refactor: new dns app

app/dns/dns.go

@@ -2,3 +2,233 @@
 package dns
 
 //go:generate go run github.com/xtls/xray-core/common/errors/errorgen
+
+import (
+	"context"
+	"fmt"
+	"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"
+	"github.com/xtls/xray-core/common/session"
+	"github.com/xtls/xray-core/common/strmatcher"
+	"github.com/xtls/xray-core/features"
+	"github.com/xtls/xray-core/features/dns"
+)
+
+// DNS is a DNS rely server.
+type DNS struct {
+	sync.Mutex
+	tag           string
+	disableCache  bool
+	hosts         *StaticHosts
+	clients       []*Client
+	ctx           context.Context
+	domainMatcher strmatcher.IndexMatcher
+	matcherInfos  []DomainMatcherInfo
+}
+
+// DomainMatcherInfo contains information attached to index returned by Server.domainMatcher
+type DomainMatcherInfo struct {
+	clientIdx     uint16
+	domainRuleIdx uint16
+}
+
+// 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:
+		clientIP = net.IP(config.ClientIp)
+	default:
+		return nil, newError("unexpected client IP length ", len(config.ClientIp))
+	}
+
+	hosts, err := NewStaticHosts(config.StaticHosts, config.Hosts)
+	if err != nil {
+		return nil, newError("failed to create hosts").Base(err)
+	}
+
+	clients := []*Client{}
+	domainRuleCount := 0
+	for _, ns := range config.NameServer {
+		domainRuleCount += len(ns.PrioritizedDomain)
+	}
+
+	// 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 _, endpoint := range config.NameServers {
+		features.PrintDeprecatedFeatureWarning("simple DNS server")
+		client, err := NewSimpleClient(ctx, endpoint, clientIP)
+		if err != nil {
+			return nil, newError("failed to create client").Base(err)
+		}
+		clients = append(clients, client)
+	}
+
+	for _, ns := range config.NameServer {
+		clientIdx := len(clients)
+		updateDomain := func(domainRule strmatcher.Matcher, originalRuleIdx int, matcherInfos []DomainMatcherInfo) error {
+			midx := domainMatcher.Add(domainRule)
+			matcherInfos[midx] = DomainMatcherInfo{
+				clientIdx:     uint16(clientIdx),
+				domainRuleIdx: uint16(originalRuleIdx),
+			}
+			return nil
+		}
+
+		myClientIP := clientIP
+		switch len(ns.ClientIp) {
+		case net.IPv4len, net.IPv6len:
+			myClientIP = net.IP(ns.ClientIp)
+		}
+		client, err := NewClient(ctx, ns, myClientIP, geoipContainer, &matcherInfos, updateDomain)
+		if err != nil {
+			return nil, newError("failed to create client").Base(err)
+		}
+		clients = append(clients, client)
+	}
+
+	// If there is no DNS client in config, add a `localhost` DNS client
+	if len(clients) == 0 {
+		clients = append(clients, NewLocalDNSClient())
+	}
+
+	return &DNS{
+		tag:           tag,
+		hosts:         hosts,
+		clients:       clients,
+		ctx:           ctx,
+		domainMatcher: domainMatcher,
+		matcherInfos:  matcherInfos,
+		disableCache:  config.DisableCache,
+	}, nil
+}
+
+// Type implements common.HasType.
+func (*DNS) Type() interface{} {
+	return dns.ClientType()
+}
+
+// Start implements common.Runnable.
+func (s *DNS) Start() error {
+	return nil
+}
+
+// Close implements common.Closable.
+func (s *DNS) Close() error {
+	return nil
+}
+
+// IsOwnLink implements proxy.dns.ownLinkVerifier
+func (s *DNS) IsOwnLink(ctx context.Context) bool {
+	inbound := session.InboundFromContext(ctx)
+	return inbound != nil && inbound.Tag == s.tag
+}
+
+// LookupIP implements dns.Client.
+func (s *DNS) LookupIP(domain string, option dns.IPOption) ([]net.IP, error) {
+	if domain == "" {
+		return nil, newError("empty domain name")
+	}
+
+	// Normalize the FQDN form query
+	if strings.HasSuffix(domain, ".") {
+		domain = domain[:len(domain)-1]
+	}
+
+	// Static host lookup
+	switch addrs := s.hosts.Lookup(domain, option); {
+	case addrs == nil: // Domain not recorded in static host
+		break
+	case len(addrs) == 0: // Domain recorded, but no valid IP returned (e.g. IPv4 address with only IPv6 enabled)
+		return nil, dns.ErrEmptyResponse
+	case len(addrs) == 1 && addrs[0].Family().IsDomain(): // Domain replacement
+		newError("domain replaced: ", domain, " -> ", addrs[0].Domain()).WriteToLog()
+		domain = addrs[0].Domain()
+	default: // Successfully found ip records in static host
+		newError("returning ", len(addrs), " IPs for domain ", domain).WriteToLog()
+		return toNetIP(addrs)
+	}
+
+	// Name servers lookup
+	errs := []error{}
+	ctx := session.ContextWithInbound(s.ctx, &session.Inbound{Tag: s.tag})
+	for _, client := range s.sortClients(domain) {
+		if !option.FakeEnable && strings.EqualFold(client.Name(), "FakeDNS") {
+			newError("skip DNS resolution for domain ", domain, " at server ", client.Name()).AtDebug().WriteToLog()
+			continue
+		}
+		ips, err := client.QueryIP(ctx, domain, option, s.disableCache)
+		if len(ips) > 0 {
+			return ips, nil
+		}
+		if err != nil {
+			newError("failed to lookup ip for domain ", domain, " at server ", client.Name()).Base(err).WriteToLog()
+			errs = append(errs, err)
+		}
+		if err != context.Canceled && err != context.DeadlineExceeded && err != errExpectedIPNonMatch {
+			return nil, err
+		}
+	}
+
+	return nil, newError("returning nil for domain ", domain).Base(errors.Combine(errs...))
+}
+
+func (s *DNS) sortClients(domain string) []*Client {
+	clients := make([]*Client, 0, len(s.clients))
+	clientUsed := make([]bool, len(s.clients))
+	clientNames := make([]string, 0, len(s.clients))
+	domainRules := []string{}
+
+	// Priority domain matching
+	for _, match := range s.domainMatcher.Match(domain) {
+		info := s.matcherInfos[match]
+		client := s.clients[info.clientIdx]
+		domainRule := client.domains[info.domainRuleIdx]
+		domainRules = append(domainRules, fmt.Sprintf("%s(DNS idx:%d)", domainRule, info.clientIdx))
+		if clientUsed[info.clientIdx] {
+			continue
+		}
+		clientUsed[info.clientIdx] = true
+		clients = append(clients, client)
+		clientNames = append(clientNames, client.Name())
+	}
+
+	// Default round-robin query
+	for idx, client := range s.clients {
+		if clientUsed[idx] {
+			continue
+		}
+		clientUsed[idx] = true
+		clients = append(clients, client)
+		clientNames = append(clientNames, client.Name())
+	}
+
+	if len(domainRules) > 0 {
+		newError("domain ", domain, " matches following rules: ", domainRules).AtDebug().WriteToLog()
+	}
+	if len(clientNames) > 0 {
+		newError("domain ", domain, " will use DNS in order: ", clientNames).AtDebug().WriteToLog()
+	}
+	return clients
+}
+
+func init() {
+	common.Must(common.RegisterConfig((*Config)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
+		return New(ctx, config.(*Config))
+	}))
+}