mirror of https://github.com/XTLS/Xray-core
376 lines
8.8 KiB
Go
376 lines
8.8 KiB
Go
package dns
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import (
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"bytes"
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"context"
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"encoding/binary"
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"net/url"
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"sync"
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"sync/atomic"
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"time"
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"github.com/xtls/xray-core/common"
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"github.com/xtls/xray-core/common/buf"
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"github.com/xtls/xray-core/common/errors"
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"github.com/xtls/xray-core/common/log"
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"github.com/xtls/xray-core/common/net"
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"github.com/xtls/xray-core/common/net/cnc"
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"github.com/xtls/xray-core/common/protocol/dns"
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"github.com/xtls/xray-core/common/session"
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"github.com/xtls/xray-core/common/signal/pubsub"
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"github.com/xtls/xray-core/common/task"
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dns_feature "github.com/xtls/xray-core/features/dns"
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"github.com/xtls/xray-core/features/routing"
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"github.com/xtls/xray-core/transport/internet"
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"golang.org/x/net/dns/dnsmessage"
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)
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// TCPNameServer implemented DNS over TCP (RFC7766).
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type TCPNameServer struct {
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sync.RWMutex
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name string
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destination *net.Destination
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ips map[string]*record
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pub *pubsub.Service
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cleanup *task.Periodic
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reqID uint32
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dial func(context.Context) (net.Conn, error)
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queryStrategy QueryStrategy
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}
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// NewTCPNameServer creates DNS over TCP server object for remote resolving.
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func NewTCPNameServer(
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url *url.URL,
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dispatcher routing.Dispatcher,
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queryStrategy QueryStrategy,
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) (*TCPNameServer, error) {
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s, err := baseTCPNameServer(url, "TCP", queryStrategy)
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if err != nil {
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return nil, err
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}
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s.dial = func(ctx context.Context) (net.Conn, error) {
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link, err := dispatcher.Dispatch(toDnsContext(ctx, s.destination.String()), *s.destination)
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if err != nil {
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return nil, err
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}
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return cnc.NewConnection(
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cnc.ConnectionInputMulti(link.Writer),
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cnc.ConnectionOutputMulti(link.Reader),
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), nil
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}
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return s, nil
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}
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// NewTCPLocalNameServer creates DNS over TCP client object for local resolving
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func NewTCPLocalNameServer(url *url.URL, queryStrategy QueryStrategy) (*TCPNameServer, error) {
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s, err := baseTCPNameServer(url, "TCPL", queryStrategy)
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if err != nil {
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return nil, err
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}
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s.dial = func(ctx context.Context) (net.Conn, error) {
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return internet.DialSystem(ctx, *s.destination, nil)
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}
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return s, nil
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}
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func baseTCPNameServer(url *url.URL, prefix string, queryStrategy QueryStrategy) (*TCPNameServer, error) {
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port := net.Port(53)
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if url.Port() != "" {
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var err error
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if port, err = net.PortFromString(url.Port()); err != nil {
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return nil, err
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}
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}
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dest := net.TCPDestination(net.ParseAddress(url.Hostname()), port)
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s := &TCPNameServer{
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destination: &dest,
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ips: make(map[string]*record),
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pub: pubsub.NewService(),
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name: prefix + "//" + dest.NetAddr(),
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queryStrategy: queryStrategy,
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}
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s.cleanup = &task.Periodic{
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Interval: time.Minute,
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Execute: s.Cleanup,
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}
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return s, nil
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}
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// Name implements Server.
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func (s *TCPNameServer) Name() string {
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return s.name
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}
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// Cleanup clears expired items from cache
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func (s *TCPNameServer) Cleanup() error {
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now := time.Now()
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s.Lock()
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defer s.Unlock()
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if len(s.ips) == 0 {
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return errors.New("nothing to do. stopping...")
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}
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for domain, record := range s.ips {
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if record.A != nil && record.A.Expire.Before(now) {
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record.A = nil
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}
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if record.AAAA != nil && record.AAAA.Expire.Before(now) {
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record.AAAA = nil
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}
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if record.A == nil && record.AAAA == nil {
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errors.LogDebug(context.Background(), s.name, " cleanup ", domain)
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delete(s.ips, domain)
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} else {
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s.ips[domain] = record
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}
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}
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if len(s.ips) == 0 {
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s.ips = make(map[string]*record)
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}
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return nil
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}
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func (s *TCPNameServer) updateIP(req *dnsRequest, ipRec *IPRecord) {
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elapsed := time.Since(req.start)
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s.Lock()
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rec, found := s.ips[req.domain]
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if !found {
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rec = &record{}
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}
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updated := false
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switch req.reqType {
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case dnsmessage.TypeA:
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if isNewer(rec.A, ipRec) {
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rec.A = ipRec
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updated = true
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}
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case dnsmessage.TypeAAAA:
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addr := make([]net.Address, 0)
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for _, ip := range ipRec.IP {
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if len(ip.IP()) == net.IPv6len {
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addr = append(addr, ip)
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}
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}
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ipRec.IP = addr
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if isNewer(rec.AAAA, ipRec) {
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rec.AAAA = ipRec
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updated = true
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}
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}
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errors.LogInfo(context.Background(), s.name, " got answer: ", req.domain, " ", req.reqType, " -> ", ipRec.IP, " ", elapsed)
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if updated {
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s.ips[req.domain] = rec
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}
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switch req.reqType {
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case dnsmessage.TypeA:
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s.pub.Publish(req.domain+"4", nil)
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case dnsmessage.TypeAAAA:
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s.pub.Publish(req.domain+"6", nil)
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}
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s.Unlock()
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common.Must(s.cleanup.Start())
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}
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func (s *TCPNameServer) newReqID() uint16 {
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return uint16(atomic.AddUint32(&s.reqID, 1))
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}
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func (s *TCPNameServer) sendQuery(ctx context.Context, domain string, clientIP net.IP, option dns_feature.IPOption) {
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errors.LogDebug(ctx, s.name, " querying DNS for: ", domain)
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reqs := buildReqMsgs(domain, option, s.newReqID, genEDNS0Options(clientIP))
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var deadline time.Time
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if d, ok := ctx.Deadline(); ok {
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deadline = d
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} else {
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deadline = time.Now().Add(time.Second * 5)
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}
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for _, req := range reqs {
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go func(r *dnsRequest) {
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dnsCtx := ctx
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if inbound := session.InboundFromContext(ctx); inbound != nil {
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dnsCtx = session.ContextWithInbound(dnsCtx, inbound)
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}
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dnsCtx = session.ContextWithContent(dnsCtx, &session.Content{
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Protocol: "dns",
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SkipDNSResolve: true,
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})
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var cancel context.CancelFunc
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dnsCtx, cancel = context.WithDeadline(dnsCtx, deadline)
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defer cancel()
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b, err := dns.PackMessage(r.msg)
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if err != nil {
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errors.LogErrorInner(ctx, err, "failed to pack dns query")
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return
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}
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conn, err := s.dial(dnsCtx)
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if err != nil {
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errors.LogErrorInner(ctx, err, "failed to dial namesever")
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return
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}
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defer conn.Close()
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dnsReqBuf := buf.New()
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binary.Write(dnsReqBuf, binary.BigEndian, uint16(b.Len()))
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dnsReqBuf.Write(b.Bytes())
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b.Release()
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_, err = conn.Write(dnsReqBuf.Bytes())
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if err != nil {
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errors.LogErrorInner(ctx, err, "failed to send query")
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return
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}
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dnsReqBuf.Release()
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respBuf := buf.New()
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defer respBuf.Release()
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n, err := respBuf.ReadFullFrom(conn, 2)
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if err != nil && n == 0 {
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errors.LogErrorInner(ctx, err, "failed to read response length")
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return
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}
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var length int16
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err = binary.Read(bytes.NewReader(respBuf.Bytes()), binary.BigEndian, &length)
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if err != nil {
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errors.LogErrorInner(ctx, err, "failed to parse response length")
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return
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}
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respBuf.Clear()
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n, err = respBuf.ReadFullFrom(conn, int32(length))
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if err != nil && n == 0 {
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errors.LogErrorInner(ctx, err, "failed to read response length")
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return
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}
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rec, err := parseResponse(respBuf.Bytes())
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if err != nil {
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errors.LogErrorInner(ctx, err, "failed to parse DNS over TCP response")
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return
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}
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s.updateIP(r, rec)
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}(req)
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}
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}
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func (s *TCPNameServer) findIPsForDomain(domain string, option dns_feature.IPOption) ([]net.IP, error) {
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s.RLock()
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record, found := s.ips[domain]
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s.RUnlock()
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if !found {
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return nil, errRecordNotFound
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}
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var err4 error
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var err6 error
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var ips []net.Address
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var ip6 []net.Address
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if option.IPv4Enable {
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ips, err4 = record.A.getIPs()
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}
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if option.IPv6Enable {
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ip6, err6 = record.AAAA.getIPs()
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ips = append(ips, ip6...)
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}
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if len(ips) > 0 {
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return toNetIP(ips)
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}
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if err4 != nil {
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return nil, err4
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}
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if err6 != nil {
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return nil, err6
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}
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return nil, dns_feature.ErrEmptyResponse
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}
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// QueryIP implements Server.
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func (s *TCPNameServer) QueryIP(ctx context.Context, domain string, clientIP net.IP, option dns_feature.IPOption, disableCache bool) ([]net.IP, error) {
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fqdn := Fqdn(domain)
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option = ResolveIpOptionOverride(s.queryStrategy, option)
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if !option.IPv4Enable && !option.IPv6Enable {
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return nil, dns_feature.ErrEmptyResponse
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}
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if disableCache {
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errors.LogDebug(ctx, "DNS cache is disabled. Querying IP for ", domain, " at ", s.name)
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} else {
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ips, err := s.findIPsForDomain(fqdn, option)
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if err != errRecordNotFound {
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errors.LogDebugInner(ctx, err, s.name, " cache HIT ", domain, " -> ", ips)
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log.Record(&log.DNSLog{Server: s.name, Domain: domain, Result: ips, Status: log.DNSCacheHit, Elapsed: 0, Error: err})
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return ips, err
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}
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}
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// ipv4 and ipv6 belong to different subscription groups
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var sub4, sub6 *pubsub.Subscriber
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if option.IPv4Enable {
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sub4 = s.pub.Subscribe(fqdn + "4")
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defer sub4.Close()
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}
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if option.IPv6Enable {
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sub6 = s.pub.Subscribe(fqdn + "6")
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defer sub6.Close()
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}
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done := make(chan interface{})
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go func() {
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if sub4 != nil {
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select {
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case <-sub4.Wait():
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case <-ctx.Done():
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}
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}
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if sub6 != nil {
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select {
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case <-sub6.Wait():
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case <-ctx.Done():
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}
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}
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close(done)
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}()
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s.sendQuery(ctx, fqdn, clientIP, option)
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start := time.Now()
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for {
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ips, err := s.findIPsForDomain(fqdn, option)
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if err != errRecordNotFound {
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log.Record(&log.DNSLog{Server: s.name, Domain: domain, Result: ips, Status: log.DNSQueried, Elapsed: time.Since(start), Error: err})
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return ips, err
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}
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select {
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case <-ctx.Done():
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return nil, ctx.Err()
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case <-done:
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}
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}
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}
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