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test: Make blockencodings_tests deterministic

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refactor: CBlockHeaderAndShortTxIDs constructor now always takes an explicit nonce.
test: Make blockencodings_tests deterministic using fixed seed providing deterministic
CBlockHeaderAndShortTxID nonces and dummy transaction IDs.

Fixes very rare flaky test failures, where the ShortIDs of test transactions collide, leading to
`READ_STATUS_FAILED` from PartiallyDownloadedBlock::InitData and/or `IsTxAvailable` giving `false`
when the transaction should actually be available.

 * Use a new `FastRandomContext` with a fixed seed in each test, to ensure 'random' uint256s
   used as fake prevouts are deterministic, so in-turn test txids and short IDs are deterministic
   and don't collide causing very rare but flaky test failures.
 * Add new test-only/internal initializer for `CBlockHeaderAndShortTxIDs` that takes a specified
   nonce to further ensure determinism and avoid rare but undesireable short ID collisions.
   In a test context this nonce is set to a fixed known-good value. Normally it is random, as
   previously.

Flaky test failures can be reproduced with:

```patch
diff --git a/src/blockencodings.cpp b/src/blockencodings.cpp
index 695e8d806a..64d635a97a 100644
--- a/src/blockencodings.cpp
+++ b/src/blockencodings.cpp
@@ -44,7 +44,8 @@ void CBlockHeaderAndShortTxIDs::FillShortTxIDSelector() const {

 uint64_t CBlockHeaderAndShortTxIDs::GetShortID(const Wtxid& wtxid) const {
     static_assert(SHORTTXIDS_LENGTH == 6, "shorttxids calculation assumes 6-byte shorttxids");
-    return SipHashUint256(shorttxidk0, shorttxidk1, wtxid) & 0xffffffffffffL;
+    // return SipHashUint256(shorttxidk0, shorttxidk1, wtxid) & 0xffffffffffffL;
+    return SipHashUint256(shorttxidk0, shorttxidk1, wtxid) & 0x0f;
 }

```

to increase the likelihood of a short ID collision; and running

```shell
set -e;
n=0;
while (( n++ < 5000 )); do
    src/test/test_bitcoin --run_test=blockencodings_tests;
done
```
This commit is contained in:
AngusP
2024-06-12 22:09:15 +01:00
parent 4c99301220
commit 55eea003af
5 changed files with 38 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

44
src/test/blockencodings_tests.cpp
View File

@@ -27,23 +27,23 @@ static CMutableTransaction BuildTransactionTestCase() {
return tx;
}
static CBlock BuildBlockTestCase() {
static CBlock BuildBlockTestCase(FastRandomContext& ctx) {
CBlock block;
CMutableTransaction tx = BuildTransactionTestCase();
block.vtx.resize(3);
block.vtx[0] = MakeTransactionRef(tx);
block.nVersion = 42;
block.hashPrevBlock = InsecureRand256();
block.hashPrevBlock = ctx.rand256();
block.nBits = 0x207fffff;
tx.vin[0].prevout.hash = Txid::FromUint256(InsecureRand256());
tx.vin[0].prevout.hash = Txid::FromUint256(ctx.rand256());
tx.vin[0].prevout.n = 0;
block.vtx[1] = MakeTransactionRef(tx);
tx.vin.resize(10);
for (size_t i = 0; i < tx.vin.size(); i++) {
tx.vin[i].prevout.hash = Txid::FromUint256(InsecureRand256());
tx.vin[i].prevout.hash = Txid::FromUint256(ctx.rand256());
tx.vin[i].prevout.n = 0;
}
block.vtx[2] = MakeTransactionRef(tx);
@@ -63,7 +63,8 @@ BOOST_AUTO_TEST_CASE(SimpleRoundTripTest)
{
CTxMemPool& pool = *Assert(m_node.mempool);
TestMemPoolEntryHelper entry;
CBlock block(BuildBlockTestCase());
auto rand_ctx(FastRandomContext(uint256{42}));
CBlock block(BuildBlockTestCase(rand_ctx));
LOCK2(cs_main, pool.cs);
pool.addUnchecked(entry.FromTx(block.vtx[2]));
@@ -71,7 +72,7 @@ BOOST_AUTO_TEST_CASE(SimpleRoundTripTest)
// Do a simple ShortTxIDs RT
{
CBlockHeaderAndShortTxIDs shortIDs{block};
CBlockHeaderAndShortTxIDs shortIDs{block, rand_ctx.rand64()};
DataStream stream{};
stream << shortIDs;
@@ -128,8 +129,8 @@ public:
stream << orig;
stream >> *this;
}
explicit TestHeaderAndShortIDs(const CBlock& block) :
TestHeaderAndShortIDs(CBlockHeaderAndShortTxIDs{block}) {}
explicit TestHeaderAndShortIDs(const CBlock& block, FastRandomContext& ctx) :
TestHeaderAndShortIDs(CBlockHeaderAndShortTxIDs{block, ctx.rand64()}) {}
uint64_t GetShortID(const Wtxid& txhash) const {
DataStream stream{};
@@ -146,7 +147,8 @@ BOOST_AUTO_TEST_CASE(NonCoinbasePreforwardRTTest)
{
CTxMemPool& pool = *Assert(m_node.mempool);
TestMemPoolEntryHelper entry;
CBlock block(BuildBlockTestCase());
auto rand_ctx(FastRandomContext(uint256{42}));
CBlock block(BuildBlockTestCase(rand_ctx));
LOCK2(cs_main, pool.cs);
pool.addUnchecked(entry.FromTx(block.vtx[2]));
@@ -156,7 +158,7 @@ BOOST_AUTO_TEST_CASE(NonCoinbasePreforwardRTTest)
// Test with pre-forwarding tx 1, but not coinbase
{
TestHeaderAndShortIDs shortIDs(block);
TestHeaderAndShortIDs shortIDs(block, rand_ctx);
shortIDs.prefilledtxn.resize(1);
shortIDs.prefilledtxn[0] = {1, block.vtx[1]};
shortIDs.shorttxids.resize(2);
@@ -216,7 +218,8 @@ BOOST_AUTO_TEST_CASE(SufficientPreforwardRTTest)
{
CTxMemPool& pool = *Assert(m_node.mempool);
TestMemPoolEntryHelper entry;
CBlock block(BuildBlockTestCase());
auto rand_ctx(FastRandomContext(uint256{42}));
CBlock block(BuildBlockTestCase(rand_ctx));
LOCK2(cs_main, pool.cs);
pool.addUnchecked(entry.FromTx(block.vtx[1]));
@@ -226,7 +229,7 @@ BOOST_AUTO_TEST_CASE(SufficientPreforwardRTTest)
// Test with pre-forwarding coinbase + tx 2 with tx 1 in mempool
{
TestHeaderAndShortIDs shortIDs(block);
TestHeaderAndShortIDs shortIDs(block, rand_ctx);
shortIDs.prefilledtxn.resize(2);
shortIDs.prefilledtxn[0] = {0, block.vtx[0]};
shortIDs.prefilledtxn[1] = {1, block.vtx[2]}; // id == 1 as it is 1 after index 1
@@ -269,10 +272,11 @@ BOOST_AUTO_TEST_CASE(EmptyBlockRoundTripTest)
CMutableTransaction coinbase = BuildTransactionTestCase();
CBlock block;
auto rand_ctx(FastRandomContext(uint256{42}));
block.vtx.resize(1);
block.vtx[0] = MakeTransactionRef(std::move(coinbase));
block.nVersion = 42;
block.hashPrevBlock = InsecureRand256();
block.hashPrevBlock = rand_ctx.rand256();
block.nBits = 0x207fffff;
bool mutated;
@@ -282,7 +286,7 @@ BOOST_AUTO_TEST_CASE(EmptyBlockRoundTripTest)
// Test simple header round-trip with only coinbase
{
CBlockHeaderAndShortTxIDs shortIDs{block};
CBlockHeaderAndShortTxIDs shortIDs{block, rand_ctx.rand64()};
DataStream stream{};
stream << shortIDs;
@@ -306,15 +310,17 @@ BOOST_AUTO_TEST_CASE(EmptyBlockRoundTripTest)
BOOST_AUTO_TEST_CASE(ReceiveWithExtraTransactions) {
CTxMemPool& pool = *Assert(m_node.mempool);
TestMemPoolEntryHelper entry;
const CBlock block(BuildBlockTestCase());
std::vector<CTransactionRef> extra_txn;
extra_txn.resize(10);
auto rand_ctx(FastRandomContext(uint256{42}));
CMutableTransaction mtx = BuildTransactionTestCase();
mtx.vin[0].prevout.hash = Txid::FromUint256(InsecureRand256());
mtx.vin[0].prevout.hash = Txid::FromUint256(rand_ctx.rand256());
mtx.vin[0].prevout.n = 0;
const CTransactionRef non_block_tx = MakeTransactionRef(std::move(mtx));
CBlock block(BuildBlockTestCase(rand_ctx));
std::vector<CTransactionRef> extra_txn;
extra_txn.resize(10);
LOCK2(cs_main, pool.cs);
pool.addUnchecked(entry.FromTx(block.vtx[2]));
BOOST_CHECK_EQUAL(pool.get(block.vtx[2]->GetHash()).use_count(), SHARED_TX_OFFSET + 0);
@@ -326,7 +332,7 @@ BOOST_AUTO_TEST_CASE(ReceiveWithExtraTransactions) {
BOOST_CHECK_EQUAL(pool.get(block.vtx[1]->GetHash()), nullptr);
{
const CBlockHeaderAndShortTxIDs cmpctblock{block};
const CBlockHeaderAndShortTxIDs cmpctblock{block, rand_ctx.rand64()};
PartiallyDownloadedBlock partial_block(&pool);
PartiallyDownloadedBlock partial_block_with_extra(&pool);