Add dns client

dns/client.go

@@ -0,0 +1,327 @@
+package dns
+
+import (
+	"context"
+	"net"
+	"net/netip"
+	"time"
+
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/cache"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/task"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+
+	"golang.org/x/net/dns/dnsmessage"
+)
+
+const DefaultTTL = 600
+
+var (
+	ErrNoRawSupport = E.New("no raw query support by current transport")
+	ErrNotCached    = E.New("not cached")
+)
+
+var _ adapter.DNSClient = (*Client)(nil)
+
+type Client struct {
+	cache *cache.LruCache[dnsmessage.Question, dnsmessage.Message]
+}
+
+func NewClient() *Client {
+	return &Client{
+		cache: cache.New[dnsmessage.Question, dnsmessage.Message](),
+	}
+}
+
+func (c *Client) Exchange(ctx context.Context, transport adapter.DNSTransport, message *dnsmessage.Message) (*dnsmessage.Message, error) {
+	if len(message.Questions) == 0 {
+		return nil, E.New("empty query")
+	}
+	question := message.Questions[0]
+	cachedAnswer, cached := c.cache.Load(question)
+	if cached {
+		cachedAnswer.ID = message.ID
+		return &cachedAnswer, nil
+	}
+	if !transport.Raw() {
+		if question.Type == dnsmessage.TypeA || question.Type == dnsmessage.TypeAAAA {
+			return c.exchangeToLookup(ctx, transport, message, question)
+		}
+		return nil, ErrNoRawSupport
+	}
+	response, err := transport.Exchange(ctx, message)
+	if err != nil {
+		return nil, err
+	}
+	c.cache.StoreWithExpire(question, *response, calculateExpire(message))
+	return message, err
+}
+
+func (c *Client) Lookup(ctx context.Context, transport adapter.DNSTransport, domain string, strategy C.DomainStrategy) ([]netip.Addr, error) {
+	dnsName, err := dnsmessage.NewName(domain)
+	if err != nil {
+		return nil, wrapError(err)
+	}
+	if transport.Raw() {
+		if strategy == C.DomainStrategyUseIPv4 {
+			return c.lookupToExchange(ctx, transport, dnsName, dnsmessage.TypeA)
+		} else if strategy == C.DomainStrategyUseIPv6 {
+			return c.lookupToExchange(ctx, transport, dnsName, dnsmessage.TypeAAAA)
+		}
+		var response4 []netip.Addr
+		var response6 []netip.Addr
+		err = task.Run(ctx, func() error {
+			response, err := c.lookupToExchange(ctx, transport, dnsName, dnsmessage.TypeA)
+			if err != nil {
+				return err
+			}
+			response4 = response
+			return nil
+		}, func() error {
+			response, err := c.lookupToExchange(ctx, transport, dnsName, dnsmessage.TypeAAAA)
+			if err != nil {
+				return err
+			}
+			response6 = response
+			return nil
+		})
+		if len(response4) == 0 && len(response6) == 0 {
+			return nil, err
+		}
+		return sortAddresses(response4, response6, strategy), nil
+	}
+	if strategy == C.DomainStrategyUseIPv4 {
+		response, err := c.questionCache(dnsmessage.Question{
+			Name:  dnsName,
+			Type:  dnsmessage.TypeA,
+			Class: dnsmessage.ClassINET,
+		})
+		if err != ErrNotCached {
+			return response, err
+		}
+	} else if strategy == C.DomainStrategyUseIPv6 {
+		response, err := c.questionCache(dnsmessage.Question{
+			Name:  dnsName,
+			Type:  dnsmessage.TypeAAAA,
+			Class: dnsmessage.ClassINET,
+		})
+		if err != ErrNotCached {
+			return response, err
+		}
+	} else {
+		response4, _ := c.questionCache(dnsmessage.Question{
+			Name:  dnsName,
+			Type:  dnsmessage.TypeA,
+			Class: dnsmessage.ClassINET,
+		})
+		response6, _ := c.questionCache(dnsmessage.Question{
+			Name:  dnsName,
+			Type:  dnsmessage.TypeAAAA,
+			Class: dnsmessage.ClassINET,
+		})
+		if len(response4) > 0 || len(response6) > 0 {
+			return sortAddresses(response4, response6, strategy), nil
+		}
+	}
+	var rCode dnsmessage.RCode
+	response, err := transport.Lookup(ctx, domain, strategy)
+	if err != nil {
+		err = wrapError(err)
+		if rCodeError, isRCodeError := err.(RCodeError); !isRCodeError {
+			return nil, err
+		} else {
+			rCode = dnsmessage.RCode(rCodeError)
+		}
+	}
+	header := dnsmessage.Header{
+		Response:      true,
+		Authoritative: true,
+		RCode:         rCode,
+	}
+	expire := time.Now().Add(time.Second * time.Duration(DefaultTTL))
+	if strategy != C.DomainStrategyUseIPv6 {
+		question4 := dnsmessage.Question{
+			Name:  dnsName,
+			Type:  dnsmessage.TypeA,
+			Class: dnsmessage.ClassINET,
+		}
+		response4 := common.Filter(response, func(addr netip.Addr) bool {
+			return addr.Is4() || addr.Is4In6()
+		})
+		message4 := dnsmessage.Message{
+			Header:    header,
+			Questions: []dnsmessage.Question{question4},
+		}
+		if len(response4) > 0 {
+			for _, address := range response4 {
+				message4.Answers = append(message4.Answers, dnsmessage.Resource{
+					Header: dnsmessage.ResourceHeader{
+						Name:  question4.Name,
+						Class: question4.Class,
+						TTL:   DefaultTTL,
+					},
+					Body: &dnsmessage.AResource{
+						A: address.As4(),
+					},
+				})
+			}
+		}
+		c.cache.StoreWithExpire(question4, message4, expire)
+	}
+	if strategy != C.DomainStrategyUseIPv4 {
+		question6 := dnsmessage.Question{
+			Name:  dnsName,
+			Type:  dnsmessage.TypeAAAA,
+			Class: dnsmessage.ClassINET,
+		}
+		response6 := common.Filter(response, func(addr netip.Addr) bool {
+			return addr.Is6() && !addr.Is4In6()
+		})
+		message6 := dnsmessage.Message{
+			Header:    header,
+			Questions: []dnsmessage.Question{question6},
+		}
+		if len(response6) > 0 {
+			for _, address := range response6 {
+				message6.Answers = append(message6.Answers, dnsmessage.Resource{
+					Header: dnsmessage.ResourceHeader{
+						Name:  question6.Name,
+						Class: question6.Class,
+						TTL:   DefaultTTL,
+					},
+					Body: &dnsmessage.AAAAResource{
+						AAAA: address.As16(),
+					},
+				})
+			}
+		}
+		c.cache.StoreWithExpire(question6, message6, expire)
+	}
+	return response, err
+}
+
+func sortAddresses(response4 []netip.Addr, response6 []netip.Addr, strategy C.DomainStrategy) []netip.Addr {
+	if strategy == C.DomainStrategyPreferIPv6 {
+		return append(response6, response4...)
+	} else {
+		return append(response4, response6...)
+	}
+}
+
+func calculateExpire(message *dnsmessage.Message) time.Time {
+	timeToLive := DefaultTTL
+	for _, answer := range message.Answers {
+		if int(answer.Header.TTL) < timeToLive {
+			timeToLive = int(answer.Header.TTL)
+		}
+	}
+	return time.Now().Add(time.Second * time.Duration(timeToLive))
+}
+
+func (c *Client) exchangeToLookup(ctx context.Context, transport adapter.DNSTransport, message *dnsmessage.Message, question dnsmessage.Question) (*dnsmessage.Message, error) {
+	domain := question.Name.String()
+	var strategy C.DomainStrategy
+	if question.Type == dnsmessage.TypeA {
+		strategy = C.DomainStrategyUseIPv4
+	} else {
+		strategy = C.DomainStrategyUseIPv6
+	}
+	var rCode dnsmessage.RCode
+	result, err := c.Lookup(ctx, transport, domain, strategy)
+	if err != nil {
+		err = wrapError(err)
+		if rCodeError, isRCodeError := err.(RCodeError); !isRCodeError {
+			return nil, err
+		} else {
+			rCode = dnsmessage.RCode(rCodeError)
+		}
+	}
+	response := dnsmessage.Message{
+		Header: dnsmessage.Header{
+			ID:                 message.ID,
+			RCode:              rCode,
+			RecursionAvailable: true,
+			RecursionDesired:   true,
+			Response:           true,
+		},
+		Questions: message.Questions,
+	}
+	for _, address := range result {
+		var resource dnsmessage.Resource
+		resource.Header = dnsmessage.ResourceHeader{
+			Name:  question.Name,
+			Class: question.Class,
+			TTL:   DefaultTTL,
+		}
+		if address.Is4() || address.Is4In6() {
+			resource.Body = &dnsmessage.AResource{
+				A: address.As4(),
+			}
+		} else {
+			resource.Body = &dnsmessage.AAAAResource{
+				AAAA: address.As16(),
+			}
+		}
+	}
+	return &response, nil
+}
+
+func (c *Client) lookupToExchange(ctx context.Context, transport adapter.DNSTransport, name dnsmessage.Name, qType dnsmessage.Type) ([]netip.Addr, error) {
+	question := dnsmessage.Question{
+		Name:  name,
+		Type:  qType,
+		Class: dnsmessage.ClassINET,
+	}
+	cachedAddresses, err := c.questionCache(question)
+	if err != ErrNotCached {
+		return cachedAddresses, err
+	}
+	message := dnsmessage.Message{
+		Header: dnsmessage.Header{
+			ID:               0,
+			RecursionDesired: true,
+		},
+		Questions: []dnsmessage.Question{question},
+	}
+	response, err := c.Exchange(ctx, transport, &message)
+	if err != nil {
+		return nil, err
+	}
+	return messageToAddresses(response)
+}
+
+func (c *Client) questionCache(question dnsmessage.Question) ([]netip.Addr, error) {
+	response, cached := c.cache.Load(question)
+	if !cached {
+		return nil, ErrNotCached
+	}
+	return messageToAddresses(&response)
+}
+
+func messageToAddresses(response *dnsmessage.Message) ([]netip.Addr, error) {
+	if response.RCode != dnsmessage.RCodeSuccess {
+		return nil, RCodeError(response.RCode)
+	}
+	addresses := make([]netip.Addr, 0, len(response.Answers))
+	for _, answer := range response.Answers {
+		switch resource := answer.Body.(type) {
+		case *dnsmessage.AResource:
+			addresses = append(addresses, netip.AddrFrom4(resource.A))
+		case *dnsmessage.AAAAResource:
+			addresses = append(addresses, netip.AddrFrom16(resource.AAAA))
+		}
+	}
+	return addresses, nil
+}
+
+func wrapError(err error) error {
+	if dnsErr, isDNSError := err.(*net.DNSError); isDNSError {
+		if dnsErr.IsNotFound {
+			return RCodeNameError
+		}
+	}
+	return err
+}

dns/rcode.go

@@ -0,0 +1,33 @@
+package dns
+
+import F "github.com/sagernet/sing/common/format"
+
+const (
+	RCodeSuccess        RCodeError = 0 // NoError
+	RCodeFormatError    RCodeError = 1 // FormErr
+	RCodeServerFailure  RCodeError = 2 // ServFail
+	RCodeNameError      RCodeError = 3 // NXDomain
+	RCodeNotImplemented RCodeError = 4 // NotImp
+	RCodeRefused        RCodeError = 5 // Refused
+)
+
+type RCodeError uint16
+
+func (e RCodeError) Error() string {
+	switch e {
+	case RCodeSuccess:
+		return "success"
+	case RCodeFormatError:
+		return "format error"
+	case RCodeServerFailure:
+		return "server failure"
+	case RCodeNameError:
+		return "name error"
+	case RCodeNotImplemented:
+		return "not implemented"
+	case RCodeRefused:
+		return "refused"
+	default:
+		return F.ToString("unknown error: ", uint16(e))
+	}
+}

dns/transport.go

@@ -2,17 +2,40 @@ package dns
 
 import (
 	"context"
-	"net/netip"
+	"net/url"
+
+	E "github.com/sagernet/sing/common/exceptions"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
 
 	"github.com/sagernet/sing-box/adapter"
-	C "github.com/sagernet/sing-box/constant"
-
-	"golang.org/x/net/dns/dnsmessage"
+	"github.com/sagernet/sing-box/log"
 )
 
-type Transport interface {
-	adapter.Service
-	Raw() bool
-	Exchange(ctx context.Context, message *dnsmessage.Message) (*dnsmessage.Message, error)
-	Lookup(ctx context.Context, domain string, strategy C.DomainStrategy) ([]netip.Addr, error)
+func NewTransport(ctx context.Context, dialer N.Dialer, logger log.Logger, address string) (adapter.DNSTransport, error) {
+	if address == "local" {
+		return NewLocalTransport(), nil
+	}
+	serverURL, err := url.Parse(address)
+	if err != nil {
+		return nil, err
+	}
+	host := serverURL.Hostname()
+	port := serverURL.Port()
+	if port == "" {
+		port = "53"
+	}
+	destination := M.ParseSocksaddrHostPortStr(host, port)
+	switch serverURL.Scheme {
+	case "", "udp":
+		return NewUDPTransport(ctx, dialer, logger, destination), nil
+	case "tcp":
+		return NewTCPTransport(ctx, dialer, logger, destination), nil
+	case "tls":
+		return NewTLSTransport(ctx, dialer, logger, destination), nil
+	case "https":
+		return NewHTTPSTransport(dialer, serverURL.String()), nil
+	default:
+		return nil, E.New("unknown dns scheme: " + serverURL.Scheme)
+	}
 }

dns/transport_base.go

@@ -0,0 +1,46 @@
+package dns
+
+import (
+	"context"
+	"net/netip"
+	"os"
+	"sync"
+
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/log"
+)
+
+type myTransportAdapter struct {
+	ctx         context.Context
+	dialer      N.Dialer
+	logger      log.Logger
+	destination M.Socksaddr
+	done        chan struct{}
+	access      sync.RWMutex
+	connection  *dnsConnection
+}
+
+func (t *myTransportAdapter) Start() error {
+	return nil
+}
+
+func (t *myTransportAdapter) Close() error {
+	select {
+	case <-t.done:
+		return os.ErrClosed
+	default:
+	}
+	close(t.done)
+	return nil
+}
+
+func (t *myTransportAdapter) Raw() bool {
+	return true
+}
+
+func (t *myTransportAdapter) Lookup(ctx context.Context, domain string, strategy C.DomainStrategy) ([]netip.Addr, error) {
+	return nil, os.ErrInvalid
+}

dns/transport_https.go

@@ -13,6 +13,7 @@ import (
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
 
+	"github.com/sagernet/sing-box/adapter"
 	C "github.com/sagernet/sing-box/constant"
 
 	"golang.org/x/net/dns/dnsmessage"
@@ -20,7 +21,7 @@ import (
 
 const dnsMimeType = "application/dns-message"
 
-var _ Transport = (*HTTPSTransport)(nil)
+var _ adapter.DNSTransport = (*HTTPSTransport)(nil)
 
 type HTTPSTransport struct {
 	destination string

dns/transport_local.go

@@ -9,21 +9,22 @@ import (
 
 	"github.com/sagernet/sing/common"
 
+	"github.com/sagernet/sing-box/adapter"
 	C "github.com/sagernet/sing-box/constant"
 
 	"golang.org/x/net/dns/dnsmessage"
 )
 
-var LocalTransportConstructor func() Transport
+var LocalTransportConstructor func() adapter.DNSTransport
 
-func NewLocalTransport() Transport {
+func NewLocalTransport() adapter.DNSTransport {
 	if LocalTransportConstructor != nil {
 		return LocalTransportConstructor()
 	}
 	return &LocalTransport{}
 }
 
-var _ Transport = (*LocalTransport)(nil)
+var _ adapter.DNSTransport = (*LocalTransport)(nil)
 
 type LocalTransport struct {
 	resolver net.Resolver

dns/transport_tcp.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"encoding/binary"
 	"net"
-	"net/netip"
 	"os"
 	"sync"
 
@@ -15,52 +14,30 @@ import (
 	N "github.com/sagernet/sing/common/network"
 	"github.com/sagernet/sing/common/task"
 
-	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/log"
 
 	"golang.org/x/net/dns/dnsmessage"
 )
 
-var _ Transport = (*TCPTransport)(nil)
+var _ adapter.DNSTransport = (*TCPTransport)(nil)
 
 type TCPTransport struct {
-	ctx         context.Context
-	dialer      N.Dialer
-	logger      log.Logger
-	destination M.Socksaddr
-	done        chan struct{}
-	access      sync.RWMutex
-	connection  *dnsConnection
+	myTransportAdapter
 }
 
 func NewTCPTransport(ctx context.Context, dialer N.Dialer, logger log.Logger, destination M.Socksaddr) *TCPTransport {
 	return &TCPTransport{
-		ctx:         ctx,
-		dialer:      dialer,
-		logger:      logger,
-		destination: destination,
-		done:        make(chan struct{}),
+		myTransportAdapter{
+			ctx:         ctx,
+			dialer:      dialer,
+			logger:      logger,
+			destination: destination,
+			done:        make(chan struct{}),
+		},
 	}
 }
 
-func (t *TCPTransport) Start() error {
-	return nil
-}
-
-func (t *TCPTransport) Close() error {
-	select {
-	case <-t.done:
-		return os.ErrClosed
-	default:
-	}
-	close(t.done)
-	return nil
-}
-
-func (t *TCPTransport) Raw() bool {
-	return true
-}
-
 func (t *TCPTransport) offer() (*dnsConnection, error) {
 	t.access.RLock()
 	connection := t.connection
@@ -207,7 +184,3 @@ func (t *TCPTransport) Exchange(ctx context.Context, message *dnsmessage.Message
 		return nil, ctx.Err()
 	}
 }
-
-func (t *TCPTransport) Lookup(ctx context.Context, domain string, strategy C.DomainStrategy) ([]netip.Addr, error) {
-	return nil, os.ErrInvalid
-}

dns/transport_tls.go

@@ -4,9 +4,7 @@ import (
 	"context"
 	"crypto/tls"
 	"encoding/binary"
-	"net/netip"
 	"os"
-	"sync"
 
 	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/buf"
@@ -15,52 +13,30 @@ import (
 	N "github.com/sagernet/sing/common/network"
 	"github.com/sagernet/sing/common/task"
 
-	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/log"
 
 	"golang.org/x/net/dns/dnsmessage"
 )
 
-var _ Transport = (*TLSTransport)(nil)
+var _ adapter.DNSTransport = (*TLSTransport)(nil)
 
 type TLSTransport struct {
-	ctx         context.Context
-	dialer      N.Dialer
-	logger      log.Logger
-	destination M.Socksaddr
-	done        chan struct{}
-	access      sync.RWMutex
-	connection  *dnsConnection
+	myTransportAdapter
 }
 
 func NewTLSTransport(ctx context.Context, dialer N.Dialer, logger log.Logger, destination M.Socksaddr) *TLSTransport {
 	return &TLSTransport{
-		ctx:         ctx,
-		dialer:      dialer,
-		logger:      logger,
-		destination: destination,
-		done:        make(chan struct{}),
+		myTransportAdapter{
+			ctx:         ctx,
+			dialer:      dialer,
+			logger:      logger,
+			destination: destination,
+			done:        make(chan struct{}),
+		},
 	}
 }
 
-func (t *TLSTransport) Start() error {
-	return nil
-}
-
-func (t *TLSTransport) Close() error {
-	select {
-	case <-t.done:
-		return os.ErrClosed
-	default:
-	}
-	close(t.done)
-	return nil
-}
-
-func (t *TLSTransport) Raw() bool {
-	return true
-}
-
 func (t *TLSTransport) offer(ctx context.Context) (*dnsConnection, error) {
 	t.access.RLock()
 	connection := t.connection
@@ -207,7 +183,3 @@ func (t *TLSTransport) Exchange(ctx context.Context, message *dnsmessage.Message
 		return nil, ctx.Err()
 	}
 }
-
-func (t *TLSTransport) Lookup(ctx context.Context, domain string, strategy C.DomainStrategy) ([]netip.Addr, error) {
-	return nil, os.ErrInvalid
-}

dns/transport_udp.go

@@ -2,9 +2,7 @@ package dns
 
 import (
 	"context"
-	"net/netip"
 	"os"
-	"sync"
 
 	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/buf"
@@ -12,52 +10,30 @@ import (
 	N "github.com/sagernet/sing/common/network"
 	"github.com/sagernet/sing/common/task"
 
-	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/log"
 
 	"golang.org/x/net/dns/dnsmessage"
 )
 
-var _ Transport = (*UDPTransport)(nil)
+var _ adapter.DNSTransport = (*UDPTransport)(nil)
 
 type UDPTransport struct {
-	ctx         context.Context
-	dialer      N.Dialer
-	logger      log.Logger
-	destination M.Socksaddr
-	done        chan struct{}
-	access      sync.RWMutex
-	connection  *dnsConnection
+	myTransportAdapter
 }
 
 func NewUDPTransport(ctx context.Context, dialer N.Dialer, logger log.Logger, destination M.Socksaddr) *UDPTransport {
 	return &UDPTransport{
-		ctx:         ctx,
-		dialer:      dialer,
-		logger:      logger,
-		destination: destination,
-		done:        make(chan struct{}),
+		myTransportAdapter{
+			ctx:         ctx,
+			dialer:      dialer,
+			logger:      logger,
+			destination: destination,
+			done:        make(chan struct{}),
+		},
 	}
 }
 
-func (t *UDPTransport) Start() error {
-	return nil
-}
-
-func (t *UDPTransport) Close() error {
-	select {
-	case <-t.done:
-		return os.ErrClosed
-	default:
-	}
-	close(t.done)
-	return nil
-}
-
-func (t *UDPTransport) Raw() bool {
-	return true
-}
-
 func (t *UDPTransport) offer() (*dnsConnection, error) {
 	t.access.RLock()
 	connection := t.connection
@@ -184,7 +160,3 @@ func (t *UDPTransport) Exchange(ctx context.Context, message *dnsmessage.Message
 		return nil, ctx.Err()
 	}
 }
-
-func (t *UDPTransport) Lookup(ctx context.Context, domain string, strategy C.DomainStrategy) ([]netip.Addr, error) {
-	return nil, os.ErrInvalid
-}