Add Fake DNS support (#309)

Co-authored-by: Xiaokang Wang <xiaokangwang@outlook.com>
Co-authored-by: loyalsoldier <10487845+Loyalsoldier@users.noreply.github.com>
Co-authored-by: kslr <kslrwang@gmail.com>

features/dns/client.go

@@ -7,6 +7,13 @@ import (
 	"github.com/xtls/xray-core/features"
 )
 
+// IPOption is an object for IP query options.
+type IPOption struct {
+	IPv4Enable bool
+	IPv6Enable bool
+	FakeEnable bool
+}
+
 // Client is a Xray feature for querying DNS information.
 //
 // xray:api:stable
@@ -14,21 +21,7 @@ type Client interface {
 	features.Feature
 
 	// 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.
-//
-// xray:api:beta
-type IPv4Lookup interface {
-	LookupIPv4(domain string) ([]net.IP, error)
-}
-
-// IPv6Lookup is an optional feature for querying IPv6 addresses only.
-//
-// xray:api:beta
-type IPv6Lookup interface {
-	LookupIPv6(domain string) ([]net.IP, error)
+	LookupIP(domain string, option IPOption) ([]net.IP, error)
 }
 
 // ClientType returns the type of Client interface. Can be used for implementing common.HasType.

features/dns/fakedns.go

@@ -0,0 +1,15 @@
+package dns
+
+import (
+	gonet "net"
+
+	"github.com/xtls/xray-core/common/net"
+	"github.com/xtls/xray-core/features"
+)
+
+type FakeDNSEngine interface {
+	features.Feature
+	GetFakeIPForDomain(domain string) []net.Address
+	GetDomainFromFakeDNS(ip net.Address) string
+	GetFakeIPRange() *gonet.IPNet
+}

features/dns/localdns/client.go

@@ -20,58 +20,41 @@ func (*Client) Start() error { return nil }
 func (*Client) Close() error { return nil }
 
 // LookupIP implements Client.
-func (*Client) LookupIP(host string) ([]net.IP, error) {
+func (*Client) LookupIP(host string, option dns.IPOption) ([]net.IP, error) {
 	ips, err := net.LookupIP(host)
 	if err != nil {
 		return nil, err
 	}
 	parsedIPs := make([]net.IP, 0, len(ips))
+	ipv4 := make([]net.IP, 0, len(ips))
+	ipv6 := make([]net.IP, 0, len(ips))
 	for _, ip := range ips {
 		parsed := net.IPAddress(ip)
 		if parsed != nil {
 			parsedIPs = append(parsedIPs, parsed.IP())
 		}
-	}
-	if len(parsedIPs) == 0 {
-		return nil, dns.ErrEmptyResponse
-	}
-	return parsedIPs, nil
-}
-
-// LookupIPv4 implements IPv4Lookup.
-func (c *Client) LookupIPv4(host string) ([]net.IP, error) {
-	ips, err := c.LookupIP(host)
-	if err != nil {
-		return nil, err
-	}
-	ipv4 := make([]net.IP, 0, len(ips))
-	for _, ip := range ips {
 		if len(ip) == net.IPv4len {
 			ipv4 = append(ipv4, ip)
 		}
-	}
-	if len(ipv4) == 0 {
-		return nil, dns.ErrEmptyResponse
-	}
-	return ipv4, nil
-}
-
-// LookupIPv6 implements IPv6Lookup.
-func (c *Client) LookupIPv6(host string) ([]net.IP, error) {
-	ips, err := c.LookupIP(host)
-	if err != nil {
-		return nil, err
-	}
-	ipv6 := make([]net.IP, 0, len(ips))
-	for _, ip := range ips {
 		if len(ip) == net.IPv6len {
 			ipv6 = append(ipv6, ip)
 		}
 	}
-	if len(ipv6) == 0 {
-		return nil, dns.ErrEmptyResponse
+	switch {
+	case option.IPv4Enable && option.IPv6Enable:
+		if len(parsedIPs) > 0 {
+			return parsedIPs, nil
+		}
+	case option.IPv4Enable:
+		if len(ipv4) > 0 {
+			return ipv4, nil
+		}
+	case option.IPv6Enable:
+		if len(ipv6) > 0 {
+			return ipv6, nil
+		}
 	}
-	return ipv6, nil
+	return nil, dns.ErrEmptyResponse
 }
 
 // New create a new dns.Client that queries localhost for DNS.

features/dns/localdns/errors.generated.go

@@ -0,0 +1,9 @@
+package localdns
+
+import "github.com/xtls/xray-core/common/errors"
+
+type errPathObjHolder struct{}
+
+func newError(values ...interface{}) *errors.Error {
+	return errors.New(values...).WithPathObj(errPathObjHolder{})
+}

features/routing/dns/context.go

@@ -26,7 +26,11 @@ func (ctx *ResolvableContext) GetTargetIPs() []net.IP {
 	}
 
 	if domain := ctx.GetTargetDomain(); len(domain) != 0 {
-		ips, err := ctx.dnsClient.LookupIP(domain)
+		ips, err := ctx.dnsClient.LookupIP(domain, dns.IPOption{
+			IPv4Enable: true,
+			IPv6Enable: true,
+			FakeEnable: false,
+		})
 		if err == nil {
 			ctx.resolvedIPs = ips
 			return ips