Skip to content
Permalink
Branch: master
Find file Copy path
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
454 lines (382 sloc) 9.48 KB
// +build !confonly
package dns
import (
"context"
"encoding/binary"
"sync"
"sync/atomic"
"time"
"golang.org/x/net/dns/dnsmessage"
"v2ray.com/core/common"
"v2ray.com/core/common/errors"
"v2ray.com/core/common/net"
"v2ray.com/core/common/protocol/dns"
udp_proto "v2ray.com/core/common/protocol/udp"
"v2ray.com/core/common/session"
"v2ray.com/core/common/signal/pubsub"
"v2ray.com/core/common/task"
dns_feature "v2ray.com/core/features/dns"
"v2ray.com/core/features/routing"
"v2ray.com/core/transport/internet/udp"
)
type record struct {
A *IPRecord
AAAA *IPRecord
}
type IPRecord struct {
IP []net.Address
Expire time.Time
RCode dnsmessage.RCode
}
func (r *IPRecord) getIPs() ([]net.Address, error) {
if r == nil || r.Expire.Before(time.Now()) {
return nil, errRecordNotFound
}
if r.RCode != dnsmessage.RCodeSuccess {
return nil, dns_feature.RCodeError(r.RCode)
}
return r.IP, nil
}
type pendingRequest struct {
domain string
expire time.Time
recType dnsmessage.Type
}
var (
errRecordNotFound = errors.New("record not found")
)
type ClassicNameServer struct {
sync.RWMutex
address net.Destination
ips map[string]record
requests map[uint16]pendingRequest
pub *pubsub.Service
udpServer *udp.Dispatcher
cleanup *task.Periodic
reqID uint32
clientIP net.IP
}
func NewClassicNameServer(address net.Destination, dispatcher routing.Dispatcher, clientIP net.IP) *ClassicNameServer {
s := &ClassicNameServer{
address: address,
ips: make(map[string]record),
requests: make(map[uint16]pendingRequest),
clientIP: clientIP,
pub: pubsub.NewService(),
}
s.cleanup = &task.Periodic{
Interval: time.Minute,
Execute: s.Cleanup,
}
s.udpServer = udp.NewDispatcher(dispatcher, s.HandleResponse)
return s
}
func (s *ClassicNameServer) Name() string {
return s.address.String()
}
func (s *ClassicNameServer) Cleanup() error {
now := time.Now()
s.Lock()
defer s.Unlock()
if len(s.ips) == 0 && len(s.requests) == 0 {
return newError("nothing to do. stopping...")
}
for domain, record := range s.ips {
if record.A != nil && record.A.Expire.Before(now) {
record.A = nil
}
if record.AAAA != nil && record.AAAA.Expire.Before(now) {
record.AAAA = nil
}
if record.A == nil && record.AAAA == nil {
delete(s.ips, domain)
} else {
s.ips[domain] = record
}
}
if len(s.ips) == 0 {
s.ips = make(map[string]record)
}
for id, req := range s.requests {
if req.expire.Before(now) {
delete(s.requests, id)
}
}
if len(s.requests) == 0 {
s.requests = make(map[uint16]pendingRequest)
}
return nil
}
func (s *ClassicNameServer) HandleResponse(ctx context.Context, packet *udp_proto.Packet) {
payload := packet.Payload
var parser dnsmessage.Parser
header, err := parser.Start(payload.Bytes())
if err != nil {
newError("failed to parse DNS response").Base(err).AtWarning().WriteToLog()
return
}
if err := parser.SkipAllQuestions(); err != nil {
newError("failed to skip questions in DNS response").Base(err).AtWarning().WriteToLog()
return
}
id := header.ID
s.Lock()
req, f := s.requests[id]
if f {
delete(s.requests, id)
}
s.Unlock()
if !f {
return
}
domain := req.domain
recType := req.recType
now := time.Now()
ipRecord := &IPRecord{
RCode: header.RCode,
Expire: now.Add(time.Second * 600),
}
L:
for {
header, err := parser.AnswerHeader()
if err != nil {
if err != dnsmessage.ErrSectionDone {
newError("failed to parse answer section for domain: ", domain).Base(err).WriteToLog()
}
break
}
ttl := header.TTL
if ttl == 0 {
ttl = 600
}
expire := now.Add(time.Duration(ttl) * time.Second)
if ipRecord.Expire.After(expire) {
ipRecord.Expire = expire
}
if header.Type != recType {
if err := parser.SkipAnswer(); err != nil {
newError("failed to skip answer").Base(err).WriteToLog()
break L
}
continue
}
switch header.Type {
case dnsmessage.TypeA:
ans, err := parser.AResource()
if err != nil {
newError("failed to parse A record for domain: ", domain).Base(err).WriteToLog()
break L
}
ipRecord.IP = append(ipRecord.IP, net.IPAddress(ans.A[:]))
case dnsmessage.TypeAAAA:
ans, err := parser.AAAAResource()
if err != nil {
newError("failed to parse A record for domain: ", domain).Base(err).WriteToLog()
break L
}
ipRecord.IP = append(ipRecord.IP, net.IPAddress(ans.AAAA[:]))
default:
if err := parser.SkipAnswer(); err != nil {
newError("failed to skip answer").Base(err).WriteToLog()
break L
}
}
}
var rec record
switch recType {
case dnsmessage.TypeA:
rec.A = ipRecord
case dnsmessage.TypeAAAA:
rec.AAAA = ipRecord
}
if len(domain) > 0 && (rec.A != nil || rec.AAAA != nil) {
s.updateIP(domain, rec)
}
}
func isNewer(baseRec *IPRecord, newRec *IPRecord) bool {
if newRec == nil {
return false
}
if baseRec == nil {
return true
}
return baseRec.Expire.Before(newRec.Expire)
}
func (s *ClassicNameServer) updateIP(domain string, newRec record) {
s.Lock()
newError("updating IP records for domain:", domain).AtDebug().WriteToLog()
rec := s.ips[domain]
updated := false
if isNewer(rec.A, newRec.A) {
rec.A = newRec.A
updated = true
}
if isNewer(rec.AAAA, newRec.AAAA) {
rec.AAAA = newRec.AAAA
updated = true
}
if updated {
s.ips[domain] = rec
s.pub.Publish(domain, nil)
}
s.Unlock()
common.Must(s.cleanup.Start())
}
func (s *ClassicNameServer) getMsgOptions() *dnsmessage.Resource {
if len(s.clientIP) == 0 {
return nil
}
var netmask int
var family uint16
if len(s.clientIP) == 4 {
family = 1
netmask = 24 // 24 for IPV4, 96 for IPv6
} else {
family = 2
netmask = 96
}
b := make([]byte, 4)
binary.BigEndian.PutUint16(b[0:], family)
b[2] = byte(netmask)
b[3] = 0
switch family {
case 1:
ip := s.clientIP.To4().Mask(net.CIDRMask(netmask, net.IPv4len*8))
needLength := (netmask + 8 - 1) / 8 // division rounding up
b = append(b, ip[:needLength]...)
case 2:
ip := s.clientIP.Mask(net.CIDRMask(netmask, net.IPv6len*8))
needLength := (netmask + 8 - 1) / 8 // division rounding up
b = append(b, ip[:needLength]...)
}
const EDNS0SUBNET = 0x08
opt := new(dnsmessage.Resource)
common.Must(opt.Header.SetEDNS0(1350, 0xfe00, true))
opt.Body = &dnsmessage.OPTResource{
Options: []dnsmessage.Option{
{
Code: EDNS0SUBNET,
Data: b,
},
},
}
return opt
}
func (s *ClassicNameServer) addPendingRequest(domain string, recType dnsmessage.Type) uint16 {
id := uint16(atomic.AddUint32(&s.reqID, 1))
s.Lock()
defer s.Unlock()
s.requests[id] = pendingRequest{
domain: domain,
expire: time.Now().Add(time.Second * 8),
recType: recType,
}
return id
}
func (s *ClassicNameServer) buildMsgs(domain string, option IPOption) []*dnsmessage.Message {
qA := dnsmessage.Question{
Name: dnsmessage.MustNewName(domain),
Type: dnsmessage.TypeA,
Class: dnsmessage.ClassINET,
}
qAAAA := dnsmessage.Question{
Name: dnsmessage.MustNewName(domain),
Type: dnsmessage.TypeAAAA,
Class: dnsmessage.ClassINET,
}
var msgs []*dnsmessage.Message
if option.IPv4Enable {
msg := new(dnsmessage.Message)
msg.Header.ID = s.addPendingRequest(domain, dnsmessage.TypeA)
msg.Header.RecursionDesired = true
msg.Questions = []dnsmessage.Question{qA}
if opt := s.getMsgOptions(); opt != nil {
msg.Additionals = append(msg.Additionals, *opt)
}
msgs = append(msgs, msg)
}
if option.IPv6Enable {
msg := new(dnsmessage.Message)
msg.Header.ID = s.addPendingRequest(domain, dnsmessage.TypeAAAA)
msg.Header.RecursionDesired = true
msg.Questions = []dnsmessage.Question{qAAAA}
if opt := s.getMsgOptions(); opt != nil {
msg.Additionals = append(msg.Additionals, *opt)
}
msgs = append(msgs, msg)
}
return msgs
}
func (s *ClassicNameServer) sendQuery(ctx context.Context, domain string, option IPOption) {
newError("querying DNS for: ", domain).AtDebug().WriteToLog(session.ExportIDToError(ctx))
msgs := s.buildMsgs(domain, option)
for _, msg := range msgs {
b, _ := dns.PackMessage(msg)
udpCtx := context.Background()
if inbound := session.InboundFromContext(ctx); inbound != nil {
udpCtx = session.ContextWithInbound(udpCtx, inbound)
}
udpCtx = session.ContextWithContent(udpCtx, &session.Content{
Protocol: "dns",
})
s.udpServer.Dispatch(udpCtx, s.address, b)
}
}
func (s *ClassicNameServer) findIPsForDomain(domain string, option IPOption) ([]net.IP, error) {
s.RLock()
record, found := s.ips[domain]
s.RUnlock()
if !found {
return nil, errRecordNotFound
}
var ips []net.Address
var lastErr error
if option.IPv4Enable {
a, err := record.A.getIPs()
if err != nil {
lastErr = err
}
ips = append(ips, a...)
}
if option.IPv6Enable {
aaaa, err := record.AAAA.getIPs()
if err != nil {
lastErr = err
}
ips = append(ips, aaaa...)
}
if len(ips) > 0 {
return toNetIP(ips), nil
}
if lastErr != nil {
return nil, lastErr
}
return nil, dns_feature.ErrEmptyResponse
}
func Fqdn(domain string) string {
if len(domain) > 0 && domain[len(domain)-1] == '.' {
return domain
}
return domain + "."
}
func (s *ClassicNameServer) QueryIP(ctx context.Context, domain string, option IPOption) ([]net.IP, error) {
fqdn := Fqdn(domain)
ips, err := s.findIPsForDomain(fqdn, option)
if err != errRecordNotFound {
return ips, err
}
sub := s.pub.Subscribe(fqdn)
defer sub.Close()
s.sendQuery(ctx, fqdn, option)
for {
ips, err := s.findIPsForDomain(fqdn, option)
if err != errRecordNotFound {
return ips, err
}
select {
case <-ctx.Done():
return nil, ctx.Err()
case <-sub.Wait():
}
}
}
You can’t perform that action at this time.