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 *
pf_osfp_fingerprint(struct pf_pdesc * pd,const struct tcphdr * tcp)70 pf_osfp_fingerprint(struct pf_pdesc *pd, const struct tcphdr *tcp)
71 {
72 struct ip *ip = NULL;
73 struct ip6_hdr *ip6 = NULL;
74 char hdr[60];
75
76 if (pd->proto != IPPROTO_TCP || (tcp->th_off << 2) < sizeof(*tcp))
77 return (NULL);
78
79 switch (pd->af) {
80 case AF_INET:
81 ip = mtod(pd->m, struct ip *);
82 ip6 = (struct ip6_hdr *)NULL;
83 break;
84 case AF_INET6:
85 ip6 = mtod(pd->m, struct ip6_hdr *);
86 break;
87 }
88 if (!pf_pull_hdr(pd->m, pd->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 *
pf_osfp_fingerprint_hdr(const struct ip * ip,const struct ip6_hdr * ip6,const struct tcphdr * tcp)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
pf_osfp_match(struct pf_osfp_enlist * list,pf_osfp_t os)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
pf_osfp_flush(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
pf_osfp_add(struct pf_osfp_ioctl * fpioc)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 *
pf_osfp_find(struct pf_osfp_list * list,struct pf_os_fingerprint * find,u_int8_t ttldiff)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 *
pf_osfp_find_exact(struct pf_osfp_list * list,struct pf_os_fingerprint * find)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
pf_osfp_insert(struct pf_osfp_list * list,struct pf_os_fingerprint * ins)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
pf_osfp_get(struct pf_osfp_ioctl * fpioc)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 *
pf_osfp_validate(void)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