summaryrefslogtreecommitdiff
path: root/common/snmp-engine.c
blob: 0c1aa87a589657582e55add14e711100aeb467aa (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
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
/*
 * Copyright (c) 2008, Stefan Walter
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *     * Redistributions of source code must retain the above
 *       copyright notice, this list of conditions and the
 *       following disclaimer.
 *     * Redistributions in binary form must reproduce the
 *       above copyright notice, this list of conditions and
 *       the following disclaimer in the documentation and/or
 *       other materials provided with the distribution.
 *     * The names of contributors to this software may not be
 *       used to endorse or promote products derived from this
 *       software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 *
 * CONTRIBUTORS
 *  Stef Walter <stef@memberwebs.com>
 *
 */

#include "usuals.h"

#include "async-resolver.h"
#include "hash.h"
#include "log.h"
#include "server-mainloop.h"
#include "snmp-engine.h"
#include "sock-any.h"

#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <unistd.h>
#include <syslog.h>
#include <err.h>
#include <arpa/inet.h>

#include <bsnmp/asn1.h>
#include <bsnmp/snmp.h>
#include <mib/mib-parser.h>

struct host;
struct request;

typedef uint64_t mstime;

/* ------------------------------------------------------------------------------
 * HOSTS
 */

struct host {
	/* The hash key is hostname:options:community */
	char key[128];

	char *hostname;
	char *community;
	int version;

	mstime interval;

	/* Host resolving and book keeping */
	struct sockaddr_any address;
	mstime resolve_interval;
	mstime last_resolve_try;
	mstime last_resolved;
	int is_resolved;
	int is_resolving;
	int must_resolve;

	/* Requests that are queued of this host */
	struct request *prepared;

	/* Next in list of hosts */
	struct host *next;
};

/* All hosts we've allocated */
static struct host *host_list = NULL;

/* Hosts hashed by the host:version:community string */
static hsh_t *host_by_key = NULL;

static void
resolve_cb (int ecode, struct addrinfo* ai, void* arg)
{
	struct host *host = (struct host*)arg;
	host->is_resolving = 0;

	if (ecode) {
		log_warnx ("couldn't resolve host name: %s: %s",
		           host->hostname, gai_strerror (ecode));
		return;
	}

	/* A successful resolve */
	memcpy (&SANY_ADDR (host->address), ai->ai_addr, ai->ai_addrlen);
	SANY_LEN (host->address) = ai->ai_addrlen;
	host->last_resolved = server_get_time ();
	host->is_resolved = 1;

	log_debug ("resolved host: %s", host->hostname);
}

static void
host_resolve (struct host *host, mstime when)
{
	struct addrinfo hints;

	if (host->is_resolving)
		return;

	memset (&hints, 0, sizeof (hints));
	hints.ai_family = PF_UNSPEC;
	hints.ai_socktype = SOCK_DGRAM;

	/* Automatically strips port number */
	log_debug ("resolving host: %s", host->hostname);
	host->last_resolve_try = when;
	host->is_resolving = 0;
	async_resolver_queue (host->hostname, "161", &hints, resolve_cb, host);
}

static int
host_resolve_timer (mstime when, void* arg)
{
	struct host* h;

	/* Go through hosts and see which ones need resolving */
	for (h = host_list; h; h = h->next) {

		/* No need to resolve? */
		if (!h->must_resolve)
			continue;

		ASSERT (h->resolve_interval);

		if (when - h->resolve_interval > h->last_resolve_try)
			host_resolve (h, when);

		/* When the last 3 resolves have failed, set to unresolved */
		if (h->is_resolved && when - (h->resolve_interval * 3) > h->last_resolved) {
			log_debug ("host address expired, and was not resolved: %s", h->hostname);
			h->is_resolved = 0;
		}
	}

	return 1;
}

static void
host_update_interval (struct host *host, mstime interval)
{
	mstime resint;

	if (!host->must_resolve)
		return;

	/* When less than three minutes, resolve once per minute */
	if (interval <= 180000)
		resint = 60000;

	/* When between 3 and 10 minutes resolve once per cycle */
	else if(interval <= 600000)
		resint = interval;

	/* Otherwise resolve thrice per cycle */
	else
		resint = interval / 3;

        /* The lowest interval (since hosts can be shared by pollers) wins */
	if (!host->resolve_interval || host->resolve_interval > resint) {
		host->resolve_interval = resint;
		log_debug ("will resolve host '%s' every %d seconds", host->hostname, resint / 1000);
	}
}

static struct host*
host_instance (const char *hostname, const char *community, int version, mstime interval)
{
	struct host *host;
	char key[128];
	int r, initialize;

	ASSERT (hostname);
	initialize = 0;

	/*
	 * Build a lookup key. We can only combine requests for the same
	 * host when the version and community match.
	 */
	community = community ? community : "public";
	snprintf (key, sizeof(key), "%s:%d:%s", hostname, version, community);
	key[sizeof(key) - 1] = 0;

	/* See if we can find an associated host */
	host = hsh_get (host_by_key, key, -1);
	if (!host) {

		host = calloc (1, sizeof (struct host));
		if (!host) {
			log_errorx ("out of memory");
			return NULL;
		}

		/* Try and resolve the DNS name */
		r = sock_any_pton (hostname, &host->address, SANY_OPT_DEFPORT(161) | SANY_OPT_DEFLOCAL |
		                   SANY_OPT_NORESOLV);
		if (r == -1) {
			log_warn ("couldn't parse host address (ignoring): %s", hostname);
			free (host);
			return NULL;
		}

		/* And into the hash table */
		memcpy (&host->key, key, sizeof (host->key));
		if (!hsh_set (host_by_key, host->key, -1, host)) {
			log_errorx ("out of memory");
			free (host);
			return NULL;
		}

		/* And add it to the list */
		host->next = host_list;
		host_list = host;

		/*
		 * If we got back SANY_AF_DNS, then it needs resolving. The actual
		 * interval and stuff are worked out in once all the hosts, polls etc...
		 * have been parsed.
		 */
		host->must_resolve = (r == SANY_AF_DNS);
		host->is_resolved = (r != SANY_AF_DNS);

		host->version = version;
		host->hostname = strdup (hostname);
		host->community = strdup (community);
		host->resolve_interval = 0;
		host->last_resolved = 0;
		host->last_resolve_try = 0;

		/* Start the resolving process */
		if (!host->is_resolved)
			host_resolve (host, server_get_time ());
	}

	/* Update the host's resolve interval based on the poll interval requested */
	host_update_interval (host, interval);

	return host;
}

static void
host_initialize (void)
{
	/* Initialize stuff if necessary */
	host_by_key = hsh_create ();
	if (!host_by_key)
		err (1, "out of memory");

	/* resolve timer goes once per second */
	if (server_timer (1000, host_resolve_timer, NULL) == -1)
		err (1, "couldn't setup resolve timer");
}

static void
host_cleanup (void)
{
	struct host *next, *host;

	if (host_by_key)
		hsh_free (host_by_key);
	host_by_key = NULL;

	for (host = host_list; host; host = next) {
		next = host->next;
	        if (host->hostname)
			free (host->hostname);
		if (host->community)
			free (host->community);
		free (host);
	}

	host_list = NULL;
}

/* ------------------------------------------------------------------------------
 * ASYNC REQUEST PROCESSING
 */

#define MAKE_REQUEST_ID(snmp, cb) \
	((((snmp) & 0xFFFFFF) << 8) | (cb & 0xFF))
#define REQUEST_ID_SNMP(id) \
	((id) >> 8)
#define REQUEST_ID_CB(id) \
	((id) & 0xFF)

struct request
{
	/* The SNMP request identifier */
	uint snmp_id;

	/* References, useful since we have callbacks */
	int refs;

	mstime next_send;         /* Time of the next packet send */
	mstime last_sent;         /* Time last sent */
	mstime retry_interval;    /* How long between retries */
	mstime when_timeout;      /* When this request times out */
	uint num_sent;            /* How many times we've sent */

	struct host *host;        /* Host associated with this request */

	/* One callback entry for each binding */
	struct {
		snmp_response func;
		void *arg;
	} callbacks[SNMP_MAX_BINDINGS];

	/* The actual request data */
	struct snmp_pdu pdu;
};

/* The number of SNMP packet retries */
static int snmp_retries = 3;

/* The last request id */
static uint snmp_request_id = 1;

/* The SNMP socket we're communicating on */
static int snmp_socket = -1;

/* Since we only deal with one packet at a time, global buffer */
static unsigned char snmp_buffer[0x1000];

/* Hash table of all requests being processed */
static hsh_t *snmp_processing = NULL;

/* Hash table of all requests being prepared */
static hsh_t *snmp_preparing = NULL;

/* A flush of prepared packets is pending */
static int snmp_flush_pending = 0;

static void
request_release (struct request *req)
{
	/* It should no longer be referred to any of these places */
	ASSERT (!hsh_get (snmp_preparing, &req->snmp_id, sizeof (req->snmp_id)));
	ASSERT (!hsh_get (snmp_processing, &req->snmp_id, sizeof (req->snmp_id)));

	snmp_pdu_clear (&req->pdu);
	free (req);
}

static void
request_send (struct request* req, mstime when)
{
	struct asn_buf b;
	ssize_t ret;

	ASSERT (snmp_socket != -1);

	/* Update our bookkeeping */
	req->num_sent++;
	if (req->num_sent <= snmp_retries)
		req->next_send = when + req->retry_interval;
	else
		req->next_send = 0;
	req->last_sent = when;

	if (!req->host->is_resolved) {
		if (req->num_sent <= 1)
			log_debug ("skipping snmp request: host not resolved: %s",
			           req->host->hostname);
		return;
	}

	b.asn_ptr = snmp_buffer;
	b.asn_len = sizeof (snmp_buffer);

	if (snmp_pdu_encode (&req->pdu, &b)) {
		log_error("couldn't encode snmp buffer");
	} else {
		ret = sendto (snmp_socket, snmp_buffer, b.asn_ptr - snmp_buffer, 0,
		              &SANY_ADDR (req->host->address), SANY_LEN (req->host->address));
		if (ret == -1)
			log_error ("couldn't send snmp packet to: %s", req->host->hostname);
		else
			log_debug ("sent request #%d to: %s", req->snmp_id, req->host->hostname);
	}
}

static void
request_failure (struct request *req, int code)
{
	void *val;
	int j;

	ASSERT (req);
	ASSERT (code != 0);
	ASSERT (hsh_get (snmp_processing, &req->snmp_id, sizeof (req->snmp_id)) == req);

	log_debug ("failed request #%d to '%s' with code %d", req->snmp_id, req->host->hostname, code);

	/* For each request SNMP value... */
	for (j = 0; j < req->pdu.nbindings; ++j) {

		if (!req->callbacks[j].func)
			continue;

		/* ... let callback know */
		(req->callbacks[j].func) (MAKE_REQUEST_ID (req->snmp_id, j),
				          code, NULL, req->callbacks[j].arg);

		/*
		 * Request could have been freed by the callback, by calling the cancel
		 * function, check and bail if so.
		 */
		if (hsh_get (snmp_processing, &req->snmp_id, sizeof (req->snmp_id)) != req)
			return;
	}

	/* Remove from the processing list */
	val = hsh_rem (snmp_processing, &req->snmp_id, sizeof (req->snmp_id));
	ASSERT (val == req);

	/* And free the request */
	request_release (req);
}

static void
request_get_dispatch (struct request* req, struct snmp_pdu* pdu)
{
	struct snmp_value* pvalue;
	struct snmp_value* rvalue;
	int i, j, skipped, processed;
	void *val;

	ASSERT (req);
	ASSERT (pdu);
	ASSERT (req->snmp_id == pdu->request_id);
	ASSERT (pdu->error_status == SNMP_ERR_NOERROR);
	ASSERT (req->pdu.type == SNMP_PDU_GET);
	ASSERT (hsh_get (snmp_processing, &req->snmp_id, sizeof (req->snmp_id)) == req);

	/*
	 * For SNMP GET requests we check that the values that came back
	 * were in fact for the same values we requested, and fix any
	 * ordering issues etc.
	 */
	skipped = 0;
	for (j = 0; j < SNMP_MAX_BINDINGS; ++j) {

		if (!req->callbacks[j].func)
			continue;

		rvalue = &(req->pdu.bindings[j]);
		processed = 0;

		/* ... dig out matching value from response */
		for (i = 0; i < pdu->nbindings; ++i) {
			pvalue = &(pdu->bindings[i]);

			if (asn_compare_oid (&(rvalue->var), &(pvalue->var)) != 0)
				continue;

			(req->callbacks[j].func) (MAKE_REQUEST_ID (req->snmp_id, j),
			                          SNMP_ERR_NOERROR, pvalue, req->callbacks[j].arg);

			/*
			 * Request could have been freed by the callback, by calling the cancel
			 * function, check and bail if so.
			 */
			if (hsh_get (snmp_processing, &req->snmp_id, sizeof (req->snmp_id)) != req)
				return;

			req->callbacks[j].func = NULL;
			processed = 1;
			break;
		}

		/* Make note that we didn't find a match for at least one binding */
		if (!processed && !skipped)
			skipped = 1;
	}

	/* All done? then remove request */
	if (!skipped) {

		log_debug ("request #%d is complete", req->snmp_id);

		val = hsh_rem (snmp_processing, &req->snmp_id, sizeof (req->snmp_id));
		ASSERT (val == req);
		request_release (req);
	}
}

static void
request_other_dispatch (struct request* req, struct snmp_pdu* pdu)
{
	void *val;

	ASSERT (req);
	ASSERT (pdu);
	ASSERT (req->snmp_id == pdu->request_id);
	ASSERT (pdu->error_status == SNMP_ERR_NOERROR);
	ASSERT (req->pdu.type != SNMP_PDU_GET);

	/*
	 * For requests other than GET we just use the first value
	 * that was sent. See below where we limit to one binding
	 * per SNMP request when other than GET.
	 */

	if (pdu->nbindings == 0) {
		log_warn ("received response from the server without any values");
		return;
	}

	if (pdu->nbindings > 1)
		log_warn ("received response from the server with extra values");

	/* Shouldn't have sent more than one binding */
	ASSERT (req->pdu.nbindings == 1);

	if (req->callbacks[0].func)
		(req->callbacks[0].func) (MAKE_REQUEST_ID (req->snmp_id, 0), SNMP_ERR_NOERROR,
				          &(pdu->bindings[0]), req->callbacks[0].arg);

	log_debug ("request #%d is complete", req->snmp_id);

	val = hsh_rem (snmp_processing, &req->snmp_id, sizeof (req->snmp_id));
	ASSERT (val == req);
	request_release (req);
}

static void
request_response (int fd, int type, void* arg)
{
	char hostname[MAXPATHLEN];
	struct sockaddr_any from;
	struct snmp_pdu pdu;
	struct asn_buf b;
	struct request* req;
	const char* msg;
	int len, ret;
	int ip, id;

	ASSERT (snmp_socket == fd);

	/* Read in the packet */

	SANY_LEN (from) = sizeof (from);
	len = recvfrom (snmp_socket, snmp_buffer, sizeof (snmp_buffer), 0,
	                &SANY_ADDR (from), &SANY_LEN (from));
	if(len < 0) {
		if(errno != EAGAIN && errno != EWOULDBLOCK)
			log_error ("error receiving snmp packet from network");
		return;
	}

	if (sock_any_ntop (&from, hostname, MAXPATHLEN, 0) == -1)
		strcpy(hostname, "[UNKNOWN]");

	/* Now parse the packet */

	b.asn_ptr = snmp_buffer;
	b.asn_len = len;

	ret = snmp_pdu_decode(&b, &pdu, &ip);
	if (ret != SNMP_CODE_OK) {
		log_warnx ("invalid snmp packet received from: %s", hostname);
		return;
	}

	/* It needs to match something we're waiting for */
	id = pdu.request_id;
	req = hsh_get (snmp_processing, &id, sizeof (id));
	if(!req) {
		log_debug ("received extra, cancelled or delayed packet from: %s", hostname);
		return;
	}

	if(pdu.version != req->pdu.version)
		log_warnx ("wrong version snmp packet from: %s", hostname);


	/* Log any errors */
	if(pdu.error_status == SNMP_ERR_NOERROR) {
		log_debug ("response to request #%d from: %s", req->snmp_id, hostname);

		if (req->pdu.type == SNMP_PDU_GET)
			request_get_dispatch (req, &pdu);
		else
			request_other_dispatch (req, &pdu);

	} else {
		msg = snmp_get_errmsg (pdu.error_status);
		if(msg)
			log_debug ("failure for request #%d from: %s: %s", req->snmp_id, hostname, msg);
		else
			log_debug ("failure for request #%d from: %s: %d", req->snmp_id, hostname,
			           pdu.error_status);
		request_failure (req, pdu.error_status);
	}

}

static void
request_process_all (mstime when)
{
	struct request *req;
	hsh_index_t *i;

	/* Go through all processing packets */
	for (i = hsh_first (snmp_processing); i; ) {

		req = hsh_this (i, NULL, NULL);
		ASSERT (req);

		/* Move to the next, as we may delete below */
		i = hsh_next (i);

		if (when >= req->when_timeout) {
			request_failure (req, -1);
			continue;
		}

		if (req->next_send && when >= req->next_send)
			request_send (req, when);
	}
}

static int
request_resend_timer (mstime when, void* arg)
{
	request_process_all (when);
	return 1;
}

static void
request_flush (struct request *req, mstime when)
{
	void *val;

	ASSERT (req->host->prepared == req);

	val = hsh_rem (snmp_preparing, &req->snmp_id, sizeof (req->snmp_id));
	ASSERT (val == req);

	/* Don't let us add more onto this request via the host */
	ASSERT (req->host->prepared == req);
	req->host->prepared = NULL;

	/* Mark this packet to be sent now */
	req->next_send = when;

	if (!hsh_set (snmp_processing, &req->snmp_id, sizeof (req->snmp_id), req)) {
		log_errorx ("out of memory, discarding packets");
		request_release (req);
	}
}

static void
request_flush_all (mstime when)
{
	struct request *req;
	hsh_index_t *i;

	/* Transfer everything to the processing table */
	for (i = hsh_first (snmp_preparing); i; ) {
		req = hsh_this (i, NULL, NULL);

		/* Do this here, because below removes from table */
		i = hsh_next (i);

		request_flush (req, when);
	}

	/* Clear the preparing table */
	hsh_clear (snmp_preparing);

	/* Process all packets in processing */
	request_process_all (when);
}



static int
request_flush_cb (mstime when, void *arg)
{
	snmp_flush_pending = 0;
	request_flush_all (when);
	return 0;
}

static struct request*
request_prep_instance (struct host *host, mstime interval, mstime timeout, int reqtype)
{
	struct request *req;

	/* See if we have one we can piggy back onto */
	req = host->prepared;
	if (req) {
		ASSERT (hsh_get (snmp_preparing, &req->snmp_id, sizeof (req->snmp_id)));

		/* We have one we can piggy back another request onto */
		if (req->pdu.nbindings < SNMP_MAX_BINDINGS && req->pdu.type == reqtype)
			return req;

		/* It's too full, so send it off */
		request_flush (req, server_get_time ());
		req = NULL;
	}

	ASSERT (host->prepared == NULL);

	/* Create a new request */
	req = calloc (1, sizeof (struct request));
	if (!req) {
		log_error ("out of memory");
		return NULL;
	}

	/* Assign the unique id */
	req->snmp_id = snmp_request_id++;

	/* Roll around after a decent amount of ids */
	if (snmp_request_id >= 0xFFFFFF)
		snmp_request_id = 1;

	/* Mark it down as something we want to prepare */
	if (!hsh_set (snmp_preparing, &req->snmp_id, sizeof (req->snmp_id), req)) {
		log_error ("out of memory");
		free (req);
		return NULL;
	}

        /* Setup the packet */
        strlcpy (req->pdu.community, host->community, sizeof (req->pdu.community));
        req->pdu.request_id = req->snmp_id;
        req->pdu.version = host->version;
        req->pdu.type = reqtype;
        req->pdu.error_status = 0;
        req->pdu.error_index = 0;
        req->pdu.nbindings = 0;

        /* Send interval is 200 ms when poll interval is below 2 seconds */
        req->retry_interval = (interval <= 2000) ? 200L : 600L;

        /* Timeout is for the last packet sent, not first */
        req->when_timeout = server_get_time () + (req->retry_interval * ((mstime)snmp_retries)) + timeout;
        req->num_sent = 0;

        /* Add it to the host */
	req->host = host;
	ASSERT (host->prepared == NULL);
        host->prepared = req;

        log_debug ("preparing request #%d for: %s@%s", req->snmp_id,
                   req->host->community, req->host->hostname);

	return req;
}

int
snmp_engine_request (const char *hostname, const char *community, int version,
                     mstime interval, mstime timeout, int reqtype,
                     struct asn_oid *oid, snmp_response func, void *arg)
{
	struct host *host;
	struct request *req;
	int callback_id;

	ASSERT (func);

	/* Lookup host for request */
	host = host_instance (hostname, community, version, interval);
	if (!host)
		return 0;

	/* Get a request with space or a new request for that host */
	req = request_prep_instance (host, interval, timeout, reqtype);
	if (!req)
		return 0;

	ASSERT (req->pdu.nbindings < SNMP_MAX_BINDINGS);

	/* Add the oid to that request */
	callback_id = req->pdu.nbindings;
        req->pdu.bindings[callback_id].var = *oid;
        req->pdu.bindings[callback_id].syntax = SNMP_SYNTAX_NULL;
        req->callbacks[callback_id].func = func;
        req->callbacks[callback_id].arg = arg;
        req->pdu.nbindings++;

        /* All other than GET, only get one binding */
        if (reqtype != SNMP_PDU_GET) {
        	ASSERT (req->pdu.nbindings == 1);
        	request_flush (req, server_get_time ());
        }

        /* Otherwise flush on the idle callback */
        else if (!snmp_flush_pending) {
        	server_oneshot (0, request_flush_cb, NULL);
        	snmp_flush_pending = 1;
        }

        return MAKE_REQUEST_ID (req->snmp_id, callback_id);
}

void
snmp_engine_cancel (int id)
{
	struct request *req;
	int snmp_id, callback_id, i;
	const char *during;

	ASSERT (id);

	snmp_id = REQUEST_ID_SNMP (id);
	callback_id = REQUEST_ID_CB (id);

	ASSERT (snmp_id > 0 && snmp_id < 0xFFFFFF);
	ASSERT (callback_id >= 0 && callback_id < SNMP_MAX_BINDINGS);

	/* Is it being processed? */
	req = hsh_rem (snmp_processing, &snmp_id, sizeof (snmp_id));
	if (req) {
		during = "processing";

	/* Is it being prepared? */
	} else {
		req = hsh_rem (snmp_preparing, &snmp_id, sizeof (snmp_id));
		if (req) {
			during = "prep";
			ASSERT (req->host->prepared == req);
		}
	}

	if (!req)
		return;

	/* Remove this callback from the request */
	req->callbacks[callback_id].func = NULL;
	req->callbacks[callback_id].arg = NULL;

	/* See if any callbacks exist in the request */
	for (i = 0; i < SNMP_MAX_BINDINGS; ++i) {
		if (req->callbacks[i].func)
			return;
	}

	/* If not, free the request */
	log_debug ("cancelling request #%d during %s", snmp_id, during);
	if (req->host->prepared == req)
		req->host->prepared = NULL;
	request_release (req);
}

void
snmp_engine_flush (void)
{
	request_flush_all (server_get_time ());
}

/* -------------------------------------------------------------------------------
 * SYNC REQUESTS
 */

struct sync_data {
	int valid;
	int code;
	int id;
	struct snmp_value *dest;
};

static void
sync_response (int req, int code, struct snmp_value *value, void *data)
{
	struct sync_data *sync = data;

	ASSERT (req == sync->id);

	sync->valid = 1;
	sync->code = code;
	if (value)
		snmp_value_copy (sync->dest, value);

	server_stop ();
}

int
snmp_engine_sync (const char* host, const char* community, int version,
                  uint64_t interval, uint64_t timeout, int reqtype,
                  struct snmp_value *value)
{
	struct sync_data sync;

	/* Can't run a sync request with the server running */
	ASSERT (server_stopped());

	sync.valid = 0;
	sync.code = 0;
	sync.dest = value;

	sync.id = snmp_engine_request (host, community, version, interval, timeout,
	                               reqtype, &value->var, sync_response, &sync);

	if (!sync.id)
		return -1;

	snmp_engine_flush ();
	server_run ();

	ASSERT (sync.valid);
	return sync.code;
}

/* -----------------------------------------------------------------------------
 * INIT
 */

void
snmp_engine_init (const char *bindaddr, int retries)
{
	struct sockaddr_any addr;

	snmp_retries = retries;

	snmp_processing = hsh_create ();
	if (!snmp_processing)
		err (1, "out of memory");

	snmp_preparing = hsh_create ();
	if (!snmp_preparing)
		err (1, "out of memory");

	memset (&addr, 0, sizeof(addr));
	if (!bindaddr)
		bindaddr = "0.0.0.0";
	if (sock_any_pton (bindaddr, &addr, SANY_OPT_DEFPORT (0) | SANY_OPT_DEFANY) < 0)
		err (1, "couldn't parse bind address: %s", bindaddr);

	ASSERT (snmp_socket == -1);
	snmp_socket = socket (SANY_TYPE (addr), SOCK_DGRAM, 0);
	if (snmp_socket < 0)
		err (1, "couldn't open snmp socket");

	if (bind (snmp_socket, &SANY_ADDR (addr), SANY_LEN (addr)) < 0)
		err (1, "couldn't listen on port");

	if (server_watch (snmp_socket, SERVER_READ, request_response, NULL) == -1)
		err (1, "couldn't listen on socket");

	/* We fire off the resend timer every 1/5 second */
	if (server_timer (200, request_resend_timer, NULL) == -1)
	    err(1, "couldn't setup timer");

	host_initialize ();
}

void
snmp_engine_stop (void)
{
	if (snmp_socket != -1) {
		server_unwatch (snmp_socket);
		close (snmp_socket);
		snmp_socket = -1;
	}

	host_cleanup ();
}

int
snmp_engine_match (const struct snmp_value *value, const char *text)
{
	char *end;

	ASSERT (value);
	ASSERT (text);

	switch (value->syntax) {

	/* Empty string */
	case SNMP_SYNTAX_NULL:
	case SNMP_SYNTAX_NOSUCHOBJECT:
	case SNMP_SYNTAX_NOSUCHINSTANCE:
	case SNMP_SYNTAX_ENDOFMIBVIEW:
		return *text == '\0';

	/* Integer value */
	case SNMP_SYNTAX_INTEGER:
		{
			int num = strtoll (text, &end, 0);
			if (*end != '\0')
				return 0;
			return num == value->v.integer;
		}

	/* String of bytes */
	case SNMP_SYNTAX_OCTETSTRING:
		{
			int len = strlen (text);
			if (value->v.octetstring.len != len)
				return 0;
			return memcmp (value->v.octetstring.octets, text, len) == 0;
		}


	case SNMP_SYNTAX_OID:
		{
			struct asn_oid oid;
			if (mib_parse (text, &oid) < 0)
				return 0;
			return asn_compare_oid (&oid, &value->v.oid) == 0;
		}

	case SNMP_SYNTAX_IPADDRESS:
		{
		    struct in_addr addr;
		    if (!inet_aton (text, &addr))
			    return 0;
		    return memcmp (&addr, value->v.ipaddress, 4) == 0;
		}

	case SNMP_SYNTAX_COUNTER:
	case SNMP_SYNTAX_GAUGE:
	case SNMP_SYNTAX_TIMETICKS:
		{
			uint64_t sub = strtoull (text, &end, 0);
			if (*end != '\0' || sub > 0xffffffff)
				return 0;
			return sub == value->v.uint32;
		}

	case SNMP_SYNTAX_COUNTER64:
		{
			uint64_t sub = strtoull (text, &end, 0);
			if (*end != '\0' || sub > 0xffffffff)
				return 0;
			return sub == value->v.counter64;
		}

	default:
		return 0;
	};
}