tftpd.c revision 112452 
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
35static const char copyright[] =
36"@(#) Copyright (c) 1983, 1993\n\
37	The Regents of the University of California.  All rights reserved.\n";
38#endif /* not lint */
39
40#ifndef lint
41#if 0
42static char sccsid[] = "@(#)tftpd.c	8.1 (Berkeley) 6/4/93";
43#endif
44static const char rcsid[] =
45  "$FreeBSD: head/libexec/tftpd/tftpd.c 112452 2003-03-20 22:42:22Z dwmalone $";
46#endif /* not lint */
47
48/*
49 * Trivial file transfer protocol server.
50 *
51 * This version includes many modifications by Jim Guyton
52 * <guyton@rand-unix>.
53 */
54
55#include <sys/param.h>
56#include <sys/ioctl.h>
57#include <sys/stat.h>
58#include <sys/socket.h>
59#include <sys/types.h>
60
61#include <netinet/in.h>
62#include <arpa/tftp.h>
63#include <arpa/inet.h>
64
65#include <ctype.h>
66#include <errno.h>
67#include <fcntl.h>
68#include <libutil.h>
69#include <netdb.h>
70#include <pwd.h>
71#include <setjmp.h>
72#include <signal.h>
73#include <stdio.h>
74#include <stdlib.h>
75#include <string.h>
76#include <syslog.h>
77#include <unistd.h>
78
79#include "tftpsubs.h"
80
81#define	TIMEOUT		5
82#define	MAX_TIMEOUTS	5
83
84int	peer;
85int	rexmtval = TIMEOUT;
86int	max_rexmtval = 2*TIMEOUT;
87
88#define	PKTSIZE	SEGSIZE+4
89char	buf[PKTSIZE];
90char	ackbuf[PKTSIZE];
91struct	sockaddr_storage from;
92int	fromlen;
93
94void	tftp(struct tftphdr *, int);
95static void unmappedaddr(struct sockaddr_in6 *);
96
97/*
98 * Null-terminated directory prefix list for absolute pathname requests and
99 * search list for relative pathname requests.
100 *
101 * MAXDIRS should be at least as large as the number of arguments that
102 * inetd allows (currently 20).
103 */
104#define MAXDIRS	20
105static struct dirlist {
106	const char	*name;
107	int	len;
108} dirs[MAXDIRS+1];
109static int	suppress_naks;
110static int	logging;
111static int	ipchroot;
112
113static const char *errtomsg(int);
114static void  nak(int);
115static void  oack(void);
116
117static void  timer(int);
118static void  justquit(int);
119
120int
121main(int argc, char *argv[])
122{
123	struct tftphdr *tp;
124	int n;
125	int ch, on;
126	struct sockaddr_storage me;
127	int len;
128	char *chroot_dir = NULL;
129	struct passwd *nobody;
130	const char *chuser = "nobody";
131
132	openlog("tftpd", LOG_PID | LOG_NDELAY, LOG_FTP);
133	while ((ch = getopt(argc, argv, "cClns:u:")) != -1) {
134		switch (ch) {
135		case 'c':
136			ipchroot = 1;
137			break;
138		case 'C':
139			ipchroot = 2;
140			break;
141		case 'l':
142			logging = 1;
143			break;
144		case 'n':
145			suppress_naks = 1;
146			break;
147		case 's':
148			chroot_dir = optarg;
149			break;
150		case 'u':
151			chuser = optarg;
152			break;
153		default:
154			syslog(LOG_WARNING, "ignoring unknown option -%c", ch);
155		}
156	}
157	if (optind < argc) {
158		struct dirlist *dirp;
159
160		/* Get list of directory prefixes. Skip relative pathnames. */
161		for (dirp = dirs; optind < argc && dirp < &dirs[MAXDIRS];
162		     optind++) {
163			if (argv[optind][0] == '/') {
164				dirp->name = argv[optind];
165				dirp->len  = strlen(dirp->name);
166				dirp++;
167			}
168		}
169	}
170	else if (chroot_dir) {
171		dirs->name = "/";
172		dirs->len = 1;
173	}
174	if (ipchroot && chroot_dir == NULL) {
175		syslog(LOG_ERR, "-c requires -s");
176		exit(1);
177	}
178
179	on = 1;
180	if (ioctl(0, FIONBIO, &on) < 0) {
181		syslog(LOG_ERR, "ioctl(FIONBIO): %m");
182		exit(1);
183	}
184	fromlen = sizeof (from);
185	n = recvfrom(0, buf, sizeof (buf), 0,
186	    (struct sockaddr *)&from, &fromlen);
187	if (n < 0) {
188		syslog(LOG_ERR, "recvfrom: %m");
189		exit(1);
190	}
191	/*
192	 * Now that we have read the message out of the UDP
193	 * socket, we fork and exit.  Thus, inetd will go back
194	 * to listening to the tftp port, and the next request
195	 * to come in will start up a new instance of tftpd.
196	 *
197	 * We do this so that inetd can run tftpd in "wait" mode.
198	 * The problem with tftpd running in "nowait" mode is that
199	 * inetd may get one or more successful "selects" on the
200	 * tftp port before we do our receive, so more than one
201	 * instance of tftpd may be started up.  Worse, if tftpd
202	 * break before doing the above "recvfrom", inetd would
203	 * spawn endless instances, clogging the system.
204	 */
205	{
206		int pid;
207		int i, j;
208
209		for (i = 1; i < 20; i++) {
210		    pid = fork();
211		    if (pid < 0) {
212				sleep(i);
213				/*
214				 * flush out to most recently sent request.
215				 *
216				 * This may drop some request, but those
217				 * will be resent by the clients when
218				 * they timeout.  The positive effect of
219				 * this flush is to (try to) prevent more
220				 * than one tftpd being started up to service
221				 * a single request from a single client.
222				 */
223				j = sizeof from;
224				i = recvfrom(0, buf, sizeof (buf), 0,
225				    (struct sockaddr *)&from, &j);
226				if (i > 0) {
227					n = i;
228					fromlen = j;
229				}
230		    } else {
231				break;
232		    }
233		}
234		if (pid < 0) {
235			syslog(LOG_ERR, "fork: %m");
236			exit(1);
237		} else if (pid != 0) {
238			exit(0);
239		}
240	}
241
242	/*
243	 * Since we exit here, we should do that only after the above
244	 * recvfrom to keep inetd from constantly forking should there
245	 * be a problem.  See the above comment about system clogging.
246	 */
247	if (chroot_dir) {
248		if (ipchroot) {
249			char *tempchroot;
250			struct stat sb;
251			int statret;
252			struct sockaddr_storage ss;
253			char hbuf[NI_MAXHOST];
254
255			memcpy(&ss, &from, from.ss_len);
256			unmappedaddr((struct sockaddr_in6 *)&ss);
257			getnameinfo((struct sockaddr *)&ss, ss.ss_len,
258				    hbuf, sizeof(hbuf), NULL, 0,
259				    NI_NUMERICHOST | NI_WITHSCOPEID);
260			asprintf(&tempchroot, "%s/%s", chroot_dir, hbuf);
261			statret = stat(tempchroot, &sb);
262			if ((sb.st_mode & S_IFDIR) &&
263			    (statret == 0 || (statret == -1 && ipchroot == 1)))
264				chroot_dir = tempchroot;
265		}
266		/* Must get this before chroot because /etc might go away */
267		if ((nobody = getpwnam(chuser)) == NULL) {
268			syslog(LOG_ERR, "%s: no such user", chuser);
269			exit(1);
270		}
271		if (chroot(chroot_dir)) {
272			syslog(LOG_ERR, "chroot: %s: %m", chroot_dir);
273			exit(1);
274		}
275		chdir( "/" );
276		setuid(nobody->pw_uid);
277		setgroups(1, &nobody->pw_gid);
278	}
279
280	len = sizeof(me);
281	if (getsockname(0, (struct sockaddr *)&me, &len) == 0) {
282		switch (me.ss_family) {
283		case AF_INET:
284			((struct sockaddr_in *)&me)->sin_port = 0;
285			break;
286		case AF_INET6:
287			((struct sockaddr_in6 *)&me)->sin6_port = 0;
288			break;
289		default:
290			/* unsupported */
291			break;
292		}
293	} else {
294		memset(&me, 0, sizeof(me));
295		me.ss_family = from.ss_family;
296		me.ss_len = from.ss_len;
297	}
298	alarm(0);
299	close(0);
300	close(1);
301	peer = socket(from.ss_family, SOCK_DGRAM, 0);
302	if (peer < 0) {
303		syslog(LOG_ERR, "socket: %m");
304		exit(1);
305	}
306	if (bind(peer, (struct sockaddr *)&me, me.ss_len) < 0) {
307		syslog(LOG_ERR, "bind: %m");
308		exit(1);
309	}
310	if (connect(peer, (struct sockaddr *)&from, from.ss_len) < 0) {
311		syslog(LOG_ERR, "connect: %m");
312		exit(1);
313	}
314	tp = (struct tftphdr *)buf;
315	tp->th_opcode = ntohs(tp->th_opcode);
316	if (tp->th_opcode == RRQ || tp->th_opcode == WRQ)
317		tftp(tp, n);
318	exit(1);
319}
320
321struct formats;
322int	validate_access(char **, int);
323void	xmitfile(struct formats *);
324void	recvfile(struct formats *);
325
326struct formats {
327	const char	*f_mode;
328	int	(*f_validate)(char **, int);
329	void	(*f_send)(struct formats *);
330	void	(*f_recv)(struct formats *);
331	int	f_convert;
332} formats[] = {
333	{ "netascii",	validate_access,	xmitfile,	recvfile, 1 },
334	{ "octet",	validate_access,	xmitfile,	recvfile, 0 },
335#ifdef notdef
336	{ "mail",	validate_user,		sendmail,	recvmail, 1 },
337#endif
338	{ 0,		NULL,			NULL,		NULL,	  0 }
339};
340
341struct options {
342	const char	*o_type;
343	char	*o_request;
344	int	o_reply;	/* turn into union if need be */
345} options[] = {
346	{ "tsize",	NULL, 0 },		/* OPT_TSIZE */
347	{ "timeout",	NULL, 0 },		/* OPT_TIMEOUT */
348	{ NULL,		NULL, 0 }
349};
350
351enum opt_enum {
352	OPT_TSIZE = 0,
353	OPT_TIMEOUT,
354};
355
356/*
357 * Handle initial connection protocol.
358 */
359void
360tftp(struct tftphdr *tp, int size)
361{
362	char *cp;
363	int i, first = 1, has_options = 0, ecode;
364	struct formats *pf;
365	char *filename, *mode, *option, *ccp;
366
367	filename = cp = tp->th_stuff;
368again:
369	while (cp < buf + size) {
370		if (*cp == '\0')
371			break;
372		cp++;
373	}
374	if (*cp != '\0') {
375		nak(EBADOP);
376		exit(1);
377	}
378	if (first) {
379		mode = ++cp;
380		first = 0;
381		goto again;
382	}
383	for (cp = mode; *cp; cp++)
384		if (isupper(*cp))
385			*cp = tolower(*cp);
386	for (pf = formats; pf->f_mode; pf++)
387		if (strcmp(pf->f_mode, mode) == 0)
388			break;
389	if (pf->f_mode == 0) {
390		nak(EBADOP);
391		exit(1);
392	}
393	while (++cp < buf + size) {
394		for (i = 2, ccp = cp; i > 0; ccp++) {
395			if (ccp >= buf + size) {
396				/*
397				 * Don't reject the request, just stop trying
398				 * to parse the option and get on with it.
399				 * Some Apple OpenFirmware versions have
400				 * trailing garbage on the end of otherwise
401				 * valid requests.
402				 */
403				goto option_fail;
404			} else if (*ccp == '\0')
405				i--;
406		}
407		for (option = cp; *cp; cp++)
408			if (isupper(*cp))
409				*cp = tolower(*cp);
410		for (i = 0; options[i].o_type != NULL; i++)
411			if (strcmp(option, options[i].o_type) == 0) {
412				options[i].o_request = ++cp;
413				has_options = 1;
414			}
415		cp = ccp-1;
416	}
417
418option_fail:
419	if (options[OPT_TIMEOUT].o_request) {
420		int to = atoi(options[OPT_TIMEOUT].o_request);
421		if (to < 1 || to > 255) {
422			nak(EBADOP);
423			exit(1);
424		}
425		else if (to <= max_rexmtval)
426			options[OPT_TIMEOUT].o_reply = rexmtval = to;
427		else
428			options[OPT_TIMEOUT].o_request = NULL;
429	}
430
431	ecode = (*pf->f_validate)(&filename, tp->th_opcode);
432	if (has_options)
433		oack();
434	if (logging) {
435		char hbuf[NI_MAXHOST];
436
437		getnameinfo((struct sockaddr *)&from, from.ss_len,
438			    hbuf, sizeof(hbuf), NULL, 0,
439			    NI_WITHSCOPEID);
440		syslog(LOG_INFO, "%s: %s request for %s: %s", hbuf,
441			tp->th_opcode == WRQ ? "write" : "read",
442			filename, errtomsg(ecode));
443	}
444	if (ecode) {
445		/*
446		 * Avoid storms of naks to a RRQ broadcast for a relative
447		 * bootfile pathname from a diskless Sun.
448		 */
449		if (suppress_naks && *filename != '/' && ecode == ENOTFOUND)
450			exit(0);
451		nak(ecode);
452		exit(1);
453	}
454	if (tp->th_opcode == WRQ)
455		(*pf->f_recv)(pf);
456	else
457		(*pf->f_send)(pf);
458	exit(0);
459}
460
461
462FILE *file;
463
464/*
465 * Validate file access.  Since we
466 * have no uid or gid, for now require
467 * file to exist and be publicly
468 * readable/writable.
469 * If we were invoked with arguments
470 * from inetd then the file must also be
471 * in one of the given directory prefixes.
472 * Note also, full path name must be
473 * given as we have no login directory.
474 */
475int
476validate_access(char **filep, int mode)
477{
478	struct stat stbuf;
479	int	fd;
480	struct dirlist *dirp;
481	static char pathname[MAXPATHLEN];
482	char *filename = *filep;
483
484	/*
485	 * Prevent tricksters from getting around the directory restrictions
486	 */
487	if (strstr(filename, "/../"))
488		return (EACCESS);
489
490	if (*filename == '/') {
491		/*
492		 * Allow the request if it's in one of the approved locations.
493		 * Special case: check the null prefix ("/") by looking
494		 * for length = 1 and relying on the arg. processing that
495		 * it's a /.
496		 */
497		for (dirp = dirs; dirp->name != NULL; dirp++) {
498			if (dirp->len == 1 ||
499			    (!strncmp(filename, dirp->name, dirp->len) &&
500			     filename[dirp->len] == '/'))
501				    break;
502		}
503		/* If directory list is empty, allow access to any file */
504		if (dirp->name == NULL && dirp != dirs)
505			return (EACCESS);
506		if (stat(filename, &stbuf) < 0)
507			return (errno == ENOENT ? ENOTFOUND : EACCESS);
508		if ((stbuf.st_mode & S_IFMT) != S_IFREG)
509			return (ENOTFOUND);
510		if (mode == RRQ) {
511			if ((stbuf.st_mode & S_IROTH) == 0)
512				return (EACCESS);
513		} else {
514			if ((stbuf.st_mode & S_IWOTH) == 0)
515				return (EACCESS);
516		}
517	} else {
518		int err;
519
520		/*
521		 * Relative file name: search the approved locations for it.
522		 * Don't allow write requests that avoid directory
523		 * restrictions.
524		 */
525
526		if (!strncmp(filename, "../", 3))
527			return (EACCESS);
528
529		/*
530		 * If the file exists in one of the directories and isn't
531		 * readable, continue looking. However, change the error code
532		 * to give an indication that the file exists.
533		 */
534		err = ENOTFOUND;
535		for (dirp = dirs; dirp->name != NULL; dirp++) {
536			snprintf(pathname, sizeof(pathname), "%s/%s",
537				dirp->name, filename);
538			if (stat(pathname, &stbuf) == 0 &&
539			    (stbuf.st_mode & S_IFMT) == S_IFREG) {
540				if ((stbuf.st_mode & S_IROTH) != 0) {
541					break;
542				}
543				err = EACCESS;
544			}
545		}
546		if (dirp->name == NULL)
547			return (err);
548		*filep = filename = pathname;
549	}
550	if (options[OPT_TSIZE].o_request) {
551		if (mode == RRQ)
552			options[OPT_TSIZE].o_reply = stbuf.st_size;
553		else
554			/* XXX Allows writes of all sizes. */
555			options[OPT_TSIZE].o_reply =
556				atoi(options[OPT_TSIZE].o_request);
557	}
558	fd = open(filename, mode == RRQ ? O_RDONLY : O_WRONLY|O_TRUNC);
559	if (fd < 0)
560		return (errno + 100);
561	file = fdopen(fd, (mode == RRQ)? "r":"w");
562	if (file == NULL) {
563		return errno+100;
564	}
565	return (0);
566}
567
568int	timeouts;
569jmp_buf	timeoutbuf;
570
571void
572timer(int sig __unused)
573{
574	if (++timeouts > MAX_TIMEOUTS)
575		exit(1);
576	longjmp(timeoutbuf, 1);
577}
578
579/*
580 * Send the requested file.
581 */
582void
583xmitfile(struct formats *pf)
584{
585	struct tftphdr *dp;
586	struct tftphdr *ap;    /* ack packet */
587	int size, n;
588	volatile unsigned short block;
589
590	signal(SIGALRM, timer);
591	dp = r_init();
592	ap = (struct tftphdr *)ackbuf;
593	block = 1;
594	do {
595		size = readit(file, &dp, pf->f_convert);
596		if (size < 0) {
597			nak(errno + 100);
598			goto abort;
599		}
600		dp->th_opcode = htons((u_short)DATA);
601		dp->th_block = htons((u_short)block);
602		timeouts = 0;
603		(void)setjmp(timeoutbuf);
604
605send_data:
606		{
607			int i, t = 1;
608			for (i = 0; ; i++){
609				if (send(peer, dp, size + 4, 0) != size + 4) {
610					sleep(t);
611					t = (t < 32) ? t<< 1 : t;
612					if (i >= 12) {
613						syslog(LOG_ERR, "write: %m");
614						goto abort;
615					}
616				}
617				break;
618			}
619		}
620		read_ahead(file, pf->f_convert);
621		for ( ; ; ) {
622			alarm(rexmtval);        /* read the ack */
623			n = recv(peer, ackbuf, sizeof (ackbuf), 0);
624			alarm(0);
625			if (n < 0) {
626				syslog(LOG_ERR, "read: %m");
627				goto abort;
628			}
629			ap->th_opcode = ntohs((u_short)ap->th_opcode);
630			ap->th_block = ntohs((u_short)ap->th_block);
631
632			if (ap->th_opcode == ERROR)
633				goto abort;
634
635			if (ap->th_opcode == ACK) {
636				if (ap->th_block == block)
637					break;
638				/* Re-synchronize with the other side */
639				(void) synchnet(peer);
640				if (ap->th_block == (block -1))
641					goto send_data;
642			}
643
644		}
645		block++;
646	} while (size == SEGSIZE);
647abort:
648	(void) fclose(file);
649}
650
651void
652justquit(int sig __unused)
653{
654	exit(0);
655}
656
657
658/*
659 * Receive a file.
660 */
661void
662recvfile(struct formats *pf)
663{
664	struct tftphdr *dp;
665	struct tftphdr *ap;    /* ack buffer */
666	int n, size;
667	volatile unsigned short block;
668
669	signal(SIGALRM, timer);
670	dp = w_init();
671	ap = (struct tftphdr *)ackbuf;
672	block = 0;
673	do {
674		timeouts = 0;
675		ap->th_opcode = htons((u_short)ACK);
676		ap->th_block = htons((u_short)block);
677		block++;
678		(void) setjmp(timeoutbuf);
679send_ack:
680		if (send(peer, ackbuf, 4, 0) != 4) {
681			syslog(LOG_ERR, "write: %m");
682			goto abort;
683		}
684		write_behind(file, pf->f_convert);
685		for ( ; ; ) {
686			alarm(rexmtval);
687			n = recv(peer, dp, PKTSIZE, 0);
688			alarm(0);
689			if (n < 0) {            /* really? */
690				syslog(LOG_ERR, "read: %m");
691				goto abort;
692			}
693			dp->th_opcode = ntohs((u_short)dp->th_opcode);
694			dp->th_block = ntohs((u_short)dp->th_block);
695			if (dp->th_opcode == ERROR)
696				goto abort;
697			if (dp->th_opcode == DATA) {
698				if (dp->th_block == block) {
699					break;   /* normal */
700				}
701				/* Re-synchronize with the other side */
702				(void) synchnet(peer);
703				if (dp->th_block == (block-1))
704					goto send_ack;          /* rexmit */
705			}
706		}
707		/*  size = write(file, dp->th_data, n - 4); */
708		size = writeit(file, &dp, n - 4, pf->f_convert);
709		if (size != (n-4)) {                    /* ahem */
710			if (size < 0) nak(errno + 100);
711			else nak(ENOSPACE);
712			goto abort;
713		}
714	} while (size == SEGSIZE);
715	write_behind(file, pf->f_convert);
716	(void) fclose(file);            /* close data file */
717
718	ap->th_opcode = htons((u_short)ACK);    /* send the "final" ack */
719	ap->th_block = htons((u_short)(block));
720	(void) send(peer, ackbuf, 4, 0);
721
722	signal(SIGALRM, justquit);      /* just quit on timeout */
723	alarm(rexmtval);
724	n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */
725	alarm(0);
726	if (n >= 4 &&                   /* if read some data */
727	    dp->th_opcode == DATA &&    /* and got a data block */
728	    block == dp->th_block) {	/* then my last ack was lost */
729		(void) send(peer, ackbuf, 4, 0);     /* resend final ack */
730	}
731abort:
732	return;
733}
734
735struct errmsg {
736	int	e_code;
737	const char	*e_msg;
738} errmsgs[] = {
739	{ EUNDEF,	"Undefined error code" },
740	{ ENOTFOUND,	"File not found" },
741	{ EACCESS,	"Access violation" },
742	{ ENOSPACE,	"Disk full or allocation exceeded" },
743	{ EBADOP,	"Illegal TFTP operation" },
744	{ EBADID,	"Unknown transfer ID" },
745	{ EEXISTS,	"File already exists" },
746	{ ENOUSER,	"No such user" },
747	{ EOPTNEG,	"Option negotiation" },
748	{ -1,		0 }
749};
750
751static const char *
752errtomsg(int error)
753{
754	static char ebuf[20];
755	struct errmsg *pe;
756	if (error == 0)
757		return "success";
758	for (pe = errmsgs; pe->e_code >= 0; pe++)
759		if (pe->e_code == error)
760			return pe->e_msg;
761	snprintf(ebuf, sizeof(buf), "error %d", error);
762	return ebuf;
763}
764
765/*
766 * Send a nak packet (error message).
767 * Error code passed in is one of the
768 * standard TFTP codes, or a UNIX errno
769 * offset by 100.
770 */
771static void
772nak(int error)
773{
774	struct tftphdr *tp;
775	int length;
776	struct errmsg *pe;
777
778	tp = (struct tftphdr *)buf;
779	tp->th_opcode = htons((u_short)ERROR);
780	tp->th_code = htons((u_short)error);
781	for (pe = errmsgs; pe->e_code >= 0; pe++)
782		if (pe->e_code == error)
783			break;
784	if (pe->e_code < 0) {
785		pe->e_msg = strerror(error - 100);
786		tp->th_code = EUNDEF;   /* set 'undef' errorcode */
787	}
788	strcpy(tp->th_msg, pe->e_msg);
789	length = strlen(pe->e_msg);
790	tp->th_msg[length] = '\0';
791	length += 5;
792	if (send(peer, buf, length, 0) != length)
793		syslog(LOG_ERR, "nak: %m");
794}
795
796/* translate IPv4 mapped IPv6 address to IPv4 address */
797static void
798unmappedaddr(struct sockaddr_in6 *sin6)
799{
800	struct sockaddr_in *sin4;
801	u_int32_t addr;
802	int port;
803
804	if (sin6->sin6_family != AF_INET6 ||
805	    !IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr))
806		return;
807	sin4 = (struct sockaddr_in *)sin6;
808	addr = *(u_int32_t *)&sin6->sin6_addr.s6_addr[12];
809	port = sin6->sin6_port;
810	memset(sin4, 0, sizeof(struct sockaddr_in));
811	sin4->sin_addr.s_addr = addr;
812	sin4->sin_port = port;
813	sin4->sin_family = AF_INET;
814	sin4->sin_len = sizeof(struct sockaddr_in);
815}
816
817/*
818 * Send an oack packet (option acknowledgement).
819 */
820static void
821oack(void)
822{
823	struct tftphdr *tp, *ap;
824	int size, i, n;
825	char *bp;
826
827	tp = (struct tftphdr *)buf;
828	bp = buf + 2;
829	size = sizeof(buf) - 2;
830	tp->th_opcode = htons((u_short)OACK);
831	for (i = 0; options[i].o_type != NULL; i++) {
832		if (options[i].o_request) {
833			n = snprintf(bp, size, "%s%c%d", options[i].o_type,
834				     0, options[i].o_reply);
835			bp += n+1;
836			size -= n+1;
837			if (size < 0) {
838				syslog(LOG_ERR, "oack: buffer overflow");
839				exit(1);
840			}
841		}
842	}
843	size = bp - buf;
844	ap = (struct tftphdr *)ackbuf;
845	signal(SIGALRM, timer);
846	timeouts = 0;
847
848	(void)setjmp(timeoutbuf);
849	if (send(peer, buf, size, 0) != size) {
850		syslog(LOG_INFO, "oack: %m");
851		exit(1);
852	}
853
854	for (;;) {
855		alarm(rexmtval);
856		n = recv(peer, ackbuf, sizeof (ackbuf), 0);
857		alarm(0);
858		if (n < 0) {
859			syslog(LOG_ERR, "recv: %m");
860			exit(1);
861		}
862		ap->th_opcode = ntohs((u_short)ap->th_opcode);
863		ap->th_block = ntohs((u_short)ap->th_block);
864		if (ap->th_opcode == ERROR)
865			exit(1);
866		if (ap->th_opcode == ACK && ap->th_block == 0)
867			break;
868	}
869}
870