Refactoring: DNS App

app/dns/config.go

@@ -0,0 +1,65 @@
+// +build !confonly
+
+package dns
+
+import (
+	"v2ray.com/core/common/net"
+	"v2ray.com/core/common/strmatcher"
+	"v2ray.com/core/common/uuid"
+)
+
+var typeMap = map[DomainMatchingType]strmatcher.Type{
+	DomainMatchingType_Full:      strmatcher.Full,
+	DomainMatchingType_Subdomain: strmatcher.Domain,
+	DomainMatchingType_Keyword:   strmatcher.Substr,
+	DomainMatchingType_Regex:     strmatcher.Regex,
+}
+
+// References:
+// https://www.iana.org/assignments/special-use-domain-names/special-use-domain-names.xhtml
+// https://unix.stackexchange.com/questions/92441/whats-the-difference-between-local-home-and-lan
+var localTLDsAndDotlessDomains = []*NameServer_PriorityDomain{
+	{Type: DomainMatchingType_Regex, Domain: "^[^.]+$"}, // This will only match domains without any dot
+	{Type: DomainMatchingType_Subdomain, Domain: "local"},
+	{Type: DomainMatchingType_Subdomain, Domain: "localdomain"},
+	{Type: DomainMatchingType_Subdomain, Domain: "localhost"},
+	{Type: DomainMatchingType_Subdomain, Domain: "lan"},
+	{Type: DomainMatchingType_Subdomain, Domain: "home.arpa"},
+	{Type: DomainMatchingType_Subdomain, Domain: "example"},
+	{Type: DomainMatchingType_Subdomain, Domain: "invalid"},
+	{Type: DomainMatchingType_Subdomain, Domain: "test"},
+}
+
+var localTLDsAndDotlessDomainsRule = &NameServer_OriginalRule{
+	Rule: "geosite:private",
+	Size: uint32(len(localTLDsAndDotlessDomains)),
+}
+
+func toStrMatcher(t DomainMatchingType, domain string) (strmatcher.Matcher, error) {
+	strMType, f := typeMap[t]
+	if !f {
+		return nil, newError("unknown mapping type", t).AtWarning()
+	}
+	matcher, err := strMType.New(domain)
+	if err != nil {
+		return nil, newError("failed to create str matcher").Base(err)
+	}
+	return matcher, nil
+}
+
+func toNetIP(addrs []net.Address) ([]net.IP, error) {
+	ips := make([]net.IP, 0, len(addrs))
+	for _, addr := range addrs {
+		if addr.Family().IsIP() {
+			ips = append(ips, addr.IP())
+		} else {
+			return nil, newError("Failed to convert address", addr, "to Net IP.").AtWarning()
+		}
+	}
+	return ips, nil
+}
+
+func generateRandomTag() string {
+	id := uuid.New()
+	return "v2ray.system." + id.String()
+}

app/dns/dns.go

@@ -1,4 +1,243 @@
+// +build !confonly
+
 // Package dns is an implementation of core.DNS feature.
 package dns
 
 //go:generate errorgen
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"v2ray.com/core/app/router"
+	"v2ray.com/core/common"
+	"v2ray.com/core/common/errors"
+	"v2ray.com/core/common/net"
+	"v2ray.com/core/common/session"
+	"v2ray.com/core/common/strmatcher"
+	"v2ray.com/core/features"
+	"v2ray.com/core/features/dns"
+)
+
+// DNS is a DNS rely server.
+type DNS struct {
+	sync.Mutex
+	tag     string
+	hosts   *StaticHosts
+	clients []*Client
+
+	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) error {
+			midx := domainMatcher.Add(domainRule)
+			matcherInfos[midx] = DomainMatcherInfo{
+				clientIdx:     uint16(clientIdx),
+				domainRuleIdx: uint16(originalRuleIdx),
+			}
+			return nil
+		}
+		client, err := NewClient(ctx, ns, clientIP, geoipContainer, updateDomain)
+		if err != nil {
+			return nil, newError("failed to create client").Base(err)
+		}
+		clients = append(clients, client)
+	}
+
+	if len(clients) == 0 {
+		clients = append(clients, NewLocalDNSClient())
+	}
+
+	return &DNS{
+		tag:           tag,
+		hosts:         hosts,
+		clients:       clients,
+		domainMatcher: domainMatcher,
+		matcherInfos:  matcherInfos,
+	}, 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) ([]net.IP, error) {
+	return s.lookupIPInternal(domain, IPOption{
+		IPv4Enable: true,
+		IPv6Enable: true,
+	})
+}
+
+// LookupIPv4 implements dns.IPv4Lookup.
+func (s *DNS) LookupIPv4(domain string) ([]net.IP, error) {
+	return s.lookupIPInternal(domain, IPOption{
+		IPv4Enable: true,
+		IPv6Enable: false,
+	})
+}
+
+// LookupIPv6 implements dns.IPv6Lookup.
+func (s *DNS) LookupIPv6(domain string) ([]net.IP, error) {
+	return s.lookupIPInternal(domain, IPOption{
+		IPv4Enable: false,
+		IPv6Enable: true,
+	})
+}
+
+func (s *DNS) lookupIPInternal(domain string, option IPOption) ([]net.IP, error) {
+	if domain == "" {
+		return nil, newError("empty domain name")
+	}
+
+	// Normalize the FQDN form query
+	if domain[len(domain)-1] == '.' {
+		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(context.Background(), &session.Inbound{Tag: s.tag})
+	for _, client := range s.sortClients(domain) {
+		ips, err := client.QueryIP(ctx, domain, option)
+		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))
+	}))
+}

app/dns/hosts.go

@@ -15,25 +15,6 @@ type StaticHosts struct {
 	matchers *strmatcher.MatcherGroup
 }
 
-var typeMap = map[DomainMatchingType]strmatcher.Type{
-	DomainMatchingType_Full:      strmatcher.Full,
-	DomainMatchingType_Subdomain: strmatcher.Domain,
-	DomainMatchingType_Keyword:   strmatcher.Substr,
-	DomainMatchingType_Regex:     strmatcher.Regex,
-}
-
-func toStrMatcher(t DomainMatchingType, domain string) (strmatcher.Matcher, error) {
-	strMType, f := typeMap[t]
-	if !f {
-		return nil, newError("unknown mapping type", t).AtWarning()
-	}
-	matcher, err := strMType.New(domain)
-	if err != nil {
-		return nil, newError("failed to create str matcher").Base(err)
-	}
-	return matcher, nil
-}
-
 // NewStaticHosts creates a new StaticHosts instance.
 func NewStaticHosts(hosts []*Config_HostMapping, legacy map[string]*net.IPOrDomain) (*StaticHosts, error) {
 	g := new(strmatcher.MatcherGroup)
@@ -98,24 +79,35 @@ func filterIP(ips []net.Address, option IPOption) []net.Address {
 			filtered = append(filtered, ip)
 		}
 	}
-	if len(filtered) == 0 {
-		return nil
-	}
 	return filtered
 }
 
-// LookupIP returns IP address for the given domain, if exists in this StaticHosts.
-func (h *StaticHosts) LookupIP(domain string, option IPOption) []net.Address {
-	indices := h.matchers.Match(domain)
-	if len(indices) == 0 {
-		return nil
-	}
-	ips := []net.Address{}
-	for _, id := range indices {
+func (h *StaticHosts) lookupInternal(domain string) []net.Address {
+	var ips []net.Address
+	for _, id := range h.matchers.Match(domain) {
 		ips = append(ips, h.ips[id]...)
 	}
-	if len(ips) == 1 && ips[0].Family().IsDomain() {
-		return ips
+	return ips
+}
+
+func (h *StaticHosts) lookup(domain string, option IPOption, maxDepth int) []net.Address {
+	switch addrs := h.lookupInternal(domain); {
+	case len(addrs) == 0: // Not recorded in static hosts, return nil
+		return nil
+	case len(addrs) == 1 && addrs[0].Family().IsDomain(): // Try to unwrap domain
+		if maxDepth > 0 {
+			unwrapped := h.lookup(addrs[0].Domain(), option, maxDepth-1)
+			if unwrapped != nil {
+				return unwrapped
+			}
+		}
+		return addrs
+	default: // IP record found, return a non-nil IP array
+		return filterIP(addrs, option)
 	}
-	return filterIP(ips, option)
+}
+
+// Lookup returns IP addresses or proxied domain for the given domain, if exists in this StaticHosts.
+func (h *StaticHosts) Lookup(domain string, option IPOption) []net.Address {
+	return h.lookup(domain, option, 5)
 }