1// Copyright (c) 2021-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_NETGROUP_H
6#define BITCOIN_NETGROUP_H
7
8#include <netaddress.h>
9#include <uint256.h>
10
11#include <cstddef>
12#include <vector>
13
14/**
15 * Netgroup manager
16 */
17class NetGroupManager {
18public:
19    NetGroupManager(const NetGroupManager&) = delete;
20    NetGroupManager(NetGroupManager&&) = default;
21    NetGroupManager& operator=(const NetGroupManager&) = delete;
22    NetGroupManager& operator=(NetGroupManager&&) = delete;
23
24    static NetGroupManager WithEmbeddedAsmap(std::span<const std::byte> asmap) {
25        return NetGroupManager(asmap, {});
26    }
27
28    static NetGroupManager WithLoadedAsmap(std::vector<std::byte>&& asmap) {
29        return NetGroupManager(std::span{asmap}, std::move(asmap));
30    }
31
32    static NetGroupManager NoAsmap() {
33        return NetGroupManager({}, {});
34    }
35
36    /** Get the asmap version, a checksum identifying the asmap being used. */
37    uint256 GetAsmapVersion() const;
38
39    /**
40     * Get the canonical identifier of the network group for address.
41     *
42     * The groups are assigned in a way where it should be costly for an attacker to
43     * obtain addresses with many different group identifiers, even if it is cheap
44     * to obtain addresses with the same identifier.
45     *
46     * @note No two connections will be attempted to addresses with the same network
47     *       group.
48     */
49    std::vector<unsigned char> GetGroup(const CNetAddr& address) const;
50
51    /**
52     *  Get the autonomous system on the BGP path to address.
53     *
54     *  The ip->AS mapping depends on how asmap is constructed.
55     */
56    uint32_t GetMappedAS(const CNetAddr& address) const;
57
58    /**
59     *  Analyze and log current health of ASMap based buckets.
60     */
61    void ASMapHealthCheck(const std::vector<CNetAddr>& clearnet_addrs) const;
62
63    /**
64     *  Indicates whether ASMap is being used for clearnet bucketing.
65     */
66    bool UsingASMap() const;
67
68private:
69    /** Compressed IP->ASN mapping.
70     *
71     * Data may be loaded from a file when a node starts or embedded in the
72     * binary.
73     *
74     * This mapping is then used for bucketing nodes in Addrman and for
75     * ensuring we connect to a diverse set of peers in Connman. The map is
76     * empty if no file was provided.
77     *
78     * If asmap is provided, nodes will be bucketed by AS they belong to, in
79     * order to make impossible for a node to connect to several nodes hosted
80     * in a single AS. This is done in response to Erebus attack, but also to
81     * generally diversify the connections every node creates, especially
82     * useful when a large fraction of nodes operate under a couple of cloud
83     * providers.
84     *
85     * If a new asmap is provided, the existing addrman records are
86     * re-bucketed.
87     *
88     * This is initialized in the constructor, const, and therefore is
89     * thread-safe. m_asmap can either point to m_loaded_asmap which holds
90     * data loaded from an external file at runtime or it can point to embedded
91     * asmap data.
92     */
93    const std::span<const std::byte> m_asmap;
94    std::vector<std::byte> m_loaded_asmap;
95    const uint256 m_asmap_version;
96
97    explicit NetGroupManager(std::span<const std::byte> embedded_asmap, std::vector<std::byte>&& loaded_asmap);
98};
99
100#endif // BITCOIN_NETGROUP_H
101