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Merge bitcoin/bitcoin#26289: Use util::Result in for calculating mempool ancestors

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47c4b1f52a mempool: log/halt when CalculateMemPoolAncestors fails unexpectedly (stickies-v)
5481f65849 mempool: add AssumeCalculateMemPoolAncestors helper function (stickies-v)
f911bdfff9 mempool: use util::Result for CalculateMemPoolAncestors (stickies-v)
66e028f739 mempool: use util::Result for CalculateAncestorsAndCheckLimits (stickies-v)

Pull request description:

  Upon reviewing the documentation for `CTxMemPool::CalculateMemPoolAncestors`, I noticed `setAncestors` was meant to be an `out` parameter but actually is an `in,out` parameter, as can be observed by adding `assert(setAncestors.empty());` as the first line in the function and running `make check`. This PR fixes this unexpected behaviour and introduces refactoring improvements to make intents and effects of the code more clear.

  ## Unexpected behaviour
  This behaviour occurs only in the package acceptance path, currently only triggered by `testmempoolaccept` and `submitpackage` RPCs.

  In `MemPoolAccept::AcceptMultipleTransactions()`, we first call `PreChecks()` and then `SubmitPackage()` with the same `Workspace ws` reference. `PreChecks` leaves `ws.m_ancestors` in a potentially non-empty state, before it is passed on to `MemPoolAccept::SubmitPackage`. `SubmitPackage` is the only place where `setAncestors` isn't guaranteed to be empty before calling `CalculateMemPoolAncestors`. The most straightforward fix is to just forcefully clear `setAncestors` at the beginning of CalculateMemPoolAncestors, which is done in the first bugfix commit.

  ## Improvements
  ### Return value instead of out-parameters
  This PR updates the function signatures for `CTxMemPool::CalculateMemPoolAncestors` and `CTxMemPool::CalculateAncestorsAndCheckLimits` to use a `util::Result` return type and eliminate both the `setAncestors` `in,out`-parameter as well as the error string. It simplifies the code and makes the intent and effects more explicit.

  ### Observability
  There are 7 instances where we currently call `CalculateMemPoolAncestors` without actually checking if the function succeeded because we assume that it can't fail, such as in [miner.cpp](69b10212ea/src/node/miner.cpp (L399)). This PR adds a new wrapper `AssumeCalculateMemPoolAncestors` function that logs such unexpected failures, or in case of debug builds even halts the program. It's not crucial to the objective, more of an observability improvement that seems sensible to add on here.

ACKs for top commit:
  achow101:
    ACK 47c4b1f52a
  w0xlt:
    ACK 47c4b1f52a
  glozow:
    ACK 47c4b1f52a
  furszy:
    light code review ACK 47c4b1f5
  aureleoules:
    ACK 47c4b1f52a

Tree-SHA512: d908dad00d1a5645eb865c4877cc0bae74b9cd3332a3641eb4a285431aef119f9fc78172d38b55c592168a73dae83242e6af3348815f7b37cbe2d448a3a58648
This commit is contained in:
Andrew Chow
2023-01-03 16:24:21 -05:00
parent f301bf52ab 47c4b1f52a
commit 80fc1af096
8 changed files with 121 additions and 111 deletions
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40
src/validation.cpp
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@@ -64,6 +64,7 @@
#include <numeric>
#include <optional>
#include <string>
#include <utility>
using kernel::CCoinsStats;
using kernel::CoinStatsHashType;
@@ -867,11 +868,9 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
m_limits.descendant_size_vbytes += conflict->GetSizeWithDescendants();
}
std::string errString;
if (!m_pool.CalculateMemPoolAncestors(*entry, ws.m_ancestors, m_limits, errString)) {
ws.m_ancestors.clear();
auto ancestors{m_pool.CalculateMemPoolAncestors(*entry, m_limits)};
if (!ancestors) {
// If CalculateMemPoolAncestors fails second time, we want the original error string.
std::string dummy_err_string;
// Contracting/payment channels CPFP carve-out:
// If the new transaction is relatively small (up to 40k weight)
// and has at most one ancestor (ie ancestor limit of 2, including
@@ -889,14 +888,16 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
.descendant_count = m_limits.descendant_count + 1,
.descendant_size_vbytes = m_limits.descendant_size_vbytes + EXTRA_DESCENDANT_TX_SIZE_LIMIT,
};
if (ws.m_vsize > EXTRA_DESCENDANT_TX_SIZE_LIMIT ||
!m_pool.CalculateMemPoolAncestors(*entry, ws.m_ancestors,
cpfp_carve_out_limits,
dummy_err_string)) {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "too-long-mempool-chain", errString);
const auto error_message{util::ErrorString(ancestors).original};
if (ws.m_vsize > EXTRA_DESCENDANT_TX_SIZE_LIMIT) {
return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "too-long-mempool-chain", error_message);
}
ancestors = m_pool.CalculateMemPoolAncestors(*entry, cpfp_carve_out_limits);
if (!ancestors) return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "too-long-mempool-chain", error_message);
}
ws.m_ancestors = *ancestors;
// A transaction that spends outputs that would be replaced by it is invalid. Now
// that we have the set of all ancestors we can detect this
// pathological case by making sure ws.m_conflicts and ws.m_ancestors don't
@@ -1111,15 +1112,18 @@ bool MemPoolAccept::SubmitPackage(const ATMPArgs& args, std::vector<Workspace>&
// Re-calculate mempool ancestors to call addUnchecked(). They may have changed since the
// last calculation done in PreChecks, since package ancestors have already been submitted.
std::string unused_err_string;
if(!m_pool.CalculateMemPoolAncestors(*ws.m_entry, ws.m_ancestors, m_limits, unused_err_string)) {
results.emplace(ws.m_ptx->GetWitnessHash(), MempoolAcceptResult::Failure(ws.m_state));
// Since PreChecks() and PackageMempoolChecks() both enforce limits, this should never fail.
Assume(false);
all_submitted = false;
package_state.Invalid(PackageValidationResult::PCKG_MEMPOOL_ERROR,
strprintf("BUG! Mempool ancestors or descendants were underestimated: %s",
ws.m_ptx->GetHash().ToString()));
{
auto ancestors{m_pool.CalculateMemPoolAncestors(*ws.m_entry, m_limits)};
if(!ancestors) {
results.emplace(ws.m_ptx->GetWitnessHash(), MempoolAcceptResult::Failure(ws.m_state));
// Since PreChecks() and PackageMempoolChecks() both enforce limits, this should never fail.
Assume(false);
all_submitted = false;
package_state.Invalid(PackageValidationResult::PCKG_MEMPOOL_ERROR,
strprintf("BUG! Mempool ancestors or descendants were underestimated: %s",
ws.m_ptx->GetHash().ToString()));
}
ws.m_ancestors = std::move(ancestors).value_or(ws.m_ancestors);
}
// If we call LimitMempoolSize() for each individual Finalize(), the mempool will not take
// the transaction's descendant feerate into account because it hasn't seen them yet. Also,