tftpd.tproj/tftpd.c

   1 /*
   2  * Copyright (c) 1983, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #ifndef lint
  35 static const char copyright[] =
  36 "@(#) Copyright (c) 1983, 1993\n\
  37         The Regents of the University of California.  All rights reserved.\n";
  38 #endif /* not lint */
  39
  40 #ifndef lint
  41 #if 0
  42 static char sccsid[] = "@(#)tftpd.c     8.1 (Berkeley) 6/4/93";
  43 #endif
  44 static const char rcsid[] =
  45   "$FreeBSD: src/libexec/tftpd/tftpd.c,v 1.18 2001/02/02 10:52:58 asmodai Exp $";
  46 #endif /* not lint */
  47
  48 /*
  49  * Trivial file transfer protocol server.
  50  *
  51  * This version includes many modifications by Jim Guyton
  52  * <guyton@rand-unix>.
  53  */
  54
  55 #include <sys/param.h>
  56 #include <sys/ioctl.h>
  57 #include <sys/stat.h>
  58 #include <sys/socket.h>
  59 #include <sys/types.h>
  60
  61 #include <netinet/in.h>
  62 #include <arpa/tftp.h>
  63 #include <arpa/inet.h>
  64
  65 #include <ctype.h>
  66 #include <errno.h>
  67 #include <fcntl.h>
  68 #include <netdb.h>
  69 #include <pwd.h>
  70 #include <setjmp.h>
  71 #include <signal.h>
  72 #include <stdio.h>
  73 #include <stdlib.h>
  74 #include <string.h>
  75 #include <syslog.h>
  76 #include <unistd.h>
  77
  78 #include "tftpsubs.h"
  79
  80 #define TIMEOUT         5
  81
  82 int     peer;
  83 int     rexmtval = TIMEOUT;
  84 int     maxtimeout = 5*TIMEOUT;
  85
  86 #define PKTSIZE SEGSIZE+4
  87 char    buf[PKTSIZE];
  88 char    ackbuf[PKTSIZE];
  89 struct  sockaddr_in from;
  90 int     fromlen;
  91
  92 void    tftp __P((struct tftphdr *, int));
  93
  94 /*
  95  * Null-terminated directory prefix list for absolute pathname requests and
  96  * search list for relative pathname requests.
  97  *
  98  * MAXDIRS should be at least as large as the number of arguments that
  99  * inetd allows (currently 20).
 100  */
 101 #define MAXDIRS 20
 102 static struct dirlist {
 103         char    *name;
 104         int     len;
 105 } dirs[MAXDIRS+1];
 106 static int      suppress_naks;
 107 static int      logging;
 108 static int      ipchroot;
 109
 110 static char *errtomsg __P((int));
 111 static void  nak __P((int));
 112 static char * __P(verifyhost(struct sockaddr_in *));
 113
 114 int
 115 main(argc, argv)
 116         int argc;
 117         char *argv[];
 118 {
 119         register struct tftphdr *tp;
 120         register int n;
 121         int ch, on;
 122         struct sockaddr_in sin;
 123         char *chroot_dir = NULL;
 124         struct passwd *nobody;
 125         char *chuser = "nobody";
 126
 127         openlog("tftpd", LOG_PID | LOG_NDELAY, LOG_FTP);
 128         while ((ch = getopt(argc, argv, "cClns:u:")) != -1) {
 129                 switch (ch) {
 130                 case 'c':
 131                         ipchroot = 1;
 132                         break;
 133                 case 'C':
 134                         ipchroot = 2;
 135                         break;
 136                 case 'l':
 137                         logging = 1;
 138                         break;
 139                 case 'n':
 140                         suppress_naks = 1;
 141                         break;
 142                 case 's':
 143                         chroot_dir = optarg;
 144                         break;
 145                 case 'u':
 146                         chuser = optarg;
 147                         break;
 148                 default:
 149                         syslog(LOG_WARNING, "ignoring unknown option -%c", ch);
 150                 }
 151         }
 152         if (optind < argc) {
 153                 struct dirlist *dirp;
 154
 155                 /* Get list of directory prefixes. Skip relative pathnames. */
 156                 for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS];
 157                      optind++) {
 158                         if (argv[optind][0] == '/') {
 159                                 dirp->name = argv[optind];
 160                                 dirp->len  = strlen(dirp->name);
 161                                 dirp++;
 162                         }
 163                 }
 164         }
 165         else if (chroot_dir) {
 166                 dirs->name = "/";
 167                 dirs->len = 1;
 168         }
 169         if (ipchroot && chroot_dir == NULL) {
 170                 syslog(LOG_ERR, "-c requires -s");
 171                 exit(1);
 172         }
 173
 174         on = 1;
 175         if (ioctl(0, FIONBIO, &on) < 0) {
 176                 syslog(LOG_ERR, "ioctl(FIONBIO): %m");
 177                 exit(1);
 178         }
 179         fromlen = sizeof (from);
 180         n = recvfrom(0, buf, sizeof (buf), 0,
 181             (struct sockaddr *)&from, &fromlen);
 182         if (n < 0) {
 183                 syslog(LOG_ERR, "recvfrom: %m");
 184                 exit(1);
 185         }
 186         /*
 187          * Now that we have read the message out of the UDP
 188          * socket, we fork and exit.  Thus, inetd will go back
 189          * to listening to the tftp port, and the next request
 190          * to come in will start up a new instance of tftpd.
 191          *
 192          * We do this so that inetd can run tftpd in "wait" mode.
 193          * The problem with tftpd running in "nowait" mode is that
 194          * inetd may get one or more successful "selects" on the
 195          * tftp port before we do our receive, so more than one
 196          * instance of tftpd may be started up.  Worse, if tftpd
 197          * break before doing the above "recvfrom", inetd would
 198          * spawn endless instances, clogging the system.
 199          */
 200         {
 201                 int pid;
 202                 int i, j;
 203
 204                 for (i = 1; i < 20; i++) {
 205                     pid = fork();
 206                     if (pid < 0) {
 207                                 sleep(i);
 208                                 /*
 209                                  * flush out to most recently sent request.
 210                                  *
 211                                  * This may drop some request, but those
 212                                  * will be resent by the clients when
 213                                  * they timeout.  The positive effect of
 214                                  * this flush is to (try to) prevent more
 215                                  * than one tftpd being started up to service
 216                                  * a single request from a single client.
 217                                  */
 218                                 j = sizeof from;
 219                                 i = recvfrom(0, buf, sizeof (buf), 0,
 220                                     (struct sockaddr *)&from, &j);
 221                                 if (i > 0) {
 222                                         n = i;
 223                                         fromlen = j;
 224                                 }
 225                     } else {
 226                                 break;
 227                     }
 228                 }
 229                 if (pid < 0) {
 230                         syslog(LOG_ERR, "fork: %m");
 231                         exit(1);
 232                 } else if (pid != 0) {
 233                         exit(0);
 234                 }
 235         }
 236
 237         /*
 238          * Since we exit here, we should do that only after the above
 239          * recvfrom to keep inetd from constantly forking should there
 240          * be a problem.  See the above comment about system clogging.
 241          */
 242         if (chroot_dir) {
 243                 if (ipchroot) {
 244                         char tempchroot[MAXPATHLEN];
 245                         char *tempaddr;
 246                         struct stat sb;
 247                         int statret;
 248
 249                         tempaddr = inet_ntoa(from.sin_addr);
 250                         snprintf(tempchroot, sizeof(tempchroot), "%s/%s", chroot_dir, tempaddr);
 251                         statret = stat(tempchroot, &sb);
 252                         if ((sb.st_mode & S_IFDIR) &&
 253                             (statret == 0 || (statret == -1 && ipchroot == 1)))
 254                                 chroot_dir = tempchroot;
 255                 }
 256                 /* Must get this before chroot because /etc might go away */
 257                 if ((nobody = getpwnam(chuser)) == NULL) {
 258                         syslog(LOG_ERR, "%s: no such user", chuser);
 259                         exit(1);
 260                 }
 261                 if (chroot(chroot_dir)) {
 262                         syslog(LOG_ERR, "chroot: %s: %m", chroot_dir);
 263                         exit(1);
 264                 }
 265                 chdir( "/" );
 266                 setuid(nobody->pw_uid);
 267         }
 268
 269         from.sin_family = AF_INET;
 270         alarm(0);
 271         close(0);
 272         close(1);
 273         peer = socket(AF_INET, SOCK_DGRAM, 0);
 274         if (peer < 0) {
 275                 syslog(LOG_ERR, "socket: %m");
 276                 exit(1);
 277         }
 278         memset(&sin, 0, sizeof(sin));
 279         sin.sin_family = AF_INET;
 280         if (bind(peer, (struct sockaddr *)&sin, sizeof (sin)) < 0) {
 281                 syslog(LOG_ERR, "bind: %m");
 282                 exit(1);
 283         }
 284         if (connect(peer, (struct sockaddr *)&from, sizeof(from)) < 0) {
 285                 syslog(LOG_ERR, "connect: %m");
 286                 exit(1);
 287         }
 288         tp = (struct tftphdr *)buf;
 289         tp->th_opcode = ntohs(tp->th_opcode);
 290         if (tp->th_opcode == RRQ || tp->th_opcode == WRQ)
 291                 tftp(tp, n);
 292         exit(1);
 293 }
 294
 295 struct formats;
 296 int     validate_access __P((char **, int));
 297 void    xmitfile __P((struct formats *));
 298 void    recvfile __P((struct formats *));
 299
 300 struct formats {
 301         char    *f_mode;
 302         int     (*f_validate) __P((char **, int));
 303         void    (*f_send) __P((struct formats *));
 304         void    (*f_recv) __P((struct formats *));
 305         int     f_convert;
 306 } formats[] = {
 307         { "netascii",   validate_access,        xmitfile,       recvfile, 1 },
 308         { "octet",      validate_access,        xmitfile,       recvfile, 0 },
 309 #ifdef notdef
 310         { "mail",       validate_user,          sendmail,       recvmail, 1 },
 311 #endif
 312         { 0 }
 313 };
 314
 315 /*
 316  * Handle initial connection protocol.
 317  */
 318 void
 319 tftp(tp, size)
 320         struct tftphdr *tp;
 321         int size;
 322 {
 323         register char *cp;
 324         int first = 1, ecode;
 325         register struct formats *pf;
 326         char *filename, *mode;
 327
 328         filename = cp = tp->th_stuff;
 329 again:
 330         while (cp < buf + size) {
 331                 if (*cp == '\0')
 332                         break;
 333                 cp++;
 334         }
 335         if (*cp != '\0') {
 336                 nak(EBADOP);
 337                 exit(1);
 338         }
 339         if (first) {
 340                 mode = ++cp;
 341                 first = 0;
 342                 goto again;
 343         }
 344         for (cp = mode; *cp; cp++)
 345                 if (isupper(*cp))
 346                         *cp = tolower(*cp);
 347         for (pf = formats; pf->f_mode; pf++)
 348                 if (strcmp(pf->f_mode, mode) == 0)
 349                         break;
 350         if (pf->f_mode == 0) {
 351                 nak(EBADOP);
 352                 exit(1);
 353         }
 354         ecode = (*pf->f_validate)(&filename, tp->th_opcode);
 355         if (logging) {
 356                 syslog(LOG_INFO, "%s: %s request for %s: %s", verifyhost(&from),
 357                         tp->th_opcode == WRQ ? "write" : "read",
 358                         filename, errtomsg(ecode));
 359         }
 360         if (ecode) {
 361                 /*
 362                  * Avoid storms of naks to a RRQ broadcast for a relative
 363                  * bootfile pathname from a diskless Sun.
 364                  */
 365                 if (suppress_naks && *filename != '/' && ecode == ENOTFOUND)
 366                         exit(0);
 367                 nak(ecode);
 368                 exit(1);
 369         }
 370         if (tp->th_opcode == WRQ)
 371                 (*pf->f_recv)(pf);
 372         else
 373                 (*pf->f_send)(pf);
 374         exit(0);
 375 }
 376
 377
 378 FILE *file;
 379
 380 /*
 381  * Validate file access.  Since we
 382  * have no uid or gid, for now require
 383  * file to exist and be publicly
 384  * readable/writable.
 385  * If we were invoked with arguments
 386  * from inetd then the file must also be
 387  * in one of the given directory prefixes.
 388  * Note also, full path name must be
 389  * given as we have no login directory.
 390  */
 391 int
 392 validate_access(filep, mode)
 393         char **filep;
 394         int mode;
 395 {
 396         struct stat stbuf;
 397         int     fd;
 398         struct dirlist *dirp;
 399         static char pathname[MAXPATHLEN];
 400         char *filename = *filep;
 401
 402         /*
 403          * Prevent tricksters from getting around the directory restrictions
 404          */
 405         if (strstr(filename, "/../"))
 406                 return (EACCESS);
 407
 408         if (*filename == '/') {
 409                 /*
 410                  * Allow the request if it's in one of the approved locations.
 411                  * Special case: check the null prefix ("/") by looking
 412                  * for length = 1 and relying on the arg. processing that
 413                  * it's a /.
 414                  */
 415                 for (dirp = dirs; dirp->name != NULL; dirp++) {
 416                         if (dirp->len == 1 ||
 417                             (!strncmp(filename, dirp->name, dirp->len) &&
 418                              filename[dirp->len] == '/'))
 419                                     break;
 420                 }
 421                 /* If directory list is empty, allow access to any file */
 422                 if (dirp->name == NULL && dirp != dirs)
 423                         return (EACCESS);
 424                 if (stat(filename, &stbuf) < 0)
 425                         return (errno == ENOENT ? ENOTFOUND : EACCESS);
 426                 if ((stbuf.st_mode & S_IFMT) != S_IFREG)
 427                         return (ENOTFOUND);
 428                 if (mode == RRQ) {
 429                         if ((stbuf.st_mode & S_IROTH) == 0)
 430                                 return (EACCESS);
 431                 } else {
 432                         if ((stbuf.st_mode & S_IWOTH) == 0)
 433                                 return (EACCESS);
 434                 }
 435         } else {
 436                 int err;
 437
 438                 /*
 439                  * Relative file name: search the approved locations for it.
 440                  * Don't allow write requests that avoid directory
 441                  * restrictions.
 442                  */
 443
 444                 if (!strncmp(filename, "../", 3))
 445                         return (EACCESS);
 446
 447                 /*
 448                  * If the file exists in one of the directories and isn't
 449                  * readable, continue looking. However, change the error code
 450                  * to give an indication that the file exists.
 451                  */
 452                 err = ENOTFOUND;
 453                 for (dirp = dirs; dirp->name != NULL; dirp++) {
 454                         snprintf(pathname, sizeof(pathname), "%s/%s",
 455                                 dirp->name, filename);
 456                         if (stat(pathname, &stbuf) == 0 &&
 457                             (stbuf.st_mode & S_IFMT) == S_IFREG) {
 458                                 if ((stbuf.st_mode & S_IROTH) != 0) {
 459                                         break;
 460                                 }
 461                                 err = EACCESS;
 462                         }
 463                 }
 464                 if (dirp->name == NULL)
 465                         return (err);
 466                 *filep = filename = pathname;
 467         }
 468         fd = open(filename, mode == RRQ ? O_RDONLY : O_WRONLY|O_TRUNC);
 469         if (fd < 0)
 470                 return (errno + 100);
 471         file = fdopen(fd, (mode == RRQ)? "r":"w");
 472         if (file == NULL) {
 473                 return errno+100;
 474         }
 475         return (0);
 476 }
 477
 478 int     timeout;
 479 jmp_buf timeoutbuf;
 480
 481 void
 482 timer()
 483 {
 484
 485         timeout += rexmtval;
 486         if (timeout >= maxtimeout)
 487                 exit(1);
 488         longjmp(timeoutbuf, 1);
 489 }
 490
 491 /*
 492  * Send the requested file.
 493  */
 494 void
 495 xmitfile(pf)
 496         struct formats *pf;
 497 {
 498         struct tftphdr *dp, *r_init();
 499         register struct tftphdr *ap;    /* ack packet */
 500         register int size, n;
 501         volatile unsigned short block;
 502
 503         signal(SIGALRM, timer);
 504         dp = r_init();
 505         ap = (struct tftphdr *)ackbuf;
 506         block = 1;
 507         do {
 508                 size = readit(file, &dp, pf->f_convert);
 509                 if (size < 0) {
 510                         nak(errno + 100);
 511                         goto abort;
 512                 }
 513                 dp->th_opcode = htons((u_short)DATA);
 514                 dp->th_block = htons((u_short)block);
 515                 timeout = 0;
 516                 (void)setjmp(timeoutbuf);
 517
 518 send_data:
 519                 if (send(peer, dp, size + 4, 0) != size + 4) {
 520                         syslog(LOG_ERR, "write: %m");
 521                         goto abort;
 522                 }
 523                 read_ahead(file, pf->f_convert);
 524                 for ( ; ; ) {
 525                         alarm(rexmtval);        /* read the ack */
 526                         n = recv(peer, ackbuf, sizeof (ackbuf), 0);
 527                         alarm(0);
 528                         if (n < 0) {
 529                                 syslog(LOG_ERR, "read: %m");
 530                                 goto abort;
 531                         }
 532                         ap->th_opcode = ntohs((u_short)ap->th_opcode);
 533                         ap->th_block = ntohs((u_short)ap->th_block);
 534
 535                         if (ap->th_opcode == ERROR)
 536                                 goto abort;
 537
 538                         if (ap->th_opcode == ACK) {
 539                                 if (ap->th_block == block)
 540                                         break;
 541                                 /* Re-synchronize with the other side */
 542                                 (void) synchnet(peer);
 543                                 if (ap->th_block == (block -1))
 544                                         goto send_data;
 545                         }
 546
 547                 }
 548                 block++;
 549         } while (size == SEGSIZE);
 550 abort:
 551         (void) fclose(file);
 552 }
 553
 554 void
 555 justquit()
 556 {
 557         exit(0);
 558 }
 559
 560
 561 /*
 562  * Receive a file.
 563  */
 564 void
 565 recvfile(pf)
 566         struct formats *pf;
 567 {
 568         struct tftphdr *dp, *w_init();
 569         register struct tftphdr *ap;    /* ack buffer */
 570         register int n, size;
 571         volatile unsigned short block;
 572
 573         signal(SIGALRM, timer);
 574         dp = w_init();
 575         ap = (struct tftphdr *)ackbuf;
 576         block = 0;
 577         do {
 578                 timeout = 0;
 579                 ap->th_opcode = htons((u_short)ACK);
 580                 ap->th_block = htons((u_short)block);
 581                 block++;
 582                 (void) setjmp(timeoutbuf);
 583 send_ack:
 584                 if (send(peer, ackbuf, 4, 0) != 4) {
 585                         syslog(LOG_ERR, "write: %m");
 586                         goto abort;
 587                 }
 588                 write_behind(file, pf->f_convert);
 589                 for ( ; ; ) {
 590                         alarm(rexmtval);
 591                         n = recv(peer, dp, PKTSIZE, 0);
 592                         alarm(0);
 593                         if (n < 0) {            /* really? */
 594                                 syslog(LOG_ERR, "read: %m");
 595                                 goto abort;
 596                         }
 597                         dp->th_opcode = ntohs((u_short)dp->th_opcode);
 598                         dp->th_block = ntohs((u_short)dp->th_block);
 599                         if (dp->th_opcode == ERROR)
 600                                 goto abort;
 601                         if (dp->th_opcode == DATA) {
 602                                 if (dp->th_block == block) {
 603                                         break;   /* normal */
 604                                 }
 605                                 /* Re-synchronize with the other side */
 606                                 (void) synchnet(peer);
 607                                 if (dp->th_block == (block-1))
 608                                         goto send_ack;          /* rexmit */
 609                         }
 610                 }
 611                 /*  size = write(file, dp->th_data, n - 4); */
 612                 size = writeit(file, &dp, n - 4, pf->f_convert);
 613                 if (size != (n-4)) {                    /* ahem */
 614                         if (size < 0) nak(errno + 100);
 615                         else nak(ENOSPACE);
 616                         goto abort;
 617                 }
 618         } while (size == SEGSIZE);
 619         write_behind(file, pf->f_convert);
 620         (void) fclose(file);            /* close data file */
 621
 622         ap->th_opcode = htons((u_short)ACK);    /* send the "final" ack */
 623         ap->th_block = htons((u_short)(block));
 624         (void) send(peer, ackbuf, 4, 0);
 625
 626         signal(SIGALRM, justquit);      /* just quit on timeout */
 627         alarm(rexmtval);
 628         n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */
 629         alarm(0);
 630         if (n >= 4 &&                   /* if read some data */
 631             dp->th_opcode == DATA &&    /* and got a data block */
 632             block == dp->th_block) {    /* then my last ack was lost */
 633                 (void) send(peer, ackbuf, 4, 0);     /* resend final ack */
 634         }
 635 abort:
 636         return;
 637 }
 638
 639 struct errmsg {
 640         int     e_code;
 641         char    *e_msg;
 642 } errmsgs[] = {
 643         { EUNDEF,       "Undefined error code" },
 644         { ENOTFOUND,    "File not found" },
 645         { EACCESS,      "Access violation" },
 646         { ENOSPACE,     "Disk full or allocation exceeded" },
 647         { EBADOP,       "Illegal TFTP operation" },
 648         { EBADID,       "Unknown transfer ID" },
 649         { EEXISTS,      "File already exists" },
 650         { ENOUSER,      "No such user" },
 651         { -1,           0 }
 652 };
 653
 654 static char *
 655 errtomsg(error)
 656         int error;
 657 {
 658         static char buf[20];
 659         register struct errmsg *pe;
 660         if (error == 0)
 661                 return "success";
 662         for (pe = errmsgs; pe->e_code >= 0; pe++)
 663                 if (pe->e_code == error)
 664                         return pe->e_msg;
 665         snprintf(buf, sizeof(buf), "error %d", error);
 666         return buf;
 667 }
 668
 669 /*
 670  * Send a nak packet (error message).
 671  * Error code passed in is one of the
 672  * standard TFTP codes, or a UNIX errno
 673  * offset by 100.
 674  */
 675 static void
 676 nak(error)
 677         int error;
 678 {
 679         register struct tftphdr *tp;
 680         int length;
 681         register struct errmsg *pe;
 682
 683         tp = (struct tftphdr *)buf;
 684         tp->th_opcode = htons((u_short)ERROR);
 685         tp->th_code = htons((u_short)error);
 686         for (pe = errmsgs; pe->e_code >= 0; pe++)
 687                 if (pe->e_code == error)
 688                         break;
 689         if (pe->e_code < 0) {
 690                 pe->e_msg = strerror(error - 100);
 691                 tp->th_code = EUNDEF;   /* set 'undef' errorcode */
 692         }
 693         strcpy(tp->th_msg, pe->e_msg);
 694         length = strlen(pe->e_msg);
 695         tp->th_msg[length] = '\0';
 696         length += 5;
 697         if (send(peer, buf, length, 0) != length)
 698                 syslog(LOG_ERR, "nak: %m");
 699 }
 700
 701 static char *
 702 verifyhost(fromp)
 703         struct sockaddr_in *fromp;
 704 {
 705         struct hostent *hp;
 706
 707         hp = gethostbyaddr((char *)&fromp->sin_addr, sizeof(fromp->sin_addr),
 708                 fromp->sin_family);
 709         if(hp)
 710                 return hp->h_name;
 711         else
 712                 return inet_ntoa(fromp->sin_addr);
 713 }