usr/src/boot/lib/libstand/tftp.c

   1 /*      $NetBSD: tftp.c,v 1.4 1997/09/17 16:57:07 drochner Exp $         */
   2
   3 /*
   4  * Copyright (c) 1996
   5  *      Matthias Drochner.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed for the NetBSD Project
  18  *      by Matthias Drochner.
  19  * 4. The name of the author may not be used to endorse or promote products
  20  *    derived from this software without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  27  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  31  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 #include <sys/cdefs.h>
  35 __FBSDID("$FreeBSD$");
  36
  37 /*
  38  * Simple TFTP implementation for libsa.
  39  * Assumes:
  40  *  - socket descriptor (int) at open_file->f_devdata
  41  *  - server host IP in global servip
  42  * Restrictions:
  43  *  - read only
  44  *  - lseek only with SEEK_SET or SEEK_CUR
  45  *  - no big time differences between transfers (<tftp timeout)
  46  */
  47
  48 #include <sys/types.h>
  49 #include <sys/stat.h>
  50 #include <netinet/in.h>
  51 #include <netinet/udp.h>
  52 #include <netinet/in_systm.h>
  53 #include <arpa/tftp.h>
  54
  55 #include <string.h>
  56
  57 #include "stand.h"
  58 #include "net.h"
  59 #include "netif.h"
  60
  61 #include "tftp.h"
  62
  63 struct tftp_handle;
  64
  65 static int      tftp_open(const char *path, struct open_file *f);
  66 static int      tftp_close(struct open_file *f);
  67 static int      tftp_parse_oack(struct tftp_handle *h, char *buf, size_t len);
  68 static int      tftp_read(struct open_file *f, void *buf, size_t size, size_t *resid);
  69 static int      tftp_write(struct open_file *f, void *buf, size_t size, size_t *resid);
  70 static off_t    tftp_seek(struct open_file *f, off_t offset, int where);
  71 static int      tftp_set_blksize(struct tftp_handle *h, const char *str);
  72 static int      tftp_stat(struct open_file *f, struct stat *sb);
  73 static ssize_t sendrecv_tftp(struct tftp_handle *h,
  74     ssize_t (*sproc)(struct iodesc *, void *, size_t),
  75     void *sbuf, size_t ssize,
  76     ssize_t (*rproc)(struct tftp_handle *h, void *, ssize_t, time_t, unsigned short *),
  77     void *rbuf, size_t rsize, unsigned short *rtype);
  78
  79 struct fs_ops tftp_fsops = {
  80         "tftp",
  81         tftp_open,
  82         tftp_close,
  83         tftp_read,
  84         tftp_write,
  85         tftp_seek,
  86         tftp_stat,
  87         null_readdir
  88 };
  89
  90 extern struct in_addr servip;
  91
  92 static int      tftpport = 2000;
  93 static int      is_open = 0;
  94
  95 /*
  96  * The legacy TFTP_BLKSIZE value was SEGSIZE(512).
  97  * TFTP_REQUESTED_BLKSIZE of 1428 is (Ethernet MTU, less the TFTP, UDP and
  98  * IP header lengths).
  99  */
 100 #define TFTP_REQUESTED_BLKSIZE 1428
 101
 102 /*
 103  * Choose a blksize big enough so we can test with Ethernet
 104  * Jumbo frames in the future.
 105  */
 106 #define TFTP_MAX_BLKSIZE 9008
 107
 108 struct tftp_handle {
 109         struct iodesc  *iodesc;
 110         int             currblock;      /* contents of lastdata */
 111         int             islastblock;    /* flag */
 112         int             validsize;
 113         int             off;
 114         char           *path;   /* saved for re-requests */
 115         unsigned int    tftp_blksize;
 116         unsigned long   tftp_tsize;
 117         struct {
 118                 u_char header[HEADER_SIZE];
 119                 struct tftphdr t;
 120                 u_char space[TFTP_MAX_BLKSIZE];
 121         } __packed __aligned(4) lastdata;
 122 };
 123
 124 #define TFTP_MAX_ERRCODE EOPTNEG
 125 static const int tftperrors[TFTP_MAX_ERRCODE + 1] = {
 126         0,                      /* ??? */
 127         ENOENT,
 128         EPERM,
 129         ENOSPC,
 130         EINVAL,                 /* ??? */
 131         EINVAL,                 /* ??? */
 132         EEXIST,
 133         EINVAL,                 /* ??? */
 134         EINVAL,                 /* Option negotiation failed. */
 135 };
 136
 137 static int  tftp_getnextblock(struct tftp_handle *h);
 138
 139 /* send error message back. */
 140 static void
 141 tftp_senderr(struct tftp_handle *h, u_short errcode, const char *msg)
 142 {
 143         struct {
 144                 u_char header[HEADER_SIZE];
 145                 struct tftphdr  t;
 146                 u_char space[63]; /* +1 from t */
 147         } __packed __aligned(4) wbuf;
 148         char           *wtail;
 149         int             len;
 150
 151         len = strlen(msg);
 152         if (len > sizeof(wbuf.space))
 153                 len = sizeof(wbuf.space);
 154
 155         wbuf.t.th_opcode = htons((u_short) ERROR);
 156         wbuf.t.th_code   = htons(errcode);
 157
 158         wtail = wbuf.t.th_msg;
 159         bcopy(msg, wtail, len);
 160         wtail[len] = '\0';
 161         wtail += len + 1;
 162
 163         sendudp(h->iodesc, &wbuf.t, wtail - (char *) &wbuf.t);
 164 }
 165
 166 static void
 167 tftp_sendack(struct tftp_handle *h)
 168 {
 169         struct {
 170                 u_char header[HEADER_SIZE];
 171                 struct tftphdr  t;
 172         } __packed __aligned(4) wbuf;
 173         char           *wtail;
 174
 175         wbuf.t.th_opcode = htons((u_short) ACK);
 176         wtail = (char *) &wbuf.t.th_block;
 177         wbuf.t.th_block = htons((u_short) h->currblock);
 178         wtail += 2;
 179
 180         sendudp(h->iodesc, &wbuf.t, wtail - (char *) &wbuf.t);
 181 }
 182
 183 static ssize_t
 184 recvtftp(struct tftp_handle *h, void *pkt, ssize_t len, time_t tleft,
 185     unsigned short *rtype)
 186 {
 187         struct iodesc *d = h->iodesc;
 188         struct tftphdr *t;
 189
 190         errno = 0;
 191
 192         len = readudp(d, pkt, len, tleft);
 193
 194         if (len < 4)
 195                 return (-1);
 196
 197         t = (struct tftphdr *) pkt;
 198         *rtype = ntohs(t->th_opcode);
 199         switch (ntohs(t->th_opcode)) {
 200         case DATA: {
 201                 int got;
 202
 203                 if (htons(t->th_block) != (u_short) d->xid) {
 204                         /*
 205                          * Expected block?
 206                          */
 207                         return (-1);
 208                 }
 209                 if (d->xid == 1) {
 210                         /*
 211                          * First data packet from new port.
 212                          */
 213                         struct udphdr *uh;
 214                         uh = (struct udphdr *) pkt - 1;
 215                         d->destport = uh->uh_sport;
 216                 } /* else check uh_sport has not changed??? */
 217                 got = len - (t->th_data - (char *) t);
 218                 return got;
 219         }
 220         case ERROR:
 221                 if ((unsigned) ntohs(t->th_code) > TFTP_MAX_ERRCODE) {
 222                         printf("illegal tftp error %d\n", ntohs(t->th_code));
 223                         errno = EIO;
 224                 } else {
 225 #ifdef TFTP_DEBUG
 226                         printf("tftp-error %d\n", ntohs(t->th_code));
 227 #endif
 228                         errno = tftperrors[ntohs(t->th_code)];
 229                 }
 230                 return (-1);
 231         case OACK: {
 232                 struct udphdr *uh;
 233                 int tftp_oack_len;
 234
 235                 /*
 236                  * Unexpected OACK. TFTP transfer already in progress.
 237                  * Drop the pkt.
 238                  */
 239                 if (d->xid != 1) {
 240                         return (-1);
 241                 }
 242
 243                 /*
 244                  * Remember which port this OACK came from, because we need
 245                  * to send the ACK or errors back to it.
 246                  */
 247                 uh = (struct udphdr *) pkt - 1;
 248                 d->destport = uh->uh_sport;
 249
 250                 /* Parse options ACK-ed by the server. */
 251                 tftp_oack_len = len - sizeof(t->th_opcode);
 252                 if (tftp_parse_oack(h, t->th_u.tu_stuff, tftp_oack_len) != 0) {
 253                         tftp_senderr(h, EOPTNEG, "Malformed OACK");
 254                         errno = EIO;
 255                         return (-1);
 256                 }
 257                 return (0);
 258         }
 259         default:
 260 #ifdef TFTP_DEBUG
 261                 printf("tftp type %d not handled\n", ntohs(t->th_opcode));
 262 #endif
 263                 return (-1);
 264         }
 265 }
 266
 267 /* send request, expect first block (or error) */
 268 static int
 269 tftp_makereq(struct tftp_handle *h)
 270 {
 271         struct {
 272                 u_char header[HEADER_SIZE];
 273                 struct tftphdr  t;
 274                 u_char space[FNAME_SIZE + 6];
 275         } __packed __aligned(4) wbuf;
 276         char           *wtail;
 277         int             l;
 278         ssize_t         res;
 279         struct tftphdr *t;
 280         char *tftp_blksize = NULL;
 281         int blksize_l;
 282         unsigned short rtype = 0;
 283
 284         /*
 285          * Allow overriding default TFTP block size by setting
 286          * a tftp.blksize environment variable.
 287          */
 288         if ((tftp_blksize = getenv("tftp.blksize")) != NULL) {
 289                 tftp_set_blksize(h, tftp_blksize);
 290         }
 291
 292         wbuf.t.th_opcode = htons((u_short) RRQ);
 293         wtail = wbuf.t.th_stuff;
 294         l = strlen(h->path);
 295 #ifdef TFTP_PREPEND_PATH
 296         if (l > FNAME_SIZE - (sizeof(TFTP_PREPEND_PATH) - 1))
 297                 return (ENAMETOOLONG);
 298         bcopy(TFTP_PREPEND_PATH, wtail, sizeof(TFTP_PREPEND_PATH) - 1);
 299         wtail += sizeof(TFTP_PREPEND_PATH) - 1;
 300 #else
 301         if (l > FNAME_SIZE)
 302                 return (ENAMETOOLONG);
 303 #endif
 304         bcopy(h->path, wtail, l + 1);
 305         wtail += l + 1;
 306         bcopy("octet", wtail, 6);
 307         wtail += 6;
 308         bcopy("blksize", wtail, 8);
 309         wtail += 8;
 310         blksize_l = sprintf(wtail, "%d", h->tftp_blksize);
 311         wtail += blksize_l + 1;
 312         bcopy("tsize", wtail, 6);
 313         wtail += 6;
 314         bcopy("0", wtail, 2);
 315         wtail += 2;
 316
 317         t = &h->lastdata.t;
 318
 319         /* h->iodesc->myport = htons(--tftpport); */
 320         h->iodesc->myport = htons(tftpport + (getsecs() & 0x3ff));
 321         h->iodesc->destport = htons(IPPORT_TFTP);
 322         h->iodesc->xid = 1;     /* expected block */
 323
 324         h->currblock = 0;
 325         h->islastblock = 0;
 326         h->validsize = 0;
 327
 328         res = sendrecv_tftp(h, &sendudp, &wbuf.t, wtail - (char *) &wbuf.t,
 329                        &recvtftp, t, sizeof(*t) + h->tftp_blksize, &rtype);
 330
 331         if (rtype == OACK)
 332                 return (tftp_getnextblock(h));
 333
 334         /* Server ignored our blksize request, revert to TFTP default. */
 335         h->tftp_blksize = SEGSIZE;
 336
 337         switch (rtype) {
 338                 case DATA: {
 339                         h->currblock = 1;
 340                         h->validsize = res;
 341                         h->islastblock = 0;
 342                         if (res < h->tftp_blksize) {
 343                                 h->islastblock = 1;     /* very short file */
 344                                 tftp_sendack(h);
 345                         }
 346                         return (0);
 347                 }
 348                 case ERROR:
 349                 default:
 350                         return (errno);
 351         }
 352
 353 }
 354
 355 /* ack block, expect next */
 356 static int
 357 tftp_getnextblock(struct tftp_handle *h)
 358 {
 359         struct {
 360                 u_char header[HEADER_SIZE];
 361                 struct tftphdr t;
 362         } __packed __aligned(4) wbuf;
 363         char           *wtail;
 364         int             res;
 365         struct tftphdr *t;
 366         unsigned short rtype = 0;
 367         wbuf.t.th_opcode = htons((u_short) ACK);
 368         wtail = (char *) &wbuf.t.th_block;
 369         wbuf.t.th_block = htons((u_short) h->currblock);
 370         wtail += 2;
 371
 372         t = &h->lastdata.t;
 373
 374         h->iodesc->xid = h->currblock + 1;      /* expected block */
 375
 376         res = sendrecv_tftp(h, &sendudp, &wbuf.t, wtail - (char *) &wbuf.t,
 377                        &recvtftp, t, sizeof(*t) + h->tftp_blksize, &rtype);
 378
 379         if (res == -1)          /* 0 is OK! */
 380                 return (errno);
 381
 382         h->currblock++;
 383         h->validsize = res;
 384         if (res < h->tftp_blksize)
 385                 h->islastblock = 1;     /* EOF */
 386
 387         if (h->islastblock == 1) {
 388                 /* Send an ACK for the last block */
 389                 wbuf.t.th_block = htons((u_short) h->currblock);
 390                 sendudp(h->iodesc, &wbuf.t, wtail - (char *)&wbuf.t);
 391         }
 392
 393         return (0);
 394 }
 395
 396 static int
 397 tftp_open(const char *path, struct open_file *f)
 398 {
 399         struct tftp_handle *tftpfile;
 400         struct iodesc  *io;
 401         int             res;
 402         size_t          pathsize;
 403         const char     *extraslash;
 404
 405         if (netproto != NET_TFTP)
 406                 return (EINVAL);
 407
 408         if (strcmp(f->f_dev->dv_name, "net") != 0) {
 409 #ifdef __i386__
 410                 if (strcmp(f->f_dev->dv_name, "pxe") != 0)
 411                         return (EINVAL);
 412 #else
 413                 return (EINVAL);
 414 #endif
 415         }
 416
 417         if (is_open)
 418                 return (EBUSY);
 419
 420         tftpfile = (struct tftp_handle *) malloc(sizeof(*tftpfile));
 421         if (!tftpfile)
 422                 return (ENOMEM);
 423
 424         memset(tftpfile, 0, sizeof(*tftpfile));
 425         tftpfile->tftp_blksize = TFTP_REQUESTED_BLKSIZE;
 426         tftpfile->iodesc = io = socktodesc(*(int *) (f->f_devdata));
 427         if (io == NULL)
 428                 return (EINVAL);
 429
 430         io->destip = servip;
 431         tftpfile->off = 0;
 432         pathsize = (strlen(rootpath) + 1 + strlen(path) + 1) * sizeof(char);
 433         tftpfile->path = malloc(pathsize);
 434         if (tftpfile->path == NULL) {
 435                 free(tftpfile);
 436                 return(ENOMEM);
 437         }
 438         if (rootpath[strlen(rootpath) - 1] == '/' || path[0] == '/')
 439                 extraslash = "";
 440         else
 441                 extraslash = "/";
 442         res = snprintf(tftpfile->path, pathsize, "%s%s%s",
 443             rootpath, extraslash, path);
 444         if (res < 0 || res > pathsize) {
 445                 free(tftpfile->path);
 446                 free(tftpfile);
 447                 return(ENOMEM);
 448         }
 449
 450         res = tftp_makereq(tftpfile);
 451
 452         if (res) {
 453                 free(tftpfile->path);
 454                 free(tftpfile);
 455                 return (res);
 456         }
 457         f->f_fsdata = (void *) tftpfile;
 458         is_open = 1;
 459         return (0);
 460 }
 461
 462 static int
 463 tftp_read(struct open_file *f, void *addr, size_t size,
 464     size_t *resid /* out */)
 465 {
 466         struct tftp_handle *tftpfile;
 467         tftpfile = (struct tftp_handle *) f->f_fsdata;
 468
 469         while (size > 0) {
 470                 int needblock, count;
 471
 472                 twiddle(32);
 473
 474                 needblock = tftpfile->off / tftpfile->tftp_blksize + 1;
 475
 476                 if (tftpfile->currblock > needblock) {  /* seek backwards */
 477                         tftp_senderr(tftpfile, 0, "No error: read aborted");
 478                         tftp_makereq(tftpfile); /* no error check, it worked
 479                                                  * for open */
 480                 }
 481
 482                 while (tftpfile->currblock < needblock) {
 483                         int res;
 484
 485                         res = tftp_getnextblock(tftpfile);
 486                         if (res) {      /* no answer */
 487 #ifdef TFTP_DEBUG
 488                                 printf("tftp: read error\n");
 489 #endif
 490                                 return (res);
 491                         }
 492                         if (tftpfile->islastblock)
 493                                 break;
 494                 }
 495
 496                 if (tftpfile->currblock == needblock) {
 497                         int offinblock, inbuffer;
 498
 499                         offinblock = tftpfile->off % tftpfile->tftp_blksize;
 500
 501                         inbuffer = tftpfile->validsize - offinblock;
 502                         if (inbuffer < 0) {
 503 #ifdef TFTP_DEBUG
 504                                 printf("tftp: invalid offset %d\n",
 505                                     tftpfile->off);
 506 #endif
 507                                 return (EINVAL);
 508                         }
 509                         count = (size < inbuffer ? size : inbuffer);
 510                         bcopy(tftpfile->lastdata.t.th_data + offinblock,
 511                             addr, count);
 512
 513                         addr = (char *)addr + count;
 514                         tftpfile->off += count;
 515                         size -= count;
 516
 517                         if ((tftpfile->islastblock) && (count == inbuffer))
 518                                 break;  /* EOF */
 519                 } else {
 520 #ifdef TFTP_DEBUG
 521                         printf("tftp: block %d not found\n", needblock);
 522 #endif
 523                         return (EINVAL);
 524                 }
 525
 526         }
 527
 528         if (resid)
 529                 *resid = size;
 530         return (0);
 531 }
 532
 533 static int
 534 tftp_close(struct open_file *f)
 535 {
 536         struct tftp_handle *tftpfile;
 537         tftpfile = (struct tftp_handle *) f->f_fsdata;
 538
 539         /* let it time out ... */
 540
 541         if (tftpfile) {
 542                 free(tftpfile->path);
 543                 free(tftpfile);
 544         }
 545         is_open = 0;
 546         return (0);
 547 }
 548
 549 static int
 550 tftp_write(struct open_file *f __unused, void *start __unused, size_t size __unused,
 551     size_t *resid __unused /* out */)
 552 {
 553         return (EROFS);
 554 }
 555
 556 static int
 557 tftp_stat(struct open_file *f, struct stat *sb)
 558 {
 559         struct tftp_handle *tftpfile;
 560         tftpfile = (struct tftp_handle *) f->f_fsdata;
 561
 562         sb->st_mode = 0444 | S_IFREG;
 563         sb->st_nlink = 1;
 564         sb->st_uid = 0;
 565         sb->st_gid = 0;
 566         sb->st_size = (off_t) tftpfile->tftp_tsize;
 567         return (0);
 568 }
 569
 570 static off_t
 571 tftp_seek(struct open_file *f, off_t offset, int where)
 572 {
 573         struct tftp_handle *tftpfile;
 574         tftpfile = (struct tftp_handle *) f->f_fsdata;
 575
 576         switch (where) {
 577         case SEEK_SET:
 578                 tftpfile->off = offset;
 579                 break;
 580         case SEEK_CUR:
 581                 tftpfile->off += offset;
 582                 break;
 583         default:
 584                 errno = EOFFSET;
 585                 return (-1);
 586         }
 587         return (tftpfile->off);
 588 }
 589
 590 static ssize_t
 591 sendrecv_tftp(struct tftp_handle *h,
 592     ssize_t (*sproc)(struct iodesc *, void *, size_t),
 593     void *sbuf, size_t ssize,
 594     ssize_t (*rproc)(struct tftp_handle *, void *, ssize_t, time_t, unsigned short *),
 595     void *rbuf, size_t rsize, unsigned short *rtype)
 596 {
 597         struct iodesc *d = h->iodesc;
 598         ssize_t cc;
 599         time_t t, t1, tleft;
 600
 601 #ifdef TFTP_DEBUG
 602         if (debug)
 603                 printf("sendrecv: called\n");
 604 #endif
 605
 606         tleft = MINTMO;
 607         t = t1 = getsecs();
 608         for (;;) {
 609                 if ((getsecs() - t) > MAXTMO) {
 610                         errno = ETIMEDOUT;
 611                         return -1;
 612                 }
 613
 614                 cc = (*sproc)(d, sbuf, ssize);
 615                 if (cc != -1 && cc < ssize)
 616                         panic("sendrecv: short write! (%zd < %zu)",
 617                             cc, ssize);
 618
 619                 if (cc == -1) {
 620                         /* Error on transmit; wait before retrying */
 621                         while ((getsecs() - t1) < tleft);
 622                         continue;
 623                 }
 624
 625 recvnext:
 626                 /* Try to get a packet and process it. */
 627                 cc = (*rproc)(h, rbuf, rsize, tleft, rtype);
 628                 /* Return on data, EOF or real error. */
 629                 if (cc != -1 || errno != 0)
 630                         return (cc);
 631                 if ((getsecs() - t1) < tleft) {
 632                     goto recvnext;
 633                 }
 634
 635                 /* Timed out or didn't get the packet we're waiting for */
 636                 tleft += MINTMO;
 637                 if (tleft > (2 * MINTMO)) {
 638                         tleft = (2 * MINTMO);
 639                 }
 640                 t1 = getsecs();
 641         }
 642 }
 643
 644 static int
 645 tftp_set_blksize(struct tftp_handle *h, const char *str)
 646 {
 647         char *endptr;
 648         int new_blksize;
 649         int ret = 0;
 650
 651         if (h == NULL || str == NULL)
 652                 return (ret);
 653
 654         new_blksize =
 655             (unsigned int)strtol(str, &endptr, 0);
 656
 657         /*
 658          * Only accept blksize value if it is numeric.
 659          * RFC2348 specifies that acceptable values are 8-65464.
 660          * Let's choose a limit less than MAXRSPACE.
 661          */
 662         if (*endptr == '\0' && new_blksize >= 8
 663             && new_blksize <= TFTP_MAX_BLKSIZE) {
 664                 h->tftp_blksize = new_blksize;
 665                 ret = 1;
 666         }
 667
 668         return (ret);
 669 }
 670
 671 /*
 672  * In RFC2347, the TFTP Option Acknowledgement package (OACK)
 673  * is used to acknowledge a client's option negotiation request.
 674  * The format of an OACK packet is:
 675  *    +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
 676  *    |  opc  |  opt1  | 0 | value1 | 0 |  optN  | 0 | valueN | 0 |
 677  *    +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
 678  *
 679  *    opc
 680  *       The opcode field contains a 6, for Option Acknowledgment.
 681  *
 682  *    opt1
 683  *       The first option acknowledgment, copied from the original
 684  *       request.
 685  *
 686  *    value1
 687  *       The acknowledged value associated with the first option.  If
 688  *       and how this value may differ from the original request is
 689  *       detailed in the specification for the option.
 690  *
 691  *    optN, valueN
 692  *       The final option/value acknowledgment pair.
 693  */
 694 static int
 695 tftp_parse_oack(struct tftp_handle *h, char *buf, size_t len)
 696 {
 697         /*
 698          *  We parse the OACK strings into an array
 699          *  of name-value pairs.
 700          */
 701         char *tftp_options[128] = { 0 };
 702         char *val = buf;
 703         int i = 0;
 704         int option_idx = 0;
 705         int blksize_is_set = 0;
 706         int tsize = 0;
 707
 708         unsigned int orig_blksize;
 709
 710         while (option_idx < 128 && i < len) {
 711                 if (buf[i] == '\0') {
 712                         if (&buf[i] > val) {
 713                                 tftp_options[option_idx] = val;
 714                                 val = &buf[i] + 1;
 715                                 ++option_idx;
 716                         }
 717                 }
 718                 ++i;
 719         }
 720
 721         /* Save the block size we requested for sanity check later. */
 722         orig_blksize = h->tftp_blksize;
 723
 724         /*
 725          * Parse individual TFTP options.
 726          *    * "blksize" is specified in RFC2348.
 727          *    * "tsize" is specified in RFC2349.
 728          */
 729         for (i = 0; i < option_idx; i += 2) {
 730             if (strcasecmp(tftp_options[i], "blksize") == 0) {
 731                 if (i + 1 < option_idx)
 732                         blksize_is_set =
 733                             tftp_set_blksize(h, tftp_options[i + 1]);
 734             } else if (strcasecmp(tftp_options[i], "tsize") == 0) {
 735                 if (i + 1 < option_idx)
 736                         tsize = strtol(tftp_options[i + 1], (char **)NULL, 10);
 737                 if (tsize != 0)
 738                         h->tftp_tsize = tsize;
 739             } else {
 740                 /* Do not allow any options we did not expect to be ACKed. */
 741                 printf("unexpected tftp option '%s'\n", tftp_options[i]);
 742                 return (-1);
 743             }
 744         }
 745
 746         if (!blksize_is_set) {
 747                 /*
 748                  * If TFTP blksize was not set, try defaulting
 749                  * to the legacy TFTP blksize of SEGSIZE(512)
 750                  */
 751                 h->tftp_blksize = SEGSIZE;
 752         } else if (h->tftp_blksize > orig_blksize) {
 753                 /*
 754                  * Server should not be proposing block sizes that
 755                  * exceed what we said we can handle.
 756                  */
 757                 printf("unexpected blksize %u\n", h->tftp_blksize);
 758                 return (-1);
 759         }
 760
 761 #ifdef TFTP_DEBUG
 762         printf("tftp_blksize: %u\n", h->tftp_blksize);
 763         printf("tftp_tsize: %lu\n", h->tftp_tsize);
 764 #endif
 765         return 0;
 766 }