xref: /freebsd/stand/libsa/tftp.c (revision 7cc42f6d25ef2e19059d088fa7d4853fe9afefb5) 
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 struct tftprecv_extra;
65 
66 static ssize_t recvtftp(struct iodesc *, void **, void **, time_t, void *);
67 static int tftp_open(const char *, struct open_file *);
68 static int tftp_close(struct open_file *);
69 static int tftp_parse_oack(struct tftp_handle *, char *, size_t);
70 static int tftp_read(struct open_file *, void *, size_t, size_t *);
71 static off_t tftp_seek(struct open_file *, off_t, int);
72 static int tftp_set_blksize(struct tftp_handle *, const char *);
73 static int tftp_stat(struct open_file *, struct stat *);
74 
75 struct fs_ops tftp_fsops = {
76 	.fs_name = "tftp",
77 	.fo_open = tftp_open,
78 	.fo_close = tftp_close,
79 	.fo_read = tftp_read,
80 	.fo_write = null_write,
81 	.fo_seek = tftp_seek,
82 	.fo_stat = tftp_stat,
83 	.fo_readdir = null_readdir
84 };
85 
86 extern struct in_addr servip;
87 
88 static int	tftpport = 2000;
89 static int	is_open = 0;
90 
91 /*
92  * The legacy TFTP_BLKSIZE value was SEGSIZE(512).
93  * TFTP_REQUESTED_BLKSIZE of 1428 is (Ethernet MTU, less the TFTP, UDP and
94  * IP header lengths).
95  */
96 #define	TFTP_REQUESTED_BLKSIZE 1428
97 
98 /*
99  * Choose a blksize big enough so we can test with Ethernet
100  * Jumbo frames in the future.
101  */
102 #define	TFTP_MAX_BLKSIZE 9008
103 #define TFTP_TRIES 2
104 
105 struct tftp_handle {
106 	struct iodesc  *iodesc;
107 	int		currblock;	/* contents of lastdata */
108 	int		islastblock:1;	/* flag */
109 	int		tries:4;	/* number of read attempts */
110 	int		validsize;
111 	int		off;
112 	char		*path;	/* saved for re-requests */
113 	unsigned int	tftp_blksize;
114 	unsigned long	tftp_tsize;
115 	void		*pkt;
116 	struct tftphdr	*tftp_hdr;
117 };
118 
119 struct tftprecv_extra {
120 	struct tftp_handle	*tftp_handle;
121 	unsigned short		rtype;		/* Received type */
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, u_short block)
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(block);
178 	wtail += 2;
179 
180 	sendudp(h->iodesc, &wbuf.t, wtail - (char *)&wbuf.t);
181 }
182 
183 static ssize_t
184 recvtftp(struct iodesc *d, void **pkt, void **payload, time_t tleft,
185     void *recv_extra)
186 {
187 	struct tftprecv_extra *extra;
188 	struct tftp_handle *h;
189 	struct tftphdr *t;
190 	void *ptr = NULL;
191 	ssize_t len;
192 
193 	errno = 0;
194 	extra = recv_extra;
195 	h = extra->tftp_handle;
196 
197 	len = readudp(d, &ptr, (void **)&t, tleft);
198 
199 	if (len < 4) {
200 		free(ptr);
201 		return (-1);
202 	}
203 
204 	extra->rtype = ntohs(t->th_opcode);
205 	switch (ntohs(t->th_opcode)) {
206 	case DATA: {
207 		int got;
208 
209 		if (htons(t->th_block) < (u_short)d->xid) {
210 			/*
211 			 * Apparently our ACK was missed, re-send.
212 			 */
213 			tftp_sendack(h, htons(t->th_block));
214 			free(ptr);
215 			return (-1);
216 		}
217 		if (htons(t->th_block) != (u_short)d->xid) {
218 			/*
219 			 * Packet from the future, drop this.
220 			 */
221 			free(ptr);
222 			return (-1);
223 		}
224 		if (d->xid == 1) {
225 			/*
226 			 * First data packet from new port.
227 			 */
228 			struct udphdr *uh;
229 			uh = (struct udphdr *)t - 1;
230 			d->destport = uh->uh_sport;
231 		}
232 		got = len - (t->th_data - (char *)t);
233 		*pkt = ptr;
234 		*payload = t;
235 		return (got);
236 	}
237 	case ERROR:
238 		if ((unsigned)ntohs(t->th_code) > TFTP_MAX_ERRCODE) {
239 			printf("illegal tftp error %d\n", ntohs(t->th_code));
240 			errno = EIO;
241 		} else {
242 #ifdef TFTP_DEBUG
243 			printf("tftp-error %d\n", ntohs(t->th_code));
244 #endif
245 			errno = tftperrors[ntohs(t->th_code)];
246 		}
247 		free(ptr);
248 		return (-1);
249 	case OACK: {
250 		struct udphdr *uh;
251 		int tftp_oack_len;
252 
253 		/*
254 		 * Unexpected OACK. TFTP transfer already in progress.
255 		 * Drop the pkt.
256 		 */
257 		if (d->xid != 1) {
258 			free(ptr);
259 			return (-1);
260 		}
261 
262 		/*
263 		 * Remember which port this OACK came from, because we need
264 		 * to send the ACK or errors back to it.
265 		 */
266 		uh = (struct udphdr *)t - 1;
267 		d->destport = uh->uh_sport;
268 
269 		/* Parse options ACK-ed by the server. */
270 		tftp_oack_len = len - sizeof(t->th_opcode);
271 		if (tftp_parse_oack(h, t->th_u.tu_stuff, tftp_oack_len) != 0) {
272 			tftp_senderr(h, EOPTNEG, "Malformed OACK");
273 			errno = EIO;
274 			free(ptr);
275 			return (-1);
276 		}
277 		*pkt = ptr;
278 		*payload = t;
279 		return (0);
280 	}
281 	default:
282 #ifdef TFTP_DEBUG
283 		printf("tftp type %d not handled\n", ntohs(t->th_opcode));
284 #endif
285 		free(ptr);
286 		return (-1);
287 	}
288 }
289 
290 /* send request, expect first block (or error) */
291 static int
292 tftp_makereq(struct tftp_handle *h)
293 {
294 	struct {
295 		u_char header[HEADER_SIZE];
296 		struct tftphdr  t;
297 		u_char space[FNAME_SIZE + 6];
298 	} __packed __aligned(4) wbuf;
299 	struct tftprecv_extra recv_extra;
300 	char *wtail;
301 	int l;
302 	ssize_t res;
303 	void *pkt;
304 	struct tftphdr *t;
305 	char *tftp_blksize = NULL;
306 	int blksize_l;
307 
308 	/*
309 	 * Allow overriding default TFTP block size by setting
310 	 * a tftp.blksize environment variable.
311 	 */
312 	if ((tftp_blksize = getenv("tftp.blksize")) != NULL) {
313 		tftp_set_blksize(h, tftp_blksize);
314 	}
315 
316 	wbuf.t.th_opcode = htons((u_short)RRQ);
317 	wtail = wbuf.t.th_stuff;
318 	l = strlen(h->path);
319 #ifdef TFTP_PREPEND_PATH
320 	if (l > FNAME_SIZE - (sizeof(TFTP_PREPEND_PATH) - 1))
321 		return (ENAMETOOLONG);
322 	bcopy(TFTP_PREPEND_PATH, wtail, sizeof(TFTP_PREPEND_PATH) - 1);
323 	wtail += sizeof(TFTP_PREPEND_PATH) - 1;
324 #else
325 	if (l > FNAME_SIZE)
326 		return (ENAMETOOLONG);
327 #endif
328 	bcopy(h->path, wtail, l + 1);
329 	wtail += l + 1;
330 	bcopy("octet", wtail, 6);
331 	wtail += 6;
332 	bcopy("blksize", wtail, 8);
333 	wtail += 8;
334 	blksize_l = sprintf(wtail, "%d", h->tftp_blksize);
335 	wtail += blksize_l + 1;
336 	bcopy("tsize", wtail, 6);
337 	wtail += 6;
338 	bcopy("0", wtail, 2);
339 	wtail += 2;
340 
341 	h->iodesc->myport = htons(tftpport + (getsecs() & 0x3ff));
342 	h->iodesc->destport = htons(IPPORT_TFTP);
343 	h->iodesc->xid = 1;	/* expected block */
344 
345 	h->currblock = 0;
346 	h->islastblock = 0;
347 	h->validsize = 0;
348 
349 	pkt = NULL;
350 	recv_extra.tftp_handle = h;
351 	res = sendrecv(h->iodesc, &sendudp, &wbuf.t, wtail - (char *)&wbuf.t,
352 	    &recvtftp, &pkt, (void **)&t, &recv_extra);
353 	if (res == -1) {
354 		free(pkt);
355 		return (errno);
356 	}
357 
358 	free(h->pkt);
359 	h->pkt = pkt;
360 	h->tftp_hdr = t;
361 
362 	if (recv_extra.rtype == OACK)
363 		return (tftp_getnextblock(h));
364 
365 	/* Server ignored our blksize request, revert to TFTP default. */
366 	h->tftp_blksize = SEGSIZE;
367 
368 	switch (recv_extra.rtype) {
369 		case DATA: {
370 			h->currblock = 1;
371 			h->validsize = res;
372 			h->islastblock = 0;
373 			if (res < h->tftp_blksize) {
374 				h->islastblock = 1;	/* very short file */
375 				tftp_sendack(h, h->currblock);
376 			}
377 			return (0);
378 		}
379 		case ERROR:
380 		default:
381 			return (errno);
382 	}
383 
384 }
385 
386 /* ack block, expect next */
387 static int
388 tftp_getnextblock(struct tftp_handle *h)
389 {
390 	struct {
391 		u_char header[HEADER_SIZE];
392 		struct tftphdr t;
393 	} __packed __aligned(4) wbuf;
394 	struct tftprecv_extra recv_extra;
395 	char *wtail;
396 	int res;
397 	void *pkt;
398 	struct tftphdr *t;
399 
400 	wbuf.t.th_opcode = htons((u_short)ACK);
401 	wtail = (char *)&wbuf.t.th_block;
402 	wbuf.t.th_block = htons((u_short)h->currblock);
403 	wtail += 2;
404 
405 	h->iodesc->xid = h->currblock + 1;	/* expected block */
406 
407 	pkt = NULL;
408 	recv_extra.tftp_handle = h;
409 	res = sendrecv(h->iodesc, &sendudp, &wbuf.t, wtail - (char *)&wbuf.t,
410 	    &recvtftp, &pkt, (void **)&t, &recv_extra);
411 
412 	if (res == -1) {		/* 0 is OK! */
413 		free(pkt);
414 		return (errno);
415 	}
416 
417 	free(h->pkt);
418 	h->pkt = pkt;
419 	h->tftp_hdr = t;
420 	h->currblock++;
421 	h->validsize = res;
422 	if (res < h->tftp_blksize)
423 		h->islastblock = 1;	/* EOF */
424 
425 	if (h->islastblock == 1) {
426 		/* Send an ACK for the last block */
427 		wbuf.t.th_block = htons((u_short)h->currblock);
428 		sendudp(h->iodesc, &wbuf.t, wtail - (char *)&wbuf.t);
429 	}
430 
431 	return (0);
432 }
433 
434 static int
435 tftp_open(const char *path, struct open_file *f)
436 {
437 	struct tftp_handle *tftpfile;
438 	struct iodesc	*io;
439 	int		res;
440 	size_t		pathsize;
441 	const char	*extraslash;
442 
443 	if (netproto != NET_TFTP)
444 		return (EINVAL);
445 
446 	if (f->f_dev->dv_type != DEVT_NET)
447 		return (EINVAL);
448 
449 	if (is_open)
450 		return (EBUSY);
451 
452 	tftpfile = calloc(1, sizeof(*tftpfile));
453 	if (!tftpfile)
454 		return (ENOMEM);
455 
456 	tftpfile->tftp_blksize = TFTP_REQUESTED_BLKSIZE;
457 	tftpfile->iodesc = io = socktodesc(*(int *)(f->f_devdata));
458 	if (io == NULL) {
459 		free(tftpfile);
460 		return (EINVAL);
461 	}
462 
463 	io->destip = servip;
464 	tftpfile->off = 0;
465 	pathsize = (strlen(rootpath) + 1 + strlen(path) + 1) * sizeof(char);
466 	tftpfile->path = malloc(pathsize);
467 	if (tftpfile->path == NULL) {
468 		free(tftpfile);
469 		return (ENOMEM);
470 	}
471 	if (rootpath[strlen(rootpath) - 1] == '/' || path[0] == '/')
472 		extraslash = "";
473 	else
474 		extraslash = "/";
475 	res = snprintf(tftpfile->path, pathsize, "%s%s%s",
476 	    rootpath, extraslash, path);
477 	if (res < 0 || res > pathsize) {
478 		free(tftpfile->path);
479 		free(tftpfile);
480 		return (ENOMEM);
481 	}
482 
483 	res = tftp_makereq(tftpfile);
484 
485 	if (res) {
486 		free(tftpfile->path);
487 		free(tftpfile->pkt);
488 		free(tftpfile);
489 		return (res);
490 	}
491 	f->f_fsdata = tftpfile;
492 	is_open = 1;
493 	return (0);
494 }
495 
496 static int
497 tftp_read(struct open_file *f, void *addr, size_t size,
498     size_t *resid /* out */)
499 {
500 	struct tftp_handle *tftpfile;
501 	size_t res;
502 	int rc;
503 
504 	rc = 0;
505 	res = size;
506 	tftpfile = f->f_fsdata;
507 
508 	/* Make sure we will not read past file end */
509 	if (tftpfile->tftp_tsize > 0 &&
510 	    tftpfile->off + size > tftpfile->tftp_tsize) {
511 		size = tftpfile->tftp_tsize - tftpfile->off;
512 	}
513 
514 	while (size > 0) {
515 		int needblock, count;
516 
517 		twiddle(32);
518 
519 		needblock = tftpfile->off / tftpfile->tftp_blksize + 1;
520 
521 		if (tftpfile->currblock > needblock) {	/* seek backwards */
522 			tftp_senderr(tftpfile, 0, "No error: read aborted");
523 			rc = tftp_makereq(tftpfile);
524 			if (rc != 0)
525 				break;
526 		}
527 
528 		while (tftpfile->currblock < needblock) {
529 
530 			rc = tftp_getnextblock(tftpfile);
531 			if (rc) {	/* no answer */
532 #ifdef TFTP_DEBUG
533 				printf("tftp: read error\n");
534 #endif
535 				if (tftpfile->tries > TFTP_TRIES) {
536 					return (rc);
537 				} else {
538 					tftpfile->tries++;
539 					tftp_makereq(tftpfile);
540 				}
541 			}
542 			if (tftpfile->islastblock)
543 				break;
544 		}
545 
546 		if (tftpfile->currblock == needblock) {
547 			int offinblock, inbuffer;
548 
549 			offinblock = tftpfile->off % tftpfile->tftp_blksize;
550 
551 			inbuffer = tftpfile->validsize - offinblock;
552 			if (inbuffer < 0) {
553 #ifdef TFTP_DEBUG
554 				printf("tftp: invalid offset %d\n",
555 				    tftpfile->off);
556 #endif
557 				return (EINVAL);
558 			}
559 			count = (size < inbuffer ? size : inbuffer);
560 			bcopy(tftpfile->tftp_hdr->th_data + offinblock,
561 			    addr, count);
562 
563 			addr = (char *)addr + count;
564 			tftpfile->off += count;
565 			size -= count;
566 			res -= count;
567 
568 			if ((tftpfile->islastblock) && (count == inbuffer))
569 				break;	/* EOF */
570 		} else {
571 #ifdef TFTP_DEBUG
572 			printf("tftp: block %d not found\n", needblock);
573 #endif
574 			return (EINVAL);
575 		}
576 
577 	}
578 
579 	if (resid != NULL)
580 		*resid = res;
581 	return (rc);
582 }
583 
584 static int
585 tftp_close(struct open_file *f)
586 {
587 	struct tftp_handle *tftpfile;
588 	tftpfile = f->f_fsdata;
589 
590 	/* let it time out ... */
591 
592 	if (tftpfile) {
593 		free(tftpfile->path);
594 		free(tftpfile->pkt);
595 		free(tftpfile);
596 	}
597 	is_open = 0;
598 	return (0);
599 }
600 
601 static int
602 tftp_stat(struct open_file *f, struct stat *sb)
603 {
604 	struct tftp_handle *tftpfile;
605 	tftpfile = f->f_fsdata;
606 
607 	sb->st_mode = 0444 | S_IFREG;
608 	sb->st_nlink = 1;
609 	sb->st_uid = 0;
610 	sb->st_gid = 0;
611 	sb->st_size = tftpfile->tftp_tsize;
612 	return (0);
613 }
614 
615 static off_t
616 tftp_seek(struct open_file *f, off_t offset, int where)
617 {
618 	struct tftp_handle *tftpfile;
619 	tftpfile = f->f_fsdata;
620 
621 	switch (where) {
622 	case SEEK_SET:
623 		tftpfile->off = offset;
624 		break;
625 	case SEEK_CUR:
626 		tftpfile->off += offset;
627 		break;
628 	default:
629 		errno = EOFFSET;
630 		return (-1);
631 	}
632 	return (tftpfile->off);
633 }
634 
635 static int
636 tftp_set_blksize(struct tftp_handle *h, const char *str)
637 {
638 	char *endptr;
639 	int new_blksize;
640 	int ret = 0;
641 
642 	if (h == NULL || str == NULL)
643 		return (ret);
644 
645 	new_blksize =
646 	    (unsigned int)strtol(str, &endptr, 0);
647 
648 	/*
649 	 * Only accept blksize value if it is numeric.
650 	 * RFC2348 specifies that acceptable values are 8-65464.
651 	 * Let's choose a limit less than MAXRSPACE.
652 	 */
653 	if (*endptr == '\0' && new_blksize >= 8 &&
654 	    new_blksize <= TFTP_MAX_BLKSIZE) {
655 		h->tftp_blksize = new_blksize;
656 		ret = 1;
657 	}
658 
659 	return (ret);
660 }
661 
662 /*
663  * In RFC2347, the TFTP Option Acknowledgement package (OACK)
664  * is used to acknowledge a client's option negotiation request.
665  * The format of an OACK packet is:
666  *    +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
667  *    |  opc  |  opt1  | 0 | value1 | 0 |  optN  | 0 | valueN | 0 |
668  *    +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
669  *
670  *    opc
671  *       The opcode field contains a 6, for Option Acknowledgment.
672  *
673  *    opt1
674  *       The first option acknowledgment, copied from the original
675  *       request.
676  *
677  *    value1
678  *       The acknowledged value associated with the first option.  If
679  *       and how this value may differ from the original request is
680  *       detailed in the specification for the option.
681  *
682  *    optN, valueN
683  *       The final option/value acknowledgment pair.
684  */
685 static int
686 tftp_parse_oack(struct tftp_handle *h, char *buf, size_t len)
687 {
688 	/*
689 	 *  We parse the OACK strings into an array
690 	 *  of name-value pairs.
691 	 */
692 	char *tftp_options[128] = { 0 };
693 	char *val = buf;
694 	int i = 0;
695 	int option_idx = 0;
696 	int blksize_is_set = 0;
697 	int tsize = 0;
698 
699 	unsigned int orig_blksize;
700 
701 	while (option_idx < 128 && i < len) {
702 		if (buf[i] == '\0') {
703 			if (&buf[i] > val) {
704 				tftp_options[option_idx] = val;
705 				val = &buf[i] + 1;
706 				++option_idx;
707 			}
708 		}
709 		++i;
710 	}
711 
712 	/* Save the block size we requested for sanity check later. */
713 	orig_blksize = h->tftp_blksize;
714 
715 	/*
716 	 * Parse individual TFTP options.
717 	 *    * "blksize" is specified in RFC2348.
718 	 *    * "tsize" is specified in RFC2349.
719 	 */
720 	for (i = 0; i < option_idx; i += 2) {
721 		if (strcasecmp(tftp_options[i], "blksize") == 0) {
722 			if (i + 1 < option_idx)
723 				blksize_is_set =
724 				    tftp_set_blksize(h, tftp_options[i + 1]);
725 		} else if (strcasecmp(tftp_options[i], "tsize") == 0) {
726 			if (i + 1 < option_idx)
727 				tsize = strtol(tftp_options[i + 1], NULL, 10);
728 			if (tsize != 0)
729 				h->tftp_tsize = tsize;
730 		} else {
731 			/*
732 			 * Do not allow any options we did not expect to be
733 			 * ACKed.
734 			 */
735 			printf("unexpected tftp option '%s'\n",
736 			    tftp_options[i]);
737 			return (-1);
738 		}
739 	}
740 
741 	if (!blksize_is_set) {
742 		/*
743 		 * If TFTP blksize was not set, try defaulting
744 		 * to the legacy TFTP blksize of SEGSIZE(512)
745 		 */
746 		h->tftp_blksize = SEGSIZE;
747 	} else if (h->tftp_blksize > orig_blksize) {
748 		/*
749 		 * Server should not be proposing block sizes that
750 		 * exceed what we said we can handle.
751 		 */
752 		printf("unexpected blksize %u\n", h->tftp_blksize);
753 		return (-1);
754 	}
755 
756 #ifdef TFTP_DEBUG
757 	printf("tftp_blksize: %u\n", h->tftp_blksize);
758 	printf("tftp_tsize: %lu\n", h->tftp_tsize);
759 #endif
760 	return (0);
761 }
762