Treat requests with OPT extra but no options as simple requests

dns/client.go

@@ -2,12 +2,14 @@ package dns
 
 import (
 	"context"
+	"errors"
 	"net"
 	"net/netip"
 	"strings"
 	"time"
 
 	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/compatible"
 	C "github.com/sagernet/sing-box/constant"
 	"github.com/sagernet/sing/common"
 	E "github.com/sagernet/sing/common/exceptions"
@@ -17,7 +19,7 @@ import (
 	"github.com/sagernet/sing/contrab/freelru"
 	"github.com/sagernet/sing/contrab/maphash"
 
-	dns "github.com/miekg/dns"
+	"github.com/miekg/dns"
 )
 
 var (
@@ -39,7 +41,9 @@ type Client struct {
 	initRDRCFunc       func() adapter.RDRCStore
 	logger             logger.ContextLogger
 	cache              freelru.Cache[dns.Question, *dns.Msg]
+	cacheLock          compatible.Map[dns.Question, chan struct{}]
 	transportCache     freelru.Cache[transportCacheKey, *dns.Msg]
+	transportCacheLock compatible.Map[dns.Question, chan struct{}]
 }
 
 type ClientOptions struct {
@@ -96,17 +100,15 @@ func (c *Client) Exchange(ctx context.Context, transport adapter.DNSTransport, m
 		if c.logger != nil {
 			c.logger.WarnContext(ctx, "bad question size: ", len(message.Question))
 		}
-		responseMessage := dns.Msg{
-			MsgHdr: dns.MsgHdr{
-				Id:       message.Id,
-				Response: true,
-				Rcode:    dns.RcodeFormatError,
-			},
-			Question: message.Question,
-		}
-		return &responseMessage, nil
+		return FixedResponseStatus(message, dns.RcodeFormatError), nil
 	}
 	question := message.Question[0]
+	if question.Qtype == dns.TypeA && options.Strategy == C.DomainStrategyIPv6Only || question.Qtype == dns.TypeAAAA && options.Strategy == C.DomainStrategyIPv4Only {
+		if c.logger != nil {
+			c.logger.DebugContext(ctx, "strategy rejected")
+		}
+		return FixedResponseStatus(message, dns.RcodeSuccess), nil
+	}
 	clientSubnet := options.ClientSubnet
 	if !clientSubnet.IsValid() {
 		clientSubnet = c.clientSubnet
@@ -114,12 +116,38 @@ func (c *Client) Exchange(ctx context.Context, transport adapter.DNSTransport, m
 	if clientSubnet.IsValid() {
 		message = SetClientSubnet(message, clientSubnet)
 	}
+
 	isSimpleRequest := len(message.Question) == 1 &&
 		len(message.Ns) == 0 &&
-		len(message.Extra) == 0 &&
+		(len(message.Extra) == 0 || len(message.Extra) == 1 &&
+			message.Extra[0].Header().Rrtype == dns.TypeOPT &&
+			message.Extra[0].Header().Class > 0 &&
+			message.Extra[0].Header().Ttl == 0 &&
+			len(message.Extra[0].(*dns.OPT).Option) == 0) &&
 		!options.ClientSubnet.IsValid()
 	disableCache := !isSimpleRequest || c.disableCache || options.DisableCache
 	if !disableCache {
+		if c.cache != nil {
+			cond, loaded := c.cacheLock.LoadOrStore(question, make(chan struct{}))
+			if loaded {
+				<-cond
+			} else {
+				defer func() {
+					c.cacheLock.Delete(question)
+					close(cond)
+				}()
+			}
+		} else if c.transportCache != nil {
+			cond, loaded := c.transportCacheLock.LoadOrStore(question, make(chan struct{}))
+			if loaded {
+				<-cond
+			} else {
+				defer func() {
+					c.transportCacheLock.Delete(question)
+					close(cond)
+				}()
+			}
+		}
 		response, ttl := c.loadResponse(question, transport)
 		if response != nil {
 			logCachedResponse(c.logger, ctx, response, ttl)
@@ -127,27 +155,14 @@ func (c *Client) Exchange(ctx context.Context, transport adapter.DNSTransport, m
 			return response, nil
 		}
 	}
-	if question.Qtype == dns.TypeA && options.Strategy == C.DomainStrategyIPv6Only || question.Qtype == dns.TypeAAAA && options.Strategy == C.DomainStrategyIPv4Only {
-		responseMessage := dns.Msg{
-			MsgHdr: dns.MsgHdr{
-				Id:       message.Id,
-				Response: true,
-				Rcode:    dns.RcodeSuccess,
-			},
-			Question: []dns.Question{question},
-		}
-		if c.logger != nil {
-			c.logger.DebugContext(ctx, "strategy rejected")
-		}
-		return &responseMessage, nil
-	}
+
 	messageId := message.Id
 	contextTransport, clientSubnetLoaded := transportTagFromContext(ctx)
 	if clientSubnetLoaded && transport.Tag() == contextTransport {
 		return nil, E.New("DNS query loopback in transport[", contextTransport, "]")
 	}
 	ctx = contextWithTransportTag(ctx, transport.Tag())
-	if responseChecker != nil && c.rdrc != nil {
+	if !disableCache && responseChecker != nil && c.rdrc != nil {
 		rejected := c.rdrc.LoadRDRC(transport.Tag(), question.Name, question.Qtype)
 		if rejected {
 			return nil, ErrResponseRejectedCached
@@ -157,8 +172,13 @@ func (c *Client) Exchange(ctx context.Context, transport adapter.DNSTransport, m
 	response, err := transport.Exchange(ctx, message)
 	cancel()
 	if err != nil {
+		var rcodeError RcodeError
+		if errors.As(err, &rcodeError) {
+			response = FixedResponseStatus(message, int(rcodeError))
+		} else {
 			return nil, err
 		}
+	}
 	/*if question.Qtype == dns.TypeA || question.Qtype == dns.TypeAAAA {
 		validResponse := response
 	loop:
@@ -196,13 +216,14 @@ func (c *Client) Exchange(ctx context.Context, transport adapter.DNSTransport, m
 	}*/
 	if responseChecker != nil {
 		var rejected bool
-		if !(response.Rcode == dns.RcodeSuccess || response.Rcode == dns.RcodeNameError) {
+		// TODO: add accept_any rule and support to check response instead of addresses
+		if response.Rcode != dns.RcodeSuccess || len(response.Answer) == 0 {
 			rejected = true
 		} else {
 			rejected = !responseChecker(MessageToAddresses(response))
 		}
 		if rejected {
-			if c.rdrc != nil {
+			if !disableCache && c.rdrc != nil {
 				c.rdrc.SaveRDRCAsync(transport.Tag(), question.Name, question.Qtype, c.logger)
 			}
 			logRejectedResponse(c.logger, ctx, response)
@@ -305,8 +326,7 @@ func (c *Client) Lookup(ctx context.Context, transport adapter.DNSTransport, dom
 func (c *Client) ClearCache() {
 	if c.cache != nil {
 		c.cache.Purge()
-	}
-	if c.transportCache != nil {
+	} else if c.transportCache != nil {
 		c.transportCache.Purge()
 	}
 }
@@ -320,36 +340,36 @@ func (c *Client) LookupCache(domain string, strategy C.DomainStrategy) ([]netip.
 	}
 	dnsName := dns.Fqdn(domain)
 	if strategy == C.DomainStrategyIPv4Only {
-		response, err := c.questionCache(dns.Question{
+		addresses, err := c.questionCache(dns.Question{
 			Name:   dnsName,
 			Qtype:  dns.TypeA,
 			Qclass: dns.ClassINET,
 		}, nil)
 		if err != ErrNotCached {
-			return response, true
+			return addresses, true
 		}
 	} else if strategy == C.DomainStrategyIPv6Only {
-		response, err := c.questionCache(dns.Question{
+		addresses, err := c.questionCache(dns.Question{
 			Name:   dnsName,
 			Qtype:  dns.TypeAAAA,
 			Qclass: dns.ClassINET,
 		}, nil)
 		if err != ErrNotCached {
-			return response, true
+			return addresses, true
 		}
 	} else {
-		response4, _ := c.questionCache(dns.Question{
+		response4, _ := c.loadResponse(dns.Question{
 			Name:   dnsName,
 			Qtype:  dns.TypeA,
 			Qclass: dns.ClassINET,
 		}, nil)
-		response6, _ := c.questionCache(dns.Question{
+		response6, _ := c.loadResponse(dns.Question{
 			Name:   dnsName,
 			Qtype:  dns.TypeAAAA,
 			Qclass: dns.ClassINET,
 		}, nil)
-		if len(response4) > 0 || len(response6) > 0 {
-			return sortAddresses(response4, response6, strategy), true
+		if response4 != nil || response6 != nil {
+			return sortAddresses(MessageToAddresses(response4), MessageToAddresses(response6), strategy), true
 		}
 	}
 	return nil, false
@@ -390,8 +410,7 @@ func (c *Client) storeCache(transport adapter.DNSTransport, question dns.Questio
 				transportTag: transport.Tag(),
 			}, message)
 		}
-		return
-	}
+	} else {
 		if !c.independentCache {
 			c.cache.AddWithLifetime(question, message, time.Second*time.Duration(timeToLive))
 		} else {
@@ -401,6 +420,7 @@ func (c *Client) storeCache(transport adapter.DNSTransport, question dns.Questio
 			}, message, time.Second*time.Duration(timeToLive))
 		}
 	}
+}
 
 func (c *Client) lookupToExchange(ctx context.Context, transport adapter.DNSTransport, name string, qType uint16, options adapter.DNSQueryOptions, responseChecker func(responseAddrs []netip.Addr) bool) ([]netip.Addr, error) {
 	question := dns.Question{
@@ -517,6 +537,9 @@ func (c *Client) loadResponse(question dns.Question, transport adapter.DNSTransp
 }
 
 func MessageToAddresses(response *dns.Msg) []netip.Addr {
+	if response == nil || response.Rcode != dns.RcodeSuccess {
+		return nil
+	}
 	addresses := make([]netip.Addr, 0, len(response.Answer))
 	for _, rawAnswer := range response.Answer {
 		switch answer := rawAnswer.(type) {
@@ -562,8 +585,11 @@ func FixedResponseStatus(message *dns.Msg, rcode int) *dns.Msg {
 	return &dns.Msg{
 		MsgHdr: dns.MsgHdr{
 			Id:                 message.Id,
-			Rcode:    rcode,
 			Response:           true,
+			Authoritative:      true,
+			RecursionDesired:   true,
+			RecursionAvailable: true,
+			Rcode:              rcode,
 		},
 		Question: message.Question,
 	}

dns/transport/dhcp/dhcp_shared.go

@@ -16,11 +16,6 @@ import (
 	mDNS "github.com/miekg/dns"
 )
 
-const (
-	// net.maxDNSPacketSize
-	maxDNSPacketSize = 1232
-)
-
 func (t *Transport) exchangeSingleRequest(ctx context.Context, servers []M.Socksaddr, message *mDNS.Msg, domain string) (*mDNS.Msg, error) {
 	var lastErr error
 	for _, fqdn := range t.nameList(domain) {
@@ -118,7 +113,7 @@ func (t *Transport) exchangeOne(ctx context.Context, server M.Socksaddr, questio
 		Question: []mDNS.Question{question},
 		Compress: true,
 	}
-	request.SetEdns0(maxDNSPacketSize, false)
+	request.SetEdns0(buf.UDPBufferSize, false)
 	buffer := buf.Get(buf.UDPBufferSize)
 	defer buf.Put(buffer)
 	for _, network := range networks {

dns/transport/local/local.go

@@ -2,7 +2,9 @@ package local
 
 import (
 	"context"
+	"errors"
 	"math/rand"
+	"syscall"
 	"time"
 
 	"github.com/sagernet/sing-box/adapter"
@@ -164,7 +166,7 @@ func (t *Transport) exchangeOne(ctx context.Context, server M.Socksaddr, questio
 		Question: []mDNS.Question{question},
 		Compress: true,
 	}
-	request.SetEdns0(maxDNSPacketSize, false)
+	request.SetEdns0(buf.UDPBufferSize, false)
 	buffer := buf.Get(buf.UDPBufferSize)
 	defer buf.Put(buffer)
 	for _, network := range networks {
@@ -184,6 +186,9 @@ func (t *Transport) exchangeOne(ctx context.Context, server M.Socksaddr, questio
 		}
 		_, err = conn.Write(rawMessage)
 		if err != nil {
+			if errors.Is(err, syscall.EMSGSIZE) && network == N.NetworkUDP {
+				continue
+			}
 			return nil, E.Cause(err, "write request")
 		}
 		n, err := conn.Read(buffer)

dns/transport/local/resolv.go

@@ -10,11 +10,6 @@ import (
 	"time"
 )
 
-const (
-	// net.maxDNSPacketSize
-	maxDNSPacketSize = 1232
-)
-
 type resolverConfig struct {
 	initOnce    sync.Once
 	ch          chan struct{}

dns/transport_dialer.go

@@ -19,7 +19,6 @@ func NewLocalDialer(ctx context.Context, options option.LocalDNSServerOptions) (
 	if options.LegacyDefaultDialer {
 		return dialer.NewDefaultOutbound(ctx), nil
 	} else {
-		options.UDPFragmentDefault = true
 		return dialer.NewWithOptions(dialer.Options{
 			Context:         ctx,
 			Options:         options.DialerOptions,

experimental/clashapi/trafficontrol/manager.go

@@ -6,8 +6,8 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/sagernet/sing-box/common/compatible"
 	C "github.com/sagernet/sing-box/constant"
-	"github.com/sagernet/sing-box/experimental/clashapi/compatible"
 	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/json"
 	"github.com/sagernet/sing/common/x/list"