xref: /freebsd/stand/libsa/tftp.c (revision ca987d4641cdcd7f27e153db17c5bf064934faf5)
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 **, void **, time_t, unsigned short *),
77     void **, void **, 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 	void		*pkt;
118 	struct tftphdr	*tftp_hdr;
119 };
120 
121 #define	TFTP_MAX_ERRCODE EOPTNEG
122 static const int tftperrors[TFTP_MAX_ERRCODE + 1] = {
123 	0,			/* ??? */
124 	ENOENT,
125 	EPERM,
126 	ENOSPC,
127 	EINVAL,			/* ??? */
128 	EINVAL,			/* ??? */
129 	EEXIST,
130 	EINVAL,			/* ??? */
131 	EINVAL,			/* Option negotiation failed. */
132 };
133 
134 static int  tftp_getnextblock(struct tftp_handle *h);
135 
136 /* send error message back. */
137 static void
138 tftp_senderr(struct tftp_handle *h, u_short errcode, const char *msg)
139 {
140 	struct {
141 		u_char header[HEADER_SIZE];
142 		struct tftphdr  t;
143 		u_char space[63]; /* +1 from t */
144 	} __packed __aligned(4) wbuf;
145 	char           *wtail;
146 	int             len;
147 
148 	len = strlen(msg);
149 	if (len > sizeof(wbuf.space))
150 		len = sizeof(wbuf.space);
151 
152 	wbuf.t.th_opcode = htons((u_short) ERROR);
153 	wbuf.t.th_code   = htons(errcode);
154 
155 	wtail = wbuf.t.th_msg;
156 	bcopy(msg, wtail, len);
157 	wtail[len] = '\0';
158 	wtail += len + 1;
159 
160 	sendudp(h->iodesc, &wbuf.t, wtail - (char *) &wbuf.t);
161 }
162 
163 static void
164 tftp_sendack(struct tftp_handle *h)
165 {
166 	struct {
167 		u_char header[HEADER_SIZE];
168 		struct tftphdr  t;
169 	} __packed __aligned(4) wbuf;
170 	char           *wtail;
171 
172 	wbuf.t.th_opcode = htons((u_short) ACK);
173 	wtail = (char *) &wbuf.t.th_block;
174 	wbuf.t.th_block = htons((u_short) h->currblock);
175 	wtail += 2;
176 
177 	sendudp(h->iodesc, &wbuf.t, wtail - (char *) &wbuf.t);
178 }
179 
180 static ssize_t
181 recvtftp(struct tftp_handle *h, void **pkt, void **payload, time_t tleft,
182     unsigned short *rtype)
183 {
184 	struct iodesc *d = h->iodesc;
185 	struct tftphdr *t;
186 	void *ptr = NULL;
187 	ssize_t len;
188 
189 	errno = 0;
190 
191 	len = readudp(d, &ptr, (void **)&t, tleft);
192 
193 	if (len < 4) {
194 		free(ptr);
195 		return (-1);
196 	}
197 
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 			free(ptr);
208 			return (-1);
209 		}
210 		if (d->xid == 1) {
211 			/*
212 			 * First data packet from new port.
213 			 */
214 			struct udphdr *uh;
215 			uh = (struct udphdr *) t - 1;
216 			d->destport = uh->uh_sport;
217 		} /* else check uh_sport has not changed??? */
218 		got = len - (t->th_data - (char *)t);
219 		*pkt = ptr;
220 		*payload = t;
221 		return (got);
222 	}
223 	case ERROR:
224 		if ((unsigned) ntohs(t->th_code) > TFTP_MAX_ERRCODE) {
225 			printf("illegal tftp error %d\n", ntohs(t->th_code));
226 			errno = EIO;
227 		} else {
228 #ifdef TFTP_DEBUG
229 			printf("tftp-error %d\n", ntohs(t->th_code));
230 #endif
231 			errno = tftperrors[ntohs(t->th_code)];
232 		}
233 		free(ptr);
234 		return (-1);
235 	case OACK: {
236 		struct udphdr *uh;
237 		int tftp_oack_len;
238 
239 		/*
240 		 * Unexpected OACK. TFTP transfer already in progress.
241 		 * Drop the pkt.
242 		 */
243 		if (d->xid != 1) {
244 			free(ptr);
245 			return (-1);
246 		}
247 
248 		/*
249 		 * Remember which port this OACK came from, because we need
250 		 * to send the ACK or errors back to it.
251 		 */
252 		uh = (struct udphdr *) t - 1;
253 		d->destport = uh->uh_sport;
254 
255 		/* Parse options ACK-ed by the server. */
256 		tftp_oack_len = len - sizeof(t->th_opcode);
257 		if (tftp_parse_oack(h, t->th_u.tu_stuff, tftp_oack_len) != 0) {
258 			tftp_senderr(h, EOPTNEG, "Malformed OACK");
259 			errno = EIO;
260 			free(ptr);
261 			return (-1);
262 		}
263 		*pkt = ptr;
264 		*payload = t;
265 		return (0);
266 	}
267 	default:
268 #ifdef TFTP_DEBUG
269 		printf("tftp type %d not handled\n", ntohs(t->th_opcode));
270 #endif
271 		free(ptr);
272 		return (-1);
273 	}
274 }
275 
276 /* send request, expect first block (or error) */
277 static int
278 tftp_makereq(struct tftp_handle *h)
279 {
280 	struct {
281 		u_char header[HEADER_SIZE];
282 		struct tftphdr  t;
283 		u_char space[FNAME_SIZE + 6];
284 	} __packed __aligned(4) wbuf;
285 	char           *wtail;
286 	int             l;
287 	ssize_t         res;
288 	void *pkt;
289 	struct tftphdr *t;
290 	char *tftp_blksize = NULL;
291 	int blksize_l;
292 	unsigned short rtype = 0;
293 
294 	/*
295 	 * Allow overriding default TFTP block size by setting
296 	 * a tftp.blksize environment variable.
297 	 */
298 	if ((tftp_blksize = getenv("tftp.blksize")) != NULL) {
299 		tftp_set_blksize(h, tftp_blksize);
300 	}
301 
302 	wbuf.t.th_opcode = htons((u_short) RRQ);
303 	wtail = wbuf.t.th_stuff;
304 	l = strlen(h->path);
305 #ifdef TFTP_PREPEND_PATH
306 	if (l > FNAME_SIZE - (sizeof(TFTP_PREPEND_PATH) - 1))
307 		return (ENAMETOOLONG);
308 	bcopy(TFTP_PREPEND_PATH, wtail, sizeof(TFTP_PREPEND_PATH) - 1);
309 	wtail += sizeof(TFTP_PREPEND_PATH) - 1;
310 #else
311 	if (l > FNAME_SIZE)
312 		return (ENAMETOOLONG);
313 #endif
314 	bcopy(h->path, wtail, l + 1);
315 	wtail += l + 1;
316 	bcopy("octet", wtail, 6);
317 	wtail += 6;
318 	bcopy("blksize", wtail, 8);
319 	wtail += 8;
320 	blksize_l = sprintf(wtail, "%d", h->tftp_blksize);
321 	wtail += blksize_l + 1;
322 	bcopy("tsize", wtail, 6);
323 	wtail += 6;
324 	bcopy("0", wtail, 2);
325 	wtail += 2;
326 
327 	/* h->iodesc->myport = htons(--tftpport); */
328 	h->iodesc->myport = htons(tftpport + (getsecs() & 0x3ff));
329 	h->iodesc->destport = htons(IPPORT_TFTP);
330 	h->iodesc->xid = 1;	/* expected block */
331 
332 	h->currblock = 0;
333 	h->islastblock = 0;
334 	h->validsize = 0;
335 
336 	pkt = NULL;
337 	res = sendrecv_tftp(h, &sendudp, &wbuf.t, wtail - (char *) &wbuf.t,
338 		       &recvtftp, &pkt, (void **)&t, &rtype);
339 	if (res == -1) {
340 		free(pkt);
341 		return (errno);
342 	}
343 
344 	free(h->pkt);
345 	h->pkt = pkt;
346 	h->tftp_hdr = t;
347 
348 	if (rtype == OACK)
349 		return (tftp_getnextblock(h));
350 
351 	/* Server ignored our blksize request, revert to TFTP default. */
352 	h->tftp_blksize = SEGSIZE;
353 
354 	switch (rtype) {
355 		case DATA: {
356 			h->currblock = 1;
357 			h->validsize = res;
358 			h->islastblock = 0;
359 			if (res < h->tftp_blksize) {
360 				h->islastblock = 1;	/* very short file */
361 				tftp_sendack(h);
362 			}
363 			return (0);
364 		}
365 		case ERROR:
366 		default:
367 			return (errno);
368 	}
369 
370 }
371 
372 /* ack block, expect next */
373 static int
374 tftp_getnextblock(struct tftp_handle *h)
375 {
376 	struct {
377 		u_char header[HEADER_SIZE];
378 		struct tftphdr t;
379 	} __packed __aligned(4) wbuf;
380 	char           *wtail;
381 	int             res;
382 	void *pkt;
383 	struct tftphdr *t;
384 	unsigned short rtype = 0;
385 	wbuf.t.th_opcode = htons((u_short) ACK);
386 	wtail = (char *) &wbuf.t.th_block;
387 	wbuf.t.th_block = htons((u_short) h->currblock);
388 	wtail += 2;
389 
390 	h->iodesc->xid = h->currblock + 1;	/* expected block */
391 
392 	pkt = NULL;
393 	res = sendrecv_tftp(h, &sendudp, &wbuf.t, wtail - (char *) &wbuf.t,
394 		       &recvtftp, &pkt, (void **)&t, &rtype);
395 
396 	if (res == -1) {		/* 0 is OK! */
397 		free(pkt);
398 		return (errno);
399 	}
400 
401 	free(h->pkt);
402 	h->pkt = pkt;
403 	h->tftp_hdr = t;
404 	h->currblock++;
405 	h->validsize = res;
406 	if (res < h->tftp_blksize)
407 		h->islastblock = 1;	/* EOF */
408 
409 	if (h->islastblock == 1) {
410 		/* Send an ACK for the last block */
411 		wbuf.t.th_block = htons((u_short) h->currblock);
412 		sendudp(h->iodesc, &wbuf.t, wtail - (char *)&wbuf.t);
413 	}
414 
415 	return (0);
416 }
417 
418 static int
419 tftp_open(const char *path, struct open_file *f)
420 {
421 	struct tftp_handle *tftpfile;
422 	struct iodesc  *io;
423 	int             res;
424 	size_t          pathsize;
425 	const char     *extraslash;
426 
427 	if (netproto != NET_TFTP)
428 		return (EINVAL);
429 
430 	if (f->f_dev->dv_type != DEVT_NET)
431 		return (EINVAL);
432 
433 	if (is_open)
434 		return (EBUSY);
435 
436 	tftpfile = (struct tftp_handle *) malloc(sizeof(*tftpfile));
437 	if (!tftpfile)
438 		return (ENOMEM);
439 
440 	memset(tftpfile, 0, sizeof(*tftpfile));
441 	tftpfile->tftp_blksize = TFTP_REQUESTED_BLKSIZE;
442 	tftpfile->iodesc = io = socktodesc(*(int *) (f->f_devdata));
443 	if (io == NULL)
444 		return (EINVAL);
445 
446 	io->destip = servip;
447 	tftpfile->off = 0;
448 	pathsize = (strlen(rootpath) + 1 + strlen(path) + 1) * sizeof(char);
449 	tftpfile->path = malloc(pathsize);
450 	if (tftpfile->path == NULL) {
451 		free(tftpfile);
452 		return(ENOMEM);
453 	}
454 	if (rootpath[strlen(rootpath) - 1] == '/' || path[0] == '/')
455 		extraslash = "";
456 	else
457 		extraslash = "/";
458 	res = snprintf(tftpfile->path, pathsize, "%s%s%s",
459 	    rootpath, extraslash, path);
460 	if (res < 0 || res > pathsize) {
461 		free(tftpfile->path);
462 		free(tftpfile);
463 		return(ENOMEM);
464 	}
465 
466 	res = tftp_makereq(tftpfile);
467 
468 	if (res) {
469 		free(tftpfile->path);
470 		free(tftpfile->pkt);
471 		free(tftpfile);
472 		return (res);
473 	}
474 	f->f_fsdata = (void *) tftpfile;
475 	is_open = 1;
476 	return (0);
477 }
478 
479 static int
480 tftp_read(struct open_file *f, void *addr, size_t size,
481     size_t *resid /* out */)
482 {
483 	struct tftp_handle *tftpfile;
484 	tftpfile = (struct tftp_handle *) f->f_fsdata;
485 
486 	while (size > 0) {
487 		int needblock, count;
488 
489 		twiddle(32);
490 
491 		needblock = tftpfile->off / tftpfile->tftp_blksize + 1;
492 
493 		if (tftpfile->currblock > needblock) {	/* seek backwards */
494 			tftp_senderr(tftpfile, 0, "No error: read aborted");
495 			tftp_makereq(tftpfile);	/* no error check, it worked
496 						 * for open */
497 		}
498 
499 		while (tftpfile->currblock < needblock) {
500 			int res;
501 
502 			res = tftp_getnextblock(tftpfile);
503 			if (res) {	/* no answer */
504 #ifdef TFTP_DEBUG
505 				printf("tftp: read error\n");
506 #endif
507 				return (res);
508 			}
509 			if (tftpfile->islastblock)
510 				break;
511 		}
512 
513 		if (tftpfile->currblock == needblock) {
514 			int offinblock, inbuffer;
515 
516 			offinblock = tftpfile->off % tftpfile->tftp_blksize;
517 
518 			inbuffer = tftpfile->validsize - offinblock;
519 			if (inbuffer < 0) {
520 #ifdef TFTP_DEBUG
521 				printf("tftp: invalid offset %d\n",
522 				    tftpfile->off);
523 #endif
524 				return (EINVAL);
525 			}
526 			count = (size < inbuffer ? size : inbuffer);
527 			bcopy(tftpfile->tftp_hdr->th_data + offinblock,
528 			    addr, count);
529 
530 			addr = (char *)addr + count;
531 			tftpfile->off += count;
532 			size -= count;
533 
534 			if ((tftpfile->islastblock) && (count == inbuffer))
535 				break;	/* EOF */
536 		} else {
537 #ifdef TFTP_DEBUG
538 			printf("tftp: block %d not found\n", needblock);
539 #endif
540 			return (EINVAL);
541 		}
542 
543 	}
544 
545 	if (resid)
546 		*resid = size;
547 	return (0);
548 }
549 
550 static int
551 tftp_close(struct open_file *f)
552 {
553 	struct tftp_handle *tftpfile;
554 	tftpfile = (struct tftp_handle *) f->f_fsdata;
555 
556 	/* let it time out ... */
557 
558 	if (tftpfile) {
559 		free(tftpfile->path);
560 		free(tftpfile->pkt);
561 		free(tftpfile);
562 	}
563 	is_open = 0;
564 	return (0);
565 }
566 
567 static int
568 tftp_write(struct open_file *f __unused, void *start __unused, size_t size __unused,
569     size_t *resid __unused /* out */)
570 {
571 	return (EROFS);
572 }
573 
574 static int
575 tftp_stat(struct open_file *f, struct stat *sb)
576 {
577 	struct tftp_handle *tftpfile;
578 	tftpfile = (struct tftp_handle *) f->f_fsdata;
579 
580 	sb->st_mode = 0444 | S_IFREG;
581 	sb->st_nlink = 1;
582 	sb->st_uid = 0;
583 	sb->st_gid = 0;
584 	sb->st_size = (off_t) tftpfile->tftp_tsize;
585 	return (0);
586 }
587 
588 static off_t
589 tftp_seek(struct open_file *f, off_t offset, int where)
590 {
591 	struct tftp_handle *tftpfile;
592 	tftpfile = (struct tftp_handle *) f->f_fsdata;
593 
594 	switch (where) {
595 	case SEEK_SET:
596 		tftpfile->off = offset;
597 		break;
598 	case SEEK_CUR:
599 		tftpfile->off += offset;
600 		break;
601 	default:
602 		errno = EOFFSET;
603 		return (-1);
604 	}
605 	return (tftpfile->off);
606 }
607 
608 static ssize_t
609 sendrecv_tftp(struct tftp_handle *h,
610     ssize_t (*sproc)(struct iodesc *, void *, size_t),
611     void *sbuf, size_t ssize,
612     ssize_t (*rproc)(struct tftp_handle *, void **, void **, time_t,
613     unsigned short *),
614     void **pkt, void **payload, unsigned short *rtype)
615 {
616 	struct iodesc *d = h->iodesc;
617 	ssize_t cc;
618 	time_t t, t1, tleft;
619 
620 #ifdef TFTP_DEBUG
621 	if (debug)
622 		printf("sendrecv: called\n");
623 #endif
624 
625 	tleft = MINTMO;
626 	t = t1 = getsecs();
627 	for (;;) {
628 		if ((getsecs() - t) > MAXTMO) {
629 			errno = ETIMEDOUT;
630 			return -1;
631 		}
632 
633 		cc = (*sproc)(d, sbuf, ssize);
634 		if (cc != -1 && cc < ssize)
635 			panic("sendrecv: short write! (%zd < %zu)",
636 			    cc, ssize);
637 
638 		if (cc == -1) {
639 			/* Error on transmit; wait before retrying */
640 			while ((getsecs() - t1) < tleft);
641 			continue;
642 		}
643 
644 recvnext:
645 		/* Try to get a packet and process it. */
646 		cc = (*rproc)(h, pkt, payload, tleft, rtype);
647 		/* Return on data, EOF or real error. */
648 		if (cc != -1 || errno != 0)
649 			return (cc);
650 		if ((getsecs() - t1) < tleft) {
651 		    goto recvnext;
652 		}
653 
654 		/* Timed out or didn't get the packet we're waiting for */
655 		tleft += MINTMO;
656 		if (tleft > (2 * MINTMO)) {
657 			tleft = (2 * MINTMO);
658 		}
659 		t1 = getsecs();
660 	}
661 }
662 
663 static int
664 tftp_set_blksize(struct tftp_handle *h, const char *str)
665 {
666         char *endptr;
667 	int new_blksize;
668 	int ret = 0;
669 
670 	if (h == NULL || str == NULL)
671 		return (ret);
672 
673 	new_blksize =
674 	    (unsigned int)strtol(str, &endptr, 0);
675 
676 	/*
677 	 * Only accept blksize value if it is numeric.
678 	 * RFC2348 specifies that acceptable values are 8-65464.
679 	 * Let's choose a limit less than MAXRSPACE.
680 	 */
681 	if (*endptr == '\0' && new_blksize >= 8
682 	    && new_blksize <= TFTP_MAX_BLKSIZE) {
683 		h->tftp_blksize = new_blksize;
684 		ret = 1;
685 	}
686 
687 	return (ret);
688 }
689 
690 /*
691  * In RFC2347, the TFTP Option Acknowledgement package (OACK)
692  * is used to acknowledge a client's option negotiation request.
693  * The format of an OACK packet is:
694  *    +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
695  *    |  opc  |  opt1  | 0 | value1 | 0 |  optN  | 0 | valueN | 0 |
696  *    +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
697  *
698  *    opc
699  *       The opcode field contains a 6, for Option Acknowledgment.
700  *
701  *    opt1
702  *       The first option acknowledgment, copied from the original
703  *       request.
704  *
705  *    value1
706  *       The acknowledged value associated with the first option.  If
707  *       and how this value may differ from the original request is
708  *       detailed in the specification for the option.
709  *
710  *    optN, valueN
711  *       The final option/value acknowledgment pair.
712  */
713 static int
714 tftp_parse_oack(struct tftp_handle *h, char *buf, size_t len)
715 {
716 	/*
717 	 *  We parse the OACK strings into an array
718 	 *  of name-value pairs.
719 	 */
720 	char *tftp_options[128] = { 0 };
721 	char *val = buf;
722 	int i = 0;
723 	int option_idx = 0;
724 	int blksize_is_set = 0;
725 	int tsize = 0;
726 
727 	unsigned int orig_blksize;
728 
729 	while (option_idx < 128 && i < len) {
730 		if (buf[i] == '\0') {
731 			if (&buf[i] > val) {
732 				tftp_options[option_idx] = val;
733 				val = &buf[i] + 1;
734 				++option_idx;
735 			}
736 		}
737 		++i;
738 	}
739 
740 	/* Save the block size we requested for sanity check later. */
741 	orig_blksize = h->tftp_blksize;
742 
743 	/*
744 	 * Parse individual TFTP options.
745 	 *    * "blksize" is specified in RFC2348.
746 	 *    * "tsize" is specified in RFC2349.
747 	 */
748 	for (i = 0; i < option_idx; i += 2) {
749 	    if (strcasecmp(tftp_options[i], "blksize") == 0) {
750 		if (i + 1 < option_idx)
751 			blksize_is_set =
752 			    tftp_set_blksize(h, tftp_options[i + 1]);
753 	    } else if (strcasecmp(tftp_options[i], "tsize") == 0) {
754 		if (i + 1 < option_idx)
755 			tsize = strtol(tftp_options[i + 1], (char **)NULL, 10);
756 		if (tsize != 0)
757 			h->tftp_tsize = tsize;
758 	    } else {
759 		/* Do not allow any options we did not expect to be ACKed. */
760 		printf("unexpected tftp option '%s'\n", tftp_options[i]);
761 		return (-1);
762 	    }
763 	}
764 
765 	if (!blksize_is_set) {
766 		/*
767 		 * If TFTP blksize was not set, try defaulting
768 		 * to the legacy TFTP blksize of SEGSIZE(512)
769 		 */
770 		h->tftp_blksize = SEGSIZE;
771 	} else if (h->tftp_blksize > orig_blksize) {
772 		/*
773 		 * Server should not be proposing block sizes that
774 		 * exceed what we said we can handle.
775 		 */
776 		printf("unexpected blksize %u\n", h->tftp_blksize);
777 		return (-1);
778 	}
779 
780 #ifdef TFTP_DEBUG
781 	printf("tftp_blksize: %u\n", h->tftp_blksize);
782 	printf("tftp_tsize: %lu\n", h->tftp_tsize);
783 #endif
784 	return 0;
785 }
786