aboutsummaryrefslogtreecommitdiff
path: root/networking/nslookup.c
blob: dda22de0e5d7bcd7c0c0ea6d00d4c4a7ff8a0eae (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
/* vi: set sw=4 ts=4: */

//config:config NSLOOKUP
//config:	bool "nslookup (9.7 kb)"
//config:	default y
//config:	help
//config:	nslookup is a tool to query Internet name servers.
//config:
//config:config FEATURE_NSLOOKUP_BIG
//config:	bool "Use internal resolver code instead of libc"
//config:	depends on NSLOOKUP
//config:	default y
//config:
//config:config FEATURE_NSLOOKUP_LONG_OPTIONS
//config:	bool "Enable long options"
//config:	default y
//config:	depends on FEATURE_NSLOOKUP_BIG && LONG_OPTS

//applet:IF_NSLOOKUP(APPLET(nslookup, BB_DIR_USR_BIN, BB_SUID_DROP))

//kbuild:lib-$(CONFIG_NSLOOKUP) += nslookup.o

//usage:#define nslookup_trivial_usage
//usage:       IF_FEATURE_NSLOOKUP_BIG("[-type=QUERY_TYPE] [-debug] ") "HOST [DNS_SERVER]"
//usage:#define nslookup_full_usage "\n\n"
//usage:       "Query DNS about HOST"
//usage:       IF_FEATURE_NSLOOKUP_BIG("\n")
//usage:       IF_FEATURE_NSLOOKUP_BIG("\nQUERY_TYPE: soa,ns,a,"IF_FEATURE_IPV6("aaaa,")"cname,mx,txt,ptr,any")
//usage:#define nslookup_example_usage
//usage:       "$ nslookup localhost\n"
//usage:       "Server:     default\n"
//usage:       "Address:    default\n"
//usage:       "\n"
//usage:       "Name:       debian\n"
//usage:       "Address:    127.0.0.1\n"

#include <resolv.h>
#include <net/if.h>	/* for IFNAMSIZ */
//#include <arpa/inet.h>
//#include <netdb.h>
#include "libbb.h"
#include "common_bufsiz.h"


#if !ENABLE_FEATURE_NSLOOKUP_BIG

/*
 * Mini nslookup implementation for busybox
 *
 * Copyright (C) 1999,2000 by Lineo, inc. and John Beppu
 * Copyright (C) 1999,2000,2001 by John Beppu <beppu@codepoet.org>
 *
 * Correct default name server display and explicit name server option
 * added by Ben Zeckel <bzeckel@hmc.edu> June 2001
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

/*
 * I'm only implementing non-interactive mode;
 * I totally forgot nslookup even had an interactive mode.
 *
 * This applet is the only user of res_init(). Without it,
 * you may avoid pulling in _res global from libc.
 */

/* Examples of 'standard' nslookup output
 * $ nslookup yahoo.com
 * Server:         128.193.0.10
 * Address:        128.193.0.10#53
 *
 * Non-authoritative answer:
 * Name:   yahoo.com
 * Address: 216.109.112.135
 * Name:   yahoo.com
 * Address: 66.94.234.13
 *
 * $ nslookup 204.152.191.37
 * Server:         128.193.4.20
 * Address:        128.193.4.20#53
 *
 * Non-authoritative answer:
 * 37.191.152.204.in-addr.arpa     canonical name = 37.32-27.191.152.204.in-addr.arpa.
 * 37.32-27.191.152.204.in-addr.arpa       name = zeus-pub2.kernel.org.
 *
 * Authoritative answers can be found from:
 * 32-27.191.152.204.in-addr.arpa  nameserver = ns1.kernel.org.
 * 32-27.191.152.204.in-addr.arpa  nameserver = ns2.kernel.org.
 * 32-27.191.152.204.in-addr.arpa  nameserver = ns3.kernel.org.
 * ns1.kernel.org  internet address = 140.211.167.34
 * ns2.kernel.org  internet address = 204.152.191.4
 * ns3.kernel.org  internet address = 204.152.191.36
 */

static int print_host(const char *hostname, const char *header)
{
	/* We can't use xhost2sockaddr() - we want to get ALL addresses,
	 * not just one */
	struct addrinfo *result = NULL;
	int rc;
	struct addrinfo hint;

	memset(&hint, 0 , sizeof(hint));
	/* hint.ai_family = AF_UNSPEC; - zero anyway */
	/* Needed. Or else we will get each address thrice (or more)
	 * for each possible socket type (tcp,udp,raw...): */
	hint.ai_socktype = SOCK_STREAM;
	// hint.ai_flags = AI_CANONNAME;
	rc = getaddrinfo(hostname, NULL /*service*/, &hint, &result);

	if (rc == 0) {
		struct addrinfo *cur = result;
		unsigned cnt = 0;

		printf("%-10s %s\n", header, hostname);
		// puts(cur->ai_canonname); ?
		while (cur) {
			char *dotted, *revhost;
			dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr);
			revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr);

			printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n');
			if (revhost) {
				puts(revhost);
				if (ENABLE_FEATURE_CLEAN_UP)
					free(revhost);
			}
			if (ENABLE_FEATURE_CLEAN_UP)
				free(dotted);
			cur = cur->ai_next;
		}
	} else {
#if ENABLE_VERBOSE_RESOLUTION_ERRORS
		bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc));
#else
		bb_error_msg("can't resolve '%s'", hostname);
#endif
	}
	if (ENABLE_FEATURE_CLEAN_UP && result)
		freeaddrinfo(result);
	return (rc != 0);
}

/* lookup the default nameserver and display it */
static void server_print(void)
{
	char *server;
	struct sockaddr *sa;

#if ENABLE_FEATURE_IPV6
	sa = (struct sockaddr*)_res._u._ext.nsaddrs[0];
	if (!sa)
#endif
		sa = (struct sockaddr*)&_res.nsaddr_list[0];
	server = xmalloc_sockaddr2dotted_noport(sa);

	print_host(server, "Server:");
	if (ENABLE_FEATURE_CLEAN_UP)
		free(server);
	bb_putchar('\n');
}

/* alter the global _res nameserver structure to use
   an explicit dns server instead of what is in /etc/resolv.conf */
static void set_default_dns(const char *server)
{
	len_and_sockaddr *lsa;

	if (!server)
		return;

	/* NB: this works even with, say, "[::1]:5353"! :) */
	lsa = xhost2sockaddr(server, 53);

	if (lsa->u.sa.sa_family == AF_INET) {
		_res.nscount = 1;
		/* struct copy */
		_res.nsaddr_list[0] = lsa->u.sin;
	}
#if ENABLE_FEATURE_IPV6
	/* Hoped libc can cope with IPv4 address there too.
	 * No such luck, glibc 2.4 segfaults even with IPv6,
	 * maybe I misunderstand how to make glibc use IPv6 addr?
	 * (uclibc 0.9.31+ should work) */
	if (lsa->u.sa.sa_family == AF_INET6) {
		// glibc neither SEGVs nor sends any dgrams with this
		// (strace shows no socket ops):
		//_res.nscount = 0;
		_res._u._ext.nscount = 1;
		/* store a pointer to part of malloc'ed lsa */
		_res._u._ext.nsaddrs[0] = &lsa->u.sin6;
		/* must not free(lsa)! */
	}
#endif
}

int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int nslookup_main(int argc, char **argv)
{
	/* We allow 1 or 2 arguments.
	 * The first is the name to be looked up and the second is an
	 * optional DNS server with which to do the lookup.
	 * More than 3 arguments is an error to follow the pattern of the
	 * standard nslookup */
	if (!argv[1] || argv[1][0] == '-' || argc > 3)
		bb_show_usage();

	/* initialize DNS structure _res used in printing the default
	 * name server and in the explicit name server option feature. */
	res_init();
	/* rfc2133 says this enables IPv6 lookups */
	/* (but it also says "may be enabled in /etc/resolv.conf") */
	/*_res.options |= RES_USE_INET6;*/

	set_default_dns(argv[2]);

	server_print();

	/* getaddrinfo and friends are free to request a resolver
	 * reinitialization. Just in case, set_default_dns() again
	 * after getaddrinfo (in server_print). This reportedly helps
	 * with bug 675 "nslookup does not properly use second argument"
	 * at least on Debian Wheezy and Openwrt AA (eglibc based).
	 */
	set_default_dns(argv[2]);

	return print_host(argv[1], "Name:");
}


#else /****** A version from LEDE / OpenWRT ******/

/*
 * musl compatible nslookup
 *
 * Copyright (C) 2017 Jo-Philipp Wich <jo@mein.io>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#if 0
# define dbg(...) fprintf(stderr, __VA_ARGS__)
#else
# define dbg(...) ((void)0)
#endif

struct ns {
	const char *name;
	len_and_sockaddr *lsa;
	//UNUSED: int failures;
	int replies;
};

struct query {
	const char *name;
	unsigned qlen;
//	unsigned latency;
//	uint8_t rcode;
	unsigned char query[512];
//	unsigned char reply[512];
};

static const struct {
	unsigned char type;
	char name[7];
} qtypes[] ALIGN1 = {
	{ ns_t_soa,   "SOA"   },
	{ ns_t_ns,    "NS"    },
	{ ns_t_a,     "A"     },
#if ENABLE_FEATURE_IPV6
	{ ns_t_aaaa,  "AAAA"  },
#endif
	{ ns_t_cname, "CNAME" },
	{ ns_t_mx,    "MX"    },
	{ ns_t_txt,   "TXT"   },
	{ ns_t_srv,   "SRV"   },
	{ ns_t_ptr,   "PTR"   },
	{ ns_t_any,   "ANY"   },
};

static const char *const rcodes[] ALIGN_PTR = {
	"NOERROR",    // 0
	"FORMERR",    // 1
	"SERVFAIL",   // 2
	"NXDOMAIN",   // 3
	"NOTIMP",     // 4
	"REFUSED",    // 5
	"YXDOMAIN",   // 6
	"YXRRSET",    // 7
	"NXRRSET",    // 8
	"NOTAUTH",    // 9
	"NOTZONE",    // 10
	"11",         // 11 not assigned
	"12",         // 12 not assigned
	"13",         // 13 not assigned
	"14",         // 14 not assigned
	"15",         // 15 not assigned
};

#if ENABLE_FEATURE_IPV6
static const char v4_mapped[12] = { 0,0,0,0, 0,0,0,0, 0,0,0xff,0xff };
#endif

struct globals {
	unsigned default_port;
	unsigned default_retry;
	unsigned default_timeout;
	unsigned query_count;
	unsigned serv_count;
	struct ns *server;
	struct query *query;
	char *search;
	smalluint have_search_directive;
	smalluint exitcode;
} FIX_ALIASING;
#define G (*(struct globals*)bb_common_bufsiz1)
#define INIT_G() do { \
	setup_common_bufsiz(); \
	G.default_port = 53; \
	G.default_retry = 2; \
	G.default_timeout = 5; \
} while (0)

enum {
	OPT_debug = (1 << 0),
};

static int parse_reply(const unsigned char *msg, size_t len)
{
	HEADER *header;

	ns_msg handle;
	ns_rr rr;
	int i, n, rdlen;
	const char *format = NULL;
	char astr[INET6_ADDRSTRLEN], dname[MAXDNAME];
	const unsigned char *cp;

	header = (HEADER *)msg;
	if (!header->aa)
		printf("Non-authoritative answer:\n");

	if (ns_initparse(msg, len, &handle) != 0) {
		//printf("Unable to parse reply: %s\n", strerror(errno));
		return -1;
	}

	for (i = 0; i < ns_msg_count(handle, ns_s_an); i++) {
		if (ns_parserr(&handle, ns_s_an, i, &rr) != 0) {
			//printf("Unable to parse resource record: %s\n", strerror(errno));
			return -1;
		}

		rdlen = ns_rr_rdlen(rr);

		switch (ns_rr_type(rr))
		{
		case ns_t_a:
			if (rdlen != 4) {
				dbg("unexpected A record length %d\n", rdlen);
				return -1;
			}
			inet_ntop(AF_INET, ns_rr_rdata(rr), astr, sizeof(astr));
			printf("Name:\t%s\nAddress: %s\n", ns_rr_name(rr), astr);
			break;

#if ENABLE_FEATURE_IPV6
		case ns_t_aaaa:
			if (rdlen != 16) {
				dbg("unexpected AAAA record length %d\n", rdlen);
				return -1;
			}
			inet_ntop(AF_INET6, ns_rr_rdata(rr), astr, sizeof(astr));
			/* bind-utils-9.11.3 uses the same format for A and AAAA answers */
			printf("Name:\t%s\nAddress: %s\n", ns_rr_name(rr), astr);
			break;
#endif

		case ns_t_ns:
			if (!format)
				format = "%s\tnameserver = %s\n";
			/* fall through */

		case ns_t_cname:
			if (!format)
				format = "%s\tcanonical name = %s\n";
			/* fall through */

		case ns_t_ptr:
			if (!format)
				format = "%s\tname = %s\n";
			if (ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle),
					ns_rr_rdata(rr), dname, sizeof(dname)) < 0
			) {
				//printf("Unable to uncompress domain: %s\n", strerror(errno));
				return -1;
			}
			printf(format, ns_rr_name(rr), dname);
			break;

		case ns_t_mx:
			if (rdlen < 2) {
				printf("MX record too short\n");
				return -1;
			}
			n = ns_get16(ns_rr_rdata(rr));
			if (ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle),
					ns_rr_rdata(rr) + 2, dname, sizeof(dname)) < 0
			) {
				//printf("Cannot uncompress MX domain: %s\n", strerror(errno));
				return -1;
			}
			printf("%s\tmail exchanger = %d %s\n", ns_rr_name(rr), n, dname);
			break;

		case ns_t_txt:
			if (rdlen < 1) {
				//printf("TXT record too short\n");
				return -1;
			}
			n = *(unsigned char *)ns_rr_rdata(rr);
			if (n > 0) {
				memset(dname, 0, sizeof(dname));
				memcpy(dname, ns_rr_rdata(rr) + 1, n);
				printf("%s\ttext = \"%s\"\n", ns_rr_name(rr), dname);
			}
			break;

		case ns_t_srv:
			if (rdlen < 6) {
				//printf("SRV record too short\n");
				return -1;
			}

			cp = ns_rr_rdata(rr);
			n = ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle),
			                       cp + 6, dname, sizeof(dname));

			if (n < 0) {
				//printf("Unable to uncompress domain: %s\n", strerror(errno));
				return -1;
			}

			printf("%s\tservice = %u %u %u %s\n", ns_rr_name(rr),
				ns_get16(cp), ns_get16(cp + 2), ns_get16(cp + 4), dname);
			break;

		case ns_t_soa:
			if (rdlen < 20) {
				dbg("SOA record too short:%d\n", rdlen);
				return -1;
			}

			printf("%s\n", ns_rr_name(rr));

			cp = ns_rr_rdata(rr);
			n = ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle),
			                       cp, dname, sizeof(dname));
			if (n < 0) {
				//printf("Unable to uncompress domain: %s\n", strerror(errno));
				return -1;
			}

			printf("\torigin = %s\n", dname);
			cp += n;

			n = ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle),
			                       cp, dname, sizeof(dname));
			if (n < 0) {
				//printf("Unable to uncompress domain: %s\n", strerror(errno));
				return -1;
			}

			printf("\tmail addr = %s\n", dname);
			cp += n;

			printf("\tserial = %lu\n", ns_get32(cp));
			cp += 4;

			printf("\trefresh = %lu\n", ns_get32(cp));
			cp += 4;

			printf("\tretry = %lu\n", ns_get32(cp));
			cp += 4;

			printf("\texpire = %lu\n", ns_get32(cp));
			cp += 4;

			printf("\tminimum = %lu\n", ns_get32(cp));
			break;

		default:
			break;
		}
	}

	return i;
}

/*
 * Function logic borrowed & modified from musl libc, res_msend.c
 * G.query_count is always > 0.
 */
static int send_queries(struct ns *ns)
{
	unsigned char reply[512];
	uint8_t rcode;
	len_and_sockaddr *local_lsa;
	struct pollfd pfd;
	int servfail_retry = 0;
	int n_replies = 0;
//	int save_idx = 0;
	unsigned retry_interval;
	unsigned timeout = G.default_timeout * 1000;
	unsigned tstart, tsent, tcur;

	pfd.events = POLLIN;
	pfd.fd = xsocket_type(&local_lsa, ns->lsa->u.sa.sa_family, SOCK_DGRAM);
	/*
	 * local_lsa has "null" address and port 0 now.
	 * bind() ensures we have a *particular port* selected by kernel
	 * and remembered in fd, thus later recv(fd)
	 * receives only packets sent to this port.
	 */
	xbind(pfd.fd, &local_lsa->u.sa, local_lsa->len);
	free(local_lsa);
	/* Make read/writes know the destination */
	xconnect(pfd.fd, &ns->lsa->u.sa, ns->lsa->len);
	ndelay_on(pfd.fd);

	retry_interval = timeout / G.default_retry;
	tstart = tcur = monotonic_ms();
	goto send;

	while (tcur - tstart < timeout) {
		int qn;
		int recvlen;

		if (tcur - tsent >= retry_interval) {
 send:
			for (qn = 0; qn < G.query_count; qn++) {
				if (G.query[qn].qlen == 0)
					continue; /* this one was replied already */

				if (write(pfd.fd, G.query[qn].query, G.query[qn].qlen) < 0) {
					bb_perror_msg("write to '%s'", ns->name);
					n_replies = -1; /* "no go, try next server" */
					goto ret;
				}
				dbg("query %u sent\n", qn);
			}
			tsent = tcur;
			servfail_retry = 2 * G.query_count;
		}

		/* Wait for a response, or until time to retry */
		if (poll(&pfd, 1, retry_interval - (tcur - tsent)) <= 0)
			goto next;

		recvlen = read(pfd.fd, reply, sizeof(reply));
		if (recvlen < 0) {
			bb_simple_perror_msg("read");
 next:
			tcur = monotonic_ms();
			continue;
		}

		if (ns->replies++ == 0) {
			printf("Server:\t\t%s\n", ns->name);
			printf("Address:\t%s\n\n",
				auto_string(xmalloc_sockaddr2dotted(&ns->lsa->u.sa))
			);
			/* In "Address", bind-utils-9.11.3 show port after a hash: "1.2.3.4#53" */
			/* Should we do the same? */
		}

		/* Non-identifiable packet */
		if (recvlen < 4) {
			dbg("read is too short:%d\n", recvlen);
			goto next;
		}

		/* Find which query this answer goes with, if any */
//		qn = save_idx;
		qn = 0;
		for (;;) {
			if (memcmp(reply, G.query[qn].query, 2) == 0) {
				dbg("response matches query %u\n", qn);
				break;
			}
			if (++qn >= G.query_count) {
				dbg("response does not match any query\n");
				goto next;
			}
		}

		if (G.query[qn].qlen == 0) {
			dbg("dropped duplicate response to query %u\n", qn);
			goto next;
		}

		rcode = reply[3] & 0x0f;
		dbg("query %u rcode:%s\n", qn, rcodes[rcode]);

		/* Retry immediately on SERVFAIL */
		if (rcode == 2) {
			//UNUSED: ns->failures++;
			if (servfail_retry) {
				servfail_retry--;
				write(pfd.fd, G.query[qn].query, G.query[qn].qlen);
				dbg("query %u resent\n", qn);
				goto next;
			}
		}

		/* Process reply */
		G.query[qn].qlen = 0; /* flag: "reply received" */
		tcur = monotonic_ms();
#if 1
		if (option_mask32 & OPT_debug) {
			printf("Query #%d completed in %ums:\n", qn, tcur - tstart);
		}
		if (rcode != 0) {
			printf("** server can't find %s: %s\n",
					G.query[qn].name, rcodes[rcode]);
			G.exitcode = EXIT_FAILURE;
		} else {
			switch (parse_reply(reply, recvlen)) {
			case -1:
				printf("*** Can't find %s: Parse error\n", G.query[qn].name);
				G.exitcode = EXIT_FAILURE;
				break;

			case 0:
				printf("*** Can't find %s: No answer\n", G.query[qn].name);
				break;
			}
		}
		bb_putchar('\n');
		n_replies++;
		if (n_replies >= G.query_count)
			goto ret;
#else
//used to store replies and process them later
		G.query[qn].latency = tcur - tstart;
		n_replies++;
		if (qn != save_idx) {
			/* "wrong" receive buffer, move to correct one */
			memcpy(G.query[qn].reply, G.query[save_idx].reply, recvlen);
			continue;
		}
		/* G.query[0..save_idx] have replies, move to next one, if exists */
		for (;;) {
			save_idx++;
			if (save_idx >= G.query_count)
				goto ret; /* all are full: we have all results */
			if (!G.query[save_idx].rlen)
				break; /* this one is empty */
		}
#endif
	} /* while() */

 ret:
	close(pfd.fd);

	return n_replies;
}

static void add_ns(const char *addr)
{
	struct ns *ns;
	unsigned count;

	dbg("%s: addr:'%s'\n", __func__, addr);

	count = G.serv_count++;

	G.server = xrealloc_vector(G.server, /*8=2^3:*/ 3, count);
	ns = &G.server[count];
	ns->name = addr;
	ns->lsa = xhost2sockaddr(addr, G.default_port);
	/*ns->replies = 0; - already is */
	/*ns->failures = 0; - already is */
}

static void parse_resolvconf(void)
{
	FILE *resolv;

	resolv = fopen("/etc/resolv.conf", "r");
	if (resolv) {
		char line[512];	/* "search" is defined to be up to 256 chars */

		while (fgets(line, sizeof(line), resolv)) {
			char *p, *arg;
			char *tokstate;

			p = strtok_r(line, " \t\n", &tokstate);
			if (!p)
				continue;
			dbg("resolv_key:'%s'\n", p);
			arg = strtok_r(NULL, "\n", &tokstate);
			dbg("resolv_arg:'%s'\n", arg);
			if (!arg)
				continue;

			if (strcmp(p, "domain") == 0) {
				/* domain DOM */
				if (!G.have_search_directive)
					goto set_search;
				continue;
			}
			if (strcmp(p, "search") == 0) {
				/* search DOM1 DOM2... */
				G.have_search_directive = 1;
 set_search:
				free(G.search);
				G.search = xstrdup(arg);
				dbg("search='%s'\n", G.search);
				continue;
			}

			if (strcmp(p, "nameserver") != 0)
				continue;

			/* nameserver DNS */
			add_ns(xstrdup(arg));
		}

		fclose(resolv);
	}

	if (!G.search) {
		/* default search domain is domain part of hostname */
		char *h = safe_gethostname();
		char *d = strchr(h, '.');
		if (d) {
			G.search = d + 1;
			dbg("search='%s' (from hostname)\n", G.search);
		}
		/* else free(h); */
	}

	/* Cater for case of "domain ." in resolv.conf */
	if (G.search && LONE_CHAR(G.search, '.'))
		G.search = NULL;
}

static void add_query(int type, const char *dname)
{
	struct query *new_q;
	unsigned count;
	ssize_t qlen;

	count = G.query_count++;

	G.query = xrealloc_vector(G.query, /*4=2^2:*/ 2, count);
	new_q = &G.query[count];

	dbg("new query#%u type %u for '%s'\n", count, type, dname);
	new_q->name = dname;

	qlen = res_mkquery(QUERY, dname, C_IN, type,
			/*data:*/ NULL, /*datalen:*/ 0,
			/*newrr:*/ NULL,
			new_q->query, sizeof(new_q->query)
	);
	new_q->qlen = qlen;
}

static void add_query_with_search(int type, const char *dname)
{
	char *s;

	if (type == T_PTR || !G.search || strchr(dname, '.')) {
		add_query(type, dname);
		return;
	}

	s = G.search;
	for (;;) {
		char *fullname, *e;

		e = skip_non_whitespace(s);
		fullname = xasprintf("%s.%.*s", dname, (int)(e - s), s);
		add_query(type, fullname);
		s = skip_whitespace(e);
		if (!*s)
			break;
	}
}

static char *make_ptr(const char *addrstr)
{
	unsigned char addr[16];

#if ENABLE_FEATURE_IPV6
	if (inet_pton(AF_INET6, addrstr, addr)) {
		if (memcmp(addr, v4_mapped, 12) != 0) {
			int i;
			char resbuf[80];
			char *ptr = resbuf;
			for (i = 0; i < 16; i++) {
				*ptr++ = 0x20 | bb_hexdigits_upcase[(unsigned char)addr[15 - i] & 0xf];
				*ptr++ = '.';
				*ptr++ = 0x20 | bb_hexdigits_upcase[(unsigned char)addr[15 - i] >> 4];
				*ptr++ = '.';
			}
			strcpy(ptr, "ip6.arpa");
			return xstrdup(resbuf);
		}
		return xasprintf("%u.%u.%u.%u.in-addr.arpa",
				addr[15], addr[14], addr[13], addr[12]);
	}
#endif

	if (inet_pton(AF_INET, addrstr, addr)) {
		return xasprintf("%u.%u.%u.%u.in-addr.arpa",
		        addr[3], addr[2], addr[1], addr[0]);
	}

	return NULL;
}

int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int nslookup_main(int argc UNUSED_PARAM, char **argv)
{
	unsigned types;
	int rc;
	int err;

	INIT_G();

	/* manpage: "Options can also be specified on the command line
	 * if they precede the arguments and are prefixed with a hyphen."
	 */
	types = 0;
	argv++;
	for (;;) {
		const char *options =
// bind-utils-9.11.3 accept these:
// class=   cl=
// type=    ty= querytype= query= qu= q=
// domain=  do=
// port=    po=
// timeout= t=
// retry=   ret=
// ndots=
// recurse
// norecurse
// defname
// nodefname
// vc
// novc
// debug
// nodebug
// d2
// nod2
// search
// nosearch
// sil
// fail
// nofail
// ver (prints version and exits)
			"type\0"      /* 0 */
			"querytype\0" /* 1 */
			"port\0"      /* 2 */
			"retry\0"     /* 3 */
			"debug\0"     /* 4 */
			"t\0" /* disambiguate with "type": else -t=2 fails */
			"timeout\0"   /* 6 */
			"";
		int i;
		char *arg;
		char *val;

		if (!*argv)
			bb_show_usage();
		if (argv[0][0] != '-')
			break;

		/* Separate out "=val" part */
		arg = (*argv++) + 1;
		val = strchrnul(arg, '=');
		if (*val)
			*val++ = '\0';

		i = index_in_substrings(options, arg);
		//bb_error_msg("i:%d arg:'%s' val:'%s'", i, arg, val);
		if (i < 0)
			bb_show_usage();

		if (i <= 1) {
			for (i = 0;; i++) {
				if (i == ARRAY_SIZE(qtypes))
					bb_error_msg_and_die("invalid query type \"%s\"", val);
				if (strcasecmp(qtypes[i].name, val) == 0)
					break;
			}
			types |= (1 << i);
			continue;
		}
		if (i == 2) {
			G.default_port = xatou_range(val, 1, 0xffff);
		}
		if (i == 3) {
			G.default_retry = xatou_range(val, 1, INT_MAX);
		}
		if (i == 4) {
			option_mask32 |= OPT_debug;
		}
		if (i > 4) {
			G.default_timeout = xatou_range(val, 1, INT_MAX / 1000);
		}
	}

	/* Use given DNS server if present */
	if (argv[1]) {
		if (argv[2])
			bb_show_usage();
		add_ns(argv[1]);
	} else {
		parse_resolvconf();
		/* Fall back to localhost if we could not find NS in resolv.conf */
		if (G.serv_count == 0)
			add_ns("127.0.0.1");
	}

	if (types == 0) {
		/* No explicit type given, guess query type.
		 * If we can convert the domain argument into a ptr (means that
		 * inet_pton() could read it) we assume a PTR request, else
		 * we issue A+AAAA queries and switch to an output format
		 * mimicking the one of the traditional nslookup applet.
		 */
		char *ptr;

		ptr = make_ptr(argv[0]);
		if (ptr) {
			add_query(T_PTR, ptr);
		} else {
			add_query_with_search(T_A, argv[0]);
#if ENABLE_FEATURE_IPV6
			add_query_with_search(T_AAAA, argv[0]);
#endif
		}
	} else {
		int c;
		for (c = 0; c < ARRAY_SIZE(qtypes); c++) {
			if (types & (1 << c))
				add_query_with_search(qtypes[c].type, argv[0]);
		}
	}

	for (rc = 0; rc < G.serv_count;) {
		int c;

		c = send_queries(&G.server[rc]);
		if (c > 0) {
			/* more than zero replies received */
#if 0 /* which version does this? */
			if (option_mask32 & OPT_debug) {
				printf("Replies:\t%d\n", G.server[rc].replies);
				printf("Failures:\t%d\n\n", G.server[rc].failures);
			}
#endif
			break;
//FIXME: we "break" even though some queries may still be not answered, and other servers may know them?
		}
		/* c = 0: timed out waiting for replies */
		/* c < 0: error (message already printed) */
		rc++;
		if (rc >= G.serv_count) {
//
// NB: bind-utils-9.11.3 behavior (all to stdout, not stderr):
//
// $ nslookup gmail.com 8.8.8.8
// ;; connection timed out; no servers could be reached
//
// Using TCP mode:
// $ nslookup -vc gmail.com 8.8.8.8; echo EXITCODE:$?
//     <~10 sec>
// ;; Connection to 8.8.8.8#53(8.8.8.8) for gmail.com failed: timed out.
//     <~10 sec>
// ;; Connection to 8.8.8.8#53(8.8.8.8) for gmail.com failed: timed out.
//     <~10 sec>
// ;; connection timed out; no servers could be reached
// ;; Connection to 8.8.8.8#53(8.8.8.8) for gmail.com failed: timed out.
//     <empty line>
// EXITCODE:1
// $ _
			printf(";; connection timed out; no servers could be reached\n\n");
			return EXIT_FAILURE;
		}
	}

	err = 0;
	for (rc = 0; rc < G.query_count; rc++) {
		if (G.query[rc].qlen) {
			printf("*** Can't find %s: No answer\n", G.query[rc].name);
			err = 1;
		}
	}
	if (err) /* should this affect exicode too? */
		bb_putchar('\n');

	if (ENABLE_FEATURE_CLEAN_UP) {
		free(G.server);
		free(G.query);
	}

	return G.exitcode;
}

#endif