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// Copyright (c) 2021 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_NETGROUP_H
#define BITCOIN_NETGROUP_H
#include <netaddress.h>
#include <uint256.h>
#include <vector>
/**
* Netgroup manager
*/
class NetGroupManager {
public:
explicit NetGroupManager(std::vector<bool> asmap)
: m_asmap{std::move(asmap)}
{}
/* Get a reference to (const) asmap. May be held as long as NetGroupManager
* exists, since the data is const. */
const std::vector<bool>& GetAsmap() const { return m_asmap; }
/** Get a checksum identifying the asmap being used. */
uint256 GetAsmapChecksum() const;
/**
* Get the canonical identifier of the network group for address.
*
* The groups are assigned in a way where it should be costly for an attacker to
* obtain addresses with many different group identifiers, even if it is cheap
* to obtain addresses with the same identifier.
*
* @note No two connections will be attempted to addresses with the same network
* group.
*/
std::vector<unsigned char> GetGroup(const CNetAddr& address) const;
/**
* Get the autonomous system on the BGP path to address.
*
* The ip->AS mapping depends on how asmap is constructed.
*/
uint32_t GetMappedAS(const CNetAddr& address) const;
private:
/** Compressed IP->ASN mapping, loaded from a file when a node starts.
*
* This mapping is then used for bucketing nodes in Addrman and for
* ensuring we connect to a diverse set of peers in Connman. The map is
* empty if no file was provided.
*
* If asmap is provided, nodes will be bucketed by AS they belong to, in
* order to make impossible for a node to connect to several nodes hosted
* in a single AS. This is done in response to Erebus attack, but also to
* generally diversify the connections every node creates, especially
* useful when a large fraction of nodes operate under a couple of cloud
* providers.
*
* If a new asmap is provided, the existing addrman records are
* re-bucketed.
*
* This is initialized in the constructor, const, and therefore is
* thread-safe. */
const std::vector<bool> m_asmap;
};
#endif // BITCOIN_NETGROUP_H
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