aboutsummaryrefslogtreecommitdiff
path: root/src/net.h
blob: 93d36a6e3db8d137ead2a58e45203d7e0e87b863 (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
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_NET_H
#define BITCOIN_NET_H

#include <addrman.h>
#include <chainparams.h>
#include <common/bloom.h>
#include <compat.h>
#include <consensus/amount.h>
#include <crypto/siphash.h>
#include <hash.h>
#include <i2p.h>
#include <net_permissions.h>
#include <netaddress.h>
#include <netbase.h>
#include <policy/feerate.h>
#include <protocol.h>
#include <random.h>
#include <span.h>
#include <streams.h>
#include <sync.h>
#include <threadinterrupt.h>
#include <uint256.h>
#include <util/check.h>

#include <atomic>
#include <condition_variable>
#include <cstdint>
#include <deque>
#include <map>
#include <memory>
#include <optional>
#include <thread>
#include <vector>

class CScheduler;
class CNode;
class BanMan;
struct bilingual_str;

/** Default for -whitelistrelay. */
static const bool DEFAULT_WHITELISTRELAY = true;
/** Default for -whitelistforcerelay. */
static const bool DEFAULT_WHITELISTFORCERELAY = false;

/** Time after which to disconnect, after waiting for a ping response (or inactivity). */
static const int TIMEOUT_INTERVAL = 20 * 60;
/** Run the feeler connection loop once every 2 minutes. **/
static constexpr auto FEELER_INTERVAL = 2min;
/** Run the extra block-relay-only connection loop once every 5 minutes. **/
static constexpr auto EXTRA_BLOCK_RELAY_ONLY_PEER_INTERVAL = 5min;
/** Maximum length of incoming protocol messages (no message over 4 MB is currently acceptable). */
static const unsigned int MAX_PROTOCOL_MESSAGE_LENGTH = 4 * 1000 * 1000;
/** Maximum length of the user agent string in `version` message */
static const unsigned int MAX_SUBVERSION_LENGTH = 256;
/** Maximum number of automatic outgoing nodes over which we'll relay everything (blocks, tx, addrs, etc) */
static const int MAX_OUTBOUND_FULL_RELAY_CONNECTIONS = 8;
/** Maximum number of addnode outgoing nodes */
static const int MAX_ADDNODE_CONNECTIONS = 8;
/** Maximum number of block-relay-only outgoing connections */
static const int MAX_BLOCK_RELAY_ONLY_CONNECTIONS = 2;
/** Maximum number of feeler connections */
static const int MAX_FEELER_CONNECTIONS = 1;
/** -listen default */
static const bool DEFAULT_LISTEN = true;
/** The maximum number of peer connections to maintain. */
static const unsigned int DEFAULT_MAX_PEER_CONNECTIONS = 125;
/** The default for -maxuploadtarget. 0 = Unlimited */
static const std::string DEFAULT_MAX_UPLOAD_TARGET{"0M"};
/** Default for blocks only*/
static const bool DEFAULT_BLOCKSONLY = false;
/** -peertimeout default */
static const int64_t DEFAULT_PEER_CONNECT_TIMEOUT = 60;
/** Number of file descriptors required for message capture **/
static const int NUM_FDS_MESSAGE_CAPTURE = 1;

static constexpr bool DEFAULT_FORCEDNSSEED{false};
static constexpr bool DEFAULT_DNSSEED{true};
static constexpr bool DEFAULT_FIXEDSEEDS{true};
static const size_t DEFAULT_MAXRECEIVEBUFFER = 5 * 1000;
static const size_t DEFAULT_MAXSENDBUFFER    = 1 * 1000;

typedef int64_t NodeId;

struct AddedNodeInfo
{
    std::string strAddedNode;
    CService resolvedAddress;
    bool fConnected;
    bool fInbound;
};

class CNodeStats;
class CClientUIInterface;

struct CSerializedNetMsg
{
    CSerializedNetMsg() = default;
    CSerializedNetMsg(CSerializedNetMsg&&) = default;
    CSerializedNetMsg& operator=(CSerializedNetMsg&&) = default;
    // No copying, only moves.
    CSerializedNetMsg(const CSerializedNetMsg& msg) = delete;
    CSerializedNetMsg& operator=(const CSerializedNetMsg&) = delete;

    std::vector<unsigned char> data;
    std::string m_type;
};

/** Different types of connections to a peer. This enum encapsulates the
 * information we have available at the time of opening or accepting the
 * connection. Aside from INBOUND, all types are initiated by us.
 *
 * If adding or removing types, please update CONNECTION_TYPE_DOC in
 * src/rpc/net.cpp and src/qt/rpcconsole.cpp, as well as the descriptions in
 * src/qt/guiutil.cpp and src/bitcoin-cli.cpp::NetinfoRequestHandler. */
enum class ConnectionType {
    /**
     * Inbound connections are those initiated by a peer. This is the only
     * property we know at the time of connection, until P2P messages are
     * exchanged.
     */
    INBOUND,

    /**
     * These are the default connections that we use to connect with the
     * network. There is no restriction on what is relayed; by default we relay
     * blocks, addresses & transactions. We automatically attempt to open
     * MAX_OUTBOUND_FULL_RELAY_CONNECTIONS using addresses from our AddrMan.
     */
    OUTBOUND_FULL_RELAY,


    /**
     * We open manual connections to addresses that users explicitly requested
     * via the addnode RPC or the -addnode/-connect configuration options. Even if a
     * manual connection is misbehaving, we do not automatically disconnect or
     * add it to our discouragement filter.
     */
    MANUAL,

    /**
     * Feeler connections are short-lived connections made to check that a node
     * is alive. They can be useful for:
     * - test-before-evict: if one of the peers is considered for eviction from
     *   our AddrMan because another peer is mapped to the same slot in the tried table,
     *   evict only if this longer-known peer is offline.
     * - move node addresses from New to Tried table, so that we have more
     *   connectable addresses in our AddrMan.
     * Note that in the literature ("Eclipse Attacks on Bitcoin’s Peer-to-Peer Network")
     * only the latter feature is referred to as "feeler connections",
     * although in our codebase feeler connections encompass test-before-evict as well.
     * We make these connections approximately every FEELER_INTERVAL:
     * first we resolve previously found collisions if they exist (test-before-evict),
     * otherwise we connect to a node from the new table.
     */
    FEELER,

    /**
     * We use block-relay-only connections to help prevent against partition
     * attacks. By not relaying transactions or addresses, these connections
     * are harder to detect by a third party, thus helping obfuscate the
     * network topology. We automatically attempt to open
     * MAX_BLOCK_RELAY_ONLY_ANCHORS using addresses from our anchors.dat. Then
     * addresses from our AddrMan if MAX_BLOCK_RELAY_ONLY_CONNECTIONS
     * isn't reached yet.
     */
    BLOCK_RELAY,

    /**
     * AddrFetch connections are short lived connections used to solicit
     * addresses from peers. These are initiated to addresses submitted via the
     * -seednode command line argument, or under certain conditions when the
     * AddrMan is empty.
     */
    ADDR_FETCH,
};

/** Convert ConnectionType enum to a string value */
std::string ConnectionTypeAsString(ConnectionType conn_type);
void Discover();
uint16_t GetListenPort();

enum
{
    LOCAL_NONE,   // unknown
    LOCAL_IF,     // address a local interface listens on
    LOCAL_BIND,   // address explicit bound to
    LOCAL_MAPPED, // address reported by UPnP or NAT-PMP
    LOCAL_MANUAL, // address explicitly specified (-externalip=)

    LOCAL_MAX
};

bool IsPeerAddrLocalGood(CNode *pnode);
/** Returns a local address that we should advertise to this peer */
std::optional<CAddress> GetLocalAddrForPeer(CNode *pnode);

/**
 * Mark a network as reachable or unreachable (no automatic connects to it)
 * @note Networks are reachable by default
 */
void SetReachable(enum Network net, bool reachable);
/** @returns true if the network is reachable, false otherwise */
bool IsReachable(enum Network net);
/** @returns true if the address is in a reachable network, false otherwise */
bool IsReachable(const CNetAddr& addr);

bool AddLocal(const CService& addr, int nScore = LOCAL_NONE);
bool AddLocal(const CNetAddr& addr, int nScore = LOCAL_NONE);
void RemoveLocal(const CService& addr);
bool SeenLocal(const CService& addr);
bool IsLocal(const CService& addr);
bool GetLocal(CService &addr, const CNetAddr *paddrPeer = nullptr);
CAddress GetLocalAddress(const CNetAddr *paddrPeer, ServiceFlags nLocalServices);


extern bool fDiscover;
extern bool fListen;

/** Subversion as sent to the P2P network in `version` messages */
extern std::string strSubVersion;

struct LocalServiceInfo {
    int nScore;
    uint16_t nPort;
};

extern RecursiveMutex cs_mapLocalHost;
extern std::map<CNetAddr, LocalServiceInfo> mapLocalHost GUARDED_BY(cs_mapLocalHost);

extern const std::string NET_MESSAGE_COMMAND_OTHER;
typedef std::map<std::string, uint64_t> mapMsgCmdSize; //command, total bytes

class CNodeStats
{
public:
    NodeId nodeid;
    ServiceFlags nServices;
    bool fRelayTxes;
    int64_t nLastSend;
    int64_t nLastRecv;
    int64_t nLastTXTime;
    int64_t nLastBlockTime;
    int64_t nTimeConnected;
    int64_t nTimeOffset;
    std::string m_addr_name;
    int nVersion;
    std::string cleanSubVer;
    bool fInbound;
    bool m_bip152_highbandwidth_to;
    bool m_bip152_highbandwidth_from;
    int m_starting_height;
    uint64_t nSendBytes;
    mapMsgCmdSize mapSendBytesPerMsgCmd;
    uint64_t nRecvBytes;
    mapMsgCmdSize mapRecvBytesPerMsgCmd;
    NetPermissionFlags m_permissionFlags;
    std::chrono::microseconds m_last_ping_time;
    std::chrono::microseconds m_min_ping_time;
    CAmount minFeeFilter;
    // Our address, as reported by the peer
    std::string addrLocal;
    // Address of this peer
    CAddress addr;
    // Bind address of our side of the connection
    CAddress addrBind;
    // Network the peer connected through
    Network m_network;
    uint32_t m_mapped_as;
    ConnectionType m_conn_type;
};


/** Transport protocol agnostic message container.
 * Ideally it should only contain receive time, payload,
 * command and size.
 */
class CNetMessage {
public:
    CDataStream m_recv;                  //!< received message data
    std::chrono::microseconds m_time{0}; //!< time of message receipt
    uint32_t m_message_size{0};          //!< size of the payload
    uint32_t m_raw_message_size{0};      //!< used wire size of the message (including header/checksum)
    std::string m_command;

    CNetMessage(CDataStream&& recv_in) : m_recv(std::move(recv_in)) {}

    void SetVersion(int nVersionIn)
    {
        m_recv.SetVersion(nVersionIn);
    }
};

/** The TransportDeserializer takes care of holding and deserializing the
 * network receive buffer. It can deserialize the network buffer into a
 * transport protocol agnostic CNetMessage (command & payload)
 */
class TransportDeserializer {
public:
    // returns true if the current deserialization is complete
    virtual bool Complete() const = 0;
    // set the serialization context version
    virtual void SetVersion(int version) = 0;
    /** read and deserialize data, advances msg_bytes data pointer */
    virtual int Read(Span<const uint8_t>& msg_bytes) = 0;
    // decomposes a message from the context
    virtual CNetMessage GetMessage(std::chrono::microseconds time, bool& reject_message) = 0;
    virtual ~TransportDeserializer() {}
};

class V1TransportDeserializer final : public TransportDeserializer
{
private:
    const CChainParams& m_chain_params;
    const NodeId m_node_id; // Only for logging
    mutable CHash256 hasher;
    mutable uint256 data_hash;
    bool in_data;                   // parsing header (false) or data (true)
    CDataStream hdrbuf;             // partially received header
    CMessageHeader hdr;             // complete header
    CDataStream vRecv;              // received message data
    unsigned int nHdrPos;
    unsigned int nDataPos;

    const uint256& GetMessageHash() const;
    int readHeader(Span<const uint8_t> msg_bytes);
    int readData(Span<const uint8_t> msg_bytes);

    void Reset() {
        vRecv.clear();
        hdrbuf.clear();
        hdrbuf.resize(24);
        in_data = false;
        nHdrPos = 0;
        nDataPos = 0;
        data_hash.SetNull();
        hasher.Reset();
    }

public:
    V1TransportDeserializer(const CChainParams& chain_params, const NodeId node_id, int nTypeIn, int nVersionIn)
        : m_chain_params(chain_params),
          m_node_id(node_id),
          hdrbuf(nTypeIn, nVersionIn),
          vRecv(nTypeIn, nVersionIn)
    {
        Reset();
    }

    bool Complete() const override
    {
        if (!in_data)
            return false;
        return (hdr.nMessageSize == nDataPos);
    }
    void SetVersion(int nVersionIn) override
    {
        hdrbuf.SetVersion(nVersionIn);
        vRecv.SetVersion(nVersionIn);
    }
    int Read(Span<const uint8_t>& msg_bytes) override
    {
        int ret = in_data ? readData(msg_bytes) : readHeader(msg_bytes);
        if (ret < 0) {
            Reset();
        } else {
            msg_bytes = msg_bytes.subspan(ret);
        }
        return ret;
    }
    CNetMessage GetMessage(std::chrono::microseconds time, bool& reject_message) override;
};

/** The TransportSerializer prepares messages for the network transport
 */
class TransportSerializer {
public:
    // prepare message for transport (header construction, error-correction computation, payload encryption, etc.)
    virtual void prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) = 0;
    virtual ~TransportSerializer() {}
};

class V1TransportSerializer  : public TransportSerializer {
public:
    void prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) override;
};

/** Information about a peer */
class CNode
{
    friend class CConnman;
    friend struct ConnmanTestMsg;

public:
    std::unique_ptr<TransportDeserializer> m_deserializer;
    std::unique_ptr<TransportSerializer> m_serializer;

    NetPermissionFlags m_permissionFlags{NetPermissionFlags::None};
    std::atomic<ServiceFlags> nServices{NODE_NONE};
    SOCKET hSocket GUARDED_BY(cs_hSocket);
    /** Total size of all vSendMsg entries */
    size_t nSendSize GUARDED_BY(cs_vSend){0};
    /** Offset inside the first vSendMsg already sent */
    size_t nSendOffset GUARDED_BY(cs_vSend){0};
    uint64_t nSendBytes GUARDED_BY(cs_vSend){0};
    std::deque<std::vector<unsigned char>> vSendMsg GUARDED_BY(cs_vSend);
    Mutex cs_vSend;
    Mutex cs_hSocket;
    Mutex cs_vRecv;

    RecursiveMutex cs_vProcessMsg;
    std::list<CNetMessage> vProcessMsg GUARDED_BY(cs_vProcessMsg);
    size_t nProcessQueueSize{0};

    RecursiveMutex cs_sendProcessing;

    uint64_t nRecvBytes GUARDED_BY(cs_vRecv){0};

    std::atomic<int64_t> nLastSend{0};
    std::atomic<int64_t> nLastRecv{0};
    //! Unix epoch time at peer connection, in seconds.
    const int64_t nTimeConnected;
    std::atomic<int64_t> nTimeOffset{0};
    // Address of this peer
    const CAddress addr;
    // Bind address of our side of the connection
    const CAddress addrBind;
    const std::string m_addr_name;
    //! Whether this peer is an inbound onion, i.e. connected via our Tor onion service.
    const bool m_inbound_onion;
    std::atomic<int> nVersion{0};
    RecursiveMutex cs_SubVer;
    /**
     * cleanSubVer is a sanitized string of the user agent byte array we read
     * from the wire. This cleaned string can safely be logged or displayed.
     */
    std::string cleanSubVer GUARDED_BY(cs_SubVer){};
    bool m_prefer_evict{false}; // This peer is preferred for eviction.
    bool HasPermission(NetPermissionFlags permission) const {
        return NetPermissions::HasFlag(m_permissionFlags, permission);
    }
    bool fClient{false}; // set by version message
    bool m_limited_node{false}; //after BIP159, set by version message
    /** fSuccessfullyConnected is set to true on receiving VERACK from the peer. */
    std::atomic_bool fSuccessfullyConnected{false};
    // Setting fDisconnect to true will cause the node to be disconnected the
    // next time DisconnectNodes() runs
    std::atomic_bool fDisconnect{false};
    CSemaphoreGrant grantOutbound;
    std::atomic<int> nRefCount{0};

    const uint64_t nKeyedNetGroup;
    std::atomic_bool fPauseRecv{false};
    std::atomic_bool fPauseSend{false};

    bool IsOutboundOrBlockRelayConn() const {
        switch (m_conn_type) {
            case ConnectionType::OUTBOUND_FULL_RELAY:
            case ConnectionType::BLOCK_RELAY:
                return true;
            case ConnectionType::INBOUND:
            case ConnectionType::MANUAL:
            case ConnectionType::ADDR_FETCH:
            case ConnectionType::FEELER:
                return false;
        } // no default case, so the compiler can warn about missing cases

        assert(false);
    }

    bool IsFullOutboundConn() const {
        return m_conn_type == ConnectionType::OUTBOUND_FULL_RELAY;
    }

    bool IsManualConn() const {
        return m_conn_type == ConnectionType::MANUAL;
    }

    bool IsBlockOnlyConn() const {
        return m_conn_type == ConnectionType::BLOCK_RELAY;
    }

    bool IsFeelerConn() const {
        return m_conn_type == ConnectionType::FEELER;
    }

    bool IsAddrFetchConn() const {
        return m_conn_type == ConnectionType::ADDR_FETCH;
    }

    bool IsInboundConn() const {
        return m_conn_type == ConnectionType::INBOUND;
    }

    bool ExpectServicesFromConn() const {
        switch (m_conn_type) {
            case ConnectionType::INBOUND:
            case ConnectionType::MANUAL:
            case ConnectionType::FEELER:
                return false;
            case ConnectionType::OUTBOUND_FULL_RELAY:
            case ConnectionType::BLOCK_RELAY:
            case ConnectionType::ADDR_FETCH:
                return true;
        } // no default case, so the compiler can warn about missing cases

        assert(false);
    }

    /**
     * Get network the peer connected through.
     *
     * Returns Network::NET_ONION for *inbound* onion connections,
     * and CNetAddr::GetNetClass() otherwise. The latter cannot be used directly
     * because it doesn't detect the former, and it's not the responsibility of
     * the CNetAddr class to know the actual network a peer is connected through.
     *
     * @return network the peer connected through.
     */
    Network ConnectedThroughNetwork() const;

    // We selected peer as (compact blocks) high-bandwidth peer (BIP152)
    std::atomic<bool> m_bip152_highbandwidth_to{false};
    // Peer selected us as (compact blocks) high-bandwidth peer (BIP152)
    std::atomic<bool> m_bip152_highbandwidth_from{false};

    struct TxRelay {
        mutable RecursiveMutex cs_filter;
        // We use fRelayTxes for two purposes -
        // a) it allows us to not relay tx invs before receiving the peer's version message
        // b) the peer may tell us in its version message that we should not relay tx invs
        //    unless it loads a bloom filter.
        bool fRelayTxes GUARDED_BY(cs_filter){false};
        std::unique_ptr<CBloomFilter> pfilter PT_GUARDED_BY(cs_filter) GUARDED_BY(cs_filter){nullptr};

        mutable RecursiveMutex cs_tx_inventory;
        CRollingBloomFilter filterInventoryKnown GUARDED_BY(cs_tx_inventory){50000, 0.000001};
        // Set of transaction ids we still have to announce.
        // They are sorted by the mempool before relay, so the order is not important.
        std::set<uint256> setInventoryTxToSend;
        // Used for BIP35 mempool sending
        bool fSendMempool GUARDED_BY(cs_tx_inventory){false};
        // Last time a "MEMPOOL" request was serviced.
        std::atomic<std::chrono::seconds> m_last_mempool_req{0s};
        std::chrono::microseconds nNextInvSend{0};

        /** Minimum fee rate with which to filter inv's to this node */
        std::atomic<CAmount> minFeeFilter{0};
        CAmount lastSentFeeFilter{0};
        std::chrono::microseconds m_next_send_feefilter{0};
    };

    // m_tx_relay == nullptr if we're not relaying transactions with this peer
    std::unique_ptr<TxRelay> m_tx_relay;

    /** UNIX epoch time of the last block received from this peer that we had
     * not yet seen (e.g. not already received from another peer), that passed
     * preliminary validity checks and was saved to disk, even if we don't
     * connect the block or it eventually fails connection. Used as an inbound
     * peer eviction criterium in CConnman::AttemptToEvictConnection. */
    std::atomic<int64_t> nLastBlockTime{0};

    /** UNIX epoch time of the last transaction received from this peer that we
     * had not yet seen (e.g. not already received from another peer) and that
     * was accepted into our mempool. Used as an inbound peer eviction criterium
     * in CConnman::AttemptToEvictConnection. */
    std::atomic<int64_t> nLastTXTime{0};

    /** Last measured round-trip time. Used only for RPC/GUI stats/debugging.*/
    std::atomic<std::chrono::microseconds> m_last_ping_time{0us};

    /** Lowest measured round-trip time. Used as an inbound peer eviction
     * criterium in CConnman::AttemptToEvictConnection. */
    std::atomic<std::chrono::microseconds> m_min_ping_time{std::chrono::microseconds::max()};

    CNode(NodeId id, ServiceFlags nLocalServicesIn, SOCKET hSocketIn, const CAddress& addrIn, uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn, const CAddress& addrBindIn, const std::string& addrNameIn, ConnectionType conn_type_in, bool inbound_onion);
    ~CNode();
    CNode(const CNode&) = delete;
    CNode& operator=(const CNode&) = delete;

    NodeId GetId() const {
        return id;
    }

    uint64_t GetLocalNonce() const {
        return nLocalHostNonce;
    }

    int GetRefCount() const
    {
        assert(nRefCount >= 0);
        return nRefCount;
    }

    /**
     * Receive bytes from the buffer and deserialize them into messages.
     *
     * @param[in]   msg_bytes   The raw data
     * @param[out]  complete    Set True if at least one message has been
     *                          deserialized and is ready to be processed
     * @return  True if the peer should stay connected,
     *          False if the peer should be disconnected from.
     */
    bool ReceiveMsgBytes(Span<const uint8_t> msg_bytes, bool& complete);

    void SetCommonVersion(int greatest_common_version)
    {
        Assume(m_greatest_common_version == INIT_PROTO_VERSION);
        m_greatest_common_version = greatest_common_version;
    }
    int GetCommonVersion() const
    {
        return m_greatest_common_version;
    }

    CService GetAddrLocal() const;
    //! May not be called more than once
    void SetAddrLocal(const CService& addrLocalIn);

    CNode* AddRef()
    {
        nRefCount++;
        return this;
    }

    void Release()
    {
        nRefCount--;
    }

    void AddKnownTx(const uint256& hash)
    {
        if (m_tx_relay != nullptr) {
            LOCK(m_tx_relay->cs_tx_inventory);
            m_tx_relay->filterInventoryKnown.insert(hash);
        }
    }

    void PushTxInventory(const uint256& hash)
    {
        if (m_tx_relay == nullptr) return;
        LOCK(m_tx_relay->cs_tx_inventory);
        if (!m_tx_relay->filterInventoryKnown.contains(hash)) {
            m_tx_relay->setInventoryTxToSend.insert(hash);
        }
    }

    void CloseSocketDisconnect();

    void CopyStats(CNodeStats& stats);

    ServiceFlags GetLocalServices() const
    {
        return nLocalServices;
    }

    std::string ConnectionTypeAsString() const { return ::ConnectionTypeAsString(m_conn_type); }

    /** A ping-pong round trip has completed successfully. Update latest and minimum ping times. */
    void PongReceived(std::chrono::microseconds ping_time) {
        m_last_ping_time = ping_time;
        m_min_ping_time = std::min(m_min_ping_time.load(), ping_time);
    }

private:
    const NodeId id;
    const uint64_t nLocalHostNonce;
    const ConnectionType m_conn_type;
    std::atomic<int> m_greatest_common_version{INIT_PROTO_VERSION};

    //! Services offered to this peer.
    //!
    //! This is supplied by the parent CConnman during peer connection
    //! (CConnman::ConnectNode()) from its attribute of the same name.
    //!
    //! This is const because there is no protocol defined for renegotiating
    //! services initially offered to a peer. The set of local services we
    //! offer should not change after initialization.
    //!
    //! An interesting example of this is NODE_NETWORK and initial block
    //! download: a node which starts up from scratch doesn't have any blocks
    //! to serve, but still advertises NODE_NETWORK because it will eventually
    //! fulfill this role after IBD completes. P2P code is written in such a
    //! way that it can gracefully handle peers who don't make good on their
    //! service advertisements.
    const ServiceFlags nLocalServices;

    std::list<CNetMessage> vRecvMsg; // Used only by SocketHandler thread

    // Our address, as reported by the peer
    CService addrLocal GUARDED_BY(cs_addrLocal);
    mutable RecursiveMutex cs_addrLocal;

    mapMsgCmdSize mapSendBytesPerMsgCmd GUARDED_BY(cs_vSend);
    mapMsgCmdSize mapRecvBytesPerMsgCmd GUARDED_BY(cs_vRecv);
};

/**
 * Interface for message handling
 */
class NetEventsInterface
{
public:
    /** Initialize a peer (setup state, queue any initial messages) */
    virtual void InitializeNode(CNode* pnode) = 0;

    /** Handle removal of a peer (clear state) */
    virtual void FinalizeNode(const CNode& node) = 0;

    /**
    * Process protocol messages received from a given node
    *
    * @param[in]   pnode           The node which we have received messages from.
    * @param[in]   interrupt       Interrupt condition for processing threads
    * @return                      True if there is more work to be done
    */
    virtual bool ProcessMessages(CNode* pnode, std::atomic<bool>& interrupt) = 0;

    /**
    * Send queued protocol messages to a given node.
    *
    * @param[in]   pnode           The node which we are sending messages to.
    * @return                      True if there is more work to be done
    */
    virtual bool SendMessages(CNode* pnode) EXCLUSIVE_LOCKS_REQUIRED(pnode->cs_sendProcessing) = 0;


protected:
    /**
     * Protected destructor so that instances can only be deleted by derived classes.
     * If that restriction is no longer desired, this should be made public and virtual.
     */
    ~NetEventsInterface() = default;
};

class CConnman
{
public:

    struct Options
    {
        ServiceFlags nLocalServices = NODE_NONE;
        int nMaxConnections = 0;
        int m_max_outbound_full_relay = 0;
        int m_max_outbound_block_relay = 0;
        int nMaxAddnode = 0;
        int nMaxFeeler = 0;
        CClientUIInterface* uiInterface = nullptr;
        NetEventsInterface* m_msgproc = nullptr;
        BanMan* m_banman = nullptr;
        unsigned int nSendBufferMaxSize = 0;
        unsigned int nReceiveFloodSize = 0;
        uint64_t nMaxOutboundLimit = 0;
        int64_t m_peer_connect_timeout = DEFAULT_PEER_CONNECT_TIMEOUT;
        std::vector<std::string> vSeedNodes;
        std::vector<NetWhitelistPermissions> vWhitelistedRange;
        std::vector<NetWhitebindPermissions> vWhiteBinds;
        std::vector<CService> vBinds;
        std::vector<CService> onion_binds;
        /// True if the user did not specify -bind= or -whitebind= and thus
        /// we should bind on `0.0.0.0` (IPv4) and `::` (IPv6).
        bool bind_on_any;
        bool m_use_addrman_outgoing = true;
        std::vector<std::string> m_specified_outgoing;
        std::vector<std::string> m_added_nodes;
        bool m_i2p_accept_incoming;
    };

    void Init(const Options& connOptions) {
        nLocalServices = connOptions.nLocalServices;
        nMaxConnections = connOptions.nMaxConnections;
        m_max_outbound_full_relay = std::min(connOptions.m_max_outbound_full_relay, connOptions.nMaxConnections);
        m_max_outbound_block_relay = connOptions.m_max_outbound_block_relay;
        m_use_addrman_outgoing = connOptions.m_use_addrman_outgoing;
        nMaxAddnode = connOptions.nMaxAddnode;
        nMaxFeeler = connOptions.nMaxFeeler;
        m_max_outbound = m_max_outbound_full_relay + m_max_outbound_block_relay + nMaxFeeler;
        m_client_interface = connOptions.uiInterface;
        m_banman = connOptions.m_banman;
        m_msgproc = connOptions.m_msgproc;
        nSendBufferMaxSize = connOptions.nSendBufferMaxSize;
        nReceiveFloodSize = connOptions.nReceiveFloodSize;
        m_peer_connect_timeout = connOptions.m_peer_connect_timeout;
        {
            LOCK(cs_totalBytesSent);
            nMaxOutboundLimit = connOptions.nMaxOutboundLimit;
        }
        vWhitelistedRange = connOptions.vWhitelistedRange;
        {
            LOCK(m_added_nodes_mutex);
            m_added_nodes = connOptions.m_added_nodes;
        }
        m_onion_binds = connOptions.onion_binds;
    }

    CConnman(uint64_t seed0, uint64_t seed1, AddrMan& addrman, bool network_active = true);
    ~CConnman();
    bool Start(CScheduler& scheduler, const Options& options);

    void StopThreads();
    void StopNodes();
    void Stop()
    {
        StopThreads();
        StopNodes();
    };

    void Interrupt();
    bool GetNetworkActive() const { return fNetworkActive; };
    bool GetUseAddrmanOutgoing() const { return m_use_addrman_outgoing; };
    void SetNetworkActive(bool active);
    void OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant* grantOutbound, const char* strDest, ConnectionType conn_type);
    bool CheckIncomingNonce(uint64_t nonce);

    bool ForNode(NodeId id, std::function<bool(CNode* pnode)> func);

    void PushMessage(CNode* pnode, CSerializedNetMsg&& msg);

    using NodeFn = std::function<void(CNode*)>;
    void ForEachNode(const NodeFn& func)
    {
        LOCK(m_nodes_mutex);
        for (auto&& node : m_nodes) {
            if (NodeFullyConnected(node))
                func(node);
        }
    };

    void ForEachNode(const NodeFn& func) const
    {
        LOCK(m_nodes_mutex);
        for (auto&& node : m_nodes) {
            if (NodeFullyConnected(node))
                func(node);
        }
    };

    // Addrman functions
    /**
     * Return all or many randomly selected addresses, optionally by network.
     *
     * @param[in] max_addresses  Maximum number of addresses to return (0 = all).
     * @param[in] max_pct        Maximum percentage of addresses to return (0 = all).
     * @param[in] network        Select only addresses of this network (nullopt = all).
     */
    std::vector<CAddress> GetAddresses(size_t max_addresses, size_t max_pct, std::optional<Network> network) const;
    /**
     * Cache is used to minimize topology leaks, so it should
     * be used for all non-trusted calls, for example, p2p.
     * A non-malicious call (from RPC or a peer with addr permission) should
     * call the function without a parameter to avoid using the cache.
     */
    std::vector<CAddress> GetAddresses(CNode& requestor, size_t max_addresses, size_t max_pct);

    // This allows temporarily exceeding m_max_outbound_full_relay, with the goal of finding
    // a peer that is better than all our current peers.
    void SetTryNewOutboundPeer(bool flag);
    bool GetTryNewOutboundPeer() const;

    void StartExtraBlockRelayPeers() {
        LogPrint(BCLog::NET, "net: enabling extra block-relay-only peers\n");
        m_start_extra_block_relay_peers = true;
    }

    // Return the number of outbound peers we have in excess of our target (eg,
    // if we previously called SetTryNewOutboundPeer(true), and have since set
    // to false, we may have extra peers that we wish to disconnect). This may
    // return a value less than (num_outbound_connections - num_outbound_slots)
    // in cases where some outbound connections are not yet fully connected, or
    // not yet fully disconnected.
    int GetExtraFullOutboundCount() const;
    // Count the number of block-relay-only peers we have over our limit.
    int GetExtraBlockRelayCount() const;

    bool AddNode(const std::string& node);
    bool RemoveAddedNode(const std::string& node);
    std::vector<AddedNodeInfo> GetAddedNodeInfo() const;

    /**
     * Attempts to open a connection. Currently only used from tests.
     *
     * @param[in]   address     Address of node to try connecting to
     * @param[in]   conn_type   ConnectionType::OUTBOUND or ConnectionType::BLOCK_RELAY
     *                          or ConnectionType::ADDR_FETCH
     * @return      bool        Returns false if there are no available
     *                          slots for this connection:
     *                          - conn_type not a supported ConnectionType
     *                          - Max total outbound connection capacity filled
     *                          - Max connection capacity for type is filled
     */
    bool AddConnection(const std::string& address, ConnectionType conn_type);

    size_t GetNodeCount(ConnectionDirection) const;
    void GetNodeStats(std::vector<CNodeStats>& vstats) const;
    bool DisconnectNode(const std::string& node);
    bool DisconnectNode(const CSubNet& subnet);
    bool DisconnectNode(const CNetAddr& addr);
    bool DisconnectNode(NodeId id);

    //! Used to convey which local services we are offering peers during node
    //! connection.
    //!
    //! The data returned by this is used in CNode construction,
    //! which is used to advertise which services we are offering
    //! that peer during `net_processing.cpp:PushNodeVersion()`.
    ServiceFlags GetLocalServices() const;

    uint64_t GetMaxOutboundTarget() const;
    std::chrono::seconds GetMaxOutboundTimeframe() const;

    //! check if the outbound target is reached
    //! if param historicalBlockServingLimit is set true, the function will
    //! response true if the limit for serving historical blocks has been reached
    bool OutboundTargetReached(bool historicalBlockServingLimit) const;

    //! response the bytes left in the current max outbound cycle
    //! in case of no limit, it will always response 0
    uint64_t GetOutboundTargetBytesLeft() const;

    //! returns the time left in the current max outbound cycle
    //! in case of no limit, it will always return 0
    std::chrono::seconds GetMaxOutboundTimeLeftInCycle() const;

    uint64_t GetTotalBytesRecv() const;
    uint64_t GetTotalBytesSent() const;

    /** Get a unique deterministic randomizer. */
    CSipHasher GetDeterministicRandomizer(uint64_t id) const;

    unsigned int GetReceiveFloodSize() const;

    void WakeMessageHandler();

    /** Attempts to obfuscate tx time through exponentially distributed emitting.
        Works assuming that a single interval is used.
        Variable intervals will result in privacy decrease.
    */
    std::chrono::microseconds PoissonNextSendInbound(std::chrono::microseconds now, std::chrono::seconds average_interval);

    /** Return true if we should disconnect the peer for failing an inactivity check. */
    bool ShouldRunInactivityChecks(const CNode& node, int64_t secs_now) const;

private:
    struct ListenSocket {
    public:
        SOCKET socket;
        inline void AddSocketPermissionFlags(NetPermissionFlags& flags) const { NetPermissions::AddFlag(flags, m_permissions); }
        ListenSocket(SOCKET socket_, NetPermissionFlags permissions_) : socket(socket_), m_permissions(permissions_) {}
    private:
        NetPermissionFlags m_permissions;
    };

    bool BindListenPort(const CService& bindAddr, bilingual_str& strError, NetPermissionFlags permissions);
    bool Bind(const CService& addr, unsigned int flags, NetPermissionFlags permissions);
    bool InitBinds(const Options& options);

    void ThreadOpenAddedConnections();
    void AddAddrFetch(const std::string& strDest);
    void ProcessAddrFetch();
    void ThreadOpenConnections(std::vector<std::string> connect);
    void ThreadMessageHandler();
    void ThreadI2PAcceptIncoming();
    void AcceptConnection(const ListenSocket& hListenSocket);

    /**
     * Create a `CNode` object from a socket that has just been accepted and add the node to
     * the `m_nodes` member.
     * @param[in] hSocket Connected socket to communicate with the peer.
     * @param[in] permissionFlags The peer's permissions.
     * @param[in] addr_bind The address and port at our side of the connection.
     * @param[in] addr The address and port at the peer's side of the connection.
     */
    void CreateNodeFromAcceptedSocket(SOCKET hSocket,
                                      NetPermissionFlags permissionFlags,
                                      const CAddress& addr_bind,
                                      const CAddress& addr);

    void DisconnectNodes();
    void NotifyNumConnectionsChanged();
    /** Return true if the peer is inactive and should be disconnected. */
    bool InactivityCheck(const CNode& node) const;

    /**
     * Generate a collection of sockets to check for IO readiness.
     * @param[in] nodes Select from these nodes' sockets.
     * @param[out] recv_set Sockets to check for read readiness.
     * @param[out] send_set Sockets to check for write readiness.
     * @param[out] error_set Sockets to check for errors.
     * @return true if at least one socket is to be checked (the returned set is not empty)
     */
    bool GenerateSelectSet(const std::vector<CNode*>& nodes,
                           std::set<SOCKET>& recv_set,
                           std::set<SOCKET>& send_set,
                           std::set<SOCKET>& error_set);

    /**
     * Check which sockets are ready for IO.
     * @param[in] nodes Select from these nodes' sockets.
     * @param[out] recv_set Sockets which are ready for read.
     * @param[out] send_set Sockets which are ready for write.
     * @param[out] error_set Sockets which have errors.
     * This calls `GenerateSelectSet()` to gather a list of sockets to check.
     */
    void SocketEvents(const std::vector<CNode*>& nodes,
                      std::set<SOCKET>& recv_set,
                      std::set<SOCKET>& send_set,
                      std::set<SOCKET>& error_set);

    /**
     * Check connected and listening sockets for IO readiness and process them accordingly.
     */
    void SocketHandler();

    /**
     * Do the read/write for connected sockets that are ready for IO.
     * @param[in] nodes Nodes to process. The socket of each node is checked against
     * `recv_set`, `send_set` and `error_set`.
     * @param[in] recv_set Sockets that are ready for read.
     * @param[in] send_set Sockets that are ready for send.
     * @param[in] error_set Sockets that have an exceptional condition (error).
     */
    void SocketHandlerConnected(const std::vector<CNode*>& nodes,
                                const std::set<SOCKET>& recv_set,
                                const std::set<SOCKET>& send_set,
                                const std::set<SOCKET>& error_set);

    /**
     * Accept incoming connections, one from each read-ready listening socket.
     * @param[in] recv_set Sockets that are ready for read.
     */
    void SocketHandlerListening(const std::set<SOCKET>& recv_set);

    void ThreadSocketHandler();
    void ThreadDNSAddressSeed();

    uint64_t CalculateKeyedNetGroup(const CAddress& ad) const;

    CNode* FindNode(const CNetAddr& ip);
    CNode* FindNode(const CSubNet& subNet);
    CNode* FindNode(const std::string& addrName);
    CNode* FindNode(const CService& addr);

    /**
     * Determine whether we're already connected to a given address, in order to
     * avoid initiating duplicate connections.
     */
    bool AlreadyConnectedToAddress(const CAddress& addr);

    bool AttemptToEvictConnection();
    CNode* ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, ConnectionType conn_type);
    void AddWhitelistPermissionFlags(NetPermissionFlags& flags, const CNetAddr &addr) const;

    void DeleteNode(CNode* pnode);

    NodeId GetNewNodeId();

    size_t SocketSendData(CNode& node) const EXCLUSIVE_LOCKS_REQUIRED(node.cs_vSend);
    void DumpAddresses();

    // Network stats
    void RecordBytesRecv(uint64_t bytes);
    void RecordBytesSent(uint64_t bytes);

    /**
     * Return vector of current BLOCK_RELAY peers.
     */
    std::vector<CAddress> GetCurrentBlockRelayOnlyConns() const;

    // Whether the node should be passed out in ForEach* callbacks
    static bool NodeFullyConnected(const CNode* pnode);

    // Network usage totals
    mutable RecursiveMutex cs_totalBytesSent;
    std::atomic<uint64_t> nTotalBytesRecv{0};
    uint64_t nTotalBytesSent GUARDED_BY(cs_totalBytesSent) {0};

    // outbound limit & stats
    uint64_t nMaxOutboundTotalBytesSentInCycle GUARDED_BY(cs_totalBytesSent) {0};
    std::chrono::seconds nMaxOutboundCycleStartTime GUARDED_BY(cs_totalBytesSent) {0};
    uint64_t nMaxOutboundLimit GUARDED_BY(cs_totalBytesSent);

    // P2P timeout in seconds
    int64_t m_peer_connect_timeout;

    // Whitelisted ranges. Any node connecting from these is automatically
    // whitelisted (as well as those connecting to whitelisted binds).
    std::vector<NetWhitelistPermissions> vWhitelistedRange;

    unsigned int nSendBufferMaxSize{0};
    unsigned int nReceiveFloodSize{0};

    std::vector<ListenSocket> vhListenSocket;
    std::atomic<bool> fNetworkActive{true};
    bool fAddressesInitialized{false};
    AddrMan& addrman;
    std::deque<std::string> m_addr_fetches GUARDED_BY(m_addr_fetches_mutex);
    Mutex m_addr_fetches_mutex;
    std::vector<std::string> m_added_nodes GUARDED_BY(m_added_nodes_mutex);
    mutable RecursiveMutex m_added_nodes_mutex;
    std::vector<CNode*> m_nodes GUARDED_BY(m_nodes_mutex);
    std::list<CNode*> m_nodes_disconnected;
    mutable RecursiveMutex m_nodes_mutex;
    std::atomic<NodeId> nLastNodeId{0};
    unsigned int nPrevNodeCount{0};

    /**
     * Cache responses to addr requests to minimize privacy leak.
     * Attack example: scraping addrs in real-time may allow an attacker
     * to infer new connections of the victim by detecting new records
     * with fresh timestamps (per self-announcement).
     */
    struct CachedAddrResponse {
        std::vector<CAddress> m_addrs_response_cache;
        std::chrono::microseconds m_cache_entry_expiration{0};
    };

    /**
     * Addr responses stored in different caches
     * per (network, local socket) prevent cross-network node identification.
     * If a node for example is multi-homed under Tor and IPv6,
     * a single cache (or no cache at all) would let an attacker
     * to easily detect that it is the same node by comparing responses.
     * Indexing by local socket prevents leakage when a node has multiple
     * listening addresses on the same network.
     *
     * The used memory equals to 1000 CAddress records (or around 40 bytes) per
     * distinct Network (up to 5) we have/had an inbound peer from,
     * resulting in at most ~196 KB. Every separate local socket may
     * add up to ~196 KB extra.
     */
    std::map<uint64_t, CachedAddrResponse> m_addr_response_caches;

    /**
     * Services this instance offers.
     *
     * This data is replicated in each CNode instance we create during peer
     * connection (in ConnectNode()) under a member also called
     * nLocalServices.
     *
     * This data is not marked const, but after being set it should not
     * change. See the note in CNode::nLocalServices documentation.
     *
     * \sa CNode::nLocalServices
     */
    ServiceFlags nLocalServices;

    std::unique_ptr<CSemaphore> semOutbound;
    std::unique_ptr<CSemaphore> semAddnode;
    int nMaxConnections;

    // How many full-relay (tx, block, addr) outbound peers we want
    int m_max_outbound_full_relay;

    // How many block-relay only outbound peers we want
    // We do not relay tx or addr messages with these peers
    int m_max_outbound_block_relay;

    int nMaxAddnode;
    int nMaxFeeler;
    int m_max_outbound;
    bool m_use_addrman_outgoing;
    CClientUIInterface* m_client_interface;
    NetEventsInterface* m_msgproc;
    /** Pointer to this node's banman. May be nullptr - check existence before dereferencing. */
    BanMan* m_banman;

    /**
     * Addresses that were saved during the previous clean shutdown. We'll
     * attempt to make block-relay-only connections to them.
     */
    std::vector<CAddress> m_anchors;

    /** SipHasher seeds for deterministic randomness */
    const uint64_t nSeed0, nSeed1;

    /** flag for waking the message processor. */
    bool fMsgProcWake GUARDED_BY(mutexMsgProc);

    std::condition_variable condMsgProc;
    Mutex mutexMsgProc;
    std::atomic<bool> flagInterruptMsgProc{false};

    /**
     * This is signaled when network activity should cease.
     * A pointer to it is saved in `m_i2p_sam_session`, so make sure that
     * the lifetime of `interruptNet` is not shorter than
     * the lifetime of `m_i2p_sam_session`.
     */
    CThreadInterrupt interruptNet;

    /**
     * I2P SAM session.
     * Used to accept incoming and make outgoing I2P connections.
     */
    std::unique_ptr<i2p::sam::Session> m_i2p_sam_session;

    std::thread threadDNSAddressSeed;
    std::thread threadSocketHandler;
    std::thread threadOpenAddedConnections;
    std::thread threadOpenConnections;
    std::thread threadMessageHandler;
    std::thread threadI2PAcceptIncoming;

    /** flag for deciding to connect to an extra outbound peer,
     *  in excess of m_max_outbound_full_relay
     *  This takes the place of a feeler connection */
    std::atomic_bool m_try_another_outbound_peer;

    /** flag for initiating extra block-relay-only peer connections.
     *  this should only be enabled after initial chain sync has occurred,
     *  as these connections are intended to be short-lived and low-bandwidth.
     */
    std::atomic_bool m_start_extra_block_relay_peers{false};

    std::atomic<std::chrono::microseconds> m_next_send_inv_to_incoming{0us};

    /**
     * A vector of -bind=<address>:<port>=onion arguments each of which is
     * an address and port that are designated for incoming Tor connections.
     */
    std::vector<CService> m_onion_binds;

    /**
     * RAII helper to atomically create a copy of `m_nodes` and add a reference
     * to each of the nodes. The nodes are released when this object is destroyed.
     */
    class NodesSnapshot
    {
    public:
        explicit NodesSnapshot(const CConnman& connman, bool shuffle)
        {
            {
                LOCK(connman.m_nodes_mutex);
                m_nodes_copy = connman.m_nodes;
                for (auto& node : m_nodes_copy) {
                    node->AddRef();
                }
            }
            if (shuffle) {
                Shuffle(m_nodes_copy.begin(), m_nodes_copy.end(), FastRandomContext{});
            }
        }

        ~NodesSnapshot()
        {
            for (auto& node : m_nodes_copy) {
                node->Release();
            }
        }

        const std::vector<CNode*>& Nodes() const
        {
            return m_nodes_copy;
        }

    private:
        std::vector<CNode*> m_nodes_copy;
    };

    friend struct CConnmanTest;
    friend struct ConnmanTestMsg;
};

/** Return a timestamp in the future (in microseconds) for exponentially distributed events. */
std::chrono::microseconds PoissonNextSend(std::chrono::microseconds now, std::chrono::seconds average_interval);

/** Dump binary message to file, with timestamp */
void CaptureMessage(const CAddress& addr, const std::string& msg_type, const Span<const unsigned char>& data, bool is_incoming);

struct NodeEvictionCandidate
{
    NodeId id;
    int64_t nTimeConnected;
    std::chrono::microseconds m_min_ping_time;
    int64_t nLastBlockTime;
    int64_t nLastTXTime;
    bool fRelevantServices;
    bool fRelayTxes;
    bool fBloomFilter;
    uint64_t nKeyedNetGroup;
    bool prefer_evict;
    bool m_is_local;
    Network m_network;
};

/**
 * Select an inbound peer to evict after filtering out (protecting) peers having
 * distinct, difficult-to-forge characteristics. The protection logic picks out
 * fixed numbers of desirable peers per various criteria, followed by (mostly)
 * ratios of desirable or disadvantaged peers. If any eviction candidates
 * remain, the selection logic chooses a peer to evict.
 */
[[nodiscard]] std::optional<NodeId> SelectNodeToEvict(std::vector<NodeEvictionCandidate>&& vEvictionCandidates);

/** Protect desirable or disadvantaged inbound peers from eviction by ratio.
 *
 * This function protects half of the peers which have been connected the
 * longest, to replicate the non-eviction implicit behavior and preclude attacks
 * that start later.
 *
 * Half of these protected spots (1/4 of the total) are reserved for the
 * following categories of peers, sorted by longest uptime, even if they're not
 * longest uptime overall:
 *
 * - onion peers connected via our tor control service
 *
 * - localhost peers, as manually configured hidden services not using
 *   `-bind=addr[:port]=onion` will not be detected as inbound onion connections
 *
 * - I2P peers
 *
 * This helps protect these privacy network peers, which tend to be otherwise
 * disadvantaged under our eviction criteria for their higher min ping times
 * relative to IPv4/IPv6 peers, and favorise the diversity of peer connections.
 */
void ProtectEvictionCandidatesByRatio(std::vector<NodeEvictionCandidate>& vEvictionCandidates);

#endif // BITCOIN_NET_H