From 2d796faf62095e83f74337c26e7e1a8c3957cf3c Mon Sep 17 00:00:00 2001
From: Chun Kuan Lee <ken2812221@gmail.com>
Date: Tue, 25 Sep 2018 21:56:16 +0800
Subject: [PATCH] wallet: Fix duplicate fileid

---
 src/wallet/db.cpp | 31 +++++++++++++++++++------------
 src/wallet/db.h   |  7 +++++++
 2 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/src/wallet/db.cpp b/src/wallet/db.cpp
index a7bf89c572..25880f3529 100644
--- a/src/wallet/db.cpp
+++ b/src/wallet/db.cpp
@@ -20,6 +20,7 @@
 #include <boost/thread.hpp>
 
 namespace {
+
 //! Make sure database has a unique fileid within the environment. If it
 //! doesn't, throw an error. BDB caches do not work properly when more than one
 //! open database has the same fileid (values written to one database may show
@@ -29,25 +30,19 @@ namespace {
 //! (https://docs.oracle.com/cd/E17275_01/html/programmer_reference/program_copy.html),
 //! so bitcoin should never create different databases with the same fileid, but
 //! this error can be triggered if users manually copy database files.
-void CheckUniqueFileid(const BerkeleyEnvironment& env, const std::string& filename, Db& db)
+void CheckUniqueFileid(const BerkeleyEnvironment& env, const std::string& filename, Db& db, WalletDatabaseFileId& fileid)
 {
     if (env.IsMock()) return;
 
-    u_int8_t fileid[DB_FILE_ID_LEN];
-    int ret = db.get_mpf()->get_fileid(fileid);
+    int ret = db.get_mpf()->get_fileid(fileid.value);
     if (ret != 0) {
         throw std::runtime_error(strprintf("BerkeleyBatch: Can't open database %s (get_fileid failed with %d)", filename, ret));
     }
 
-    for (const auto& item : env.mapDb) {
-        u_int8_t item_fileid[DB_FILE_ID_LEN];
-        if (item.second && item.second->get_mpf()->get_fileid(item_fileid) == 0 &&
-            memcmp(fileid, item_fileid, sizeof(fileid)) == 0) {
-            const char* item_filename = nullptr;
-            item.second->get_dbname(&item_filename, nullptr);
+    for (const auto& item : env.m_fileids) {
+        if (fileid == item.second && &fileid != &item.second) {
             throw std::runtime_error(strprintf("BerkeleyBatch: Can't open database %s (duplicates fileid %s from %s)", filename,
-                HexStr(std::begin(item_fileid), std::end(item_fileid)),
-                item_filename ? item_filename : "(unknown database)"));
+                HexStr(std::begin(item.second.value), std::end(item.second.value)), item.first));
         }
     }
 }
@@ -56,6 +51,11 @@ CCriticalSection cs_db;
 std::map<std::string, BerkeleyEnvironment> g_dbenvs GUARDED_BY(cs_db); //!< Map from directory name to open db environment.
 } // namespace
 
+bool WalletDatabaseFileId::operator==(const WalletDatabaseFileId& rhs) const
+{
+    return memcmp(value, &rhs.value, sizeof(value)) == 0;
+}
+
 BerkeleyEnvironment* GetWalletEnv(const fs::path& wallet_path, std::string& database_filename)
 {
     fs::path env_directory;
@@ -504,7 +504,7 @@ BerkeleyBatch::BerkeleyBatch(BerkeleyDatabase& database, const char* pszMode, bo
             // versions of BDB have an set_lk_exclusive method for this
             // purpose, but the older version we use does not.)
             for (const auto& env : g_dbenvs) {
-                CheckUniqueFileid(env.second, strFilename, *pdb_temp);
+                CheckUniqueFileid(env.second, strFilename, *pdb_temp, this->env->m_fileids[strFilename]);
             }
 
             pdb = pdb_temp.release();
@@ -826,6 +826,13 @@ void BerkeleyDatabase::Flush(bool shutdown)
             LOCK(cs_db);
             g_dbenvs.erase(env->Directory().string());
             env = nullptr;
+        } else {
+            // TODO: To avoid g_dbenvs.erase erasing the environment prematurely after the
+            // first database shutdown when multiple databases are open in the same
+            // environment, should replace raw database `env` pointers with shared or weak
+            // pointers, or else separate the database and environment shutdowns so
+            // environments can be shut down after databases.
+            env->m_fileids.erase(strFile);
         }
     }
 }
diff --git a/src/wallet/db.h b/src/wallet/db.h
index 467ed13b45..68a59607ae 100644
--- a/src/wallet/db.h
+++ b/src/wallet/db.h
@@ -18,6 +18,7 @@
 #include <map>
 #include <memory>
 #include <string>
+#include <unordered_map>
 #include <vector>
 
 #include <db_cxx.h>
@@ -25,6 +26,11 @@
 static const unsigned int DEFAULT_WALLET_DBLOGSIZE = 100;
 static const bool DEFAULT_WALLET_PRIVDB = true;
 
+struct WalletDatabaseFileId {
+    u_int8_t value[DB_FILE_ID_LEN];
+    bool operator==(const WalletDatabaseFileId& rhs) const;
+};
+
 class BerkeleyEnvironment
 {
 private:
@@ -38,6 +44,7 @@ class BerkeleyEnvironment
     std::unique_ptr<DbEnv> dbenv;
     std::map<std::string, int> mapFileUseCount;
     std::map<std::string, Db*> mapDb;
+    std::unordered_map<std::string, WalletDatabaseFileId> m_fileids;
     std::condition_variable_any m_db_in_use;
 
     BerkeleyEnvironment(const fs::path& env_directory);