support querying either IPv4 or IPv6 dns

features/dns/client.go

@@ -8,29 +8,22 @@ import (
 // Client is a V2Ray feature for querying DNS information.
 type Client interface {
 	features.Feature
-	LookupIP(host string) ([]net.IP, error)
+
+	// LookupIP returns IP address for the given domain. IPs may contain IPv4 and/or IPv6 addresses.
+	LookupIP(domain string) ([]net.IP, error)
+}
+
+// IPv4Lookup is an optional feature for querying IPv4 addresses only.
+type IPv4Lookup interface {
+	LookupIPv4(domain string) ([]net.IP, error)
+}
+
+// IPv6Lookup is an optional feature for querying IPv6 addresses only.
+type IPv6Lookup interface {
+	LookupIPv6(domain string) ([]net.IP, error)
 }
 
 // ClientType returns the type of Client interface. Can be used for implementing common.HasType.
 func ClientType() interface{} {
 	return (*Client)(nil)
 }
-
-// LocalClient is an implementation of Client, which queries localhost for DNS.
-type LocalClient struct{}
-
-// Type implements common.HasType.
-func (LocalClient) Type() interface{} {
-	return ClientType()
-}
-
-// Start implements common.Runnable.
-func (LocalClient) Start() error { return nil }
-
-// Close implements common.Closable.
-func (LocalClient) Close() error { return nil }
-
-// LookupIP implements Client.
-func (LocalClient) LookupIP(host string) ([]net.IP, error) {
-	return net.LookupIP(host)
-}

features/dns/localdns/client.go

@@ -0,0 +1,73 @@
+package localdns
+
+import (
+	"context"
+	"net"
+
+	"v2ray.com/core/features/dns"
+)
+
+// Client is an implementation of dns.Client, which queries localhost for DNS.
+type Client struct {
+	resolver net.Resolver
+}
+
+// Type implements common.HasType.
+func (*Client) Type() interface{} {
+	return dns.ClientType()
+}
+
+// Start implements common.Runnable.
+func (*Client) Start() error { return nil }
+
+// Close implements common.Closable.
+func (*Client) Close() error { return nil }
+
+// LookupIP implements Client.
+func (c *Client) LookupIP(host string) ([]net.IP, error) {
+	ipAddr, err := c.resolver.LookupIPAddr(context.Background(), host)
+	if err != nil {
+		return nil, err
+	}
+	ips := make([]net.IP, 0, len(ipAddr))
+	for _, addr := range ipAddr {
+		ips = append(ips, addr.IP)
+	}
+	return ips, nil
+}
+
+func (c *Client) LookupIPv4(host string) ([]net.IP, error) {
+	ips, err := c.LookupIP(host)
+	if err != nil {
+		return nil, err
+	}
+	var ipv4 []net.IP
+	for _, ip := range ips {
+		if len(ip) == net.IPv4len {
+			ipv4 = append(ipv4, ip)
+		}
+	}
+	return ipv4, nil
+}
+
+func (c *Client) LookupIPv6(host string) ([]net.IP, error) {
+	ips, err := c.LookupIP(host)
+	if err != nil {
+		return nil, err
+	}
+	var ipv6 []net.IP
+	for _, ip := range ips {
+		if len(ip) == net.IPv6len {
+			ipv6 = append(ipv6, ip)
+		}
+	}
+	return ipv6, nil
+}
+
+func New() *Client {
+	return &Client{
+		resolver: net.Resolver{
+			PreferGo: true,
+		},
+	}
+}