1 files changed, 66 insertions, 0 deletions
diff --git a/src/netgroup.h b/src/netgroup.h
new file mode 100644
index 0000000000..2dd63ec66b
--- /dev/null
+++ b/src/netgroup.h
@@ -0,0 +1,66 @@
+// 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 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