config+test: use default port for RPC server if one isn't specified

This commit alters the configuration parsing a bit along with the
documentation to expect the RPCHost configuration paramter to also have
the target port specified. If the port isn’t included, then the default
btcd RPC port for that chain is used.

Additionally, within the integration testing framework, when creating
the lnd nodes, we now use the configuration from the btcd harness to
set the proper RPC host.

config.go

@@ -63,7 +63,7 @@ type config struct {
 	PeerPort int    `long:"peerport" description:"The port to listen on for incoming p2p connections"`
 	RPCPort  int    `long:"rpcport" description:"The port for the rpc server"`
 	SPVMode  bool   `long:"spv" description:"assert to enter spv wallet mode"`
-	RPCHost  string `long:"btcdhost" description:"The btcd rpc listening address."`
+	RPCHost  string `long:"btcdhost" description:"The btcd rpc listening address. If a port is omitted, then the default port for the selected chain parameters will be used."`
 	RPCUser  string `short:"u" long:"rpcuser" description:"Username for RPC connections"`
 	RPCPass  string `short:"P" long:"rpcpass" default-mask:"-" description:"Password for RPC connections"`
 

lnd.go

@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"strconv"
+	"strings"
 
 	"golang.org/x/net/context"
 
@@ -90,13 +91,16 @@ func lndMain() error {
 		}
 	}
 
-	rpcIP, err := net.LookupHost(cfg.RPCHost)
-	if err != nil {
-		fmt.Printf("unable to resolve rpc host: %v", err)
-		return err
+	// If the specified host for the btcd RPC server already has a port
+	// specified, then we use that directly. Otherwise, we assume the
+	// default port according to the selected chain parameters.
+	var btcdHost string
+	if strings.Contains(cfg.RPCHost, ":") {
+		btcdHost = cfg.RPCHost
+	} else {
+		btcdHost = fmt.Sprintf("%v:%v", cfg.RPCHost, activeNetParams.rpcPort)
 	}
 
-	btcdHost := fmt.Sprintf("%v:%v", cfg.RPCHost, activeNetParams.rpcPort)
 	btcdUser := cfg.RPCUser
 	btcdPass := cfg.RPCPass
 
@@ -120,7 +124,7 @@ func lndMain() error {
 	walletConfig := &btcwallet.Config{
 		PrivatePass: []byte("hello"),
 		DataDir:     filepath.Join(cfg.DataDir, "lnwallet"),
-		RpcHost:     fmt.Sprintf("%v:%v", rpcIP[0], activeNetParams.rpcPort),
+		RpcHost:     btcdHost,
 		RpcUser:     cfg.RPCUser,
 		RpcPass:     cfg.RPCPass,
 		CACert:      rpcCert,

networktest.go

@@ -106,7 +106,7 @@ func newLightningNode(rpcConfig *btcrpcclient.ConnConfig, lndArgs []string) (*li
 	var err error
 
 	cfg := &config{
-		RPCHost: "127.0.0.1",
+		RPCHost: rpcConfig.Host,
 		RPCUser: rpcConfig.User,
 		RPCPass: rpcConfig.Pass,
 	}