access android name servers from SDK.

cmd/cli/library.go

@@ -3,10 +3,11 @@ package cli
 // AppCallback provides hooks for injecting certain functionalities
 // from mobile platforms to main ctrld cli.
 type AppCallback struct {
-	HostName   func() string
-	LanIp      func() string
-	MacAddress func() string
-	Exit       func(error string)
+	HostName           func() string
+	LanIp              func() string
+	MacAddress         func() string
+	AndroidNameServers func() []string
+	Exit               func(error string)
 }
 
 // AppConfig allows overwriting ctrld cli flags from mobile platforms.

cmd/cli/prog.go

@@ -241,10 +241,20 @@ func (p *prog) preRun() {
 	}
 }
 
+// androidNameServers Only way to access system resolvers on android is through SDK.
+// due to proc/net access not permitted.
+func (p *prog) androidNameServers() []string {
+	if isAndroid() {
+		return p.appCallback.AndroidNameServers()
+	} else {
+		return nil
+	}
+}
+
 func (p *prog) postRun() {
 	if !service.Interactive() {
 		p.resetDNS()
-		ns := ctrld.InitializeOsResolver()
+		ns := ctrld.InitializeOsResolver(p.androidNameServers())
 		mainLog.Load().Debug().Msgf("initialized OS resolver with nameservers: %v", ns)
 		p.setDNS()
 		p.csSetDnsDone <- struct{}{}

cmd/ctrld_library/main.go

@@ -22,6 +22,7 @@ type AppCallback interface {
 	Hostname() string
 	LanIp() string
 	MacAddress() string
+	AndroidNameServers() []string
 	Exit(error string)
 }
 
@@ -55,6 +56,9 @@ func mapCallback(callback AppCallback) cli.AppCallback {
 		MacAddress: func() string {
 			return callback.MacAddress()
 		},
+		AndroidNameServers: func() []string {
+			return callback.AndroidNameServers()
+		},
 		Exit: func(err string) {
 			callback.Exit(err)
 		},

resolver.go

@@ -82,8 +82,12 @@ func availableNameservers() []string {
 //
 // It's the caller's responsibility to ensure the system DNS is in a clean state before
 // calling this function.
-func InitializeOsResolver() []string {
-	return initializeOsResolver(availableNameservers())
+func InitializeOsResolver(androidNameServers []string) []string {
+	if androidNameServers != nil {
+		return initializeOsResolver(androidNameServers)
+	} else {
+		return initializeOsResolver(availableNameservers())
+	}
 }
 func initializeOsResolver(servers []string) []string {
 	var (