1// Copyright (c) 2022-present The Bitcoin Core developers
2// Distributed under the MIT software license, see the accompanying
3// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5#ifndef BITCOIN_NODE_CONNECTION_TYPES_H
6#define BITCOIN_NODE_CONNECTION_TYPES_H
7
8#include <cstdint>
9#include <string>
10
11/** Different types of connections to a peer. This enum encapsulates the
12 * information we have available at the time of opening or accepting the
13 * connection. Aside from INBOUND, all types are initiated by us.
14 *
15 * If adding or removing types, please update CONNECTION_TYPE_DOC in
16 * src/rpc/net.cpp and src/qt/rpcconsole.cpp, as well as the descriptions in
17 * src/qt/guiutil.cpp and src/bitcoin-cli.cpp::NetinfoRequestHandler. */
18enum class ConnectionType {
19    /**
20     * Inbound connections are those initiated by a peer. This is the only
21     * property we know at the time of connection, until P2P messages are
22     * exchanged.
23     */
24    INBOUND,
25
26    /**
27     * These are the default connections that we use to connect with the
28     * network. There is no restriction on what is relayed; by default we relay
29     * blocks, addresses & transactions. We automatically attempt to open
30     * MAX_OUTBOUND_FULL_RELAY_CONNECTIONS using addresses from our AddrMan.
31     */
32    OUTBOUND_FULL_RELAY,
33
34
35    /**
36     * We open manual connections to addresses that users explicitly requested
37     * via the addnode RPC or the -addnode/-connect configuration options. Even if a
38     * manual connection is misbehaving, we do not automatically disconnect or
39     * add it to our discouragement filter.
40     */
41    MANUAL,
42
43    /**
44     * Feeler connections are short-lived connections made to check that a node
45     * is alive. They can be useful for:
46     * - test-before-evict: if one of the peers is considered for eviction from
47     *   our AddrMan because another peer is mapped to the same slot in the tried table,
48     *   evict only if this longer-known peer is offline.
49     * - move node addresses from New to Tried table, so that we have more
50     *   connectable addresses in our AddrMan.
51     * Note that in the literature ("Eclipse Attacks on Bitcoin’s Peer-to-Peer Network")
52     * only the latter feature is referred to as "feeler connections",
53     * although in our codebase feeler connections encompass test-before-evict as well.
54     * We make these connections approximately every FEELER_INTERVAL:
55     * first we resolve previously found collisions if they exist (test-before-evict),
56     * otherwise we connect to a node from the new table.
57     */
58    FEELER,
59
60    /**
61     * We use block-relay-only connections to help prevent against partition
62     * attacks. By not relaying transactions or addresses, these connections
63     * are harder to detect by a third party, thus helping obfuscate the
64     * network topology. We automatically attempt to open
65     * MAX_BLOCK_RELAY_ONLY_ANCHORS using addresses from our anchors.dat. Then
66     * addresses from our AddrMan if MAX_BLOCK_RELAY_ONLY_CONNECTIONS
67     * isn't reached yet.
68     */
69    BLOCK_RELAY,
70
71    /**
72     * AddrFetch connections are short lived connections used to solicit
73     * addresses from peers. These are initiated to addresses submitted via the
74     * -seednode command line argument, or under certain conditions when the
75     * AddrMan is empty.
76     */
77    ADDR_FETCH,
78
79    /**
80     * Private broadcast connections are short-lived and only opened to
81     * privacy networks (Tor, I2P) for relaying privacy-sensitive data (like
82     * our own transactions) and closed afterwards.
83     */
84    PRIVATE_BROADCAST,
85};
86
87/** Convert ConnectionType enum to a string value */
88std::string ConnectionTypeAsString(ConnectionType conn_type);
89
90/** Transport layer version */
91enum class TransportProtocolType : uint8_t {
92    DETECTING, //!< Peer could be v1 or v2
93    V1, //!< Unencrypted, plaintext protocol
94    V2, //!< BIP324 protocol
95};
96
97/** Convert TransportProtocolType enum to a string value */
98std::string TransportTypeAsString(TransportProtocolType transport_type);
99
100#endif // BITCOIN_NODE_CONNECTION_TYPES_H
101