From a238a8dfe621206624abafea1ce66297d79427df Mon Sep 17 00:00:00 2001
From: MeshCollider <dobsonsa68@gmail.com>
Date: Fri, 15 Dec 2017 11:06:22 +1300
Subject: [PATCH] Add a lock to the wallet directory

---
 src/wallet/db.cpp | 66 +++++++++++++++++++++++++++++++++--------------
 src/wallet/db.h   |  2 +-
 2 files changed, 47 insertions(+), 21 deletions(-)

diff --git a/src/wallet/db.cpp b/src/wallet/db.cpp
index f0bc8e512396a..04d4c54364736 100644
--- a/src/wallet/db.cpp
+++ b/src/wallet/db.cpp
@@ -20,6 +20,7 @@
 #include <sys/stat.h>
 #endif
 
+#include <boost/interprocess/sync/file_lock.hpp>
 #include <boost/thread.hpp>
 
 
@@ -55,6 +56,24 @@ void CheckUniqueFileid(const CDBEnv& env, const std::string& filename, Db& db)
         }
     }
 }
+
+bool LockEnvDirectory(const fs::path& env_path)
+{
+    // Make sure only a single PIVX process is using the wallet directory.
+    fs::path lock_file_path = env_path / ".lock";
+    FILE* file = fsbridge::fopen(lock_file_path, "a"); // empty lock file; created if it doesn't exist.
+    if (file) fclose(file);
+
+    try {
+        static boost::interprocess::file_lock lock(lock_file_path.string().c_str());
+        if (!lock.try_lock()) {
+            return false;
+        }
+    } catch (const boost::interprocess::interprocess_exception& e) {
+        return error("Error obtaining lock on wallet directory %s: %s.", env_path.string(), e.what());
+    }
+    return true;
+}
 } // namespace
 
 //
@@ -98,13 +117,17 @@ void CDBEnv::Close()
     EnvShutdown();
 }
 
-bool CDBEnv::Open(const fs::path& pathIn)
+bool CDBEnv::Open(const fs::path& pathIn, bool retry)
 {
     if (fDbEnvInit)
         return true;
 
     boost::this_thread::interruption_point();
 
+    if (!LockEnvDirectory(pathIn)) {
+        return false;
+    }
+
     strPath = pathIn.string();
     fs::path pathLogDir = pathIn / "database";
     TryCreateDirectories(pathLogDir);
@@ -137,7 +160,24 @@ bool CDBEnv::Open(const fs::path& pathIn)
         S_IRUSR | S_IWUSR);
     if (ret != 0) {
         dbenv->close(0);
-        return error("CDBEnv::Open : Error %d opening database environment: %s\n", ret, DbEnv::strerror(ret));
+        LogPrintf("CDBEnv::Open: Error %d opening database environment: %s\n", ret, DbEnv::strerror(ret));
+        if (retry) {
+            // try moving the database env out of the way
+            fs::path pathDatabaseBak = pathIn / strprintf("database.%d.bak", GetTime());
+            try {
+                fs::rename(pathLogDir, pathDatabaseBak);
+                LogPrintf("Moved old %s to %s. Retrying.\n", pathLogDir.string(), pathDatabaseBak.string());
+            } catch (const fs::filesystem_error&) {
+                // failure is ok (well, not really, but it's not worse than what we started with)
+            }
+            // try opening it again one more time
+            if (!Open(pathIn, false)) {
+                // if it still fails, it probably means we can't even create the database env
+                return false;
+            }
+        } else {
+            return false;
+        }
     }
 
     fDbEnvInit = true;
@@ -266,25 +306,11 @@ bool CDB::VerifyEnvironment(const std::string& walletFile, const fs::path& walle
     if (walletFile != wallet_file_path.filename().string())
         return UIError(strprintf(_("Wallet %s resides outside data directory %s"), walletFile, walletDir.string()));
 
-    if (!bitdb.Open(walletDir))
-    {
-        // try moving the database env out of the way
-        fs::path pathDatabase = walletDir / "database";
-        fs::path pathDatabaseBak = walletDir / strprintf("database.%d.bak", GetTime());
-        try {
-            fs::rename(pathDatabase, pathDatabaseBak);
-            LogPrintf("Moved old %s to %s. Retrying.\n", pathDatabase.string(), pathDatabaseBak.string());
-        } catch (const fs::filesystem_error&) {
-            // failure is ok (well, not really, but it's not worse than what we started with)
-        }
-
-        // try again
-        if (!bitdb.Open(walletDir)) {
-            // if it still fails, it probably means we can't even create the database env
-            errorStr = strprintf(_("Error initializing wallet database environment %s!"), walletDir);
-            return false;
-        }
+    if (!bitdb.Open(walletDir, true)) {
+        errorStr = strprintf(_("Cannot obtain a lock on wallet directory %s. Another instance of bitcoin may be using it."), walletDir);
+        return false;
     }
+
     return true;
 }
 
diff --git a/src/wallet/db.h b/src/wallet/db.h
index 168f6522f986f..5254f1c41d6e7 100644
--- a/src/wallet/db.h
+++ b/src/wallet/db.h
@@ -70,7 +70,7 @@ class CDBEnv
     typedef std::pair<std::vector<unsigned char>, std::vector<unsigned char> > KeyValPair;
     bool Salvage(const std::string& strFile, bool fAggressive, std::vector<KeyValPair>& vResult);
 
-    bool Open(const fs::path& path);
+    bool Open(const fs::path& path, bool retry = 0);
     void Close();
     void Flush(bool fShutdown);
     void CheckpointLSN(const std::string& strFile);