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source: trunk/third/sendmail/src/domain.c @ 12554

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Revision 12554, 20.2 KB checked in by danw, 26 years ago (diff)
This commit was generated by cvs2svn to compensate for changes in r12553, which included commits to RCS files with non-trunk default branches.

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1	/*
2	* Copyright (c) 1998 Sendmail, Inc. All rights reserved.
3	* Copyright (c) 1986, 1995-1997 Eric P. Allman. All rights reserved.
4	* Copyright (c) 1988, 1993
5	* The Regents of the University of California. All rights reserved.
6	*
7	* By using this file, you agree to the terms and conditions set
8	* forth in the LICENSE file which can be found at the top level of
9	* the sendmail distribution.
10	*
11	*/
12
13	#include "sendmail.h"
14
15	#ifndef lint
16	#if NAMED_BIND
17	static char sccsid[] = "@(#)domain.c 8.81 (Berkeley) 1/21/1999 (with name server)";
18	#else
19	static char sccsid[] = "@(#)domain.c 8.81 (Berkeley) 1/21/1999 (without name server)";
20	#endif
21	#endif /* not lint */
22
23	#if NAMED_BIND
24
25	#include <errno.h>
26	#include <resolv.h>
27	#include <arpa/inet.h>
28
29	/*
30	** The standard udp packet size PACKETSZ (512) is not sufficient for some
31	** nameserver answers containing very many resource records. The resolver
32	** may switch to tcp and retry if it detects udp packet overflow.
33	** Also note that the resolver routines res_query and res_search return
34	** the size of the untruncated answer in case the supplied answer buffer
35	** it not big enough to accommodate the entire answer.
36	*/
37
38	#ifndef MAXPACKET
39	# define MAXPACKET 8192 /* max packet size used internally by BIND */
40	#endif
41
42	typedef union
43	{
44	HEADER qb1;
45	u_char qb2[MAXPACKET];
46	} querybuf;
47
48	#ifndef MXHOSTBUFSIZE
49	# define MXHOSTBUFSIZE (128 * MAXMXHOSTS)
50	#endif
51
52	static char MXHostBuf[MXHOSTBUFSIZE];
53
54	#ifndef MAXDNSRCH
55	# define MAXDNSRCH 6 /* number of possible domains to search */
56	#endif
57
58	#ifndef MAX
59	# define MAX(a, b) ((a) > (b) ? (a) : (b))
60	#endif
61
62	#ifndef NO_DATA
63	# define NO_DATA NO_ADDRESS
64	#endif
65
66	#ifndef HFIXEDSZ
67	# define HFIXEDSZ 12 /* sizeof(HEADER) */
68	#endif
69
70	#define MAXCNAMEDEPTH 10 /* maximum depth of CNAME recursion */
71
72	#if defined(__RES) && (__RES >= 19940415)
73	# define RES_UNC_T char *
74	#else
75	# define RES_UNC_T u_char *
76	#endif
77	/*
78	** GETMXRR -- get MX resource records for a domain
79	**
80	** Parameters:
81	** host -- the name of the host to MX.
82	** mxhosts -- a pointer to a return buffer of MX records.
83	** droplocalhost -- If TRUE, all MX records less preferred
84	** than the local host (as determined by $=w) will
85	** be discarded.
86	** rcode -- a pointer to an EX_ status code.
87	**
88	** Returns:
89	** The number of MX records found.
90	** -1 if there is an internal failure.
91	** If no MX records are found, mxhosts[0] is set to host
92	** and 1 is returned.
93	*/
94
95	int
96	getmxrr(host, mxhosts, droplocalhost, rcode)
97	char *host;
98	char **mxhosts;
99	bool droplocalhost;
100	int *rcode;
101	{
102	register u_char eom, cp;
103	register int i, j, n;
104	int nmx = 0;
105	register char *bp;
106	HEADER *hp;
107	querybuf answer;
108	int ancount, qdcount, buflen;
109	bool seenlocal = FALSE;
110	u_short pref, type;
111	u_short localpref = 256;
112	char *fallbackMX = FallBackMX;
113	bool trycanon = FALSE;
114	int (*resfunc)();
115	extern int res_query(), res_search();
116	u_short prefer[MAXMXHOSTS];
117	int weight[MAXMXHOSTS];
118	extern int mxrand __P((char *));
119
120	if (tTd(8, 2))
121	printf("getmxrr(%s, droplocalhost=%d)\n", host, droplocalhost);
122
123	if (fallbackMX != NULL && droplocalhost &&
124	wordinclass(fallbackMX, 'w'))
125	{
126	/* don't use fallback for this pass */
127	fallbackMX = NULL;
128	}
129
130	*rcode = EX_OK;
131
132	/* efficiency hack -- numeric or non-MX lookups */
133	if (host[0] == '[')
134	goto punt;
135
136	/*
137	** If we don't have MX records in our host switch, don't
138	** try for MX records. Note that this really isn't "right",
139	** since we might be set up to try NIS first and then DNS;
140	** if the host is found in NIS we really shouldn't be doing
141	** MX lookups. However, that should be a degenerate case.
142	*/
143
144	if (!UseNameServer)
145	goto punt;
146	if (HasWildcardMX && ConfigLevel >= 6)
147	resfunc = res_query;
148	else
149	resfunc = res_search;
150
151	errno = 0;
152	n = (resfunc)(host, C_IN, T_MX, (u_char ) &answer, sizeof(answer));
153	if (n < 0)
154	{
155	if (tTd(8, 1))
156	printf("getmxrr: res_search(%s) failed (errno=%d, h_errno=%d)\n",
157	(host == NULL) ? "<NULL>" : host, errno, h_errno);
158	switch (h_errno)
159	{
160	case NO_DATA:
161	trycanon = TRUE;
162	/* fall through */
163
164	case NO_RECOVERY:
165	/* no MX data on this host */
166	goto punt;
167
168	case HOST_NOT_FOUND:
169	#if BROKEN_RES_SEARCH
170	case 0: /* Ultrix resolver retns failure w/ h_errno=0 */
171	#endif
172	/* host doesn't exist in DNS; might be in /etc/hosts */
173	trycanon = TRUE;
174	*rcode = EX_NOHOST;
175	goto punt;
176
177	case TRY_AGAIN:
178	case -1:
179	/* couldn't connect to the name server */
180	if (fallbackMX != NULL)
181	{
182	/* name server is hosed -- push to fallback */
183	mxhosts[nmx++] = fallbackMX;
184	return nmx;
185	}
186	/* it might come up later; better queue it up */
187	*rcode = EX_TEMPFAIL;
188	break;
189
190	default:
191	syserr("getmxrr: res_search (%s) failed with impossible h_errno (%d)\n",
192	host, h_errno);
193	*rcode = EX_OSERR;
194	break;
195	}
196
197	/* irreconcilable differences */
198	return (-1);
199	}
200
201	/* avoid problems after truncation in tcp packets */
202	if (n > sizeof(answer))
203	n = sizeof(answer);
204
205	/* find first satisfactory answer */
206	hp = (HEADER *)&answer;
207	cp = (u_char *)&answer + HFIXEDSZ;
208	eom = (u_char *)&answer + n;
209	for (qdcount = ntohs(hp->qdcount); qdcount--; cp += n + QFIXEDSZ)
210	if ((n = dn_skipname(cp, eom)) < 0)
211	goto punt;
212	buflen = sizeof(MXHostBuf) - 1;
213	bp = MXHostBuf;
214	ancount = ntohs(hp->ancount);
215	while (--ancount >= 0 && cp < eom && nmx < MAXMXHOSTS - 1)
216	{
217	if ((n = dn_expand((u_char *)&answer,
218	eom, cp, (RES_UNC_T) bp, buflen)) < 0)
219	break;
220	cp += n;
221	GETSHORT(type, cp);
222	cp += INT16SZ + INT32SZ;
223	GETSHORT(n, cp);
224	if (type != T_MX)
225	{
226	if (tTd(8, 8) \|\| _res.options & RES_DEBUG)
227	printf("unexpected answer type %d, size %d\n",
228	type, n);
229	cp += n;
230	continue;
231	}
232	GETSHORT(pref, cp);
233	if ((n = dn_expand((u_char *)&answer, eom, cp,
234	(RES_UNC_T) bp, buflen)) < 0)
235	break;
236	cp += n;
237	if (wordinclass(bp, 'w'))
238	{
239	if (tTd(8, 3))
240	printf("found localhost (%s) in MX list, pref=%d\n",
241	bp, pref);
242	if (droplocalhost)
243	{
244	if (!seenlocal \|\| pref < localpref)
245	localpref = pref;
246	seenlocal = TRUE;
247	continue;
248	}
249	weight[nmx] = 0;
250	}
251	else
252	weight[nmx] = mxrand(bp);
253	prefer[nmx] = pref;
254	mxhosts[nmx++] = bp;
255	n = strlen(bp);
256	bp += n;
257	if (bp[-1] != '.')
258	{
259	*bp++ = '.';
260	n++;
261	}
262	*bp++ = '\0';
263	buflen -= n + 1;
264	}
265
266	/* sort the records */
267	for (i = 0; i < nmx; i++)
268	{
269	for (j = i + 1; j < nmx; j++)
270	{
271	if (prefer[i] > prefer[j] \|\|
272	(prefer[i] == prefer[j] && weight[i] > weight[j]))
273	{
274	register int temp;
275	register char *temp1;
276
277	temp = prefer[i];
278	prefer[i] = prefer[j];
279	prefer[j] = temp;
280	temp1 = mxhosts[i];
281	mxhosts[i] = mxhosts[j];
282	mxhosts[j] = temp1;
283	temp = weight[i];
284	weight[i] = weight[j];
285	weight[j] = temp;
286	}
287	}
288	if (seenlocal && prefer[i] >= localpref)
289	{
290	/* truncate higher preference part of list */
291	nmx = i;
292	}
293	}
294
295	/* delete duplicates from list (yes, some bozos have duplicates) */
296	for (i = 0; i < nmx - 1; )
297	{
298	if (strcasecmp(mxhosts[i], mxhosts[i + 1]) != 0)
299	i++;
300	else
301	{
302	/* compress out duplicate */
303	for (j = i + 1; j < nmx; j++)
304	mxhosts[j] = mxhosts[j + 1];
305	nmx--;
306	}
307	}
308
309	if (nmx == 0)
310	{
311	punt:
312	if (seenlocal &&
313	(!TryNullMXList \|\| sm_gethostbyname(host) == NULL))
314	{
315	/*
316	** If we have deleted all MX entries, this is
317	** an error -- we should NEVER send to a host that
318	** has an MX, and this should have been caught
319	** earlier in the config file.
320	**
321	** Some sites prefer to go ahead and try the
322	** A record anyway; that case is handled by
323	** setting TryNullMXList. I believe this is a
324	** bad idea, but it's up to you....
325	*/
326
327	*rcode = EX_CONFIG;
328	syserr("MX list for %s points back to %s",
329	host, MyHostName);
330	return -1;
331	}
332	if (strlen(host) >= (SIZE_T) sizeof MXHostBuf)
333	{
334	*rcode = EX_CONFIG;
335	syserr("Host name %s too long",
336	shortenstring(host, MAXSHORTSTR));
337	return -1;
338	}
339	snprintf(MXHostBuf, sizeof MXHostBuf, "%s", host);
340	mxhosts[0] = MXHostBuf;
341	if (host[0] == '[')
342	{
343	register char *p;
344
345	/* this may be an MX suppression-style address */
346	p = strchr(MXHostBuf, ']');
347	if (p != NULL)
348	{
349	*p = '\0';
350	if (inet_addr(&MXHostBuf[1]) != INADDR_NONE)
351	{
352	nmx++;
353	*p = ']';
354	}
355	else
356	{
357	trycanon = TRUE;
358	mxhosts[0]++;
359	}
360	}
361	}
362	if (trycanon &&
363	getcanonname(mxhosts[0], sizeof MXHostBuf - 2, FALSE))
364	{
365	bp = &MXHostBuf[strlen(MXHostBuf)];
366	if (bp[-1] != '.')
367	{
368	*bp++ = '.';
369	*bp = '\0';
370	}
371	nmx = 1;
372	}
373	}
374
375	/* if we have a default lowest preference, include that */
376	if (fallbackMX != NULL && !seenlocal)
377	mxhosts[nmx++] = fallbackMX;
378
379	return (nmx);
380	}
381	/*
382	** MXRAND -- create a randomizer for equal MX preferences
383	**
384	** If two MX hosts have equal preferences we want to randomize
385	** the selection. But in order for signatures to be the same,
386	** we need to randomize the same way each time. This function
387	** computes a pseudo-random hash function from the host name.
388	**
389	** Parameters:
390	** host -- the name of the host.
391	**
392	** Returns:
393	** A random but repeatable value based on the host name.
394	**
395	** Side Effects:
396	** none.
397	*/
398
399	int
400	mxrand(host)
401	register char *host;
402	{
403	int hfunc;
404	static unsigned int seed;
405
406	if (seed == 0)
407	{
408	seed = (int) curtime() & 0xffff;
409	if (seed == 0)
410	seed++;
411	}
412
413	if (tTd(17, 9))
414	printf("mxrand(%s)", host);
415
416	hfunc = seed;
417	while (*host != '\0')
418	{
419	int c = *host++;
420
421	if (isascii(c) && isupper(c))
422	c = tolower(c);
423	hfunc = ((hfunc << 1) ^ c) % 2003;
424	}
425
426	hfunc &= 0xff;
427	hfunc++;
428
429	if (tTd(17, 9))
430	printf(" = %d\n", hfunc);
431	return hfunc;
432	}
433	/*
434	** BESTMX -- find the best MX for a name
435	**
436	** This is really a hack, but I don't see any obvious way
437	** to generalize it at the moment.
438	*/
439
440	/* ARGSUSED3 */
441	char *
442	bestmx_map_lookup(map, name, av, statp)
443	MAP *map;
444	char *name;
445	char **av;
446	int *statp;
447	{
448	int nmx;
449	int saveopts = _res.options;
450	int i, len = 0;
451	char *p;
452	char *mxhosts[MAXMXHOSTS + 1];
453	char buf[PSBUFSIZE / 2];
454
455	_res.options &= ~(RES_DNSRCH\|RES_DEFNAMES);
456	nmx = getmxrr(name, mxhosts, FALSE, statp);
457	_res.options = saveopts;
458	if (nmx <= 0)
459	return NULL;
460	if (bitset(MF_MATCHONLY, map->map_mflags))
461	return map_rewrite(map, name, strlen(name), NULL);
462	if ((map->map_coldelim == '\0') \|\| (nmx == 1))
463	return map_rewrite(map, mxhosts[0], strlen(mxhosts[0]), av);
464
465	/*
466	** We were given a -z flag (return all MXs) and there are multiple
467	** ones. We need to build them all into a list.
468	*/
469	p = buf;
470	for (i = 0; i < nmx; i++)
471	{
472	int slen;
473
474	if (strchr(mxhosts[i], map->map_coldelim) != NULL)
475	{
476	syserr("bestmx_map_lookup: MX host %.64s includes map delimiter character 0x%02X",
477	mxhosts[i], map->map_coldelim);
478	return NULL;
479	}
480	slen = strlen(mxhosts[i]);
481	if (len + slen + 2 > sizeof buf)
482	break;
483	if (i > 0)
484	{
485	*p++ = map->map_coldelim;
486	len++;
487	}
488	strcpy(p, mxhosts[i]);
489	p += slen;
490	len += slen;
491	}
492	return map_rewrite(map, buf, len, av);
493	}
494	/*
495	** DNS_GETCANONNAME -- get the canonical name for named host using DNS
496	**
497	** This algorithm tries to be smart about wildcard MX records.
498	** This is hard to do because DNS doesn't tell is if we matched
499	** against a wildcard or a specific MX.
500	**
501	** We always prefer A & CNAME records, since these are presumed
502	** to be specific.
503	**
504	** If we match an MX in one pass and lose it in the next, we use
505	** the old one. For example, consider an MX matching *.FOO.BAR.COM.
506	** A hostname bletch.foo.bar.com will match against this MX, but
507	** will stop matching when we try bletch.bar.com -- so we know
508	** that bletch.foo.bar.com must have been right. This fails if
509	** there was also an MX record matching *.BAR.COM, but there are
510	** some things that just can't be fixed.
511	**
512	** Parameters:
513	** host -- a buffer containing the name of the host.
514	** This is a value-result parameter.
515	** hbsize -- the size of the host buffer.
516	** trymx -- if set, try MX records as well as A and CNAME.
517	** statp -- pointer to place to store status.
518	**
519	** Returns:
520	** TRUE -- if the host matched.
521	** FALSE -- otherwise.
522	*/
523
524	bool
525	dns_getcanonname(host, hbsize, trymx, statp)
526	char *host;
527	int hbsize;
528	bool trymx;
529	int *statp;
530	{
531	register u_char eom, ap;
532	register char *cp;
533	register int n;
534	HEADER *hp;
535	querybuf answer;
536	int ancount, qdcount;
537	int ret;
538	char **domain;
539	int type;
540	char **dp;
541	char *mxmatch;
542	bool amatch;
543	bool gotmx = FALSE;
544	int qtype;
545	int loopcnt;
546	char *xp;
547	char nbuf[MAX(MAXPACKET, MAXDNAME*2+2)];
548	char *searchlist[MAXDNSRCH+2];
549	extern char gethostalias __P((char ));
550
551	if (tTd(8, 2))
552	printf("dns_getcanonname(%s, trymx=%d)\n", host, trymx);
553
554	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
555	{
556	*statp = EX_UNAVAILABLE;
557	return FALSE;
558	}
559
560	/*
561	** Initialize domain search list. If there is at least one
562	** dot in the name, search the unmodified name first so we
563	** find "vse.CS" in Czechoslovakia instead of in the local
564	** domain (e.g., vse.CS.Berkeley.EDU).
565	**
566	** Older versions of the resolver could create this
567	** list by tearing apart the host name.
568	*/
569
570	loopcnt = 0;
571	cnameloop:
572	/* Check for dots in the name */
573	for (cp = host, n = 0; *cp != '\0'; cp++)
574	if (*cp == '.')
575	n++;
576
577	/*
578	** If this is a simple name, determine whether it matches an
579	** alias in the file defined by the environment variable HOSTALIASES.
580	*/
581	if (n == 0 && (xp = gethostalias(host)) != NULL)
582	{
583	if (loopcnt++ > MAXCNAMEDEPTH)
584	{
585	syserr("loop in ${HOSTALIASES} file");
586	}
587	else
588	{
589	strncpy(host, xp, hbsize);
590	host[hbsize - 1] = '\0';
591	goto cnameloop;
592	}
593	}
594
595	/*
596	** Build the search list.
597	** If there is at least one dot in name, start with a null
598	** domain to search the unmodified name first.
599	** If name does not end with a dot and search up local domain
600	** tree desired, append each local domain component to the
601	** search list; if name contains no dots and default domain
602	** name is desired, append default domain name to search list;
603	** else if name ends in a dot, remove that dot.
604	*/
605
606	dp = searchlist;
607	if (n > 0)
608	*dp++ = "";
609	if (n >= 0 && *--cp != '.' && bitset(RES_DNSRCH, _res.options))
610	{
611	for (domain = _res.dnsrch; *domain != NULL; )
612	dp++ = domain++;
613	}
614	else if (n == 0 && bitset(RES_DEFNAMES, _res.options))
615	{
616	*dp++ = _res.defdname;
617	}
618	else if (*cp == '.')
619	{
620	*cp = '\0';
621	}
622	*dp = NULL;
623
624	/*
625	** Now loop through the search list, appending each domain in turn
626	** name and searching for a match.
627	*/
628
629	mxmatch = NULL;
630	qtype = T_ANY;
631
632	for (dp = searchlist; *dp != NULL; )
633	{
634	if (qtype == T_ANY)
635	gotmx = FALSE;
636	if (tTd(8, 5))
637	printf("dns_getcanonname: trying %s.%s (%s)\n",
638	host, *dp,
639	qtype == T_ANY ? "ANY" : qtype == T_A ? "A" :
640	qtype == T_MX ? "MX" : "???");
641	ret = res_querydomain(host, *dp, C_IN, qtype,
642	answer.qb2, sizeof(answer.qb2));
643	if (ret <= 0)
644	{
645	if (tTd(8, 7))
646	printf("\tNO: errno=%d, h_errno=%d\n",
647	errno, h_errno);
648
649	if (errno == ECONNREFUSED \|\| h_errno == TRY_AGAIN)
650	{
651	/* the name server seems to be down */
652	h_errno = TRY_AGAIN;
653	*statp = EX_TEMPFAIL;
654	return FALSE;
655	}
656
657	if (h_errno != HOST_NOT_FOUND)
658	{
659	/* might have another type of interest */
660	if (qtype == T_ANY)
661	{
662	qtype = T_A;
663	continue;
664	}
665	else if (qtype == T_A && !gotmx && (trymx \|\| **dp == '\0'))
666	{
667	qtype = T_MX;
668	continue;
669	}
670	}
671
672	/* definite no -- try the next domain */
673	dp++;
674	qtype = T_ANY;
675	continue;
676	}
677	else if (tTd(8, 7))
678	printf("\tYES\n");
679
680	/* avoid problems after truncation in tcp packets */
681	if (ret > sizeof(answer))
682	ret = sizeof(answer);
683
684	/*
685	** Appear to have a match. Confirm it by searching for A or
686	** CNAME records. If we don't have a local domain
687	** wild card MX record, we will accept MX as well.
688	*/
689
690	hp = (HEADER *) &answer;
691	ap = (u_char *) &answer + HFIXEDSZ;
692	eom = (u_char *) &answer + ret;
693
694	/* skip question part of response -- we know what we asked */
695	for (qdcount = ntohs(hp->qdcount); qdcount--; ap += ret + QFIXEDSZ)
696	{
697	if ((ret = dn_skipname(ap, eom)) < 0)
698	{
699	if (tTd(8, 20))
700	printf("qdcount failure (%d)\n",
701	ntohs(hp->qdcount));
702	*statp = EX_SOFTWARE;
703	return FALSE; /* ???XXX??? */
704	}
705	}
706
707	amatch = FALSE;
708	for (ancount = ntohs(hp->ancount); --ancount >= 0 && ap < eom;
709	ap += n)
710	{
711	n = dn_expand((u_char *) &answer, eom, ap,
712	(RES_UNC_T) nbuf, sizeof nbuf);
713	if (n < 0)
714	break;
715	ap += n;
716	GETSHORT(type, ap);
717	ap += INT16SZ + INT32SZ;
718	GETSHORT(n, ap);
719	switch (type)
720	{
721	case T_MX:
722	gotmx = TRUE;
723	if (**dp != '\0' && HasWildcardMX)
724	{
725	/*
726	** If we are using MX matches and have
727	** not yet gotten one, save this one
728	** but keep searching for an A or
729	** CNAME match.
730	*/
731
732	if (trymx && mxmatch == NULL)
733	mxmatch = *dp;
734	continue;
735	}
736
737	/*
738	** If we did not append a domain name, this
739	** must have been a canonical name to start
740	** with. Even if we did append a domain name,
741	** in the absence of a wildcard MX this must
742	** still be a real MX match.
743	** Such MX matches are as good as an A match,
744	** fall through.
745	*/
746
747	case T_A:
748	/* Flag that a good match was found */
749	amatch = TRUE;
750
751	/* continue in case a CNAME also exists */
752	continue;
753
754	case T_CNAME:
755	if (DontExpandCnames)
756	{
757	/* got CNAME -- guaranteed canonical */
758	amatch = TRUE;
759	break;
760	}
761
762	if (loopcnt++ > MAXCNAMEDEPTH)
763	{
764	/XXX should notify postmaster XXX/
765	message("DNS failure: CNAME loop for %s",
766	host);
767	if (CurEnv->e_message == NULL)
768	{
769	char ebuf[MAXLINE];
770
771	snprintf(ebuf, sizeof ebuf,
772	"Deferred: DNS failure: CNAME loop for %.100s",
773	host);
774	CurEnv->e_message = newstr(ebuf);
775	}
776	h_errno = NO_RECOVERY;
777	*statp = EX_CONFIG;
778	return FALSE;
779	}
780
781	/* value points at name */
782	if ((ret = dn_expand((u_char *)&answer,
783	eom, ap, (RES_UNC_T) nbuf, sizeof(nbuf))) < 0)
784	break;
785	(void)strncpy(host, nbuf, hbsize); /* XXX */
786	host[hbsize - 1] = '\0';
787
788	/*
789	** RFC 1034 section 3.6 specifies that CNAME
790	** should point at the canonical name -- but
791	** urges software to try again anyway.
792	*/
793
794	goto cnameloop;
795
796	default:
797	/* not a record of interest */
798	continue;
799	}
800	}
801
802	if (amatch)
803	{
804	/*
805	** Got a good match -- either an A, CNAME, or an
806	** exact MX record. Save it and get out of here.
807	*/
808
809	mxmatch = *dp;
810	break;
811	}
812
813	/*
814	** Nothing definitive yet.
815	** If this was a T_ANY query, we don't really know what
816	** was returned -- it might have been a T_NS,
817	** for example. Try T_A to be more specific
818	** during the next pass.
819	** If this was a T_A query and we haven't yet found a MX
820	** match, try T_MX if allowed to do so.
821	** Otherwise, try the next domain.
822	*/
823
824	if (qtype == T_ANY)
825	qtype = T_A;
826	else if (qtype == T_A && !gotmx && (trymx \|\| **dp == '\0'))
827	qtype = T_MX;
828	else
829	{
830	qtype = T_ANY;
831	dp++;
832	}
833	}
834
835	/* if nothing was found, we are done */
836	if (mxmatch == NULL)
837	{
838	*statp = EX_NOHOST;
839	return FALSE;
840	}
841
842	/*
843	** Create canonical name and return.
844	** If saved domain name is null, name was already canonical.
845	** Otherwise append the saved domain name.
846	*/
847
848	(void) snprintf(nbuf, sizeof nbuf, "%.s%s%.s", MAXDNAME, host,
849	*mxmatch == '\0' ? "" : ".",
850	MAXDNAME, mxmatch);
851	strncpy(host, nbuf, hbsize);
852	host[hbsize - 1] = '\0';
853	if (tTd(8, 5))
854	printf("dns_getcanonname: %s\n", host);
855	*statp = EX_OK;
856	return TRUE;
857	}
858
859
860
861	char *
862	gethostalias(host)
863	char *host;
864	{
865	char *fname;
866	FILE *fp;
867	register char *p = NULL;
868	int sff = SFF_REGONLY;
869	char buf[MAXLINE];
870	static char hbuf[MAXDNAME];
871
872	if (DontLockReadFiles)
873	sff \|= SFF_NOLOCK;
874	fname = getenv("HOSTALIASES");
875	if (fname == NULL \|\|
876	(fp = safefopen(fname, O_RDONLY, 0, sff)) == NULL)
877	return NULL;
878	while (fgets(buf, sizeof buf, fp) != NULL)
879	{
880	for (p = buf; p != '\0' && !(isascii(p) && isspace(p)); p++)
881	continue;
882	if (*p == 0)
883	{
884	/* syntax error */
885	continue;
886	}
887	*p++ = '\0';
888	if (strcasecmp(buf, host) == 0)
889	break;
890	}
891
892	if (feof(fp))
893	{
894	/* no match */
895	fclose(fp);
896	return NULL;
897	}
898	fclose(fp);
899
900	/* got a match; extract the equivalent name */
901	while (p != '\0' && isascii(p) && isspace(*p))
902	p++;
903	host = p;
904	while (p != '\0' && !(isascii(p) && isspace(*p)))
905	p++;
906	*p = '\0';
907	strncpy(hbuf, host, sizeof hbuf - 1);
908	hbuf[sizeof hbuf - 1] = '\0';
909	return hbuf;
910	}
911
912	#endif /* NAMED_BIND */

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