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Reduce checkpoints' effect on consensus.

Instead of only checking height to decide whether to disable script checks,
actually check whether a block is an ancestor of a checkpoint, up to which
headers have been validated. This means that we don't have to prevent
accepting a side branch anymore - it will be safe, just less fast to
do.

We still need to prevent being fed a multitude of low-difficulty headers
filling up our memory. The mechanism for that is unchanged for now: once
a checkpoint is reached with headers, no headers chain branching off before
that point are allowed anymore.
tags/v0.15.1
Pieter Wuille 6 years ago
parent
commit
dce8360e44
6 changed files with 15 additions and 38 deletions
  1. 4
    3
      src/chain.cpp
  2. 0
    9
      src/checkpoints.cpp
  3. 0
    3
      src/checkpoints.h
  4. 1
    1
      src/init.cpp
  5. 9
    7
      src/main.cpp
  6. 1
    15
      src/test/Checkpoints_tests.cpp

+ 4
- 3
src/chain.cpp View File

@@ -82,9 +82,10 @@ CBlockIndex* CBlockIndex::GetAncestor(int height)
while (heightWalk > height) {
int heightSkip = GetSkipHeight(heightWalk);
int heightSkipPrev = GetSkipHeight(heightWalk - 1);
if (heightSkip == height ||
(heightSkip > height && !(heightSkipPrev < heightSkip - 2 &&
heightSkipPrev >= height))) {
if (pindexWalk->pskip != NULL &&
(heightSkip == height ||
(heightSkip > height && !(heightSkipPrev < heightSkip - 2 &&
heightSkipPrev >= height)))) {
// Only follow pskip if pprev->pskip isn't better than pskip->pprev.
pindexWalk = pindexWalk->pskip;
heightWalk = heightSkip;

+ 0
- 9
src/checkpoints.cpp View File

@@ -24,15 +24,6 @@ namespace Checkpoints {
*/
static const double SIGCHECK_VERIFICATION_FACTOR = 5.0;

bool CheckBlock(const CCheckpointData& data, int nHeight, const uint256& hash)
{
const MapCheckpoints& checkpoints = data.mapCheckpoints;

MapCheckpoints::const_iterator i = checkpoints.find(nHeight);
if (i == checkpoints.end()) return true;
return hash == i->second;
}

//! Guess how far we are in the verification process at the given block index
double GuessVerificationProgress(const CCheckpointData& data, CBlockIndex *pindex, bool fSigchecks) {
if (pindex==NULL)

+ 0
- 3
src/checkpoints.h View File

@@ -26,9 +26,6 @@ struct CCheckpointData {
double fTransactionsPerDay;
};

//! Returns true if block passes checkpoint checks
bool CheckBlock(const CCheckpointData& data, int nHeight, const uint256& hash);

//! Return conservative estimate of total number of blocks, 0 if unknown
int GetTotalBlocksEstimate(const CCheckpointData& data);


+ 1
- 1
src/init.cpp View File

@@ -347,7 +347,7 @@ std::string HelpMessage(HelpMessageMode mode)
strUsage += HelpMessageGroup(_("Debugging/Testing options:"));
if (GetBoolArg("-help-debug", false))
{
strUsage += HelpMessageOpt("-checkpoints", strprintf(_("Only accept block chain matching built-in checkpoints (default: %u)"), 1));
strUsage += HelpMessageOpt("-checkpoints", strprintf(_("Disable expensive verification for known chain history (default: %u)"), 1));
strUsage += HelpMessageOpt("-dblogsize=<n>", strprintf(_("Flush database activity from memory pool to disk log every <n> megabytes (default: %u)"), 100));
strUsage += HelpMessageOpt("-disablesafemode", strprintf(_("Disable safemode, override a real safe mode event (default: %u)"), 0));
strUsage += HelpMessageOpt("-testsafemode", strprintf(_("Force safe mode (default: %u)"), 0));

+ 9
- 7
src/main.cpp View File

@@ -1714,7 +1714,14 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
return true;
}

bool fScriptChecks = (!fCheckpointsEnabled || pindex->nHeight >= Checkpoints::GetTotalBlocksEstimate(chainparams.Checkpoints()));
bool fScriptChecks = true;
if (fCheckpointsEnabled) {
CBlockIndex *pindexLastCheckpoint = Checkpoints::GetLastCheckpoint(chainparams.Checkpoints());
if (pindexLastCheckpoint && pindexLastCheckpoint->GetAncestor(pindex->nHeight) == pindex) {
// This block is an ancestor of a checkpoint: disable script checks
fScriptChecks = false;
}
}

// Do not allow blocks that contain transactions which 'overwrite' older transactions,
// unless those are already completely spent.
@@ -2630,13 +2637,8 @@ bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationState& sta
return state.Invalid(error("%s: block's timestamp is too early", __func__),
REJECT_INVALID, "time-too-old");

if(fCheckpointsEnabled)
if (fCheckpointsEnabled)
{
// Check that the block chain matches the known block chain up to a checkpoint
if (!Checkpoints::CheckBlock(chainParams.Checkpoints(), nHeight, hash))
return state.DoS(100, error("%s: rejected by checkpoint lock-in at %d", __func__, nHeight),
REJECT_CHECKPOINT, "checkpoint mismatch");

// Don't accept any forks from the main chain prior to last checkpoint
CBlockIndex* pcheckpoint = Checkpoints::GetLastCheckpoint(chainParams.Checkpoints());
if (pcheckpoint && nHeight < pcheckpoint->nHeight)

+ 1
- 15
src/test/Checkpoints_tests.cpp View File

@@ -21,21 +21,7 @@ BOOST_FIXTURE_TEST_SUITE(Checkpoints_tests, BasicTestingSetup)
BOOST_AUTO_TEST_CASE(sanity)
{
const Checkpoints::CCheckpointData& checkpoints = Params(CBaseChainParams::MAIN).Checkpoints();
uint256 p11111 = uint256S("0x0000000069e244f73d78e8fd29ba2fd2ed618bd6fa2ee92559f542fdb26e7c1d");
uint256 p134444 = uint256S("0x00000000000005b12ffd4cd315cd34ffd4a594f430ac814c91184a0d42d2b0fe");
BOOST_CHECK(Checkpoints::CheckBlock(checkpoints, 11111, p11111));
BOOST_CHECK(Checkpoints::CheckBlock(checkpoints, 134444, p134444));

// Wrong hashes at checkpoints should fail:
BOOST_CHECK(!Checkpoints::CheckBlock(checkpoints, 11111, p134444));
BOOST_CHECK(!Checkpoints::CheckBlock(checkpoints, 134444, p11111));

// ... but any hash not at a checkpoint should succeed:
BOOST_CHECK(Checkpoints::CheckBlock(checkpoints, 11111+1, p134444));
BOOST_CHECK(Checkpoints::CheckBlock(checkpoints, 134444+1, p11111));

BOOST_CHECK(Checkpoints::GetTotalBlocksEstimate(checkpoints) >= 134444);
}
}

BOOST_AUTO_TEST_SUITE_END()

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