-
Notifications
You must be signed in to change notification settings - Fork 3
/
evdns.c
5664 lines (5014 loc) · 159 KB
/
evdns.c
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
/* Copyright 2006-2007 Niels Provos
* Copyright 2007-2012 Nick Mathewson and Niels Provos
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/
/* Based on software by Adam Langly. Adam's original message:
*
* Async DNS Library
* Adam Langley <[email protected]>
* http://www.imperialviolet.org/eventdns.html
* Public Domain code
*
* This software is Public Domain. To view a copy of the public domain dedication,
* visit http://creativecommons.org/licenses/publicdomain/ or send a letter to
* Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
*
* I ask and expect, but do not require, that all derivative works contain an
* attribution similar to:
* Parts developed by Adam Langley <[email protected]>
*
* You may wish to replace the word "Parts" with something else depending on
* the amount of original code.
*
* (Derivative works does not include programs which link against, run or include
* the source verbatim in their source distributions)
*
* Version: 0.1b
*/
#include "event2/event-config.h"
#include "evconfig-private.h"
#include <sys/types.h>
#ifndef _FORTIFY_SOURCE
#define _FORTIFY_SOURCE 3
#endif
#include <string.h>
#include <fcntl.h>
#ifdef EVENT__HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#ifdef EVENT__HAVE_STDINT_H
#include <stdint.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#ifdef EVENT__HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <limits.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdarg.h>
#ifdef _WIN32
#include <winsock2.h>
#include <winerror.h>
#include <ws2tcpip.h>
#ifndef _WIN32_IE
#define _WIN32_IE 0x400
#endif
#include <shlobj.h>
#endif
#include "event2/buffer.h"
#include "event2/bufferevent.h"
#include "event2/dns.h"
#include "event2/dns_struct.h"
#include "event2/dns_compat.h"
#include "event2/util.h"
#include "event2/event.h"
#include "event2/event_struct.h"
#include "event2/listener.h"
#include "event2/thread.h"
#include "defer-internal.h"
#include "log-internal.h"
#include "mm-internal.h"
#include "strlcpy-internal.h"
#include "ipv6-internal.h"
#include "util-internal.h"
#include "evthread-internal.h"
#ifdef _WIN32
#include <ctype.h>
#include <winsock2.h>
#include <windows.h>
#include <iphlpapi.h>
#include <io.h>
#else
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#endif
#ifdef EVENT__HAVE_NETINET_IN6_H
#include <netinet/in6.h>
#endif
#define EVDNS_LOG_DEBUG EVENT_LOG_DEBUG
#define EVDNS_LOG_WARN EVENT_LOG_WARN
#define EVDNS_LOG_MSG EVENT_LOG_MSG
#ifndef HOST_NAME_MAX
#define HOST_NAME_MAX 255
#endif
#include <stdio.h>
#undef MIN
#undef MAX
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))
#define ASSERT_VALID_REQUEST(req) \
EVUTIL_ASSERT((req)->handle && (req)->handle->current_req == (req))
#define u64 ev_uint64_t
#define u32 ev_uint32_t
#define u16 ev_uint16_t
#define u8 ev_uint8_t
/* maximum number of addresses from a single packet */
/* that we bother recording */
#define MAX_V4_ADDRS 32
#define MAX_V6_ADDRS 32
/* Maximum allowable size of a DNS message over UDP without EDNS.*/
#define DNS_MAX_UDP_SIZE 512
/* Maximum allowable size of a DNS message over UDP with EDNS.*/
#define EDNS_MAX_UDP_SIZE 65535
#define EDNS_ENABLED(base) \
(((base)->global_max_udp_size) > DNS_MAX_UDP_SIZE)
#define TYPE_A EVDNS_TYPE_A
#define TYPE_CNAME 5
#define TYPE_PTR EVDNS_TYPE_PTR
#define TYPE_SOA EVDNS_TYPE_SOA
#define TYPE_AAAA EVDNS_TYPE_AAAA
#define TYPE_OPT 41
#define CLASS_INET EVDNS_CLASS_INET
/* Timeout in seconds for idle TCP connections that server keeps alive. */
#define SERVER_IDLE_CONN_TIMEOUT 10
/* Timeout in seconds for idle TCP connections that client keeps alive. */
#define CLIENT_IDLE_CONN_TIMEOUT 5
/* Default maximum number of simultaneous TCP client connections that DNS server can hold. */
#define MAX_CLIENT_CONNECTIONS 10
/* Persistent handle. We keep this separate from 'struct request' since we
* need some object to last for as long as an evdns_request is outstanding so
* that it can be canceled, whereas a search request can lead to multiple
* 'struct request' instances being created over its lifetime. */
struct evdns_request {
struct request *current_req;
struct evdns_base *base;
int pending_cb; /* Waiting for its callback to be invoked; not
* owned by event base any more. */
/* elements used by the searching code */
int search_index;
struct search_state *search_state;
char *search_origname; /* needs to be free()ed */
int search_flags;
u16 tcp_flags;
};
struct request {
u8 *request; /* the dns packet data */
u16 request_size; /* size of memory block stored in request field */
u8 request_type; /* TYPE_PTR or TYPE_A or TYPE_AAAA */
unsigned int request_len;
int reissue_count;
int tx_count; /* the number of times that this packet has been sent */
void *user_pointer; /* the pointer given to us for this request */
evdns_callback_type user_callback;
struct nameserver *ns; /* the server which we last sent it */
/* these objects are kept in a circular list */
/* XXX We could turn this into a CIRCLEQ. */
struct request *next, *prev;
struct event timeout_event;
u16 trans_id; /* the transaction id */
unsigned request_appended :1; /* true if the request pointer is data which follows this struct */
unsigned transmit_me :1; /* needs to be transmitted */
/* XXXX This is a horrible hack. */
char **put_cname_in_ptr; /* store the cname here if we get one. */
struct evdns_base *base;
struct evdns_request *handle;
};
struct reply {
unsigned int type;
unsigned int have_answer : 1;
u32 rr_count;
union {
u32 *a;
struct in6_addr *aaaa;
char *ptr_name;
void *raw;
} data;
};
enum tcp_state {
TS_DISCONNECTED,
TS_CONNECTING,
TS_CONNECTED
};
struct tcp_connection {
struct bufferevent *bev;
enum tcp_state state;
u16 awaiting_packet_size;
};
struct evdns_server_port;
struct client_tcp_connection {
LIST_ENTRY(client_tcp_connection) next;
struct tcp_connection connection;
struct evdns_server_port *port;
};
struct nameserver {
evutil_socket_t socket; /* a connected UDP socket */
struct tcp_connection *connection; /* intended for TCP support */
struct sockaddr_storage address;
ev_socklen_t addrlen;
int failed_times; /* number of times which we have given this server a chance */
int timedout; /* number of times in a row a request has timed out */
struct event event;
/* these objects are kept in a circular list */
struct nameserver *next, *prev;
struct event timeout_event; /* used to keep the timeout for */
/* when we next probe this server. */
/* Valid if state == 0 */
/* Outstanding probe request for this nameserver, if any */
struct evdns_request *probe_request;
char state; /* zero if we think that this server is down */
char choked; /* true if we have an EAGAIN from this server's socket */
char write_waiting; /* true if we are waiting for EV_WRITE events */
struct evdns_base *base;
/* Number of currently inflight requests: used
* to track when we should add/del the event. */
int requests_inflight;
};
/* Represents a local port where we're listening for DNS requests. */
struct evdns_server_port {
evutil_socket_t socket; /* socket we use to read queries and write replies. */
int refcnt; /* reference count. */
char choked; /* Are we currently blocked from writing? */
char closing; /* Are we trying to close this port, pending writes? */
evdns_request_callback_fn_type user_callback; /* Fn to handle requests */
void *user_data; /* Opaque pointer passed to user_callback */
struct event event; /* Read/write event */
/* circular list of replies that we want to write. */
struct server_request *pending_replies;
struct event_base *event_base;
/* Structures for tcp support */
struct evconnlistener *listener;
LIST_HEAD(client_list, client_tcp_connection) client_connections;
unsigned client_connections_count;
unsigned max_client_connections;
struct timeval tcp_idle_timeout;
#ifndef EVENT__DISABLE_THREAD_SUPPORT
void *lock;
#endif
};
/* Represents part of a reply being built. (That is, a single RR.) */
struct server_reply_item {
struct server_reply_item *next; /* next item in sequence. */
char *name; /* name part of the RR */
u16 type; /* The RR type */
u16 class; /* The RR class (usually CLASS_INET) */
u32 ttl; /* The RR TTL */
char is_name; /* True iff data is a label */
u16 datalen; /* Length of data; -1 if data is a label */
void *data; /* The contents of the RR */
};
/* Represents a request that we've received as a DNS server, and holds */
/* the components of the reply as we're constructing it. */
struct server_request {
/* Pointers to the next and previous entries on the list of replies */
/* that we're waiting to write. Only set if we have tried to respond */
/* and gotten EAGAIN. */
struct server_request *next_pending;
struct server_request *prev_pending;
u16 trans_id; /* Transaction id. */
struct evdns_server_port *port; /* Which port received this request on? */
struct client_tcp_connection *client; /* Equal to NULL in case of UDP connection. */
struct sockaddr_storage addr; /* Where to send the response in case of UDP. Equal to NULL in case of TCP connection.*/
ev_socklen_t addrlen; /* length of addr */
u16 max_udp_reply_size; /* Maximum size of udp reply that client can handle. */
int n_answer; /* how many answer RRs have been set? */
int n_authority; /* how many authority RRs have been set? */
int n_additional; /* how many additional RRs have been set? */
struct server_reply_item *answer; /* linked list of answer RRs */
struct server_reply_item *authority; /* linked list of authority RRs */
struct server_reply_item *additional; /* linked list of additional RRs */
/* Constructed response. Only set once we're ready to send a reply. */
/* Once this is set, the RR fields are cleared, and no more should be set. */
char *response;
size_t response_len;
/* Caller-visible fields: flags, questions. */
struct evdns_server_request base;
};
struct evdns_base {
/* An array of n_req_heads circular lists for inflight requests.
* Each inflight request req is in req_heads[req->trans_id % n_req_heads].
*/
struct request **req_heads;
/* A circular list of requests that we're waiting to send, but haven't
* sent yet because there are too many requests inflight */
struct request *req_waiting_head;
/* A circular list of nameservers. */
struct nameserver *server_head;
int n_req_heads;
struct event_base *event_base;
/* The number of good nameservers that we have */
int global_good_nameservers;
/* inflight requests are contained in the req_head list */
/* and are actually going out across the network */
int global_requests_inflight;
/* requests which aren't inflight are in the waiting list */
/* and are counted here */
int global_requests_waiting;
int global_max_requests_inflight;
struct timeval global_timeout; /* 5 seconds by default */
int global_max_reissues; /* a reissue occurs when we get some errors from the server */
int global_max_retransmits; /* number of times we'll retransmit a request which timed out */
/* number of timeouts in a row before we consider this server to be down */
int global_max_nameserver_timeout;
/* true iff we will use the 0x20 hack to prevent poisoning attacks. */
int global_randomize_case;
/* Maximum size of a UDP DNS packet. */
u16 global_max_udp_size;
/* The first time that a nameserver fails, how long do we wait before
* probing to see if it has returned? */
struct timeval global_nameserver_probe_initial_timeout;
/* Combination of DNS_QUERY_USEVC, DNS_QUERY_IGNTC flags
* to control requests via TCP. */
u16 global_tcp_flags;
/* Idle timeout for outgoing TCP connections. */
struct timeval global_tcp_idle_timeout;
/** Port to bind to for outgoing DNS packets. */
struct sockaddr_storage global_outgoing_address;
/** ev_socklen_t for global_outgoing_address. 0 if it isn't set. */
ev_socklen_t global_outgoing_addrlen;
struct timeval global_getaddrinfo_allow_skew;
int so_rcvbuf;
int so_sndbuf;
int getaddrinfo_ipv4_timeouts;
int getaddrinfo_ipv6_timeouts;
int getaddrinfo_ipv4_answered;
int getaddrinfo_ipv6_answered;
struct search_state *global_search_state;
TAILQ_HEAD(hosts_list, hosts_entry) hostsdb;
#ifndef EVENT__DISABLE_THREAD_SUPPORT
void *lock;
#endif
int disable_when_inactive;
};
struct hosts_entry {
TAILQ_ENTRY(hosts_entry) next;
union {
struct sockaddr sa;
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
} addr;
int addrlen;
char hostname[1];
};
static struct evdns_base *current_base = NULL;
struct evdns_base *
evdns_get_global_base(void)
{
return current_base;
}
/* Given a pointer to an evdns_server_request, get the corresponding */
/* server_request. */
#define TO_SERVER_REQUEST(base_ptr) \
((struct server_request*) \
(((char*)(base_ptr) - evutil_offsetof(struct server_request, base))))
#define REQ_HEAD(base, id) ((base)->req_heads[id % (base)->n_req_heads])
static struct nameserver *nameserver_pick(struct evdns_base *base);
static void evdns_request_insert(struct request *req, struct request **head);
static void evdns_request_remove(struct request *req, struct request **head);
static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg);
static int evdns_transmit(struct evdns_base *base);
static int evdns_request_transmit(struct request *req);
static void nameserver_send_probe(struct nameserver *const ns);
static void search_request_finished(struct evdns_request *const);
static int search_try_next(struct evdns_request *const req);
static struct request *search_request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg);
static void evdns_requests_pump_waiting_queue(struct evdns_base *base);
static u16 transaction_id_pick(struct evdns_base *base);
static struct request *request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *name, int flags, evdns_callback_type callback, void *ptr);
static struct request *request_clone(struct evdns_base *base, struct request* current);
static void request_submit(struct request *const req);
static int server_request_free(struct server_request *req);
static void server_request_free_answers(struct server_request *req);
static void server_port_free(struct evdns_server_port *port);
static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg);
static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename);
static int evdns_base_set_option_impl(struct evdns_base *base,
const char *option, const char *val, int flags);
static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests);
static void evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg);
static int evdns_server_request_format_response(struct server_request *req, int err);
static void incoming_conn_cb(struct evconnlistener *listener, evutil_socket_t fd,
struct sockaddr *address, int socklen, void *arg);
static int strtoint(const char *const str);
#ifdef EVENT__DISABLE_THREAD_SUPPORT
#define EVDNS_LOCK(base) EVUTIL_NIL_STMT_
#define EVDNS_UNLOCK(base) EVUTIL_NIL_STMT_
#define ASSERT_LOCKED(base) EVUTIL_NIL_STMT_
#else
#define EVDNS_LOCK(base) \
EVLOCK_LOCK((base)->lock, 0)
#define EVDNS_UNLOCK(base) \
EVLOCK_UNLOCK((base)->lock, 0)
#define ASSERT_LOCKED(base) \
EVLOCK_ASSERT_LOCKED((base)->lock)
#endif
static evdns_debug_log_fn_type evdns_log_fn = NULL;
void
evdns_set_log_fn(evdns_debug_log_fn_type fn)
{
evdns_log_fn = fn;
}
#ifdef __GNUC__
#define EVDNS_LOG_CHECK __attribute__ ((format(printf, 2, 3)))
#else
#define EVDNS_LOG_CHECK
#endif
static void evdns_log_(int severity, const char *fmt, ...) EVDNS_LOG_CHECK;
static void
evdns_log_(int severity, const char *fmt, ...)
{
va_list args;
va_start(args,fmt);
if (evdns_log_fn) {
char buf[512];
int is_warn = (severity == EVDNS_LOG_WARN);
evutil_vsnprintf(buf, sizeof(buf), fmt, args);
evdns_log_fn(is_warn, buf);
} else {
event_logv_(severity, NULL, fmt, args);
}
va_end(args);
}
#define log evdns_log_
/* Initialize tcp_connection structure. */
static void
init_tcp_connection(struct tcp_connection *conn, struct bufferevent *bev)
{
memset(conn, 0, sizeof(*conn));
conn->state = TS_DISCONNECTED;
conn->bev = bev;
conn->awaiting_packet_size = 0;
}
/* Disconnect tcp connection. */
static void
evdns_tcp_disconnect(struct tcp_connection *conn)
{
if (!conn)
return;
conn->state = TS_DISCONNECTED;
conn->awaiting_packet_size = 0;
if (conn->bev) {
bufferevent_free(conn->bev);
conn->bev = NULL;
}
}
/* Add new tcp client to the list of TCP clients in the TCP DNS server. */
static struct client_tcp_connection*
evdns_add_tcp_client(struct evdns_server_port *port, struct bufferevent *bev)
{
struct client_tcp_connection *client;
EVUTIL_ASSERT(port && bev);
if (port->max_client_connections == port->client_connections_count)
goto error;
client = mm_calloc(1, sizeof(*client));
if (!client)
goto error;
init_tcp_connection(&client->connection, bev);
client->port = port;
LIST_INSERT_HEAD(&port->client_connections, client, next);
++port->client_connections_count;
/* we need to hold evdns_server_port as long as one connection at least stays alive */
++port->refcnt;
return client;
error:
return NULL;
}
/* Remove tcp client and free all associated data from the TCP DNS server. */
static int
evdns_remove_tcp_client(struct evdns_server_port *port, struct client_tcp_connection *client)
{
if (!port || !client)
goto error;
evdns_tcp_disconnect(&client->connection);
LIST_REMOVE(client, next);
mm_free(client);
--port->client_connections_count;
--port->refcnt;
return 0;
error:
return -1;
}
/* Remove all tcp clients and free all associated data from the TCP DNS server. */
static void
evdns_remove_all_tcp_clients(struct evdns_server_port *port)
{
struct client_tcp_connection *client;
while ((client = LIST_FIRST(&port->client_connections))) {
evdns_remove_tcp_client(port, client);
}
}
/* Create new tcp connection structure for DNS client. */
static struct tcp_connection *
new_tcp_connecton(struct bufferevent *bev)
{
struct tcp_connection *conn;
if (!bev)
return NULL;
conn = mm_calloc(1, sizeof(*conn));
if (!conn)
return NULL;
init_tcp_connection(conn, bev);
return conn;
}
/* Disconnect and free all associated data for the tcp connection in DNS client. */
static void
disconnect_and_free_connection(struct tcp_connection *conn)
{
if (!conn)
return;
evdns_tcp_disconnect(conn);
mm_free(conn);
}
/* This walks the list of inflight requests to find the */
/* one with a matching transaction id. Returns NULL on */
/* failure */
static struct request *
request_find_from_trans_id(struct evdns_base *base, u16 trans_id) {
struct request *req = REQ_HEAD(base, trans_id);
struct request *const started_at = req;
ASSERT_LOCKED(base);
if (req) {
do {
if (req->trans_id == trans_id) return req;
req = req->next;
} while (req != started_at);
}
return NULL;
}
/* a libevent callback function which is called when a nameserver */
/* has gone down and we want to test if it has came back to life yet */
static void
nameserver_prod_callback(evutil_socket_t fd, short events, void *arg) {
struct nameserver *const ns = (struct nameserver *) arg;
(void)fd;
(void)events;
EVDNS_LOCK(ns->base);
nameserver_send_probe(ns);
EVDNS_UNLOCK(ns->base);
}
/* a libevent callback which is called when a nameserver probe (to see if */
/* it has come back to life) times out. We increment the count of failed_times */
/* and wait longer to send the next probe packet. */
static void
nameserver_probe_failed(struct nameserver *const ns) {
struct timeval timeout;
int i;
ASSERT_LOCKED(ns->base);
(void) evtimer_del(&ns->timeout_event);
if (ns->state == 1) {
/* This can happen if the nameserver acts in a way which makes us mark */
/* it as bad and then starts sending good replies. */
return;
}
#define MAX_PROBE_TIMEOUT 3600
#define TIMEOUT_BACKOFF_FACTOR 3
memcpy(&timeout, &ns->base->global_nameserver_probe_initial_timeout,
sizeof(struct timeval));
for (i=ns->failed_times; i > 0 && timeout.tv_sec < MAX_PROBE_TIMEOUT; --i) {
timeout.tv_sec *= TIMEOUT_BACKOFF_FACTOR;
timeout.tv_usec *= TIMEOUT_BACKOFF_FACTOR;
if (timeout.tv_usec > 1000000) {
timeout.tv_sec += timeout.tv_usec / 1000000;
timeout.tv_usec %= 1000000;
}
}
if (timeout.tv_sec > MAX_PROBE_TIMEOUT) {
timeout.tv_sec = MAX_PROBE_TIMEOUT;
timeout.tv_usec = 0;
}
ns->failed_times++;
if (evtimer_add(&ns->timeout_event, &timeout) < 0) {
char addrbuf[128];
log(EVDNS_LOG_WARN,
"Error from libevent when adding timer event for %s",
evutil_format_sockaddr_port_(
(struct sockaddr *)&ns->address,
addrbuf, sizeof(addrbuf)));
}
}
static void
request_swap_ns(struct request *req, struct nameserver *ns) {
if (ns && req->ns != ns) {
EVUTIL_ASSERT(req->ns->requests_inflight > 0);
req->ns->requests_inflight--;
ns->requests_inflight++;
req->ns = ns;
}
}
/* called when a nameserver has been deemed to have failed. For example, too */
/* many packets have timed out etc */
static void
nameserver_failed(struct nameserver *const ns, const char *msg, int err) {
struct request *req, *started_at;
struct evdns_base *base = ns->base;
int i;
char addrbuf[128];
ASSERT_LOCKED(base);
/* if this nameserver has already been marked as failed */
/* then don't do anything */
if (!ns->state) return;
log(EVDNS_LOG_MSG, "Nameserver %s has failed: %s",
evutil_format_sockaddr_port_(
(struct sockaddr *)&ns->address,
addrbuf, sizeof(addrbuf)),
msg);
base->global_good_nameservers--;
EVUTIL_ASSERT(base->global_good_nameservers >= 0);
if (base->global_good_nameservers == 0) {
log(EVDNS_LOG_MSG, "All nameservers have failed");
}
ns->state = 0;
ns->failed_times = 1;
if (ns->connection) {
disconnect_and_free_connection(ns->connection);
ns->connection = NULL;
} else if (err == ENOTCONN) {
/* XXX: If recvfrom results in ENOTCONN, the socket remains readable
* which triggers another recvfrom. The observed behavior is 100% CPU use.
* This occurs on iOS (kqueue) after the process has been backgrounded
* for a long time (~300 seconds) and then resumed.
* All sockets, TCP and UDP, seem to get ENOTCONN and must be closed.
* https://github.com/libevent/libevent/issues/265 */
const struct sockaddr *address = (const struct sockaddr *)&ns->address;
evutil_closesocket(ns->socket);
ns->socket = evutil_socket_(address->sa_family,
SOCK_DGRAM | EVUTIL_SOCK_NONBLOCK | EVUTIL_SOCK_CLOEXEC, 0);
if (base->global_outgoing_addrlen &&
!evutil_sockaddr_is_loopback_(address)) {
if (bind(ns->socket,
(struct sockaddr *)&base->global_outgoing_address,
base->global_outgoing_addrlen) < 0) {
log(EVDNS_LOG_WARN, "Couldn't bind to outgoing address");
}
}
event_del(&ns->event);
event_assign(&ns->event, ns->base->event_base, ns->socket,
EV_READ | (ns->write_waiting ? EV_WRITE : 0) | EV_PERSIST,
nameserver_ready_callback, ns);
if (!base->disable_when_inactive && event_add(&ns->event, NULL) < 0) {
log(EVDNS_LOG_WARN, "Couldn't add %s event",
ns->write_waiting ? "rw": "read");
}
}
if (evtimer_add(&ns->timeout_event,
&base->global_nameserver_probe_initial_timeout) < 0) {
log(EVDNS_LOG_WARN,
"Error from libevent when adding timer event for %s",
evutil_format_sockaddr_port_(
(struct sockaddr *)&ns->address,
addrbuf, sizeof(addrbuf)));
/* ???? Do more? */
}
/* walk the list of inflight requests to see if any can be reassigned to */
/* a different server. Requests in the waiting queue don't have a */
/* nameserver assigned yet */
/* if we don't have *any* good nameservers then there's no point */
/* trying to reassign requests to one */
if (!base->global_good_nameservers) return;
for (i = 0; i < base->n_req_heads; ++i) {
req = started_at = base->req_heads[i];
if (req) {
do {
if (req->tx_count == 0 && req->ns == ns) {
/* still waiting to go out, can be moved */
/* to another server */
request_swap_ns(req, nameserver_pick(base));
}
req = req->next;
} while (req != started_at);
}
}
}
static void
nameserver_up(struct nameserver *const ns)
{
char addrbuf[128];
ASSERT_LOCKED(ns->base);
if (ns->state) return;
log(EVDNS_LOG_MSG, "Nameserver %s is back up",
evutil_format_sockaddr_port_(
(struct sockaddr *)&ns->address,
addrbuf, sizeof(addrbuf)));
evtimer_del(&ns->timeout_event);
if (ns->probe_request) {
evdns_cancel_request(ns->base, ns->probe_request);
ns->probe_request = NULL;
}
ns->state = 1;
ns->failed_times = 0;
ns->timedout = 0;
ns->base->global_good_nameservers++;
}
static void
request_trans_id_set(struct request *const req, const u16 trans_id) {
req->trans_id = trans_id;
*((u16 *) req->request) = htons(trans_id);
}
/* Called to remove a request from a list and dealloc it. */
/* head is a pointer to the head of the list it should be */
/* removed from or NULL if the request isn't in a list. */
/* when free_handle is one, free the handle as well. */
static void
request_finished(struct request *const req, struct request **head, int free_handle) {
struct evdns_base *base = req->base;
int was_inflight = (head != &base->req_waiting_head);
EVDNS_LOCK(base);
ASSERT_VALID_REQUEST(req);
if (head)
evdns_request_remove(req, head);
log(EVDNS_LOG_DEBUG, "Removing timeout for request %p", req);
if (was_inflight) {
evtimer_del(&req->timeout_event);
base->global_requests_inflight--;
req->ns->requests_inflight--;
} else {
base->global_requests_waiting--;
}
/* it was initialized during request_new / evtimer_assign */
event_debug_unassign(&req->timeout_event);
if (req->ns &&
req->ns->requests_inflight == 0 &&
req->base->disable_when_inactive) {
event_del(&req->ns->event);
evtimer_del(&req->ns->timeout_event);
}
if (!req->request_appended) {
/* need to free the request data on it's own */
mm_free(req->request);
} else {
/* the request data is appended onto the header */
/* so everything gets free()ed when we: */
}
if (req->handle) {
EVUTIL_ASSERT(req->handle->current_req == req);
if (free_handle) {
search_request_finished(req->handle);
req->handle->current_req = NULL;
if (! req->handle->pending_cb) {
/* If we're planning to run the callback,
* don't free the handle until later. */
mm_free(req->handle);
}
req->handle = NULL; /* If we have a bug, let's crash
* early */
} else {
req->handle->current_req = NULL;
}
}
mm_free(req);
evdns_requests_pump_waiting_queue(base);
EVDNS_UNLOCK(base);
}
/* This is called when a server returns a funny error code. */
/* We try the request again with another server. */
/* */
/* return: */
/* 0 ok */
/* 1 failed/reissue is pointless */
static int
request_reissue(struct request *req) {
const struct nameserver *const last_ns = req->ns;
ASSERT_LOCKED(req->base);
ASSERT_VALID_REQUEST(req);
/* the last nameserver should have been marked as failing */
/* by the caller of this function, therefore pick will try */
/* not to return it */
request_swap_ns(req, nameserver_pick(req->base));
if (req->ns == last_ns) {
/* ... but pick did return it */
/* not a lot of point in trying again with the */
/* same server */
return 1;
}
req->reissue_count++;
req->tx_count = 0;
req->transmit_me = 1;
return 0;
}
/* this function looks for space on the inflight queue and promotes */
/* requests from the waiting queue if it can. */
/* */
/* TODO: */
/* add return code, see at nameserver_pick() and other functions. */
static void
evdns_requests_pump_waiting_queue(struct evdns_base *base) {
ASSERT_LOCKED(base);
while (base->global_requests_inflight < base->global_max_requests_inflight &&
base->global_requests_waiting) {
struct request *req;
EVUTIL_ASSERT(base->req_waiting_head);
req = base->req_waiting_head;
req->ns = nameserver_pick(base);
if (!req->ns)
return;
/* move a request from the waiting queue to the inflight queue */
req->ns->requests_inflight++;
evdns_request_remove(req, &base->req_waiting_head);
base->global_requests_waiting--;
base->global_requests_inflight++;
request_trans_id_set(req, transaction_id_pick(base));
evdns_request_insert(req, &REQ_HEAD(base, req->trans_id));
evdns_request_transmit(req);
evdns_transmit(base);
}
}
/* TODO(nickm) document */
struct deferred_reply_callback {
struct event_callback deferred;
struct evdns_request *handle;
u8 request_type;
u8 have_reply;
u32 ttl;
u32 err;
evdns_callback_type user_callback;
struct reply reply;
};
static void
reply_run_callback(struct event_callback *d, void *user_pointer)
{
struct deferred_reply_callback *cb =
EVUTIL_UPCAST(d, struct deferred_reply_callback, deferred);
switch (cb->request_type) {
case TYPE_A:
if (cb->have_reply)
cb->user_callback(DNS_ERR_NONE, DNS_IPv4_A,
cb->reply.rr_count, cb->ttl,
cb->reply.data.a,
user_pointer);
else
cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
break;
case TYPE_PTR:
if (cb->have_reply) {
char *name = cb->reply.data.ptr_name;
cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl,
&name, user_pointer);
} else {
cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);