dash/src/checkpoints.h
Alexander Block ccee103a0e Backport "assumed valid blocks" feature from Bitcoin 0.13 (#1582)
* IBD check uses minimumchain work instead of checkpoints.

This introduces a 'minimum chain work' chainparam which is intended
 to be the known amount of work in the chain for the network at the
 time of software release.  If you don't have this much work, you're
 not yet caught up.

This is used instead of the count of blocks test from checkpoints.

This criteria is trivial to keep updated as there is no element of
subjectivity, trust, or position dependence to it. It is also a more
reliable metric of sync status than a block count.

* Remove GetTotalBlocksEstimate and checkpoint tests that test nothing.

GetTotalBlocksEstimate is no longer used and it was the only thing
 the checkpoint tests were testing.

Since checkpoints are on their way out it makes more sense to remove
 the test file than to cook up a new pointless test.

# Conflicts:
#	src/Makefile.test.include
#	src/test/Checkpoints_tests.cpp

* IsInitialBlockDownload no longer uses header-only timestamps.

This avoids a corner case (mostly visible on testnet) where bogus
 headers can keep nodes in IsInitialBlockDownload.

* Delay parallel block download until chain has sufficient work

nMinimumChainWork is an anti-DoS threshold; wait until we have a proposed
tip with more work than that before downloading blocks towards that tip.

* Add timeout for headers sync

At startup, we choose one peer to serve us the headers chain, until
our best header is close to caught up.  Disconnect this peer if more
than 15 minutes + 1ms/expected_header passes and our best header
is still more than 1 day away from current time.

* Introduce assumevalid setting to skip presumed valid scripts.

This disentangles the script validation skipping from checkpoints.

A new option is introduced "assumevalid" which specifies a block whos
 ancestors we assume all have valid scriptsigs and so we do not check
 them when they are also burried under the best header by two weeks
 worth of work.

Unlike checkpoints this has no influence on consensus unless you set
 it to a block with an invalid history.  Because of this it can be
 easily be updated without risk of influencing the network consensus.

This results in a massive IBD speedup.

This approach was independently recommended by Peter Todd and Luke-Jr
 since POW based signature skipping (see PR#9180) does not have the
 verifiable properties of a specific hash and may create bad incentives.

The downside is that, like checkpoints, the defaults bitrot and older
 releases will sync slower.  On the plus side users can provide their
 own value here, and if they set it to something crazy all that will
 happen is more time will be spend validating signatures.

Checkblocks and checklevel are also moved to the hidden debug options:
 Especially now that checkblocks has a low default there is little need
 to change these settings, and users frequently misunderstand them as
 influencing security or IBD speed.  By hiding them we offset the
 space added by this new option.

* Add consensusParams to FindNextBlocksToDownload

* Adjust check in headers timeout logic to align with 144 blocks in Dash
2017-08-23 17:21:08 +03:00

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// Copyright (c) 2009-2015 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_CHECKPOINTS_H
#define BITCOIN_CHECKPOINTS_H
#include "uint256.h"
#include <map>
class CBlockIndex;
struct CCheckpointData;
/**
* Block-chain checkpoints are compiled-in sanity checks.
* They are updated every release or three.
*/
namespace Checkpoints
{
//! Returns last CBlockIndex* in mapBlockIndex that is a checkpoint
CBlockIndex* GetLastCheckpoint(const CCheckpointData& data);
double GuessVerificationProgress(const CCheckpointData& data, CBlockIndex* pindex, bool fSigchecks = true);
} //namespace Checkpoints
#endif // BITCOIN_CHECKPOINTS_H