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39 lines
1.9 KiB
39 lines
1.9 KiB
9 years ago
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// Copyright (c) 2014 The btcsuite developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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/*
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Package addrmgr implements concurrency safe Bitcoin address manager.
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Address Manager Overview
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In order maintain the peer-to-peer Bitcoin network, there needs to be a source
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of addresses to connect to as nodes come and go. The Bitcoin protocol provides
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a the getaddr and addr messages to allow peers to communicate known addresses
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with each other. However, there needs to a mechanism to store those results and
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select peers from them. It is also important to note that remote peers can't
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be trusted to send valid peers nor attempt to provide you with only peers they
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control with malicious intent.
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With that in mind, this package provides a concurrency safe address manager for
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caching and selecting peers in a non-determinstic manner. The general idea is
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the caller adds addresses to the address manager and notifies it when addresses
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are connected, known good, and attempted. The caller also requests addresses as
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it needs them.
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The address manager internally segregates the addresses into groups and
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non-deterministically selects groups in a cryptographically random manner. This
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reduce the chances multiple addresses from the same nets are selected which
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generally helps provide greater peer diversity, and perhaps more importantly,
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drastically reduces the chances an attacker is able to coerce your peer into
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only connecting to nodes they control.
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The address manager also understands routability and tor addresses and tries
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hard to only return routable addresses. In addition, it uses the information
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provided by the caller about connected, known good, and attempted addresses to
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periodically purge peers which no longer appear to be good peers as well as
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bias the selection toward known good peers. The general idea is to make a best
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effort at only providing usuable addresses.
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*/
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package addrmgr
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