Allow setting default config path and AdminListen at compile time

By providing the following items to `LDFLAGS`:

* `-X github.com/yggdrasil-network/yggdrasil-go/src/defaults.defaultConfig=/path/to/config`
* '-X github.com/yggdrasil-network/yggdrasil-go/src/defaults.defaultAdminListen=unix://path/to/sock'

Closes #818.

src/defaults/defaults.go

@@ -4,6 +4,9 @@ import "github.com/yggdrasil-network/yggdrasil-go/src/config"
 
 type MulticastInterfaceConfig = config.MulticastInterfaceConfig
 
+var defaultConfig = ""      // LDFLAGS='-X github.com/yggdrasil-network/yggdrasil-go/src/defaults.defaultConfig=/path/to/config
+var defaultAdminListen = "" // LDFLAGS='-X github.com/yggdrasil-network/yggdrasil-go/src/defaults.defaultAdminListen=unix://path/to/sock'
+
 // Defines which parameters are expected by default for configuration on a
 // specific platform. These values are populated in the relevant defaults_*.go
 // for the platform being targeted. They must be set.
@@ -23,21 +26,34 @@ type platformDefaultParameters struct {
 	DefaultIfName string
 }
 
+func GetDefaults() platformDefaultParameters {
+	defaults := getDefaults()
+	if defaultConfig != "" {
+		defaults.DefaultConfigFile = defaultConfig
+	}
+	if defaultAdminListen != "" {
+		defaults.DefaultAdminListen = defaultAdminListen
+	}
+	return defaults
+}
+
 // Generates default configuration and returns a pointer to the resulting
 // NodeConfig. This is used when outputting the -genconf parameter and also when
 // using -autoconf.
 func GenerateConfig() *config.NodeConfig {
+	// Get the defaults for the platform.
+	defaults := GetDefaults()
 	// Create a node configuration and populate it.
 	cfg := new(config.NodeConfig)
 	cfg.NewKeys()
 	cfg.Listen = []string{}
-	cfg.AdminListen = GetDefaults().DefaultAdminListen
+	cfg.AdminListen = defaults.DefaultAdminListen
 	cfg.Peers = []string{}
 	cfg.InterfacePeers = map[string][]string{}
 	cfg.AllowedPublicKeys = []string{}
-	cfg.MulticastInterfaces = GetDefaults().DefaultMulticastInterfaces
+	cfg.MulticastInterfaces = defaults.DefaultMulticastInterfaces
-	cfg.IfName = GetDefaults().DefaultIfName
+	cfg.IfName = defaults.DefaultIfName
-	cfg.IfMTU = GetDefaults().DefaultIfMTU
+	cfg.IfMTU = defaults.DefaultIfMTU
 	cfg.NodeInfoPrivacy = false
 
 	return cfg

src/defaults/defaults_darwin.go

@@ -5,7 +5,7 @@ package defaults
 
 // Sane defaults for the macOS/Darwin platform. The "default" options may be
 // may be replaced by the running configuration.
-func GetDefaults() platformDefaultParameters {
+func getDefaults() platformDefaultParameters {
 	return platformDefaultParameters{
 		// Admin
 		DefaultAdminListen: "unix:///var/run/yggdrasil.sock",

src/defaults/defaults_freebsd.go

@@ -5,7 +5,7 @@ package defaults
 
 // Sane defaults for the BSD platforms. The "default" options may be
 // may be replaced by the running configuration.
-func GetDefaults() platformDefaultParameters {
+func getDefaults() platformDefaultParameters {
 	return platformDefaultParameters{
 		// Admin
 		DefaultAdminListen: "unix:///var/run/yggdrasil.sock",

src/defaults/defaults_linux.go

@@ -5,7 +5,7 @@ package defaults
 
 // Sane defaults for the Linux platform. The "default" options may be
 // may be replaced by the running configuration.
-func GetDefaults() platformDefaultParameters {
+func getDefaults() platformDefaultParameters {
 	return platformDefaultParameters{
 		// Admin
 		DefaultAdminListen: "unix:///var/run/yggdrasil.sock",

src/defaults/defaults_openbsd.go

@@ -5,7 +5,7 @@ package defaults
 
 // Sane defaults for the BSD platforms. The "default" options may be
 // may be replaced by the running configuration.
-func GetDefaults() platformDefaultParameters {
+func getDefaults() platformDefaultParameters {
 	return platformDefaultParameters{
 		// Admin
 		DefaultAdminListen: "unix:///var/run/yggdrasil.sock",

src/defaults/defaults_other.go

@@ -5,7 +5,7 @@ package defaults
 
 // Sane defaults for the other platforms. The "default" options may be
 // may be replaced by the running configuration.
-func GetDefaults() platformDefaultParameters {
+func getDefaults() platformDefaultParameters {
 	return platformDefaultParameters{
 		// Admin
 		DefaultAdminListen: "tcp://localhost:9001",

src/defaults/defaults_windows.go

@@ -5,7 +5,7 @@ package defaults
 
 // Sane defaults for the Windows platform. The "default" options may be
 // may be replaced by the running configuration.
-func GetDefaults() platformDefaultParameters {
+func getDefaults() platformDefaultParameters {
 	return platformDefaultParameters{
 		// Admin
 		DefaultAdminListen: "tcp://localhost:9001",