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local_udp.go
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local_udp.go
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package easyss
import (
"errors"
"fmt"
"net"
"strconv"
"strings"
"time"
"github.com/cespare/xxhash/v2"
"github.com/miekg/dns"
"github.com/nange/easyss/v2/cipherstream"
"github.com/nange/easyss/v2/log"
"github.com/nange/easyss/v2/util/bytespool"
"github.com/txthinking/socks5"
)
const (
MaxUDPDataSize = 65507
DefaultDNSServer = "8.8.8.8:53"
)
const DefaultDNSTimeout = 5 * time.Second
// UDPExchange used to store client address and remote connection
type UDPExchange struct {
ClientAddr *net.UDPAddr
RemoteConn net.Conn
}
func (ss *Easyss) UDPHandle(s *socks5.Server, addr *net.UDPAddr, d *socks5.Datagram) error {
log.Debug("[SOCKS5_UDP] enter udp handle", "local_addr", addr.String(), "remote_addr", d.Address())
dst := d.Address()
rewrittenDst := dst
msg := &dns.Msg{}
err := msg.Unpack(d.Data)
isDNSReq := isDNSRequest(msg)
if err == nil && isDNSReq {
question := msg.Question[0]
rule := ss.MatchHostRule(strings.TrimSuffix(question.Name, "."))
if rule == HostRuleBlock {
return responseBlockedDNSMsg(s.UDPConn, addr, msg, d.Address())
}
isDirect := rule == HostRuleDirect
// find from dns cache first
msgCache := ss.DNSCache(question.Name, dns.TypeToString[question.Qtype], isDirect)
if msgCache != nil {
msgCache.MsgHdr.Id = msg.MsgHdr.Id
log.Info("[DNS_CACHE] find from cache", "domain", question.Name, "qtype", dns.TypeToString[question.Qtype])
if err := responseDNSMsg(s.UDPConn, addr, msgCache, d.Address()); err != nil {
log.Error("[DNS_CACHE] write msg back", "err", err)
return err
}
if strings.TrimSuffix(question.Name, ".") != ss.Server() {
log.Debug("[DNS_CACHE] renew cache for", "domain", question.Name)
ss.RenewDNSCache(question.Name, dns.TypeToString[question.Qtype], isDirect)
}
return nil
}
if isDirect {
log.Info("[DNS_DIRECT]", "domain", question.Name, "qtype", dns.TypeToString[question.Qtype])
return ss.directUDPRelay(s, addr, d, true)
}
log.Info("[DNS_PROXY]", "domain", msg.Question[0].Name, "qtype", dns.TypeToString[msg.Question[0].Qtype])
log.Debug("[DNS_PROXY] rewrite dns dst to", "server", DefaultDNSServer)
rewrittenDst = DefaultDNSServer
}
dstHost, port, _ := net.SplitHostPort(rewrittenDst)
if ss.MatchHostRule(dstHost) == HostRuleDirect {
return ss.directUDPRelay(s, addr, d, isDNSReq)
}
if port == "443" && ss.DisableQUIC() { // disable quic proto
log.Info("[UDP_PROXY] quic is disabled", "dst", rewrittenDst)
return errors.New("quic is disabled")
}
if !ss.disableValidateAddr {
if err := ss.validateAddr(rewrittenDst); err != nil {
log.Warn("[UDP_PROXY] validate", "dst", dst, "err", err)
return errors.New("dst addr is invalid")
}
}
var ch chan struct{}
var hasAssoc bool
portStr := strconv.FormatInt(int64(addr.Port), 10)
asCh, ok := s.AssociatedUDP.Get(portStr)
if ok {
hasAssoc = true
ch = asCh.(chan struct{})
log.Debug("[UDP_PROXY] found the associate with tcp", "src", addr.String(), "dst", d.Address())
} else {
ch = make(chan struct{}, 2)
log.Debug("[UDP_PROXY] the addr doesn't associate with tcp", "addr", addr.String(), "dst", d.Address())
}
send := func(ue *UDPExchange, data []byte) error {
select {
case <-ch:
return fmt.Errorf("the tcp that udp address %s associated closed", ue.ClientAddr.String())
default:
}
_, err := ue.RemoteConn.Write(data)
if err != nil {
return err
}
log.Debug("[UDP_PROXY] sent data to remote", "from", ue.ClientAddr.String())
return nil
}
var ue *UDPExchange
var exchKey = addr.String() + dst
ss.lockKey(exchKey)
defer ss.unlockKey(exchKey)
iue, ok := s.UDPExchanges.Get(exchKey)
if ok {
ue = iue.(*UDPExchange)
return send(ue, d.Data)
}
flag := cipherstream.FlagUDP
if isDNSReq {
flag |= cipherstream.FlagDNS
}
csStream, err := ss.handShakeWithRemote(rewrittenDst, flag)
if err != nil {
log.Error("[UDP_PROXY] handshake with remote server", "err", err)
if csStream != nil {
if cs, ok := csStream.(*cipherstream.CipherStream); ok {
cs.MarkConnUnusable()
}
_ = csStream.Close()
}
return err
}
ue = &UDPExchange{
ClientAddr: addr,
RemoteConn: csStream,
}
if err := send(ue, d.Data); err != nil {
if cs, ok := ue.RemoteConn.(*cipherstream.CipherStream); ok {
cs.MarkConnUnusable()
}
_ = ue.RemoteConn.Close()
return err
}
s.UDPExchanges.Set(exchKey, ue, -1)
var monitorCh = make(chan bool)
// monitor the assoc tcp connection to be closed and try to reuse the underlying connection
go func() {
var tryReuse bool
select {
case <-ch:
if err := expireConn(ue.RemoteConn); err != nil {
log.Error("[UDP_PROXY] expire remote conn", "err", err)
}
tryReuse = <-monitorCh
case tryReuse = <-monitorCh:
}
if err := ue.RemoteConn.SetReadDeadline(time.Time{}); err != nil {
tryReuse = false
}
if tryReuse {
log.Debug("[UDP_PROXY] request is finished, try to reuse underlying tcp connection")
reuse := tryReuseInUDPClient(ue.RemoteConn, ss.Timeout())
if reuse != nil {
if cs, ok := ue.RemoteConn.(*cipherstream.CipherStream); ok {
cs.MarkConnUnusable()
}
log.Warn("[UDP_PROXY] underlying proxy connection is unhealthy, need close it", "reuse", reuse)
} else {
log.Debug("[UDP_PROXY] underlying proxy connection is healthy, so reuse it")
}
} else {
if cs, ok := ue.RemoteConn.(*cipherstream.CipherStream); ok {
cs.MarkConnUnusable()
}
}
_ = ue.RemoteConn.Close()
}()
go func(ue *UDPExchange, dst string) {
var tryReuse = true
if !ss.IsNativeOutboundProto() {
tryReuse = false
}
defer func() {
ss.lockKey(exchKey)
defer ss.unlockKey(exchKey)
monitorCh <- tryReuse
ch <- struct{}{}
s.UDPExchanges.Delete(exchKey)
}()
var buf = bytespool.Get(MaxUDPDataSize)
defer bytespool.MustPut(buf)
for {
select {
case <-ch:
log.Info("[UDP_PROXY] the tcp that udp address associated closed", "udp_addr", ue.ClientAddr.String())
return
default:
}
if !hasAssoc {
var err error
if isDNSReq {
err = ue.RemoteConn.SetReadDeadline(time.Now().Add(DefaultDNSTimeout))
} else {
err = ue.RemoteConn.SetReadDeadline(time.Now().Add(ss.Timeout()))
}
if err != nil {
log.Error("[UDP_PROXY] set the deadline for remote conn err", "err", err)
tryReuse = false
return
}
}
n, err := ue.RemoteConn.Read(buf[:])
if err != nil {
if !errors.Is(err, cipherstream.ErrTimeout) {
tryReuse = false
log.Debug("[UDP_PROXY] remote conn read", "err", err)
}
return
}
log.Debug("[UDP_PROXY] got data from remote", "client", ue.ClientAddr.String(), "data_len", len(buf[0:n]))
// if is dns response, set result to dns cache
_msg := ss.SetDNSCacheIfNeeded(buf[0:n], false)
a, addr, port, err := socks5.ParseAddress(dst)
if err != nil {
log.Error("[UDP_PROXY] parse dst address", "err", err)
return
}
data := buf[0:n]
if _msg != nil {
data, _ = _msg.Pack()
}
d1 := socks5.NewDatagram(a, addr, port, data)
if _, err := s.UDPConn.WriteToUDP(d1.Bytes(), ue.ClientAddr); err != nil {
return
}
}
}(ue, dst)
return nil
}
func (ss *Easyss) lockKey(key string) {
hashVal := xxhash.Sum64String(key)
lockID := hashVal & UDPLocksAndOpVal
ss.udpLocks[lockID].Lock()
}
func (ss *Easyss) unlockKey(key string) {
hashVal := xxhash.Sum64String(key)
lockID := hashVal & UDPLocksAndOpVal
ss.udpLocks[lockID].Unlock()
}
func (ss *Easyss) SetDNSCacheIfNeeded(udpResp []byte, isDirect bool) *dns.Msg {
logPrefix := "[DNS_PROXY]"
if isDirect {
logPrefix = "[DNS_DIRECT]"
}
msg := &dns.Msg{}
if err := msg.Unpack(udpResp); err == nil && isDNSResponse(msg) {
log.Info(logPrefix+" got result for",
"domain", msg.Question[0].Name, "answer", msg.Answer, "qtype", dns.TypeToString[msg.Question[0].Qtype])
if ss.ShouldIPV6Disable() && msg.Question[0].Qtype == dns.TypeAAAA {
log.Info(logPrefix+" ipv6 is disabled, set TypeAAAA dns answer to nil for", "domain", msg.Question[0].Name)
msg.Answer = nil
}
if err := ss.SetDNSCache(msg, false, isDirect); err != nil {
log.Warn(logPrefix+" set dns cache", logPrefix, "err", err)
} else {
log.Debug(logPrefix+" set cache for", "domain", msg.Question[0].Name, "qtype", dns.TypeToString[msg.Question[0].Qtype])
}
return msg
}
return nil
}
func responseDNSMsg(conn *net.UDPConn, localAddr *net.UDPAddr, msg *dns.Msg, remoteAddr string) error {
a, _addr, port, _ := socks5.ParseAddress(remoteAddr)
pack, _ := msg.Pack()
d1 := socks5.NewDatagram(a, _addr, port, pack)
_, err := conn.WriteToUDP(d1.Bytes(), localAddr)
return err
}
func responseBlockedDNSMsg(conn *net.UDPConn, localAddr *net.UDPAddr, request *dns.Msg, remoteAddr string) error {
question := request.Question[0]
log.Info("[DNS_BLOCK]", "domain", question.Name)
m := new(dns.Msg)
m.SetReply(request)
if question.Qtype == dns.TypeA {
rr, err := dns.NewRR(fmt.Sprintf("%s A 127.0.0.1", question.Name))
if err != nil {
log.Error("[DNS_BLOCK] creating A record:", "err", err)
return err
}
m.Answer = append(m.Answer, rr)
} else if question.Qtype == dns.TypeAAAA {
rr, err := dns.NewRR(fmt.Sprintf("%s AAAA ::1", question.Name))
if err != nil {
log.Error("[DNS_BLOCK] creating AAAA record:", "err", err)
return err
}
m.Answer = append(m.Answer, rr)
}
if err := responseDNSMsg(conn, localAddr, m, remoteAddr); err != nil {
log.Error("[DNS_BLOCK] response", "err", err)
return err
}
return nil
}
func expireConn(conn net.Conn) error {
return conn.SetReadDeadline(time.Unix(0, 0))
}
func isDNSRequest(msg *dns.Msg) bool {
if msg == nil || len(msg.Question) == 0 {
return false
}
q := msg.Question[0]
if q.Qtype == dns.TypeA || q.Qtype == dns.TypeAAAA {
return true
}
return false
}
func isDNSResponse(msg *dns.Msg) bool {
if msg == nil {
return false
}
if !msg.MsgHdr.Response || !isDNSRequest(msg) {
return false
}
return true
}
func tryReuseInUDPClient(cipher net.Conn, timeout time.Duration) error {
if err := cipher.SetReadDeadline(time.Now().Add(timeout)); err != nil {
return err
}
if err := CloseWrite(cipher); err != nil {
return err
}
if err := ReadACKFromCipher(cipher); err != nil {
return err
}
if err := readFINFromCipher(cipher); err != nil {
return err
}
if err := WriteACKToCipher(cipher); err != nil {
return err
}
if err := cipher.SetReadDeadline(time.Time{}); err != nil {
return err
}
return nil
}
func readFINFromCipher(conn net.Conn) error {
buf := bytespool.Get(RelayBufferSize)
defer bytespool.MustPut(buf)
var err error
for {
_, err = conn.Read(buf)
if err != nil {
break
}
}
if errors.Is(err, cipherstream.ErrFINRSTStream) {
return nil
}
return err
}