chore: better config internal structure

adapter/inbound/listen.go

@@ -17,10 +17,18 @@ func SetTfo(open bool) {
 	lc.DisableTFO = !open
 }
 
+func Tfo() bool {
+	return !lc.DisableTFO
+}
+
 func SetMPTCP(open bool) {
 	setMultiPathTCP(&lc.ListenConfig, open)
 }
 
+func MPTCP() bool {
+	return getMultiPathTCP(&lc.ListenConfig)
+}
+
 func ListenContext(ctx context.Context, network, address string) (net.Listener, error) {
 	return lc.Listen(ctx, network, address)
 }

adapter/inbound/mptcp_go120.go

@@ -8,3 +8,7 @@ const multipathTCPAvailable = false
 
 func setMultiPathTCP(listenConfig *net.ListenConfig, open bool) {
 }
+
+func getMultiPathTCP(listenConfig *net.ListenConfig) bool {
+	return false
+}

adapter/inbound/mptcp_go121.go

@@ -9,3 +9,7 @@ const multipathTCPAvailable = true
 func setMultiPathTCP(listenConfig *net.ListenConfig, open bool) {
 	listenConfig.SetMultipathTCP(open)
 }
+
+func getMultiPathTCP(listenConfig *net.ListenConfig) bool {
+	return listenConfig.MultipathTCP()
+}