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

de8f9123af test: cover read-only blockstore (Matthew Zipkin)
5c2185b3b6 ci: enable chattr +i capability inside containers (Matthew Zipkin)
e573f24202 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 de8f9123af 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 de8f9123af
  MarcoFalke:
    lgtm ACK de8f9123af 📶

Tree-SHA512: b9bd684035dcea11c901b649fc39f397a2155a9a8459f3348e67947e387e45312fddeccb52981aef486f8a31deebb5356a7901c1bb94b78f82c24192a369af73

test/functional/feature_reindex_readonly.py

@@ -0,0 +1,64 @@
+#!/usr/bin/env python3
+# Copyright (c) 2023-present The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test running bitcoind with -reindex from a read-only blockstore
+- Start a node, generate blocks, then restart with -reindex after setting blk files to read-only
+"""
+
+import platform
+import stat
+import subprocess
+from test_framework.test_framework import BitcoinTestFramework
+
+
+class BlockstoreReindexTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.setup_clean_chain = True
+        self.num_nodes = 1
+        self.extra_args = [["-fastprune"]]
+
+    def reindex_readonly(self):
+        self.log.debug("Generate block big enough to start second block file")
+        fastprune_blockfile_size = 0x10000
+        opreturn = "6a"
+        nulldata = fastprune_blockfile_size * "ff"
+        self.generateblock(self.nodes[0], output=f"raw({opreturn}{nulldata})", transactions=[])
+        self.stop_node(0)
+
+        assert (self.nodes[0].chain_path / "blocks" / "blk00000.dat").exists()
+        assert (self.nodes[0].chain_path / "blocks" / "blk00001.dat").exists()
+
+        self.log.debug("Make the first block file read-only")
+        filename = self.nodes[0].chain_path / "blocks" / "blk00000.dat"
+        filename.chmod(stat.S_IREAD)
+
+        used_chattr = False
+        if platform.system() == "Linux":
+            try:
+                subprocess.run(['chattr', '+i', filename], capture_output=True, check=True)
+                used_chattr = True
+                self.log.info("Made file immutable with chattr")
+            except subprocess.CalledProcessError as e:
+                self.log.warning(str(e))
+                if e.stdout:
+                    self.log.warning(f"stdout: {e.stdout}")
+                if e.stderr:
+                    self.log.warning(f"stderr: {e.stderr}")
+
+        self.log.debug("Attempt to restart and reindex the node with the unwritable block file")
+        with self.nodes[0].assert_debug_log(expected_msgs=['FlushStateToDisk', 'failed to open file'], unexpected_msgs=[]):
+            self.nodes[0].assert_start_raises_init_error(extra_args=['-reindex', '-fastprune'],
+                expected_msg="Error: A fatal internal error occurred, see debug.log for details")
+
+        if used_chattr:
+            subprocess.check_call(['chattr', '-i', filename])
+
+        filename.chmod(0o777)
+
+    def run_test(self):
+        self.reindex_readonly()
+
+
+if __name__ == '__main__':
+    BlockstoreReindexTest().main()

test/functional/test_runner.py

@@ -162,6 +162,7 @@ BASE_SCRIPTS = [
     'wallet_abandonconflict.py --legacy-wallet',
     'wallet_abandonconflict.py --descriptors',
     'feature_reindex.py',
+    'feature_reindex_readonly.py',
     'wallet_labels.py --legacy-wallet',
     'wallet_labels.py --descriptors',
     'p2p_compactblocks.py',