From c7e8c9f964034f0ef98358c4206892a1799e1d8c Mon Sep 17 00:00:00 2001
From: "Johan T. Halseth" <johanth@gmail.com>
Date: Fri, 3 Jan 2020 14:01:32 +0100
Subject: [PATCH] loopd: make RPC listener configurable

Allows to use external listener, such as in-memory.
---
 cmd/loopd/main.go |  3 ++-
 loopd/daemon.go   | 34 ++++++++++++++++++++++------------
 loopd/start.go    | 30 ++++++++++++++++++++++++++----
 3 files changed, 50 insertions(+), 17 deletions(-)

diff --git a/cmd/loopd/main.go b/cmd/loopd/main.go
index dac8935..0310198 100644
--- a/cmd/loopd/main.go
+++ b/cmd/loopd/main.go
@@ -7,7 +7,8 @@ import (
 )
 
 func main() {
-	err := loopd.Start()
+	cfg := loopd.RPCConfig{}
+	err := loopd.Start(cfg)
 	if err != nil {
 		fmt.Println(err)
 	}
diff --git a/loopd/daemon.go b/loopd/daemon.go
index f567c57..2695482 100644
--- a/loopd/daemon.go
+++ b/loopd/daemon.go
@@ -104,23 +104,30 @@ func daemon(config *config, lisCfg *listenerCfg) error {
 		return err
 	}
 
-	log.Infof("Starting REST proxy listener")
 	restListener, err := lisCfg.restListener()
 	if err != nil {
 		return fmt.Errorf("REST proxy unable to listen on %s",
 			config.RESTListen)
 	}
-	defer restListener.Close()
-	proxy := &http.Server{Handler: mux}
 
-	go func() {
-		err := proxy.Serve(restListener)
-		// ErrServerClosed is always returned when the proxy is shut
-		// down, so don't log it.
-		if err != nil && err != http.ErrServerClosed {
-			log.Error(err)
-		}
-	}()
+	// A nil listener indicates REST is disabled.
+	if restListener != nil {
+		log.Infof("Starting REST proxy listener")
+
+		defer restListener.Close()
+		proxy := &http.Server{Handler: mux}
+
+		go func() {
+			err := proxy.Serve(restListener)
+			// ErrServerClosed is always returned when the proxy is
+			// shut down, so don't log it.
+			if err != nil && err != http.ErrServerClosed {
+				log.Error(err)
+			}
+		}()
+	} else {
+		log.Infof("REST proxy disabled")
+	}
 
 	statusChan := make(chan loop.SwapInfo)
 
@@ -178,7 +185,10 @@ func daemon(config *config, lisCfg *listenerCfg) error {
 		defer wg.Done()
 
 		log.Infof("RPC server listening on %s", grpcListener.Addr())
-		log.Infof("REST proxy listening on %s", restListener.Addr())
+
+		if restListener != nil {
+			log.Infof("REST proxy listening on %s", restListener.Addr())
+		}
 
 		err = grpcServer.Serve(grpcListener)
 		if err != nil {
diff --git a/loopd/start.go b/loopd/start.go
index 7f3bbb6..6cd5db6 100644
--- a/loopd/start.go
+++ b/loopd/start.go
@@ -27,19 +27,41 @@ var (
 	swapsLock        sync.Mutex
 )
 
-// newListenerCfg creates and returns a new listenerCfg from the passed config.
-func newListenerCfg(config *config) *listenerCfg {
+// RPCConfig holds optional options that can be used to make the loop daemon
+// communicate on custom connections.
+type RPCConfig struct {
+	// RPCListener is an optional listener that if set will override the
+	// daemon's gRPC settings, and make the gRPC server listen on this
+	// listener.
+	// Note that setting this will also disable REST.
+	RPCListener net.Listener
+}
+
+// newListenerCfg creates and returns a new listenerCfg from the passed config
+// and RPCConfig.
+func newListenerCfg(config *config, rpcCfg RPCConfig) *listenerCfg {
 	return &listenerCfg{
 		grpcListener: func() (net.Listener, error) {
+			// If a custom RPC listener is set, we will listen on
+			// it instead of the regular tcp socket.
+			if rpcCfg.RPCListener != nil {
+				return rpcCfg.RPCListener, nil
+			}
+
 			return net.Listen("tcp", config.RPCListen)
 		},
 		restListener: func() (net.Listener, error) {
+			// If a custom RPC listener is set, we disable REST.
+			if rpcCfg.RPCListener != nil {
+				return nil, nil
+			}
+
 			return net.Listen("tcp", config.RESTListen)
 		},
 	}
 }
 
-func Start() error {
+func Start(rpcCfg RPCConfig) error {
 	config := defaultConfig
 
 	// Parse command line flags.
@@ -112,7 +134,7 @@ func Start() error {
 	// Print the version before executing either primary directive.
 	log.Infof("Version: %v", loop.Version())
 
-	lisCfg := newListenerCfg(&config)
+	lisCfg := newListenerCfg(&config, rpcCfg)
 
 	// Execute command.
 	if parser.Active == nil {