (list == NULL) {
226 		DPFPRINTF("osfp no match against %x\n", os);
227 		return (os == PF_OSFP_UNKNOWN);
228 	}
229 	PF_OSFP_UNPACK(os, os_class, os_version, os_subtype);
230 	SLIST_FOREACH(entry, list, fp_entry) {
231 		PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype);
232 		if ((os_class == PF_OSFP_ANY || en_class == os_class) &&
233 		    (os_version == PF_OSFP_ANY || en_version == os_version) &&
234 		    (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) {
235 			DPFPRINTF("osfp matched %s %s %s  %x==%x\n",
236 			    entry->fp_class_nm, entry->fp_version_nm,
237 			    entry->fp_subtype_nm, os, entry->fp_os);
238 			return (1);
239 		}
240 	}
241 	DPFPRINTF("fingerprint 0x%x didn't match\n", os);
242 	return (0);
243 }
244 
245 /* Flush the fingerprint list */
246 void
247 pf_osfp_flush(void)
248 {
249 	struct pf_os_fingerprint *fp;
250 	struct pf_osfp_entry *entry;
251 
252 	while ((fp = SLIST_FIRST(&V_pf_osfp_list))) {
253 		SLIST_REMOVE_HEAD(&V_pf_osfp_list, fp_next);
254 		while ((entry = SLIST_FIRST(&fp->fp_oses))) {
255 			SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry);
256 			free(entry, M_PFOSFP);
257 		}
258 		free(fp, M_PFOSFP);
259 	}
260 }
261 
262 
263 /* Add a fingerprint */
264 int
265 pf_osfp_add(struct pf_osfp_ioctl *fpioc)
266 {
267 	struct pf_os_fingerprint *fp, fpadd;
268 	struct pf_osfp_entry *entry;
269 
270 	PF_RULES_WASSERT();
271 
272 	memset(&fpadd, 0, sizeof(fpadd));
273 	fpadd.fp_tcpopts = fpioc->fp_tcpopts;
274 	fpadd.fp_wsize = fpioc->fp_wsize;
275 	fpadd.fp_psize = fpioc->fp_psize;
276 	fpadd.fp_mss = fpioc->fp_mss;
277 	fpadd.fp_flags = fpioc->fp_flags;
278 	fpadd.fp_optcnt = fpioc->fp_optcnt;
279 	fpadd.fp_wscale = fpioc->fp_wscale;
280 	fpadd.fp_ttl = fpioc->fp_ttl;
281 
282 #if 0	/* XXX RYAN wants to fix logging */
283 	DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d "
284 	    "(TS=%s,M=%s%d,W=%s%d) %x\n",
285 	    fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm,
286 	    fpioc->fp_os.fp_subtype_nm,
287 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" :
288 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" :
289 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" :
290 	    (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "",
291 	    fpadd.fp_wsize,
292 	    fpadd.fp_ttl,
293 	    (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0,
294 	    (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" :
295 	    (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "",
296 	    fpadd.fp_psize,
297 	    (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt,
298 	    (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "",
299 	    (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
300 	    (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
301 	    fpadd.fp_mss,
302 	    (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
303 	    (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
304 	    fpadd.fp_wscale,
305 	    fpioc->fp_os.fp_os);
306 #endif
307 
308 	if ((fp = pf_osfp_find_exact(&V_pf_osfp_list, &fpadd))) {
309 		 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
310 			if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os))
311 				return (EEXIST);
312 		}
313 		if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT))
314 		    == NULL)
315 			return (ENOMEM);
316 	} else {
317 		if ((fp = malloc(sizeof(*fp), M_PFOSFP, M_ZERO | M_NOWAIT))
318 		    == NULL)
319 			return (ENOMEM);
320 		fp->fp_tcpopts = fpioc->fp_tcpopts;
321 		fp->fp_wsize = fpioc->fp_wsize;
322 		fp->fp_psize = fpioc->fp_psize;
323 		fp->fp_mss = fpioc->fp_mss;
324 		fp->fp_flags = fpioc->fp_flags;
325 		fp->fp_optcnt = fpioc->fp_optcnt;
326 		fp->fp_wscale = fpioc->fp_wscale;
327 		fp->fp_ttl = fpioc->fp_ttl;
328 		SLIST_INIT(&fp->fp_oses);
329 		if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT))
330 		    == NULL) {
331 			free(fp, M_PFOSFP);
332 			return (ENOMEM);
333 		}
334 		pf_osfp_insert(&V_pf_osfp_list, fp);
335 	}
336 	memcpy(entry, &fpioc->fp_os, sizeof(*entry));
337 
338 	/* Make sure the strings are NUL terminated */
339 	entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0';
340 	entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0';
341 	entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0';
342 
343 	SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry);
344 
345 #ifdef PFDEBUG
346 	if ((fp = pf_osfp_validate()))
347 		printf("Invalid fingerprint list\n");
348 #endif /* PFDEBUG */
349 	return (0);
350 }
351 
352 
353 /* Find a fingerprint in the list */
354 static struct pf_os_fingerprint *
355 pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find,
356     u_int8_t ttldiff)
357 {
358 	struct pf_os_fingerprint *f;
359 
360 #define	MATCH_INT(_MOD, _DC, _field)					\
361 	if ((f->fp_flags & _DC) == 0) {					\
362 		if ((f->fp_flags & _MOD) == 0) {			\
363 			if (f->_field != find->_field)			\
364 				continue;				\
365 		} else {						\
366 			if (f->_field == 0 || find->_field % f->_field)	\
367 				continue;				\
368 		}							\
369 	}
370 
371 	SLIST_FOREACH(f, list, fp_next) {
372 		if (f->fp_tcpopts != find->fp_tcpopts ||
373 		    f->fp_optcnt != find->fp_optcnt ||
374 		    f->fp_ttl < find->fp_ttl ||
375 		    f->fp_ttl - find->fp_ttl > ttldiff ||
376 		    (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) !=
377 		    (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)))
378 			continue;
379 
380 		MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize)
381 		MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss)
382 		MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale)
383 		if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) {
384 			if (f->fp_flags & PF_OSFP_WSIZE_MSS) {
385 				if (find->fp_mss == 0)
386 					continue;
387 
388 /*
389  * Some "smart" NAT devices and DSL routers will tweak the MSS size and
390  * will set it to whatever is suitable for the link type.
391  */
392 #define	SMART_MSS	1460
393 				if ((find->fp_wsize % find->fp_mss ||
394 				    find->fp_wsize / find->fp_mss !=
395 				    f->fp_wsize) &&
396 				    (find->fp_wsize % SMART_MSS ||
397 				    find->fp_wsize / SMART_MSS !=
398 				    f->fp_wsize))
399 					continue;
400 			} else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
401 				if (find->fp_mss == 0)
402 					continue;
403 
404 #define	MTUOFF		(sizeof(struct ip) + sizeof(struct tcphdr))
405 #define	SMART_MTU	(SMART_MSS + MTUOFF)
406 				if ((find->fp_wsize % (find->fp_mss + MTUOFF) ||
407 				    find->fp_wsize / (find->fp_mss + MTUOFF) !=
408 				    f->fp_wsize) &&
409 				    (find->fp_wsize % SMART_MTU ||
410 				    find->fp_wsize / SMART_MTU !=
411 				    f->fp_wsize))
412 					continue;
413 			} else if (f->fp_flags & PF_OSFP_WSIZE_MOD) {
414 				if (f->fp_wsize == 0 || find->fp_wsize %
415 				    f->fp_wsize)
416 					continue;
417 			} else {
418 				if (f->fp_wsize != find->fp_wsize)
419 					continue;
420 			}
421 		}
422 		return (f);
423 	}
424 
425 	return (NULL);
426 }
427 
428 /* Find an exact fingerprint in the list */
429 static struct pf_os_fingerprint *
430 pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find)
431 {
432 	struct pf_os_fingerprint *f;
433 
434 	SLIST_FOREACH(f, list, fp_next) {
435 		if (f->fp_tcpopts == find->fp_tcpopts &&
436 		    f->fp_wsize == find->fp_wsize &&
437 		    f->fp_psize == find->fp_psize &&
438 		    f->fp_mss == find->fp_mss &&
439 		    f->fp_flags == find->fp_flags &&
440 		    f->fp_optcnt == find->fp_optcnt &&
441 		    f->fp_wscale == find->fp_wscale &&
442 		    f->fp_ttl == find->fp_ttl)
443 			return (f);
444 	}
445 
446 	return (NULL);
447 }
448 
449 /* Insert a fingerprint into the list */
450 static void
451 pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins)
452 {
453 	struct pf_os_fingerprint *f, *prev = NULL;
454 
455 	/* XXX need to go semi tree based.  can key on tcp options */
456 
457 	SLIST_FOREACH(f, list, fp_next)
458 		prev = f;
459 	if (prev)
460 		SLIST_INSERT_AFTER(prev, ins, fp_next);
461 	else
462 		SLIST_INSERT_HEAD(list, ins, fp_next);
463 }
464 
465 /* Fill a fingerprint by its number (from an ioctl) */
466 int
467 pf_osfp_get(struct pf_osfp_ioctl *fpioc)
468 {
469 	struct pf_os_fingerprint *fp;
470 	struct pf_osfp_entry *entry;
471 	int num = fpioc->fp_getnum;
472 	int i = 0;
473 
474 
475 	memset(fpioc, 0, sizeof(*fpioc));
476 	SLIST_FOREACH(fp, &V_pf_osfp_list, fp_next) {
477 		SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
478 			if (i++ == num) {
479 				fpioc->fp_mss = fp->fp_mss;
480 				fpioc->fp_wsize = fp->fp_wsize;
481 				fpioc->fp_flags = fp->fp_flags;
482 				fpioc->fp_psize = fp->fp_psize;
483 				fpioc->fp_ttl = fp->fp_ttl;
484 				fpioc->fp_wscale = fp->fp_wscale;
485 				fpioc->fp_getnum = num;
486 				memcpy(&fpioc->fp_os, entry,
487 				    sizeof(fpioc->fp_os));
488 				return (0);
489 			}
490 		}
491 	}
492 
493 	return (EBUSY);
494 }
495 
496 
497 #ifdef PFDEBUG
498 /* Validate that each signature is reachable */
499 static struct pf_os_fingerprint *
500 pf_osfp_validate(void)
501 {
502 	struct pf_os_fingerprint *f, *f2, find;
503 
504 	SLIST_FOREACH(f, &V_pf_osfp_list, fp_next) {
505 		memcpy(&find, f, sizeof(find));
506 
507 		/* We do a few MSS/th_win percolations to make things unique */
508 		if (find.fp_mss == 0)
509 			find.fp_mss = 128;
510 		if (f->fp_flags & PF_OSFP_WSIZE_MSS)
511 			find.fp_wsize *= find.fp_mss;
512 		else if (f->fp_flags & PF_OSFP_WSIZE_MTU)
513 			find.fp_wsize *= (find.fp_mss + 40);
514 		else if (f->fp_flags & PF_OSFP_WSIZE_MOD)
515 			find.fp_wsize *= 2;
516 		if (f != (f2 = pf_osfp_find(&V_pf_osfp_list, &find, 0))) {
517 			if (f2)
518 				printf("Found \"%s %s %s\" instead of "
519 				    "\"%s %s %s\"\n",
520 				    SLIST_FIRST(&f2->fp_oses)->fp_class_nm,
521 				    SLIST_FIRST(&f2->fp_oses)->fp_version_nm,
522 				    SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm,
523 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
524 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
525 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
526 			else
527 				printf("Couldn't find \"%s %s %s\"\n",
528 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
529 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
530 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
531 			return (f);
532 		}
533 	}
534 	return (NULL);
535 }
536 #endif /* PFDEBUG */
537