DNS: Fix some bugs; Refactors; Optimizations (#4659)

app/dns/dns.go

@@ -3,12 +3,12 @@ package dns
 
 import (
 	"context"
+	go_errors "errors"
 	"fmt"
 	"sort"
 	"strings"
 	"sync"
 
-	"github.com/xtls/xray-core/app/router"
 	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/errors"
 	"github.com/xtls/xray-core/common/net"
@@ -20,8 +20,6 @@ import (
 // DNS is a DNS rely server.
 type DNS struct {
 	sync.Mutex
-	tag                    string
-	disableCache           bool
 	disableFallback        bool
 	disableFallbackIfMatch bool
 	ipOption               *dns.IPOption
@@ -40,13 +38,6 @@ type DomainMatcherInfo struct {
 
 // New creates a new DNS server with given configuration.
 func New(ctx context.Context, config *Config) (*DNS, error) {
-	var tag string
-	if len(config.Tag) > 0 {
-		tag = config.Tag
-	} else {
-		tag = generateRandomTag()
-	}
-
 	var clientIP net.IP
 	switch len(config.ClientIp) {
 	case 0, net.IPv4len, net.IPv6len:
@@ -55,26 +46,28 @@ func New(ctx context.Context, config *Config) (*DNS, error) {
 		return nil, errors.New("unexpected client IP length ", len(config.ClientIp))
 	}
 
-	var ipOption *dns.IPOption
+	var ipOption dns.IPOption
 	switch config.QueryStrategy {
 	case QueryStrategy_USE_IP:
-		ipOption = &dns.IPOption{
+		ipOption = dns.IPOption{
 			IPv4Enable: true,
 			IPv6Enable: true,
 			FakeEnable: false,
 		}
 	case QueryStrategy_USE_IP4:
-		ipOption = &dns.IPOption{
+		ipOption = dns.IPOption{
 			IPv4Enable: true,
 			IPv6Enable: false,
 			FakeEnable: false,
 		}
 	case QueryStrategy_USE_IP6:
-		ipOption = &dns.IPOption{
+		ipOption = dns.IPOption{
 			IPv4Enable: false,
 			IPv6Enable: true,
 			FakeEnable: false,
 		}
+	default:
+		return nil, errors.New("unexpected query strategy ", config.QueryStrategy)
 	}
 
 	hosts, err := NewStaticHosts(config.StaticHosts)
@@ -82,8 +75,14 @@ func New(ctx context.Context, config *Config) (*DNS, error) {
 		return nil, errors.New("failed to create hosts").Base(err)
 	}
 
-	clients := []*Client{}
+	var clients []*Client
 	domainRuleCount := 0
+
+	var defaultTag = config.Tag
+	if len(config.Tag) == 0 {
+		defaultTag = generateRandomTag()
+	}
+
 	for _, ns := range config.NameServer {
 		domainRuleCount += len(ns.PrioritizedDomain)
 	}
@@ -91,7 +90,6 @@ func New(ctx context.Context, config *Config) (*DNS, error) {
 	// MatcherInfos is ensured to cover the maximum index domainMatcher could return, where matcher's index starts from 1
 	matcherInfos := make([]*DomainMatcherInfo, domainRuleCount+1)
 	domainMatcher := &strmatcher.MatcherGroup{}
-	geoipContainer := router.GeoIPMatcherContainer{}
 
 	for _, ns := range config.NameServer {
 		clientIdx := len(clients)
@@ -109,7 +107,18 @@ func New(ctx context.Context, config *Config) (*DNS, error) {
 		case net.IPv4len, net.IPv6len:
 			myClientIP = net.IP(ns.ClientIp)
 		}
-		client, err := NewClient(ctx, ns, myClientIP, geoipContainer, &matcherInfos, updateDomain)
+
+		disableCache := config.DisableCache
+
+		var tag = defaultTag
+		if len(ns.Tag) > 0 {
+			tag = ns.Tag
+		}
+		clientIPOption := ResolveIpOptionOverride(ns.QueryStrategy, ipOption)
+		if !clientIPOption.IPv4Enable && !clientIPOption.IPv6Enable {
+			return nil, errors.New("no QueryStrategy available for ", ns.Address)
+		}
+		client, err := NewClient(ctx, ns, myClientIP, disableCache, tag, clientIPOption, &matcherInfos, updateDomain)
 		if err != nil {
 			return nil, errors.New("failed to create client").Base(err)
 		}
@@ -118,18 +127,16 @@ func New(ctx context.Context, config *Config) (*DNS, error) {
 
 	// If there is no DNS client in config, add a `localhost` DNS client
 	if len(clients) == 0 {
-		clients = append(clients, NewLocalDNSClient())
+		clients = append(clients, NewLocalDNSClient(ipOption))
 	}
 
 	return &DNS{
-		tag:                    tag,
 		hosts:                  hosts,
-		ipOption:               ipOption,
+		ipOption:               &ipOption,
 		clients:                clients,
 		ctx:                    ctx,
 		domainMatcher:          domainMatcher,
 		matcherInfos:           matcherInfos,
-		disableCache:           config.DisableCache,
 		disableFallback:        config.DisableFallback,
 		disableFallbackIfMatch: config.DisableFallbackIfMatch,
 	}, nil
@@ -153,11 +160,21 @@ func (s *DNS) Close() error {
 // IsOwnLink implements proxy.dns.ownLinkVerifier
 func (s *DNS) IsOwnLink(ctx context.Context) bool {
 	inbound := session.InboundFromContext(ctx)
-	return inbound != nil && inbound.Tag == s.tag
+	if inbound == nil {
+		return false
+	}
+	for _, client := range s.clients {
+		if client.tag == inbound.Tag {
+			return true
+		}
+	}
+	return false
 }
 
 // LookupIP implements dns.Client.
 func (s *DNS) LookupIP(domain string, option dns.IPOption) ([]net.IP, uint32, error) {
+	// Normalize the FQDN form query
+	domain = strings.TrimSuffix(domain, ".")
 	if domain == "" {
 		return nil, 0, errors.New("empty domain name")
 	}
@@ -169,9 +186,6 @@ func (s *DNS) LookupIP(domain string, option dns.IPOption) ([]net.IP, uint32, er
 		return nil, 0, dns.ErrEmptyResponse
 	}
 
-	// Normalize the FQDN form query
-	domain = strings.TrimSuffix(domain, ".")
-
 	// Static host lookup
 	switch addrs := s.hosts.Lookup(domain, option); {
 	case addrs == nil: // Domain not recorded in static host
@@ -184,32 +198,49 @@ func (s *DNS) LookupIP(domain string, option dns.IPOption) ([]net.IP, uint32, er
 	default: // Successfully found ip records in static host
 		errors.LogInfo(s.ctx, "returning ", len(addrs), " IP(s) for domain ", domain, " -> ", addrs)
 		ips, err := toNetIP(addrs)
-		return ips, 10, err // Hosts ttl is 10
+		if err != nil {
+			return nil, 0, err
+		}
+		return ips, 10, nil // Hosts ttl is 10
 	}
 
 	// Name servers lookup
-	errs := []error{}
-	ctx := session.ContextWithInbound(s.ctx, &session.Inbound{Tag: s.tag})
+	var errs []error
 	for _, client := range s.sortClients(domain) {
 		if !option.FakeEnable && strings.EqualFold(client.Name(), "FakeDNS") {
 			errors.LogDebug(s.ctx, "skip DNS resolution for domain ", domain, " at server ", client.Name())
 			continue
 		}
-		ips, ttl, err := client.QueryIP(ctx, domain, option, s.disableCache)
+
+		ips, ttl, err := client.QueryIP(s.ctx, domain, option)
+
 		if len(ips) > 0 {
+			if ttl == 0 {
+				ttl = 1
+			}
 			return ips, ttl, nil
 		}
-		if err != nil {
-			errors.LogInfoInner(s.ctx, err, "failed to lookup ip for domain ", domain, " at server ", client.Name())
-			errs = append(errs, err)
-		}
-		// 5 for RcodeRefused in miekg/dns, hardcode to reduce binary size
-		if err != context.Canceled && err != context.DeadlineExceeded && err != errExpectedIPNonMatch && err != dns.ErrEmptyResponse && dns.RCodeFromError(err) != 5 {
-			return nil, 0, err
+
+		errors.LogInfoInner(s.ctx, err, "failed to lookup ip for domain ", domain, " at server ", client.Name())
+		if err == nil {
+			err = dns.ErrEmptyResponse
 		}
+		errs = append(errs, err)
+
 	}
 
-	return nil, 0, errors.New("returning nil for domain ", domain).Base(errors.Combine(errs...))
+	if len(errs) > 0 {
+		allErrs := errors.Combine(errs...)
+		err0 := errs[0]
+		if errors.AllEqual(err0, allErrs) {
+			if go_errors.Is(err0, dns.ErrEmptyResponse) {
+				return nil, 0, dns.ErrEmptyResponse
+			}
+			return nil, 0, errors.New("returning nil for domain ", domain).Base(err0)
+		}
+		return nil, 0, errors.New("returning nil for domain ", domain).Base(allErrs)
+	}
+	return nil, 0, dns.ErrEmptyResponse
 }
 
 // LookupHosts implements dns.HostsLookup.
@@ -228,22 +259,6 @@ func (s *DNS) LookupHosts(domain string) *net.Address {
 	return nil
 }
 
-// GetIPOption implements ClientWithIPOption.
-func (s *DNS) GetIPOption() *dns.IPOption {
-	return s.ipOption
-}
-
-// SetQueryOption implements ClientWithIPOption.
-func (s *DNS) SetQueryOption(isIPv4Enable, isIPv6Enable bool) {
-	s.ipOption.IPv4Enable = isIPv4Enable
-	s.ipOption.IPv6Enable = isIPv6Enable
-}
-
-// SetFakeDNSOption implements ClientWithIPOption.
-func (s *DNS) SetFakeDNSOption(isFakeEnable bool) {
-	s.ipOption.FakeEnable = isFakeEnable
-}
-
 func (s *DNS) sortClients(domain string) []*Client {
 	clients := make([]*Client, 0, len(s.clients))
 	clientUsed := make([]bool, len(s.clients))