Merge #11904: Add a lock to the wallet directory

2f3bd47 Abstract directory locking into util.cpp (MeshCollider)
5260a4a Make .walletlock distinct from .lock (MeshCollider)
64226de Generalise walletdir lock error message for correctness (MeshCollider)
c9ed4bd Add a test for wallet directory locking (MeshCollider)
e60cb99 Add a lock to the wallet directory (MeshCollider)

Pull request description:

  Fixes https://github.com/bitcoin/bitcoin/issues/11888, needs a 0.16 milestone

  Also adds a test that the lock works.

  https://github.com/bitcoin/bitcoin/pull/11687 will probably rework this to a per-wallet lock instead of just the walletdir, but this fixes the current issue

Tree-SHA512: 98e52d67f820e3b8f919cf361ffbb7d928f1bd67603e0ed26c5076ea02d9b3a90c3535ddf7329f3b88171396fa28dd3c87adab3577a8a217bd1e4247bda99138

1 files changed, 22 insertions, 0 deletions

diff --git a/src/util.cpp b/src/util.cpp
index 150bc503d..80eed24ff 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -72,6 +72,7 @@
 
 #include <boost/algorithm/string/case_conv.hpp> // for to_lower()
 #include <boost/algorithm/string/predicate.hpp> // for startswith() and endswith()
+#include <boost/interprocess/sync/file_lock.hpp>
 #include <boost/program_options/detail/config_file.hpp>
 #include <boost/thread.hpp>
 #include <openssl/crypto.h>
@@ -375,6 +376,27 @@ int LogPrintStr(const std::string &str)
     return ret;
 }
 
+bool LockDirectory(const fs::path& directory, const std::string lockfile_name, bool probe_only)
+{
+    fs::path pathLockFile = directory / lockfile_name;
+    FILE* file = fsbridge::fopen(pathLockFile, "a"); // empty lock file; created if it doesn't exist.
+    if (file) fclose(file);
+
+    try {
+        static std::map<std::string, boost::interprocess::file_lock> locks;
+        boost::interprocess::file_lock& lock = locks.emplace(pathLockFile.string(), pathLockFile.string().c_str()).first->second;
+        if (!lock.try_lock()) {
+            return false;
+        }
+        if (probe_only) {
+            lock.unlock();
+        }
+    } catch (const boost::interprocess::interprocess_exception& e) {
+        return error("Error while attempting to lock directory %s: %s", directory.string(), e.what());
+    }
+    return true;
+}
+
 /** Interpret string as boolean, for argument parsing */
 static bool InterpretBool(const std::string& strValue)
 {