Merge bitcoin/bitcoin#27850: test: Add unit & functional test coverage for blockstore

de8f9123afbecc3b4f59fa80af8148bc865d0588 test: cover read-only blockstore (Matthew Zipkin)
5c2185b3b624ce87320ec16412f98ab591a5860c ci: enable chattr +i capability inside containers (Matthew Zipkin)
e573f2420244c583e218f51cd0d3a3cac6731003 unit test: add coverage for BlockManager (Matthew Zipkin)

Pull request description:

  This PR adds unit and functional tests to cover the behavior described in #2039. In particular, that bitcoind will crash on startup if a reindex is requested but the `blk` files are read-only. Eventually this behavior can be updated with https://github.com/bitcoin/bitcoin/pull/27039. This PR just commits the test coverage from #27039 as suggested in https://github.com/bitcoin/bitcoin/pull/27039#issuecomment-1584915782

ACKs for top commit:
  jonatack:
    ACK de8f9123afbecc3b4f59fa80af8148bc865d0588 modulo suggestions in https://github.com/bitcoin/bitcoin/pull/27850#discussion_r1319010039, tested on macOS, but not on Linux for the Linux-related change in the last push
  achow101:
    ACK de8f9123afbecc3b4f59fa80af8148bc865d0588
  MarcoFalke:
    lgtm ACK de8f9123afbecc3b4f59fa80af8148bc865d0588 📶

Tree-SHA512: b9bd684035dcea11c901b649fc39f397a2155a9a8459f3348e67947e387e45312fddeccb52981aef486f8a31deebb5356a7901c1bb94b78f82c24192a369af73

1 files changed, 71 insertions, 0 deletions

diff --git a/src/test/blockmanager_tests.cpp b/src/test/blockmanager_tests.cpp
index 13cb1cc314..636f5b9388 100644
--- a/src/test/blockmanager_tests.cpp
+++ b/src/test/blockmanager_tests.cpp
@@ -8,10 +8,12 @@
 #include <node/context.h>
 #include <node/kernel_notifications.h>
 #include <script/solver.h>
+#include <primitives/block.h>
 #include <util/chaintype.h>
 #include <validation.h>
 
 #include <boost/test/unit_test.hpp>
+#include <test/util/logging.h>
 #include <test/util/setup_common.h>
 
 using node::BLOCK_SERIALIZATION_HEADER_SIZE;
@@ -130,4 +132,73 @@ BOOST_FIXTURE_TEST_CASE(blockmanager_block_data_availability, TestChain100Setup)
     BOOST_CHECK(!blockman.CheckBlockDataAvailability(tip, *last_pruned_block));
 }
 
+BOOST_AUTO_TEST_CASE(blockmanager_flush_block_file)
+{
+    KernelNotifications notifications{m_node.exit_status};
+    node::BlockManager::Options blockman_opts{
+        .chainparams = Params(),
+        .blocks_dir = m_args.GetBlocksDirPath(),
+        .notifications = notifications,
+    };
+    BlockManager blockman{m_node.kernel->interrupt, blockman_opts};
+
+    // Test blocks with no transactions, not even a coinbase
+    CBlock block1;
+    block1.nVersion = 1;
+    CBlock block2;
+    block2.nVersion = 2;
+    CBlock block3;
+    block3.nVersion = 3;
+
+    // They are 80 bytes header + 1 byte 0x00 for vtx length
+    constexpr int TEST_BLOCK_SIZE{81};
+
+    // Blockstore is empty
+    BOOST_CHECK_EQUAL(blockman.CalculateCurrentUsage(), 0);
+
+    // Write the first block; dbp=nullptr means this block doesn't already have a disk
+    // location, so allocate a free location and write it there.
+    FlatFilePos pos1{blockman.SaveBlockToDisk(block1, /*nHeight=*/1, /*dbp=*/nullptr)};
+
+    // Write second block
+    FlatFilePos pos2{blockman.SaveBlockToDisk(block2, /*nHeight=*/2, /*dbp=*/nullptr)};
+
+    // Two blocks in the file
+    BOOST_CHECK_EQUAL(blockman.CalculateCurrentUsage(), (TEST_BLOCK_SIZE + BLOCK_SERIALIZATION_HEADER_SIZE) * 2);
+
+    // First two blocks are written as expected
+    // Errors are expected because block data is junk, thrown AFTER successful read
+    CBlock read_block;
+    BOOST_CHECK_EQUAL(read_block.nVersion, 0);
+    {
+        ASSERT_DEBUG_LOG("ReadBlockFromDisk: Errors in block header");
+        BOOST_CHECK(!blockman.ReadBlockFromDisk(read_block, pos1));
+        BOOST_CHECK_EQUAL(read_block.nVersion, 1);
+    }
+    {
+        ASSERT_DEBUG_LOG("ReadBlockFromDisk: Errors in block header");
+        BOOST_CHECK(!blockman.ReadBlockFromDisk(read_block, pos2));
+        BOOST_CHECK_EQUAL(read_block.nVersion, 2);
+    }
+
+    // When FlatFilePos* dbp is given, SaveBlockToDisk() will not write or
+    // overwrite anything to the flat file block storage. It will, however,
+    // update the blockfile metadata. This is to facilitate reindexing
+    // when the user has the blocks on disk but the metadata is being rebuilt.
+    // Verify this behavior by attempting (and failing) to write block 3 data
+    // to block 2 location.
+    CBlockFileInfo* block_data = blockman.GetBlockFileInfo(0);
+    BOOST_CHECK_EQUAL(block_data->nBlocks, 2);
+    BOOST_CHECK(blockman.SaveBlockToDisk(block3, /*nHeight=*/3, /*dbp=*/&pos2) == pos2);
+    // Metadata is updated...
+    BOOST_CHECK_EQUAL(block_data->nBlocks, 3);
+    // ...but there are still only two blocks in the file
+    BOOST_CHECK_EQUAL(blockman.CalculateCurrentUsage(), (TEST_BLOCK_SIZE + BLOCK_SERIALIZATION_HEADER_SIZE) * 2);
+
+    // Block 2 was not overwritten:
+    //   SaveBlockToDisk() did not call WriteBlockToDisk() because `FlatFilePos* dbp` was non-null
+    blockman.ReadBlockFromDisk(read_block, pos2);
+    BOOST_CHECK_EQUAL(read_block.nVersion, 2);
+}
+
 BOOST_AUTO_TEST_SUITE_END()