-
Notifications
You must be signed in to change notification settings - Fork 996
Expand file tree
/
Copy pathdnsdist.cc
More file actions
3980 lines (3513 loc) · 159 KB
/
dnsdist.cc
File metadata and controls
3980 lines (3513 loc) · 159 KB
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
/*
* This file is part of PowerDNS or dnsdist.
* Copyright -- PowerDNS.COM B.V. and its contributors
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* In addition, for the avoidance of any doubt, permission is granted to
* link this program with OpenSSL and to (re)distribute the binaries
* produced as the result of such linking.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "config.h"
#include <cstdint>
#include <cstring>
#include <filesystem>
#include <fstream>
#include <getopt.h>
#include <grp.h>
#include <limits>
#include <netinet/tcp.h>
#include <optional>
#include <pwd.h>
#include <set>
#include <sys/resource.h>
#include <unistd.h>
#include <vector>
#include "dns.hh"
#include "dnsdist-idstate.hh"
#include "dnsdist-opentelemetry.hh"
#include "dnsdist-systemd.hh"
#include "logging.hh"
#include "protozero-trace.hh"
#ifdef HAVE_SYSTEMD
#include <systemd/sd-daemon.h>
#endif
#include "dnsdist.hh"
#include "dnsdist-async.hh"
#include "dnsdist-cache.hh"
#include "dnsdist-carbon.hh"
#include "dnsdist-configuration.hh"
#include "dnsdist-configuration-yaml.hh"
#include "dnsdist-console.hh"
#include "dnsdist-console-completion.hh"
#include "dnsdist-crypto.hh"
#include "dnsdist-discovery.hh"
#include "dnsdist-dynblocks.hh"
#include "dnsdist-ecs.hh"
#include "dnsdist-edns.hh"
#include "dnsdist-frontend.hh"
#include "dnsdist-healthchecks.hh"
#include "dnsdist-logging.hh"
#include "dnsdist-lua.hh"
#include "dnsdist-lua-hooks.hh"
#include "dnsdist-nghttp2.hh"
#include "dnsdist-nghttp2-in.hh"
#include "dnsdist-proxy-protocol.hh"
#include "dnsdist-random.hh"
#include "dnsdist-rings.hh"
#include "dnsdist-rules.hh"
#include "dnsdist-secpoll.hh"
#include "dnsdist-self-answers.hh"
#include "dnsdist-snmp.hh"
#include "dnsdist-tcp.hh"
#include "dnsdist-tcp-downstream.hh"
#include "dnsdist-tcp-upstream.hh"
#include "dnsdist-udp.hh"
#include "dnsdist-web.hh"
#include "dnsdist-xsk.hh"
#include "base64.hh"
#include "capabilities.hh"
#include "coverage.hh"
#include "delaypipe.hh"
#include "dolog.hh"
#include "dnsname.hh"
#include "ednsoptions.hh"
#include "gettime.hh"
#include "lock.hh"
#include "misc.hh"
#include "sstuff.hh"
#include "threadname.hh"
#include "xsk.hh"
/* Known sins:
Receiver is currently single threaded
not *that* bad actually, but now that we are thread safe, might want to scale
*/
/* the RuleAction plan
Set of Rules, if one matches, it leads to an Action
Both rules and actions could conceivably be Lua based.
On the C++ side, both could be inherited from a class Rule and a class Action,
on the Lua side we can't do that. */
using std::thread;
string g_outputBuffer;
shared_ptr<BPFFilter> g_defaultBPFFilter{nullptr};
/* UDP: the grand design. Per socket we listen on for incoming queries there is one thread.
Then we have a bunch of connected sockets for talking to downstream servers.
We send directly to those sockets.
For the return path, per downstream server we have a thread that listens to responses.
Per socket there is an array of 2^16 states, when we send out a packet downstream, we note
there the original requestor and the original id. The new ID is the offset in the array.
When an answer comes in on a socket, we look up the offset by the id, and lob it to the
original requestor.
IDs are assigned by atomic increments of the socket offset.
*/
Rings g_rings;
// we are not willing to receive a bigger UDP response than that, no matter what
static constexpr size_t s_maxUDPResponsePacketSize{4096U};
static size_t const s_initialUDPPacketBufferSize = s_maxUDPResponsePacketSize + DNSCRYPT_MAX_RESPONSE_PADDING_AND_MAC_SIZE;
static_assert(s_initialUDPPacketBufferSize <= UINT16_MAX, "Packet size should fit in a uint16_t");
static void sendfromto(int sock, const PacketBuffer& buffer, const ComboAddress& from, const ComboAddress& dest)
{
const int flags = 0;
if (from.sin4.sin_family == 0) {
// NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
auto ret = sendto(sock, buffer.data(), buffer.size(), flags, reinterpret_cast<const struct sockaddr*>(&dest), dest.getSocklen());
if (ret == -1) {
int error = errno;
VERBOSESLOG(infolog("Error sending UDP response to %s: %s", dest.toStringWithPort(), stringerror(error)),
dnsdist::logging::getTopLogger("sendfromto")->error(Logr::Info, error, "Error sending UDP response", "client.address", Logging::Loggable(dest)));
}
return;
}
try {
sendMsgWithOptions(sock, buffer.data(), buffer.size(), &dest, &from, 0, 0);
}
catch (const std::exception& exp) {
VERBOSESLOG(infolog("Error sending UDP response from %s to %s: %s", from.toStringWithPort(), dest.toStringWithPort(), exp.what()),
dnsdist::logging::getTopLogger("sendfromto")->error(Logr::Info, exp.what(), "Error sending UDP response", "source.address", Logging::Loggable(from), "client.address", Logging::Loggable(dest)));
}
}
static void truncateTC(PacketBuffer& packet, size_t maximumSize, unsigned int qnameWireLength, bool addEDNSToSelfGeneratedResponses)
{
try {
bool hadEDNS = false;
uint16_t payloadSize = 0;
uint16_t zValue = 0;
if (addEDNSToSelfGeneratedResponses) {
// NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
hadEDNS = getEDNSUDPPayloadSizeAndZ(reinterpret_cast<const char*>(packet.data()), packet.size(), &payloadSize, &zValue);
}
packet.resize(static_cast<uint16_t>(sizeof(dnsheader) + qnameWireLength + DNS_TYPE_SIZE + DNS_CLASS_SIZE));
dnsdist::PacketMangling::editDNSHeaderFromPacket(packet, [](dnsheader& header) {
header.ancount = 0;
header.arcount = 0;
header.nscount = 0;
return true;
});
if (hadEDNS) {
addEDNS(packet, maximumSize, (zValue & EDNS_HEADER_FLAG_DO) != 0, payloadSize, 0);
}
}
catch (...) {
++dnsdist::metrics::g_stats.truncFail;
}
}
#ifndef DISABLE_DELAY_PIPE
struct DelayedPacket
{
int fd{-1};
PacketBuffer packet;
ComboAddress destination;
ComboAddress origDest;
void operator()() const
{
sendfromto(fd, packet, origDest, destination);
}
};
static std::unique_ptr<DelayPipe<DelayedPacket>> g_delay{nullptr};
#endif /* DISABLE_DELAY_PIPE */
static void doLatencyStats(dnsdist::Protocol protocol, double latencyUs)
{
constexpr auto doAvg = [](pdns::stat_double_t& var, double n, double weight) {
var.store((weight - 1) * var.load() / weight + n / weight);
};
if (protocol == dnsdist::Protocol::DoUDP || protocol == dnsdist::Protocol::DNSCryptUDP) {
if (latencyUs >= 0) {
dnsdist::metrics::updateLatencyHistogram(dnsdist::metrics::g_stats, static_cast<uint64_t>(latencyUs));
}
doAvg(dnsdist::metrics::g_stats.latencyAvg100, latencyUs, 100);
doAvg(dnsdist::metrics::g_stats.latencyAvg1000, latencyUs, 1000);
doAvg(dnsdist::metrics::g_stats.latencyAvg10000, latencyUs, 10000);
doAvg(dnsdist::metrics::g_stats.latencyAvg1000000, latencyUs, 1000000);
}
else if (protocol == dnsdist::Protocol::DoTCP || protocol == dnsdist::Protocol::DNSCryptTCP) {
doAvg(dnsdist::metrics::g_stats.latencyTCPAvg100, latencyUs, 100);
doAvg(dnsdist::metrics::g_stats.latencyTCPAvg1000, latencyUs, 1000);
doAvg(dnsdist::metrics::g_stats.latencyTCPAvg10000, latencyUs, 10000);
doAvg(dnsdist::metrics::g_stats.latencyTCPAvg1000000, latencyUs, 1000000);
}
else if (protocol == dnsdist::Protocol::DoT) {
doAvg(dnsdist::metrics::g_stats.latencyDoTAvg100, latencyUs, 100);
doAvg(dnsdist::metrics::g_stats.latencyDoTAvg1000, latencyUs, 1000);
doAvg(dnsdist::metrics::g_stats.latencyDoTAvg10000, latencyUs, 10000);
doAvg(dnsdist::metrics::g_stats.latencyDoTAvg1000000, latencyUs, 1000000);
}
else if (protocol == dnsdist::Protocol::DoH) {
doAvg(dnsdist::metrics::g_stats.latencyDoHAvg100, latencyUs, 100);
doAvg(dnsdist::metrics::g_stats.latencyDoHAvg1000, latencyUs, 1000);
doAvg(dnsdist::metrics::g_stats.latencyDoHAvg10000, latencyUs, 10000);
doAvg(dnsdist::metrics::g_stats.latencyDoHAvg1000000, latencyUs, 1000000);
}
else if (protocol == dnsdist::Protocol::DoQ) {
doAvg(dnsdist::metrics::g_stats.latencyDoQAvg100, latencyUs, 100);
doAvg(dnsdist::metrics::g_stats.latencyDoQAvg1000, latencyUs, 1000);
doAvg(dnsdist::metrics::g_stats.latencyDoQAvg10000, latencyUs, 10000);
doAvg(dnsdist::metrics::g_stats.latencyDoQAvg1000000, latencyUs, 1000000);
}
else if (protocol == dnsdist::Protocol::DoH3) {
doAvg(dnsdist::metrics::g_stats.latencyDoH3Avg100, latencyUs, 100);
doAvg(dnsdist::metrics::g_stats.latencyDoH3Avg1000, latencyUs, 1000);
doAvg(dnsdist::metrics::g_stats.latencyDoH3Avg10000, latencyUs, 10000);
doAvg(dnsdist::metrics::g_stats.latencyDoH3Avg1000000, latencyUs, 1000000);
}
}
bool responseContentMatches(const PacketBuffer& response, const DNSName& qname, const uint16_t qtype, const uint16_t qclass, const std::shared_ptr<DownstreamState>& remote, bool allowEmptyResponse)
{
if (response.size() < sizeof(dnsheader)) {
return false;
}
const dnsheader_aligned dnsHeader(response.data());
if (dnsHeader->qr == 0) {
++dnsdist::metrics::g_stats.nonCompliantResponses;
if (remote) {
++remote->nonCompliantResponses;
}
return false;
}
if (dnsHeader->qdcount == 0) {
if ((dnsHeader->rcode != RCode::NoError && dnsHeader->rcode != RCode::NXDomain) || allowEmptyResponse) {
return true;
}
++dnsdist::metrics::g_stats.nonCompliantResponses;
if (remote) {
++remote->nonCompliantResponses;
}
return false;
}
try {
uint16_t rqtype{};
uint16_t rqclass{};
if (response.size() < (sizeof(dnsheader) + qname.wirelength() + sizeof(rqtype) + sizeof(rqclass))) {
return false;
}
// NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast,cppcoreguidelines-pro-bounds-pointer-arithmetic)
const std::string_view packetView(reinterpret_cast<const char*>(response.data() + sizeof(dnsheader)), response.size() - sizeof(dnsheader));
if (qname.matchesUncompressedName(packetView)) {
size_t pos = sizeof(dnsheader) + qname.wirelength();
rqtype = response.at(pos) * 256 + response.at(pos + 1);
rqclass = response.at(pos + 2) * 256 + response.at(pos + 3);
return rqtype == qtype && rqclass == qclass;
}
return false;
}
catch (const std::exception& e) {
if (remote && !response.empty() && static_cast<size_t>(response.size()) > sizeof(dnsheader)) {
VERBOSESLOG(infolog("Backend %s sent us a response with id %d that did not parse: %s", remote->d_config.remote.toStringWithPort(), ntohs(dnsHeader->id), e.what()),
dnsdist::logging::getTopLogger("udp-response-worker")->error(Logr::Info, e.what(), "Received a DNS response from a backend that we could not parse", "backend.address", Logging::Loggable(remote->d_config.remote), "dns.query.id", Logging::Loggable(ntohs(dnsHeader->id))));
}
++dnsdist::metrics::g_stats.nonCompliantResponses;
if (remote) {
++remote->nonCompliantResponses;
}
return false;
}
}
static void restoreFlags(struct dnsheader* dnsHeader, uint16_t origFlags)
{
static const uint16_t rdMask = 1 << FLAGS_RD_OFFSET;
static const uint16_t cdMask = 1 << FLAGS_CD_OFFSET;
static const uint16_t restoreFlagsMask = UINT16_MAX & ~(rdMask | cdMask);
uint16_t* flags = getFlagsFromDNSHeader(dnsHeader);
/* clear the flags we are about to restore */
*flags &= restoreFlagsMask;
/* only keep the flags we want to restore */
origFlags &= ~restoreFlagsMask;
/* set the saved flags as they were */
*flags |= origFlags;
}
static bool fixUpQueryTurnedResponse(DNSQuestion& dnsQuestion, const uint16_t origFlags)
{
dnsdist::PacketMangling::editDNSHeaderFromPacket(dnsQuestion.getMutableData(), [origFlags](dnsheader& header) {
restoreFlags(&header, origFlags);
return true;
});
if (dnsQuestion.d_selfGeneratedHandledEDNS) {
return true;
}
return addEDNSToQueryTurnedResponse(dnsQuestion);
}
static bool fixUpResponse(PacketBuffer& response, const DNSName& qname, uint16_t origFlags, bool ednsAdded, bool ecsAdded, bool* zeroScope)
{
if (response.size() < sizeof(dnsheader)) {
return false;
}
dnsdist::PacketMangling::editDNSHeaderFromPacket(response, [origFlags](dnsheader& header) {
restoreFlags(&header, origFlags);
return true;
});
if (response.size() == sizeof(dnsheader)) {
return true;
}
if (dnsdist::configuration::getCurrentRuntimeConfiguration().d_fixupCase) {
const auto& realname = qname.getStorage();
if (response.size() >= (sizeof(dnsheader) + realname.length())) {
memcpy(&response.at(sizeof(dnsheader)), realname.c_str(), realname.length());
}
}
if (ednsAdded || ecsAdded) {
uint16_t optStart{};
size_t optLen = 0;
bool last = false;
int res = locateEDNSOptRR(response, &optStart, &optLen, &last);
if (res == 0) {
if (zeroScope != nullptr) { // this finds if an EDNS Client Subnet scope was set, and if it is 0
size_t optContentStart = 0;
uint16_t optContentLen = 0;
/* we need at least 4 bytes after the option length (family: 2, source prefix-length: 1, scope prefix-length: 1) */
if (isEDNSOptionInOpt(response, optStart, optLen, EDNSOptionCode::ECS, &optContentStart, &optContentLen) && optContentLen >= 4) {
/* see if the EDNS Client Subnet SCOPE PREFIX-LENGTH byte in position 3 is set to 0, which is the only thing
we care about. */
*zeroScope = response.at(optContentStart + 3) == 0;
}
}
if (ednsAdded) {
/* we added the entire OPT RR,
therefore we need to remove it entirely */
if (last) {
/* simply remove the last AR */
response.resize(response.size() - optLen);
dnsdist::PacketMangling::editDNSHeaderFromPacket(response, [](dnsheader& header) {
uint16_t arcount = ntohs(header.arcount);
arcount--;
header.arcount = htons(arcount);
return true;
});
}
else {
/* Removing an intermediary RR could lead to compression error */
PacketBuffer rewrittenResponse;
if (rewriteResponseWithoutEDNS(response, rewrittenResponse) == 0) {
response = std::move(rewrittenResponse);
}
else {
SLOG(warnlog("Error rewriting content"),
dnsdist::logging::getTopLogger("fixup-response")->info(Logr::Error, "Error rewriting response content", "dns.question.name", Logging::Loggable(qname)));
}
}
}
else {
/* the OPT RR was already present, but without ECS,
we need to remove the ECS option if any */
if (last) {
/* nothing after the OPT RR, we can simply remove the
ECS option */
size_t existingOptLen = optLen;
// NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
removeEDNSOptionFromOPT(reinterpret_cast<char*>(&response.at(optStart)), &optLen, EDNSOptionCode::ECS);
response.resize(response.size() - (existingOptLen - optLen));
}
else {
PacketBuffer rewrittenResponse;
/* Removing an intermediary RR could lead to compression error */
if (rewriteResponseWithoutEDNSOption(response, EDNSOptionCode::ECS, rewrittenResponse) == 0) {
response = std::move(rewrittenResponse);
}
else {
SLOG(warnlog("Error rewriting content"),
dnsdist::logging::getTopLogger("fixup-response")->info(Logr::Error, "Error rewriting response content", "dns.question.name", Logging::Loggable(qname)));
}
}
}
}
}
return true;
}
#ifdef HAVE_DNSCRYPT
static bool encryptResponse(PacketBuffer& response, size_t maximumSize, bool tcp, std::unique_ptr<DNSCryptQuery>& dnsCryptQuery)
{
if (dnsCryptQuery) {
int res = dnsCryptQuery->encryptResponse(response, maximumSize, tcp);
if (res != 0) {
/* dropping response */
VERBOSESLOG(infolog("Error encrypting the response, dropping."),
dnsdist::logging::getTopLogger("dnscrypt")->info(Logr::Error, "Error encrypting response, dropping"));
return false;
}
}
return true;
}
#endif /* HAVE_DNSCRYPT */
bool applyRulesToResponse(const std::vector<dnsdist::rules::ResponseRuleAction>& respRuleActions, DNSResponse& dnsResponse)
{
auto closer = dnsResponse.ids.getCloser(__func__); // NOLINT(cppcoreguidelines-pro-bounds-array-to-pointer-decay)
if (respRuleActions.empty()) {
return true;
}
DNSResponseAction::Action action = DNSResponseAction::Action::None;
std::string ruleresult;
static const std::string ruleType = "Response";
for (const auto& rrule : respRuleActions) {
auto ruleCloser = dnsResponse.ids.getRulesCloser(rrule.d_name, ruleType);
if (rrule.d_rule->matches(&dnsResponse)) {
++rrule.d_rule->d_matches;
action = (*rrule.d_action)(&dnsResponse, &ruleresult);
switch (action) {
case DNSResponseAction::Action::Allow:
return true;
break;
case DNSResponseAction::Action::Drop:
return false;
break;
case DNSResponseAction::Action::HeaderModify:
return true;
break;
case DNSResponseAction::Action::ServFail:
if (dnsResponse.getData().size() < sizeof(dnsheader)) {
return false;
}
dnsdist::PacketMangling::editDNSHeaderFromPacket(dnsResponse.getMutableData(), [](dnsheader& header) {
header.rcode = RCode::ServFail;
return true;
});
return true;
break;
case DNSResponseAction::Action::Truncate:
if (dnsResponse.getData().size() < sizeof(dnsheader)) {
return false;
}
if (!dnsResponse.overTCP()) {
dnsdist::PacketMangling::editDNSHeaderFromPacket(dnsResponse.getMutableData(), [](dnsheader& header) {
header.tc = true;
header.qr = true;
return true;
});
truncateTC(dnsResponse.getMutableData(), dnsResponse.getMaximumSize(), dnsResponse.ids.qname.wirelength(), dnsdist::configuration::getCurrentRuntimeConfiguration().d_addEDNSToSelfGeneratedResponses);
++dnsdist::metrics::g_stats.ruleTruncated;
return true;
}
break;
/* non-terminal actions follow */
case DNSResponseAction::Action::Delay:
pdns::checked_stoi_into(dnsResponse.ids.delayMsec, ruleresult); // sorry
break;
case DNSResponseAction::Action::None:
break;
}
}
}
return true;
}
bool processResponseAfterRules(PacketBuffer& response, DNSResponse& dnsResponse, [[maybe_unused]] bool muted)
{
auto closer = dnsResponse.ids.getCloser(__func__); // NOLINT(cppcoreguidelines-pro-bounds-array-to-pointer-decay)
bool zeroScope = false;
if (!fixUpResponse(response, dnsResponse.ids.qname, dnsResponse.ids.origFlags, dnsResponse.ids.ednsAdded, dnsResponse.ids.ecsAdded, dnsResponse.ids.useZeroScope ? &zeroScope : nullptr)) {
if (closer) {
closer->setAttribute("result", AnyValue{"fixUpResponse->false"});
}
return false;
}
if (dnsResponse.ids.packetCache && !dnsResponse.ids.selfGenerated && !dnsResponse.ids.skipCache && (!dnsResponse.ids.forwardedOverUDP || response.size() <= s_maxUDPResponsePacketSize)) {
if (!dnsResponse.ids.useZeroScope) {
/* if the query was not suitable for zero-scope, for
example because it had an existing ECS entry so the hash is
not really 'no ECS', so just insert it for the existing subnet
since:
- we don't have the correct hash for a non-ECS query
- inserting with hash computed before the ECS replacement but with
the subnet extracted _after_ the replacement would not work.
*/
zeroScope = false;
}
uint32_t cacheKey = dnsResponse.ids.cacheKey;
if (dnsResponse.ids.protocol == dnsdist::Protocol::DoH && !dnsResponse.ids.forwardedOverUDP) {
cacheKey = dnsResponse.ids.cacheKeyTCP;
// disable zeroScope in that case, as we only have the "no-ECS" cache key for UDP
zeroScope = false;
}
if (zeroScope) {
// if zeroScope, pass the pre-ECS hash-key and do not pass the subnet to the cache
cacheKey = dnsResponse.ids.cacheKeyNoECS;
}
{
auto cacheInsertCloser = dnsResponse.ids.getCloser("packetCacheInsert"); // NOLINT(cppcoreguidelines-pro-bounds-array-to-pointer-decay)
dnsResponse.ids.packetCache->insert(cacheKey, zeroScope ? std::nullopt : dnsResponse.ids.subnet, dnsResponse.ids.cacheFlags, dnsResponse.ids.dnssecOK ? *dnsResponse.ids.dnssecOK : false, dnsResponse.ids.qname, dnsResponse.ids.qtype, dnsResponse.ids.qclass, response, dnsResponse.ids.forwardedOverUDP, dnsResponse.getHeader()->rcode, dnsResponse.ids.tempFailureTTL);
}
const auto& chains = dnsdist::configuration::getCurrentRuntimeConfiguration().d_ruleChains;
const auto& cacheInsertedRespRuleActions = dnsdist::rules::getResponseRuleChain(chains, dnsdist::rules::ResponseRuleChain::CacheInsertedResponseRules);
if (!applyRulesToResponse(cacheInsertedRespRuleActions, dnsResponse)) {
return false;
}
}
if (dnsResponse.ids.ttlCap > 0) {
dnsdist::PacketMangling::restrictDNSPacketTTLs(dnsResponse.getMutableData(), 0, dnsResponse.ids.ttlCap);
}
if (dnsResponse.ids.d_extendedErrors) {
for (const auto& ede : *dnsResponse.ids.d_extendedErrors) {
dnsdist::edns::addExtendedDNSError(dnsResponse.getMutableData(), dnsResponse.getMaximumSize(), ede);
}
}
if (dnsResponse.ids.cs->d_padResponses && !dnsResponse.ids.ednsAdded) {
dnsdist::edns::addEDNSPadding(dnsResponse.getMutableData(), dnsResponse.getMaximumSize());
}
#ifdef HAVE_DNSCRYPT
if (!muted) {
if (!encryptResponse(response, dnsResponse.getMaximumSize(), dnsResponse.overTCP(), dnsResponse.ids.dnsCryptQuery)) {
return false;
}
}
#endif /* HAVE_DNSCRYPT */
return true;
}
bool processResponse(PacketBuffer& response, DNSResponse& dnsResponse, bool muted)
{
// This is a new root span
auto closer = dnsResponse.ids.getCloser(__func__); // NOLINT(cppcoreguidelines-pro-bounds-array-to-pointer-decay)
const auto& chains = dnsdist::configuration::getCurrentRuntimeConfiguration().d_ruleChains;
const auto& respRuleActions = dnsdist::rules::getResponseRuleChain(chains, dnsdist::rules::ResponseRuleChain::ResponseRules);
if (!applyRulesToResponse(respRuleActions, dnsResponse)) {
return false;
}
if (dnsResponse.isAsynchronous()) {
return true;
}
return processResponseAfterRules(response, dnsResponse, muted);
}
static size_t getInitialUDPPacketBufferSize(bool expectProxyProtocol)
{
static_assert(dnsdist::configuration::s_udpIncomingBufferSize <= s_initialUDPPacketBufferSize, "The incoming buffer size should not be larger than s_initialUDPPacketBufferSize");
const auto& runtimeConfig = dnsdist::configuration::getCurrentRuntimeConfiguration();
if (!expectProxyProtocol || runtimeConfig.d_proxyProtocolACL.empty()) {
return s_initialUDPPacketBufferSize;
}
return s_initialUDPPacketBufferSize + runtimeConfig.d_proxyProtocolMaximumSize;
}
static size_t getMaximumIncomingPacketSize(const ClientState& clientState)
{
if (clientState.dnscryptCtx) {
return getInitialUDPPacketBufferSize(clientState.d_enableProxyProtocol);
}
const auto& runtimeConfig = dnsdist::configuration::getCurrentRuntimeConfiguration();
if (!clientState.d_enableProxyProtocol || runtimeConfig.d_proxyProtocolACL.empty()) {
return dnsdist::configuration::s_udpIncomingBufferSize;
}
return dnsdist::configuration::s_udpIncomingBufferSize + runtimeConfig.d_proxyProtocolMaximumSize;
}
bool sendUDPResponse(int origFD, const PacketBuffer& response, [[maybe_unused]] const int delayMsec, const ComboAddress& origDest, const ComboAddress& origRemote)
{
#ifndef DISABLE_DELAY_PIPE
if (delayMsec > 0 && g_delay != nullptr) {
DelayedPacket delayed{origFD, response, origRemote, origDest};
g_delay->submit(delayed, delayMsec);
return true;
}
#endif /* DISABLE_DELAY_PIPE */
// NOLINTNEXTLINE(readability-suspicious-call-argument)
sendfromto(origFD, response, origDest, origRemote);
return true;
}
void handleResponseSent(InternalQueryState& ids, double latencyUs, const ComboAddress& client, const ComboAddress& backend, unsigned int size, const dnsheader& cleartextDH, dnsdist::Protocol outgoingProtocol, bool fromBackend)
{
handleResponseSent(std::move(ids.qname), ids.qtype, latencyUs, client, backend, size, cleartextDH, outgoingProtocol, ids.protocol, fromBackend);
}
void handleResponseSent(DNSName&& qname, const QType& qtype, double latencyUs, const ComboAddress& client, const ComboAddress& backend, unsigned int size, const dnsheader& cleartextDH, dnsdist::Protocol outgoingProtocol, dnsdist::Protocol incomingProtocol, bool fromBackend)
{
if (g_rings.shouldRecordResponses()) {
timespec now{};
gettime(&now);
g_rings.insertResponse(now, client, std::move(qname), qtype, static_cast<unsigned int>(latencyUs), size, cleartextDH, backend, outgoingProtocol);
}
switch (cleartextDH.rcode) {
case RCode::NXDomain:
++dnsdist::metrics::g_stats.frontendNXDomain;
break;
case RCode::ServFail:
if (fromBackend) {
++dnsdist::metrics::g_stats.servfailResponses;
}
++dnsdist::metrics::g_stats.frontendServFail;
break;
case RCode::NoError:
++dnsdist::metrics::g_stats.frontendNoError;
break;
}
doLatencyStats(incomingProtocol, latencyUs);
}
static void handleResponseTC4UDPClient(DNSQuestion& dnsQuestion, uint16_t udpPayloadSize, PacketBuffer& response)
{
if (udpPayloadSize != 0 && response.size() > udpPayloadSize) {
VERBOSESLOG(infolog("Got a response of size %d while the initial UDP payload size was %d, truncating", response.size(), udpPayloadSize),
dnsQuestion.getLogger()->withName("udp-response")->info(Logr::Info, "Got a UDP response larger than the initial UDP payload size, truncating", "dns.response.size", Logging::Loggable(response.size()), "dns.query.udp_payload_size", Logging::Loggable(udpPayloadSize)));
truncateTC(dnsQuestion.getMutableData(), dnsQuestion.getMaximumSize(), dnsQuestion.ids.qname.wirelength(), dnsdist::configuration::getCurrentRuntimeConfiguration().d_addEDNSToSelfGeneratedResponses);
dnsdist::PacketMangling::editDNSHeaderFromPacket(dnsQuestion.getMutableData(), [](dnsheader& header) {
header.tc = true;
return true;
});
}
else if (dnsdist::configuration::getCurrentRuntimeConfiguration().d_truncateTC && dnsQuestion.getHeader()->tc) {
truncateTC(response, dnsQuestion.getMaximumSize(), dnsQuestion.ids.qname.wirelength(), dnsdist::configuration::getCurrentRuntimeConfiguration().d_addEDNSToSelfGeneratedResponses);
}
}
static void handleResponseForUDPClient(InternalQueryState& ids, PacketBuffer& response, const std::shared_ptr<DownstreamState>& backend, bool isAsync, bool selfGenerated)
{
DNSResponse dnsResponse(ids, response, backend);
handleResponseTC4UDPClient(dnsResponse, ids.udpPayloadSize, response);
/* when the answer is encrypted in place, we need to get a copy
of the original header before encryption to fill the ring buffer */
dnsheader cleartextDH{};
memcpy(&cleartextDH, dnsResponse.getHeader().get(), sizeof(cleartextDH));
if (!isAsync) {
if (!processResponse(response, dnsResponse, ids.cs != nullptr && ids.cs->muted)) {
return;
}
if (dnsResponse.isAsynchronous()) {
return;
}
}
++dnsdist::metrics::g_stats.responses;
if (ids.cs != nullptr) {
++ids.cs->responses;
}
bool muted = true;
if (ids.cs != nullptr && !ids.cs->muted && !ids.isXSK()) {
sendUDPResponse(ids.cs->udpFD, response, dnsResponse.ids.delayMsec, ids.hopLocal, ids.hopRemote);
muted = false;
}
if (!selfGenerated) {
auto latencyUs = ids.queryRealTime.udiff();
if (!muted) {
if (!ids.isXSK()) {
VERBOSESLOG(infolog("Got answer from %s, relayed to %s (UDP), took %d us", backend->d_config.remote.toStringWithPort(), ids.origRemote.toStringWithPort(), latencyUs),
dnsResponse.getLogger()->withName("udp-response")->info(Logr::Info, "Got answer from backend, relayed to client"));
}
else {
VERBOSESLOG(infolog("Got answer from %s, relayed to %s (UDP via XSK), took %d us", backend->d_config.remote.toStringWithPort(), ids.origRemote.toStringWithPort(), latencyUs),
dnsResponse.getLogger()->withName("udp-xsk-response")->info(Logr::Info, "Got answer from backend, relayed to client"));
}
}
else {
if (!ids.isXSK()) {
VERBOSESLOG(infolog("Got answer from %s, NOT relayed to %s (UDP) since that frontend is muted, took %d us", backend->d_config.remote.toStringWithPort(), ids.origRemote.toStringWithPort(), latencyUs),
dnsResponse.getLogger()->withName("udp-response")->info(Logr::Info, "Got answer from backend, NOT relayed to client since that frontend is muted"));
}
else {
VERBOSESLOG(infolog("Got answer from %s, relayed to %s (UDP via XSK), took %d us", backend->d_config.remote.toStringWithPort(), ids.origRemote.toStringWithPort(), latencyUs),
dnsResponse.getLogger()->withName("udp-xsk-response")->info(Logr::Info, "Got answer from backend, NOT relayed to client since that frontend is muted"));
}
}
handleResponseSent(ids, latencyUs, dnsResponse.ids.origRemote, backend->d_config.remote, response.size(), cleartextDH, backend->getProtocol(), true);
}
else {
handleResponseSent(ids, 0., dnsResponse.ids.origRemote, ComboAddress(), response.size(), cleartextDH, dnsdist::Protocol::DoUDP, false);
}
}
bool processResponderPacket(std::shared_ptr<DownstreamState>& dss, PacketBuffer& response, InternalQueryState&& ids)
{
const dnsheader_aligned dnsHeader(response.data());
auto queryId = dnsHeader->id;
if (!responseContentMatches(response, ids.qname, ids.qtype, ids.qclass, dss, dnsdist::configuration::getCurrentRuntimeConfiguration().d_allowEmptyResponse)) {
dss->restoreState(queryId, std::move(ids));
return false;
}
auto dohUnit = std::move(ids.du);
dnsdist::PacketMangling::editDNSHeaderFromPacket(response, [&ids](dnsheader& header) {
header.id = ids.origID;
return true;
});
++dss->responses;
double latencyUs = ids.queryRealTime.udiff();
// do that _before_ the processing, otherwise it's not fair to the backend
dss->latencyUsec = (127.0 * dss->latencyUsec / 128.0) + latencyUs / 128.0;
dss->reportResponse(dnsHeader->rcode);
/* don't call processResponse for DOH */
if (dohUnit) {
#ifdef HAVE_DNS_OVER_HTTPS
// DoH query, we cannot touch dohUnit after that
DOHUnitInterface::handleUDPResponse(std::move(dohUnit), std::move(response), std::move(ids), dss);
#endif
return false;
}
handleResponseForUDPClient(ids, response, dss, false, false);
return true;
}
// listens on a dedicated socket, lobs answers from downstream servers to original requestors
void responderThread(std::shared_ptr<DownstreamState> dss)
{
auto responderLogger = dnsdist::logging::getTopLogger("udp-response")->withValues("backend.address", Logging::Loggable(dss->d_config.remote));
try {
setThreadName("dnsdist/respond");
const size_t initialBufferSize = getInitialUDPPacketBufferSize(false);
/* allocate one more byte so we can detect truncation */
PacketBuffer response(initialBufferSize + 1);
uint16_t queryId = 0;
std::vector<int> sockets;
sockets.reserve(dss->sockets.size());
for (;;) {
try {
if (dss->isStopped()) {
break;
}
if (!dss->connected) {
/* the sockets are not connected yet, likely because we detected a problem,
tried to reconnect and it failed. We will try to reconnect after the next
successful health-check (unless reconnectOnUp is false), or when trying
to send in the UDP listener thread, but until then we simply need to wait. */
dss->waitUntilConnected();
continue;
}
dss->pickSocketsReadyForReceiving(sockets);
/* check a second time here because we might have waited quite a bit
since the first check */
if (dss->isStopped()) {
break;
}
for (const auto& sockDesc : sockets) {
/* allocate one more byte so we can detect truncation */
// NOLINTNEXTLINE(bugprone-use-after-move): resizing a vector has no preconditions so it is valid to do so after moving it
response.resize(initialBufferSize + 1);
ssize_t got = recv(sockDesc, response.data(), response.size(), 0);
if (got == 0 && dss->isStopped()) {
break;
}
if (got < 0 || static_cast<size_t>(got) < sizeof(dnsheader) || static_cast<size_t>(got) == (initialBufferSize + 1)) {
continue;
}
response.resize(static_cast<size_t>(got));
const dnsheader_aligned dnsHeader(response.data());
queryId = dnsHeader->id;
auto ids = dss->getState(queryId);
if (!ids) {
continue;
}
if (!ids->isXSK() && sockDesc != ids->backendFD) {
dss->restoreState(queryId, std::move(*ids));
continue;
}
dnsdist::configuration::refreshLocalRuntimeConfiguration();
if (processResponderPacket(dss, response, std::move(*ids)) && ids->isXSK() && ids->cs->xskInfoResponder) {
#ifdef HAVE_XSK
auto& xskInfo = ids->cs->xskInfoResponder;
auto xskPacket = xskInfo->getEmptyFrame();
if (!xskPacket) {
continue;
}
xskPacket->setHeader(ids->xskPacketHeader);
if (!xskPacket->setPayload(response)) {
}
if (ids->delayMsec > 0) {
xskPacket->addDelay(ids->delayMsec);
}
xskPacket->updatePacket();
xskInfo->pushToSendQueue(*xskPacket);
xskInfo->notifyXskSocket();
#endif /* HAVE_XSK */
}
}
}
catch (const std::exception& e) {
VERBOSESLOG(infolog("Got an error in UDP responder thread while parsing a response from %s, id %d: %s", dss->d_config.remote.toStringWithPort(), queryId, e.what()),
responderLogger->error(Logr::Info, e.what(), "Got an error in UDP responder thread while parsing a response", "dns.response.id", Logging::Loggable(queryId)));
}
}
}
catch (const std::exception& e) {
SLOG(errlog("UDP responder thread died because of exception: %s", e.what()),
responderLogger->error(Logr::Error, e.what(), "UDP responder thread died because of an exception"));
}
catch (const PDNSException& e) {
SLOG(errlog("UDP responder thread died because of PowerDNS exception: %s", e.reason),
responderLogger->error(Logr::Error, e.reason, "UDP responder thread died because of a PowerDNS exception"));
}
catch (...) {
SLOG(errlog("UDP responder thread died because of an exception: %s", "unknown"),
responderLogger->info(Logr::Error, "UDP responder thread died because of an unknown exception"));
}
}
RecursiveLockGuarded<LuaContext> g_lua{LuaContext()};
static void spoofResponseFromString(DNSQuestion& dnsQuestion, const string& spoofContent, bool raw)
{
string result;
if (raw) {
dnsdist::ResponseConfig config;
std::vector<std::string> raws;
stringtok(raws, spoofContent, ",");
dnsdist::self_answers::generateAnswerFromRDataEntries(dnsQuestion, raws, std::nullopt, config);
}
else {
std::vector<std::string> addrs;
stringtok(addrs, spoofContent, " ,");
if (addrs.size() == 1) {
dnsdist::ResponseConfig config;
try {
ComboAddress spoofAddr(spoofContent);
dnsdist::self_answers::generateAnswerFromIPAddresses(dnsQuestion, {spoofAddr}, config);
}
catch (const PDNSException& e) {
DNSName cname(spoofContent);
dnsdist::self_answers::generateAnswerFromCNAME(dnsQuestion, cname, config);
}
}
else {
dnsdist::ResponseConfig config;
std::vector<ComboAddress> cas;
for (const auto& addr : addrs) {
try {
cas.emplace_back(addr);
}
catch (...) {
}
}
dnsdist::self_answers::generateAnswerFromIPAddresses(dnsQuestion, cas, config);
}
}
}
static void spoofPacketFromString(DNSQuestion& dnsQuestion, const string& spoofContent)
{
// NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-pointer-arithmetic)
dnsdist::self_answers::generateAnswerFromRawPacket(dnsQuestion, PacketBuffer(spoofContent.data(), spoofContent.data() + spoofContent.size()));
}
bool processRulesResult(const DNSAction::Action& action, DNSQuestion& dnsQuestion, std::string& ruleresult, bool& drop)
{
if (dnsQuestion.isAsynchronous()) {
return false;
}
auto setRCode = [&dnsQuestion](uint8_t rcode) {
dnsdist::self_answers::removeRecordsAndSetRCode(dnsQuestion, rcode);
};
switch (action) {
case DNSAction::Action::Allow:
return true;
break;
case DNSAction::Action::Drop:
++dnsdist::metrics::g_stats.ruleDrop;
drop = true;
return true;
break;
case DNSAction::Action::Nxdomain:
setRCode(RCode::NXDomain);
return true;
break;
case DNSAction::Action::Refused:
setRCode(RCode::Refused);
return true;
break;
case DNSAction::Action::ServFail:
setRCode(RCode::ServFail);
return true;
break;
case DNSAction::Action::Spoof:
spoofResponseFromString(dnsQuestion, ruleresult, false);
return true;
break;
case DNSAction::Action::SpoofPacket:
spoofPacketFromString(dnsQuestion, ruleresult);
return true;
break;
case DNSAction::Action::SpoofRaw:
spoofResponseFromString(dnsQuestion, ruleresult, true);
return true;
break;
case DNSAction::Action::Truncate:
if (!dnsQuestion.overTCP()) {
dnsdist::PacketMangling::editDNSHeaderFromPacket(dnsQuestion.getMutableData(), [](dnsheader& header) {
header.tc = true;
header.qr = true;
header.ra = header.rd;
header.aa = false;
header.ad = false;
return true;
});
++dnsdist::metrics::g_stats.ruleTruncated;
return true;
}
break;
case DNSAction::Action::HeaderModify:
return true;
break;