Add resolved service and DNS server

service/resolved/resolve1.go

@@ -0,0 +1,648 @@
+//go:build linux
+
+package resolved
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/netip"
+	"os"
+	"os/user"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"syscall"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/process"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing/common"
+	E "github.com/sagernet/sing/common/exceptions"
+	F "github.com/sagernet/sing/common/format"
+	M "github.com/sagernet/sing/common/metadata"
+
+	"github.com/godbus/dbus/v5"
+	mDNS "github.com/miekg/dns"
+)
+
+type resolve1Manager Service
+
+type Address struct {
+	IfIndex int32
+	Family  int32
+	Address []byte
+}
+
+type Name struct {
+	IfIndex  int32
+	Hostname string
+}
+
+type ResourceRecord struct {
+	IfIndex int32
+	Type    uint16
+	Class   uint16
+	Data    []byte
+}
+
+type SRVRecord struct {
+	Priority  uint16
+	Weight    uint16
+	Port      uint16
+	Hostname  string
+	Addresses []Address
+	CNAME     string
+}
+
+type TXTRecord []byte
+
+type LinkDNS struct {
+	Family  int32
+	Address []byte
+}
+
+type LinkDNSEx struct {
+	Family  int32
+	Address []byte
+	Port    uint16
+	Name    string
+}
+
+type LinkDomain struct {
+	Domain      string
+	RoutingOnly bool
+}
+
+func (t *resolve1Manager) getLink(ifIndex int32) (*TransportLink, *dbus.Error) {
+	link, loaded := t.links[ifIndex]
+	if !loaded {
+		link = &TransportLink{}
+		t.links[ifIndex] = link
+		iif, err := t.network.InterfaceFinder().ByIndex(int(ifIndex))
+		if err != nil {
+			return nil, wrapError(err)
+		}
+		link.iif = iif
+	}
+	return link, nil
+}
+
+func (t *resolve1Manager) getSenderProcess(sender dbus.Sender) (int32, error) {
+	var senderPid int32
+	dbusObject := t.systemBus.Object("org.freedesktop.DBus", "/org/freedesktop/DBus")
+	if dbusObject == nil {
+		return 0, E.New("missing dbus object")
+	}
+	err := dbusObject.Call("org.freedesktop.DBus.GetConnectionUnixProcessID", 0, string(sender)).Store(&senderPid)
+	if err != nil {
+		return 0, E.Cause(err, "GetConnectionUnixProcessID")
+	}
+	return senderPid, nil
+}
+
+func (t *resolve1Manager) createMetadata(sender dbus.Sender) adapter.InboundContext {
+	var metadata adapter.InboundContext
+	metadata.Inbound = t.Tag()
+	metadata.InboundType = C.TypeResolved
+	senderPid, err := t.getSenderProcess(sender)
+	if err != nil {
+		return metadata
+	}
+	var processInfo process.Info
+	metadata.ProcessInfo = &processInfo
+	processInfo.ProcessID = uint32(senderPid)
+
+	processPath, err := os.Readlink(F.ToString("/proc/", senderPid, "/exe"))
+	if err == nil {
+		processInfo.ProcessPath = processPath
+	} else {
+		processPath, err = os.Readlink(F.ToString("/proc/", senderPid, "/comm"))
+		if err == nil {
+			processInfo.ProcessPath = processPath
+		}
+	}
+
+	var uidFound bool
+	statusContent, err := os.ReadFile(F.ToString("/proc/", senderPid, "/status"))
+	if err == nil {
+		for _, line := range strings.Split(string(statusContent), "\n") {
+			line = strings.TrimSpace(line)
+			if strings.HasPrefix(line, "Uid:") {
+				fields := strings.Fields(line)
+				if len(fields) >= 2 {
+					uid, parseErr := strconv.ParseUint(fields[1], 10, 32)
+					if parseErr != nil {
+						break
+					}
+					processInfo.UserId = int32(uid)
+					uidFound = true
+					if osUser, _ := user.LookupId(F.ToString(uid)); osUser != nil {
+						processInfo.User = osUser.Username
+					}
+					break
+				}
+			}
+		}
+	}
+	if !uidFound {
+		metadata.ProcessInfo.UserId = -1
+	}
+	return metadata
+}
+
+func (t *resolve1Manager) log(sender dbus.Sender, message ...any) {
+	metadata := t.createMetadata(sender)
+	if metadata.ProcessInfo != nil {
+		var prefix string
+		if metadata.ProcessInfo.ProcessPath != "" {
+			prefix = filepath.Base(metadata.ProcessInfo.ProcessPath)
+		} else if metadata.ProcessInfo.User != "" {
+			prefix = F.ToString("user:", metadata.ProcessInfo.User)
+		} else if metadata.ProcessInfo.UserId != 0 {
+			prefix = F.ToString("uid:", metadata.ProcessInfo.UserId)
+		}
+		t.logger.Info("(", prefix, ") ", F.ToString(message...))
+	} else {
+		t.logger.Info(F.ToString(message...))
+	}
+}
+
+func (t *resolve1Manager) logRequest(sender dbus.Sender, message ...any) context.Context {
+	ctx := log.ContextWithNewID(t.ctx)
+	metadata := t.createMetadata(sender)
+	if metadata.ProcessInfo != nil {
+		var prefix string
+		if metadata.ProcessInfo.ProcessPath != "" {
+			prefix = filepath.Base(metadata.ProcessInfo.ProcessPath)
+		} else if metadata.ProcessInfo.User != "" {
+			prefix = F.ToString("user:", metadata.ProcessInfo.User)
+		} else if metadata.ProcessInfo.UserId != 0 {
+			prefix = F.ToString("uid:", metadata.ProcessInfo.UserId)
+		}
+		t.logger.InfoContext(ctx, "(", prefix, ") ", F.ToString(message...))
+	} else {
+		t.logger.InfoContext(ctx, F.ToString(message...))
+	}
+	return adapter.WithContext(ctx, &metadata)
+}
+
+func familyToString(family int32) string {
+	switch family {
+	case syscall.AF_UNSPEC:
+		return "AF_UNSPEC"
+	case syscall.AF_INET:
+		return "AF_INET"
+	case syscall.AF_INET6:
+		return "AF_INET6"
+	default:
+		return F.ToString(family)
+	}
+}
+
+func (t *resolve1Manager) ResolveHostname(sender dbus.Sender, ifIndex int32, hostname string, family int32, flags uint64) (addresses []Address, canonical string, outflags uint64, err *dbus.Error) {
+	t.linkAccess.Lock()
+	link, err := t.getLink(ifIndex)
+	if err != nil {
+		return
+	}
+	t.linkAccess.Unlock()
+	var strategy C.DomainStrategy
+	switch family {
+	case syscall.AF_UNSPEC:
+		strategy = C.DomainStrategyAsIS
+	case syscall.AF_INET:
+		strategy = C.DomainStrategyIPv4Only
+	case syscall.AF_INET6:
+		strategy = C.DomainStrategyIPv6Only
+	}
+	ctx := t.logRequest(sender, "ResolveHostname ", link.iif.Name, " ", hostname, " ", familyToString(family), " ", flags)
+	responseAddresses, lookupErr := t.dnsRouter.Lookup(ctx, hostname, adapter.DNSQueryOptions{
+		LookupStrategy: strategy,
+	})
+	if lookupErr != nil {
+		err = wrapError(err)
+		return
+	}
+	addresses = common.Map(responseAddresses, func(it netip.Addr) Address {
+		var addrFamily int32
+		if it.Is4() {
+			addrFamily = syscall.AF_INET
+		} else {
+			addrFamily = syscall.AF_INET6
+		}
+		return Address{
+			IfIndex: ifIndex,
+			Family:  addrFamily,
+			Address: it.AsSlice(),
+		}
+	})
+	canonical = mDNS.CanonicalName(hostname)
+	return
+}
+
+func (t *resolve1Manager) ResolveAddress(sender dbus.Sender, ifIndex int32, family int32, address []byte, flags uint64) (names []Name, outflags uint64, err *dbus.Error) {
+	t.linkAccess.Lock()
+	link, err := t.getLink(ifIndex)
+	if err != nil {
+		return
+	}
+	t.linkAccess.Unlock()
+	addr, ok := netip.AddrFromSlice(address)
+	if !ok {
+		err = wrapError(E.New("invalid address"))
+		return
+	}
+	var nibbles []string
+	for i := len(address) - 1; i >= 0; i-- {
+		b := address[i]
+		nibbles = append(nibbles, fmt.Sprintf("%x", b&0x0F))
+		nibbles = append(nibbles, fmt.Sprintf("%x", b>>4))
+	}
+	var ptrDomain string
+	if addr.Is4() {
+		ptrDomain = strings.Join(nibbles, ".") + ".in-addr.arpa."
+	} else {
+		ptrDomain = strings.Join(nibbles, ".") + ".ip6.arpa."
+	}
+	request := &mDNS.Msg{
+		MsgHdr: mDNS.MsgHdr{
+			RecursionDesired: true,
+		},
+		Question: []mDNS.Question{
+			{
+				Name:   mDNS.Fqdn(ptrDomain),
+				Qtype:  mDNS.TypePTR,
+				Qclass: mDNS.ClassINET,
+			},
+		},
+	}
+	ctx := t.logRequest(sender, "ResolveAddress ", link.iif.Name, familyToString(family), addr, flags)
+	response, lookupErr := t.dnsRouter.Exchange(ctx, request, adapter.DNSQueryOptions{})
+	if lookupErr != nil {
+		err = wrapError(err)
+		return
+	}
+	if response.Rcode != mDNS.RcodeSuccess {
+		err = rcodeError(response.Rcode)
+		return
+	}
+	for _, rawRR := range response.Answer {
+		switch rr := rawRR.(type) {
+		case *mDNS.PTR:
+			names = append(names, Name{
+				IfIndex:  ifIndex,
+				Hostname: rr.Ptr,
+			})
+		}
+	}
+	return
+}
+
+func (t *resolve1Manager) ResolveRecord(sender dbus.Sender, ifIndex int32, family int32, hostname string, qClass uint16, qType uint16, flags uint64) (records []ResourceRecord, outflags uint64, err *dbus.Error) {
+	t.linkAccess.Lock()
+	link, err := t.getLink(ifIndex)
+	if err != nil {
+		return
+	}
+	t.linkAccess.Unlock()
+	request := &mDNS.Msg{
+		MsgHdr: mDNS.MsgHdr{
+			RecursionDesired: true,
+		},
+		Question: []mDNS.Question{
+			{
+				Name:   mDNS.Fqdn(hostname),
+				Qtype:  qType,
+				Qclass: qClass,
+			},
+		},
+	}
+	ctx := t.logRequest(sender, "ResolveRecord ", link.iif.Name, familyToString(family), hostname, mDNS.Class(qClass), mDNS.Type(qType), flags)
+	response, exchangeErr := t.dnsRouter.Exchange(ctx, request, adapter.DNSQueryOptions{})
+	if exchangeErr != nil {
+		err = wrapError(exchangeErr)
+		return
+	}
+	if response.Rcode != mDNS.RcodeSuccess {
+		err = rcodeError(response.Rcode)
+		return
+	}
+	for _, rr := range response.Answer {
+		var record ResourceRecord
+		record.IfIndex = ifIndex
+		record.Type = rr.Header().Rrtype
+		record.Class = rr.Header().Class
+		data := make([]byte, mDNS.Len(rr))
+		_, unpackErr := mDNS.PackRR(rr, data, 0, nil, false)
+		if unpackErr != nil {
+			err = wrapError(unpackErr)
+		}
+		record.Data = data
+	}
+	return
+}
+
+func (t *resolve1Manager) ResolveService(sender dbus.Sender, ifIndex int32, hostname string, sType string, domain string, family int32, flags uint64) (srvData []SRVRecord, txtData []TXTRecord, canonicalName string, canonicalType string, canonicalDomain string, outflags uint64, err *dbus.Error) {
+	t.linkAccess.Lock()
+	link, err := t.getLink(ifIndex)
+	if err != nil {
+		return
+	}
+	t.linkAccess.Unlock()
+
+	serviceName := hostname
+	if hostname != "" && !strings.HasSuffix(hostname, ".") {
+		serviceName += "."
+	}
+	serviceName += sType
+	if !strings.HasSuffix(serviceName, ".") {
+		serviceName += "."
+	}
+	serviceName += domain
+	if !strings.HasSuffix(serviceName, ".") {
+		serviceName += "."
+	}
+
+	ctx := t.logRequest(sender, "ResolveService ", link.iif.Name, " ", hostname, " ", sType, " ", domain, " ", familyToString(family), " ", flags)
+
+	srvRequest := &mDNS.Msg{
+		MsgHdr: mDNS.MsgHdr{
+			RecursionDesired: true,
+		},
+		Question: []mDNS.Question{
+			{
+				Name:   serviceName,
+				Qtype:  mDNS.TypeSRV,
+				Qclass: mDNS.ClassINET,
+			},
+		},
+	}
+
+	srvResponse, exchangeErr := t.dnsRouter.Exchange(ctx, srvRequest, adapter.DNSQueryOptions{})
+	if exchangeErr != nil {
+		err = wrapError(exchangeErr)
+		return
+	}
+	if srvResponse.Rcode != mDNS.RcodeSuccess {
+		err = rcodeError(srvResponse.Rcode)
+		return
+	}
+
+	txtRequest := &mDNS.Msg{
+		MsgHdr: mDNS.MsgHdr{
+			RecursionDesired: true,
+		},
+		Question: []mDNS.Question{
+			{
+				Name:   serviceName,
+				Qtype:  mDNS.TypeTXT,
+				Qclass: mDNS.ClassINET,
+			},
+		},
+	}
+
+	txtResponse, exchangeErr := t.dnsRouter.Exchange(ctx, txtRequest, adapter.DNSQueryOptions{})
+	if exchangeErr != nil {
+		err = wrapError(exchangeErr)
+		return
+	}
+
+	for _, rawRR := range srvResponse.Answer {
+		switch rr := rawRR.(type) {
+		case *mDNS.SRV:
+			var srvRecord SRVRecord
+			srvRecord.Priority = rr.Priority
+			srvRecord.Weight = rr.Weight
+			srvRecord.Port = rr.Port
+			srvRecord.Hostname = rr.Target
+
+			var strategy C.DomainStrategy
+			switch family {
+			case syscall.AF_UNSPEC:
+				strategy = C.DomainStrategyAsIS
+			case syscall.AF_INET:
+				strategy = C.DomainStrategyIPv4Only
+			case syscall.AF_INET6:
+				strategy = C.DomainStrategyIPv6Only
+			}
+
+			addrs, lookupErr := t.dnsRouter.Lookup(ctx, rr.Target, adapter.DNSQueryOptions{
+				LookupStrategy: strategy,
+			})
+			if lookupErr == nil {
+				srvRecord.Addresses = common.Map(addrs, func(it netip.Addr) Address {
+					var addrFamily int32
+					if it.Is4() {
+						addrFamily = syscall.AF_INET
+					} else {
+						addrFamily = syscall.AF_INET6
+					}
+					return Address{
+						IfIndex: ifIndex,
+						Family:  addrFamily,
+						Address: it.AsSlice(),
+					}
+				})
+			}
+			for _, a := range srvResponse.Answer {
+				if cname, ok := a.(*mDNS.CNAME); ok && cname.Header().Name == rr.Target {
+					srvRecord.CNAME = cname.Target
+					break
+				}
+			}
+			srvData = append(srvData, srvRecord)
+		}
+	}
+	for _, rawRR := range txtResponse.Answer {
+		switch rr := rawRR.(type) {
+		case *mDNS.TXT:
+			data := make([]byte, mDNS.Len(rr))
+			_, packErr := mDNS.PackRR(rr, data, 0, nil, false)
+			if packErr == nil {
+				txtData = append(txtData, data)
+			}
+		}
+	}
+	canonicalName = mDNS.CanonicalName(hostname)
+	canonicalType = mDNS.CanonicalName(sType)
+	canonicalDomain = mDNS.CanonicalName(domain)
+	return
+}
+
+func (t *resolve1Manager) SetLinkDNS(sender dbus.Sender, ifIndex int32, addresses []LinkDNS) *dbus.Error {
+	t.linkAccess.Lock()
+	defer t.linkAccess.Unlock()
+	link, err := t.getLink(ifIndex)
+	if err != nil {
+		return wrapError(err)
+	}
+	link.address = addresses
+	if len(addresses) > 0 {
+		t.log(sender, "SetLinkDNS ", link.iif.Name, " ", strings.Join(common.Map(addresses, func(it LinkDNS) string {
+			return M.AddrFromIP(it.Address).String()
+		}), ", "))
+	} else {
+		t.log(sender, "SetLinkDNS ", link.iif.Name, " (empty)")
+	}
+	return t.postUpdate(link)
+}
+
+func (t *resolve1Manager) SetLinkDNSEx(sender dbus.Sender, ifIndex int32, addresses []LinkDNSEx) *dbus.Error {
+	t.linkAccess.Lock()
+	defer t.linkAccess.Unlock()
+	link, err := t.getLink(ifIndex)
+	if err != nil {
+		return wrapError(err)
+	}
+	link.addressEx = addresses
+	if len(addresses) > 0 {
+		t.log(sender, "SetLinkDNSEx ", link.iif.Name, " ", strings.Join(common.Map(addresses, func(it LinkDNSEx) string {
+			return M.SocksaddrFrom(M.AddrFromIP(it.Address), it.Port).String()
+		}), ", "))
+	} else {
+		t.log(sender, "SetLinkDNSEx ", link.iif.Name, " (empty)")
+	}
+	return t.postUpdate(link)
+}
+
+func (t *resolve1Manager) SetLinkDomains(sender dbus.Sender, ifIndex int32, domains []LinkDomain) *dbus.Error {
+	t.linkAccess.Lock()
+	defer t.linkAccess.Unlock()
+	link, err := t.getLink(ifIndex)
+	if err != nil {
+		return wrapError(err)
+	}
+	link.domain = domains
+	if len(domains) > 0 {
+		t.log(sender, "SetLinkDomains ", link.iif.Name, " ", strings.Join(common.Map(domains, func(domain LinkDomain) string {
+			if !domain.RoutingOnly {
+				return domain.Domain
+			} else {
+				return "~" + domain.Domain
+			}
+		}), ", "))
+	} else {
+		t.log(sender, "SetLinkDomains ", link.iif.Name, " (empty)")
+	}
+	return t.postUpdate(link)
+}
+
+func (t *resolve1Manager) SetLinkDefaultRoute(sender dbus.Sender, ifIndex int32, defaultRoute bool) *dbus.Error {
+	t.linkAccess.Lock()
+	defer t.linkAccess.Unlock()
+	link, err := t.getLink(ifIndex)
+	if err != nil {
+		return err
+	}
+	link.defaultRoute = defaultRoute
+	if defaultRoute {
+		t.defaultRouteSequence = append(common.Filter(t.defaultRouteSequence, func(it int32) bool { return it != ifIndex }), ifIndex)
+	} else {
+		t.defaultRouteSequence = common.Filter(t.defaultRouteSequence, func(it int32) bool { return it != ifIndex })
+	}
+	var defaultRouteString string
+	if defaultRoute {
+		defaultRouteString = "yes"
+	} else {
+		defaultRouteString = "no"
+	}
+	t.log(sender, "SetLinkDefaultRoute ", link.iif.Name, " ", defaultRouteString)
+	return t.postUpdate(link)
+}
+
+func (t *resolve1Manager) SetLinkLLMNR(ifIndex int32, llmnrMode string) *dbus.Error {
+	return nil
+}
+
+func (t *resolve1Manager) SetLinkMulticastDNS(ifIndex int32, mdnsMode string) *dbus.Error {
+	return nil
+}
+
+func (t *resolve1Manager) SetLinkDNSOverTLS(sender dbus.Sender, ifIndex int32, dotMode string) *dbus.Error {
+	t.linkAccess.Lock()
+	defer t.linkAccess.Unlock()
+	link, err := t.getLink(ifIndex)
+	if err != nil {
+		return wrapError(err)
+	}
+	switch dotMode {
+	case "yes":
+		link.dnsOverTLS = true
+	case "":
+		dotMode = "no"
+		fallthrough
+	case "opportunistic", "no":
+		link.dnsOverTLS = false
+	}
+	t.log(sender, "SetLinkDNSOverTLS ", link.iif.Name, " ", dotMode)
+	return t.postUpdate(link)
+}
+
+func (t *resolve1Manager) SetLinkDNSSEC(ifIndex int32, dnssecMode string) *dbus.Error {
+	return nil
+}
+
+func (t *resolve1Manager) SetLinkDNSSECNegativeTrustAnchors(ifIndex int32, domains []string) *dbus.Error {
+	return nil
+}
+
+func (t *resolve1Manager) RevertLink(sender dbus.Sender, ifIndex int32) *dbus.Error {
+	t.linkAccess.Lock()
+	defer t.linkAccess.Unlock()
+	link, err := t.getLink(ifIndex)
+	if err != nil {
+		return wrapError(err)
+	}
+	delete(t.links, ifIndex)
+	t.log(sender, "RevertLink ", link.iif.Name)
+	return t.postUpdate(link)
+}
+
+// TODO: implement RegisterService, UnregisterService
+
+func (t *resolve1Manager) RegisterService(sender dbus.Sender, identifier string, nameTemplate string, serviceType string, port uint16, priority uint16, weight uint16, txtRecords []TXTRecord) (objectPath dbus.ObjectPath, dbusErr *dbus.Error) {
+	return "", wrapError(E.New("not implemented"))
+}
+
+func (t *resolve1Manager) UnregisterService(sender dbus.Sender, servicePath dbus.ObjectPath) error {
+	return wrapError(E.New("not implemented"))
+}
+
+func (t *resolve1Manager) ResetStatistics() *dbus.Error {
+	return nil
+}
+
+func (t *resolve1Manager) FlushCaches(sender dbus.Sender) *dbus.Error {
+	t.dnsRouter.ClearCache()
+	t.log(sender, "FlushCaches")
+	return nil
+}
+
+func (t *resolve1Manager) ResetServerFeatures() *dbus.Error {
+	return nil
+}
+
+func (t *resolve1Manager) postUpdate(link *TransportLink) *dbus.Error {
+	if t.updateCallback != nil {
+		return wrapError(t.updateCallback(link))
+	}
+	return nil
+}
+
+func rcodeError(rcode int) *dbus.Error {
+	return dbus.NewError("org.freedesktop.resolve1.DnsError."+mDNS.RcodeToString[rcode], []any{mDNS.RcodeToString[rcode]})
+}
+
+func wrapError(err error) *dbus.Error {
+	if err == nil {
+		return nil
+	}
+	var rcode dns.RcodeError
+	if errors.As(err, &rcode) {
+		return rcodeError(int(rcode))
+	}
+	return dbus.MakeFailedError(err)
+}

service/resolved/service.go

@@ -0,0 +1,252 @@
+//go:build linux
+
+package resolved
+
+import (
+	"context"
+	"net"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	boxService "github.com/sagernet/sing-box/adapter/service"
+	"github.com/sagernet/sing-box/common/listener"
+	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"
+	dnsOutbound "github.com/sagernet/sing-box/protocol/dns"
+	tun "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"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+	"github.com/sagernet/sing/common/x/list"
+	"github.com/sagernet/sing/service"
+
+	"github.com/godbus/dbus/v5"
+	mDNS "github.com/miekg/dns"
+)
+
+func RegisterService(registry *boxService.Registry) {
+	boxService.Register[option.ResolvedServiceOptions](registry, C.TypeResolved, NewService)
+}
+
+type Service struct {
+	boxService.Adapter
+	ctx                   context.Context
+	logger                log.ContextLogger
+	network               adapter.NetworkManager
+	dnsRouter             adapter.DNSRouter
+	listener              *listener.Listener
+	systemBus             *dbus.Conn
+	linkAccess            sync.RWMutex
+	links                 map[int32]*TransportLink
+	defaultRouteSequence  []int32
+	networkUpdateCallback *list.Element[tun.NetworkUpdateCallback]
+	updateCallback        func(*TransportLink) error
+	deleteCallback        func(*TransportLink)
+}
+
+type TransportLink struct {
+	iif          *control.Interface
+	address      []LinkDNS
+	addressEx    []LinkDNSEx
+	domain       []LinkDomain
+	defaultRoute bool
+	dnsOverTLS   bool
+	// dnsOverTLSFallback bool
+}
+
+func NewService(ctx context.Context, logger log.ContextLogger, tag string, options option.ResolvedServiceOptions) (adapter.Service, error) {
+	inbound := &Service{
+		Adapter:   boxService.NewAdapter(C.TypeResolved, tag),
+		ctx:       ctx,
+		logger:    logger,
+		network:   service.FromContext[adapter.NetworkManager](ctx),
+		dnsRouter: service.FromContext[adapter.DNSRouter](ctx),
+		links:     make(map[int32]*TransportLink),
+	}
+	inbound.listener = listener.New(listener.Options{
+		Context:                  ctx,
+		Logger:                   logger,
+		Network:                  []string{N.NetworkTCP, N.NetworkUDP},
+		Listen:                   options.ListenOptions,
+		ConnectionHandler:        inbound,
+		OOBPacketHandler:         inbound,
+		ThreadUnsafePacketWriter: true,
+	})
+	return inbound, nil
+}
+
+func (i *Service) Start(stage adapter.StartStage) error {
+	switch stage {
+	case adapter.StartStateInitialize:
+		inboundManager := service.FromContext[adapter.ServiceManager](i.ctx)
+		for _, transport := range inboundManager.Services() {
+			if transport.Type() == C.TypeResolved && transport != i {
+				return E.New("multiple resolved service are not supported")
+			}
+		}
+	case adapter.StartStateStart:
+		err := i.listener.Start()
+		if err != nil {
+			return err
+		}
+		systemBus, err := dbus.SystemBus()
+		if err != nil {
+			return err
+		}
+		i.systemBus = systemBus
+		err = systemBus.Export((*resolve1Manager)(i), "/org/freedesktop/resolve1", "org.freedesktop.resolve1.Manager")
+		if err != nil {
+			return err
+		}
+		reply, err := systemBus.RequestName("org.freedesktop.resolve1", dbus.NameFlagDoNotQueue)
+		if err != nil {
+			return err
+		}
+		switch reply {
+		case dbus.RequestNameReplyPrimaryOwner:
+		case dbus.RequestNameReplyExists:
+			return E.New("D-Bus object already exists, maybe real resolved is running")
+		default:
+			return E.New("unknown request name reply: ", reply)
+		}
+		i.networkUpdateCallback = i.network.NetworkMonitor().RegisterCallback(i.onNetworkUpdate)
+	}
+	return nil
+}
+
+func (i *Service) Close() error {
+	if i.networkUpdateCallback != nil {
+		i.network.NetworkMonitor().UnregisterCallback(i.networkUpdateCallback)
+	}
+	if i.systemBus != nil {
+		i.systemBus.ReleaseName("org.freedesktop.resolve1")
+		i.systemBus.Close()
+	}
+	return i.listener.Close()
+}
+
+func (i *Service) NewConnectionEx(ctx context.Context, conn net.Conn, metadata adapter.InboundContext, onClose N.CloseHandlerFunc) {
+	metadata.Inbound = i.Tag()
+	metadata.InboundType = i.Type()
+	metadata.Destination = M.Socksaddr{}
+	for {
+		conn.SetReadDeadline(time.Now().Add(C.DNSTimeout))
+		err := dnsOutbound.HandleStreamDNSRequest(ctx, i.dnsRouter, conn, metadata)
+		if err != nil {
+			N.CloseOnHandshakeFailure(conn, onClose, err)
+			return
+		}
+	}
+}
+
+func (i *Service) NewPacketEx(buffer *buf.Buffer, oob []byte, source M.Socksaddr) {
+	go i.exchangePacket(buffer, oob, source)
+}
+
+func (i *Service) exchangePacket(buffer *buf.Buffer, oob []byte, source M.Socksaddr) {
+	ctx := log.ContextWithNewID(i.ctx)
+	err := i.exchangePacket0(ctx, buffer, oob, source)
+	if err != nil {
+		i.logger.ErrorContext(ctx, "process DNS packet: ", err)
+	}
+}
+
+func (i *Service) exchangePacket0(ctx context.Context, buffer *buf.Buffer, oob []byte, source M.Socksaddr) error {
+	var message mDNS.Msg
+	err := message.Unpack(buffer.Bytes())
+	buffer.Release()
+	if err != nil {
+		return E.Cause(err, "unpack request")
+	}
+	var metadata adapter.InboundContext
+	metadata.Source = source
+	response, err := i.dnsRouter.Exchange(adapter.WithContext(ctx, &metadata), &message, adapter.DNSQueryOptions{})
+	if err != nil {
+		return err
+	}
+	responseBuffer, err := dns.TruncateDNSMessage(&message, response, 0)
+	if err != nil {
+		return err
+	}
+	defer responseBuffer.Release()
+	_, _, err = i.listener.UDPConn().WriteMsgUDPAddrPort(responseBuffer.Bytes(), oob, source.AddrPort())
+	return err
+}
+
+func (i *Service) onNetworkUpdate() {
+	i.linkAccess.Lock()
+	defer i.linkAccess.Unlock()
+	var deleteIfIndex []int
+	for ifIndex, link := range i.links {
+		iif, err := i.network.InterfaceFinder().ByIndex(int(ifIndex))
+		if err != nil || iif != link.iif {
+			deleteIfIndex = append(deleteIfIndex, int(ifIndex))
+		}
+		i.defaultRouteSequence = common.Filter(i.defaultRouteSequence, func(it int32) bool {
+			return it != ifIndex
+		})
+		if i.deleteCallback != nil {
+			i.deleteCallback(link)
+		}
+	}
+	for _, ifIndex := range deleteIfIndex {
+		delete(i.links, int32(ifIndex))
+	}
+}
+
+func (conf *TransportLink) nameList(ndots int, name string) []string {
+	search := common.Map(common.Filter(conf.domain, func(it LinkDomain) bool {
+		return !it.RoutingOnly
+	}), func(it LinkDomain) string {
+		return it.Domain
+	})
+
+	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, ".") >= ndots
+	name += "."
+	// l++
+
+	names := make([]string, 0, 1+len(search))
+	if hasNdots && !avoidDNS(name) {
+		names = append(names, name)
+	}
+	for _, suffix := range 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")
+}

service/resolved/stub.go

@@ -0,0 +1,27 @@
+//go:build !linux
+
+package resolved
+
+import (
+	"context"
+
+	"github.com/sagernet/sing-box/adapter"
+	boxService "github.com/sagernet/sing-box/adapter/service"
+	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"
+)
+
+func RegisterService(registry *boxService.Registry) {
+	boxService.Register[option.ResolvedServiceOptions](registry, C.TypeResolved, func(ctx context.Context, logger log.ContextLogger, tag string, options option.ResolvedServiceOptions) (adapter.Service, error) {
+		return nil, E.New("resolved service is only supported on Linux")
+	})
+}
+
+func RegisterTransport(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.ResolvedDNSServerOptions](registry, C.TypeResolved, func(ctx context.Context, logger log.ContextLogger, tag string, options option.ResolvedDNSServerOptions) (adapter.DNSTransport, error) {
+		return nil, E.New("resolved DNS server is only supported on Linux")
+	})
+}

service/resolved/transport.go

@@ -0,0 +1,297 @@
+//go:build linux
+
+package resolved
+
+import (
+	"context"
+	"net/netip"
+	"os"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/dialer"
+	"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"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	"github.com/sagernet/sing/service"
+
+	mDNS "github.com/miekg/dns"
+)
+
+func RegisterTransport(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.ResolvedDNSServerOptions](registry, C.TypeResolved, NewTransport)
+}
+
+var _ adapter.DNSTransport = (*Transport)(nil)
+
+type Transport struct {
+	dns.TransportAdapter
+	ctx                    context.Context
+	logger                 logger.ContextLogger
+	serviceTag             string
+	acceptDefaultResolvers bool
+	ndots                  int
+	timeout                time.Duration
+	attempts               int
+	rotate                 bool
+	service                *Service
+	linkAccess             sync.RWMutex
+	linkServers            map[*TransportLink]*LinkServers
+}
+
+type LinkServers struct {
+	Link         *TransportLink
+	Servers      []adapter.DNSTransport
+	serverOffset uint32
+}
+
+func (c *LinkServers) ServerOffset(rotate bool) uint32 {
+	if rotate {
+		return atomic.AddUint32(&c.serverOffset, 1) - 1
+	}
+	return 0
+}
+
+func NewTransport(ctx context.Context, logger log.ContextLogger, tag string, options option.ResolvedDNSServerOptions) (adapter.DNSTransport, error) {
+	return &Transport{
+		TransportAdapter:       dns.NewTransportAdapter(C.DNSTypeDHCP, tag, nil),
+		ctx:                    ctx,
+		logger:                 logger,
+		serviceTag:             options.Service,
+		acceptDefaultResolvers: options.AcceptDefaultResolvers,
+		// ndots:                  options.NDots,
+		// timeout:                time.Duration(options.Timeout),
+		// attempts:               options.Attempts,
+		// rotate:                 options.Rotate,
+		ndots:       1,
+		timeout:     5 * time.Second,
+		attempts:    2,
+		linkServers: make(map[*TransportLink]*LinkServers),
+	}, nil
+}
+
+func (t *Transport) Start(stage adapter.StartStage) error {
+	if stage != adapter.StartStateInitialize {
+		return nil
+	}
+	serviceManager := service.FromContext[adapter.ServiceManager](t.ctx)
+	service, loaded := serviceManager.Get(t.serviceTag)
+	if !loaded {
+		return E.New("service not found: ", t.serviceTag)
+	}
+	resolvedInbound, isResolved := service.(*Service)
+	if !isResolved {
+		return E.New("service is not resolved: ", t.serviceTag)
+	}
+	resolvedInbound.updateCallback = t.updateTransports
+	resolvedInbound.deleteCallback = t.deleteTransport
+	t.service = resolvedInbound
+	return nil
+}
+
+func (t *Transport) Close() error {
+	t.linkAccess.RLock()
+	defer t.linkAccess.RUnlock()
+	for _, servers := range t.linkServers {
+		for _, server := range servers.Servers {
+			server.Close()
+		}
+	}
+	return nil
+}
+
+func (t *Transport) updateTransports(link *TransportLink) error {
+	t.linkAccess.Lock()
+	defer t.linkAccess.Unlock()
+	if servers, loaded := t.linkServers[link]; loaded {
+		for _, server := range servers.Servers {
+			server.Close()
+		}
+	}
+	serverDialer := common.Must1(dialer.NewDefault(t.ctx, option.DialerOptions{
+		BindInterface:      link.iif.Name,
+		UDPFragmentDefault: true,
+	}))
+	var transports []adapter.DNSTransport
+	for _, address := range link.address {
+		serverAddr, ok := netip.AddrFromSlice(address.Address)
+		if !ok {
+			return os.ErrInvalid
+		}
+		if link.dnsOverTLS {
+			tlsConfig := common.Must1(tls.NewClient(t.ctx, serverAddr.String(), option.OutboundTLSOptions{
+				Enabled:    true,
+				ServerName: serverAddr.String(),
+			}))
+			transports = append(transports, transport.NewTLSRaw(t.logger, t.TransportAdapter, serverDialer, M.SocksaddrFrom(serverAddr, 53), tlsConfig))
+
+		} else {
+			transports = append(transports, transport.NewUDPRaw(t.logger, t.TransportAdapter, serverDialer, M.SocksaddrFrom(serverAddr, 53)))
+		}
+	}
+	for _, address := range link.addressEx {
+		serverAddr, ok := netip.AddrFromSlice(address.Address)
+		if !ok {
+			return os.ErrInvalid
+		}
+		if link.dnsOverTLS {
+			var serverName string
+			if address.Name != "" {
+				serverName = address.Name
+			} else {
+				serverName = serverAddr.String()
+			}
+			tlsConfig := common.Must1(tls.NewClient(t.ctx, serverAddr.String(), option.OutboundTLSOptions{
+				Enabled:    true,
+				ServerName: serverName,
+			}))
+			transports = append(transports, transport.NewTLSRaw(t.logger, t.TransportAdapter, serverDialer, M.SocksaddrFrom(serverAddr, address.Port), tlsConfig))
+
+		} else {
+			transports = append(transports, transport.NewUDPRaw(t.logger, t.TransportAdapter, serverDialer, M.SocksaddrFrom(serverAddr, address.Port)))
+		}
+	}
+	t.linkServers[link] = &LinkServers{
+		Link:    link,
+		Servers: transports,
+	}
+	return nil
+}
+
+func (t *Transport) deleteTransport(link *TransportLink) {
+	t.linkAccess.Lock()
+	defer t.linkAccess.Unlock()
+	servers, loaded := t.linkServers[link]
+	if !loaded {
+		return
+	}
+	for _, server := range servers.Servers {
+		server.Close()
+	}
+	delete(t.linkServers, link)
+}
+
+func (t *Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	question := message.Question[0]
+	var selectedLink *TransportLink
+	t.service.linkAccess.RLock()
+	for _, link := range t.service.links {
+		for _, domain := range link.domain {
+			if domain.Domain == "." && domain.RoutingOnly && !t.acceptDefaultResolvers {
+				continue
+			}
+			if strings.HasSuffix(question.Name, domain.Domain) {
+				selectedLink = link
+			}
+		}
+	}
+	if selectedLink == nil && t.acceptDefaultResolvers {
+		for l := len(t.service.defaultRouteSequence); l > 0; l-- {
+			selectedLink = t.service.links[t.service.defaultRouteSequence[l-1]]
+			if len(selectedLink.address) > 0 || len(selectedLink.addressEx) > 0 {
+				break
+			}
+		}
+	}
+	t.service.linkAccess.RUnlock()
+	if selectedLink == nil {
+		return dns.FixedResponseStatus(message, mDNS.RcodeNameError), nil
+	}
+	t.linkAccess.RLock()
+	servers := t.linkServers[selectedLink]
+	t.linkAccess.RUnlock()
+	if len(servers.Servers) == 0 {
+		return dns.FixedResponseStatus(message, mDNS.RcodeNameError), nil
+	}
+	if question.Qtype == mDNS.TypeA || question.Qtype == mDNS.TypeAAAA {
+		return t.exchangeParallel(ctx, servers, message)
+	} else {
+		return t.exchangeSingleRequest(ctx, servers, message)
+	}
+}
+
+func (t *Transport) exchangeSingleRequest(ctx context.Context, servers *LinkServers, message *mDNS.Msg) (*mDNS.Msg, error) {
+	var lastErr error
+	for _, fqdn := range servers.Link.nameList(t.ndots, message.Question[0].Name) {
+		response, err := t.tryOneName(ctx, servers, message, fqdn)
+		if err != nil {
+			lastErr = err
+			continue
+		}
+		return response, nil
+	}
+	return nil, lastErr
+}
+
+func (t *Transport) tryOneName(ctx context.Context, servers *LinkServers, message *mDNS.Msg, fqdn string) (*mDNS.Msg, error) {
+	serverOffset := servers.ServerOffset(t.rotate)
+	sLen := uint32(len(servers.Servers))
+	var lastErr error
+	for i := 0; i < t.attempts; i++ {
+		for j := uint32(0); j < sLen; j++ {
+			server := servers.Servers[(serverOffset+j)%sLen]
+			question := message.Question[0]
+			question.Name = fqdn
+			exchangeMessage := *message
+			exchangeMessage.Question = []mDNS.Question{question}
+			exchangeCtx, cancel := context.WithTimeout(ctx, t.timeout)
+			response, err := server.Exchange(exchangeCtx, &exchangeMessage)
+			cancel()
+			if err != nil {
+				lastErr = err
+				continue
+			}
+			return response, nil
+		}
+	}
+	return nil, E.Cause(lastErr, fqdn)
+}
+
+func (t *Transport) exchangeParallel(ctx context.Context, servers *LinkServers, message *mDNS.Msg) (*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, servers, message, fqdn)
+		select {
+		case results <- queryResult{response, err}:
+		case <-returned:
+		}
+	}
+	queryCtx, queryCancel := context.WithCancel(ctx)
+	defer queryCancel()
+	var nameCount int
+	for _, fqdn := range servers.Link.nameList(t.ndots, message.Question[0].Name) {
+		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...)
+			}
+		}
+	}
+}