v1.7.5

Fixes https://github.com/XTLS/Xray-core/issues/1611

.github/workflows/release.yml

@@ -123,7 +123,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v3
         with:
-          go-version: 1.19
+          go-version: '1.20'
           check-latest: true
 
       - name: Get project dependencies

.github/workflows/test.yml

@@ -30,7 +30,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v3
         with:
-          go-version: 1.19
+          go-version: '1.20'
           check-latest: true
       - name: Checkout codebase
         uses: actions/checkout@v3

common/protocol/quic/qtls_go118.go

@@ -1,16 +1,18 @@
 package quic
 
 import (
+	"crypto"
 	"crypto/cipher"
-
-	"github.com/quic-go/qtls-go1-20"
+	_ "crypto/tls"
+	_ "unsafe"
 )
 
-type (
-	// A CipherSuiteTLS13 is a cipher suite for TLS 1.3
-	CipherSuiteTLS13 = qtls.CipherSuiteTLS13
-)
-
-func AEADAESGCMTLS13(key, fixedNonce []byte) cipher.AEAD {
-	return qtls.AEADAESGCMTLS13(key, fixedNonce)
+type CipherSuiteTLS13 struct {
+	ID     uint16
+	KeyLen int
+	AEAD   func(key, fixedNonce []byte) cipher.AEAD
+	Hash   crypto.Hash
 }
+
+//go:linkname AEADAESGCMTLS13 crypto/tls.aeadAESGCMTLS13
+func AEADAESGCMTLS13(key, nonceMask []byte) cipher.AEAD

core/core.go

@@ -18,7 +18,7 @@ import (
 )
 
 var (
-	version  = "1.7.3"
+	version  = "1.7.5"
 	build    = "Custom"
 	codename = "Xray, Penetrates Everything."
 	intro    = "A unified platform for anti-censorship."

go.mod

@@ -11,9 +11,8 @@ require (
 	github.com/miekg/dns v1.1.50
 	github.com/pelletier/go-toml v1.9.5
 	github.com/pires/go-proxyproto v0.6.2
-	github.com/quic-go/qtls-go1-20 v0.1.0
 	github.com/quic-go/quic-go v0.32.0
-	github.com/refraction-networking/utls v1.2.0
+	github.com/refraction-networking/utls v1.2.2-0.20230207151345-a75a4b484849
 	github.com/sagernet/sing v0.1.6
 	github.com/sagernet/sing-shadowsocks v0.1.1-0.20230202035033-e3123545f2f7
 	github.com/sagernet/wireguard-go v0.0.0-20221116151939-c99467f53f2c
@@ -25,8 +24,8 @@ require (
 	golang.org/x/crypto v0.5.0
 	golang.org/x/net v0.5.0
 	golang.org/x/sync v0.1.0
-	golang.org/x/sys v0.4.0
-	google.golang.org/grpc v1.52.3
+	golang.org/x/sys v0.5.0
+	google.golang.org/grpc v1.53.0
 	google.golang.org/protobuf v1.28.1
 	gvisor.dev/gvisor v0.0.0-20220901235040-6ca97ef2ce1c
 	h12.io/socks v1.0.3
@@ -39,21 +38,22 @@ require (
 	github.com/francoispqt/gojay v1.2.13 // indirect
 	github.com/go-task/slim-sprig v0.0.0-20210107165309-348f09dbbbc0 // indirect
 	github.com/google/btree v1.1.2 // indirect
-	github.com/google/pprof v0.0.0-20230131232505-5a9e8f65f08f // indirect
+	github.com/google/pprof v0.0.0-20230207041349-798e818bf904 // indirect
 	github.com/klauspost/compress v1.15.15 // indirect
 	github.com/klauspost/cpuid/v2 v2.2.3 // indirect
 	github.com/onsi/ginkgo/v2 v2.8.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/quic-go/qtls-go1-18 v0.2.0 // indirect
 	github.com/quic-go/qtls-go1-19 v0.2.0 // indirect
+	github.com/quic-go/qtls-go1-20 v0.1.0 // indirect
 	github.com/riobard/go-bloom v0.0.0-20200614022211-cdc8013cb5b3 // indirect
 	go.uber.org/atomic v1.10.0 // indirect
-	golang.org/x/exp v0.0.0-20230131160201-f062dba9d201 // indirect
+	golang.org/x/exp v0.0.0-20230206171751-46f607a40771 // indirect
 	golang.org/x/mod v0.7.0 // indirect
 	golang.org/x/text v0.6.0 // indirect
 	golang.org/x/time v0.3.0 // indirect
 	golang.org/x/tools v0.5.0 // indirect
-	google.golang.org/genproto v0.0.0-20230131230820-1c016267d619 // indirect
+	google.golang.org/genproto v0.0.0-20230202175211-008b39050e57 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	lukechampine.com/blake3 v1.1.7 // indirect

go.sum

@@ -76,8 +76,8 @@ github.com/google/go-github v17.0.0+incompatible/go.mod h1:zLgOLi98H3fifZn+44m+u
 github.com/google/go-querystring v1.0.0/go.mod h1:odCYkC5MyYFN7vkCjXpyrEuKhc/BUO6wN/zVPAxq5ck=
 github.com/google/martian v2.1.0+incompatible/go.mod h1:9I4somxYTbIHy5NJKHRl3wXiIaQGbYVAs8BPL6v8lEs=
 github.com/google/pprof v0.0.0-20181206194817-3ea8567a2e57/go.mod h1:zfwlbNMJ+OItoe0UupaVj+oy1omPYYDuagoSzA8v9mc=
-github.com/google/pprof v0.0.0-20230131232505-5a9e8f65f08f h1:gl1DCiSk+mrXXBGPm6CEeS2MkJuMVzAOrXg34oVj1QI=
-github.com/google/pprof v0.0.0-20230131232505-5a9e8f65f08f/go.mod h1:dDKJzRmX4S37WGHujM7tX//fmj1uioxKzKxz3lo4HJo=
+github.com/google/pprof v0.0.0-20230207041349-798e818bf904 h1:4/hN5RUoecvl+RmJRE2YxKWtnnQls6rQjjW5oV7qg2U=
+github.com/google/pprof v0.0.0-20230207041349-798e818bf904/go.mod h1:uglQLonpP8qtYCYyzA+8c/9qtqgA3qsXGYqCPKARAFg=
 github.com/googleapis/gax-go v2.0.0+incompatible/go.mod h1:SFVmujtThgffbyetf+mdk2eWhX2bMyUtNHzFKcPA9HY=
 github.com/googleapis/gax-go/v2 v2.0.3/go.mod h1:LLvjysVCY1JZeum8Z6l8qUty8fiNwE08qbEPm1M08qg=
 github.com/gopherjs/gopherjs v0.0.0-20181017120253-0766667cb4d1/go.mod h1:wJfORRmW1u3UXTncJ5qlYoELFm8eSnnEO6hX4iZ3EWY=
@@ -138,8 +138,8 @@ github.com/quic-go/qtls-go1-20 v0.1.0 h1:d1PK3ErFy9t7zxKsG3NXBJXZjp/kMLoIb3y/kV5
 github.com/quic-go/qtls-go1-20 v0.1.0/go.mod h1:JKtK6mjbAVcUTN/9jZpvLbGxvdWIKS8uT7EiStoU1SM=
 github.com/quic-go/quic-go v0.32.0 h1:lY02md31s1JgPiiyfqJijpu/UX/Iun304FI3yUqX7tA=
 github.com/quic-go/quic-go v0.32.0/go.mod h1:/fCsKANhQIeD5l76c2JFU+07gVE3KaA0FP+0zMWwfwo=
-github.com/refraction-networking/utls v1.2.0 h1:U5f8wkij2NVinfLuJdFP3gCMwIHs+EzvhxmYdXgiapo=
-github.com/refraction-networking/utls v1.2.0/go.mod h1:NPq+cVqzH7D1BeOkmOcb5O/8iVewAsiVt2x1/eO0hgQ=
+github.com/refraction-networking/utls v1.2.2-0.20230207151345-a75a4b484849 h1:vNEcNapWFwnYJTBcVkHJa8VrdL40PNDLDbSGVY+ZV7I=
+github.com/refraction-networking/utls v1.2.2-0.20230207151345-a75a4b484849/go.mod h1:L1goe44KvhnTfctUffM2isnJpSjPlYShrhXDeZaoYKw=
 github.com/riobard/go-bloom v0.0.0-20200614022211-cdc8013cb5b3 h1:f/FNXud6gA3MNr8meMVVGxhp+QBTqY91tM8HjEuMjGg=
 github.com/riobard/go-bloom v0.0.0-20200614022211-cdc8013cb5b3/go.mod h1:HgjTstvQsPGkxUsCd2KWxErBblirPizecHcpD3ffK+s=
 github.com/russross/blackfriday v1.5.2/go.mod h1:JO/DiYxRf+HjHt06OyowR9PTA263kcR/rfWxYHBV53g=
@@ -208,8 +208,8 @@ golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8U
 golang.org/x/crypto v0.5.0 h1:U/0M97KRkSFvyD/3FSmdP5W5swImpNgle/EHFhOsQPE=
 golang.org/x/crypto v0.5.0/go.mod h1:NK/OQwhpMQP3MwtdjgLlYHnH9ebylxKWv3e0fK+mkQU=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
-golang.org/x/exp v0.0.0-20230131160201-f062dba9d201 h1:BEABXpNXLEz0WxtA+6CQIz2xkg80e+1zrhWyMcq8VzE=
-golang.org/x/exp v0.0.0-20230131160201-f062dba9d201/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=
+golang.org/x/exp v0.0.0-20230206171751-46f607a40771 h1:xP7rWLUr1e1n2xkK5YB4LI0hPEy3LJC6Wk+D4pGlOJg=
+golang.org/x/exp v0.0.0-20230206171751-46f607a40771/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=
 golang.org/x/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
 golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961/go.mod h1:wehouNa3lNwaWXcvxsM5YxQ5yQlVC4a0KAMCusXpPoU=
@@ -259,8 +259,8 @@ golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220704084225-05e143d24a9e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.4.0 h1:Zr2JFtRQNX3BCZ8YtxRE9hNJYC8J6I1MVbMg6owUp18=
-golang.org/x/sys v0.4.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.5.0 h1:MUK/U/4lj1t1oPg0HfuXDN/Z1wv31ZJ/YcPiGccS4DU=
+golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20220526004731-065cf7ba2467/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
@@ -303,16 +303,16 @@ google.golang.org/genproto v0.0.0-20181202183823-bd91e49a0898/go.mod h1:7Ep/1NZk
 google.golang.org/genproto v0.0.0-20190306203927-b5d61aea6440/go.mod h1:VzzqZJRnGkLBvHegQrXjBqPurQTc5/KpmUdxsrq26oE=
 google.golang.org/genproto v0.0.0-20190819201941-24fa4b261c55/go.mod h1:DMBHOl98Agz4BDEuKkezgsaosCRResVns1a3J2ZsMNc=
 google.golang.org/genproto v0.0.0-20200526211855-cb27e3aa2013/go.mod h1:NbSheEEYHJ7i3ixzK3sjbqSGDJWnxyFXZblF3eUsNvo=
-google.golang.org/genproto v0.0.0-20230131230820-1c016267d619 h1:p0kMzw6AG0JEzd7Z+kXqOiLhC6gjUQTbtS2zR0Q3DbI=
-google.golang.org/genproto v0.0.0-20230131230820-1c016267d619/go.mod h1:RGgjbofJ8xD9Sq1VVhDM1Vok1vRONV+rg+CjzG4SZKM=
+google.golang.org/genproto v0.0.0-20230202175211-008b39050e57 h1:vArvWooPH749rNHpBGgVl+U9B9dATjiEhJzcWGlovNs=
+google.golang.org/genproto v0.0.0-20230202175211-008b39050e57/go.mod h1:RGgjbofJ8xD9Sq1VVhDM1Vok1vRONV+rg+CjzG4SZKM=
 google.golang.org/grpc v1.14.0/go.mod h1:yo6s7OP7yaDglbqo1J04qKzAhqBH6lvTonzMVmEdcZw=
 google.golang.org/grpc v1.16.0/go.mod h1:0JHn/cJsOMiMfNA9+DeHDlAU7KAAB5GDlYFpa9MZMio=
 google.golang.org/grpc v1.17.0/go.mod h1:6QZJwpn2B+Zp71q/5VxRsJ6NXXVCE5NRUHRo+f3cWCs=
 google.golang.org/grpc v1.19.0/go.mod h1:mqu4LbDTu4XGKhr4mRzUsmM4RtVoemTSY81AxZiDr8c=
 google.golang.org/grpc v1.23.0/go.mod h1:Y5yQAOtifL1yxbo5wqy6BxZv8vAUGQwXBOALyacEbxg=
 google.golang.org/grpc v1.27.0/go.mod h1:qbnxyOmOxrQa7FizSgH+ReBfzJrCY1pSN7KXBS8abTk=
-google.golang.org/grpc v1.52.3 h1:pf7sOysg4LdgBqduXveGKrcEwbStiK2rtfghdzlUYDQ=
-google.golang.org/grpc v1.52.3/go.mod h1:pu6fVzoFb+NBYNAvQL08ic+lvB2IojljRYuun5vorUY=
+google.golang.org/grpc v1.53.0 h1:LAv2ds7cmFV/XTS3XG1NneeENYrXGmorPxsBbptIjNc=
+google.golang.org/grpc v1.53.0/go.mod h1:OnIrk0ipVdj4N5d9IUoFUx72/VlD7+jUsHwZgwSMQpw=
 google.golang.org/protobuf v0.0.0-20200109180630-ec00e32a8dfd/go.mod h1:DFci5gLYBciE7Vtevhsrf46CRTquxDuWsQurQQe4oz8=
 google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64/go.mod h1:kwYJMbMJ01Woi6D6+Kah6886xMZcty6N08ah7+eCXa0=
 google.golang.org/protobuf v0.0.0-20200228230310-ab0ca4ff8a60/go.mod h1:cfTl7dwQJ+fmap5saPgwCLgHXTUD7jkjRqWcaiX5VyM=

infra/conf/transport_internet.go

@@ -458,6 +458,7 @@ type XTLSConfig struct {
 	MaxVersion                       string            `json:"maxVersion"`
 	CipherSuites                     string            `json:"cipherSuites"`
 	PreferServerCipherSuites         bool              `json:"preferServerCipherSuites"`
+	Fingerprint                      string            `json:"fingerprint"`
 	RejectUnknownSNI                 bool              `json:"rejectUnknownSni"`
 	PinnedPeerCertificateChainSha256 *[]string         `json:"pinnedPeerCertificateChainSha256"`
 }
@@ -487,6 +488,9 @@ func (c *XTLSConfig) Build() (proto.Message, error) {
 	config.MaxVersion = c.MaxVersion
 	config.CipherSuites = c.CipherSuites
 	config.PreferServerCipherSuites = c.PreferServerCipherSuites
+	if c.Fingerprint != "" {
+		return nil, newError(`Old version of XTLS does not support fingerprint. Please use flow "xtls-rprx-vision" with "tls & tlsSettings" instead.`)
+	}
 	config.RejectUnknownSni = c.RejectUnknownSNI
 
 	if c.PinnedPeerCertificateChainSha256 != nil {
@@ -500,6 +504,8 @@ func (c *XTLSConfig) Build() (proto.Message, error) {
 		}
 	}
 
+	newError(`You are using an old version of XTLS, which is deprecated now and will be removed soon. Please use flow "xtls-rprx-vision" with "tls & tlsSettings" instead.`).AtWarning().WriteToLog()
+
 	return config, nil
 }
 

proxy/vless/encoding/encoding.go

@@ -506,25 +506,31 @@ func ReshapeMultiBuffer(ctx context.Context, buffer buf.MultiBuffer) buf.MultiBu
 
 // XtlsPadding add padding to eliminate length siganature during tls handshake
 func XtlsPadding(b *buf.Buffer, command byte, userUUID *[]byte, ctx context.Context) *buf.Buffer {
-	var length int32 = 0
-	if b.Len() < 900 {
+	var contantLen int32 = 0
+	var paddingLen int32 = 0
+	if b != nil {
+		contantLen = b.Len()
+	}
+	if contantLen < 900 {
 		l, err := rand.Int(rand.Reader, big.NewInt(500))
 		if err != nil {
 			newError("failed to generate padding").Base(err).WriteToLog(session.ExportIDToError(ctx))
 		}
-		length = int32(l.Int64()) + 900 - b.Len()
+		paddingLen = int32(l.Int64()) + 900 - contantLen
 	}
 	newbuffer := buf.New()
 	if userUUID != nil {
 		newbuffer.Write(*userUUID)
 		*userUUID = nil
 	}
-	newbuffer.Write([]byte{command, byte(b.Len() >> 8), byte(b.Len()), byte(length >> 8), byte(length)})
-	newbuffer.Write(b.Bytes())
-	newbuffer.Extend(length)
-	newError("XtlsPadding ", b.Len(), " ", length, " ", command).WriteToLog(session.ExportIDToError(ctx))
-	b.Release()
-	b = nil
+	newbuffer.Write([]byte{command, byte(contantLen >> 8), byte(contantLen), byte(paddingLen >> 8), byte(paddingLen)})
+	if (b != nil) {
+		newbuffer.Write(b.Bytes())
+		b.Release()
+		b = nil
+	}
+	newbuffer.Extend(paddingLen)
+	newError("XtlsPadding ", contantLen, " ", paddingLen, " ", command).WriteToLog(session.ExportIDToError(ctx))
 	return newbuffer
 }
 

proxy/vless/outbound/outbound.go

@@ -249,6 +249,13 @@ func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer inte
 				}
 			} else if err1 != buf.ErrReadTimeout {
 				return err1
+			} else if requestAddons.Flow == vless.XRV {
+				mb := make(buf.MultiBuffer, 1)
+				mb[0] = encoding.XtlsPadding(nil, 0x01, &userUUID, ctx) // it must not be tls so padding finish with it (command 1)
+				newError("Insert padding with empty content to camouflage VLESS header ", mb.Len()).WriteToLog(session.ExportIDToError(ctx))
+				if err := serverWriter.WriteMultiBuffer(mb); err != nil {
+					return err
+				}
 			}
 		} else {
 			newError("Reader is not timeout reader, will send out vless header separately from first payload").AtDebug().WriteToLog(session.ExportIDToError(ctx))

transport/internet/tls/tls.go

@@ -12,6 +12,13 @@ import (
 
 //go:generate go run github.com/xtls/xray-core/common/errors/errorgen
 
+type Interface interface {
+	net.Conn
+	Handshake() error
+	VerifyHostname(host string) error
+	NegotiatedProtocol() (name string, mutual bool)
+}
+
 var _ buf.Writer = (*Conn)(nil)
 
 type Conn struct {
@@ -125,6 +132,13 @@ func init() {
 		}
 		i++
 	}
+	weights := utls.DefaultWeights
+	weights.TLSVersMax_Set_VersionTLS13 = 1
+	weights.FirstKeyShare_Set_CurveP256 = 0
+	randomized := utls.HelloRandomized
+	randomized.Seed, _ = utls.NewPRNGSeed()
+	randomized.Weights = &weights
+	PresetFingerprints["randomized"] = &randomized
 }
 
 func GetFingerprint(name string) (fingerprint *utls.ClientHelloID) {
@@ -154,7 +168,7 @@ var PresetFingerprints = map[string]*utls.ClientHelloID{
 	"360":        &utls.Hello360_Auto,
 	"qq":         &utls.HelloQQ_Auto,
 	"random":     nil,
-	"randomized": &utls.HelloRandomized,
+	"randomized": nil,
 }
 
 var ModernFingerprints = map[string]*utls.ClientHelloID{
@@ -203,10 +217,3 @@ var OtherFingerprints = map[string]*utls.ClientHelloID{
 	"helloios_11_1":         &utls.HelloIOS_11_1,
 	"hello360_7_5":          &utls.Hello360_7_5,
 }
-
-type Interface interface {
-	net.Conn
-	Handshake() error
-	VerifyHostname(host string) error
-	NegotiatedProtocol() (name string, mutual bool)
-}

transport/internet/udp/dispatcher.go

@@ -31,6 +31,7 @@ type Dispatcher struct {
 	conns      map[net.Destination]*connEntry
 	dispatcher routing.Dispatcher
 	callback   ResponseCallback
+	callClose  func() error
 }
 
 func NewDispatcher(dispatcher routing.Dispatcher, callback ResponseCallback) *Dispatcher {
@@ -79,7 +80,7 @@ func (v *Dispatcher) getInboundRay(ctx context.Context, dest net.Destination) (*
 		cancel: removeRay,
 	}
 	v.conns[dest] = entry
-	go handleInput(ctx, entry, dest, v.callback)
+	go handleInput(ctx, entry, dest, v.callback, v.callClose)
 	return entry, nil
 }
 
@@ -102,8 +103,13 @@ func (v *Dispatcher) Dispatch(ctx context.Context, destination net.Destination,
 	}
 }
 
-func handleInput(ctx context.Context, conn *connEntry, dest net.Destination, callback ResponseCallback) {
-	defer conn.cancel()
+func handleInput(ctx context.Context, conn *connEntry, dest net.Destination, callback ResponseCallback, callClose func() error) {
+	defer func() {
+		conn.cancel()
+		if callClose != nil {
+			callClose()
+		}
+	}()
 
 	input := conn.link.Reader
 	timer := conn.timer
@@ -144,7 +150,12 @@ func DialDispatcher(ctx context.Context, dispatcher routing.Dispatcher) (net.Pac
 		done:  done.New(),
 	}
 
-	d := NewDispatcher(dispatcher, c.callback)
+	d := &Dispatcher{
+		conns:      make(map[net.Destination]*connEntry),
+		dispatcher: dispatcher,
+		callback:   c.callback,
+		callClose:  c.Close,
+	}
 	c.dispatcher = d
 	return c, nil
 }
@@ -162,16 +173,22 @@ func (c *dispatcherConn) callback(ctx context.Context, packet *udp.Packet) {
 }
 
 func (c *dispatcherConn) ReadFrom(p []byte) (int, net.Addr, error) {
+	var packet *udp.Packet
+s:
 	select {
 	case <-c.done.Wait():
-		return 0, nil, io.EOF
-	case packet := <-c.cache:
-		n := copy(p, packet.Payload.Bytes())
-		return n, &net.UDPAddr{
-			IP:   packet.Source.Address.IP(),
-			Port: int(packet.Source.Port),
-		}, nil
+		select {
+		case packet = <-c.cache:
+			break s
+		default:
+			return 0, nil, io.EOF
+		}
+	case packet = <-c.cache:
 	}
+	return copy(p, packet.Payload.Bytes()), &net.UDPAddr{
+		IP:   packet.Source.Address.IP(),
+		Port: int(packet.Source.Port),
+	}, nil
 }
 
 func (c *dispatcherConn) WriteTo(p []byte, addr net.Addr) (int, error) {