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source: rtems/cpukit/libnetworking/libc/res_send.c @ 09fdb5e8

4.104.114.84.95

Last change on this file since 09fdb5e8 was 09fdb5e8, checked in by Ralf Corsepius <ralf.corsepius@…>, on 03/30/07 at 05:15:58
Eliminate SCCS, LINT. Add HAVE_CONFIG_H.
Property mode set to `100644`
File size: 22.9 KB

Line
1	/*
2	* Copyright (c) 1985, 1989, 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	/*
35	* Portions Copyright (c) 1993 by Digital Equipment Corporation.
36	*
37	* Permission to use, copy, modify, and distribute this software for any
38	* purpose with or without fee is hereby granted, provided that the above
39	* copyright notice and this permission notice appear in all copies, and that
40	* the name of Digital Equipment Corporation not be used in advertising or
41	* publicity pertaining to distribution of the document or software without
42	* specific, written prior permission.
43	*
44	* THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
45	* WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
46	* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT
47	* CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
48	* DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
49	* PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
50	* ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
51	* SOFTWARE.
52	*/
53
54	/*
55	* Portions Copyright (c) 1996 by Internet Software Consortium.
56	*
57	* Permission to use, copy, modify, and distribute this software for any
58	* purpose with or without fee is hereby granted, provided that the above
59	* copyright notice and this permission notice appear in all copies.
60	*
61	* THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
62	* ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
63	* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
64	* CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
65	* DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
66	* PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
67	* ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
68	* SOFTWARE.
69	*/
70
71	#if HAVE_CONFIG_H
72	#include "config.h"
73	#endif
74
75	/*
76	* Send query to name server and wait for reply.
77	*/
78
79	#include <sys/types.h>
80	#include <sys/param.h>
81	#include <sys/time.h>
82	#include <sys/socket.h>
83	#include <sys/uio.h>
84
85	#include <netinet/in.h>
86	#include <arpa/nameser.h>
87	#include <arpa/inet.h>
88
89	#include <errno.h>
90	#include <netdb.h>
91	#include <resolv.h>
92	#include <stdio.h>
93	#include <stdlib.h>
94	#include <string.h>
95	#include <unistd.h>
96	#if !defined(__rtems__)
97	#include <poll.h>
98	#endif
99
100	#include "res_config.h"
101
102	#if !defined(__rtems__)
103
104	#ifdef NOPOLL /* libc_r doesn't wrap poll yet() */
105	static int use_poll = 0;
106	#else
107	static int use_poll = 1; /* adapt to poll() syscall availability */
108	/* 0 = not present, 1 = try it, 2 = exists */
109	#endif
110	#endif
111
112	static int s = -1; /* socket used for communications */
113	static int connected = 0; /* is the socket connected */
114	static int vc = 0; /* is the socket a virtual circuit? */
115	static res_send_qhook Qhook = NULL;
116	static res_send_rhook Rhook = NULL;
117
118
119	#define CAN_RECONNECT 1
120
121	#ifndef DEBUG
122	# define Dprint(cond, args) /empty/
123	# define DprintQ(cond, args, query, size) /empty/
124	# define Aerror(file, string, error, address) /empty/
125	# define Perror(file, string, error) /empty/
126	#else
127	# define Dprint(cond, args) if (cond) {fprintf args;} else {}
128	# define DprintQ(cond, args, query, size) if (cond) {\
129	fprintf args;\
130	__fp_nquery(query, size, stdout);\
131	} else {}
132	static void
133	Aerror(file, string, error, address)
134	FILE *file;
135	char *string;
136	int error;
137	struct sockaddr_in address;
138	{
139	int save = errno;
140
141	if (_res.options & RES_DEBUG) {
142	fprintf(file, "res_send: %s ([%s].%u): %s\n",
143	string,
144	inet_ntoa(address.sin_addr),
145	ntohs(address.sin_port),
146	strerror(error));
147	}
148	errno = save;
149	}
150	static void
151	Perror(file, string, error)
152	FILE *file;
153	char *string;
154	int error;
155	{
156	int save = errno;
157
158	if (_res.options & RES_DEBUG) {
159	fprintf(file, "res_send: %s: %s\n",
160	string, strerror(error));
161	}
162	errno = save;
163	}
164	#endif
165
166	void
167	res_send_setqhook(hook)
168	res_send_qhook hook;
169	{
170
171	Qhook = hook;
172	}
173
174	void
175	res_send_setrhook(hook)
176	res_send_rhook hook;
177	{
178
179	Rhook = hook;
180	}
181
182	/* int
183	* res_isourserver(ina)
184	* looks up "ina" in _res.ns_addr_list[]
185	* returns:
186	* 0 : not found
187	* >0 : found
188	* author:
189	* paul vixie, 29may94
190	*/
191	int
192	res_isourserver(inp)
193	const struct sockaddr_in *inp;
194	{
195	struct sockaddr_in ina;
196	int ns, ret;
197
198	ina = *inp;
199	ret = 0;
200	for (ns = 0; ns < _res.nscount; ns++) {
201	const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
202
203	if (srv->sin_family == ina.sin_family &&
204	srv->sin_port == ina.sin_port &&
205	(srv->sin_addr.s_addr == INADDR_ANY \|\|
206	srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
207	ret++;
208	break;
209	}
210	}
211	return (ret);
212	}
213
214	/* int
215	* res_nameinquery(name, type, class, buf, eom)
216	* look for (name,type,class) in the query section of packet (buf,eom)
217	* requires:
218	* buf + HFIXEDSZ <= eom
219	* returns:
220	* -1 : format error
221	* 0 : not found
222	* >0 : found
223	* author:
224	* paul vixie, 29may94
225	*/
226	int
227	res_nameinquery(name, type, class, buf, eom)
228	const char *name;
229	int type, class;
230	const u_char buf, eom;
231	{
232	const u_char *cp = buf + HFIXEDSZ;
233	int qdcount = ntohs(((HEADER*)buf)->qdcount);
234
235	while (qdcount-- > 0) {
236	char tname[MAXDNAME+1];
237	int n, ttype, tclass;
238
239	n = dn_expand(buf, eom, cp, tname, sizeof tname);
240	if (n < 0)
241	return (-1);
242	cp += n;
243	if (cp + 2 * INT16SZ > eom)
244	return (-1);
245	ttype = ns_get16(cp); cp += INT16SZ;
246	tclass = ns_get16(cp); cp += INT16SZ;
247	if (ttype == type &&
248	tclass == class &&
249	strcasecmp(tname, name) == 0)
250	return (1);
251	}
252	return (0);
253	}
254
255	/* int
256	* res_queriesmatch(buf1, eom1, buf2, eom2)
257	* is there a 1:1 mapping of (name,type,class)
258	* in (buf1,eom1) and (buf2,eom2)?
259	* returns:
260	* -1 : format error
261	* 0 : not a 1:1 mapping
262	* >0 : is a 1:1 mapping
263	* author:
264	* paul vixie, 29may94
265	*/
266	int
267	res_queriesmatch(buf1, eom1, buf2, eom2)
268	const u_char buf1, eom1;
269	const u_char buf2, eom2;
270	{
271	const u_char *cp = buf1 + HFIXEDSZ;
272	int qdcount = ntohs(((HEADER*)buf1)->qdcount);
273
274	if (buf1 + HFIXEDSZ > eom1 \|\| buf2 + HFIXEDSZ > eom2)
275	return (-1);
276
277	/*
278	* Only header section present in replies to
279	* dynamic update packets.
280	*/
281	if ( (((HEADER *)buf1)->opcode == ns_o_update) &&
282	(((HEADER *)buf2)->opcode == ns_o_update) )
283	return (1);
284
285	if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
286	return (0);
287	while (qdcount-- > 0) {
288	char tname[MAXDNAME+1];
289	int n, ttype, tclass;
290
291	n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
292	if (n < 0)
293	return (-1);
294	cp += n;
295	if (cp + 2 * INT16SZ > eom1)
296	return (-1);
297	ttype = ns_get16(cp); cp += INT16SZ;
298	tclass = ns_get16(cp); cp += INT16SZ;
299	if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
300	return (0);
301	}
302	return (1);
303	}
304
305	int
306	res_send(buf, buflen, ans, anssiz)
307	const u_char *buf;
308	int buflen;
309	u_char *ans;
310	int anssiz;
311	{
312	HEADER hp = (HEADER ) buf;
313	HEADER anhp = (HEADER ) ans;
314	int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns, n;
315	u_int badns; /* XXX NSMAX can't exceed #/bits in this variable */
316
317	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
318	/* errno should have been set by res_init() in this case. */
319	return (-1);
320	}
321	if (anssiz < HFIXEDSZ) {
322	errno = EINVAL;
323	return (-1);
324	}
325	DprintQ((_res.options & RES_DEBUG) \|\| (_res.pfcode & RES_PRF_QUERY),
326	(stdout, ";; res_send()\n"), buf, buflen);
327	v_circuit = (_res.options & RES_USEVC) \|\| buflen > PACKETSZ;
328	gotsomewhere = 0;
329	connreset = 0;
330	terrno = ETIMEDOUT;
331	badns = 0;
332
333	/*
334	* Send request, RETRY times, or until successful
335	*/
336	for (try = 0; try < _res.retry; try++) {
337	for (ns = 0; ns < _res.nscount; ns++) {
338	struct sockaddr_in *nsap = &_res.nsaddr_list[ns];
339	same_ns:
340	if (badns & (1 << ns)) {
341	res_close();
342	goto next_ns;
343	}
344
345	if (Qhook) {
346	int done = 0, loops = 0;
347
348	do {
349	res_sendhookact act;
350
351	act = (*Qhook)(&nsap, &buf, &buflen,
352	ans, anssiz, &resplen);
353	switch (act) {
354	case res_goahead:
355	done = 1;
356	break;
357	case res_nextns:
358	res_close();
359	goto next_ns;
360	case res_done:
361	return (resplen);
362	case res_modified:
363	/* give the hook another try */
364	if (++loops < 42) /doug adams/
365	break;
366	/FALLTHROUGH/
367	case res_error:
368	/FALLTHROUGH/
369	default:
370	return (-1);
371	}
372	} while (!done);
373	}
374
375	Dprint(_res.options & RES_DEBUG,
376	(stdout, ";; Querying server (# %d) address = %s\n",
377	ns + 1, inet_ntoa(nsap->sin_addr)));
378
379	if (v_circuit) {
380	int truncated;
381	#if !defined(__rtems__)
382	struct iovec iov[2];
383	#endif
384	u_short len;
385	u_char *cp;
386
387	/*
388	* Use virtual circuit;
389	* at most one attempt per server.
390	*/
391	try = _res.retry;
392	truncated = 0;
393	if (s < 0 \|\| !vc \|\| hp->opcode == ns_o_update) {
394	if (s >= 0)
395	res_close();
396
397	s = socket(PF_INET, SOCK_STREAM, 0);
398	if (s < 0) {
399	terrno = errno;
400	Perror(stderr, "socket(vc)", errno);
401	return (-1);
402	}
403	errno = 0;
404	if (connect(s, (struct sockaddr *)nsap,
405	sizeof *nsap) < 0) {
406	terrno = errno;
407	Aerror(stderr, "connect/vc",
408	errno, *nsap);
409	badns \|= (1 << ns);
410	res_close();
411	goto next_ns;
412	}
413	vc = 1;
414	}
415	/*
416	* Send length & message
417	*/
418	putshort((u_short)buflen, (u_char*)&len);
419	#if !defined(__rtems__)
420	iov[0].iov_base = (caddr_t)&len;
421	iov[0].iov_len = INT16SZ;
422	iov[1].iov_base = (caddr_t)buf;
423	iov[1].iov_len = buflen;
424	if (writev(s, iov, 2) != (INT16SZ + buflen)) {
425	#else
426	/*
427	* RTEMS doesn't have writev (yet)
428	*/
429	if ((write (s, &len, INT16SZ) != INT16SZ)
430	\|\| (write (s, buf, buflen) != buflen)) {
431	#endif
432	terrno = errno;
433	Perror(stderr, "write failed", errno);
434	badns \|= (1 << ns);
435	res_close();
436	goto next_ns;
437	}
438	/*
439	* Receive length & response
440	*/
441	read_len:
442	cp = ans;
443	len = INT16SZ;
444	while ((n = read(s, (char *)cp, (int)len)) > 0) {
445	cp += n;
446	if ((len -= n) <= 0)
447	break;
448	}
449	if (n <= 0) {
450	terrno = errno;
451	Perror(stderr, "read failed", errno);
452	res_close();
453	/*
454	* A long running process might get its TCP
455	* connection reset if the remote server was
456	* restarted. Requery the server instead of
457	* trying a new one. When there is only one
458	* server, this means that a query might work
459	* instead of failing. We only allow one reset
460	* per query to prevent looping.
461	*/
462	if (terrno == ECONNRESET && !connreset) {
463	connreset = 1;
464	res_close();
465	goto same_ns;
466	}
467	res_close();
468	goto next_ns;
469	}
470	resplen = ns_get16(ans);
471	if (resplen > anssiz) {
472	Dprint(_res.options & RES_DEBUG,
473	(stdout, ";; response truncated\n")
474	);
475	truncated = 1;
476	len = anssiz;
477	} else
478	len = resplen;
479	if (len < HFIXEDSZ) {
480	/*
481	* Undersized message.
482	*/
483	Dprint(_res.options & RES_DEBUG,
484	(stdout, ";; undersized: %d\n", len));
485	terrno = EMSGSIZE;
486	badns \|= (1 << ns);
487	res_close();
488	goto next_ns;
489	}
490	cp = ans;
491	while (len != 0 &&
492	(n = read(s, (char *)cp, (int)len)) > 0) {
493	cp += n;
494	len -= n;
495	}
496	if (n <= 0) {
497	terrno = errno;
498	Perror(stderr, "read(vc)", errno);
499	res_close();
500	goto next_ns;
501	}
502	if (truncated) {
503	/*
504	* Flush rest of answer
505	* so connection stays in synch.
506	*/
507	anhp->tc = 1;
508	len = resplen - anssiz;
509	while (len != 0) {
510	char junk[PACKETSZ];
511
512	n = (len > sizeof(junk)
513	? sizeof(junk)
514	: len);
515	if ((n = read(s, junk, n)) > 0)
516	len -= n;
517	else
518	break;
519	}
520	}
521	/*
522	* The calling applicating has bailed out of
523	* a previous call and failed to arrange to have
524	* the circuit closed or the server has got
525	* itself confused. Anyway drop the packet and
526	* wait for the correct one.
527	*/
528	if (hp->id != anhp->id) {
529	DprintQ((_res.options & RES_DEBUG) \|\|
530	(_res.pfcode & RES_PRF_REPLY),
531	(stdout, ";; old answer (unexpected):\n"),
532	ans, (resplen>anssiz)?anssiz:resplen);
533	goto read_len;
534	}
535	} else {
536	/*
537	* Use datagrams.
538	*/
539	#ifndef NOPOLL
540	struct pollfd pfd;
541	int msec;
542	#endif
543	struct timeval timeout;
544	#ifndef NOSELECT
545	fd_set dsmask, *dsmaskp;
546	int dsmasklen;
547	#endif
548	struct sockaddr_in from;
549	socklen_t fromlen;
550
551	if ((s < 0) \|\| vc) {
552	if (vc)
553	res_close();
554	s = socket(PF_INET, SOCK_DGRAM, 0);
555	if (s < 0) {
556	#ifndef CAN_RECONNECT
557	bad_dg_sock:
558	#endif
559	terrno = errno;
560	Perror(stderr, "socket(dg)", errno);
561	return (-1);
562	}
563	connected = 0;
564	}
565	#ifndef CANNOT_CONNECT_DGRAM
566	/*
567	* On a 4.3BSD+ machine (client and server,
568	* actually), sending to a nameserver datagram
569	* port with no nameserver will cause an
570	* ICMP port unreachable message to be returned.
571	* If our datagram socket is "connected" to the
572	* server, we get an ECONNREFUSED error on the next
573	* socket operation, and select returns if the
574	* error message is received. We can thus detect
575	* the absence of a nameserver without timing out.
576	* If we have sent queries to at least two servers,
577	* however, we don't want to remain connected,
578	* as we wish to receive answers from the first
579	* server to respond.
580	*/
581	if (_res.nscount == 1 \|\| (try == 0 && ns == 0)) {
582	/*
583	* Connect only if we are sure we won't
584	* receive a response from another server.
585	*/
586	if (!connected) {
587	if (connect(s, (struct sockaddr *)nsap,
588	sizeof *nsap
589	) < 0) {
590	Aerror(stderr,
591	"connect(dg)",
592	errno, *nsap);
593	badns \|= (1 << ns);
594	res_close();
595	goto next_ns;
596	}
597	connected = 1;
598	}
599	if (send(s, (char*)buf, buflen, 0) != buflen) {
600	Perror(stderr, "send", errno);
601	badns \|= (1 << ns);
602	res_close();
603	goto next_ns;
604	}
605	} else {
606	/*
607	* Disconnect if we want to listen
608	* for responses from more than one server.
609	*/
610	if (connected) {
611	#ifdef CAN_RECONNECT
612	struct sockaddr_in no_addr;
613
614	no_addr.sin_family = AF_INET;
615	no_addr.sin_addr.s_addr = INADDR_ANY;
616	no_addr.sin_port = 0;
617	(void) connect(s,
618	(struct sockaddr *)
619	&no_addr,
620	sizeof no_addr);
621	#else
622	int s1 = socket(PF_INET, SOCK_DGRAM,0);
623	if (s1 < 0)
624	goto bad_dg_sock;
625	(void) dup2(s1, s);
626	(void) close(s1);
627	Dprint(_res.options & RES_DEBUG,
628	(stdout, ";; new DG socket\n"))
629	#endif /* CAN_RECONNECT */
630	connected = 0;
631	errno = 0;
632	}
633	#endif /* !CANNOT_CONNECT_DGRAM */
634	if (sendto(s, (char*)buf, buflen, 0,
635	(struct sockaddr *)nsap,
636	sizeof *nsap)
637	!= buflen) {
638	Aerror(stderr, "sendto", errno, *nsap);
639	badns \|= (1 << ns);
640	res_close();
641	goto next_ns;
642	}
643	#ifndef CANNOT_CONNECT_DGRAM
644	}
645	#endif /* !CANNOT_CONNECT_DGRAM */
646
647	/*
648	* Wait for reply
649	*/
650	#ifndef NOPOLL
651	othersyscall:
652	if (use_poll) {
653	msec = (_res.retrans << try) * 1000;
654	if (try > 0)
655	msec /= _res.nscount;
656	if (msec <= 0)
657	msec = 1000;
658	} else {
659	#endif
660	timeout.tv_sec = (_res.retrans << try);
661	if (try > 0)
662	timeout.tv_sec /= _res.nscount;
663	if ((long) timeout.tv_sec <= 0)
664	timeout.tv_sec = 1;
665	timeout.tv_usec = 0;
666	#ifndef NOPOLL
667	}
668	#endif
669	wait:
670	if (s < 0) {
671	Perror(stderr, "s out-of-bounds", EMFILE);
672	res_close();
673	goto next_ns;
674	}
675	#ifndef NOPOLL
676	if (use_poll) {
677	struct sigaction sa, osa;
678	int sigsys_installed = 0;
679
680	pfd.fd = s;
681	pfd.events = POLLIN;
682	if (use_poll == 1) {
683	bzero(&sa, sizeof(sa));
684	sa.sa_handler = SIG_IGN;
685	if (sigaction(SIGSYS, &sa, &osa) >= 0)
686	sigsys_installed = 1;
687	}
688	n = poll(&pfd, 1, msec);
689	if (sigsys_installed == 1) {
690	int oerrno = errno;
691	sigaction(SIGSYS, &osa, NULL);
692	errno = oerrno;
693	}
694	/* XXX why does nosys() return EINVAL? */
695	if (n < 0 && (errno == ENOSYS \|\|
696	errno == EINVAL)) {
697	use_poll = 0;
698	goto othersyscall;
699	} else if (use_poll == 1)
700	use_poll = 2;
701	if (n < 0) {
702	if (errno == EINTR)
703	goto wait;
704	Perror(stderr, "poll", errno);
705	res_close();
706	goto next_ns;
707	}
708	} else {
709	#endif
710	#ifndef NOSELECT
711	dsmasklen = howmany(s + 1, NFDBITS) *
712	sizeof(fd_mask);
713	if (dsmasklen > sizeof(fd_set)) {
714	dsmaskp = (fd_set *)malloc(dsmasklen);
715	if (dsmaskp == NULL) {
716	res_close();
717	goto next_ns;
718	}
719	} else
720	dsmaskp = &dsmask;
721	/* only zero what we need */
722	bzero((char *)dsmaskp, dsmasklen);
723	FD_SET(s, dsmaskp);
724	n = select(s + 1, dsmaskp, (fd_set *)NULL,
725	(fd_set *)NULL, &timeout);
726	if (dsmaskp != &dsmask)
727	free(dsmaskp);
728	if (n < 0) {
729	if (errno == EINTR)
730	goto wait;
731	Perror(stderr, "select", errno);
732	res_close();
733	goto next_ns;
734	}
735	#endif
736	#ifndef NOPOLL
737	}
738	#endif
739
740	#ifdef NOSELECT
741	setsockopt (s, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof timeout);
742	#else
743	if (n == 0) {
744	/*
745	* timeout
746	*/
747	Dprint(_res.options & RES_DEBUG,
748	(stdout, ";; timeout\n"));
749	gotsomewhere = 1;
750	res_close();
751	goto next_ns;
752	}
753	#endif
754	errno = 0;
755	fromlen = sizeof(struct sockaddr_in);
756	resplen = recvfrom(s, (char*)ans, anssiz, 0,
757	(struct sockaddr *)&from, &fromlen);
758	if (resplen <= 0) {
759	#ifdef NOSELECT
760	if (errno == ETIMEDOUT) {
761	Dprint(_res.options & RES_DEBUG,
762	(stdout, ";; timeout\n"));
763	gotsomewhere = 1;
764	res_close();
765	goto next_ns;
766	}
767	#endif
768	Perror(stderr, "recvfrom", errno);
769	res_close();
770	goto next_ns;
771	}
772	gotsomewhere = 1;
773	if (resplen < HFIXEDSZ) {
774	/*
775	* Undersized message.
776	*/
777	Dprint(_res.options & RES_DEBUG,
778	(stdout, ";; undersized: %d\n",
779	resplen));
780	terrno = EMSGSIZE;
781	badns \|= (1 << ns);
782	res_close();
783	goto next_ns;
784	}
785	if (hp->id != anhp->id) {
786	/*
787	* response from old query, ignore it.
788	* XXX - potential security hazard could
789	* be detected here.
790	*/
791	DprintQ((_res.options & RES_DEBUG) \|\|
792	(_res.pfcode & RES_PRF_REPLY),
793	(stdout, ";; old answer:\n"),
794	ans, (resplen>anssiz)?anssiz:resplen);
795	goto wait;
796	}
797	#ifdef CHECK_SRVR_ADDR
798	if (!(_res.options & RES_INSECURE1) &&
799	!res_isourserver(&from)) {
800	/*
801	* response from wrong server? ignore it.
802	* XXX - potential security hazard could
803	* be detected here.
804	*/
805	DprintQ((_res.options & RES_DEBUG) \|\|
806	(_res.pfcode & RES_PRF_REPLY),
807	(stdout, ";; not our server:\n"),
808	ans, (resplen>anssiz)?anssiz:resplen);
809	goto wait;
810	}
811	#endif
812	if (!(_res.options & RES_INSECURE2) &&
813	!res_queriesmatch(buf, buf + buflen,
814	ans, ans + anssiz)) {
815	/*
816	* response contains wrong query? ignore it.
817	* XXX - potential security hazard could
818	* be detected here.
819	*/
820	DprintQ((_res.options & RES_DEBUG) \|\|
821	(_res.pfcode & RES_PRF_REPLY),
822	(stdout, ";; wrong query name:\n"),
823	ans, (resplen>anssiz)?anssiz:resplen);
824	goto wait;
825	}
826	if (anhp->rcode == SERVFAIL \|\|
827	anhp->rcode == NOTIMP \|\|
828	anhp->rcode == REFUSED) {
829	DprintQ(_res.options & RES_DEBUG,
830	(stdout, "server rejected query:\n"),
831	ans, (resplen>anssiz)?anssiz:resplen);
832	badns \|= (1 << ns);
833	res_close();
834	/* don't retry if called from dig */
835	if (!_res.pfcode)
836	goto next_ns;
837	}
838	if (!(_res.options & RES_IGNTC) && anhp->tc) {
839	/*
840	* get rest of answer;
841	* use TCP with same server.
842	*/
843	Dprint(_res.options & RES_DEBUG,
844	(stdout, ";; truncated answer\n"));
845	v_circuit = 1;
846	res_close();
847	goto same_ns;
848	}
849	} /if vc/dg/
850	Dprint((_res.options & RES_DEBUG) \|\|
851	((_res.pfcode & RES_PRF_REPLY) &&
852	(_res.pfcode & RES_PRF_HEAD1)),
853	(stdout, ";; got answer:\n"));
854	DprintQ((_res.options & RES_DEBUG) \|\|
855	(_res.pfcode & RES_PRF_REPLY),
856	(stdout, "%s", ""),
857	ans, (resplen>anssiz)?anssiz:resplen);
858	/*
859	* If using virtual circuits, we assume that the first server
860	* is preferred over the rest (i.e. it is on the local
861	* machine) and only keep that one open.
862	* If we have temporarily opened a virtual circuit,
863	* or if we haven't been asked to keep a socket open,
864	* close the socket.
865	*/
866	if ((v_circuit && (!(_res.options & RES_USEVC) \|\| ns != 0)) \|\|
867	!(_res.options & RES_STAYOPEN)) {
868	res_close();
869	}
870	if (Rhook) {
871	int done = 0, loops = 0;
872
873	do {
874	res_sendhookact act;
875
876	act = (*Rhook)(nsap, buf, buflen,
877	ans, anssiz, &resplen);
878	switch (act) {
879	case res_goahead:
880	case res_done:
881	done = 1;
882	break;
883	case res_nextns:
884	res_close();
885	goto next_ns;
886	case res_modified:
887	/* give the hook another try */
888	if (++loops < 42) /doug adams/
889	break;
890	/FALLTHROUGH/
891	case res_error:
892	/FALLTHROUGH/
893	default:
894	return (-1);
895	}
896	} while (!done);
897
898	}
899	return (resplen);
900	next_ns: ;
901	} /foreach ns/
902	} /foreach retry/
903	res_close();
904	if (!v_circuit) {
905	if (!gotsomewhere)
906	errno = ECONNREFUSED; /* no nameservers found */
907	else
908	errno = ETIMEDOUT; /* no answer obtained */
909	} else
910	errno = terrno;
911	return (-1);
912	}
913
914	/*
915	* This routine is for closing the socket if a virtual circuit is used and
916	* the program wants to close it. This provides support for endhostent()
917	* which expects to close the socket.
918	*
919	* This routine is not expected to be user visible.
920	*/
921	void
922	res_close()
923	{
924	if (s >= 0) {
925	(void) close(s);
926	s = -1;
927	connected = 0;
928	vc = 0;
929	}
930	}

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