xref: /freebsd/sys/netpfil/pf/pf_osfp.c (revision 076ad2f8) 
1 /*-
2  * Copyright (c) 2003 Mike Frantzen <frantzen@w4g.org>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  *
16  *	$OpenBSD: pf_osfp.c,v 1.14 2008/06/12 18:17:01 henning Exp $
17  */
18 
19 #include <sys/cdefs.h>
20 __FBSDID("$FreeBSD$");
21 
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/rwlock.h>
29 #include <sys/socket.h>
30 
31 #include <netinet/in.h>
32 #include <netinet/ip.h>
33 #include <netinet/tcp.h>
34 
35 #include <net/if.h>
36 #include <net/vnet.h>
37 #include <net/pfvar.h>
38 
39 #ifdef INET6
40 #include <netinet/ip6.h>
41 #endif
42 
43 static MALLOC_DEFINE(M_PFOSFP, "pf_osfp", "pf(4) operating system fingerprints");
44 #define	DPFPRINTF(format, x...)		\
45 	if (V_pf_status.debug >= PF_DEBUG_NOISY)	\
46 		printf(format , ##x)
47 
48 SLIST_HEAD(pf_osfp_list, pf_os_fingerprint);
49 static VNET_DEFINE(struct pf_osfp_list,	pf_osfp_list) =
50 	SLIST_HEAD_INITIALIZER();
51 #define	V_pf_osfp_list			VNET(pf_osfp_list)
52 
53 static struct pf_osfp_enlist	*pf_osfp_fingerprint_hdr(const struct ip *,
54 				    const struct ip6_hdr *,
55 				    const struct tcphdr *);
56 static struct pf_os_fingerprint	*pf_osfp_find(struct pf_osfp_list *,
57 				    struct pf_os_fingerprint *, u_int8_t);
58 static struct pf_os_fingerprint	*pf_osfp_find_exact(struct pf_osfp_list *,
59 				    struct pf_os_fingerprint *);
60 static void			 pf_osfp_insert(struct pf_osfp_list *,
61 				    struct pf_os_fingerprint *);
62 #ifdef PFDEBUG
63 static struct pf_os_fingerprint	*pf_osfp_validate(void);
64 #endif
65 
66 /*
67  * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only)
68  * Returns the list of possible OSes.
69  */
70 struct pf_osfp_enlist *
71 pf_osfp_fingerprint(struct pf_pdesc *pd, struct mbuf *m, int off,
72     const struct tcphdr *tcp)
73 {
74 	struct ip *ip;
75 	struct ip6_hdr *ip6;
76 	char hdr[60];
77 
78 	if ((pd->af != PF_INET && pd->af != PF_INET6) ||
79 	    pd->proto != IPPROTO_TCP || (tcp->th_off << 2) < sizeof(*tcp))
80 		return (NULL);
81 
82 	if (pd->af == PF_INET) {
83 		ip = mtod(m, struct ip *);
84 		ip6 = (struct ip6_hdr *)NULL;
85 	} else {
86 		ip = (struct ip *)NULL;
87 		ip6 = mtod(m, struct ip6_hdr *);
88 	}
89 	if (!pf_pull_hdr(m, off, hdr, tcp->th_off << 2, NULL, NULL,
90 	    pd->af)) return (NULL);
91 
92 	return (pf_osfp_fingerprint_hdr(ip, ip6, (struct tcphdr *)hdr));
93 }
94 
95 static struct pf_osfp_enlist *
96 pf_osfp_fingerprint_hdr(const struct ip *ip, const struct ip6_hdr *ip6, const struct tcphdr *tcp)
97 {
98 	struct pf_os_fingerprint fp, *fpresult;
99 	int cnt, optlen = 0;
100 	const u_int8_t *optp;
101 #ifdef INET6
102 	char srcname[INET6_ADDRSTRLEN];
103 #else
104 	char srcname[INET_ADDRSTRLEN];
105 #endif
106 
107 	if ((tcp->th_flags & (TH_SYN|TH_ACK)) != TH_SYN)
108 		return (NULL);
109 	if (ip) {
110 		if ((ip->ip_off & htons(IP_OFFMASK)) != 0)
111 			return (NULL);
112 	}
113 
114 	memset(&fp, 0, sizeof(fp));
115 
116 	if (ip) {
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 		inet_ntoa_r(ip->ip_src, srcname);
122 	}
123 #ifdef INET6
124 	else if (ip6) {
125 		/* jumbo payload? */
126 		fp.fp_psize = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen);
127 		fp.fp_ttl = ip6->ip6_hlim;
128 		fp.fp_flags |= PF_OSFP_DF;
129 		fp.fp_flags |= PF_OSFP_INET6;
130 		ip6_sprintf(srcname, (const struct in6_addr *)&ip6->ip6_src);
131 	}
132 #endif
133 	else
134 		return (NULL);
135 	fp.fp_wsize = ntohs(tcp->th_win);
136 
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 				}
185 				fp.fp_tcpopts = (fp.fp_tcpopts <<
186 				    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS;
187 				break;
188 			default:
189 				return (NULL);
190 			}
191 		}
192 		optlen = MAX(optlen, 1);	/* paranoia */
193 	}
194 
195 	DPFPRINTF("fingerprinted %s:%d  %d:%d:%d:%d:%llx (%d) "
196 	    "(TS=%s,M=%s%d,W=%s%d)\n",
197 	    srcname, ntohs(tcp->th_sport),
198 	    fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0,
199 	    fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt,
200 	    (fp.fp_flags & PF_OSFP_TS0) ? "0" : "",
201 	    (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
202 	    (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
203 	    fp.fp_mss,
204 	    (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
205 	    (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
206 	    fp.fp_wscale);
207 
208 	if ((fpresult = pf_osfp_find(&V_pf_osfp_list, &fp,
209 	    PF_OSFP_MAXTTL_OFFSET)))
210 		return (&fpresult->fp_oses);
211 	return (NULL);
212 }
213 
214 /* Match a fingerprint ID against a list of OSes */
215 int
216 pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os)
217 {
218 	struct pf_osfp_entry *entry;
219 	int os_class, os_version, os_subtype;
220 	int en_class, en_version, en_subtype;
221 
222 	if (os == PF_OSFP_ANY)
223 		return (1);
224 	if (list == NULL) {
225 		DPFPRINTF("osfp no match against %x\n", os);
226 		return (os == PF_OSFP_UNKNOWN);
227 	}
228 	PF_OSFP_UNPACK(os, os_class, os_version, os_subtype);
229 	SLIST_FOREACH(entry, list, fp_entry) {
230 		PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype);
231 		if ((os_class == PF_OSFP_ANY || en_class == os_class) &&
232 		    (os_version == PF_OSFP_ANY || en_version == os_version) &&
233 		    (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) {
234 			DPFPRINTF("osfp matched %s %s %s  %x==%x\n",
235 			    entry->fp_class_nm, entry->fp_version_nm,
236 			    entry->fp_subtype_nm, os, entry->fp_os);
237 			return (1);
238 		}
239 	}
240 	DPFPRINTF("fingerprint 0x%x didn't match\n", os);
241 	return (0);
242 }
243 
244 /* Flush the fingerprint list */
245 void
246 pf_osfp_flush(void)
247 {
248 	struct pf_os_fingerprint *fp;
249 	struct pf_osfp_entry *entry;
250 
251 	while ((fp = SLIST_FIRST(&V_pf_osfp_list))) {
252 		SLIST_REMOVE_HEAD(&V_pf_osfp_list, fp_next);
253 		while ((entry = SLIST_FIRST(&fp->fp_oses))) {
254 			SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry);
255 			free(entry, M_PFOSFP);
256 		}
257 		free(fp, M_PFOSFP);
258 	}
259 }
260 
261 
262 /* Add a fingerprint */
263 int
264 pf_osfp_add(struct pf_osfp_ioctl *fpioc)
265 {
266 	struct pf_os_fingerprint *fp, fpadd;
267 	struct pf_osfp_entry *entry;
268 
269 	PF_RULES_WASSERT();
270 
271 	memset(&fpadd, 0, sizeof(fpadd));
272 	fpadd.fp_tcpopts = fpioc->fp_tcpopts;
273 	fpadd.fp_wsize = fpioc->fp_wsize;
274 	fpadd.fp_psize = fpioc->fp_psize;
275 	fpadd.fp_mss = fpioc->fp_mss;
276 	fpadd.fp_flags = fpioc->fp_flags;
277 	fpadd.fp_optcnt = fpioc->fp_optcnt;
278 	fpadd.fp_wscale = fpioc->fp_wscale;
279 	fpadd.fp_ttl = fpioc->fp_ttl;
280 
281 #if 0	/* XXX RYAN wants to fix logging */
282 	DPFPRINTF("adding osfp %s %s %s = %s%d:%d:%d:%s%d:0x%llx %d "
283 	    "(TS=%s,M=%s%d,W=%s%d) %x\n",
284 	    fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm,
285 	    fpioc->fp_os.fp_subtype_nm,
286 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" :
287 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" :
288 	    (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" :
289 	    (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "",
290 	    fpadd.fp_wsize,
291 	    fpadd.fp_ttl,
292 	    (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0,
293 	    (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" :
294 	    (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "",
295 	    fpadd.fp_psize,
296 	    (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt,
297 	    (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "",
298 	    (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
299 	    (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
300 	    fpadd.fp_mss,
301 	    (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
302 	    (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
303 	    fpadd.fp_wscale,
304 	    fpioc->fp_os.fp_os);
305 #endif
306 
307 	if ((fp = pf_osfp_find_exact(&V_pf_osfp_list, &fpadd))) {
308 		 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
309 			if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os))
310 				return (EEXIST);
311 		}
312 		if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT))
313 		    == NULL)
314 			return (ENOMEM);
315 	} else {
316 		if ((fp = malloc(sizeof(*fp), M_PFOSFP, M_ZERO | M_NOWAIT))
317 		    == NULL)
318 			return (ENOMEM);
319 		fp->fp_tcpopts = fpioc->fp_tcpopts;
320 		fp->fp_wsize = fpioc->fp_wsize;
321 		fp->fp_psize = fpioc->fp_psize;
322 		fp->fp_mss = fpioc->fp_mss;
323 		fp->fp_flags = fpioc->fp_flags;
324 		fp->fp_optcnt = fpioc->fp_optcnt;
325 		fp->fp_wscale = fpioc->fp_wscale;
326 		fp->fp_ttl = fpioc->fp_ttl;
327 		SLIST_INIT(&fp->fp_oses);
328 		if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT))
329 		    == NULL) {
330 			free(fp, M_PFOSFP);
331 			return (ENOMEM);
332 		}
333 		pf_osfp_insert(&V_pf_osfp_list, fp);
334 	}
335 	memcpy(entry, &fpioc->fp_os, sizeof(*entry));
336 
337 	/* Make sure the strings are NUL terminated */
338 	entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0';
339 	entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0';
340 	entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0';
341 
342 	SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry);
343 
344 #ifdef PFDEBUG
345 	if ((fp = pf_osfp_validate()))
346 		printf("Invalid fingerprint list\n");
347 #endif /* PFDEBUG */
348 	return (0);
349 }
350 
351 
352 /* Find a fingerprint in the list */
353 static struct pf_os_fingerprint *
354 pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find,
355     u_int8_t ttldiff)
356 {
357 	struct pf_os_fingerprint *f;
358 
359 #define	MATCH_INT(_MOD, _DC, _field)					\
360 	if ((f->fp_flags & _DC) == 0) {					\
361 		if ((f->fp_flags & _MOD) == 0) {			\
362 			if (f->_field != find->_field)			\
363 				continue;				\
364 		} else {						\
365 			if (f->_field == 0 || find->_field % f->_field)	\
366 				continue;				\
367 		}							\
368 	}
369 
370 	SLIST_FOREACH(f, list, fp_next) {
371 		if (f->fp_tcpopts != find->fp_tcpopts ||
372 		    f->fp_optcnt != find->fp_optcnt ||
373 		    f->fp_ttl < find->fp_ttl ||
374 		    f->fp_ttl - find->fp_ttl > ttldiff ||
375 		    (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) !=
376 		    (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)))
377 			continue;
378 
379 		MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize)
380 		MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss)
381 		MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale)
382 		if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) {
383 			if (f->fp_flags & PF_OSFP_WSIZE_MSS) {
384 				if (find->fp_mss == 0)
385 					continue;
386 
387 /*
388  * Some "smart" NAT devices and DSL routers will tweak the MSS size and
389  * will set it to whatever is suitable for the link type.
390  */
391 #define	SMART_MSS	1460
392 				if ((find->fp_wsize % find->fp_mss ||
393 				    find->fp_wsize / find->fp_mss !=
394 				    f->fp_wsize) &&
395 				    (find->fp_wsize % SMART_MSS ||
396 				    find->fp_wsize / SMART_MSS !=
397 				    f->fp_wsize))
398 					continue;
399 			} else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
400 				if (find->fp_mss == 0)
401 					continue;
402 
403 #define	MTUOFF		(sizeof(struct ip) + sizeof(struct tcphdr))
404 #define	SMART_MTU	(SMART_MSS + MTUOFF)
405 				if ((find->fp_wsize % (find->fp_mss + MTUOFF) ||
406 				    find->fp_wsize / (find->fp_mss + MTUOFF) !=
407 				    f->fp_wsize) &&
408 				    (find->fp_wsize % SMART_MTU ||
409 				    find->fp_wsize / SMART_MTU !=
410 				    f->fp_wsize))
411 					continue;
412 			} else if (f->fp_flags & PF_OSFP_WSIZE_MOD) {
413 				if (f->fp_wsize == 0 || find->fp_wsize %
414 				    f->fp_wsize)
415 					continue;
416 			} else {
417 				if (f->fp_wsize != find->fp_wsize)
418 					continue;
419 			}
420 		}
421 		return (f);
422 	}
423 
424 	return (NULL);
425 }
426 
427 /* Find an exact fingerprint in the list */
428 static struct pf_os_fingerprint *
429 pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find)
430 {
431 	struct pf_os_fingerprint *f;
432 
433 	SLIST_FOREACH(f, list, fp_next) {
434 		if (f->fp_tcpopts == find->fp_tcpopts &&
435 		    f->fp_wsize == find->fp_wsize &&
436 		    f->fp_psize == find->fp_psize &&
437 		    f->fp_mss == find->fp_mss &&
438 		    f->fp_flags == find->fp_flags &&
439 		    f->fp_optcnt == find->fp_optcnt &&
440 		    f->fp_wscale == find->fp_wscale &&
441 		    f->fp_ttl == find->fp_ttl)
442 			return (f);
443 	}
444 
445 	return (NULL);
446 }
447 
448 /* Insert a fingerprint into the list */
449 static void
450 pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins)
451 {
452 	struct pf_os_fingerprint *f, *prev = NULL;
453 
454 	/* XXX need to go semi tree based.  can key on tcp options */
455 
456 	SLIST_FOREACH(f, list, fp_next)
457 		prev = f;
458 	if (prev)
459 		SLIST_INSERT_AFTER(prev, ins, fp_next);
460 	else
461 		SLIST_INSERT_HEAD(list, ins, fp_next);
462 }
463 
464 /* Fill a fingerprint by its number (from an ioctl) */
465 int
466 pf_osfp_get(struct pf_osfp_ioctl *fpioc)
467 {
468 	struct pf_os_fingerprint *fp;
469 	struct pf_osfp_entry *entry;
470 	int num = fpioc->fp_getnum;
471 	int i = 0;
472 
473 
474 	memset(fpioc, 0, sizeof(*fpioc));
475 	SLIST_FOREACH(fp, &V_pf_osfp_list, fp_next) {
476 		SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
477 			if (i++ == num) {
478 				fpioc->fp_mss = fp->fp_mss;
479 				fpioc->fp_wsize = fp->fp_wsize;
480 				fpioc->fp_flags = fp->fp_flags;
481 				fpioc->fp_psize = fp->fp_psize;
482 				fpioc->fp_ttl = fp->fp_ttl;
483 				fpioc->fp_wscale = fp->fp_wscale;
484 				fpioc->fp_getnum = num;
485 				memcpy(&fpioc->fp_os, entry,
486 				    sizeof(fpioc->fp_os));
487 				return (0);
488 			}
489 		}
490 	}
491 
492 	return (EBUSY);
493 }
494 
495 
496 #ifdef PFDEBUG
497 /* Validate that each signature is reachable */
498 static struct pf_os_fingerprint *
499 pf_osfp_validate(void)
500 {
501 	struct pf_os_fingerprint *f, *f2, find;
502 
503 	SLIST_FOREACH(f, &V_pf_osfp_list, fp_next) {
504 		memcpy(&find, f, sizeof(find));
505 
506 		/* We do a few MSS/th_win percolations to make things unique */
507 		if (find.fp_mss == 0)
508 			find.fp_mss = 128;
509 		if (f->fp_flags & PF_OSFP_WSIZE_MSS)
510 			find.fp_wsize *= find.fp_mss;
511 		else if (f->fp_flags & PF_OSFP_WSIZE_MTU)
512 			find.fp_wsize *= (find.fp_mss + 40);
513 		else if (f->fp_flags & PF_OSFP_WSIZE_MOD)
514 			find.fp_wsize *= 2;
515 		if (f != (f2 = pf_osfp_find(&V_pf_osfp_list, &find, 0))) {
516 			if (f2)
517 				printf("Found \"%s %s %s\" instead of "
518 				    "\"%s %s %s\"\n",
519 				    SLIST_FIRST(&f2->fp_oses)->fp_class_nm,
520 				    SLIST_FIRST(&f2->fp_oses)->fp_version_nm,
521 				    SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm,
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 			else
526 				printf("Couldn't find \"%s %s %s\"\n",
527 				    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
528 				    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
529 				    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
530 			return (f);
531 		}
532 	}
533 	return (NULL);
534 }
535 #endif /* PFDEBUG */
536