add new QueryStrategy "UseSystem"

app/dns/config.pb.go

@@ -80,6 +80,7 @@ const (
 	QueryStrategy_USE_IP  QueryStrategy = 0
 	QueryStrategy_USE_IP4 QueryStrategy = 1
 	QueryStrategy_USE_IP6 QueryStrategy = 2
+	QueryStrategy_USE_SYS QueryStrategy = 3
 )
 
 // Enum value maps for QueryStrategy.
@@ -88,11 +89,13 @@ var (
 		0: "USE_IP",
 		1: "USE_IP4",
 		2: "USE_IP6",
+		3: "USE_SYS",
 	}
 	QueryStrategy_value = map[string]int32{
 		"USE_IP":  0,
 		"USE_IP4": 1,
 		"USE_IP6": 2,
+		"USE_SYS": 3,
 	}
 )
 
@@ -654,16 +657,16 @@ var file_app_dns_config_proto_rawDesc = []byte{
 	0x63, 0x68, 0x69, 0x6e, 0x67, 0x54, 0x79, 0x70, 0x65, 0x12, 0x08, 0x0a, 0x04, 0x46, 0x75, 0x6c,
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+	0x09, 0x0a, 0x05, 0x52, 0x65, 0x67, 0x65, 0x78, 0x10, 0x03, 0x2a, 0x42, 0x0a, 0x0d, 0x51, 0x75,
 	0x65, 0x72, 0x79, 0x53, 0x74, 0x72, 0x61, 0x74, 0x65, 0x67, 0x79, 0x12, 0x0a, 0x0a, 0x06, 0x55,
 	0x53, 0x45, 0x5f, 0x49, 0x50, 0x10, 0x00, 0x12, 0x0b, 0x0a, 0x07, 0x55, 0x53, 0x45, 0x5f, 0x49,
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-	0x02, 0x42, 0x46, 0x0a, 0x10, 0x63, 0x6f, 0x6d, 0x2e, 0x78, 0x72, 0x61, 0x79, 0x2e, 0x61, 0x70,
+	0x02, 0x12, 0x0b, 0x0a, 0x07, 0x55, 0x53, 0x45, 0x5f, 0x53, 0x59, 0x53, 0x10, 0x03, 0x42, 0x46,
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+	0x0a, 0x10, 0x63, 0x6f, 0x6d, 0x2e, 0x78, 0x72, 0x61, 0x79, 0x2e, 0x61, 0x70, 0x70, 0x2e, 0x64,
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+	0x6e, 0x73, 0x50, 0x01, 0x5a, 0x21, 0x67, 0x69, 0x74, 0x68, 0x75, 0x62, 0x2e, 0x63, 0x6f, 0x6d,
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+	0x2f, 0x78, 0x74, 0x6c, 0x73, 0x2f, 0x78, 0x72, 0x61, 0x79, 0x2d, 0x63, 0x6f, 0x72, 0x65, 0x2f,
-	0x79, 0x2e, 0x41, 0x70, 0x70, 0x2e, 0x44, 0x6e, 0x73, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f,
+	0x61, 0x70, 0x70, 0x2f, 0x64, 0x6e, 0x73, 0xaa, 0x02, 0x0c, 0x58, 0x72, 0x61, 0x79, 0x2e, 0x41,
-	0x33,
+	0x70, 0x70, 0x2e, 0x44, 0x6e, 0x73, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (

app/dns/config.proto

@@ -48,6 +48,7 @@ enum QueryStrategy {
   USE_IP = 0;
   USE_IP4 = 1;
   USE_IP6 = 2;
+  USE_SYS = 3;
 }
 
 message Config {

app/dns/dns.go

@@ -28,6 +28,7 @@ type DNS struct {
 	ctx                    context.Context
 	domainMatcher          strmatcher.IndexMatcher
 	matcherInfos           []*DomainMatcherInfo
+	useSystem              bool
 }
 
 // DomainMatcherInfo contains information attached to index returned by Server.domainMatcher
@@ -47,6 +48,7 @@ func New(ctx context.Context, config *Config) (*DNS, error) {
 	}
 
 	var ipOption dns.IPOption
+	useSystem := false
 	switch config.QueryStrategy {
 	case QueryStrategy_USE_IP:
 		ipOption = dns.IPOption{
@@ -54,6 +56,13 @@ func New(ctx context.Context, config *Config) (*DNS, error) {
 			IPv6Enable: true,
 			FakeEnable: false,
 		}
+	case QueryStrategy_USE_SYS:
+		ipOption = dns.IPOption{
+			IPv4Enable: true,
+			IPv6Enable: true,
+			FakeEnable: false,
+		}
+		useSystem = true
 	case QueryStrategy_USE_IP4:
 		ipOption = dns.IPOption{
 			IPv4Enable: true,
@@ -118,6 +127,7 @@ func New(ctx context.Context, config *Config) (*DNS, error) {
 		if !clientIPOption.IPv4Enable && !clientIPOption.IPv6Enable {
 			return nil, errors.New("no QueryStrategy available for ", ns.Address)
 		}
+
 		client, err := NewClient(ctx, ns, myClientIP, disableCache, tag, clientIPOption, &matcherInfos, updateDomain)
 		if err != nil {
 			return nil, errors.New("failed to create client").Base(err)
@@ -139,6 +149,7 @@ func New(ctx context.Context, config *Config) (*DNS, error) {
 		matcherInfos:           matcherInfos,
 		disableFallback:        config.DisableFallback,
 		disableFallbackIfMatch: config.DisableFallbackIfMatch,
+		useSystem:              useSystem,
 	}, nil
 }
 
@@ -179,8 +190,14 @@ func (s *DNS) LookupIP(domain string, option dns.IPOption) ([]net.IP, uint32, er
 		return nil, 0, errors.New("empty domain name")
 	}
 
-	option.IPv4Enable = option.IPv4Enable && s.ipOption.IPv4Enable
+	if s.useSystem {
-	option.IPv6Enable = option.IPv6Enable && s.ipOption.IPv6Enable
+		supportIPv4, supportIPv6 := checkSystemNetwork()
+		option.IPv4Enable = option.IPv4Enable && supportIPv4
+		option.IPv6Enable = option.IPv6Enable && supportIPv6
+	} else {
+		option.IPv4Enable = option.IPv4Enable && s.ipOption.IPv4Enable
+		option.IPv6Enable = option.IPv6Enable && s.ipOption.IPv6Enable
+	}
 
 	if !option.IPv4Enable && !option.IPv6Enable {
 		return nil, 0, dns.ErrEmptyResponse
@@ -321,3 +338,22 @@ func init() {
 		return New(ctx, config.(*Config))
 	}))
 }
+
+func checkSystemNetwork() (supportIPv4 bool, supportIPv6 bool) {
+	conn4, err4 := net.Dial("udp4", "8.8.8.8:53")
+	if err4 != nil {
+		supportIPv4 = false
+	} else {
+		supportIPv4 = true
+		conn4.Close()
+	}
+
+	conn6, err6 := net.Dial("udp6", "[2001:4860:4860::8888]:53")
+	if err6 != nil {
+		supportIPv6 = false
+	} else {
+		supportIPv6 = true
+		conn6.Close()
+	}
+	return
+}

app/dns/nameserver.go

@@ -37,6 +37,7 @@ type Client struct {
 	timeoutMs     time.Duration
 	finalQuery    bool
 	ipOption      *dns.IPOption
+	useSystem     bool
 }
 
 // NewServer creates a name server object according to the network destination url.
@@ -186,6 +187,8 @@ func NewClient(
 			timeoutMs = time.Duration(ns.TimeoutMs) * time.Millisecond
 		}
 
+		useSystem := ns.QueryStrategy == QueryStrategy_USE_SYS
+
 		client.server = server
 		client.skipFallback = ns.SkipFallback
 		client.domains = rules
@@ -197,6 +200,7 @@ func NewClient(
 		client.timeoutMs = timeoutMs
 		client.finalQuery = ns.FinalQuery
 		client.ipOption = &ipOption
+		client.useSystem = useSystem
 		return nil
 	})
 	return client, err
@@ -213,8 +217,15 @@ func (c *Client) IsFinalQuery() bool {
 
 // QueryIP sends DNS query to the name server with the client's IP.
 func (c *Client) QueryIP(ctx context.Context, domain string, option dns.IPOption) ([]net.IP, uint32, error) {
-	option.IPv4Enable = option.IPv4Enable && c.ipOption.IPv4Enable
+	if c.useSystem {
-	option.IPv6Enable = option.IPv6Enable && c.ipOption.IPv6Enable
+		supportIPv4, supportIPv6 := checkSystemNetwork()
+		option.IPv4Enable = option.IPv4Enable && supportIPv4
+		option.IPv6Enable = option.IPv6Enable && supportIPv6
+	} else {
+		option.IPv4Enable = option.IPv4Enable && c.ipOption.IPv4Enable
+		option.IPv6Enable = option.IPv6Enable && c.ipOption.IPv6Enable
+	}
+
 	if !option.IPv4Enable && !option.IPv6Enable {
 		return nil, 0, dns.ErrEmptyResponse
 	}
@@ -271,6 +282,8 @@ func ResolveIpOptionOverride(queryStrategy QueryStrategy, ipOption dns.IPOption)
 	switch queryStrategy {
 	case QueryStrategy_USE_IP:
 		return ipOption
+	case QueryStrategy_USE_SYS:
+		return ipOption
 	case QueryStrategy_USE_IP4:
 		return dns.IPOption{
 			IPv4Enable: ipOption.IPv4Enable,

infra/conf/dns.go

@@ -425,6 +425,8 @@ func resolveQueryStrategy(queryStrategy string) dns.QueryStrategy {
 		return dns.QueryStrategy_USE_IP4
 	case "useip6", "useipv6", "use_ip6", "use_ipv6", "use_ip_v6", "use-ip6", "use-ipv6", "use-ip-v6":
 		return dns.QueryStrategy_USE_IP6
+	case "usesys", "usesystem", "use_sys", "use_system", "use-sys", "use-system":
+		return dns.QueryStrategy_USE_SYS
 	default:
 		return dns.QueryStrategy_USE_IP
 	}