refactor: DNS

dns/client.go

@@ -0,0 +1,563 @@
+package dns
+
+import (
+	"context"
+	"net"
+	"net/netip"
+	"strings"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing/common"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	"github.com/sagernet/sing/common/task"
+	"github.com/sagernet/sing/contrab/freelru"
+	"github.com/sagernet/sing/contrab/maphash"
+
+	"github.com/miekg/dns"
+)
+
+var (
+	ErrNoRawSupport           = E.New("no raw query support by current transport")
+	ErrNotCached              = E.New("not cached")
+	ErrResponseRejected       = E.New("response rejected")
+	ErrResponseRejectedCached = E.Extend(ErrResponseRejected, "cached")
+)
+
+var _ adapter.DNSClient = (*Client)(nil)
+
+type Client struct {
+	timeout          time.Duration
+	disableCache     bool
+	disableExpire    bool
+	independentCache bool
+	rdrc             adapter.RDRCStore
+	initRDRCFunc     func() adapter.RDRCStore
+	logger           logger.ContextLogger
+	cache            freelru.Cache[dns.Question, *dns.Msg]
+	transportCache   freelru.Cache[transportCacheKey, *dns.Msg]
+}
+
+type ClientOptions struct {
+	Timeout          time.Duration
+	DisableCache     bool
+	DisableExpire    bool
+	IndependentCache bool
+	CacheCapacity    uint32
+	RDRC             func() adapter.RDRCStore
+	Logger           logger.ContextLogger
+}
+
+func NewClient(options ClientOptions) *Client {
+	client := &Client{
+		timeout:          options.Timeout,
+		disableCache:     options.DisableCache,
+		disableExpire:    options.DisableExpire,
+		independentCache: options.IndependentCache,
+		initRDRCFunc:     options.RDRC,
+		logger:           options.Logger,
+	}
+	if client.timeout == 0 {
+		client.timeout = C.DNSTimeout
+	}
+	cacheCapacity := options.CacheCapacity
+	if cacheCapacity < 1024 {
+		cacheCapacity = 1024
+	}
+	if !client.disableCache {
+		if !client.independentCache {
+			client.cache = common.Must1(freelru.NewSharded[dns.Question, *dns.Msg](cacheCapacity, maphash.NewHasher[dns.Question]().Hash32))
+		} else {
+			client.transportCache = common.Must1(freelru.NewSharded[transportCacheKey, *dns.Msg](cacheCapacity, maphash.NewHasher[transportCacheKey]().Hash32))
+		}
+	}
+	return client
+}
+
+type transportCacheKey struct {
+	dns.Question
+	transportTag string
+}
+
+func (c *Client) Start() {
+	if c.initRDRCFunc != nil {
+		c.rdrc = c.initRDRCFunc()
+	}
+}
+
+func (c *Client) Exchange(ctx context.Context, transport adapter.DNSTransport, message *dns.Msg, options adapter.DNSQueryOptions, responseChecker func(responseAddrs []netip.Addr) bool) (*dns.Msg, error) {
+	if len(message.Question) == 0 {
+		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
+	}
+	question := message.Question[0]
+	if options.ClientSubnet.IsValid() {
+		message = SetClientSubnet(message, options.ClientSubnet, true)
+	}
+	isSimpleRequest := len(message.Question) == 1 &&
+		len(message.Ns) == 0 &&
+		len(message.Extra) == 0 &&
+		!options.ClientSubnet.IsValid()
+	disableCache := !isSimpleRequest || c.disableCache || options.DisableCache
+	if !disableCache {
+		response, ttl := c.loadResponse(question, transport)
+		if response != nil {
+			logCachedResponse(c.logger, ctx, response, ttl)
+			response.Id = message.Id
+			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 {
+		rejected := c.rdrc.LoadRDRC(transport.Tag(), question.Name, question.Qtype)
+		if rejected {
+			return nil, ErrResponseRejectedCached
+		}
+	}
+	ctx, cancel := context.WithTimeout(ctx, c.timeout)
+	response, err := transport.Exchange(ctx, message)
+	cancel()
+	if err != nil {
+		return nil, err
+	}
+	/*if question.Qtype == dns.TypeA || question.Qtype == dns.TypeAAAA {
+		validResponse := response
+	loop:
+		for {
+			var (
+				addresses  int
+				queryCNAME string
+			)
+			for _, rawRR := range validResponse.Answer {
+				switch rr := rawRR.(type) {
+				case *dns.A:
+					break loop
+				case *dns.AAAA:
+					break loop
+				case *dns.CNAME:
+					queryCNAME = rr.Target
+				}
+			}
+			if queryCNAME == "" {
+				break
+			}
+			exMessage := *message
+			exMessage.Question = []dns.Question{{
+				Name:  queryCNAME,
+				Qtype: question.Qtype,
+			}}
+			validResponse, err = c.Exchange(ctx, transport, &exMessage, options, responseChecker)
+			if err != nil {
+				return nil, err
+			}
+		}
+		if validResponse != response {
+			response.Answer = append(response.Answer, validResponse.Answer...)
+		}
+	}*/
+	if responseChecker != nil {
+		addr, addrErr := MessageToAddresses(response)
+		if addrErr != nil || !responseChecker(addr) {
+			if c.rdrc != nil {
+				c.rdrc.SaveRDRCAsync(transport.Tag(), question.Name, question.Qtype, c.logger)
+			}
+			logRejectedResponse(c.logger, ctx, response)
+			return response, ErrResponseRejected
+		}
+	}
+	if question.Qtype == dns.TypeHTTPS {
+		if options.Strategy == C.DomainStrategyIPv4Only || options.Strategy == C.DomainStrategyIPv6Only {
+			for _, rr := range response.Answer {
+				https, isHTTPS := rr.(*dns.HTTPS)
+				if !isHTTPS {
+					continue
+				}
+				content := https.SVCB
+				content.Value = common.Filter(content.Value, func(it dns.SVCBKeyValue) bool {
+					if options.Strategy == C.DomainStrategyIPv4Only {
+						return it.Key() != dns.SVCB_IPV6HINT
+					} else {
+						return it.Key() != dns.SVCB_IPV4HINT
+					}
+				})
+				https.SVCB = content
+			}
+		}
+	}
+	var timeToLive uint32
+	for _, recordList := range [][]dns.RR{response.Answer, response.Ns, response.Extra} {
+		for _, record := range recordList {
+			if timeToLive == 0 || record.Header().Ttl > 0 && record.Header().Ttl < timeToLive {
+				timeToLive = record.Header().Ttl
+			}
+		}
+	}
+	if options.RewriteTTL != nil {
+		timeToLive = *options.RewriteTTL
+	}
+	for _, recordList := range [][]dns.RR{response.Answer, response.Ns, response.Extra} {
+		for _, record := range recordList {
+			record.Header().Ttl = timeToLive
+		}
+	}
+	response.Id = messageId
+	if !disableCache {
+		c.storeCache(transport, question, response, timeToLive)
+	}
+	logExchangedResponse(c.logger, ctx, response, timeToLive)
+	return response, err
+}
+
+func (c *Client) Lookup(ctx context.Context, transport adapter.DNSTransport, domain string, options adapter.DNSQueryOptions, responseChecker func(responseAddrs []netip.Addr) bool) ([]netip.Addr, error) {
+	domain = FqdnToDomain(domain)
+	dnsName := dns.Fqdn(domain)
+	if options.Strategy == C.DomainStrategyIPv4Only {
+		return c.lookupToExchange(ctx, transport, dnsName, dns.TypeA, options, responseChecker)
+	} else if options.Strategy == C.DomainStrategyIPv6Only {
+		return c.lookupToExchange(ctx, transport, dnsName, dns.TypeAAAA, options, responseChecker)
+	}
+	var response4 []netip.Addr
+	var response6 []netip.Addr
+	var group task.Group
+	group.Append("exchange4", func(ctx context.Context) error {
+		response, err := c.lookupToExchange(ctx, transport, dnsName, dns.TypeA, options, responseChecker)
+		if err != nil {
+			return err
+		}
+		response4 = response
+		return nil
+	})
+	group.Append("exchange6", func(ctx context.Context) error {
+		response, err := c.lookupToExchange(ctx, transport, dnsName, dns.TypeAAAA, options, responseChecker)
+		if err != nil {
+			return err
+		}
+		response6 = response
+		return nil
+	})
+	err := group.Run(ctx)
+	if len(response4) == 0 && len(response6) == 0 {
+		return nil, err
+	}
+	return sortAddresses(response4, response6, options.Strategy), nil
+}
+
+func (c *Client) ClearCache() {
+	if c.cache != nil {
+		c.cache.Purge()
+	}
+	if c.transportCache != nil {
+		c.transportCache.Purge()
+	}
+}
+
+func (c *Client) LookupCache(domain string, strategy C.DomainStrategy) ([]netip.Addr, bool) {
+	if c.disableCache || c.independentCache {
+		return nil, false
+	}
+	if dns.IsFqdn(domain) {
+		domain = domain[:len(domain)-1]
+	}
+	dnsName := dns.Fqdn(domain)
+	if strategy == C.DomainStrategyIPv4Only {
+		response, err := c.questionCache(dns.Question{
+			Name:   dnsName,
+			Qtype:  dns.TypeA,
+			Qclass: dns.ClassINET,
+		}, nil)
+		if err != ErrNotCached {
+			return response, true
+		}
+	} else if strategy == C.DomainStrategyIPv6Only {
+		response, err := c.questionCache(dns.Question{
+			Name:   dnsName,
+			Qtype:  dns.TypeAAAA,
+			Qclass: dns.ClassINET,
+		}, nil)
+		if err != ErrNotCached {
+			return response, true
+		}
+	} else {
+		response4, _ := c.questionCache(dns.Question{
+			Name:   dnsName,
+			Qtype:  dns.TypeA,
+			Qclass: dns.ClassINET,
+		}, nil)
+		response6, _ := c.questionCache(dns.Question{
+			Name:   dnsName,
+			Qtype:  dns.TypeAAAA,
+			Qclass: dns.ClassINET,
+		}, nil)
+		if len(response4) > 0 || len(response6) > 0 {
+			return sortAddresses(response4, response6, strategy), true
+		}
+	}
+	return nil, false
+}
+
+func (c *Client) ExchangeCache(ctx context.Context, message *dns.Msg) (*dns.Msg, bool) {
+	if c.disableCache || c.independentCache || len(message.Question) != 1 {
+		return nil, false
+	}
+	question := message.Question[0]
+	response, ttl := c.loadResponse(question, nil)
+	if response == nil {
+		return nil, false
+	}
+	logCachedResponse(c.logger, ctx, response, ttl)
+	response.Id = message.Id
+	return response, true
+}
+
+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 (c *Client) storeCache(transport adapter.DNSTransport, question dns.Question, message *dns.Msg, timeToLive uint32) {
+	if timeToLive == 0 {
+		return
+	}
+	if c.disableExpire {
+		if !c.independentCache {
+			c.cache.Add(question, message)
+		} else {
+			c.transportCache.Add(transportCacheKey{
+				Question:     question,
+				transportTag: transport.Tag(),
+			}, message)
+		}
+		return
+	}
+	if !c.independentCache {
+		c.cache.AddWithLifetime(question, message, time.Second*time.Duration(timeToLive))
+	} else {
+		c.transportCache.AddWithLifetime(transportCacheKey{
+			Question:     question,
+			transportTag: transport.Tag(),
+		}, 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{
+		Name:   name,
+		Qtype:  qType,
+		Qclass: dns.ClassINET,
+	}
+	disableCache := c.disableCache || options.DisableCache
+	if !disableCache {
+		cachedAddresses, err := c.questionCache(question, transport)
+		if err != ErrNotCached {
+			return cachedAddresses, err
+		}
+	}
+	message := dns.Msg{
+		MsgHdr: dns.MsgHdr{
+			RecursionDesired: true,
+		},
+		Question: []dns.Question{question},
+	}
+	response, err := c.Exchange(ctx, transport, &message, options, responseChecker)
+	if err != nil {
+		return nil, err
+	}
+	return MessageToAddresses(response)
+}
+
+func (c *Client) questionCache(question dns.Question, transport adapter.DNSTransport) ([]netip.Addr, error) {
+	response, _ := c.loadResponse(question, transport)
+	if response == nil {
+		return nil, ErrNotCached
+	}
+	return MessageToAddresses(response)
+}
+
+func (c *Client) loadResponse(question dns.Question, transport adapter.DNSTransport) (*dns.Msg, int) {
+	var (
+		response *dns.Msg
+		loaded   bool
+	)
+	if c.disableExpire {
+		if !c.independentCache {
+			response, loaded = c.cache.Get(question)
+		} else {
+			response, loaded = c.transportCache.Get(transportCacheKey{
+				Question:     question,
+				transportTag: transport.Tag(),
+			})
+		}
+		if !loaded {
+			return nil, 0
+		}
+		return response.Copy(), 0
+	} else {
+		var expireAt time.Time
+		if !c.independentCache {
+			response, expireAt, loaded = c.cache.GetWithLifetime(question)
+		} else {
+			response, expireAt, loaded = c.transportCache.GetWithLifetime(transportCacheKey{
+				Question:     question,
+				transportTag: transport.Tag(),
+			})
+		}
+		if !loaded {
+			return nil, 0
+		}
+		timeNow := time.Now()
+		if timeNow.After(expireAt) {
+			if !c.independentCache {
+				c.cache.Remove(question)
+			} else {
+				c.transportCache.Remove(transportCacheKey{
+					Question:     question,
+					transportTag: transport.Tag(),
+				})
+			}
+			return nil, 0
+		}
+		var originTTL int
+		for _, recordList := range [][]dns.RR{response.Answer, response.Ns, response.Extra} {
+			for _, record := range recordList {
+				if originTTL == 0 || record.Header().Ttl > 0 && int(record.Header().Ttl) < originTTL {
+					originTTL = int(record.Header().Ttl)
+				}
+			}
+		}
+		nowTTL := int(expireAt.Sub(timeNow).Seconds())
+		if nowTTL < 0 {
+			nowTTL = 0
+		}
+		response = response.Copy()
+		if originTTL > 0 {
+			duration := uint32(originTTL - nowTTL)
+			for _, recordList := range [][]dns.RR{response.Answer, response.Ns, response.Extra} {
+				for _, record := range recordList {
+					record.Header().Ttl = record.Header().Ttl - duration
+				}
+			}
+		} else {
+			for _, recordList := range [][]dns.RR{response.Answer, response.Ns, response.Extra} {
+				for _, record := range recordList {
+					record.Header().Ttl = uint32(nowTTL)
+				}
+			}
+		}
+		return response, nowTTL
+	}
+}
+
+func MessageToAddresses(response *dns.Msg) ([]netip.Addr, error) {
+	if response.Rcode != dns.RcodeSuccess && response.Rcode != dns.RcodeNameError {
+		return nil, RCodeError(response.Rcode)
+	}
+	addresses := make([]netip.Addr, 0, len(response.Answer))
+	for _, rawAnswer := range response.Answer {
+		switch answer := rawAnswer.(type) {
+		case *dns.A:
+			addresses = append(addresses, M.AddrFromIP(answer.A))
+		case *dns.AAAA:
+			addresses = append(addresses, M.AddrFromIP(answer.AAAA))
+		case *dns.HTTPS:
+			for _, value := range answer.SVCB.Value {
+				if value.Key() == dns.SVCB_IPV4HINT || value.Key() == dns.SVCB_IPV6HINT {
+					addresses = append(addresses, common.Map(strings.Split(value.String(), ","), M.ParseAddr)...)
+				}
+			}
+		}
+	}
+	return addresses, nil
+}
+
+func wrapError(err error) error {
+	switch dnsErr := err.(type) {
+	case *net.DNSError:
+		if dnsErr.IsNotFound {
+			return RCodeNameError
+		}
+	case *net.AddrError:
+		return RCodeNameError
+	}
+	return err
+}
+
+type transportKey struct{}
+
+func contextWithTransportTag(ctx context.Context, transportTag string) context.Context {
+	return context.WithValue(ctx, transportKey{}, transportTag)
+}
+
+func transportTagFromContext(ctx context.Context) (string, bool) {
+	value, loaded := ctx.Value(transportKey{}).(string)
+	return value, loaded
+}
+
+func FixedResponse(id uint16, question dns.Question, addresses []netip.Addr, timeToLive uint32) *dns.Msg {
+	response := dns.Msg{
+		MsgHdr: dns.MsgHdr{
+			Id:       id,
+			Rcode:    dns.RcodeSuccess,
+			Response: true,
+		},
+		Question: []dns.Question{question},
+	}
+	for _, address := range addresses {
+		if address.Is4() {
+			response.Answer = append(response.Answer, &dns.A{
+				Hdr: dns.RR_Header{
+					Name:   question.Name,
+					Rrtype: dns.TypeA,
+					Class:  dns.ClassINET,
+					Ttl:    timeToLive,
+				},
+				A: address.AsSlice(),
+			})
+		} else {
+			response.Answer = append(response.Answer, &dns.AAAA{
+				Hdr: dns.RR_Header{
+					Name:   question.Name,
+					Rrtype: dns.TypeAAAA,
+					Class:  dns.ClassINET,
+					Ttl:    timeToLive,
+				},
+				AAAA: address.AsSlice(),
+			})
+		}
+	}
+	return &response
+}

dns/client_log.go

@@ -0,0 +1,69 @@
+package dns
+
+import (
+	"context"
+	"strings"
+
+	"github.com/sagernet/sing/common/logger"
+
+	"github.com/miekg/dns"
+)
+
+func logCachedResponse(logger logger.ContextLogger, ctx context.Context, response *dns.Msg, ttl int) {
+	if logger == nil || len(response.Question) == 0 {
+		return
+	}
+	domain := FqdnToDomain(response.Question[0].Name)
+	logger.DebugContext(ctx, "cached ", domain, " ", dns.RcodeToString[response.Rcode], " ", ttl)
+	for _, recordList := range [][]dns.RR{response.Answer, response.Ns, response.Extra} {
+		for _, record := range recordList {
+			logger.InfoContext(ctx, "cached ", dns.Type(record.Header().Rrtype).String(), " ", FormatQuestion(record.String()))
+		}
+	}
+}
+
+func logExchangedResponse(logger logger.ContextLogger, ctx context.Context, response *dns.Msg, ttl uint32) {
+	if logger == nil || len(response.Question) == 0 {
+		return
+	}
+	domain := FqdnToDomain(response.Question[0].Name)
+	logger.DebugContext(ctx, "exchanged ", domain, " ", dns.RcodeToString[response.Rcode], " ", ttl)
+	for _, recordList := range [][]dns.RR{response.Answer, response.Ns, response.Extra} {
+		for _, record := range recordList {
+			logger.InfoContext(ctx, "exchanged ", dns.Type(record.Header().Rrtype).String(), " ", FormatQuestion(record.String()))
+		}
+	}
+}
+
+func logRejectedResponse(logger logger.ContextLogger, ctx context.Context, response *dns.Msg) {
+	if logger == nil || len(response.Question) == 0 {
+		return
+	}
+	for _, recordList := range [][]dns.RR{response.Answer, response.Ns, response.Extra} {
+		for _, record := range recordList {
+			logger.InfoContext(ctx, "rejected ", dns.Type(record.Header().Rrtype).String(), " ", FormatQuestion(record.String()))
+		}
+	}
+}
+
+func FqdnToDomain(fqdn string) string {
+	if dns.IsFqdn(fqdn) {
+		return fqdn[:len(fqdn)-1]
+	}
+	return fqdn
+}
+
+func FormatQuestion(string string) string {
+	for strings.HasPrefix(string, ";") {
+		string = string[1:]
+	}
+	string = strings.ReplaceAll(string, "\t", " ")
+	string = strings.ReplaceAll(string, "\n", " ")
+	string = strings.ReplaceAll(string, ";; ", " ")
+	string = strings.ReplaceAll(string, "; ", " ")
+
+	for strings.Contains(string, "  ") {
+		string = strings.ReplaceAll(string, "  ", " ")
+	}
+	return strings.TrimSpace(string)
+}

dns/client_truncate.go

@@ -0,0 +1,31 @@
+package dns
+
+import (
+	"github.com/sagernet/sing/common/buf"
+
+	"github.com/miekg/dns"
+)
+
+func TruncateDNSMessage(request *dns.Msg, response *dns.Msg, headroom int) (*buf.Buffer, error) {
+	maxLen := 512
+	if edns0Option := request.IsEdns0(); edns0Option != nil {
+		if udpSize := int(edns0Option.UDPSize()); udpSize > 512 {
+			maxLen = udpSize
+		}
+	}
+	responseLen := response.Len()
+	if responseLen > maxLen {
+		copyResponse := *response
+		response = &copyResponse
+		response.Truncate(maxLen)
+	}
+	buffer := buf.NewSize(headroom*2 + 1 + responseLen)
+	buffer.Resize(headroom, 0)
+	rawMessage, err := response.PackBuffer(buffer.FreeBytes())
+	if err != nil {
+		buffer.Release()
+		return nil, err
+	}
+	buffer.Truncate(len(rawMessage))
+	return buffer, nil
+}

dns/extension_edns0_subnet.go

@@ -0,0 +1,56 @@
+package dns
+
+import (
+	"net/netip"
+
+	"github.com/miekg/dns"
+)
+
+func SetClientSubnet(message *dns.Msg, clientSubnet netip.Prefix, override bool) *dns.Msg {
+	var (
+		optRecord    *dns.OPT
+		subnetOption *dns.EDNS0_SUBNET
+	)
+findExists:
+	for _, record := range message.Extra {
+		var isOPTRecord bool
+		if optRecord, isOPTRecord = record.(*dns.OPT); isOPTRecord {
+			for _, option := range optRecord.Option {
+				var isEDNS0Subnet bool
+				subnetOption, isEDNS0Subnet = option.(*dns.EDNS0_SUBNET)
+				if isEDNS0Subnet {
+					if !override {
+						return message
+					}
+					break findExists
+				}
+			}
+		}
+	}
+	if optRecord == nil {
+		exMessage := *message
+		message = &exMessage
+		optRecord = &dns.OPT{
+			Hdr: dns.RR_Header{
+				Name:   ".",
+				Rrtype: dns.TypeOPT,
+			},
+		}
+		message.Extra = append(message.Extra, optRecord)
+	} else {
+		message = message.Copy()
+	}
+	if subnetOption == nil {
+		subnetOption = new(dns.EDNS0_SUBNET)
+		optRecord.Option = append(optRecord.Option, subnetOption)
+	}
+	subnetOption.Code = dns.EDNS0SUBNET
+	if clientSubnet.Addr().Is4() {
+		subnetOption.Family = 1
+	} else {
+		subnetOption.Family = 2
+	}
+	subnetOption.SourceNetmask = uint8(clientSubnet.Bits())
+	subnetOption.Address = clientSubnet.Addr().AsSlice()
+	return message
+}

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/router.go

@@ -0,0 +1,444 @@
+package dns
+
+import (
+	"context"
+	"errors"
+	"net/netip"
+	"strings"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/taskmonitor"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/experimental/libbox/platform"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	R "github.com/sagernet/sing-box/route/rule"
+	"github.com/sagernet/sing-tun"
+	"github.com/sagernet/sing/common"
+	E "github.com/sagernet/sing/common/exceptions"
+	F "github.com/sagernet/sing/common/format"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	"github.com/sagernet/sing/contrab/freelru"
+	"github.com/sagernet/sing/contrab/maphash"
+	"github.com/sagernet/sing/service"
+
+	mDNS "github.com/miekg/dns"
+)
+
+var _ adapter.DNSRouter = (*Router)(nil)
+
+type Router struct {
+	ctx                   context.Context
+	logger                logger.ContextLogger
+	transport             adapter.DNSTransportManager
+	outbound              adapter.OutboundManager
+	client                adapter.DNSClient
+	rules                 []adapter.DNSRule
+	defaultDomainStrategy C.DomainStrategy
+	dnsReverseMapping     freelru.Cache[netip.Addr, string]
+	platformInterface     platform.Interface
+}
+
+func NewRouter(ctx context.Context, logFactory log.Factory, options option.DNSOptions) *Router {
+	router := &Router{
+		ctx:                   ctx,
+		logger:                logFactory.NewLogger("dns"),
+		transport:             service.FromContext[adapter.DNSTransportManager](ctx),
+		outbound:              service.FromContext[adapter.OutboundManager](ctx),
+		rules:                 make([]adapter.DNSRule, 0, len(options.Rules)),
+		defaultDomainStrategy: C.DomainStrategy(options.Strategy),
+	}
+	router.client = NewClient(ClientOptions{
+		DisableCache:     options.DNSClientOptions.DisableCache,
+		DisableExpire:    options.DNSClientOptions.DisableExpire,
+		IndependentCache: options.DNSClientOptions.IndependentCache,
+		CacheCapacity:    options.DNSClientOptions.CacheCapacity,
+		RDRC: func() adapter.RDRCStore {
+			cacheFile := service.FromContext[adapter.CacheFile](ctx)
+			if cacheFile == nil {
+				return nil
+			}
+			if !cacheFile.StoreRDRC() {
+				return nil
+			}
+			return cacheFile
+		},
+		Logger: router.logger,
+	})
+	if options.ReverseMapping {
+		router.dnsReverseMapping = common.Must1(freelru.NewSharded[netip.Addr, string](1024, maphash.NewHasher[netip.Addr]().Hash32))
+	}
+	return router
+}
+
+func (r *Router) Initialize(rules []option.DNSRule) error {
+	for i, ruleOptions := range rules {
+		dnsRule, err := R.NewDNSRule(r.ctx, r.logger, ruleOptions, true)
+		if err != nil {
+			return E.Cause(err, "parse dns rule[", i, "]")
+		}
+		r.rules = append(r.rules, dnsRule)
+	}
+	return nil
+}
+
+func (r *Router) Start(stage adapter.StartStage) error {
+	monitor := taskmonitor.New(r.logger, C.StartTimeout)
+	switch stage {
+	case adapter.StartStateStart:
+		monitor.Start("initialize DNS client")
+		r.client.Start()
+		monitor.Finish()
+
+		for i, rule := range r.rules {
+			monitor.Start("initialize DNS rule[", i, "]")
+			err := rule.Start()
+			monitor.Finish()
+			if err != nil {
+				return E.Cause(err, "initialize DNS rule[", i, "]")
+			}
+		}
+	}
+	return nil
+}
+
+func (r *Router) Close() error {
+	monitor := taskmonitor.New(r.logger, C.StopTimeout)
+	var err error
+	for i, rule := range r.rules {
+		monitor.Start("close dns rule[", i, "]")
+		err = E.Append(err, rule.Close(), func(err error) error {
+			return E.Cause(err, "close dns rule[", i, "]")
+		})
+		monitor.Finish()
+	}
+	return err
+}
+
+func (r *Router) matchDNS(ctx context.Context, allowFakeIP bool, ruleIndex int, isAddressQuery bool, options *adapter.DNSQueryOptions) (adapter.DNSTransport, adapter.DNSRule, int) {
+	metadata := adapter.ContextFrom(ctx)
+	if metadata == nil {
+		panic("no context")
+	}
+	var currentRuleIndex int
+	if ruleIndex != -1 {
+		currentRuleIndex = ruleIndex + 1
+	}
+	for ; currentRuleIndex < len(r.rules); currentRuleIndex++ {
+		currentRule := r.rules[currentRuleIndex]
+		if currentRule.WithAddressLimit() && !isAddressQuery {
+			continue
+		}
+		metadata.ResetRuleCache()
+		if currentRule.Match(metadata) {
+			displayRuleIndex := currentRuleIndex
+			if displayRuleIndex != -1 {
+				displayRuleIndex += displayRuleIndex + 1
+			}
+			ruleDescription := currentRule.String()
+			if ruleDescription != "" {
+				r.logger.DebugContext(ctx, "match[", displayRuleIndex, "] ", currentRule, " => ", currentRule.Action())
+			} else {
+				r.logger.DebugContext(ctx, "match[", displayRuleIndex, "] => ", currentRule.Action())
+			}
+			switch action := currentRule.Action().(type) {
+			case *R.RuleActionDNSRoute:
+				transport, loaded := r.transport.Transport(action.Server)
+				if !loaded {
+					r.logger.ErrorContext(ctx, "transport not found: ", action.Server)
+					continue
+				}
+				isFakeIP := transport.Type() == C.DNSTypeFakeIP
+				if isFakeIP && !allowFakeIP {
+					continue
+				}
+				if action.Strategy != C.DomainStrategyAsIS {
+					options.Strategy = action.Strategy
+				}
+				if isFakeIP || action.DisableCache {
+					options.DisableCache = true
+				}
+				if action.RewriteTTL != nil {
+					options.RewriteTTL = action.RewriteTTL
+				}
+				if action.ClientSubnet.IsValid() {
+					options.ClientSubnet = action.ClientSubnet
+				}
+				if legacyTransport, isLegacy := transport.(adapter.LegacyDNSTransport); isLegacy {
+					if options.Strategy == C.DomainStrategyAsIS {
+						options.Strategy = legacyTransport.LegacyStrategy()
+					}
+					if !options.ClientSubnet.IsValid() {
+						options.ClientSubnet = legacyTransport.LegacyClientSubnet()
+					}
+				}
+				r.logger.DebugContext(ctx, "match[", displayRuleIndex, "] => ", currentRule.Action())
+				return transport, currentRule, currentRuleIndex
+			case *R.RuleActionDNSRouteOptions:
+				if action.Strategy != C.DomainStrategyAsIS {
+					options.Strategy = action.Strategy
+				}
+				if action.DisableCache {
+					options.DisableCache = true
+				}
+				if action.RewriteTTL != nil {
+					options.RewriteTTL = action.RewriteTTL
+				}
+				if action.ClientSubnet.IsValid() {
+					options.ClientSubnet = action.ClientSubnet
+				}
+				r.logger.DebugContext(ctx, "match[", displayRuleIndex, "] => ", currentRule.Action())
+			case *R.RuleActionReject:
+				r.logger.DebugContext(ctx, "match[", displayRuleIndex, "] => ", currentRule.Action())
+				return nil, currentRule, currentRuleIndex
+			}
+		}
+	}
+	return r.transport.Default(), nil, -1
+}
+
+func (r *Router) Exchange(ctx context.Context, message *mDNS.Msg, options adapter.DNSQueryOptions) (*mDNS.Msg, error) {
+	if len(message.Question) != 1 {
+		r.logger.WarnContext(ctx, "bad question size: ", len(message.Question))
+		responseMessage := mDNS.Msg{
+			MsgHdr: mDNS.MsgHdr{
+				Id:       message.Id,
+				Response: true,
+				Rcode:    mDNS.RcodeFormatError,
+			},
+			Question: message.Question,
+		}
+		return &responseMessage, nil
+	}
+	r.logger.DebugContext(ctx, "exchange ", FormatQuestion(message.Question[0].String()))
+	var (
+		transport adapter.DNSTransport
+		err       error
+	)
+	response, cached := r.client.ExchangeCache(ctx, message)
+	if !cached {
+		var metadata *adapter.InboundContext
+		ctx, metadata = adapter.ExtendContext(ctx)
+		metadata.Destination = M.Socksaddr{}
+		metadata.QueryType = message.Question[0].Qtype
+		switch metadata.QueryType {
+		case mDNS.TypeA:
+			metadata.IPVersion = 4
+		case mDNS.TypeAAAA:
+			metadata.IPVersion = 6
+		}
+		metadata.Domain = FqdnToDomain(message.Question[0].Name)
+		if options.Transport != nil {
+			transport = options.Transport
+			if legacyTransport, isLegacy := transport.(adapter.LegacyDNSTransport); isLegacy {
+				if options.Strategy == C.DomainStrategyAsIS {
+					options.Strategy = legacyTransport.LegacyStrategy()
+				}
+				if !options.ClientSubnet.IsValid() {
+					options.ClientSubnet = legacyTransport.LegacyClientSubnet()
+				}
+			}
+			if options.Strategy == C.DomainStrategyAsIS {
+				options.Strategy = r.defaultDomainStrategy
+			}
+			response, err = r.client.Exchange(ctx, transport, message, options, nil)
+		} else {
+			var (
+				rule      adapter.DNSRule
+				ruleIndex int
+			)
+			ruleIndex = -1
+			for {
+				dnsCtx := adapter.OverrideContext(ctx)
+				dnsOptions := options
+				transport, rule, ruleIndex = r.matchDNS(ctx, true, ruleIndex, isAddressQuery(message), &dnsOptions)
+				if rule != nil {
+					switch action := rule.Action().(type) {
+					case *R.RuleActionReject:
+						switch action.Method {
+						case C.RuleActionRejectMethodDefault:
+							return &mDNS.Msg{
+								MsgHdr: mDNS.MsgHdr{
+									Id:       message.Id,
+									Rcode:    mDNS.RcodeRefused,
+									Response: true,
+								},
+								Question: []mDNS.Question{message.Question[0]},
+							}, nil
+						case C.RuleActionRejectMethodDrop:
+							return nil, tun.ErrDrop
+						}
+					}
+				}
+				var responseCheck func(responseAddrs []netip.Addr) bool
+				if rule != nil && rule.WithAddressLimit() {
+					responseCheck = func(responseAddrs []netip.Addr) bool {
+						metadata.DestinationAddresses = responseAddrs
+						return rule.MatchAddressLimit(metadata)
+					}
+				}
+				if dnsOptions.Strategy == C.DomainStrategyAsIS {
+					dnsOptions.Strategy = r.defaultDomainStrategy
+				}
+				response, err = r.client.Exchange(dnsCtx, transport, message, dnsOptions, responseCheck)
+				var rejected bool
+				if err != nil {
+					if errors.Is(err, ErrResponseRejectedCached) {
+						rejected = true
+						r.logger.DebugContext(ctx, E.Cause(err, "response rejected for ", FormatQuestion(message.Question[0].String())), " (cached)")
+					} else if errors.Is(err, ErrResponseRejected) {
+						rejected = true
+						r.logger.DebugContext(ctx, E.Cause(err, "response rejected for ", FormatQuestion(message.Question[0].String())))
+					} else if len(message.Question) > 0 {
+						r.logger.ErrorContext(ctx, E.Cause(err, "exchange failed for ", FormatQuestion(message.Question[0].String())))
+					} else {
+						r.logger.ErrorContext(ctx, E.Cause(err, "exchange failed for <empty query>"))
+					}
+				}
+				if responseCheck != nil && rejected {
+					continue
+				}
+				break
+			}
+		}
+	}
+	if err != nil {
+		return nil, err
+	}
+	if r.dnsReverseMapping != nil && len(message.Question) > 0 && response != nil && len(response.Answer) > 0 {
+		if transport == nil || transport.Type() != C.DNSTypeFakeIP {
+			for _, answer := range response.Answer {
+				switch record := answer.(type) {
+				case *mDNS.A:
+					r.dnsReverseMapping.AddWithLifetime(M.AddrFromIP(record.A), FqdnToDomain(record.Hdr.Name), time.Duration(record.Hdr.Ttl)*time.Second)
+				case *mDNS.AAAA:
+					r.dnsReverseMapping.AddWithLifetime(M.AddrFromIP(record.AAAA), FqdnToDomain(record.Hdr.Name), time.Duration(record.Hdr.Ttl)*time.Second)
+				}
+			}
+		}
+	}
+	return response, nil
+}
+
+func (r *Router) Lookup(ctx context.Context, domain string, options adapter.DNSQueryOptions) ([]netip.Addr, error) {
+	var (
+		responseAddrs []netip.Addr
+		cached        bool
+		err           error
+	)
+	printResult := func() {
+		if err != nil {
+			if errors.Is(err, ErrResponseRejectedCached) {
+				r.logger.DebugContext(ctx, "response rejected for ", domain, " (cached)")
+			} else if errors.Is(err, ErrResponseRejected) {
+				r.logger.DebugContext(ctx, "response rejected for ", domain)
+			} else {
+				r.logger.ErrorContext(ctx, E.Cause(err, "lookup failed for ", domain))
+			}
+		} else if len(responseAddrs) == 0 {
+			r.logger.ErrorContext(ctx, "lookup failed for ", domain, ": empty result")
+			err = RCodeNameError
+		}
+	}
+	responseAddrs, cached = r.client.LookupCache(domain, options.Strategy)
+	if cached {
+		if len(responseAddrs) == 0 {
+			return nil, RCodeNameError
+		}
+		return responseAddrs, nil
+	}
+	r.logger.DebugContext(ctx, "lookup domain ", domain)
+	ctx, metadata := adapter.ExtendContext(ctx)
+	metadata.Destination = M.Socksaddr{}
+	metadata.Domain = FqdnToDomain(domain)
+	if options.Transport != nil {
+		transport := options.Transport
+		if legacyTransport, isLegacy := transport.(adapter.LegacyDNSTransport); isLegacy {
+			if options.Strategy == C.DomainStrategyAsIS {
+				options.Strategy = r.defaultDomainStrategy
+			}
+			if !options.ClientSubnet.IsValid() {
+				options.ClientSubnet = legacyTransport.LegacyClientSubnet()
+			}
+		}
+		if options.Strategy == C.DomainStrategyAsIS {
+			options.Strategy = r.defaultDomainStrategy
+		}
+		responseAddrs, err = r.client.Lookup(ctx, transport, domain, options, nil)
+	} else {
+		var (
+			transport adapter.DNSTransport
+			rule      adapter.DNSRule
+			ruleIndex int
+		)
+		ruleIndex = -1
+		for {
+			dnsCtx := adapter.OverrideContext(ctx)
+			transport, rule, ruleIndex = r.matchDNS(ctx, false, ruleIndex, true, &options)
+			if rule != nil {
+				switch action := rule.Action().(type) {
+				case *R.RuleActionReject:
+					switch action.Method {
+					case C.RuleActionRejectMethodDefault:
+						return nil, nil
+					case C.RuleActionRejectMethodDrop:
+						return nil, tun.ErrDrop
+					}
+				}
+			}
+			var responseCheck func(responseAddrs []netip.Addr) bool
+			if rule != nil && rule.WithAddressLimit() {
+				responseCheck = func(responseAddrs []netip.Addr) bool {
+					metadata.DestinationAddresses = responseAddrs
+					return rule.MatchAddressLimit(metadata)
+				}
+			}
+			if options.Strategy == C.DomainStrategyAsIS {
+				options.Strategy = r.defaultDomainStrategy
+			}
+			responseAddrs, err = r.client.Lookup(dnsCtx, transport, domain, options, responseCheck)
+			if responseCheck == nil || err == nil {
+				break
+			}
+			printResult()
+		}
+	}
+	printResult()
+	if len(responseAddrs) > 0 {
+		r.logger.InfoContext(ctx, "lookup succeed for ", domain, ": ", strings.Join(F.MapToString(responseAddrs), " "))
+	}
+	return responseAddrs, err
+}
+
+func isAddressQuery(message *mDNS.Msg) bool {
+	for _, question := range message.Question {
+		if question.Qtype == mDNS.TypeA || question.Qtype == mDNS.TypeAAAA || question.Qtype == mDNS.TypeHTTPS {
+			return true
+		}
+	}
+	return false
+}
+
+func (r *Router) ClearCache() {
+	r.client.ClearCache()
+	if r.platformInterface != nil {
+		r.platformInterface.ClearDNSCache()
+	}
+}
+
+func (r *Router) LookupReverseMapping(ip netip.Addr) (string, bool) {
+	if r.dnsReverseMapping == nil {
+		return "", false
+	}
+	domain, loaded := r.dnsReverseMapping.Get(ip)
+	return domain, loaded
+}
+
+func (r *Router) ResetNetwork() {
+	r.ClearCache()
+	for _, transport := range r.transport.Transports() {
+		transport.Reset()
+	}
+}

dns/transport/dhcp/dhcp.go

@@ -0,0 +1,259 @@
+package dhcp
+
+import (
+	"context"
+	"net"
+	"runtime"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/dialer"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/dns/transport"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing-tun"
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/buf"
+	"github.com/sagernet/sing/common/control"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+	"github.com/sagernet/sing/common/task"
+	"github.com/sagernet/sing/common/x/list"
+	"github.com/sagernet/sing/service"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+	mDNS "github.com/miekg/dns"
+)
+
+func RegisterTransport(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.DHCPDNSServerOptions](registry, C.DNSTypeDHCP, NewTransport)
+}
+
+var _ adapter.DNSTransport = (*Transport)(nil)
+
+type Transport struct {
+	dns.TransportAdapter
+	ctx               context.Context
+	dialer            N.Dialer
+	logger            logger.ContextLogger
+	networkManager    adapter.NetworkManager
+	interfaceName     string
+	interfaceCallback *list.Element[tun.DefaultInterfaceUpdateCallback]
+	transports        []adapter.DNSTransport
+	updateAccess      sync.Mutex
+	updatedAt         time.Time
+}
+
+func NewTransport(ctx context.Context, logger log.ContextLogger, tag string, options option.DHCPDNSServerOptions) (adapter.DNSTransport, error) {
+	transportDialer, err := dns.NewLocalDialer(ctx, options.LocalDNSServerOptions)
+	if err != nil {
+		return nil, err
+	}
+	return &Transport{
+		TransportAdapter: dns.NewTransportAdapterWithLocalOptions(C.DNSTypeDHCP, tag, options.LocalDNSServerOptions),
+		ctx:              ctx,
+		dialer:           transportDialer,
+		logger:           logger,
+		networkManager:   service.FromContext[adapter.NetworkManager](ctx),
+		interfaceName:    options.Interface,
+	}, nil
+}
+
+func (t *Transport) Start(stage adapter.StartStage) error {
+	if stage != adapter.StartStateStart {
+		return nil
+	}
+	err := t.fetchServers()
+	if err != nil {
+		return err
+	}
+	if t.interfaceName == "" {
+		t.interfaceCallback = t.networkManager.InterfaceMonitor().RegisterCallback(t.interfaceUpdated)
+	}
+	return nil
+}
+
+func (t *Transport) Close() error {
+	for _, transport := range t.transports {
+		transport.Reset()
+	}
+	if t.interfaceCallback != nil {
+		t.networkManager.InterfaceMonitor().UnregisterCallback(t.interfaceCallback)
+	}
+	return nil
+}
+
+func (t *Transport) Reset() {
+	for _, transport := range t.transports {
+		transport.Reset()
+	}
+}
+
+func (t *Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	err := t.fetchServers()
+	if err != nil {
+		return nil, err
+	}
+
+	if len(t.transports) == 0 {
+		return nil, E.New("dhcp: empty DNS servers from response")
+	}
+
+	var response *mDNS.Msg
+	for _, transport := range t.transports {
+		response, err = transport.Exchange(ctx, message)
+		if err == nil {
+			return response, nil
+		}
+	}
+	return nil, err
+}
+
+func (t *Transport) fetchInterface() (*control.Interface, error) {
+	if t.interfaceName == "" {
+		if t.networkManager.InterfaceMonitor() == nil {
+			return nil, E.New("missing monitor for auto DHCP, set route.auto_detect_interface")
+		}
+		defaultInterface := t.networkManager.InterfaceMonitor().DefaultInterface()
+		if defaultInterface == nil {
+			return nil, E.New("missing default interface")
+		}
+		return defaultInterface, nil
+	} else {
+		return t.networkManager.InterfaceFinder().ByName(t.interfaceName)
+	}
+}
+
+func (t *Transport) fetchServers() error {
+	if time.Since(t.updatedAt) < C.DHCPTTL {
+		return nil
+	}
+	t.updateAccess.Lock()
+	defer t.updateAccess.Unlock()
+	if time.Since(t.updatedAt) < C.DHCPTTL {
+		return nil
+	}
+	return t.updateServers()
+}
+
+func (t *Transport) updateServers() error {
+	iface, err := t.fetchInterface()
+	if err != nil {
+		return E.Cause(err, "dhcp: prepare interface")
+	}
+
+	t.logger.Info("dhcp: query DNS servers on ", iface.Name)
+	fetchCtx, cancel := context.WithTimeout(t.ctx, C.DHCPTimeout)
+	err = t.fetchServers0(fetchCtx, iface)
+	cancel()
+	if err != nil {
+		return err
+	} else if len(t.transports) == 0 {
+		return E.New("dhcp: empty DNS servers response")
+	} else {
+		t.updatedAt = time.Now()
+		return nil
+	}
+}
+
+func (t *Transport) interfaceUpdated(defaultInterface *control.Interface, flags int) {
+	err := t.updateServers()
+	if err != nil {
+		t.logger.Error("update servers: ", err)
+	}
+}
+
+func (t *Transport) fetchServers0(ctx context.Context, iface *control.Interface) error {
+	var listener net.ListenConfig
+	listener.Control = control.Append(listener.Control, control.BindToInterface(t.networkManager.InterfaceFinder(), iface.Name, iface.Index))
+	listener.Control = control.Append(listener.Control, control.ReuseAddr())
+	listenAddr := "0.0.0.0:68"
+	if runtime.GOOS == "linux" || runtime.GOOS == "android" {
+		listenAddr = "255.255.255.255:68"
+	}
+	packetConn, err := listener.ListenPacket(t.ctx, "udp4", listenAddr)
+	if err != nil {
+		return err
+	}
+	defer packetConn.Close()
+
+	discovery, err := dhcpv4.NewDiscovery(iface.HardwareAddr, dhcpv4.WithBroadcast(true), dhcpv4.WithRequestedOptions(dhcpv4.OptionDomainNameServer))
+	if err != nil {
+		return err
+	}
+
+	_, err = packetConn.WriteTo(discovery.ToBytes(), &net.UDPAddr{IP: net.IPv4bcast, Port: 67})
+	if err != nil {
+		return err
+	}
+
+	var group task.Group
+	group.Append0(func(ctx context.Context) error {
+		return t.fetchServersResponse(iface, packetConn, discovery.TransactionID)
+	})
+	group.Cleanup(func() {
+		packetConn.Close()
+	})
+	return group.Run(ctx)
+}
+
+func (t *Transport) fetchServersResponse(iface *control.Interface, packetConn net.PacketConn, transactionID dhcpv4.TransactionID) error {
+	buffer := buf.NewSize(dhcpv4.MaxMessageSize)
+	defer buffer.Release()
+
+	for {
+		_, _, err := buffer.ReadPacketFrom(packetConn)
+		if err != nil {
+			return err
+		}
+
+		dhcpPacket, err := dhcpv4.FromBytes(buffer.Bytes())
+		if err != nil {
+			t.logger.Trace("dhcp: parse DHCP response: ", err)
+			return err
+		}
+
+		if dhcpPacket.MessageType() != dhcpv4.MessageTypeOffer {
+			t.logger.Trace("dhcp: expected OFFER response, but got ", dhcpPacket.MessageType())
+			continue
+		}
+
+		if dhcpPacket.TransactionID != transactionID {
+			t.logger.Trace("dhcp: expected transaction ID ", transactionID, ", but got ", dhcpPacket.TransactionID)
+			continue
+		}
+
+		dns := dhcpPacket.DNS()
+		if len(dns) == 0 {
+			return nil
+		}
+		return t.recreateServers(iface, common.Map(dns, func(it net.IP) M.Socksaddr {
+			return M.SocksaddrFrom(M.AddrFromIP(it), 53)
+		}))
+	}
+}
+
+func (t *Transport) recreateServers(iface *control.Interface, serverAddrs []M.Socksaddr) error {
+	if len(serverAddrs) > 0 {
+		t.logger.Info("dhcp: updated DNS servers from ", iface.Name, ": [", strings.Join(common.Map(serverAddrs, M.Socksaddr.String), ","), "]")
+	}
+	serverDialer := common.Must1(dialer.NewDefault(t.ctx, option.DialerOptions{
+		BindInterface:      iface.Name,
+		UDPFragmentDefault: true,
+	}))
+	var transports []adapter.DNSTransport
+	for _, serverAddr := range serverAddrs {
+		transports = append(transports, transport.NewUDPRaw(t.logger, t.TransportAdapter, serverDialer, serverAddr))
+	}
+	for _, transport := range t.transports {
+		transport.Reset()
+	}
+	t.transports = transports
+	return nil
+}

dns/transport/fakeip/fakeip.go

@@ -0,0 +1,67 @@
+package fakeip
+
+import (
+	"context"
+	"net/netip"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+
+	mDNS "github.com/miekg/dns"
+)
+
+func RegisterTransport(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.FakeIPDNSServerOptions](registry, C.DNSTypeFakeIP, NewTransport)
+}
+
+var _ adapter.FakeIPTransport = (*Transport)(nil)
+
+type Transport struct {
+	dns.TransportAdapter
+	logger logger.ContextLogger
+	store  adapter.FakeIPStore
+}
+
+func NewTransport(ctx context.Context, logger log.ContextLogger, tag string, options option.FakeIPDNSServerOptions) (adapter.DNSTransport, error) {
+	store := NewStore(ctx, logger, options.Inet4Range.Build(netip.Prefix{}), options.Inet6Range.Build(netip.Prefix{}))
+	return &Transport{
+		TransportAdapter: dns.NewTransportAdapter(C.DNSTypeFakeIP, tag, nil),
+		logger:           logger,
+		store:            store,
+	}, nil
+}
+
+func (t *Transport) Start(stage adapter.StartStage) error {
+	if stage != adapter.StartStateStart {
+		return nil
+	}
+	return t.store.Start()
+}
+
+func (t *Transport) Close() error {
+	return t.store.Close()
+}
+
+func (t *Transport) Reset() {
+}
+
+func (t *Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	question := message.Question[0]
+	if question.Qtype != mDNS.TypeA && question.Qtype != mDNS.TypeAAAA {
+		return nil, E.New("only IP queries are supported by fakeip")
+	}
+	address, err := t.store.Create(dns.FqdnToDomain(question.Name), question.Qtype == mDNS.TypeAAAA)
+	if err != nil {
+		return nil, err
+	}
+	return dns.FixedResponse(message.Id, question, []netip.Addr{address}, C.DefaultDNSTTL), nil
+}
+
+func (t *Transport) Store() adapter.FakeIPStore {
+	return t.store
+}

dns/transport/fakeip/memory.go

@@ -0,0 +1,89 @@
+package fakeip
+
+import (
+	"net/netip"
+	"sync"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing/common/logger"
+)
+
+var _ adapter.FakeIPStorage = (*MemoryStorage)(nil)
+
+type MemoryStorage struct {
+	addressAccess sync.RWMutex
+	domainAccess  sync.RWMutex
+	addressCache  map[netip.Addr]string
+	domainCache4  map[string]netip.Addr
+	domainCache6  map[string]netip.Addr
+}
+
+func NewMemoryStorage() *MemoryStorage {
+	return &MemoryStorage{
+		addressCache: make(map[netip.Addr]string),
+		domainCache4: make(map[string]netip.Addr),
+		domainCache6: make(map[string]netip.Addr),
+	}
+}
+
+func (s *MemoryStorage) FakeIPMetadata() *adapter.FakeIPMetadata {
+	return nil
+}
+
+func (s *MemoryStorage) FakeIPSaveMetadata(metadata *adapter.FakeIPMetadata) error {
+	return nil
+}
+
+func (s *MemoryStorage) FakeIPSaveMetadataAsync(metadata *adapter.FakeIPMetadata) {
+}
+
+func (s *MemoryStorage) FakeIPStore(address netip.Addr, domain string) error {
+	s.addressAccess.Lock()
+	s.domainAccess.Lock()
+	if oldDomain, loaded := s.addressCache[address]; loaded {
+		if address.Is4() {
+			delete(s.domainCache4, oldDomain)
+		} else {
+			delete(s.domainCache6, oldDomain)
+		}
+	}
+	s.addressCache[address] = domain
+	if address.Is4() {
+		s.domainCache4[domain] = address
+	} else {
+		s.domainCache6[domain] = address
+	}
+	s.domainAccess.Unlock()
+	s.addressAccess.Unlock()
+	return nil
+}
+
+func (s *MemoryStorage) FakeIPStoreAsync(address netip.Addr, domain string, logger logger.Logger) {
+	_ = s.FakeIPStore(address, domain)
+}
+
+func (s *MemoryStorage) FakeIPLoad(address netip.Addr) (string, bool) {
+	s.addressAccess.RLock()
+	defer s.addressAccess.RUnlock()
+	domain, loaded := s.addressCache[address]
+	return domain, loaded
+}
+
+func (s *MemoryStorage) FakeIPLoadDomain(domain string, isIPv6 bool) (netip.Addr, bool) {
+	s.domainAccess.RLock()
+	defer s.domainAccess.RUnlock()
+	if !isIPv6 {
+		address, loaded := s.domainCache4[domain]
+		return address, loaded
+	} else {
+		address, loaded := s.domainCache6[domain]
+		return address, loaded
+	}
+}
+
+func (s *MemoryStorage) FakeIPReset() error {
+	s.addressCache = make(map[netip.Addr]string)
+	s.domainCache4 = make(map[string]netip.Addr)
+	s.domainCache6 = make(map[string]netip.Addr)
+	return nil
+}

dns/transport/fakeip/store.go

@@ -0,0 +1,118 @@
+package fakeip
+
+import (
+	"context"
+	"net/netip"
+
+	"github.com/sagernet/sing-box/adapter"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	"github.com/sagernet/sing/service"
+)
+
+var _ adapter.FakeIPStore = (*Store)(nil)
+
+type Store struct {
+	ctx          context.Context
+	logger       logger.Logger
+	inet4Range   netip.Prefix
+	inet6Range   netip.Prefix
+	storage      adapter.FakeIPStorage
+	inet4Current netip.Addr
+	inet6Current netip.Addr
+}
+
+func NewStore(ctx context.Context, logger logger.Logger, inet4Range netip.Prefix, inet6Range netip.Prefix) *Store {
+	return &Store{
+		ctx:        ctx,
+		logger:     logger,
+		inet4Range: inet4Range,
+		inet6Range: inet6Range,
+	}
+}
+
+func (s *Store) Start() error {
+	var storage adapter.FakeIPStorage
+	cacheFile := service.FromContext[adapter.CacheFile](s.ctx)
+	if cacheFile != nil && cacheFile.StoreFakeIP() {
+		storage = cacheFile
+	}
+	if storage == nil {
+		storage = NewMemoryStorage()
+	}
+	metadata := storage.FakeIPMetadata()
+	if metadata != nil && metadata.Inet4Range == s.inet4Range && metadata.Inet6Range == s.inet6Range {
+		s.inet4Current = metadata.Inet4Current
+		s.inet6Current = metadata.Inet6Current
+	} else {
+		if s.inet4Range.IsValid() {
+			s.inet4Current = s.inet4Range.Addr().Next().Next()
+		}
+		if s.inet6Range.IsValid() {
+			s.inet6Current = s.inet6Range.Addr().Next().Next()
+		}
+		_ = storage.FakeIPReset()
+	}
+	s.storage = storage
+	return nil
+}
+
+func (s *Store) Contains(address netip.Addr) bool {
+	return s.inet4Range.Contains(address) || s.inet6Range.Contains(address)
+}
+
+func (s *Store) Close() error {
+	if s.storage == nil {
+		return nil
+	}
+	return s.storage.FakeIPSaveMetadata(&adapter.FakeIPMetadata{
+		Inet4Range:   s.inet4Range,
+		Inet6Range:   s.inet6Range,
+		Inet4Current: s.inet4Current,
+		Inet6Current: s.inet6Current,
+	})
+}
+
+func (s *Store) Create(domain string, isIPv6 bool) (netip.Addr, error) {
+	if address, loaded := s.storage.FakeIPLoadDomain(domain, isIPv6); loaded {
+		return address, nil
+	}
+	var address netip.Addr
+	if !isIPv6 {
+		if !s.inet4Current.IsValid() {
+			return netip.Addr{}, E.New("missing IPv4 fakeip address range")
+		}
+		nextAddress := s.inet4Current.Next()
+		if !s.inet4Range.Contains(nextAddress) {
+			nextAddress = s.inet4Range.Addr().Next().Next()
+		}
+		s.inet4Current = nextAddress
+		address = nextAddress
+	} else {
+		if !s.inet6Current.IsValid() {
+			return netip.Addr{}, E.New("missing IPv6 fakeip address range")
+		}
+		nextAddress := s.inet6Current.Next()
+		if !s.inet6Range.Contains(nextAddress) {
+			nextAddress = s.inet6Range.Addr().Next().Next()
+		}
+		s.inet6Current = nextAddress
+		address = nextAddress
+	}
+	s.storage.FakeIPStoreAsync(address, domain, s.logger)
+	s.storage.FakeIPSaveMetadataAsync(&adapter.FakeIPMetadata{
+		Inet4Range:   s.inet4Range,
+		Inet6Range:   s.inet6Range,
+		Inet4Current: s.inet4Current,
+		Inet6Current: s.inet6Current,
+	})
+	return address, nil
+}
+
+func (s *Store) Lookup(address netip.Addr) (string, bool) {
+	return s.storage.FakeIPLoad(address)
+}
+
+func (s *Store) Reset() error {
+	return s.storage.FakeIPReset()
+}

dns/transport/hosts/hosts.go

@@ -0,0 +1,63 @@
+package hosts
+
+import (
+	"context"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+
+	mDNS "github.com/miekg/dns"
+)
+
+func RegisterTransport(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.HostsDNSServerOptions](registry, C.DNSTypeHosts, NewTransport)
+}
+
+var _ adapter.DNSTransport = (*Transport)(nil)
+
+type Transport struct {
+	dns.TransportAdapter
+	files []*File
+}
+
+func NewTransport(ctx context.Context, logger log.ContextLogger, tag string, options option.HostsDNSServerOptions) (adapter.DNSTransport, error) {
+	var files []*File
+	if len(options.Path) == 0 {
+		files = append(files, NewFile(DefaultPath))
+	} else {
+		for _, path := range options.Path {
+			files = append(files, NewFile(path))
+		}
+	}
+	return &Transport{
+		TransportAdapter: dns.NewTransportAdapter(C.DNSTypeHosts, tag, nil),
+		files:            files,
+	}, nil
+}
+
+func (t *Transport) Reset() {
+}
+
+func (t *Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	question := message.Question[0]
+	domain := dns.FqdnToDomain(question.Name)
+	if question.Qtype == mDNS.TypeA || question.Qtype == mDNS.TypeAAAA {
+		for _, file := range t.files {
+			addresses := file.Lookup(domain)
+			if len(addresses) > 0 {
+				return dns.FixedResponse(message.Id, question, addresses, C.DefaultDNSTTL), nil
+			}
+		}
+	}
+	return &mDNS.Msg{
+		MsgHdr: mDNS.MsgHdr{
+			Id:       message.Id,
+			Rcode:    mDNS.RcodeNameError,
+			Response: true,
+		},
+		Question: []mDNS.Question{question},
+	}, nil
+}

dns/transport/hosts/hosts_file.go

@@ -0,0 +1,102 @@
+package hosts
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"net/netip"
+	"os"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/miekg/dns"
+)
+
+const cacheMaxAge = 5 * time.Second
+
+type File struct {
+	path    string
+	access  sync.Mutex
+	byName  map[string][]netip.Addr
+	expire  time.Time
+	modTime time.Time
+	size    int64
+}
+
+func NewFile(path string) *File {
+	return &File{
+		path: path,
+	}
+}
+
+func (f *File) Lookup(name string) []netip.Addr {
+	f.access.Lock()
+	defer f.access.Unlock()
+	f.update()
+	return f.byName[name]
+}
+
+func (f *File) update() {
+	now := time.Now()
+	if now.Before(f.expire) && len(f.byName) > 0 {
+		return
+	}
+	stat, err := os.Stat(f.path)
+	if err != nil {
+		return
+	}
+	if f.modTime.Equal(stat.ModTime()) && f.size == stat.Size() {
+		f.expire = now.Add(cacheMaxAge)
+		return
+	}
+	byName := make(map[string][]netip.Addr)
+	file, err := os.Open(f.path)
+	if err != nil {
+		return
+	}
+	defer file.Close()
+	reader := bufio.NewReader(file)
+	var (
+		prefix   []byte
+		line     []byte
+		isPrefix bool
+	)
+	for {
+		line, isPrefix, err = reader.ReadLine()
+		if err != nil {
+			if errors.Is(err, io.EOF) {
+				break
+			}
+			return
+		}
+		if isPrefix {
+			prefix = append(prefix, line...)
+			continue
+		} else if len(prefix) > 0 {
+			line = append(prefix, line...)
+			prefix = nil
+		}
+		commentIndex := strings.IndexRune(string(line), '#')
+		if commentIndex != -1 {
+			line = line[:commentIndex]
+		}
+		fields := strings.Fields(string(line))
+		if len(fields) < 2 {
+			continue
+		}
+		var addr netip.Addr
+		addr, err = netip.ParseAddr(fields[0])
+		if err != nil {
+			continue
+		}
+		for index := 1; index < len(fields); index++ {
+			canonicalName := dns.CanonicalName(fields[index])
+			byName[canonicalName] = append(byName[canonicalName], addr)
+		}
+	}
+	f.expire = now.Add(cacheMaxAge)
+	f.modTime = stat.ModTime()
+	f.size = stat.Size()
+	f.byName = byName
+}

dns/transport/hosts/hosts_test.go

@@ -0,0 +1,16 @@
+package hosts_test
+
+import (
+	"net/netip"
+	"testing"
+
+	"github.com/sagernet/sing-box/dns/transport/hosts"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestHosts(t *testing.T) {
+	t.Parallel()
+	require.Equal(t, []netip.Addr{netip.AddrFrom4([4]byte{127, 0, 0, 1}), netip.IPv6Loopback()}, hosts.NewFile("testdata/hosts").Lookup("localhost."))
+	require.NotEmpty(t, hosts.NewFile(hosts.DefaultPath).Lookup("localhost."))
+}

dns/transport/hosts/hosts_unix.go

@@ -0,0 +1,5 @@
+//go:build !windows
+
+package hosts
+
+var DefaultPath = "/etc/hosts"

dns/transport/hosts/hosts_windows.go

@@ -0,0 +1,17 @@
+package hosts
+
+import (
+	"path/filepath"
+
+	"golang.org/x/sys/windows"
+)
+
+var DefaultPath string
+
+func init() {
+	systemDirectory, err := windows.GetSystemDirectory()
+	if err != nil {
+		systemDirectory = "C:\\Windows\\System32"
+	}
+	DefaultPath = filepath.Join(systemDirectory, "Drivers/etc/hosts")
+}

dns/transport/hosts/testdata/hosts

@@ -0,0 +1,2 @@
+127.0.0.1       localhost
+::1             localhost

dns/transport/https.go

@@ -0,0 +1,204 @@
+package transport
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strconv"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/tls"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/buf"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+	aTLS "github.com/sagernet/sing/common/tls"
+	sHTTP "github.com/sagernet/sing/protocol/http"
+
+	mDNS "github.com/miekg/dns"
+	"golang.org/x/net/http2"
+)
+
+const MimeType = "application/dns-message"
+
+var _ adapter.DNSTransport = (*HTTPSTransport)(nil)
+
+func RegisterHTTPS(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.RemoteHTTPSDNSServerOptions](registry, C.DNSTypeHTTPS, NewHTTPS)
+}
+
+type HTTPSTransport struct {
+	dns.TransportAdapter
+	logger      logger.ContextLogger
+	dialer      N.Dialer
+	destination *url.URL
+	headers     http.Header
+	transport   *http.Transport
+}
+
+func NewHTTPS(ctx context.Context, logger log.ContextLogger, tag string, options option.RemoteHTTPSDNSServerOptions) (adapter.DNSTransport, error) {
+	transportDialer, err := dns.NewRemoteDialer(ctx, options.RemoteDNSServerOptions)
+	if err != nil {
+		return nil, err
+	}
+	tlsOptions := common.PtrValueOrDefault(options.TLS)
+	tlsOptions.Enabled = true
+	tlsConfig, err := tls.NewClient(ctx, options.Server, tlsOptions)
+	if err != nil {
+		return nil, err
+	}
+	if common.Error(tlsConfig.Config()) == nil && !common.Contains(tlsConfig.NextProtos(), http2.NextProtoTLS) {
+		tlsConfig.SetNextProtos(append(tlsConfig.NextProtos(), http2.NextProtoTLS))
+	}
+	if !common.Contains(tlsConfig.NextProtos(), "http/1.1") {
+		tlsConfig.SetNextProtos(append(tlsConfig.NextProtos(), "http/1.1"))
+	}
+	headers := options.Headers.Build()
+	host := headers.Get("Host")
+	if host != "" {
+		headers.Del("Host")
+	} else {
+		if tlsConfig.ServerName() != "" {
+			host = tlsConfig.ServerName()
+		} else {
+			host = options.Server
+		}
+	}
+	destinationURL := url.URL{
+		Scheme: "https",
+		Host:   host,
+	}
+	if destinationURL.Host == "" {
+		destinationURL.Host = options.Server
+	}
+	if options.ServerPort != 0 && options.ServerPort != 443 {
+		destinationURL.Host = net.JoinHostPort(destinationURL.Host, strconv.Itoa(int(options.ServerPort)))
+	}
+	path := options.Path
+	if path == "" {
+		path = "/dns-query"
+	}
+	err = sHTTP.URLSetPath(&destinationURL, path)
+	if err != nil {
+		return nil, err
+	}
+	serverAddr := options.ServerOptions.Build()
+	if serverAddr.Port == 0 {
+		serverAddr.Port = 443
+	}
+	return NewHTTPSRaw(
+		dns.NewTransportAdapterWithRemoteOptions(C.DNSTypeHTTPS, tag, options.RemoteDNSServerOptions),
+		logger,
+		transportDialer,
+		&destinationURL,
+		headers,
+		serverAddr,
+		tlsConfig,
+	), nil
+}
+
+func NewHTTPSRaw(
+	adapter dns.TransportAdapter,
+	logger log.ContextLogger,
+	dialer N.Dialer,
+	destination *url.URL,
+	headers http.Header,
+	serverAddr M.Socksaddr,
+	tlsConfig tls.Config,
+) *HTTPSTransport {
+	var transport *http.Transport
+	if tlsConfig != nil {
+		transport = &http.Transport{
+			ForceAttemptHTTP2: true,
+			DialTLSContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+				tcpConn, hErr := dialer.DialContext(ctx, network, serverAddr)
+				if hErr != nil {
+					return nil, hErr
+				}
+				tlsConn, hErr := aTLS.ClientHandshake(ctx, tcpConn, tlsConfig)
+				if hErr != nil {
+					tcpConn.Close()
+					return nil, hErr
+				}
+				return tlsConn, nil
+			},
+		}
+	} else {
+		transport = &http.Transport{
+			DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+				return dialer.DialContext(ctx, network, serverAddr)
+			},
+		}
+	}
+	return &HTTPSTransport{
+		TransportAdapter: adapter,
+		logger:           logger,
+		dialer:           dialer,
+		destination:      destination,
+		headers:          headers,
+		transport:        transport,
+	}
+}
+
+func (t *HTTPSTransport) Reset() {
+	t.transport.CloseIdleConnections()
+	t.transport = t.transport.Clone()
+}
+
+func (t *HTTPSTransport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	exMessage := *message
+	exMessage.Id = 0
+	exMessage.Compress = true
+	requestBuffer := buf.NewSize(1 + message.Len())
+	rawMessage, err := exMessage.PackBuffer(requestBuffer.FreeBytes())
+	if err != nil {
+		requestBuffer.Release()
+		return nil, err
+	}
+	request, err := http.NewRequestWithContext(ctx, http.MethodPost, t.destination.String(), bytes.NewReader(rawMessage))
+	if err != nil {
+		requestBuffer.Release()
+		return nil, err
+	}
+	request.Header = t.headers.Clone()
+	request.Header.Set("Content-Type", MimeType)
+	request.Header.Set("Accept", MimeType)
+	response, err := t.transport.RoundTrip(request)
+	requestBuffer.Release()
+	if err != nil {
+		return nil, err
+	}
+	defer response.Body.Close()
+	if response.StatusCode != http.StatusOK {
+		return nil, E.New("unexpected status: ", response.Status)
+	}
+	var responseMessage mDNS.Msg
+	if response.ContentLength > 0 {
+		responseBuffer := buf.NewSize(int(response.ContentLength))
+		_, err = responseBuffer.ReadFullFrom(response.Body, int(response.ContentLength))
+		if err != nil {
+			return nil, err
+		}
+		err = responseMessage.Unpack(responseBuffer.Bytes())
+		responseBuffer.Release()
+	} else {
+		rawMessage, err = io.ReadAll(response.Body)
+		if err != nil {
+			return nil, err
+		}
+		err = responseMessage.Unpack(rawMessage)
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &responseMessage, nil
+}

dns/transport/local/local.go

@@ -0,0 +1,197 @@
+package local
+
+import (
+	"context"
+	"math/rand"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/dns/transport/hosts"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common/buf"
+	E "github.com/sagernet/sing/common/exceptions"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+
+	mDNS "github.com/miekg/dns"
+)
+
+func RegisterTransport(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.LocalDNSServerOptions](registry, C.DNSTypeLocal, NewTransport)
+}
+
+var _ adapter.DNSTransport = (*Transport)(nil)
+
+type Transport struct {
+	dns.TransportAdapter
+	hosts  *hosts.File
+	dialer N.Dialer
+}
+
+func NewTransport(ctx context.Context, logger log.ContextLogger, tag string, options option.LocalDNSServerOptions) (adapter.DNSTransport, error) {
+	transportDialer, err := dns.NewLocalDialer(ctx, options)
+	if err != nil {
+		return nil, err
+	}
+	return &Transport{
+		TransportAdapter: dns.NewTransportAdapterWithLocalOptions(C.DNSTypeLocal, tag, options),
+		hosts:            hosts.NewFile(hosts.DefaultPath),
+		dialer:           transportDialer,
+	}, nil
+}
+
+func (t *Transport) Reset() {
+}
+
+func (t *Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	question := message.Question[0]
+	domain := dns.FqdnToDomain(question.Name)
+	if question.Qtype == mDNS.TypeA || question.Qtype == mDNS.TypeAAAA {
+		addresses := t.hosts.Lookup(domain)
+		if len(addresses) > 0 {
+			return dns.FixedResponse(message.Id, question, addresses, C.DefaultDNSTTL), nil
+		}
+	}
+	systemConfig := getSystemDNSConfig()
+	if systemConfig.singleRequest || !(message.Question[0].Qtype == mDNS.TypeA || message.Question[0].Qtype == mDNS.TypeAAAA) {
+		return t.exchangeSingleRequest(ctx, systemConfig, message, domain)
+	} else {
+		return t.exchangeParallel(ctx, systemConfig, message, domain)
+	}
+}
+
+func (t *Transport) exchangeSingleRequest(ctx context.Context, systemConfig *dnsConfig, message *mDNS.Msg, domain string) (*mDNS.Msg, error) {
+	var lastErr error
+	for _, fqdn := range systemConfig.nameList(domain) {
+		response, err := t.tryOneName(ctx, systemConfig, fqdn, message)
+		if err != nil {
+			lastErr = err
+			continue
+		}
+		return response, nil
+	}
+	return nil, lastErr
+}
+
+func (t *Transport) exchangeParallel(ctx context.Context, systemConfig *dnsConfig, message *mDNS.Msg, domain string) (*mDNS.Msg, error) {
+	returned := make(chan struct{})
+	defer close(returned)
+	type queryResult struct {
+		response *mDNS.Msg
+		err      error
+	}
+	results := make(chan queryResult)
+	startRacer := func(ctx context.Context, fqdn string) {
+		response, err := t.tryOneName(ctx, systemConfig, fqdn, message)
+		if err == nil {
+			addresses, _ := dns.MessageToAddresses(response)
+			if len(addresses) == 0 {
+				err = E.New(fqdn, ": empty result")
+			}
+		}
+		select {
+		case results <- queryResult{response, err}:
+		case <-returned:
+		}
+	}
+	queryCtx, queryCancel := context.WithCancel(ctx)
+	defer queryCancel()
+	var nameCount int
+	for _, fqdn := range systemConfig.nameList(domain) {
+		nameCount++
+		go startRacer(queryCtx, fqdn)
+	}
+	var errors []error
+	for {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case result := <-results:
+			if result.err == nil {
+				return result.response, nil
+			}
+			errors = append(errors, result.err)
+			if len(errors) == nameCount {
+				return nil, E.Errors(errors...)
+			}
+		}
+	}
+}
+
+func (t *Transport) tryOneName(ctx context.Context, config *dnsConfig, fqdn string, message *mDNS.Msg) (*mDNS.Msg, error) {
+	serverOffset := config.serverOffset()
+	sLen := uint32(len(config.servers))
+	var lastErr error
+	for i := 0; i < config.attempts; i++ {
+		for j := uint32(0); j < sLen; j++ {
+			server := config.servers[(serverOffset+j)%sLen]
+			question := message.Question[0]
+			question.Name = fqdn
+			response, err := t.exchangeOne(ctx, M.ParseSocksaddr(server), question, config.timeout, config.useTCP, config.trustAD)
+			if err != nil {
+				lastErr = err
+				continue
+			}
+			return response, nil
+		}
+	}
+	return nil, E.Cause(lastErr, fqdn)
+}
+
+func (t *Transport) exchangeOne(ctx context.Context, server M.Socksaddr, question mDNS.Question, timeout time.Duration, useTCP, ad bool) (*mDNS.Msg, error) {
+	var networks []string
+	if useTCP {
+		networks = []string{N.NetworkTCP}
+	} else {
+		networks = []string{N.NetworkUDP, N.NetworkTCP}
+	}
+	request := &mDNS.Msg{
+		MsgHdr: mDNS.MsgHdr{
+			Id:                uint16(rand.Uint32()),
+			RecursionDesired:  true,
+			AuthenticatedData: ad,
+		},
+		Question: []mDNS.Question{question},
+		Compress: true,
+	}
+	request.SetEdns0(maxDNSPacketSize, false)
+	buffer := buf.Get(buf.UDPBufferSize)
+	defer buf.Put(buffer)
+	for _, network := range networks {
+		ctx, cancel := context.WithDeadline(ctx, time.Now().Add(timeout))
+		defer cancel()
+		conn, err := t.dialer.DialContext(ctx, network, server)
+		if err != nil {
+			return nil, err
+		}
+		defer conn.Close()
+		if deadline, loaded := ctx.Deadline(); loaded && !deadline.IsZero() {
+			conn.SetDeadline(deadline)
+		}
+		rawMessage, err := request.PackBuffer(buffer)
+		if err != nil {
+			return nil, E.Cause(err, "pack request")
+		}
+		_, err = conn.Write(rawMessage)
+		if err != nil {
+			return nil, E.Cause(err, "write request")
+		}
+		n, err := conn.Read(buffer)
+		if err != nil {
+			return nil, E.Cause(err, "read response")
+		}
+		var response mDNS.Msg
+		err = response.Unpack(buffer[:n])
+		if err != nil {
+			return nil, E.Cause(err, "unpack response")
+		}
+		if response.Truncated && network == N.NetworkUDP {
+			continue
+		}
+		return &response, nil
+	}
+	panic("unexpected")
+}

dns/transport/local/resolv.go

@@ -0,0 +1,146 @@
+package local
+
+import (
+	"os"
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+const (
+	// net.maxDNSPacketSize
+	maxDNSPacketSize = 1232
+)
+
+type resolverConfig struct {
+	initOnce    sync.Once
+	ch          chan struct{}
+	lastChecked time.Time
+	dnsConfig   atomic.Pointer[dnsConfig]
+}
+
+var resolvConf resolverConfig
+
+func getSystemDNSConfig() *dnsConfig {
+	resolvConf.tryUpdate("/etc/resolv.conf")
+	return resolvConf.dnsConfig.Load()
+}
+
+func (conf *resolverConfig) init() {
+	conf.dnsConfig.Store(dnsReadConfig("/etc/resolv.conf"))
+	conf.lastChecked = time.Now()
+	conf.ch = make(chan struct{}, 1)
+}
+
+func (conf *resolverConfig) tryUpdate(name string) {
+	conf.initOnce.Do(conf.init)
+
+	if conf.dnsConfig.Load().noReload {
+		return
+	}
+	if !conf.tryAcquireSema() {
+		return
+	}
+	defer conf.releaseSema()
+
+	now := time.Now()
+	if conf.lastChecked.After(now.Add(-5 * time.Second)) {
+		return
+	}
+	conf.lastChecked = now
+	if runtime.GOOS != "windows" {
+		var mtime time.Time
+		if fi, err := os.Stat(name); err == nil {
+			mtime = fi.ModTime()
+		}
+		if mtime.Equal(conf.dnsConfig.Load().mtime) {
+			return
+		}
+	}
+	dnsConf := dnsReadConfig(name)
+	conf.dnsConfig.Store(dnsConf)
+}
+
+func (conf *resolverConfig) tryAcquireSema() bool {
+	select {
+	case conf.ch <- struct{}{}:
+		return true
+	default:
+		return false
+	}
+}
+
+func (conf *resolverConfig) releaseSema() {
+	<-conf.ch
+}
+
+type dnsConfig struct {
+	servers       []string
+	search        []string
+	ndots         int
+	timeout       time.Duration
+	attempts      int
+	rotate        bool
+	unknownOpt    bool
+	lookup        []string
+	err           error
+	mtime         time.Time
+	soffset       uint32
+	singleRequest bool
+	useTCP        bool
+	trustAD       bool
+	noReload      bool
+}
+
+func (c *dnsConfig) serverOffset() uint32 {
+	if c.rotate {
+		return atomic.AddUint32(&c.soffset, 1) - 1 // return 0 to start
+	}
+	return 0
+}
+
+func (conf *dnsConfig) nameList(name string) []string {
+	l := len(name)
+	rooted := l > 0 && name[l-1] == '.'
+	if l > 254 || l == 254 && !rooted {
+		return nil
+	}
+
+	if rooted {
+		if avoidDNS(name) {
+			return nil
+		}
+		return []string{name}
+	}
+
+	hasNdots := strings.Count(name, ".") >= conf.ndots
+	name += "."
+	// l++
+
+	names := make([]string, 0, 1+len(conf.search))
+	if hasNdots && !avoidDNS(name) {
+		names = append(names, name)
+	}
+	for _, suffix := range conf.search {
+		fqdn := name + suffix
+		if !avoidDNS(fqdn) && len(fqdn) <= 254 {
+			names = append(names, fqdn)
+		}
+	}
+	if !hasNdots && !avoidDNS(name) {
+		names = append(names, name)
+	}
+	return names
+}
+
+func avoidDNS(name string) bool {
+	if name == "" {
+		return true
+	}
+	if name[len(name)-1] == '.' {
+		name = name[:len(name)-1]
+	}
+	return strings.HasSuffix(name, ".onion")
+}

dns/transport/local/resolv_unix.go

@@ -0,0 +1,175 @@
+//go:build !windows
+
+package local
+
+import (
+	"bufio"
+	"net"
+	"net/netip"
+	"os"
+	"strings"
+	"time"
+	_ "unsafe"
+)
+
+func dnsReadConfig(name string) *dnsConfig {
+	conf := &dnsConfig{
+		ndots:    1,
+		timeout:  5 * time.Second,
+		attempts: 2,
+	}
+	file, err := os.Open(name)
+	if err != nil {
+		conf.servers = defaultNS
+		conf.search = dnsDefaultSearch()
+		conf.err = err
+		return conf
+	}
+	defer file.Close()
+	fi, err := file.Stat()
+	if err == nil {
+		conf.mtime = fi.ModTime()
+	} else {
+		conf.servers = defaultNS
+		conf.search = dnsDefaultSearch()
+		conf.err = err
+		return conf
+	}
+	reader := bufio.NewReader(file)
+	var (
+		prefix   []byte
+		line     []byte
+		isPrefix bool
+	)
+	for {
+		line, isPrefix, err = reader.ReadLine()
+		if err != nil {
+			break
+		}
+		if isPrefix {
+			prefix = append(prefix, line...)
+			continue
+		} else if len(prefix) > 0 {
+			line = append(prefix, line...)
+			prefix = nil
+		}
+		if len(line) > 0 && (line[0] == ';' || line[0] == '#') {
+			continue
+		}
+		f := strings.Fields(string(line))
+		if len(f) < 1 {
+			continue
+		}
+		switch f[0] {
+		case "nameserver":
+			if len(f) > 1 && len(conf.servers) < 3 {
+				if _, err := netip.ParseAddr(f[1]); err == nil {
+					conf.servers = append(conf.servers, net.JoinHostPort(f[1], "53"))
+				}
+			}
+		case "domain":
+			if len(f) > 1 {
+				conf.search = []string{ensureRooted(f[1])}
+			}
+
+		case "search":
+			conf.search = make([]string, 0, len(f)-1)
+			for i := 1; i < len(f); i++ {
+				name := ensureRooted(f[i])
+				if name == "." {
+					continue
+				}
+				conf.search = append(conf.search, name)
+			}
+
+		case "options":
+			for _, s := range f[1:] {
+				switch {
+				case strings.HasPrefix(s, "ndots:"):
+					n, _, _ := dtoi(s[6:])
+					if n < 0 {
+						n = 0
+					} else if n > 15 {
+						n = 15
+					}
+					conf.ndots = n
+				case strings.HasPrefix(s, "timeout:"):
+					n, _, _ := dtoi(s[8:])
+					if n < 1 {
+						n = 1
+					}
+					conf.timeout = time.Duration(n) * time.Second
+				case strings.HasPrefix(s, "attempts:"):
+					n, _, _ := dtoi(s[9:])
+					if n < 1 {
+						n = 1
+					}
+					conf.attempts = n
+				case s == "rotate":
+					conf.rotate = true
+				case s == "single-request" || s == "single-request-reopen":
+					conf.singleRequest = true
+				case s == "use-vc" || s == "usevc" || s == "tcp":
+					conf.useTCP = true
+				case s == "trust-ad":
+					conf.trustAD = true
+				case s == "edns0":
+				case s == "no-reload":
+					conf.noReload = true
+				default:
+					conf.unknownOpt = true
+				}
+			}
+
+		case "lookup":
+			conf.lookup = f[1:]
+
+		default:
+			conf.unknownOpt = true
+		}
+	}
+	if len(conf.servers) == 0 {
+		conf.servers = defaultNS
+	}
+	if len(conf.search) == 0 {
+		conf.search = dnsDefaultSearch()
+	}
+	return conf
+}
+
+//go:linkname defaultNS net.defaultNS
+var defaultNS []string
+
+func dnsDefaultSearch() []string {
+	hn, err := os.Hostname()
+	if err != nil {
+		return nil
+	}
+	if i := strings.IndexRune(hn, '.'); i >= 0 && i < len(hn)-1 {
+		return []string{ensureRooted(hn[i+1:])}
+	}
+	return nil
+}
+
+func ensureRooted(s string) string {
+	if len(s) > 0 && s[len(s)-1] == '.' {
+		return s
+	}
+	return s + "."
+}
+
+const big = 0xFFFFFF
+
+func dtoi(s string) (n int, i int, ok bool) {
+	n = 0
+	for i = 0; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
+		n = n*10 + int(s[i]-'0')
+		if n >= big {
+			return big, i, false
+		}
+	}
+	if i == 0 {
+		return 0, 0, false
+	}
+	return n, i, true
+}

dns/transport/local/resolv_windows.go

@@ -0,0 +1,100 @@
+package local
+
+import (
+	"net"
+	"net/netip"
+	"os"
+	"syscall"
+	"time"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+func dnsReadConfig(_ string) *dnsConfig {
+	conf := &dnsConfig{
+		ndots:    1,
+		timeout:  5 * time.Second,
+		attempts: 2,
+	}
+	defer func() {
+		if len(conf.servers) == 0 {
+			conf.servers = defaultNS
+		}
+	}()
+	aas, err := adapterAddresses()
+	if err != nil {
+		return nil
+	}
+
+	for _, aa := range aas {
+		// Only take interfaces whose OperStatus is IfOperStatusUp(0x01) into DNS configs.
+		if aa.OperStatus != windows.IfOperStatusUp {
+			continue
+		}
+
+		// Only take interfaces which have at least one gateway
+		if aa.FirstGatewayAddress == nil {
+			continue
+		}
+
+		for dns := aa.FirstDnsServerAddress; dns != nil; dns = dns.Next {
+			sa, err := dns.Address.Sockaddr.Sockaddr()
+			if err != nil {
+				continue
+			}
+			var ip netip.Addr
+			switch sa := sa.(type) {
+			case *syscall.SockaddrInet4:
+				ip = netip.AddrFrom4([4]byte{sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3]})
+			case *syscall.SockaddrInet6:
+				var addr16 [16]byte
+				copy(addr16[:], sa.Addr[:])
+				if addr16[0] == 0xfe && addr16[1] == 0xc0 {
+					// fec0/10 IPv6 addresses are site local anycast DNS
+					// addresses Microsoft sets by default if no other
+					// IPv6 DNS address is set. Site local anycast is
+					// deprecated since 2004, see
+					// https://datatracker.ietf.org/doc/html/rfc3879
+					continue
+				}
+				ip = netip.AddrFrom16(addr16)
+			default:
+				// Unexpected type.
+				continue
+			}
+			conf.servers = append(conf.servers, net.JoinHostPort(ip.String(), "53"))
+		}
+	}
+	return conf
+}
+
+//go:linkname defaultNS net.defaultNS
+var defaultNS []string
+
+func adapterAddresses() ([]*windows.IpAdapterAddresses, error) {
+	var b []byte
+	l := uint32(15000) // recommended initial size
+	for {
+		b = make([]byte, l)
+		const flags = windows.GAA_FLAG_INCLUDE_PREFIX | windows.GAA_FLAG_INCLUDE_GATEWAYS
+		err := windows.GetAdaptersAddresses(syscall.AF_UNSPEC, flags, 0, (*windows.IpAdapterAddresses)(unsafe.Pointer(&b[0])), &l)
+		if err == nil {
+			if l == 0 {
+				return nil, nil
+			}
+			break
+		}
+		if err.(syscall.Errno) != syscall.ERROR_BUFFER_OVERFLOW {
+			return nil, os.NewSyscallError("getadaptersaddresses", err)
+		}
+		if l <= uint32(len(b)) {
+			return nil, os.NewSyscallError("getadaptersaddresses", err)
+		}
+	}
+	var aas []*windows.IpAdapterAddresses
+	for aa := (*windows.IpAdapterAddresses)(unsafe.Pointer(&b[0])); aa != nil; aa = aa.Next {
+		aas = append(aas, aa)
+	}
+	return aas, nil
+}

dns/transport/predefined.go

@@ -0,0 +1,83 @@
+package transport
+
+import (
+	"context"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common"
+	E "github.com/sagernet/sing/common/exceptions"
+
+	mDNS "github.com/miekg/dns"
+)
+
+var _ adapter.DNSTransport = (*PredefinedTransport)(nil)
+
+func RegisterPredefined(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.PredefinedDNSServerOptions](registry, C.DNSTypePreDefined, NewPredefined)
+}
+
+type PredefinedTransport struct {
+	dns.TransportAdapter
+	responses []*predefinedResponse
+}
+
+type predefinedResponse struct {
+	questions []mDNS.Question
+	answer    *mDNS.Msg
+}
+
+func NewPredefined(ctx context.Context, logger log.ContextLogger, tag string, options option.PredefinedDNSServerOptions) (adapter.DNSTransport, error) {
+	var responses []*predefinedResponse
+	for _, response := range options.Responses {
+		questions, msg, err := response.Build()
+		if err != nil {
+			return nil, err
+		}
+		responses = append(responses, &predefinedResponse{
+			questions: questions,
+			answer:    msg,
+		})
+	}
+	if len(responses) == 0 {
+		return nil, E.New("empty predefined responses")
+	}
+	return &PredefinedTransport{
+		TransportAdapter: dns.NewTransportAdapter(C.DNSTypePreDefined, tag, nil),
+		responses:        responses,
+	}, nil
+}
+
+func (t *PredefinedTransport) Reset() {
+}
+
+func (t *PredefinedTransport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	for _, response := range t.responses {
+		for _, question := range response.questions {
+			if func() bool {
+				if question.Name == "" && question.Qtype == mDNS.TypeNone {
+					return true
+				} else if question.Name == "" {
+					return common.Any(message.Question, func(it mDNS.Question) bool {
+						return it.Qtype == question.Qtype
+					})
+				} else if question.Qtype == mDNS.TypeNone {
+					return common.Any(message.Question, func(it mDNS.Question) bool {
+						return it.Name == question.Name
+					})
+				} else {
+					return common.Contains(message.Question, question)
+				}
+			}() {
+				copyAnswer := *response.answer
+				copyAnswer.Id = message.Id
+				copyAnswer.Question = message.Question
+				return &copyAnswer, nil
+			}
+		}
+	}
+	return nil, dns.RCodeNameError
+}

dns/transport/quic/http3.go

@@ -0,0 +1,167 @@
+package quic
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strconv"
+
+	"github.com/sagernet/quic-go"
+	"github.com/sagernet/quic-go/http3"
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/tls"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/dns/transport"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/buf"
+	"github.com/sagernet/sing/common/bufio"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+	sHTTP "github.com/sagernet/sing/protocol/http"
+
+	mDNS "github.com/miekg/dns"
+)
+
+var _ adapter.DNSTransport = (*HTTP3Transport)(nil)
+
+func RegisterHTTP3Transport(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.RemoteHTTPSDNSServerOptions](registry, C.DNSTypeHTTP3, NewHTTP3)
+}
+
+type HTTP3Transport struct {
+	dns.TransportAdapter
+	logger      logger.ContextLogger
+	dialer      N.Dialer
+	destination *url.URL
+	headers     http.Header
+	transport   *http3.Transport
+}
+
+func NewHTTP3(ctx context.Context, logger log.ContextLogger, tag string, options option.RemoteHTTPSDNSServerOptions) (adapter.DNSTransport, error) {
+	transportDialer, err := dns.NewRemoteDialer(ctx, options.RemoteDNSServerOptions)
+	if err != nil {
+		return nil, err
+	}
+	tlsOptions := common.PtrValueOrDefault(options.TLS)
+	tlsOptions.Enabled = true
+	tlsConfig, err := tls.NewClient(ctx, options.Server, tlsOptions)
+	if err != nil {
+		return nil, err
+	}
+	stdConfig, err := tlsConfig.Config()
+	if err != nil {
+		return nil, err
+	}
+	headers := options.Headers.Build()
+	host := headers.Get("Host")
+	if host != "" {
+		headers.Del("Host")
+	} else {
+		if tlsConfig.ServerName() != "" {
+			host = tlsConfig.ServerName()
+		} else {
+			host = options.Server
+		}
+	}
+	destinationURL := url.URL{
+		Scheme: "https",
+		Host:   host,
+	}
+	if destinationURL.Host == "" {
+		destinationURL.Host = options.Server
+	}
+	if options.ServerPort != 0 && options.ServerPort != 443 {
+		destinationURL.Host = net.JoinHostPort(destinationURL.Host, strconv.Itoa(int(options.ServerPort)))
+	}
+	path := options.Path
+	if path == "" {
+		path = "/dns-query"
+	}
+	err = sHTTP.URLSetPath(&destinationURL, path)
+	if err != nil {
+		return nil, err
+	}
+	serverAddr := options.ServerOptions.Build()
+	if serverAddr.Port == 0 {
+		serverAddr.Port = 443
+	}
+	return &HTTP3Transport{
+		TransportAdapter: dns.NewTransportAdapterWithRemoteOptions(C.DNSTypeHTTP3, tag, options.RemoteDNSServerOptions),
+		logger:           logger,
+		dialer:           transportDialer,
+		destination:      &destinationURL,
+		headers:          headers,
+		transport: &http3.Transport{
+			Dial: func(ctx context.Context, addr string, tlsCfg *tls.STDConfig, cfg *quic.Config) (quic.EarlyConnection, error) {
+				destinationAddr := M.ParseSocksaddr(addr)
+				conn, dialErr := transportDialer.DialContext(ctx, N.NetworkUDP, destinationAddr)
+				if dialErr != nil {
+					return nil, dialErr
+				}
+				return quic.DialEarly(ctx, bufio.NewUnbindPacketConn(conn), conn.RemoteAddr(), tlsCfg, cfg)
+			},
+			TLSClientConfig: stdConfig,
+		},
+	}, nil
+}
+
+func (t *HTTP3Transport) Reset() {
+	t.transport.Close()
+}
+
+func (t *HTTP3Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	exMessage := *message
+	exMessage.Id = 0
+	exMessage.Compress = true
+	requestBuffer := buf.NewSize(1 + message.Len())
+	rawMessage, err := exMessage.PackBuffer(requestBuffer.FreeBytes())
+	if err != nil {
+		requestBuffer.Release()
+		return nil, err
+	}
+	request, err := http.NewRequestWithContext(ctx, http.MethodPost, t.destination.String(), bytes.NewReader(rawMessage))
+	if err != nil {
+		requestBuffer.Release()
+		return nil, err
+	}
+	request.Header = t.headers.Clone()
+	request.Header.Set("Content-Type", transport.MimeType)
+	request.Header.Set("Accept", transport.MimeType)
+	response, err := t.transport.RoundTrip(request)
+	requestBuffer.Release()
+	if err != nil {
+		return nil, err
+	}
+	defer response.Body.Close()
+	if response.StatusCode != http.StatusOK {
+		return nil, E.New("unexpected status: ", response.Status)
+	}
+	var responseMessage mDNS.Msg
+	if response.ContentLength > 0 {
+		responseBuffer := buf.NewSize(int(response.ContentLength))
+		_, err = responseBuffer.ReadFullFrom(response.Body, int(response.ContentLength))
+		if err != nil {
+			return nil, err
+		}
+		err = responseMessage.Unpack(responseBuffer.Bytes())
+		responseBuffer.Release()
+	} else {
+		rawMessage, err = io.ReadAll(response.Body)
+		if err != nil {
+			return nil, err
+		}
+		err = responseMessage.Unpack(rawMessage)
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &responseMessage, nil
+}

dns/transport/quic/quic.go

@@ -0,0 +1,174 @@
+package quic
+
+import (
+	"context"
+	"errors"
+	"sync"
+
+	"github.com/sagernet/quic-go"
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/tls"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/dns/transport"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	sQUIC "github.com/sagernet/sing-quic"
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/bufio"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+
+	mDNS "github.com/miekg/dns"
+)
+
+var _ adapter.DNSTransport = (*Transport)(nil)
+
+func RegisterTransport(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.RemoteTLSDNSServerOptions](registry, C.DNSTypeQUIC, NewQUIC)
+}
+
+type Transport struct {
+	dns.TransportAdapter
+	ctx        context.Context
+	logger     logger.ContextLogger
+	dialer     N.Dialer
+	serverAddr M.Socksaddr
+	tlsConfig  tls.Config
+	access     sync.Mutex
+	connection quic.EarlyConnection
+}
+
+func NewQUIC(ctx context.Context, logger log.ContextLogger, tag string, options option.RemoteTLSDNSServerOptions) (adapter.DNSTransport, error) {
+	transportDialer, err := dns.NewRemoteDialer(ctx, options.RemoteDNSServerOptions)
+	if err != nil {
+		return nil, err
+	}
+	tlsOptions := common.PtrValueOrDefault(options.TLS)
+	tlsOptions.Enabled = true
+	tlsConfig, err := tls.NewClient(ctx, options.Server, tlsOptions)
+	if err != nil {
+		return nil, err
+	}
+	if len(tlsConfig.NextProtos()) == 0 {
+		tlsConfig.SetNextProtos([]string{"doq"})
+	}
+	serverAddr := options.ServerOptions.Build()
+	if serverAddr.Port == 0 {
+		serverAddr.Port = 853
+	}
+	return &Transport{
+		TransportAdapter: dns.NewTransportAdapterWithRemoteOptions(C.DNSTypeQUIC, tag, options.RemoteDNSServerOptions),
+		ctx:              ctx,
+		logger:           logger,
+		dialer:           transportDialer,
+		serverAddr:       serverAddr,
+		tlsConfig:        tlsConfig,
+	}, nil
+}
+
+func (t *Transport) Reset() {
+	t.access.Lock()
+	defer t.access.Unlock()
+	connection := t.connection
+	if connection != nil {
+		connection.CloseWithError(0, "")
+	}
+}
+
+func (t *Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	var (
+		conn     quic.Connection
+		err      error
+		response *mDNS.Msg
+	)
+	for i := 0; i < 2; i++ {
+		conn, err = t.openConnection()
+		if err != nil {
+			return nil, err
+		}
+		response, err = t.exchange(ctx, message, conn)
+		if err == nil {
+			return response, nil
+		} else if !isQUICRetryError(err) {
+			return nil, err
+		} else {
+			conn.CloseWithError(quic.ApplicationErrorCode(0), "")
+			continue
+		}
+	}
+	return nil, err
+}
+
+func (t *Transport) openConnection() (quic.EarlyConnection, error) {
+	connection := t.connection
+	if connection != nil && !common.Done(connection.Context()) {
+		return connection, nil
+	}
+	t.access.Lock()
+	defer t.access.Unlock()
+	connection = t.connection
+	if connection != nil && !common.Done(connection.Context()) {
+		return connection, nil
+	}
+	conn, err := t.dialer.DialContext(t.ctx, N.NetworkUDP, t.serverAddr)
+	if err != nil {
+		return nil, err
+	}
+	earlyConnection, err := sQUIC.DialEarly(
+		t.ctx,
+		bufio.NewUnbindPacketConn(conn),
+		t.serverAddr.UDPAddr(),
+		t.tlsConfig,
+		nil,
+	)
+	if err != nil {
+		return nil, err
+	}
+	t.connection = earlyConnection
+	return earlyConnection, nil
+}
+
+func (t *Transport) exchange(ctx context.Context, message *mDNS.Msg, conn quic.Connection) (*mDNS.Msg, error) {
+	stream, err := conn.OpenStreamSync(ctx)
+	if err != nil {
+		return nil, err
+	}
+	defer stream.Close()
+	defer stream.CancelRead(0)
+	err = transport.WriteMessage(stream, 0, message)
+	if err != nil {
+		return nil, err
+	}
+	return transport.ReadMessage(stream)
+}
+
+// https://github.com/AdguardTeam/dnsproxy/blob/fd1868577652c639cce3da00e12ca548f421baf1/upstream/upstream_quic.go#L394
+func isQUICRetryError(err error) (ok bool) {
+	var qAppErr *quic.ApplicationError
+	if errors.As(err, &qAppErr) && qAppErr.ErrorCode == 0 {
+		return true
+	}
+
+	var qIdleErr *quic.IdleTimeoutError
+	if errors.As(err, &qIdleErr) {
+		return true
+	}
+
+	var resetErr *quic.StatelessResetError
+	if errors.As(err, &resetErr) {
+		return true
+	}
+
+	var qTransportError *quic.TransportError
+	if errors.As(err, &qTransportError) && qTransportError.ErrorCode == quic.NoError {
+		return true
+	}
+
+	if errors.Is(err, quic.Err0RTTRejected) {
+		return true
+	}
+
+	return false
+}

dns/transport/tcp.go

@@ -0,0 +1,99 @@
+package transport
+
+import (
+	"context"
+	"encoding/binary"
+	"io"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/buf"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+
+	mDNS "github.com/miekg/dns"
+)
+
+var _ adapter.DNSTransport = (*TCPTransport)(nil)
+
+func RegisterTCP(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.RemoteDNSServerOptions](registry, C.DNSTypeTCP, NewTCP)
+}
+
+type TCPTransport struct {
+	dns.TransportAdapter
+	dialer     N.Dialer
+	serverAddr M.Socksaddr
+}
+
+func NewTCP(ctx context.Context, logger log.ContextLogger, tag string, options option.RemoteDNSServerOptions) (adapter.DNSTransport, error) {
+	transportDialer, err := dns.NewRemoteDialer(ctx, options)
+	if err != nil {
+		return nil, err
+	}
+	serverAddr := options.ServerOptions.Build()
+	if serverAddr.Port == 0 {
+		serverAddr.Port = 53
+	}
+	return &TCPTransport{
+		TransportAdapter: dns.NewTransportAdapterWithRemoteOptions(C.DNSTypeTCP, tag, options),
+		dialer:           transportDialer,
+		serverAddr:       serverAddr,
+	}, nil
+}
+
+func (t *TCPTransport) Reset() {
+}
+
+func (t *TCPTransport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	conn, err := t.dialer.DialContext(ctx, N.NetworkTCP, t.serverAddr)
+	if err != nil {
+		return nil, err
+	}
+	defer conn.Close()
+	err = WriteMessage(conn, 0, message)
+	if err != nil {
+		return nil, err
+	}
+	return ReadMessage(conn)
+}
+
+func ReadMessage(reader io.Reader) (*mDNS.Msg, error) {
+	var responseLen uint16
+	err := binary.Read(reader, binary.BigEndian, &responseLen)
+	if err != nil {
+		return nil, err
+	}
+	if responseLen < 10 {
+		return nil, mDNS.ErrShortRead
+	}
+	buffer := buf.NewSize(int(responseLen))
+	defer buffer.Release()
+	_, err = buffer.ReadFullFrom(reader, int(responseLen))
+	if err != nil {
+		return nil, err
+	}
+	var message mDNS.Msg
+	err = message.Unpack(buffer.Bytes())
+	return &message, err
+}
+
+func WriteMessage(writer io.Writer, messageId uint16, message *mDNS.Msg) error {
+	requestLen := message.Len()
+	buffer := buf.NewSize(3 + requestLen)
+	defer buffer.Release()
+	common.Must(binary.Write(buffer, binary.BigEndian, uint16(requestLen)))
+	exMessage := *message
+	exMessage.Id = messageId
+	exMessage.Compress = true
+	rawMessage, err := exMessage.PackBuffer(buffer.FreeBytes())
+	if err != nil {
+		return err
+	}
+	buffer.Truncate(2 + len(rawMessage))
+	return common.Error(writer.Write(buffer.Bytes()))
+}

dns/transport/tls.go

@@ -0,0 +1,115 @@
+package transport
+
+import (
+	"context"
+	"sync"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/tls"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+	"github.com/sagernet/sing/common/x/list"
+
+	mDNS "github.com/miekg/dns"
+)
+
+var _ adapter.DNSTransport = (*TLSTransport)(nil)
+
+func RegisterTLS(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.RemoteTLSDNSServerOptions](registry, C.DNSTypeTLS, NewTLS)
+}
+
+type TLSTransport struct {
+	dns.TransportAdapter
+	logger      logger.ContextLogger
+	dialer      N.Dialer
+	serverAddr  M.Socksaddr
+	tlsConfig   tls.Config
+	access      sync.Mutex
+	connections list.List[*tlsDNSConn]
+}
+
+type tlsDNSConn struct {
+	tls.Conn
+	queryId uint16
+}
+
+func NewTLS(ctx context.Context, logger log.ContextLogger, tag string, options option.RemoteTLSDNSServerOptions) (adapter.DNSTransport, error) {
+	transportDialer, err := dns.NewRemoteDialer(ctx, options.RemoteDNSServerOptions)
+	if err != nil {
+		return nil, err
+	}
+	tlsOptions := common.PtrValueOrDefault(options.TLS)
+	tlsOptions.Enabled = true
+	tlsConfig, err := tls.NewClient(ctx, options.Server, tlsOptions)
+	if err != nil {
+		return nil, err
+	}
+	serverAddr := options.ServerOptions.Build()
+	if serverAddr.Port == 0 {
+		serverAddr.Port = 853
+	}
+	return &TLSTransport{
+		TransportAdapter: dns.NewTransportAdapterWithRemoteOptions(C.DNSTypeTLS, tag, options.RemoteDNSServerOptions),
+		logger:           logger,
+		dialer:           transportDialer,
+		serverAddr:       serverAddr,
+		tlsConfig:        tlsConfig,
+	}, nil
+}
+
+func (t *TLSTransport) Reset() {
+	t.access.Lock()
+	defer t.access.Unlock()
+	for connection := t.connections.Front(); connection != nil; connection = connection.Next() {
+		connection.Value.Close()
+	}
+	t.connections.Init()
+}
+
+func (t *TLSTransport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	t.access.Lock()
+	conn := t.connections.PopFront()
+	t.access.Unlock()
+	if conn != nil {
+		response, err := t.exchange(message, conn)
+		if err == nil {
+			return response, nil
+		}
+	}
+	tcpConn, err := t.dialer.DialContext(ctx, N.NetworkTCP, t.serverAddr)
+	if err != nil {
+		return nil, err
+	}
+	tlsConn, err := tls.ClientHandshake(ctx, tcpConn, t.tlsConfig)
+	if err != nil {
+		tcpConn.Close()
+		return nil, err
+	}
+	return t.exchange(message, &tlsDNSConn{Conn: tlsConn})
+}
+
+func (t *TLSTransport) exchange(message *mDNS.Msg, conn *tlsDNSConn) (*mDNS.Msg, error) {
+	conn.queryId++
+	err := WriteMessage(conn, conn.queryId, message)
+	if err != nil {
+		conn.Close()
+		return nil, E.Cause(err, "write request")
+	}
+	response, err := ReadMessage(conn)
+	if err != nil {
+		conn.Close()
+		return nil, E.Cause(err, "read response")
+	}
+	t.access.Lock()
+	t.connections.PushBack(conn)
+	t.access.Unlock()
+	return response, nil
+}

dns/transport/udp.go

@@ -0,0 +1,223 @@
+package transport
+
+import (
+	"context"
+	"net"
+	"os"
+	"sync"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common/buf"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+
+	mDNS "github.com/miekg/dns"
+)
+
+var _ adapter.DNSTransport = (*UDPTransport)(nil)
+
+func RegisterUDP(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.RemoteDNSServerOptions](registry, C.DNSTypeUDP, NewUDP)
+}
+
+type UDPTransport struct {
+	dns.TransportAdapter
+	logger       logger.ContextLogger
+	dialer       N.Dialer
+	serverAddr   M.Socksaddr
+	udpSize      int
+	tcpTransport *TCPTransport
+	access       sync.Mutex
+	conn         *dnsConnection
+	done         chan struct{}
+}
+
+func NewUDP(ctx context.Context, logger log.ContextLogger, tag string, options option.RemoteDNSServerOptions) (adapter.DNSTransport, error) {
+	transportDialer, err := dns.NewRemoteDialer(ctx, options)
+	if err != nil {
+		return nil, err
+	}
+	serverAddr := options.ServerOptions.Build()
+	if serverAddr.Port == 0 {
+		serverAddr.Port = 53
+	}
+	return NewUDPRaw(logger, dns.NewTransportAdapterWithRemoteOptions(C.DNSTypeUDP, tag, options), transportDialer, serverAddr), nil
+}
+
+func NewUDPRaw(logger logger.ContextLogger, adapter dns.TransportAdapter, dialer N.Dialer, serverAddr M.Socksaddr) *UDPTransport {
+	return &UDPTransport{
+		TransportAdapter: adapter,
+		logger:           logger,
+		dialer:           dialer,
+		serverAddr:       serverAddr,
+		udpSize:          512,
+		tcpTransport: &TCPTransport{
+			dialer:     dialer,
+			serverAddr: serverAddr,
+		},
+		done: make(chan struct{}),
+	}
+}
+
+func (t *UDPTransport) Reset() {
+	t.access.Lock()
+	defer t.access.Unlock()
+	close(t.done)
+	t.done = make(chan struct{})
+}
+
+func (t *UDPTransport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	response, err := t.exchange(ctx, message)
+	if err != nil {
+		return nil, err
+	}
+	if response.Truncated {
+		t.logger.InfoContext(ctx, "response truncated, retrying with TCP")
+		return t.tcpTransport.Exchange(ctx, message)
+	}
+	return response, nil
+}
+
+func (t *UDPTransport) exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	conn, err := t.open(ctx)
+	if err != nil {
+		return nil, err
+	}
+	if edns0Opt := message.IsEdns0(); edns0Opt != nil {
+		if udpSize := int(edns0Opt.UDPSize()); udpSize > t.udpSize {
+			t.udpSize = udpSize
+		}
+	}
+	buffer := buf.NewSize(1 + message.Len())
+	defer buffer.Release()
+	exMessage := *message
+	exMessage.Compress = true
+	messageId := message.Id
+	callback := &dnsCallback{
+		done: make(chan struct{}),
+	}
+	conn.access.Lock()
+	conn.queryId++
+	exMessage.Id = conn.queryId
+	conn.callbacks[exMessage.Id] = callback
+	conn.access.Unlock()
+	defer func() {
+		conn.access.Lock()
+		delete(conn.callbacks, messageId)
+		conn.access.Unlock()
+		callback.access.Lock()
+		select {
+		case <-callback.done:
+		default:
+			close(callback.done)
+		}
+		callback.access.Unlock()
+	}()
+	rawMessage, err := exMessage.PackBuffer(buffer.FreeBytes())
+	if err != nil {
+		return nil, err
+	}
+	_, err = conn.Write(rawMessage)
+	if err != nil {
+		conn.Close(err)
+		return nil, err
+	}
+	select {
+	case <-callback.done:
+		callback.message.Id = messageId
+		return callback.message, nil
+	case <-conn.done:
+		return nil, conn.err
+	case <-t.done:
+		return nil, os.ErrClosed
+	case <-ctx.Done():
+		conn.Close(ctx.Err())
+		return nil, ctx.Err()
+	}
+}
+
+func (t *UDPTransport) open(ctx context.Context) (*dnsConnection, error) {
+	t.access.Lock()
+	defer t.access.Unlock()
+	if t.conn != nil {
+		select {
+		case <-t.conn.done:
+		default:
+			return t.conn, nil
+		}
+	}
+	conn, err := t.dialer.DialContext(ctx, N.NetworkUDP, t.serverAddr)
+	if err != nil {
+		return nil, err
+	}
+	dnsConn := &dnsConnection{
+		Conn:      conn,
+		done:      make(chan struct{}),
+		callbacks: make(map[uint16]*dnsCallback),
+	}
+	go t.recvLoop(dnsConn)
+	t.conn = dnsConn
+	return dnsConn, nil
+}
+
+func (t *UDPTransport) recvLoop(conn *dnsConnection) {
+	for {
+		buffer := buf.NewSize(t.udpSize)
+		_, err := buffer.ReadOnceFrom(conn)
+		if err != nil {
+			buffer.Release()
+			conn.Close(err)
+			return
+		}
+		var message mDNS.Msg
+		err = message.Unpack(buffer.Bytes())
+		buffer.Release()
+		if err != nil {
+			conn.Close(err)
+			return
+		}
+		conn.access.RLock()
+		callback, loaded := conn.callbacks[message.Id]
+		conn.access.RUnlock()
+		if !loaded {
+			continue
+		}
+		callback.access.Lock()
+		select {
+		case <-callback.done:
+		default:
+			callback.message = &message
+			close(callback.done)
+		}
+		callback.access.Unlock()
+	}
+}
+
+type dnsConnection struct {
+	net.Conn
+	access    sync.RWMutex
+	done      chan struct{}
+	closeOnce sync.Once
+	err       error
+	queryId   uint16
+	callbacks map[uint16]*dnsCallback
+}
+
+func (c *dnsConnection) Close(err error) {
+	c.closeOnce.Do(func() {
+		close(c.done)
+		c.err = err
+	})
+	c.Conn.Close()
+}
+
+type dnsCallback struct {
+	access  sync.Mutex
+	message *mDNS.Msg
+	done    chan struct{}
+}

dns/transport_adapter.go

@@ -0,0 +1,70 @@
+package dns
+
+import (
+	"net/netip"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/option"
+)
+
+var _ adapter.LegacyDNSTransport = (*TransportAdapter)(nil)
+
+type TransportAdapter struct {
+	transportType string
+	transportTag  string
+	dependencies  []string
+	strategy      C.DomainStrategy
+	clientSubnet  netip.Prefix
+}
+
+func NewTransportAdapter(transportType string, transportTag string, dependencies []string) TransportAdapter {
+	return TransportAdapter{
+		transportType: transportType,
+		transportTag:  transportTag,
+		dependencies:  dependencies,
+	}
+}
+
+func NewTransportAdapterWithLocalOptions(transportType string, transportTag string, localOptions option.LocalDNSServerOptions) TransportAdapter {
+	return TransportAdapter{
+		transportType: transportType,
+		transportTag:  transportTag,
+		strategy:      C.DomainStrategy(localOptions.LegacyStrategy),
+		clientSubnet:  localOptions.LegacyClientSubnet,
+	}
+}
+
+func NewTransportAdapterWithRemoteOptions(transportType string, transportTag string, remoteOptions option.RemoteDNSServerOptions) TransportAdapter {
+	var dependencies []string
+	if remoteOptions.AddressResolver != "" {
+		dependencies = []string{remoteOptions.AddressResolver}
+	}
+	return TransportAdapter{
+		transportType: transportType,
+		transportTag:  transportTag,
+		dependencies:  dependencies,
+		strategy:      C.DomainStrategy(remoteOptions.LegacyStrategy),
+		clientSubnet:  remoteOptions.LegacyClientSubnet,
+	}
+}
+
+func (a *TransportAdapter) Type() string {
+	return a.transportType
+}
+
+func (a *TransportAdapter) Tag() string {
+	return a.transportTag
+}
+
+func (a *TransportAdapter) Dependencies() []string {
+	return a.dependencies
+}
+
+func (a *TransportAdapter) LegacyStrategy() C.DomainStrategy {
+	return a.strategy
+}
+
+func (a *TransportAdapter) LegacyClientSubnet() netip.Prefix {
+	return a.clientSubnet
+}

dns/transport_dialer.go

@@ -0,0 +1,93 @@
+package dns
+
+import (
+	"context"
+	"net"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/dialer"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/option"
+	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/service"
+)
+
+func NewLocalDialer(ctx context.Context, options option.LocalDNSServerOptions) (N.Dialer, error) {
+	if options.LegacyDefaultDialer {
+		return dialer.NewDefaultOutbound(ctx), nil
+	} else {
+		return dialer.New(ctx, options.DialerOptions)
+	}
+}
+
+func NewRemoteDialer(ctx context.Context, options option.RemoteDNSServerOptions) (N.Dialer, error) {
+	transportDialer, err := NewLocalDialer(ctx, options.LocalDNSServerOptions)
+	if err != nil {
+		return nil, err
+	}
+	if options.AddressResolver != "" {
+		transport := service.FromContext[adapter.DNSTransportManager](ctx)
+		resolverTransport, loaded := transport.Transport(options.AddressResolver)
+		if !loaded {
+			return nil, E.New("address resolver not found: ", options.AddressResolver)
+		}
+		transportDialer = NewTransportDialer(transportDialer, service.FromContext[adapter.DNSRouter](ctx), resolverTransport, C.DomainStrategy(options.AddressStrategy), time.Duration(options.AddressFallbackDelay))
+	} else if M.IsDomainName(options.Server) {
+		return nil, E.New("missing address resolver for server: ", options.Server)
+	}
+	return transportDialer, nil
+}
+
+type TransportDialer struct {
+	dialer        N.Dialer
+	dnsRouter     adapter.DNSRouter
+	transport     adapter.DNSTransport
+	strategy      C.DomainStrategy
+	fallbackDelay time.Duration
+}
+
+func NewTransportDialer(dialer N.Dialer, dnsRouter adapter.DNSRouter, transport adapter.DNSTransport, strategy C.DomainStrategy, fallbackDelay time.Duration) *TransportDialer {
+	return &TransportDialer{
+		dialer,
+		dnsRouter,
+		transport,
+		strategy,
+		fallbackDelay,
+	}
+}
+
+func (d *TransportDialer) DialContext(ctx context.Context, network string, destination M.Socksaddr) (net.Conn, error) {
+	if destination.IsIP() {
+		return d.dialer.DialContext(ctx, network, destination)
+	}
+	addresses, err := d.dnsRouter.Lookup(ctx, destination.Fqdn, adapter.DNSQueryOptions{
+		Transport: d.transport,
+		Strategy:  d.strategy,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return N.DialParallel(ctx, d.dialer, network, destination, addresses, d.strategy == C.DomainStrategyPreferIPv6, d.fallbackDelay)
+}
+
+func (d *TransportDialer) ListenPacket(ctx context.Context, destination M.Socksaddr) (net.PacketConn, error) {
+	if destination.IsIP() {
+		return d.dialer.ListenPacket(ctx, destination)
+	}
+	addresses, err := d.dnsRouter.Lookup(ctx, destination.Fqdn, adapter.DNSQueryOptions{
+		Transport: d.transport,
+		Strategy:  d.strategy,
+	})
+	if err != nil {
+		return nil, err
+	}
+	conn, _, err := N.ListenSerial(ctx, d.dialer, destination, addresses)
+	return conn, err
+}
+
+func (d *TransportDialer) Upstream() any {
+	return d.dialer
+}

dns/transport_manager.go

@@ -0,0 +1,288 @@
+package dns
+
+import (
+	"context"
+	"io"
+	"os"
+	"strings"
+	"sync"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/taskmonitor"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing/common"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+)
+
+var _ adapter.DNSTransportManager = (*TransportManager)(nil)
+
+type TransportManager struct {
+	logger                   log.ContextLogger
+	registry                 adapter.DNSTransportRegistry
+	outbound                 adapter.OutboundManager
+	defaultTag               string
+	access                   sync.RWMutex
+	started                  bool
+	stage                    adapter.StartStage
+	transports               []adapter.DNSTransport
+	transportByTag           map[string]adapter.DNSTransport
+	dependByTag              map[string][]string
+	defaultTransport         adapter.DNSTransport
+	defaultTransportFallback adapter.DNSTransport
+	fakeIPTransport          adapter.FakeIPTransport
+}
+
+func NewTransportManager(logger logger.ContextLogger, registry adapter.DNSTransportRegistry, outbound adapter.OutboundManager, defaultTag string) *TransportManager {
+	return &TransportManager{
+		logger:         logger,
+		registry:       registry,
+		outbound:       outbound,
+		defaultTag:     defaultTag,
+		transportByTag: make(map[string]adapter.DNSTransport),
+		dependByTag:    make(map[string][]string),
+	}
+}
+
+func (m *TransportManager) Initialize(defaultTransportFallback adapter.DNSTransport) {
+	m.defaultTransportFallback = defaultTransportFallback
+}
+
+func (m *TransportManager) Start(stage adapter.StartStage) error {
+	m.access.Lock()
+	if m.started && m.stage >= stage {
+		panic("already started")
+	}
+	m.started = true
+	m.stage = stage
+	outbounds := m.transports
+	m.access.Unlock()
+	if stage == adapter.StartStateStart {
+		return m.startTransports(m.transports)
+	} else {
+		for _, outbound := range outbounds {
+			err := adapter.LegacyStart(outbound, stage)
+			if err != nil {
+				return E.Cause(err, stage, " dns/", outbound.Type(), "[", outbound.Tag(), "]")
+			}
+		}
+	}
+	return nil
+}
+
+func (m *TransportManager) startTransports(transports []adapter.DNSTransport) error {
+	monitor := taskmonitor.New(m.logger, C.StartTimeout)
+	started := make(map[string]bool)
+	for {
+		canContinue := false
+	startOne:
+		for _, transportToStart := range transports {
+			transportTag := transportToStart.Tag()
+			if started[transportTag] {
+				continue
+			}
+			dependencies := transportToStart.Dependencies()
+			for _, dependency := range dependencies {
+				if !started[dependency] {
+					continue startOne
+				}
+			}
+			started[transportTag] = true
+			canContinue = true
+			if starter, isStarter := transportToStart.(adapter.Lifecycle); isStarter {
+				monitor.Start("start dns/", transportToStart.Type(), "[", transportTag, "]")
+				err := starter.Start(adapter.StartStateStart)
+				monitor.Finish()
+				if err != nil {
+					return E.Cause(err, "start dns/", transportToStart.Type(), "[", transportTag, "]")
+				}
+			}
+		}
+		if len(started) == len(transports) {
+			break
+		}
+		if canContinue {
+			continue
+		}
+		currentTransport := common.Find(transports, func(it adapter.DNSTransport) bool {
+			return !started[it.Tag()]
+		})
+		var lintTransport func(oTree []string, oCurrent adapter.DNSTransport) error
+		lintTransport = func(oTree []string, oCurrent adapter.DNSTransport) error {
+			problemTransportTag := common.Find(oCurrent.Dependencies(), func(it string) bool {
+				return !started[it]
+			})
+			if common.Contains(oTree, problemTransportTag) {
+				return E.New("circular server dependency: ", strings.Join(oTree, " -> "), " -> ", problemTransportTag)
+			}
+			m.access.Lock()
+			problemTransport := m.transportByTag[problemTransportTag]
+			m.access.Unlock()
+			if problemTransport == nil {
+				return E.New("dependency[", problemTransportTag, "] not found for server[", oCurrent.Tag(), "]")
+			}
+			return lintTransport(append(oTree, problemTransportTag), problemTransport)
+		}
+		return lintTransport([]string{currentTransport.Tag()}, currentTransport)
+	}
+	return nil
+}
+
+func (m *TransportManager) Close() error {
+	monitor := taskmonitor.New(m.logger, C.StopTimeout)
+	m.access.Lock()
+	if !m.started {
+		m.access.Unlock()
+		return nil
+	}
+	m.started = false
+	transports := m.transports
+	m.transports = nil
+	m.access.Unlock()
+	var err error
+	for _, transport := range transports {
+		if closer, isCloser := transport.(io.Closer); isCloser {
+			monitor.Start("close server/", transport.Type(), "[", transport.Tag(), "]")
+			err = E.Append(err, closer.Close(), func(err error) error {
+				return E.Cause(err, "close server/", transport.Type(), "[", transport.Tag(), "]")
+			})
+			monitor.Finish()
+		}
+	}
+	return nil
+}
+
+func (m *TransportManager) Transports() []adapter.DNSTransport {
+	m.access.RLock()
+	defer m.access.RUnlock()
+	return m.transports
+}
+
+func (m *TransportManager) Transport(tag string) (adapter.DNSTransport, bool) {
+	m.access.RLock()
+	outbound, found := m.transportByTag[tag]
+	m.access.RUnlock()
+	return outbound, found
+}
+
+func (m *TransportManager) Default() adapter.DNSTransport {
+	m.access.RLock()
+	defer m.access.RUnlock()
+	if m.defaultTransport != nil {
+		return m.defaultTransport
+	} else {
+		return m.defaultTransportFallback
+	}
+}
+
+func (m *TransportManager) FakeIP() adapter.FakeIPTransport {
+	m.access.RLock()
+	defer m.access.RUnlock()
+	return m.fakeIPTransport
+}
+
+func (m *TransportManager) Remove(tag string) error {
+	m.access.Lock()
+	defer m.access.Unlock()
+	transport, found := m.transportByTag[tag]
+	if !found {
+		return os.ErrInvalid
+	}
+	delete(m.transportByTag, tag)
+	index := common.Index(m.transports, func(it adapter.DNSTransport) bool {
+		return it == transport
+	})
+	if index == -1 {
+		panic("invalid inbound index")
+	}
+	m.transports = append(m.transports[:index], m.transports[index+1:]...)
+	started := m.started
+	if m.defaultTransport == transport {
+		if len(m.transports) > 0 {
+			nextTransport := m.transports[0]
+			if nextTransport.Type() != C.DNSTypeFakeIP {
+				return E.New("default server cannot be fakeip")
+			}
+			m.defaultTransport = nextTransport
+			m.logger.Info("updated default server to ", m.defaultTransport.Tag())
+		} else {
+			m.defaultTransport = nil
+		}
+	}
+	dependBy := m.dependByTag[tag]
+	if len(dependBy) > 0 {
+		return E.New("server[", tag, "] is depended by ", strings.Join(dependBy, ", "))
+	}
+	dependencies := transport.Dependencies()
+	for _, dependency := range dependencies {
+		if len(m.dependByTag[dependency]) == 1 {
+			delete(m.dependByTag, dependency)
+		} else {
+			m.dependByTag[dependency] = common.Filter(m.dependByTag[dependency], func(it string) bool {
+				return it != tag
+			})
+		}
+	}
+	if started {
+		transport.Reset()
+	}
+	return nil
+}
+
+func (m *TransportManager) Create(ctx context.Context, logger log.ContextLogger, tag string, transportType string, options any) error {
+	if tag == "" {
+		return os.ErrInvalid
+	}
+	transport, err := m.registry.CreateDNSTransport(ctx, logger, tag, transportType, options)
+	if err != nil {
+		return err
+	}
+	m.access.Lock()
+	defer m.access.Unlock()
+	if m.started {
+		for _, stage := range adapter.ListStartStages {
+			err = adapter.LegacyStart(transport, stage)
+			if err != nil {
+				return E.Cause(err, stage, " dns/", transport.Type(), "[", transport.Tag(), "]")
+			}
+		}
+	}
+	if existsTransport, loaded := m.transportByTag[tag]; loaded {
+		if m.started {
+			err = common.Close(existsTransport)
+			if err != nil {
+				return E.Cause(err, "close dns/", existsTransport.Type(), "[", existsTransport.Tag(), "]")
+			}
+		}
+		existsIndex := common.Index(m.transports, func(it adapter.DNSTransport) bool {
+			return it == existsTransport
+		})
+		if existsIndex == -1 {
+			panic("invalid inbound index")
+		}
+		m.transports = append(m.transports[:existsIndex], m.transports[existsIndex+1:]...)
+	}
+	m.transports = append(m.transports, transport)
+	m.transportByTag[tag] = transport
+	dependencies := transport.Dependencies()
+	for _, dependency := range dependencies {
+		m.dependByTag[dependency] = append(m.dependByTag[dependency], tag)
+	}
+	if tag == m.defaultTag || (m.defaultTag == "" && m.defaultTransport == nil) {
+		if transport.Type() == C.DNSTypeFakeIP {
+			return E.New("default server cannot be fakeip")
+		}
+		m.defaultTransport = transport
+		if m.started {
+			m.logger.Info("updated default server to ", transport.Tag())
+		}
+	}
+	if transport.Type() == C.DNSTypeFakeIP {
+		if m.fakeIPTransport != nil {
+			return E.New("multiple fakeip server are not supported")
+		}
+		m.fakeIPTransport = transport.(adapter.FakeIPTransport)
+	}
+	return nil
+}

dns/transport_registry.go

@@ -0,0 +1,72 @@
+package dns
+
+import (
+	"context"
+	"sync"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing/common"
+	E "github.com/sagernet/sing/common/exceptions"
+)
+
+type TransportConstructorFunc[T any] func(ctx context.Context, logger log.ContextLogger, tag string, options T) (adapter.DNSTransport, error)
+
+func RegisterTransport[Options any](registry *TransportRegistry, transportType string, constructor TransportConstructorFunc[Options]) {
+	registry.register(transportType, func() any {
+		return new(Options)
+	}, func(ctx context.Context, logger log.ContextLogger, tag string, rawOptions any) (adapter.DNSTransport, error) {
+		var options *Options
+		if rawOptions != nil {
+			options = rawOptions.(*Options)
+		}
+		return constructor(ctx, logger, tag, common.PtrValueOrDefault(options))
+	})
+}
+
+var _ adapter.DNSTransportRegistry = (*TransportRegistry)(nil)
+
+type (
+	optionsConstructorFunc func() any
+	constructorFunc        func(ctx context.Context, logger log.ContextLogger, tag string, options any) (adapter.DNSTransport, error)
+)
+
+type TransportRegistry struct {
+	access       sync.Mutex
+	optionsType  map[string]optionsConstructorFunc
+	constructors map[string]constructorFunc
+}
+
+func NewTransportRegistry() *TransportRegistry {
+	return &TransportRegistry{
+		optionsType:  make(map[string]optionsConstructorFunc),
+		constructors: make(map[string]constructorFunc),
+	}
+}
+
+func (r *TransportRegistry) CreateOptions(transportType string) (any, bool) {
+	r.access.Lock()
+	defer r.access.Unlock()
+	optionsConstructor, loaded := r.optionsType[transportType]
+	if !loaded {
+		return nil, false
+	}
+	return optionsConstructor(), true
+}
+
+func (r *TransportRegistry) CreateDNSTransport(ctx context.Context, logger log.ContextLogger, tag string, transportType string, options any) (adapter.DNSTransport, error) {
+	r.access.Lock()
+	defer r.access.Unlock()
+	constructor, loaded := r.constructors[transportType]
+	if !loaded {
+		return nil, E.New("transport type not found: " + transportType)
+	}
+	return constructor(ctx, logger, tag, options)
+}
+
+func (r *TransportRegistry) register(transportType string, optionsConstructor optionsConstructorFunc, constructor constructorFunc) {
+	r.access.Lock()
+	defer r.access.Unlock()
+	r.optionsType[transportType] = optionsConstructor
+	r.constructors[transportType] = constructor
+}