Track headers presync progress and log it

src/validation.cpp

@@ -3711,6 +3711,29 @@ bool ChainstateManager::ProcessNewBlockHeaders(const std::vector<CBlockHeader>&
     return true;
 }
 
+void ChainstateManager::ReportHeadersPresync(const arith_uint256& work, int64_t height, int64_t timestamp)
+{
+    AssertLockNotHeld(cs_main);
+    const auto& chainstate = ActiveChainstate();
+    {
+        LOCK(cs_main);
+        // Don't report headers presync progress if we already have a post-minchainwork header chain.
+        // This means we lose reporting for potentially legimate, but unlikely, deep reorgs, but
+        // prevent attackers that spam low-work headers from filling our logs.
+        if (m_best_header->nChainWork >= UintToArith256(GetConsensus().nMinimumChainWork)) return;
+        // Rate limit headers presync updates to 4 per second, as these are not subject to DoS
+        // protection.
+        auto now = std::chrono::steady_clock::now();
+        if (now < m_last_presync_update + std::chrono::milliseconds{250}) return;
+        m_last_presync_update = now;
+    }
+    if (chainstate.IsInitialBlockDownload()) {
+        const int64_t blocks_left{(GetTime() - timestamp) / GetConsensus().nPowTargetSpacing};
+        const double progress{100.0 * height / (height + blocks_left)};
+        LogPrintf("Pre-synchronizing blockheaders, height: %d (~%.2f%%)\n", height, progress);
+    }
+}
+
 /** Store block on disk. If dbp is non-nullptr, the file is known to already reside on disk */
 bool CChainState::AcceptBlock(const std::shared_ptr<const CBlock>& pblock, BlockValidationState& state, CBlockIndex** ppindex, bool fRequested, const FlatFilePos* dbp, bool* fNewBlock, bool min_pow_checked)
 {