sys/netpfil/pf/pf_osfp.c

   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 */