kdumpd.tproj/kdumpd.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 /* Mac OS X kernel core dump server, based on the BSD trivial file
  41  * transfer protocol server (FreeBSD distribution), with several
  42  * modifications. This server is *not* compatible with tftp, as the
  43  * protocol has changed considerably.
  44  */
  45
  46 /*
  47  * Based on the trivial file transfer protocol server.
  48  *
  49  * The original version included many modifications by Jim Guyton
  50  * <guyton@rand-unix>.
  51  */
  52
  53 #include <sys/param.h>
  54 #include <sys/ioctl.h>
  55 #include <sys/stat.h>
  56 #include <sys/socket.h>
  57 #include <sys/types.h>
  58 #include <sys/mman.h>
  59
  60 #include <netinet/in.h>
  61 #include "kdump.h"
  62 #include <arpa/inet.h>
  63
  64 #include <stdint.h>
  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 #include <libkern/OSByteOrder.h>
  78
  79 #include "kdumpsubs.h"
  80
  81 #define TIMEOUT         2
  82
  83 int     peer;
  84 int     rexmtval = TIMEOUT;
  85 int     maxtimeout = 25 * TIMEOUT;
  86
  87 #define PKTSIZE SEGSIZE+6
  88
  89 char    buf[MAXIMUM_KDP_PKTSIZE];
  90 char    ackbuf[MAXIMUM_KDP_PKTSIZE];
  91 struct  sockaddr_in from;
  92 socklen_t fromlen;
  93
  94 void    kdump __P((struct kdumphdr *, int));
  95
  96 /*
  97  * Null-terminated directory prefix list for absolute pathname requests and
  98  * search list for relative pathname requests.
  99  *
 100  * MAXDIRS should be at least as large as the number of arguments that
 101  * inetd allows (currently 20).
 102  */
 103 #define MAXDIRS 20
 104 static struct dirlist {
 105         char    *name;
 106         int     len;
 107 } dirs[MAXDIRS+1];
 108 static int      suppress_naks;
 109 static int      logging = 1;
 110 static int      ipchroot;
 111
 112 static char *errtomsg __P((int));
 113 static void  nak __P((int));
 114 static char * __P(verifyhost(struct sockaddr_in *));
 115 uint32_t kdp_crashdump_pkt_size = (SEGSIZE + (sizeof(struct kdumphdr)));
 116 uint32_t kdp_crashdump_seg_size = SEGSIZE;
 117
 118 #define KDP_FEATURE_MASK_STRING         "features"
 119 enum    {KDP_FEATURE_LARGE_CRASHDUMPS = 1, KDP_FEATURE_LARGE_PKT_SIZE = 2};
 120
 121 uint32_t kdp_crashdump_feature_mask;
 122 uint32_t kdp_feature_large_crashdumps, kdp_feature_large_packets;
 123
 124 int
 125 main(argc, argv)
 126         int argc;
 127         char *argv[];
 128 {
 129         register struct kdumphdr *tp;
 130         register int n;
 131         int ch, on;
 132         struct sockaddr_in sin;
 133         char *chroot_dir = NULL;
 134         struct passwd *nobody;
 135         char *chuser = "nobody";
 136
 137         openlog("kdumpd", LOG_PID | LOG_NDELAY, LOG_FTP);
 138         while ((ch = getopt(argc, argv, "cClns:u:")) != -1) {
 139                 switch (ch) {
 140                 case 'c':
 141                         ipchroot = 1;
 142                         break;
 143                 case 'C':
 144                         ipchroot = 2;
 145                         break;
 146                 case 'l':
 147                         logging = 1;
 148                         break;
 149                 case 'n':
 150                         suppress_naks = 1;
 151                         break;
 152                 case 's':
 153                         chroot_dir = optarg;
 154                         break;
 155                 case 'u':
 156                         chuser = optarg;
 157                         break;
 158                 default:
 159                         syslog(LOG_WARNING, "ignoring unknown option -%c", ch);
 160                 }
 161         }
 162
 163         if (optind < argc) {
 164                 struct dirlist *dirp;
 165
 166                 /* Get list of directory prefixes. Skip relative pathnames. */
 167                 for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS];
 168                      optind++) {
 169                         if (argv[optind][0] == '/') {
 170                                 dirp->name = argv[optind];
 171                                 dirp->len  = strlen(dirp->name);
 172                                 dirp++;
 173                         }
 174                 }
 175         }
 176         else if (chroot_dir) {
 177                 dirs->name = "/";
 178                 dirs->len = 1;
 179         }
 180         if (ipchroot && chroot_dir == NULL) {
 181                 syslog(LOG_ERR, "-c requires -s");
 182                 exit(1);
 183         }
 184
 185         on = 1;
 186         if (ioctl(0, FIONBIO, &on) < 0) {
 187                 syslog(LOG_ERR, "ioctl(FIONBIO): %m");
 188                 exit(1);
 189         }
 190         fromlen = sizeof (from);
 191         n = recvfrom(0, buf, sizeof (buf), 0,
 192             (struct sockaddr *)&from, &fromlen);
 193         if (n < 0) {
 194                 syslog(LOG_ERR, "recvfrom: %m");
 195                 exit(1);
 196         }
 197         /*
 198          * Now that we have read the message out of the UDP
 199          * socket, we fork and exit.  Thus, inetd will go back
 200          * to listening to the kdump port, and the next request
 201          * to come in will start up a new instance of kdumpd.
 202          *
 203          * We do this so that inetd can run kdumpd in "wait" mode.
 204          * The problem with kdumpd running in "nowait" mode is that
 205          * inetd may get one or more successful "selects" on the
 206          * kdump port before we do our receive, so more than one
 207          * instance of kdumpd may be started up.  Worse, if kdumpd
 208          * breaks before doing the above "recvfrom", inetd would
 209          * spawn endless instances, clogging the system.
 210          */
 211         {
 212                 int pid;
 213                 int i;
 214                 socklen_t j;
 215
 216                 for (i = 1; i < 20; i++) {
 217                     pid = fork();
 218                     if (pid < 0) {
 219                                 sleep(i);
 220                                 /*
 221                                  * flush out to most recently sent request.
 222                                  *
 223                                  * This may drop some requests, but those
 224                                  * will be resent by the clients when
 225                                  * they timeout.  The positive effect of
 226                                  * this flush is to (try to) prevent more
 227                                  * than one kdumpd being started up to service
 228                                  * a single request from a single client.
 229                                  */
 230                                 j = sizeof from;
 231                                 i = recvfrom(0, buf, sizeof (buf), 0,
 232                                     (struct sockaddr *)&from, &j);
 233                                 if (i > 0) {
 234                                         n = i;
 235                                         fromlen = j;
 236                                 }
 237                     } else {
 238                                 break;
 239                     }
 240                 }
 241                 if (pid < 0) {
 242                         syslog(LOG_ERR, "fork: %m");
 243                         exit(1);
 244                 } else if (pid != 0) {
 245                         exit(0);
 246                 }
 247         }
 248
 249         /*
 250          * Since we exit here, we should do that only after the above
 251          * recvfrom to keep inetd from constantly forking should there
 252          * be a problem.  See the above comment about system clogging.
 253          */
 254         if (chroot_dir) {
 255                 if (ipchroot) {
 256                         char tempchroot[MAXPATHLEN];
 257                         char *tempaddr;
 258                         struct stat sb;
 259                         int statret;
 260
 261                         tempaddr = inet_ntoa(from.sin_addr);
 262                         snprintf(tempchroot, sizeof(tempchroot), "%s/%s", chroot_dir, tempaddr);
 263                         statret = stat(tempchroot, &sb);
 264                         if ((sb.st_mode & S_IFDIR) &&
 265                             (statret == 0 || (statret == -1 && ipchroot == 1)))
 266                                 chroot_dir = tempchroot;
 267                 }
 268                 /* Must get this before chroot because /etc might go away */
 269                 if ((nobody = getpwnam(chuser)) == NULL) {
 270                         syslog(LOG_ERR, "%s: no such user", chuser);
 271                         exit(1);
 272                 }
 273                 if (chroot(chroot_dir)) {
 274                         syslog(LOG_ERR, "chroot: %s: %m", chroot_dir);
 275                         exit(1);
 276                 }
 277                 chdir( "/" );
 278                 setuid(nobody->pw_uid);
 279         }
 280         else
 281           if (0 !=  chdir(dirs->name))
 282             syslog(LOG_ERR, "chdir%s: %m", dirs->name);
 283
 284         from.sin_family = AF_INET;
 285         alarm(0);
 286         close(0);
 287         close(1);
 288         peer = socket(AF_INET, SOCK_DGRAM, 0);
 289         if (peer < 0) {
 290                 syslog(LOG_ERR, "socket: %m");
 291                 exit(1);
 292         }
 293         memset(&sin, 0, sizeof(sin));
 294         sin.sin_family = AF_INET;
 295         if (bind(peer, (struct sockaddr *)&sin, sizeof (sin)) < 0) {
 296                 syslog(LOG_ERR, "bind: %m");
 297                 exit(1);
 298         }
 299         if (connect(peer, (struct sockaddr *)&from, sizeof(from)) < 0) {
 300                 syslog(LOG_ERR, "connect: %m");
 301                 exit(1);
 302         }
 303         tp = (struct kdumphdr *)buf;
 304         tp->th_opcode = ntohs(tp->th_opcode);
 305         if (tp->th_opcode == WRQ)
 306                 kdump(tp, n);
 307         exit(1);
 308 }
 309
 310 struct formats;
 311 int     validate_access __P((char **, int));
 312
 313 void    recvfile __P((struct formats *));
 314
 315 struct formats {
 316         char    *f_mode;
 317         int     (*f_validate) __P((char **, int));
 318
 319         void    (*f_recv) __P((struct formats *));
 320         int     f_convert;
 321 } formats[] = {
 322   { "netascii", validate_access, recvfile, 1 },
 323   { "octet",    validate_access, recvfile, 0 },
 324   { 0 }
 325 };
 326
 327 /*
 328  * Handle initial connection protocol.
 329  */
 330 void
 331 kdump(tp, size)
 332         struct kdumphdr *tp;
 333         int size;
 334 {
 335         register char *cp;
 336         int first = 1, ecode;
 337         register struct formats *pf;
 338         char *filename, *mode = NULL;
 339
 340         filename = cp = tp->th_stuff;
 341 again:
 342         while (cp < buf + size) {
 343                 if (*cp == '\0')
 344                         break;
 345                 cp++;
 346         }
 347         if (*cp != '\0') {
 348                 nak(EBADOP);
 349                 exit(1);
 350         }
 351         if (first) {
 352                 mode = ++cp;
 353                 first = 0;
 354                 goto again;
 355         }
 356         for (cp = mode; *cp; cp++)
 357                 if (isupper(*cp))
 358                         *cp = tolower(*cp);
 359
 360         cp++;
 361         if (strncmp(KDP_FEATURE_MASK_STRING, cp, sizeof(KDP_FEATURE_MASK_STRING)) == 0) {
 362                 kdp_crashdump_feature_mask = ntohl(*(uint32_t *) (cp + sizeof(KDP_FEATURE_MASK_STRING)));
 363                 kdp_feature_large_crashdumps = kdp_crashdump_feature_mask & KDP_FEATURE_LARGE_CRASHDUMPS;
 364                 kdp_feature_large_packets = kdp_crashdump_feature_mask & KDP_FEATURE_LARGE_PKT_SIZE;
 365
 366                 if (kdp_feature_large_packets) {
 367                         kdp_crashdump_pkt_size = KDP_LARGE_CRASHDUMP_PKT_SIZE;
 368                         kdp_crashdump_seg_size = kdp_crashdump_pkt_size - sizeof(struct kdumphdr);
 369                 }
 370                 syslog(KDUMPD_DEBUG_LEVEL, "Received feature mask %s:0x%x", cp, kdp_crashdump_feature_mask);
 371         } else
 372                 syslog(KDUMPD_DEBUG_LEVEL, "Unable to locate feature mask, mode: %s", mode);
 373
 374         for (pf = formats; pf->f_mode; pf++)
 375                 if (strcmp(pf->f_mode, mode) == 0)
 376                         break;
 377         if (pf->f_mode == 0) {
 378                 nak(EBADOP);
 379                 exit(1);
 380         }
 381         ecode = (*pf->f_validate)(&filename, tp->th_opcode);
 382         if (logging) {
 383                 syslog(KDUMPD_DEBUG_LEVEL, "%s: %s request for %s: %s", verifyhost(&from),
 384                         tp->th_opcode == WRQ ? "write" : "read",
 385                         filename, errtomsg(ecode));
 386         }
 387         if (ecode) {
 388                 /*
 389                  * Avoid storms of naks to a RRQ broadcast for a relative
 390                  * bootfile pathname from a diskless Sun.
 391                  */
 392                 if (suppress_naks && *filename != '/' && ecode == ENOTFOUND)
 393                         exit(0);
 394                 nak(ecode);
 395                 exit(1);
 396         }
 397         if (tp->th_opcode == WRQ)
 398                 (*pf->f_recv)(pf);
 399
 400         exit(0);
 401 }
 402
 403
 404 FILE *file;
 405
 406 /*
 407  * Validate file access. We only allow storage of files that do not already
 408  * exist, and that do not include directory specifiers in their pathnames.
 409  * This is because kernel coredump filenames should always be of the form
 410  * "core-version-IP as dotted quad-random string" as in :
 411  * core-custom-17.202.40.204-a75b4eec
 412  * The file is written to the directory supplied as the first argument
 413  * in inetd.conf
 414  */
 415
 416 int
 417 validate_access(char **filep, int mode)
 418 {
 419   struct stat stbuf;
 420   int   fd;
 421   char *filename = *filep;
 422   static char pathname[MAXPATHLEN];
 423
 424   if (strstr(filename, "/") || strstr(filename, ".."))
 425     return (EACCESS);
 426
 427   snprintf(pathname, sizeof(pathname), "./%s", filename);
 428
 429   if (0 == stat(pathname, &stbuf))
 430     return (EEXIST);
 431
 432   if (errno != ENOENT)
 433     return (errno);
 434
 435
 436   fd = open(filename, O_RDWR|O_CREAT|O_TRUNC , S_IRUSR | S_IWUSR);
 437
 438   if (fd < 0)
 439     return (errno + 100);
 440
 441   file = fdopen(fd, (mode == RRQ)? "r":"w");
 442   if (file == NULL) {
 443     return errno+100;
 444   }
 445   if (fchmod(fd, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP) < 0)
 446     return errno+100;
 447
 448   return (0);
 449 }
 450
 451 int     timeout;
 452 jmp_buf timeoutbuf;
 453
 454 void
 455 timer()
 456 {
 457
 458         timeout += rexmtval;
 459         if (timeout >= maxtimeout)
 460           {
 461             longjmp(timeoutbuf, 2);
 462           }
 463         longjmp(timeoutbuf, 1);
 464 }
 465
 466 void
 467 justquit()
 468 {
 469         exit(0);
 470 }
 471
 472 /*
 473  * Receive a file.
 474  */
 475 void
 476 recvfile(pf)
 477         struct formats *pf;
 478 {
 479         struct kdumphdr *dp, *w_init();
 480         register struct kdumphdr *ap;    /* ack buffer */
 481         register int n, size;
 482         volatile unsigned int block;
 483         volatile unsigned int jmpval = 0;
 484
 485         signal(SIGALRM, timer);
 486         dp = w_init();
 487         ap = (struct kdumphdr *)ackbuf;
 488         block = 0;
 489         do {
 490 send_seek_ack:  timeout = 0;
 491                 if (block == 0)
 492                         ap->th_opcode = htons((u_short)ACK | ((kdp_feature_large_crashdumps | kdp_feature_large_packets)  << 8));
 493                 else
 494                         ap->th_opcode = htons((u_short)ACK);
 495                 ap->th_block = htonl((unsigned int)block);
 496                 block++;
 497                 jmpval = setjmp(timeoutbuf);
 498                 if (2 == jmpval)
 499                   {
 500                     syslog (LOG_ERR, "Timing out and flushing file to disk");
 501                     goto flushfile;
 502                   }
 503 send_ack:
 504                 if (send(peer, ackbuf, 6 , 0) != 6) {
 505                         syslog(LOG_ERR, "write: %m");
 506                         goto abort;
 507                 }
 508                 write_behind(file, pf->f_convert);
 509                 for ( ; ; ) {
 510                         alarm(rexmtval);
 511                         n = recv(peer, dp, kdp_crashdump_pkt_size, 0);
 512                         alarm(0);
 513                         if (n < 0) {            /* really? */
 514                                 syslog(LOG_ERR, "read: %m");
 515                                 goto abort;
 516                         }
 517                         dp->th_opcode = ntohs((u_short)dp->th_opcode);
 518                         dp->th_block = ntohl((unsigned int)dp->th_block);
 519 #if     DEBUG
 520                         syslog(KDUMPD_DEBUG_LEVEL, "Received packet type %u, block %u\n", (unsigned)dp->th_opcode, (unsigned)dp->th_block);
 521 #endif
 522
 523                         if (dp->th_opcode == ERROR)
 524                                 goto abort;
 525
 526                         if (dp->th_opcode == KDP_EOF)
 527                           {
 528                             syslog (LOG_ERR, "Received last panic dump packet");
 529                             goto final_ack;
 530                           }
 531                         if (dp->th_opcode == KDP_SEEK)
 532                           {
 533                             if (dp->th_block == block)
 534                               {
 535                                 off_t crashdump_offset = 0;
 536                                 unsigned int tempoff = 0;
 537
 538                                 if (kdp_feature_large_crashdumps) {
 539                                         crashdump_offset = OSSwapBigToHostInt64((*(uint64_t *)dp->th_data));
 540                                 }
 541                                 else {
 542                                 bcopy (dp->th_data, &tempoff, sizeof(unsigned int));
 543                                 crashdump_offset = ntohl(tempoff);
 544                                 }
 545
 546 #if     DEBUG
 547                                 syslog(KDUMPD_DEBUG_LEVEL, "Seeking to offset 0x%llx\n", crashdump_offset);
 548 #endif
 549                                 errno = 0;
 550                                 lseek(fileno (file), crashdump_offset, SEEK_SET);
 551                                 if (errno)
 552                                   syslog (LOG_ERR, "lseek: %m");
 553
 554                                 goto send_seek_ack;
 555                               }
 556                             (void) synchnet(peer);
 557                             if (dp->th_block == (block-1))
 558                             {
 559                                     syslog (LOG_DAEMON|LOG_ERR, "Retransmitting seek ack - current block %u, received block %u", block, dp->th_block);
 560                                     goto send_ack;          /* rexmit */
 561                             }
 562                         }
 563
 564                         if (dp->th_opcode == DATA) {
 565                                 if (dp->th_block == block) {
 566                                         break;   /* normal */
 567                                 }
 568                                 /* Re-synchronize with the other side */
 569                                 (void) synchnet(peer);
 570                                 if (dp->th_block == (block-1))
 571                                   {
 572                                     syslog (LOG_DAEMON|LOG_ERR, "Retransmitting ack - current block %u, received block %u", block, dp->th_block);
 573                                     goto send_ack;          /* rexmit */
 574                                   }
 575                                 else
 576                                   syslog (LOG_DAEMON|LOG_ERR, "Not retransmitting ack - current block %u, received block %u", block, dp->th_block);
 577                         }
 578                 }
 579 #if DEBUG
 580                 syslog(KDUMPD_DEBUG_LEVEL, "Writing block sized %u, current offset 0x%llx\n", n - 6, ftello(file));
 581 #endif
 582                 size = writeit(file, &dp, n - 6, pf->f_convert);
 583                 if (size != (n-6)) {                    /* ahem */
 584                         if (size < 0) nak(errno + 100);
 585                         else nak(ENOSPACE);
 586                         goto abort;
 587                 }
 588         } while (dp->th_opcode != KDP_EOF);
 589
 590 final_ack:
 591         ap->th_opcode = htons((u_short)ACK);    /* send the "final" ack */
 592         ap->th_block = htonl((unsigned int) (block));
 593         (void) send(peer, ackbuf, 6, 0);
 594 flushfile:
 595         write_behind(file, pf->f_convert);
 596         (void) fclose(file);            /* close data file */
 597         syslog (LOG_ERR, "file closed, sending final ACK\n");
 598
 599         signal(SIGALRM, justquit);      /* just quit on timeout */
 600         alarm(rexmtval);
 601         n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */
 602         alarm(0);
 603         if (n >= 6 &&                   /* if read some data */
 604             dp->th_opcode == DATA &&    /* and got a data block */
 605             block == dp->th_block) {    /* then my last ack was lost */
 606                 (void) send(peer, ackbuf, 6, 0);     /* resend final ack */
 607         }
 608 abort:
 609         return;
 610 }
 611
 612 /* update if needed, when adding new errmsgs */
 613 #define MAXERRMSGLEN    40
 614
 615 struct errmsg {
 616         int     e_code;
 617         char    *e_msg;
 618 } errmsgs[] = {
 619         { EUNDEF,       "Undefined error code" },
 620         { ENOTFOUND,    "File not found" },
 621         { EACCESS,      "Access violation" },
 622         { ENOSPACE,     "Disk full or allocation exceeded" },
 623         { EBADOP,       "Illegal KDUMP operation" },
 624         { EBADID,       "Unknown transfer ID" },
 625         { EEXISTS,      "File already exists" },
 626         { ENOUSER,      "No such user" },
 627         { -1,           0 }
 628 };
 629
 630 static char *
 631 errtomsg(error)
 632         int error;
 633 {
 634         static char buf[20];
 635         register struct errmsg *pe;
 636         if (error == 0)
 637                 return "success";
 638         for (pe = errmsgs; pe->e_code >= 0; pe++)
 639                 if (pe->e_code == error)
 640                         return pe->e_msg;
 641         snprintf(buf, sizeof(buf), "error %d", error);
 642         return buf;
 643 }
 644
 645 /*
 646  * Send a nak packet (error message).
 647  * Error code passed in is one of the
 648  * standard KDUMP codes, or a UNIX errno
 649  * offset by 100.
 650  */
 651 static void
 652 nak(error)
 653         int error;
 654 {
 655         register struct kdumphdr *tp;
 656         int length;
 657         register struct errmsg *pe;
 658
 659         tp = (struct kdumphdr *)buf;
 660         tp->th_opcode = htons((u_short)ERROR);
 661         tp->th_code = htons((unsigned int)error);
 662         for (pe = errmsgs; pe->e_code >= 0; pe++)
 663                 if (pe->e_code == error)
 664                         break;
 665         if (pe->e_code < 0) {
 666                 pe->e_msg = strerror(error - 100);
 667                 tp->th_code = EUNDEF;   /* set 'undef' errorcode */
 668         }
 669         if (strlen(pe->e_msg) > MAXERRMSGLEN) {
 670                 syslog(LOG_ERR, "nak: error msg too long");
 671                 return;
 672         }
 673
 674         strlcpy(tp->th_msg, pe->e_msg, MAXERRMSGLEN);
 675         length = strlen(pe->e_msg);
 676         tp->th_msg[length] = '\0';
 677         length += 5;
 678         if (send(peer, buf, length, 0) != length)
 679                 syslog(LOG_ERR, "nak: %m");
 680
 681         return;
 682 }
 683
 684 static char *
 685 verifyhost(fromp)
 686         struct sockaddr_in *fromp;
 687 {
 688         struct hostent *hp;
 689
 690         hp = gethostbyaddr((char *)&fromp->sin_addr, sizeof(fromp->sin_addr),
 691                 fromp->sin_family);
 692         if(hp)
 693                 return hp->h_name;
 694         else
 695                 return inet_ntoa(fromp->sin_addr);
 696 }