clash/dns/resolver.go

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package dns
import (
"context"
"errors"
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"fmt"
"math/rand"
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"net"
"strings"
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"time"
"github.com/Dreamacro/clash/common/cache"
"github.com/Dreamacro/clash/common/picker"
"github.com/Dreamacro/clash/component/fakeip"
"github.com/Dreamacro/clash/component/resolver"
"github.com/Dreamacro/clash/component/trie"
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D "github.com/miekg/dns"
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"golang.org/x/sync/singleflight"
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)
type dnsClient interface {
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Exchange(m *D.Msg) (msg *D.Msg, err error)
ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.Msg, err error)
}
type result struct {
Msg *D.Msg
Error error
}
type Resolver struct {
ipv6 bool
hosts *trie.DomainTrie
main []dnsClient
fallback []dnsClient
fallbackDomainFilters []fallbackDomainFilter
fallbackIPFilters []fallbackIPFilter
group singleflight.Group
lruCache *cache.LruCache
policy *trie.DomainTrie
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}
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// ResolveIP request with TypeA and TypeAAAA, priority return TypeA
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func (r *Resolver) ResolveIP(host string) (ip net.IP, err error) {
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ch := make(chan net.IP, 1)
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go func() {
defer close(ch)
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ip, err := r.resolveIP(host, D.TypeAAAA)
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if err != nil {
return
}
ch <- ip
}()
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ip, err = r.resolveIP(host, D.TypeA)
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if err == nil {
return
}
ip, open := <-ch
if !open {
return nil, resolver.ErrIPNotFound
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}
return ip, nil
}
// ResolveIPv4 request with TypeA
func (r *Resolver) ResolveIPv4(host string) (ip net.IP, err error) {
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return r.resolveIP(host, D.TypeA)
}
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// ResolveIPv6 request with TypeAAAA
func (r *Resolver) ResolveIPv6(host string) (ip net.IP, err error) {
return r.resolveIP(host, D.TypeAAAA)
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}
func (r *Resolver) shouldIPFallback(ip net.IP) bool {
for _, filter := range r.fallbackIPFilters {
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if filter.Match(ip) {
return true
}
}
return false
}
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// Exchange a batch of dns request, and it use cache
func (r *Resolver) Exchange(m *D.Msg) (msg *D.Msg, err error) {
if len(m.Question) == 0 {
return nil, errors.New("should have one question at least")
}
q := m.Question[0]
cache, expireTime, hit := r.lruCache.GetWithExpire(q.String())
if hit {
now := time.Now()
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msg = cache.(*D.Msg).Copy()
if expireTime.Before(now) {
setMsgTTL(msg, uint32(1)) // Continue fetch
go r.exchangeWithoutCache(m)
} else {
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setMsgTTL(msg, uint32(time.Until(expireTime).Seconds()))
}
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return
}
return r.exchangeWithoutCache(m)
}
// ExchangeWithoutCache a batch of dns request, and it do NOT GET from cache
func (r *Resolver) exchangeWithoutCache(m *D.Msg) (msg *D.Msg, err error) {
q := m.Question[0]
ret, err, shared := r.group.Do(q.String(), func() (result interface{}, err error) {
defer func() {
if err != nil {
return
}
msg := result.(*D.Msg)
putMsgToCache(r.lruCache, q.String(), msg)
}()
isIPReq := isIPRequest(q)
if isIPReq {
return r.ipExchange(m)
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}
if matched := r.matchPolicy(m); len(matched) != 0 {
return r.batchExchange(matched, m)
}
return r.batchExchange(r.main, m)
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})
if err == nil {
msg = ret.(*D.Msg)
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if shared {
msg = msg.Copy()
}
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}
return
}
func (r *Resolver) batchExchange(clients []dnsClient, m *D.Msg) (msg *D.Msg, err error) {
fast, ctx := picker.WithTimeout(context.Background(), resolver.DefaultDNSTimeout)
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for _, client := range clients {
r := client
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fast.Go(func() (interface{}, error) {
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m, err := r.ExchangeContext(ctx, m)
if err != nil {
return nil, err
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} else if m.Rcode == D.RcodeServerFailure || m.Rcode == D.RcodeRefused {
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return nil, errors.New("server failure")
}
return m, nil
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})
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}
elm := fast.Wait()
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if elm == nil {
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err := errors.New("all DNS requests failed")
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if fErr := fast.Error(); fErr != nil {
err = fmt.Errorf("%w, first error: %s", err, fErr.Error())
}
return nil, err
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}
msg = elm.(*D.Msg)
return
}
func (r *Resolver) matchPolicy(m *D.Msg) []dnsClient {
if r.policy == nil {
return nil
}
domain := r.msgToDomain(m)
if domain == "" {
return nil
}
record := r.policy.Search(domain)
if record == nil {
return nil
}
return record.Data.([]dnsClient)
}
func (r *Resolver) shouldOnlyQueryFallback(m *D.Msg) bool {
if r.fallback == nil || len(r.fallbackDomainFilters) == 0 {
return false
}
domain := r.msgToDomain(m)
if domain == "" {
return false
}
for _, df := range r.fallbackDomainFilters {
if df.Match(domain) {
return true
}
}
return false
}
func (r *Resolver) ipExchange(m *D.Msg) (msg *D.Msg, err error) {
if matched := r.matchPolicy(m); len(matched) != 0 {
res := <-r.asyncExchange(matched, m)
return res.Msg, res.Error
}
onlyFallback := r.shouldOnlyQueryFallback(m)
if onlyFallback {
res := <-r.asyncExchange(r.fallback, m)
return res.Msg, res.Error
}
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msgCh := r.asyncExchange(r.main, m)
if r.fallback == nil { // directly return if no fallback servers are available
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res := <-msgCh
msg, err = res.Msg, res.Error
return
}
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fallbackMsg := r.asyncExchange(r.fallback, m)
res := <-msgCh
if res.Error == nil {
if ips := msgToIP(res.Msg); len(ips) != 0 {
if !r.shouldIPFallback(ips[0]) {
msg = res.Msg // no need to wait for fallback result
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err = res.Error
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return msg, err
}
}
}
res = <-fallbackMsg
msg, err = res.Msg, res.Error
return
}
func (r *Resolver) resolveIP(host string, dnsType uint16) (ip net.IP, err error) {
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ip = net.ParseIP(host)
if ip != nil {
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isIPv4 := ip.To4() != nil
if dnsType == D.TypeAAAA && !isIPv4 {
return ip, nil
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} else if dnsType == D.TypeA && isIPv4 {
return ip, nil
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} else {
return nil, resolver.ErrIPVersion
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}
}
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query := &D.Msg{}
query.SetQuestion(D.Fqdn(host), dnsType)
msg, err := r.Exchange(query)
if err != nil {
return nil, err
}
ips := msgToIP(msg)
ipLength := len(ips)
if ipLength == 0 {
return nil, resolver.ErrIPNotFound
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}
ip = ips[rand.Intn(ipLength)]
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return
}
func (r *Resolver) msgToDomain(msg *D.Msg) string {
if len(msg.Question) > 0 {
return strings.TrimRight(msg.Question[0].Name, ".")
}
return ""
}
func (r *Resolver) asyncExchange(client []dnsClient, msg *D.Msg) <-chan *result {
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ch := make(chan *result, 1)
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go func() {
res, err := r.batchExchange(client, msg)
ch <- &result{Msg: res, Error: err}
}()
return ch
}
type NameServer struct {
Net string
Addr string
}
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type FallbackFilter struct {
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GeoIP bool
GeoIPCode string
IPCIDR []*net.IPNet
Domain []string
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}
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type Config struct {
Main, Fallback []NameServer
Default []NameServer
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IPv6 bool
EnhancedMode EnhancedMode
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FallbackFilter FallbackFilter
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Pool *fakeip.Pool
Hosts *trie.DomainTrie
Policy map[string]NameServer
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}
func NewResolver(config Config) *Resolver {
defaultResolver := &Resolver{
main: transform(config.Default, nil),
lruCache: cache.NewLRUCache(cache.WithSize(4096), cache.WithStale(true)),
}
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r := &Resolver{
ipv6: config.IPv6,
main: transform(config.Main, defaultResolver),
lruCache: cache.NewLRUCache(cache.WithSize(4096), cache.WithStale(true)),
hosts: config.Hosts,
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}
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if len(config.Fallback) != 0 {
r.fallback = transform(config.Fallback, defaultResolver)
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}
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if len(config.Policy) != 0 {
r.policy = trie.New()
for domain, nameserver := range config.Policy {
r.policy.Insert(domain, transform([]NameServer{nameserver}, defaultResolver))
}
}
fallbackIPFilters := []fallbackIPFilter{}
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if config.FallbackFilter.GeoIP {
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fallbackIPFilters = append(fallbackIPFilters, &geoipFilter{
code: config.FallbackFilter.GeoIPCode,
})
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}
for _, ipnet := range config.FallbackFilter.IPCIDR {
fallbackIPFilters = append(fallbackIPFilters, &ipnetFilter{ipnet: ipnet})
}
r.fallbackIPFilters = fallbackIPFilters
if len(config.FallbackFilter.Domain) != 0 {
fallbackDomainFilters := []fallbackDomainFilter{NewDomainFilter(config.FallbackFilter.Domain)}
r.fallbackDomainFilters = fallbackDomainFilters
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}
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return r
}