Implement RemoteFileOpenAbility on Windows. This also implements CORE…

…-1038 improvement

builds/install/misc/firebird.conf.in

@@ -274,6 +274,54 @@
 #
 #FileSystemCacheSize = 30
 
+# ----------------------------
+# Remove protection against opening databases on NFS mounted volumes on
+# Linux/Unix and SMB/CIFS volumes on Windows
+#
+# This also permits creating database shadows on mounted network volumes
+#
+#     ***WARNING*** ***WARNING*** ***WARNING*** ***WARNING***
+#
+# This option removes an important safety feature of Firebird and can
+# cause irrecoverable database corruption. Do not use this option unless
+# you understand the risks and are prepared to accept the loss of the
+# contents of your database.
+# Unless this configuration option is changed from 0 to 1, Firebird can
+# open a database only if the database is stored on a drive physically
+# attached to the local computer - the computer running that copy of
+# Firebird. Requests for connections to databases stored on NFS mounted
+# drives are redirected to a Firebird server running on the computer that
+# "owns" the disk.
+# This restriction prevents two different copies of Firebird from opening
+# the same database without coordinating their activities. Uncoordinated
+# access by multiple copies of Firebird will corrupt a database. On a local
+# system, the system-level file locking prevents uncoordinated access to
+# the database file.
+#
+# NFS does not provide a reliable way to detect multiple users of a file on
+# an NFS mounted disk. If a second copy of Firebird connects to a database on
+# an NFS mounted disk, it will corrupt the database.
+# Under some circumstances, running a Firebird server on the computer that
+# owns NFS mounted volumes is inconvenient or impossible. Applications that
+# use the "embedded" variant of Firebird and never share access to a database
+# can use this option to permit direct access to databases on NFS mounted
+# volumes.
+#
+# The situation for SMB/CIFS is quite similar to NFS with not all configurations
+# providing file locking mechanisms needed for safe operation. Using SuperServer
+# engine with the database on NT file server may be considered relatively safe 
+# as file locking protects the database from being used by the several engines.
+# Network stack can still change order of writes so you may get a corrupted
+# database in case of network errors or power outage.
+#
+# The useful and safe case is working with a shared database marked read-only.
+#
+# DO NOT ENABLE THIS OPTION UNLESS YOU REALLY KNOW WHAT YOU ARE DOING.
+#
+# Type: boolean
+#
+#RemoteFileOpenAbility = 0
+
 # ----------------------------
 # Temporary space management
 #
@@ -716,40 +764,6 @@
 # Settings for Unix/Linux platforms
 # ============================
 
-# ----------------------------
-# Remove protection against opening databases on NFS mounted volumes
-#
-#     ***WARNING*** ***WARNING*** ***WARNING*** ***WARNING***
-#
-# This option removes an important safety feature of Firebird and can
-# cause irrecoverable database corruption. Do not use this option unless
-# you understand the risks and are prepared to accept the loss of the
-# contents of your database.
-# Unless this configuration option is changed from 0 to 1, Firebird can
-# open a database only if the database is stored on a drive physically
-# attached to the local computer - the computer running that copy of
-# Firebird. Requests for connections to databases stored on NFS mounted
-# drives are redirected to a Firebird server running on the computer that
-# "owns" the disk.
-# This restriction prevents two different copies of Firebird from opening
-# the same database without coordinating their activities. Uncoordinated
-# access by multiple copies of Firebird will corrupt a database. On a local
-# system, the system-level file locking prevents uncoordinated access to
-# the database file.
-# NFS does not provide a reliable way to detect multiple users of a file on
-# an NFS mounted disk. If a second copy of Firebird connects to a database on
-# an NFS mounted disk, it will corrupt the database.
-# Under some circumstances, running a Firebird server on the computer that
-# owns NFS mounted volumes is inconvenient or impossible. Applications that
-# use the "embedded" variant of Firebird and never share access to a database
-# can use this option to permit direct access to databases on NFS mounted
-# volumes.
-# DO NOT ENABLE THIS OPTION UNLESS YOU REALLY KNOW WHAT YOU ARE DOING.
-#
-# Type: boolean
-#
-#RemoteFileOpenAbility = 0
-
 # ----------------------------
 # Remove protection against redirecting requests to other servers
 #

src/jrd/isc_file.cpp

@@ -372,7 +372,7 @@ bool ISC_analyze_tcp(tstring& file_name, tstring& node_name)
 	{
 		const ULONG dtype = GetDriveType((node_name + ":\\").c_str());
 		// Is it removable, fixed, cdrom or ramdisk?
-		if (dtype > DRIVE_NO_ROOT_DIR && dtype != DRIVE_REMOTE)
+		if (dtype > DRIVE_NO_ROOT_DIR && (dtype != DRIVE_REMOTE || Config::getRemoteFileOpenAbility()))
 		{
 			// CVC: If we didn't match, clean our garbage or we produce side effects
 			// in the caller.
@@ -900,6 +900,11 @@ void ISC_expand_share(tstring& file_name)
 		return;
 	}
 
+	// If RemoteFileOpenAbility = 1 doesn't expand share
+	if (Config::getRemoteFileOpenAbility()) {
+		return;
+	}
+
 	tstring device(file_name.substr(0, 1));
 	const USHORT dtype = GetDriveType((device + ":\\").c_str());
 	if (dtype != DRIVE_REMOTE)