Updated from BIND-4.9.3-BETA27.
[kopensolaris-gnu/glibc.git] / resolv / res_send.c
1 /*
2  * ++Copyright++ 1985, 1989, 1993
3  * -
4  * Copyright (c) 1985, 1989, 1993
5  *    The Regents of the University of California.  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 by the University of
18  *      California, Berkeley and its contributors.
19  * 4. Neither the name of the University nor the names of its contributors
20  *    may be used to endorse or promote products derived from this software
21  *    without specific prior written permission.
22  * 
23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.
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  * --Copyright--
54  */
55
56 #if defined(LIBC_SCCS) && !defined(lint)
57 static char sccsid[] = "@(#)res_send.c  8.1 (Berkeley) 6/4/93";
58 static char rcsid[] = "$Id$";
59 #endif /* LIBC_SCCS and not lint */
60
61         /* change this to "0"
62          * if you talk to a lot
63          * of multi-homed SunOS
64          * ("broken") name servers.
65          */
66 #define CHECK_SRVR_ADDR 1       /* XXX - should be in options.h */
67
68 /*
69  * Send query to name server and wait for reply.
70  */
71
72 #include <sys/param.h>
73 #include <sys/time.h>
74 #include <sys/socket.h>
75 #include <sys/uio.h>
76 #include <netinet/in.h>
77 #include <arpa/nameser.h>
78 #include <arpa/inet.h>
79
80 #include <stdio.h>
81 #include <netdb.h>
82 #include <errno.h>
83 #include <resolv.h>
84 #if defined(BSD) && (BSD >= 199306)
85 # include <stdlib.h>
86 # include <string.h>
87 # include <unistd.h>
88 #else
89 # include "../conf/portability.h"
90 #endif
91
92 #if defined(USE_OPTIONS_H)
93 # include <../conf/options.h>
94 #endif
95
96 void _res_close __P((void));
97
98 static int s = -1;      /* socket used for communications */
99 static int connected = 0;       /* is the socket connected */
100 static int vc = 0;      /* is the socket a virtual ciruit? */
101
102 #ifndef FD_SET
103 /* XXX - should be in portability.h */
104 #define NFDBITS         32
105 #define FD_SETSIZE      32
106 #define FD_SET(n, p)    ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
107 #define FD_CLR(n, p)    ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
108 #define FD_ISSET(n, p)  ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
109 #define FD_ZERO(p)      bzero((char *)(p), sizeof(*(p)))
110 #endif
111
112 /* XXX - this should be done in portability.h */
113 #if (defined(BSD) && (BSD >= 199103)) || defined(linux)
114 # define CAN_RECONNECT 1
115 #else
116 # define CAN_RECONNECT 0
117 #endif
118
119 #ifndef DEBUG
120 #   define Dprint(cond, args) /*empty*/
121 #   define DprintQ(cond, args, query, size) /*empty*/
122 #   define Aerror(file, string, error, address) /*empty*/
123 #   define Perror(file, string, error) /*empty*/
124 #else
125 #   define Dprint(cond, args) if (cond) {fprintf args;} else {}
126 #   define DprintQ(cond, args, query, size) if (cond) {\
127                         fprintf args;\
128                         __fp_nquery(query, size, stdout);\
129                 } else {}
130     static void
131     Aerror(file, string, error, address)
132         FILE *file;
133         char *string;
134         int error;
135         struct sockaddr_in address;
136     {
137         int save = errno;
138
139         if (_res.options & RES_DEBUG) {
140                 fprintf(file, "res_send: %s ([%s].%u): %s\n",
141                         string,
142                         inet_ntoa(address.sin_addr),
143                         ntohs(address.sin_port),
144                         strerror(error));
145         }
146         errno = save;
147     }
148     static void
149     Perror(file, string, error)
150         FILE *file;
151         char *string;
152         int error;
153     {
154         int save = errno;
155
156         if (_res.options & RES_DEBUG) {
157                 fprintf(file, "res_send: %s: %s\n",
158                         string, strerror(error));
159         }
160         errno = save;
161     }
162 #endif
163
164 static res_send_qhook Qhook = NULL;
165 static res_send_rhook Rhook = NULL;
166
167 void
168 res_send_setqhook(hook)
169         res_send_qhook hook;
170 {
171
172         Qhook = hook;
173 }
174
175 void
176 res_send_setrhook(hook)
177         res_send_rhook hook;
178 {
179
180         Rhook = hook;
181 }
182
183 /* int
184  * res_isourserver(ina)
185  *      looks up "ina" in _res.ns_addr_list[]
186  * returns:
187  *      0  : not found
188  *      >0 : found
189  * author:
190  *      paul vixie, 29may94
191  */
192 int
193 res_isourserver(inp)
194         const struct sockaddr_in *inp;
195 {
196         struct sockaddr_in ina;
197         register int ns, ret;
198
199         ina = *inp;
200         ret = 0;
201         for (ns = 0;  ns < _res.nscount;  ns++) {
202                 register const struct sockaddr_in *srv = &_res.nsaddr_list[ns];
203
204                 if (srv->sin_family == ina.sin_family &&
205                     srv->sin_port == ina.sin_port &&
206                     (srv->sin_addr.s_addr == INADDR_ANY ||
207                      srv->sin_addr.s_addr == ina.sin_addr.s_addr)) {
208                         ret++;
209                         break;
210                 }
211         }
212         return (ret);
213 }
214
215 /* int
216  * res_nameinquery(name, type, class, buf, eom)
217  *      look for (name,type,class) in the query section of packet (buf,eom)
218  * returns:
219  *      -1 : format error
220  *      0  : not found
221  *      >0 : found
222  * author:
223  *      paul vixie, 29may94
224  */
225 int
226 res_nameinquery(name, type, class, buf, eom)
227         const char *name;
228         register int type, class;
229         const u_char *buf, *eom;
230 {
231         register const u_char *cp = buf + HFIXEDSZ;
232         int qdcount = ntohs(((HEADER*)buf)->qdcount);
233
234         while (qdcount-- > 0) {
235                 char tname[MAXDNAME+1];
236                 register int n, ttype, tclass;
237
238                 n = dn_expand(buf, eom, cp, tname, sizeof tname);
239                 if (n < 0)
240                         return (-1);
241                 cp += n;
242                 ttype = _getshort(cp); cp += INT16SZ;
243                 tclass = _getshort(cp); cp += INT16SZ;
244                 if (ttype == type &&
245                     tclass == class &&
246                     strcasecmp(tname, name) == 0)
247                         return (1);
248         }
249         return (0);
250 }
251
252 /* int
253  * res_queriesmatch(buf1, eom1, buf2, eom2)
254  *      is there a 1:1 mapping of (name,type,class)
255  *      in (buf1,eom1) and (buf2,eom2)?
256  * returns:
257  *      -1 : format error
258  *      0  : not a 1:1 mapping
259  *      >0 : is a 1:1 mapping
260  * author:
261  *      paul vixie, 29may94
262  */
263 int
264 res_queriesmatch(buf1, eom1, buf2, eom2)
265         const u_char *buf1, *eom1;
266         const u_char *buf2, *eom2;
267 {
268         register const u_char *cp = buf1 + HFIXEDSZ;
269         int qdcount = ntohs(((HEADER*)buf1)->qdcount);
270
271         if (qdcount != ntohs(((HEADER*)buf2)->qdcount))
272                 return (0);
273         while (qdcount-- > 0) {
274                 char tname[MAXDNAME+1];
275                 register int n, ttype, tclass;
276
277                 n = dn_expand(buf1, eom1, cp, tname, sizeof tname);
278                 if (n < 0)
279                         return (-1);
280                 cp += n;
281                 ttype = _getshort(cp);  cp += INT16SZ;
282                 tclass = _getshort(cp); cp += INT16SZ;
283                 if (!res_nameinquery(tname, ttype, tclass, buf2, eom2))
284                         return (0);
285         }
286         return (1);
287 }
288
289 int
290 res_send(buf, buflen, ans, anssiz)
291         const u_char *buf;
292         int buflen;
293         u_char *ans;
294         int anssiz;
295 {
296         HEADER *hp = (HEADER *) buf;
297         HEADER *anhp = (HEADER *) ans;
298         int gotsomewhere, connreset, terrno, try, v_circuit, resplen, ns;
299         register int n;
300         u_int badns;    /* XXX NSMAX can't exceed #/bits in this var */
301
302         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
303                 /* errno should have been set by res_init() in this case. */
304                 return (-1);
305         }
306         DprintQ((_res.options & RES_DEBUG) || (_res.pfcode & RES_PRF_QUERY),
307                 (stdout, ";; res_send()\n"), buf, buflen);
308         v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
309         gotsomewhere = 0;
310         connreset = 0;
311         terrno = ETIMEDOUT;
312         badns = 0;
313
314         /*
315          * Send request, RETRY times, or until successful
316          */
317         for (try = 0; try < _res.retry; try++) {
318             for (ns = 0; ns < _res.nscount; ns++) {
319                 struct sockaddr_in *nsap = &_res.nsaddr_list[ns];
320     same_ns:
321                 if (badns & (1 << ns)) {
322                         _res_close();
323                         goto next_ns;
324                 }
325
326                 if (Qhook) {
327                         int done = 0, loops = 0;
328
329                         do {
330                                 res_sendhookact act;
331
332                                 act = (*Qhook)(&nsap, &buf, &buflen,
333                                                ans, anssiz, &resplen);
334                                 switch (act) {
335                                 case res_goahead:
336                                         done = 1;
337                                         break;
338                                 case res_nextns:
339                                         _res_close();
340                                         goto next_ns;
341                                 case res_done:
342                                         return (resplen);
343                                 case res_modified:
344                                         /* give the hook another try */
345                                         if (++loops < 42) /*doug adams*/
346                                                 break;
347                                         /*FALLTHROUGH*/
348                                 case res_error:
349                                         /*FALLTHROUGH*/
350                                 default:
351                                         return (-1);
352                                 }
353                         } while (!done);
354                 }
355
356                 Dprint(_res.options & RES_DEBUG,
357                        (stdout, ";; Querying server (# %d) address = %s\n",
358                         ns + 1, inet_ntoa(nsap->sin_addr)));
359
360                 if (v_circuit) {
361                         int truncated;
362                         struct iovec iov[2];
363                         u_short len;
364                         u_char *cp;
365
366                         /*
367                          * Use virtual circuit;
368                          * at most one attempt per server.
369                          */
370                         try = _res.retry;
371                         truncated = 0;
372                         if ((s < 0) || (!vc)) {
373                                 if (s >= 0)
374                                         _res_close();
375
376                                 s = socket(PF_INET, SOCK_STREAM, 0);
377                                 if (s < 0) {
378                                         terrno = errno;
379                                         Perror(stderr, "socket(vc)", errno);
380                                         return (-1);
381                                 }
382                                 errno = 0;
383                                 if (connect(s, (struct sockaddr *)nsap,
384                                             sizeof(struct sockaddr)) < 0) {
385                                         terrno = errno;
386                                         Aerror(stderr, "connect/vc",
387                                                errno, *nsap);
388                                         badns |= (1 << ns);
389                                         _res_close();
390                                         goto next_ns;
391                                 }
392                                 vc = 1;
393                         }
394                         /*
395                          * Send length & message
396                          */
397                         putshort((u_short)buflen, (u_char*)&len);
398                         iov[0].iov_base = (caddr_t)&len;
399                         iov[0].iov_len = INT16SZ;
400                         iov[1].iov_base = (caddr_t)buf;
401                         iov[1].iov_len = buflen;
402                         if (writev(s, iov, 2) != (INT16SZ + buflen)) {
403                                 terrno = errno;
404                                 Perror(stderr, "write failed", errno);
405                                 badns |= (1 << ns);
406                                 _res_close();
407                                 goto next_ns;
408                         }
409                         /*
410                          * Receive length & response
411                          */
412                         cp = ans;
413                         len = INT16SZ;
414                         while ((n = read(s, (char *)cp, (int)len)) > 0) {
415                                 cp += n;
416                                 if ((len -= n) <= 0)
417                                         break;
418                         }
419                         if (n <= 0) {
420                                 terrno = errno;
421                                 Perror(stderr, "read failed", errno);
422                                 _res_close();
423                                 /*
424                                  * A long running process might get its TCP
425                                  * connection reset if the remote server was
426                                  * restarted.  Requery the server instead of
427                                  * trying a new one.  When there is only one
428                                  * server, this means that a query might work
429                                  * instead of failing.  We only allow one reset
430                                  * per query to prevent looping.
431                                  */
432                                 if (terrno == ECONNRESET && !connreset) {
433                                         connreset = 1;
434                                         _res_close();
435                                         goto same_ns;
436                                 }
437                                 _res_close();
438                                 goto next_ns;
439                         }
440                         resplen = _getshort(ans);
441                         if (resplen > anssiz) {
442                                 Dprint(_res.options & RES_DEBUG,
443                                        (stdout, ";; response truncated\n")
444                                        );
445                                 truncated = 1;
446                                 len = anssiz;
447                         } else
448                                 len = resplen;
449                         cp = ans;
450                         while (len != 0 &&
451                                (n = read(s, (char *)cp, (int)len)) > 0) {
452                                 cp += n;
453                                 len -= n;
454                         }
455                         if (n <= 0) {
456                                 terrno = errno;
457                                 Perror(stderr, "read(vc)", errno);
458                                 _res_close();
459                                 goto next_ns;
460                         }
461                         if (truncated) {
462                                 /*
463                                  * Flush rest of answer
464                                  * so connection stays in synch.
465                                  */
466                                 anhp->tc = 1;
467                                 len = resplen - anssiz;
468                                 while (len != 0) {
469                                         char junk[PACKETSZ];
470
471                                         n = (len > sizeof(junk)
472                                              ? sizeof(junk)
473                                              : len);
474                                         if ((n = read(s, junk, n)) > 0)
475                                                 len -= n;
476                                         else
477                                                 break;
478                                 }
479                         }
480                 } else {
481                         /*
482                          * Use datagrams.
483                          */
484                         struct timeval timeout;
485                         fd_set dsmask;
486                         struct sockaddr_in from;
487                         int fromlen;
488
489                         if ((s < 0) || vc) {
490                                 if (vc)
491                                         _res_close();
492                                 s = socket(PF_INET, SOCK_DGRAM, 0);
493                                 if (s < 0) {
494 #if !CAN_RECONNECT
495  bad_dg_sock:
496 #endif
497                                         terrno = errno;
498                                         Perror(stderr, "socket(dg)", errno);
499                                         return (-1);
500                                 }
501                                 connected = 0;
502                         }
503                         /*
504                          * On a 4.3BSD+ machine (client and server,
505                          * actually), sending to a nameserver datagram
506                          * port with no nameserver will cause an
507                          * ICMP port unreachable message to be returned.
508                          * If our datagram socket is "connected" to the
509                          * server, we get an ECONNREFUSED error on the next
510                          * socket operation, and select returns if the
511                          * error message is received.  We can thus detect
512                          * the absence of a nameserver without timing out.
513                          * If we have sent queries to at least two servers,
514                          * however, we don't want to remain connected,
515                          * as we wish to receive answers from the first
516                          * server to respond.
517                          */
518                         if (_res.nscount == 1 || (try == 0 && ns == 0)) {
519                                 /*
520                                  * Connect only if we are sure we won't
521                                  * receive a response from another server.
522                                  */
523                                 if (!connected) {
524                                         if (connect(s, (struct sockaddr *)nsap,
525                                                     sizeof(struct sockaddr)
526                                                     ) < 0) {
527                                                 Aerror(stderr,
528                                                        "connect(dg)",
529                                                        errno, *nsap);
530                                                 badns |= (1 << ns);
531                                                 _res_close();
532                                                 goto next_ns;
533                                         }
534                                         connected = 1;
535                                 }
536                                 if (send(s, (char*)buf, buflen, 0) != buflen) {
537                                         Perror(stderr, "send", errno);
538                                         badns |= (1 << ns);
539                                         _res_close();
540                                         goto next_ns;
541                                 }
542                         } else {
543                                 /*
544                                  * Disconnect if we want to listen
545                                  * for responses from more than one server.
546                                  */
547                                 if (connected) {
548 #if CAN_RECONNECT
549                                         struct sockaddr_in no_addr;
550
551                                         no_addr.sin_family = AF_INET;
552                                         no_addr.sin_addr.s_addr = INADDR_ANY;
553                                         no_addr.sin_port = 0;
554                                         (void) connect(s,
555                                                        (struct sockaddr *)
556                                                         &no_addr,
557                                                        sizeof(no_addr));
558 #else
559                                         int s1 = socket(PF_INET, SOCK_DGRAM,0);
560                                         if (s1 < 0)
561                                                 goto bad_dg_sock;
562                                         (void) dup2(s1, s);
563                                         (void) close(s1);
564                                         Dprint(_res.options & RES_DEBUG,
565                                                (stdout, ";; new DG socket\n"))
566 #endif
567                                         connected = 0;
568                                         errno = 0;
569                                 }
570                                 if (sendto(s, (char*)buf, buflen, 0,
571                                            (struct sockaddr *)nsap,
572                                            sizeof(struct sockaddr))
573                                     != buflen) {
574                                         Aerror(stderr, "sendto", errno, *nsap);
575                                         badns |= (1 << ns);
576                                         _res_close();
577                                         goto next_ns;
578                                 }
579                         }
580
581                         /*
582                          * Wait for reply
583                          */
584                         timeout.tv_sec = (_res.retrans << try);
585                         if (try > 0)
586                                 timeout.tv_sec /= _res.nscount;
587                         if ((long) timeout.tv_sec <= 0)
588                                 timeout.tv_sec = 1;
589                         timeout.tv_usec = 0;
590     wait:
591                         FD_ZERO(&dsmask);
592                         FD_SET(s, &dsmask);
593                         n = select(s+1, &dsmask, (fd_set *)NULL,
594                                    (fd_set *)NULL, &timeout);
595                         if (n < 0) {
596                                 Perror(stderr, "select", errno);
597                                 _res_close();
598                                 goto next_ns;
599                         }
600                         if (n == 0) {
601                                 /*
602                                  * timeout
603                                  */
604                                 Dprint(_res.options & RES_DEBUG,
605                                        (stdout, ";; timeout\n"));
606                                 gotsomewhere = 1;
607                                 _res_close();
608                                 goto next_ns;
609                         }
610                         errno = 0;
611                         fromlen = sizeof(struct sockaddr_in);
612                         resplen = recvfrom(s, (char*)ans, anssiz, 0,
613                                            (struct sockaddr *)&from, &fromlen);
614                         if (resplen <= 0) {
615                                 Perror(stderr, "recvfrom", errno);
616                                 _res_close();
617                                 goto next_ns;
618                         }
619                         gotsomewhere = 1;
620                         if (hp->id != anhp->id) {
621                                 /*
622                                  * response from old query, ignore it.
623                                  * XXX - potential security hazard could
624                                  *       be detected here.
625                                  */
626                                 DprintQ((_res.options & RES_DEBUG) ||
627                                         (_res.pfcode & RES_PRF_REPLY),
628                                         (stdout, ";; old answer:\n"),
629                                         ans, resplen);
630                                 goto wait;
631                         }
632 #if CHECK_SRVR_ADDR
633                         if (!(_res.options & RES_INSECURE1) &&
634                             !res_isourserver(&from)) {
635                                 /*
636                                  * response from wrong server? ignore it.
637                                  * XXX - potential security hazard could
638                                  *       be detected here.
639                                  */
640                                 DprintQ((_res.options & RES_DEBUG) ||
641                                         (_res.pfcode & RES_PRF_REPLY),
642                                         (stdout, ";; not our server:\n"),
643                                         ans, resplen);
644                                 goto wait;
645                         }
646 #endif
647                         if (!(_res.options & RES_INSECURE2) &&
648                             !res_queriesmatch(buf, buf + buflen,
649                                               ans, ans + anssiz)) {
650                                 /*
651                                  * response contains wrong query? ignore it.
652                                  * XXX - potential security hazard could
653                                  *       be detected here.
654                                  */
655                                 DprintQ((_res.options & RES_DEBUG) ||
656                                         (_res.pfcode & RES_PRF_REPLY),
657                                         (stdout, ";; wrong query name:\n"),
658                                         ans, resplen);
659                                 goto wait;
660                         }
661                         if (anhp->rcode == SERVFAIL ||
662                             anhp->rcode == NOTIMP ||
663                             anhp->rcode == REFUSED) {
664                                 DprintQ(_res.options & RES_DEBUG,
665                                         (stdout, "server rejected query:\n"),
666                                         ans, resplen);
667                                 badns |= (1 << ns);
668                                 _res_close();
669                                 /* don't retry if called from dig */
670                                 if (!_res.pfcode)
671                                         goto next_ns;
672                         }
673                         if (!(_res.options & RES_IGNTC) && anhp->tc) {
674                                 /*
675                                  * get rest of answer;
676                                  * use TCP with same server.
677                                  */
678                                 Dprint(_res.options & RES_DEBUG,
679                                        (stdout, ";; truncated answer\n"));
680                                 v_circuit = 1;
681                                 _res_close();
682                                 goto same_ns;
683                         }
684                 } /*if vc/dg*/
685                 Dprint((_res.options & RES_DEBUG) ||
686                        ((_res.pfcode & RES_PRF_REPLY) &&
687                         (_res.pfcode & RES_PRF_HEAD1)),
688                        (stdout, ";; got answer:\n"));
689                 DprintQ((_res.options & RES_DEBUG) ||
690                         (_res.pfcode & RES_PRF_REPLY),
691                         (stdout, ""),
692                         ans, resplen);
693                 /*
694                  * If using virtual circuits, we assume that the first server
695                  * is preferred over the rest (i.e. it is on the local
696                  * machine) and only keep that one open.
697                  * If we have temporarily opened a virtual circuit,
698                  * or if we haven't been asked to keep a socket open,
699                  * close the socket.
700                  */
701                 if ((v_circuit && (!(_res.options & RES_USEVC) || ns != 0)) ||
702                     !(_res.options & RES_STAYOPEN)) {
703                         _res_close();
704                 }
705                 if (Rhook) {
706                         int done = 0, loops = 0;
707
708                         do {
709                                 res_sendhookact act;
710
711                                 act = (*Rhook)(nsap, buf, buflen,
712                                                ans, anssiz, &resplen);
713                                 switch (act) {
714                                 case res_goahead:
715                                 case res_done:
716                                         done = 1;
717                                         break;
718                                 case res_nextns:
719                                         _res_close();
720                                         goto next_ns;
721                                 case res_modified:
722                                         /* give the hook another try */
723                                         if (++loops < 42) /*doug adams*/
724                                                 break;
725                                         /*FALLTHROUGH*/
726                                 case res_error:
727                                         /*FALLTHROUGH*/
728                                 default:
729                                         return (-1);
730                                 }
731                         } while (!done);
732
733                 }
734                 return (resplen);
735     next_ns: ;
736            } /*foreach ns*/
737         } /*foreach retry*/
738         _res_close();
739         if (!v_circuit)
740                 if (!gotsomewhere)
741                         errno = ECONNREFUSED;   /* no nameservers found */
742                 else
743                         errno = ETIMEDOUT;      /* no answer obtained */
744         else
745                 errno = terrno;
746         return (-1);
747 }
748
749 /*
750  * This routine is for closing the socket if a virtual circuit is used and
751  * the program wants to close it.  This provides support for endhostent()
752  * which expects to close the socket.
753  *
754  * This routine is not expected to be user visible.
755  */
756 void
757 _res_close()
758 {
759         if (s >= 0) {
760                 (void) close(s);
761                 s = -1;
762                 connected = 0;
763                 vc = 0;
764         }
765 }