feat: update bootstrap_dns_android (#966)

* update with non_specified network

* remove wrongs

* add alternative bootstrapDialer

* do test

* Update dns_bootstrap_android_test.go

* example of alternative dialer

* public method

* move const

* Update dns_bootstrap_android_test.go

* no duplicated

* Rename infra/conf/dns_bootstrap_android.go to transport/internet/system_dns_android.go

* Update system_dns_android.go

* Update and rename infra/conf/dns_bootstrap_android_test.go to transport/internet/system_dns_android_test.go

* no imports

* Update system_dns_android.go

* Update system_dns_android_test.go

* create systemDNS

* Create system_dns_android.go

* Update system_dialer.go

* call Resolver on systemDialer

* create system_dns_test.go

* resolver.LookupIP params

* param fix

* noneed TestSystemDNSResolver

* revert: no specified resolver

* Delete system_dns.go

* android only

* android only test

* typo

infra/conf/dns_bootstrap_android.go

@@ -1,24 +0,0 @@
-// +build android
-
-package conf
-
-import (
-	"context"
-	"net"
-)
-
-func init() {
-	const bootstrapDNS = "8.8.8.8:53"
-	var dialer net.Dialer
-	net.DefaultResolver = &net.Resolver{
-		PreferGo: true,
-		Dial: func(context context.Context, _, _ string) (net.Conn, error) {
-			conn, err := dialer.DialContext(context, "udp", bootstrapDNS)
-			if err != nil {
-				return nil, err
-			}
-			return conn, nil
-		},
-	}
-	newError("Bootstrap DNS: ", bootstrapDNS).AtWarning().WriteToLog()
-}

infra/conf/dns_bootstrap_test.go

@@ -1,28 +0,0 @@
-package conf
-
-import (
-	"context"
-	"net"
-	"testing"
-)
-
-func TestBootstrapDNS(t *testing.T) {
-	const (
-		defaultNS = "8.8.8.8:53"
-		domain    = "github.com"
-	)
-	var dialer net.Dialer
-	net.DefaultResolver = &net.Resolver{
-		PreferGo: true,
-		Dial: func(context context.Context, network, address string) (net.Conn, error) {
-			conn, err := dialer.DialContext(context, "udp", defaultNS)
-			if err != nil {
-				return nil, err
-			}
-			return conn, nil
-		},
-	}
-	if ips, err := net.LookupIP(domain); len(ips) == 0 {
-		t.Error("set BootstrapDNS failed: ", err)
-	}
-}

transport/internet/system_dns_android.go

@@ -0,0 +1,26 @@
+// +build android
+
+package internet
+
+import (
+	"context"
+	"net"
+)
+
+const SystemDNS = "8.8.8.8:53"
+
+type DNSResolverFunc func() *net.Resolver
+
+var NewDNSResolver DNSResolverFunc = func() *net.Resolver {
+	return &net.Resolver{
+		PreferGo: true,
+		Dial: func(ctx context.Context, network, _ string) (net.Conn, error) {
+			var dialer net.Dialer
+			return dialer.DialContext(ctx, network, SystemDNS)
+		},
+	}
+}
+
+func init() {
+	net.DefaultResolver = NewDNSResolver()
+}

transport/internet/system_dns_android_test.go

@@ -0,0 +1,15 @@
+// +build android
+
+package internet
+
+import (
+	"context"
+	"testing"
+)
+
+func TestDNSResolver(t *testing.T) {
+	resolver := NewDNSResolver()
+	if ips, err := resolver.LookupIP(context.Background(), "ip", "www.google.com"); err != nil {
+		t.Errorf("failed to lookupIP, %v, %v", ips, err)
+	}
+}