Merge bitcoin/bitcoin#25574: validation: Improve error handling when VerifyDB dosn't finish successfully

0af16e7134459e0820ab95d751093876c1ec4c6d doc: add release note for #25574 (Martin Zumsande)
57ef2a4812f443b2d734f43cebf3ef5038da83f2 validation: report if pruning prevents completion of verification (Martin Zumsande)
0c7785bb2540b69564104767d38342704230cbc2 init, validation: Improve handling if VerifyDB() fails due to insufficient dbcache (Martin Zumsande)
d6f781f1cfcbc2c2ad5ee289a0642ed00386d013 validation: return VerifyDBResult::INTERRUPTED if verification was interrupted (Martin Zumsande)
6360b5302d2675788de5c4a28ea77d823f6d809e validation: Change return value of VerifyDB to enum type (Martin Zumsande)

Pull request description:

  `VerifyDB()` can fail to complete due to insufficient dbcache at the level 3 checks. This PR improves the error handling in this case in the following ways:
  - The rpc `-verifychain` now returns false if the check can't be completed due to insufficient cache
  - During init, we only log a warning if the default values for `-checkblocks` and `-checklevel` are taken and the check doesn't complete. However, if the user actively specifies one of these args, we return with an InitError if we can't complete the check.

  This PR also changes `-verifychain` RPC to return `false` if the verification didn't finish due to missing block data (pruning) or due to being interrupted by the node being shutdown.

  Previously, this PR also included a fix for a possible assert during verification - this was done in #27009 (now merged).

ACKs for top commit:
  achow101:
    ACK 0af16e7134459e0820ab95d751093876c1ec4c6d
  ryanofsky:
    Code review ACK 0af16e7134459e0820ab95d751093876c1ec4c6d. Only small suggested changes since the last review, like renaming some of the enum values. I did leave more suggestions, but they are not very important and could be followups
  john-moffett:
    ACK 0af16e7134459e0820ab95d751093876c1ec4c6d
  MarcoFalke:
    lgtm re-ACK 0af16e7134459e0820ab95d751093876c1ec4c6d 🎚

Tree-SHA512: 84b4f767cf9bfbafef362312757c9bf765b41ae3977f4ece840e40c52a2266b1457832df0cdf70440be0aac2168d9b58fc817238630b0b6812f3836ca950bc0e

1 files changed, 32 insertions, 15 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index c839647b29..1357de3c01 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -4060,7 +4060,7 @@ CVerifyDB::~CVerifyDB()
     uiInterface.ShowProgress("", 100, false);
 }
 
-bool CVerifyDB::VerifyDB(
+VerifyDBResult CVerifyDB::VerifyDB(
     Chainstate& chainstate,
     const Consensus::Params& consensus_params,
     CCoinsView& coinsview,
@@ -4069,7 +4069,7 @@ bool CVerifyDB::VerifyDB(
     AssertLockHeld(cs_main);
 
     if (chainstate.m_chain.Tip() == nullptr || chainstate.m_chain.Tip()->pprev == nullptr) {
-        return true;
+        return VerifyDBResult::SUCCESS;
     }
 
     // Verify blocks in the best chain
@@ -4084,6 +4084,7 @@ bool CVerifyDB::VerifyDB(
     int nGoodTransactions = 0;
     BlockValidationState state;
     int reportDone = 0;
+    bool skipped_no_block_data{false};
     bool skipped_l3_checks{false};
     LogPrintf("Verification progress: 0%%\n");
 
@@ -4103,25 +4104,29 @@ bool CVerifyDB::VerifyDB(
         if ((chainstate.m_blockman.IsPruneMode() || is_snapshot_cs) && !(pindex->nStatus & BLOCK_HAVE_DATA)) {
             // If pruning or running under an assumeutxo snapshot, only go
             // back as far as we have data.
-            LogPrintf("VerifyDB(): block verification stopping at height %d (pruning, no data)\n", pindex->nHeight);
+            LogPrintf("VerifyDB(): block verification stopping at height %d (no data). This could be due to pruning or use of an assumeutxo snapshot.\n", pindex->nHeight);
+            skipped_no_block_data = true;
             break;
         }
         CBlock block;
         // check level 0: read from disk
         if (!ReadBlockFromDisk(block, pindex, consensus_params)) {
-            return error("VerifyDB(): *** ReadBlockFromDisk failed at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
+            LogPrintf("Verification error: ReadBlockFromDisk failed at %d, hash=%s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
+            return VerifyDBResult::CORRUPTED_BLOCK_DB;
         }
         // check level 1: verify block validity
         if (nCheckLevel >= 1 && !CheckBlock(block, state, consensus_params)) {
-            return error("%s: *** found bad block at %d, hash=%s (%s)\n", __func__,
-                         pindex->nHeight, pindex->GetBlockHash().ToString(), state.ToString());
+            LogPrintf("Verification error: found bad block at %d, hash=%s (%s)\n",
+                      pindex->nHeight, pindex->GetBlockHash().ToString(), state.ToString());
+            return VerifyDBResult::CORRUPTED_BLOCK_DB;
         }
         // check level 2: verify undo validity
         if (nCheckLevel >= 2 && pindex) {
             CBlockUndo undo;
             if (!pindex->GetUndoPos().IsNull()) {
                 if (!UndoReadFromDisk(undo, pindex)) {
-                    return error("VerifyDB(): *** found bad undo data at %d, hash=%s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
+                    LogPrintf("Verification error: found bad undo data at %d, hash=%s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
+                    return VerifyDBResult::CORRUPTED_BLOCK_DB;
                 }
             }
         }
@@ -4133,7 +4138,8 @@ bool CVerifyDB::VerifyDB(
                 assert(coins.GetBestBlock() == pindex->GetBlockHash());
                 DisconnectResult res = chainstate.DisconnectBlock(block, pindex, coins);
                 if (res == DISCONNECT_FAILED) {
-                    return error("VerifyDB(): *** irrecoverable inconsistency in block data at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
+                    LogPrintf("Verification error: irrecoverable inconsistency in block data at %d, hash=%s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
+                    return VerifyDBResult::CORRUPTED_BLOCK_DB;
                 }
                 if (res == DISCONNECT_UNCLEAN) {
                     nGoodTransactions = 0;
@@ -4145,14 +4151,16 @@ bool CVerifyDB::VerifyDB(
                 skipped_l3_checks = true;
             }
         }
-        if (ShutdownRequested()) return true;
+        if (ShutdownRequested()) return VerifyDBResult::INTERRUPTED;
     }
     if (pindexFailure) {
-        return error("VerifyDB(): *** coin database inconsistencies found (last %i blocks, %i good transactions before that)\n", chainstate.m_chain.Height() - pindexFailure->nHeight + 1, nGoodTransactions);
+        LogPrintf("Verification error: coin database inconsistencies found (last %i blocks, %i good transactions before that)\n", chainstate.m_chain.Height() - pindexFailure->nHeight + 1, nGoodTransactions);
+        return VerifyDBResult::CORRUPTED_BLOCK_DB;
     }
     if (skipped_l3_checks) {
         LogPrintf("Skipped verification of level >=3 (insufficient database cache size). Consider increasing -dbcache.\n");
     }
+
     // store block count as we move pindex at check level >= 4
     int block_count = chainstate.m_chain.Height() - pindex->nHeight;
 
@@ -4168,18 +4176,27 @@ bool CVerifyDB::VerifyDB(
             uiInterface.ShowProgress(_("Verifying blocks…").translated, percentageDone, false);
             pindex = chainstate.m_chain.Next(pindex);
             CBlock block;
-            if (!ReadBlockFromDisk(block, pindex, consensus_params))
-                return error("VerifyDB(): *** ReadBlockFromDisk failed at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
+            if (!ReadBlockFromDisk(block, pindex, consensus_params)) {
+                LogPrintf("Verification error: ReadBlockFromDisk failed at %d, hash=%s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
+                return VerifyDBResult::CORRUPTED_BLOCK_DB;
+            }
             if (!chainstate.ConnectBlock(block, state, pindex, coins)) {
-                return error("VerifyDB(): *** found unconnectable block at %d, hash=%s (%s)", pindex->nHeight, pindex->GetBlockHash().ToString(), state.ToString());
+                LogPrintf("Verification error: found unconnectable block at %d, hash=%s (%s)\n", pindex->nHeight, pindex->GetBlockHash().ToString(), state.ToString());
+                return VerifyDBResult::CORRUPTED_BLOCK_DB;
             }
-            if (ShutdownRequested()) return true;
+            if (ShutdownRequested()) return VerifyDBResult::INTERRUPTED;
         }
     }
 
     LogPrintf("Verification: No coin database inconsistencies in last %i blocks (%i transactions)\n", block_count, nGoodTransactions);
 
-    return true;
+    if (skipped_l3_checks) {
+        return VerifyDBResult::SKIPPED_L3_CHECKS;
+    }
+    if (skipped_no_block_data) {
+        return VerifyDBResult::SKIPPED_MISSING_BLOCKS;
+    }
+    return VerifyDBResult::SUCCESS;
 }
 
 /** Apply the effects of a block on the utxo cache, ignoring that it may already have been applied. */