From 540c90546f4749130aad611b8a14373e427185c3 Mon Sep 17 00:00:00 2001
From: KarloX2 <15713553+KarloX2@users.noreply.github.com>
Date: Tue, 19 Feb 2019 17:22:11 +0100
Subject: [PATCH] CORE-6004: Add a switch to disable the "TCP Loopback Fast
 Path" option (Windows only)

---
 builds/install/misc/firebird.conf.in |  8 ++++++++
 doc/Firebird_conf.txt                |  1 +
 src/common/config/config.cpp         |  6 ++++++
 src/common/config/config.h           |  4 ++++
 src/remote/inet.cpp                  | 16 +++++++++-------
 5 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/builds/install/misc/firebird.conf.in b/builds/install/misc/firebird.conf.in
index 79ebef7655..556a3a083f 100644
--- a/builds/install/misc/firebird.conf.in
+++ b/builds/install/misc/firebird.conf.in
@@ -768,6 +768,14 @@
 #
 #TcpNoNagle = 1
 
+#
+# Either enables or disables the "TCP Loopback Fast Path" feature (SIO_LOOPBACK_FAST_PATH).
+# Applies to Windows (version 8/2012 or higher) only.
+#
+# Type: Boolean, default 1 (true)
+#
+#TcpLoopbackFastPathOption = 1
+
 #
 # Allows setting of IPV6_V6ONLY socket option. If enabled, IPv6 sockets
 # allow only IPv6 communication and separate sockets must be used for
diff --git a/doc/Firebird_conf.txt b/doc/Firebird_conf.txt
index b54283614d..4d26cb9375 100644
--- a/doc/Firebird_conf.txt
+++ b/doc/Firebird_conf.txt
@@ -124,6 +124,7 @@ Only meaningful for Windows SS on SMP systems.
 OldParameterOrdering       boolean  default false
 TcpRemoteBufferSize        integer  default 8192 (bytes)
 TcpNoNagle                 boolean  default false
+TcpLoopbackFastPathOption  boolean  default true
 IpcMapSize                 integer  default 4096 (bytes)
 DefaultDbCachePages        integer  default SS: 2048. CS: 75
 ConnectionTimeout          integer  default 180 (seconds)
diff --git a/src/common/config/config.cpp b/src/common/config/config.cpp
index 776a519c5f..70e04b92a7 100644
--- a/src/common/config/config.cpp
+++ b/src/common/config/config.cpp
@@ -148,6 +148,7 @@ const Config::ConfigEntry Config::entries[MAX_CONFIG_KEY] =
 	{TYPE_INTEGER,		"CpuAffinityMask",			(ConfigValue) 0},
 	{TYPE_INTEGER,		"TcpRemoteBufferSize",		(ConfigValue) 8192},		// bytes
 	{TYPE_BOOLEAN,		"TcpNoNagle",				(ConfigValue) true},
+	{TYPE_BOOLEAN,		"TcpLoopbackFastPathOption",(ConfigValue) true},
 	{TYPE_INTEGER,		"DefaultDbCachePages",		(ConfigValue) -1},			// pages
 	{TYPE_INTEGER,		"ConnectionTimeout",		(ConfigValue) 180},			// seconds
 	{TYPE_INTEGER,		"DummyPacketInterval",		(ConfigValue) 0},			// seconds
@@ -492,6 +493,11 @@ bool Config::getTcpNoNagle() const
 	return get<bool>(KEY_TCP_NO_NAGLE);
 }
 
+bool Config::getTcpLoopbackFastPathOption() const
+{
+	return get<bool>(KEY_TCP_LOOPBACK_FAST_PATH_OPTION);
+}
+
 bool Config::getIPv6V6Only() const
 {
 	return get<bool>(KEY_IPV6_V6ONLY);
diff --git a/src/common/config/config.h b/src/common/config/config.h
index 2b21714dff..4cb7bbba33 100644
--- a/src/common/config/config.h
+++ b/src/common/config/config.h
@@ -95,6 +95,7 @@ public:
 		KEY_CPU_AFFINITY_MASK,
 		KEY_TCP_REMOTE_BUFFER_SIZE,
 		KEY_TCP_NO_NAGLE,
+		KEY_TCP_LOOPBACK_FAST_PATH_OPTION,
 		KEY_DEFAULT_DB_CACHE_PAGES,
 		KEY_CONNECTION_TIMEOUT,
 		KEY_DUMMY_PACKET_INTERVAL,
@@ -252,6 +253,9 @@ public:
 	// Disable Nagle algorithm
 	bool getTcpNoNagle() const;
 
+	// Enable or disable the TCP Loopback Fast Path option
+	bool getTcpLoopbackFastPathOption() const;
+
 	// Let IPv6 socket accept only IPv6 packets
 	bool getIPv6V6Only() const;
 
diff --git a/src/remote/inet.cpp b/src/remote/inet.cpp
index b9ff2ddb7f..7cc4e52712 100644
--- a/src/remote/inet.cpp
+++ b/src/remote/inet.cpp
@@ -3242,16 +3242,18 @@ static bool setNoNagleOption(rem_port* port)
 bool setFastLoopbackOption(SOCKET s)
 {
 #ifdef WIN_NT
-	int optval = 1;
-	DWORD bytes = 0;
+	if (Config::getDefaultConfig()->getTcpLoopbackFastPathOption())
+	{
+		int optval = 1;
+		DWORD bytes = 0;
 
-	int ret = WSAIoctl(s, SIO_LOOPBACK_FAST_PATH, &optval, sizeof(optval),
-					   NULL, 0, &bytes, 0, 0);
+		int ret = WSAIoctl(s, SIO_LOOPBACK_FAST_PATH, &optval, sizeof(optval),
+			NULL, 0, &bytes, 0, 0);
 
-	return (ret == 0);
-#else
-	return false;
+		return (ret == 0);
+	}
 #endif
+	return false;
 }
 
 void setStopMainThread(FPTR_INT func)