From 017f53b5fcf51d19a277514b8df1e167f39e972b Mon Sep 17 00:00:00 2001
From: yuhan6665 <1588741+yuhan6665@users.noreply.github.com>
Date: Mon, 13 May 2024 21:52:24 -0400
Subject: [PATCH] Add session context outbounds as slice (#3356)

* Add session context outbounds as slice

slice is needed for dialer proxy where two outbounds work on top of each other
There are two sets of target addr for example
It also enable Xtls to correctly do splice copy by checking both outbounds are ready to do direct copy

* Fill outbound tag info

* Splice now checks capalibility from all outbounds

* Fix unit tests
---
 app/dispatcher/default.go               |  22 ++---
 app/dispatcher/fakednssniffer.go        |  11 +--
 app/proxyman/inbound/worker.go          |  11 +--
 app/proxyman/outbound/handler.go        |  38 +++++----
 app/proxyman/outbound/handler_test.go   |   3 +
 app/reverse/portal.go                   |  12 +--
 app/router/router_test.go               |  20 +++--
 common/mux/client.go                    |  14 ++--
 common/mux/client_test.go               |   8 +-
 common/session/context.go               |  10 +--
 common/session/session.go               |  14 ++--
 common/singbridge/dialer.go             |  11 ++-
 features/routing/session/context.go     |   4 +-
 proxy/blackhole/blackhole.go            |   7 +-
 proxy/blackhole/blackhole_test.go       |   6 +-
 proxy/dns/dns.go                        |  11 +--
 proxy/dokodemo/dokodemo.go              |  15 ++--
 proxy/freedom/freedom.go                |  14 ++--
 proxy/http/client.go                    |  21 +++--
 proxy/http/server.go                    |   2 +-
 proxy/loopback/loopback.go              |   9 ++-
 proxy/proxy.go                          | 102 +++++++++++++++---------
 proxy/shadowsocks/client.go             |  14 ++--
 proxy/shadowsocks/server.go             |   2 +-
 proxy/shadowsocks_2022/inbound.go       |   2 +-
 proxy/shadowsocks_2022/inbound_multi.go |   2 +-
 proxy/shadowsocks_2022/inbound_relay.go |   2 +-
 proxy/shadowsocks_2022/outbound.go      |  11 +--
 proxy/socks/client.go                   |  14 ++--
 proxy/socks/server.go                   |   2 +-
 proxy/trojan/client.go                  |  14 ++--
 proxy/trojan/server.go                  |   2 +-
 proxy/vless/encoding/encoding.go        |  20 +++--
 proxy/vless/inbound/inbound.go          |  10 ++-
 proxy/vless/outbound/outbound.go        |  24 +++---
 proxy/vmess/inbound/inbound.go          |   2 +-
 proxy/vmess/outbound/outbound.go        |  14 ++--
 proxy/wireguard/client.go               |  14 ++--
 proxy/wireguard/server.go               |   8 +-
 transport/internet/dialer.go            |  13 ++-
 transport/internet/grpc/dial.go         |   2 +-
 transport/internet/http/dialer.go       |   2 +-
 42 files changed, 303 insertions(+), 236 deletions(-)

diff --git a/app/dispatcher/default.go b/app/dispatcher/default.go
index b8131b8f8..26019bbe9 100644
--- a/app/dispatcher/default.go
+++ b/app/dispatcher/default.go
@@ -218,11 +218,12 @@ func (d *DefaultDispatcher) Dispatch(ctx context.Context, destination net.Destin
 	if !destination.IsValid() {
 		panic("Dispatcher: Invalid destination.")
 	}
-	ob := session.OutboundFromContext(ctx)
-	if ob == nil {
-		ob = &session.Outbound{}
-		ctx = session.ContextWithOutbound(ctx, ob)
+	outbounds := session.OutboundsFromContext(ctx)
+	if len(outbounds) == 0 {
+		outbounds = []*session.Outbound{{}}
+		ctx = session.ContextWithOutbounds(ctx, outbounds)
 	}
+	ob := outbounds[len(outbounds) - 1]
 	ob.OriginalTarget = destination
 	ob.Target = destination
 	content := session.ContentFromContext(ctx)
@@ -274,11 +275,12 @@ func (d *DefaultDispatcher) DispatchLink(ctx context.Context, destination net.De
 	if !destination.IsValid() {
 		return newError("Dispatcher: Invalid destination.")
 	}
-	ob := session.OutboundFromContext(ctx)
-	if ob == nil {
-		ob = &session.Outbound{}
-		ctx = session.ContextWithOutbound(ctx, ob)
+	outbounds := session.OutboundsFromContext(ctx)
+	if len(outbounds) == 0 {
+		outbounds = []*session.Outbound{{}}
+		ctx = session.ContextWithOutbounds(ctx, outbounds)
 	}
+	ob := outbounds[len(outbounds) - 1]
 	ob.OriginalTarget = destination
 	ob.Target = destination
 	content := session.ContentFromContext(ctx)
@@ -368,7 +370,8 @@ func sniffer(ctx context.Context, cReader *cachedReader, metadataOnly bool, netw
 	return contentResult, contentErr
 }
 func (d *DefaultDispatcher) routedDispatch(ctx context.Context, link *transport.Link, destination net.Destination) {
-	ob := session.OutboundFromContext(ctx)
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
 	if hosts, ok := d.dns.(dns.HostsLookup); ok && destination.Address.Family().IsDomain() {
 		proxied := hosts.LookupHosts(ob.Target.String())
 		if proxied != nil {
@@ -425,6 +428,7 @@ func (d *DefaultDispatcher) routedDispatch(ctx context.Context, link *transport.
 		return
 	}
 
+	ob.Tag = handler.Tag()
 	if accessMessage := log.AccessMessageFromContext(ctx); accessMessage != nil {
 		if tag := handler.Tag(); tag != "" {
 			if inTag == "" {
diff --git a/app/dispatcher/fakednssniffer.go b/app/dispatcher/fakednssniffer.go
index ad879daf5..8d0804de1 100644
--- a/app/dispatcher/fakednssniffer.go
+++ b/app/dispatcher/fakednssniffer.go
@@ -26,11 +26,12 @@ func newFakeDNSSniffer(ctx context.Context) (protocolSnifferWithMetadata, error)
 		return protocolSnifferWithMetadata{}, errNotInit
 	}
 	return protocolSnifferWithMetadata{protocolSniffer: func(ctx context.Context, bytes []byte) (SniffResult, error) {
-		Target := session.OutboundFromContext(ctx).Target
-		if Target.Network == net.Network_TCP || Target.Network == net.Network_UDP {
-			domainFromFakeDNS := fakeDNSEngine.GetDomainFromFakeDNS(Target.Address)
+		outbounds := session.OutboundsFromContext(ctx)
+		ob := outbounds[len(outbounds) - 1]
+		if ob.Target.Network == net.Network_TCP || ob.Target.Network == net.Network_UDP {
+			domainFromFakeDNS := fakeDNSEngine.GetDomainFromFakeDNS(ob.Target.Address)
 			if domainFromFakeDNS != "" {
-				newError("fake dns got domain: ", domainFromFakeDNS, " for ip: ", Target.Address.String()).WriteToLog(session.ExportIDToError(ctx))
+				newError("fake dns got domain: ", domainFromFakeDNS, " for ip: ", ob.Target.Address.String()).WriteToLog(session.ExportIDToError(ctx))
 				return &fakeDNSSniffResult{domainName: domainFromFakeDNS}, nil
 			}
 		}
@@ -38,7 +39,7 @@ func newFakeDNSSniffer(ctx context.Context) (protocolSnifferWithMetadata, error)
 		if ipAddressInRangeValueI := ctx.Value(ipAddressInRange); ipAddressInRangeValueI != nil {
 			ipAddressInRangeValue := ipAddressInRangeValueI.(*ipAddressInRangeOpt)
 			if fkr0, ok := fakeDNSEngine.(dns.FakeDNSEngineRev0); ok {
-				inPool := fkr0.IsIPInIPPool(Target.Address)
+				inPool := fkr0.IsIPInIPPool(ob.Target.Address)
 				ipAddressInRangeValue.addressInRange = &inPool
 			}
 		}
diff --git a/app/proxyman/inbound/worker.go b/app/proxyman/inbound/worker.go
index 1fe866552..9a6499f12 100644
--- a/app/proxyman/inbound/worker.go
+++ b/app/proxyman/inbound/worker.go
@@ -60,7 +60,7 @@ func (w *tcpWorker) callback(conn stat.Connection) {
 	sid := session.NewID()
 	ctx = session.ContextWithID(ctx, sid)
 
-	var outbound = &session.Outbound{}
+	outbounds := []*session.Outbound{{}}
 	if w.recvOrigDest {
 		var dest net.Destination
 		switch getTProxyType(w.stream) {
@@ -75,10 +75,10 @@ func (w *tcpWorker) callback(conn stat.Connection) {
 			dest = net.DestinationFromAddr(conn.LocalAddr())
 		}
 		if dest.IsValid() {
-			outbound.Target = dest
+			outbounds[0].Target = dest
 		}
 	}
-	ctx = session.ContextWithOutbound(ctx, outbound)
+	ctx = session.ContextWithOutbounds(ctx, outbounds)
 
 	if w.uplinkCounter != nil || w.downlinkCounter != nil {
 		conn = &stat.CounterConnection{
@@ -309,9 +309,10 @@ func (w *udpWorker) callback(b *buf.Buffer, source net.Destination, originalDest
 			ctx = session.ContextWithID(ctx, sid)
 
 			if originalDest.IsValid() {
-				ctx = session.ContextWithOutbound(ctx, &session.Outbound{
+				outbounds := []*session.Outbound{{
 					Target: originalDest,
-				})
+				}}
+				ctx = session.ContextWithOutbounds(ctx, outbounds)
 			}
 			ctx = session.ContextWithInbound(ctx, &session.Inbound{
 				Source:  source,
diff --git a/app/proxyman/outbound/handler.go b/app/proxyman/outbound/handler.go
index 792ac2497..4262c76a5 100644
--- a/app/proxyman/outbound/handler.go
+++ b/app/proxyman/outbound/handler.go
@@ -169,10 +169,11 @@ func (h *Handler) Tag() string {
 
 // Dispatch implements proxy.Outbound.Dispatch.
 func (h *Handler) Dispatch(ctx context.Context, link *transport.Link) {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound.Target.Network == net.Network_UDP && outbound.OriginalTarget.Address != nil && outbound.OriginalTarget.Address != outbound.Target.Address {
-		link.Reader = &buf.EndpointOverrideReader{Reader: link.Reader, Dest: outbound.Target.Address, OriginalDest: outbound.OriginalTarget.Address}
-		link.Writer = &buf.EndpointOverrideWriter{Writer: link.Writer, Dest: outbound.Target.Address, OriginalDest: outbound.OriginalTarget.Address}
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if ob.Target.Network == net.Network_UDP && ob.OriginalTarget.Address != nil && ob.OriginalTarget.Address != ob.Target.Address {
+		link.Reader = &buf.EndpointOverrideReader{Reader: link.Reader, Dest: ob.Target.Address, OriginalDest: ob.OriginalTarget.Address}
+		link.Writer = &buf.EndpointOverrideWriter{Writer: link.Writer, Dest: ob.Target.Address, OriginalDest: ob.OriginalTarget.Address}
 	}
 	if h.mux != nil {
 		test := func(err error) {
@@ -183,7 +184,7 @@ func (h *Handler) Dispatch(ctx context.Context, link *transport.Link) {
 				common.Interrupt(link.Writer)
 			}
 		}
-		if outbound.Target.Network == net.Network_UDP && outbound.Target.Port == 443 {
+		if ob.Target.Network == net.Network_UDP && ob.Target.Port == 443 {
 			switch h.udp443 {
 			case "reject":
 				test(newError("XUDP rejected UDP/443 traffic").AtInfo())
@@ -192,7 +193,7 @@ func (h *Handler) Dispatch(ctx context.Context, link *transport.Link) {
 				goto out
 			}
 		}
-		if h.xudp != nil && outbound.Target.Network == net.Network_UDP {
+		if h.xudp != nil && ob.Target.Network == net.Network_UDP {
 			if !h.xudp.Enabled {
 				goto out
 			}
@@ -243,10 +244,11 @@ func (h *Handler) Dial(ctx context.Context, dest net.Destination) (stat.Connecti
 			handler := h.outboundManager.GetHandler(tag)
 			if handler != nil {
 				newError("proxying to ", tag, " for dest ", dest).AtDebug().WriteToLog(session.ExportIDToError(ctx))
-				ctx = session.ContextWithOutbound(ctx, &session.Outbound{
+				outbounds := session.OutboundsFromContext(ctx)
+				ctx = session.ContextWithOutbounds(ctx, append(outbounds, &session.Outbound{
 					Target: dest,
-				})
-
+					Tag: tag,
+				})) // add another outbound in session ctx
 				opts := pipe.OptionsFromContext(ctx)
 				uplinkReader, uplinkWriter := pipe.New(opts...)
 				downlinkReader, downlinkWriter := pipe.New(opts...)
@@ -266,15 +268,12 @@ func (h *Handler) Dial(ctx context.Context, dest net.Destination) (stat.Connecti
 		}
 
 		if h.senderSettings.Via != nil {
-			outbound := session.OutboundFromContext(ctx)
-			if outbound == nil {
-				outbound = new(session.Outbound)
-				ctx = session.ContextWithOutbound(ctx, outbound)
-			}
+			outbounds := session.OutboundsFromContext(ctx)
+			ob := outbounds[len(outbounds) - 1]
 			if h.senderSettings.ViaCidr == "" {
-				outbound.Gateway = h.senderSettings.Via.AsAddress()
+				ob.Gateway = h.senderSettings.Via.AsAddress()
 			} else { //Get a random address.
-				outbound.Gateway = ParseRandomIPv6(h.senderSettings.Via.AsAddress(), h.senderSettings.ViaCidr)
+				ob.Gateway = ParseRandomIPv6(h.senderSettings.Via.AsAddress(), h.senderSettings.ViaCidr)
 			}
 		}
 	}
@@ -285,10 +284,9 @@ func (h *Handler) Dial(ctx context.Context, dest net.Destination) (stat.Connecti
 
 	conn, err := internet.Dial(ctx, dest, h.streamSettings)
 	conn = h.getStatCouterConnection(conn)
-	outbound := session.OutboundFromContext(ctx)
-	if outbound != nil {
-		outbound.Conn = conn
-	}
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	ob.Conn = conn
 	return conn, err
 }
 
diff --git a/app/proxyman/outbound/handler_test.go b/app/proxyman/outbound/handler_test.go
index e5b67308c..3f7ef28e0 100644
--- a/app/proxyman/outbound/handler_test.go
+++ b/app/proxyman/outbound/handler_test.go
@@ -14,6 +14,7 @@ import (
 	"github.com/xtls/xray-core/app/stats"
 	"github.com/xtls/xray-core/common/net"
 	"github.com/xtls/xray-core/common/serial"
+	"github.com/xtls/xray-core/common/session"
 	core "github.com/xtls/xray-core/core"
 	"github.com/xtls/xray-core/features/outbound"
 	"github.com/xtls/xray-core/proxy/freedom"
@@ -44,6 +45,7 @@ func TestOutboundWithoutStatCounter(t *testing.T) {
 	v, _ := core.New(config)
 	v.AddFeature((outbound.Manager)(new(Manager)))
 	ctx := context.WithValue(context.Background(), xrayKey, v)
+	ctx = session.ContextWithOutbounds(ctx, []*session.Outbound{{}})
 	h, _ := NewHandler(ctx, &core.OutboundHandlerConfig{
 		Tag:           "tag",
 		ProxySettings: serial.ToTypedMessage(&freedom.Config{}),
@@ -73,6 +75,7 @@ func TestOutboundWithStatCounter(t *testing.T) {
 	v, _ := core.New(config)
 	v.AddFeature((outbound.Manager)(new(Manager)))
 	ctx := context.WithValue(context.Background(), xrayKey, v)
+	ctx = session.ContextWithOutbounds(ctx, []*session.Outbound{{}})
 	h, _ := NewHandler(ctx, &core.OutboundHandlerConfig{
 		Tag:           "tag",
 		ProxySettings: serial.ToTypedMessage(&freedom.Config{}),
diff --git a/app/reverse/portal.go b/app/reverse/portal.go
index fb0b69300..456de550d 100644
--- a/app/reverse/portal.go
+++ b/app/reverse/portal.go
@@ -62,12 +62,13 @@ func (p *Portal) Close() error {
 }
 
 func (p *Portal) HandleConnection(ctx context.Context, link *transport.Link) error {
-	outboundMeta := session.OutboundFromContext(ctx)
-	if outboundMeta == nil {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if ob == nil {
 		return newError("outbound metadata not found").AtError()
 	}
 
-	if isDomain(outboundMeta.Target, p.domain) {
+	if isDomain(ob.Target, p.domain) {
 		muxClient, err := mux.NewClientWorker(*link, mux.ClientStrategy{})
 		if err != nil {
 			return newError("failed to create mux client worker").Base(err).AtWarning()
@@ -206,9 +207,10 @@ func NewPortalWorker(client *mux.ClientWorker) (*PortalWorker, error) {
 	downlinkReader, downlinkWriter := pipe.New(opt...)
 
 	ctx := context.Background()
-	ctx = session.ContextWithOutbound(ctx, &session.Outbound{
+	outbounds := []*session.Outbound{{
 		Target: net.UDPDestination(net.DomainAddress(internalDomain), 0),
-	})
+	}}
+	ctx = session.ContextWithOutbounds(ctx, outbounds)
 	f := client.Dispatch(ctx, &transport.Link{
 		Reader: uplinkReader,
 		Writer: downlinkWriter,
diff --git a/app/router/router_test.go b/app/router/router_test.go
index 4c6bfc63f..2c33aae1c 100644
--- a/app/router/router_test.go
+++ b/app/router/router_test.go
@@ -45,7 +45,9 @@ func TestSimpleRouter(t *testing.T) {
 		HandlerSelector: mockHs,
 	}, nil))
 
-	ctx := session.ContextWithOutbound(context.Background(), &session.Outbound{Target: net.TCPDestination(net.DomainAddress("example.com"), 80)})
+	ctx := session.ContextWithOutbounds(context.Background(), []*session.Outbound{{
+		Target: net.TCPDestination(net.DomainAddress("example.com"), 80),
+	}})
 	route, err := r.PickRoute(routing_session.AsRoutingContext(ctx))
 	common.Must(err)
 	if tag := route.GetOutboundTag(); tag != "test" {
@@ -86,7 +88,9 @@ func TestSimpleBalancer(t *testing.T) {
 		HandlerSelector: mockHs,
 	}, nil))
 
-	ctx := session.ContextWithOutbound(context.Background(), &session.Outbound{Target: net.TCPDestination(net.DomainAddress("example.com"), 80)})
+	ctx := session.ContextWithOutbounds(context.Background(), []*session.Outbound{{
+		Target: net.TCPDestination(net.DomainAddress("example.com"), 80),
+	}})
 	route, err := r.PickRoute(routing_session.AsRoutingContext(ctx))
 	common.Must(err)
 	if tag := route.GetOutboundTag(); tag != "test" {
@@ -174,7 +178,9 @@ func TestIPOnDemand(t *testing.T) {
 	r := new(Router)
 	common.Must(r.Init(context.TODO(), config, mockDNS, nil, nil))
 
-	ctx := session.ContextWithOutbound(context.Background(), &session.Outbound{Target: net.TCPDestination(net.DomainAddress("example.com"), 80)})
+	ctx := session.ContextWithOutbounds(context.Background(), []*session.Outbound{{
+		Target: net.TCPDestination(net.DomainAddress("example.com"), 80),
+	}})
 	route, err := r.PickRoute(routing_session.AsRoutingContext(ctx))
 	common.Must(err)
 	if tag := route.GetOutboundTag(); tag != "test" {
@@ -213,7 +219,9 @@ func TestIPIfNonMatchDomain(t *testing.T) {
 	r := new(Router)
 	common.Must(r.Init(context.TODO(), config, mockDNS, nil, nil))
 
-	ctx := session.ContextWithOutbound(context.Background(), &session.Outbound{Target: net.TCPDestination(net.DomainAddress("example.com"), 80)})
+	ctx := session.ContextWithOutbounds(context.Background(), []*session.Outbound{{
+		Target: net.TCPDestination(net.DomainAddress("example.com"), 80),
+	}})
 	route, err := r.PickRoute(routing_session.AsRoutingContext(ctx))
 	common.Must(err)
 	if tag := route.GetOutboundTag(); tag != "test" {
@@ -247,7 +255,9 @@ func TestIPIfNonMatchIP(t *testing.T) {
 	r := new(Router)
 	common.Must(r.Init(context.TODO(), config, mockDNS, nil, nil))
 
-	ctx := session.ContextWithOutbound(context.Background(), &session.Outbound{Target: net.TCPDestination(net.LocalHostIP, 80)})
+	ctx := session.ContextWithOutbounds(context.Background(), []*session.Outbound{{
+		Target: net.TCPDestination(net.LocalHostIP, 80),
+	}})
 	route, err := r.PickRoute(routing_session.AsRoutingContext(ctx))
 	common.Must(err)
 	if tag := route.GetOutboundTag(); tag != "test" {
diff --git a/common/mux/client.go b/common/mux/client.go
index 88621be0f..2537f02b6 100644
--- a/common/mux/client.go
+++ b/common/mux/client.go
@@ -148,9 +148,10 @@ func (f *DialingWorkerFactory) Create() (*ClientWorker, error) {
 	}
 
 	go func(p proxy.Outbound, d internet.Dialer, c common.Closable) {
-		ctx := session.ContextWithOutbound(context.Background(), &session.Outbound{
+		outbounds := []*session.Outbound{{
 			Target: net.TCPDestination(muxCoolAddress, muxCoolPort),
-		})
+		}}
+		ctx := session.ContextWithOutbounds(context.Background(), outbounds)
 		ctx, cancel := context.WithCancel(ctx)
 
 		if err := p.Process(ctx, &transport.Link{Reader: uplinkReader, Writer: downlinkWriter}, d); err != nil {
@@ -242,17 +243,18 @@ func writeFirstPayload(reader buf.Reader, writer *Writer) error {
 }
 
 func fetchInput(ctx context.Context, s *Session, output buf.Writer) {
-	dest := session.OutboundFromContext(ctx).Target
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
 	transferType := protocol.TransferTypeStream
-	if dest.Network == net.Network_UDP {
+	if ob.Target.Network == net.Network_UDP {
 		transferType = protocol.TransferTypePacket
 	}
 	s.transferType = transferType
-	writer := NewWriter(s.ID, dest, output, transferType, xudp.GetGlobalID(ctx))
+	writer := NewWriter(s.ID, ob.Target, output, transferType, xudp.GetGlobalID(ctx))
 	defer s.Close(false)
 	defer writer.Close()
 
-	newError("dispatching request to ", dest).WriteToLog(session.ExportIDToError(ctx))
+	newError("dispatching request to ", ob.Target).WriteToLog(session.ExportIDToError(ctx))
 	if err := writeFirstPayload(s.input, writer); err != nil {
 		newError("failed to write first payload").Base(err).WriteToLog(session.ExportIDToError(ctx))
 		writer.hasError = true
diff --git a/common/mux/client_test.go b/common/mux/client_test.go
index 7837a86e7..9626e2a27 100644
--- a/common/mux/client_test.go
+++ b/common/mux/client_test.go
@@ -86,9 +86,9 @@ func TestClientWorkerClose(t *testing.T) {
 	}
 
 	tr1, tw1 := pipe.New(pipe.WithoutSizeLimit())
-	ctx1 := session.ContextWithOutbound(context.Background(), &session.Outbound{
+	ctx1 := session.ContextWithOutbounds(context.Background(), []*session.Outbound{{
 		Target: net.TCPDestination(net.DomainAddress("www.example.com"), 80),
-	})
+	}})
 	common.Must(manager.Dispatch(ctx1, &transport.Link{
 		Reader: tr1,
 		Writer: tw1,
@@ -103,9 +103,9 @@ func TestClientWorkerClose(t *testing.T) {
 	}
 
 	tr2, tw2 := pipe.New(pipe.WithoutSizeLimit())
-	ctx2 := session.ContextWithOutbound(context.Background(), &session.Outbound{
+	ctx2 := session.ContextWithOutbounds(context.Background(), []*session.Outbound{{
 		Target: net.TCPDestination(net.DomainAddress("www.example.com"), 80),
-	})
+	}})
 	common.Must(manager.Dispatch(ctx2, &transport.Link{
 		Reader: tr2,
 		Writer: tw2,
diff --git a/common/session/context.go b/common/session/context.go
index 87586169e..fc37bd72e 100644
--- a/common/session/context.go
+++ b/common/session/context.go
@@ -51,13 +51,13 @@ func InboundFromContext(ctx context.Context) *Inbound {
 	return nil
 }
 
-func ContextWithOutbound(ctx context.Context, outbound *Outbound) context.Context {
-	return context.WithValue(ctx, outboundSessionKey, outbound)
+func ContextWithOutbounds(ctx context.Context, outbounds []*Outbound) context.Context {
+	return context.WithValue(ctx, outboundSessionKey, outbounds)
 }
 
-func OutboundFromContext(ctx context.Context) *Outbound {
-	if outbound, ok := ctx.Value(outboundSessionKey).(*Outbound); ok {
-		return outbound
+func OutboundsFromContext(ctx context.Context) []*Outbound {
+	if outbounds, ok := ctx.Value(outboundSessionKey).([]*Outbound); ok {
+		return outbounds
 	}
 	return nil
 }
diff --git a/common/session/session.go b/common/session/session.go
index 38ffa7bda..d8ab1ec42 100644
--- a/common/session/session.go
+++ b/common/session/session.go
@@ -50,18 +50,11 @@ type Inbound struct {
 	Conn net.Conn
 	// Timer of the inbound buf copier. May be nil.
 	Timer *signal.ActivityTimer
-	// CanSpliceCopy is a property for this connection, set by both inbound and outbound
+	// CanSpliceCopy is a property for this connection
 	// 1 = can, 2 = after processing protocol info should be able to, 3 = cannot
 	CanSpliceCopy int
 }
 
-func(i *Inbound) SetCanSpliceCopy(canSpliceCopy int) int {
-	if canSpliceCopy > i.CanSpliceCopy {
-		i.CanSpliceCopy = canSpliceCopy
-	}
-	return i.CanSpliceCopy
-}
-
 // Outbound is the metadata of an outbound connection.
 type Outbound struct {
 	// Target address of the outbound connection.
@@ -70,10 +63,15 @@ type Outbound struct {
 	RouteTarget    net.Destination
 	// Gateway address
 	Gateway net.Address
+	// Tag of the outbound proxy that handles the connection.
+	Tag string
 	// Name of the outbound proxy that handles the connection.
 	Name string
 	// Conn is actually internet.Connection. May be nil. It is currently nil for outbound with proxySettings 
 	Conn net.Conn
+	// CanSpliceCopy is a property for this connection
+	// 1 = can, 2 = after processing protocol info should be able to, 3 = cannot
+	CanSpliceCopy int
 }
 
 // SniffingRequest controls the behavior of content sniffing.
diff --git a/common/singbridge/dialer.go b/common/singbridge/dialer.go
index 896c97fee..6be83036e 100644
--- a/common/singbridge/dialer.go
+++ b/common/singbridge/dialer.go
@@ -43,9 +43,14 @@ func NewOutboundDialer(outbound proxy.Outbound, dialer internet.Dialer) *XrayOut
 }
 
 func (d *XrayOutboundDialer) DialContext(ctx context.Context, network string, destination M.Socksaddr) (net.Conn, error) {
-	ctx = session.ContextWithOutbound(ctx, &session.Outbound{
-		Target: ToDestination(destination, ToNetwork(network)),
-	})
+	outbounds := session.OutboundsFromContext(ctx)
+	if len(outbounds) == 0 {
+		outbounds = []*session.Outbound{{}}
+		ctx = session.ContextWithOutbounds(ctx, outbounds)
+	}
+	ob := outbounds[len(outbounds) - 1]
+	ob.Target = ToDestination(destination, ToNetwork(network))
+	
 	opts := []pipe.Option{pipe.WithSizeLimit(64 * 1024)}
 	uplinkReader, uplinkWriter := pipe.New(opts...)
 	downlinkReader, downlinkWriter := pipe.New(opts...)
diff --git a/features/routing/session/context.go b/features/routing/session/context.go
index c900219dc..3c9764b3f 100644
--- a/features/routing/session/context.go
+++ b/features/routing/session/context.go
@@ -124,9 +124,11 @@ func (ctx *Context) GetSkipDNSResolve() bool {
 
 // AsRoutingContext creates a context from context.context with session info.
 func AsRoutingContext(ctx context.Context) routing.Context {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
 	return &Context{
 		Inbound:  session.InboundFromContext(ctx),
-		Outbound: session.OutboundFromContext(ctx),
+		Outbound: ob,
 		Content:  session.ContentFromContext(ctx),
 	}
 }
diff --git a/proxy/blackhole/blackhole.go b/proxy/blackhole/blackhole.go
index 4b8194172..23c9c2919 100644
--- a/proxy/blackhole/blackhole.go
+++ b/proxy/blackhole/blackhole.go
@@ -31,10 +31,9 @@ func New(ctx context.Context, config *Config) (*Handler, error) {
 
 // Process implements OutboundHandler.Dispatch().
 func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound != nil {
-		outbound.Name = "blackhole"
-	}
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	ob.Name = "blackhole"
 	
 	nBytes := h.response.WriteTo(link.Writer)
 	if nBytes > 0 {
diff --git a/proxy/blackhole/blackhole_test.go b/proxy/blackhole/blackhole_test.go
index 8e487e0c1..6a9cb8e84 100644
--- a/proxy/blackhole/blackhole_test.go
+++ b/proxy/blackhole/blackhole_test.go
@@ -7,13 +7,15 @@ import (
 	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/buf"
 	"github.com/xtls/xray-core/common/serial"
+	"github.com/xtls/xray-core/common/session"
 	"github.com/xtls/xray-core/proxy/blackhole"
 	"github.com/xtls/xray-core/transport"
 	"github.com/xtls/xray-core/transport/pipe"
 )
 
 func TestBlackholeHTTPResponse(t *testing.T) {
-	handler, err := blackhole.New(context.Background(), &blackhole.Config{
+	ctx := session.ContextWithOutbounds(context.Background(), []*session.Outbound{{}})
+	handler, err := blackhole.New(ctx, &blackhole.Config{
 		Response: serial.ToTypedMessage(&blackhole.HTTPResponse{}),
 	})
 	common.Must(err)
@@ -32,7 +34,7 @@ func TestBlackholeHTTPResponse(t *testing.T) {
 		Reader: reader,
 		Writer: writer,
 	}
-	common.Must(handler.Process(context.Background(), &link, nil))
+	common.Must(handler.Process(ctx, &link, nil))
 	common.Must(rerr)
 	if mb.IsEmpty() {
 		t.Error("expect http response, but nothing")
diff --git a/proxy/dns/dns.go b/proxy/dns/dns.go
index 2cf21a429..86790f767 100644
--- a/proxy/dns/dns.go
+++ b/proxy/dns/dns.go
@@ -96,15 +96,16 @@ func parseIPQuery(b []byte) (r bool, domain string, id uint16, qType dnsmessage.
 
 // Process implements proxy.Outbound.
 func (h *Handler) Process(ctx context.Context, link *transport.Link, d internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("invalid outbound")
 	}
-	outbound.Name = "dns"
+	ob.Name = "dns"
 
-	srcNetwork := outbound.Target.Network
+	srcNetwork := ob.Target.Network
 
-	dest := outbound.Target
+	dest := ob.Target
 	if h.server.Network != net.Network_Unknown {
 		dest.Network = h.server.Network
 	}
diff --git a/proxy/dokodemo/dokodemo.go b/proxy/dokodemo/dokodemo.go
index 1c59fe623..5a07df5cb 100644
--- a/proxy/dokodemo/dokodemo.go
+++ b/proxy/dokodemo/dokodemo.go
@@ -86,10 +86,15 @@ func (d *DokodemoDoor) Process(ctx context.Context, network net.Network, conn st
 
 	destinationOverridden := false
 	if d.config.FollowRedirect {
-		if outbound := session.OutboundFromContext(ctx); outbound != nil && outbound.Target.IsValid() {
-			dest = outbound.Target
-			destinationOverridden = true
-		} else if handshake, ok := conn.(hasHandshakeAddressContext); ok {
+		outbounds := session.OutboundsFromContext(ctx)
+		if len(outbounds) > 0 {
+			ob := outbounds[len(outbounds) - 1]
+			if ob.Target.IsValid() {
+				dest = ob.Target
+				destinationOverridden = true
+			}
+		}
+		if handshake, ok := conn.(hasHandshakeAddressContext); ok && !destinationOverridden {
 			addr := handshake.HandshakeAddressContext(ctx)
 			if addr != nil {
 				dest.Address = addr
@@ -103,7 +108,7 @@ func (d *DokodemoDoor) Process(ctx context.Context, network net.Network, conn st
 
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "dokodemo-door"
-	inbound.SetCanSpliceCopy(1)
+	inbound.CanSpliceCopy = 1
 	inbound.User = &protocol.MemoryUser{
 		Level: d.config.UserLevel,
 	}
diff --git a/proxy/freedom/freedom.go b/proxy/freedom/freedom.go
index 0176929cc..9e6afc9d1 100644
--- a/proxy/freedom/freedom.go
+++ b/proxy/freedom/freedom.go
@@ -106,16 +106,16 @@ func isValidAddress(addr *net.IPOrDomain) bool {
 
 // Process implements proxy.Outbound.
 func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("target not specified.")
 	}
-	outbound.Name = "freedom"
+	ob.Name = "freedom"
+	ob.CanSpliceCopy = 1
 	inbound := session.InboundFromContext(ctx)
-	if inbound != nil {
-		inbound.SetCanSpliceCopy(1)
-	}
-	destination := outbound.Target
+
+	destination := ob.Target
 	UDPOverride := net.UDPDestination(nil, 0)
 	if h.config.DestinationOverride != nil {
 		server := h.config.DestinationOverride.Server
diff --git a/proxy/http/client.go b/proxy/http/client.go
index 72060c4d2..80a0328a7 100644
--- a/proxy/http/client.go
+++ b/proxy/http/client.go
@@ -69,16 +69,14 @@ func NewClient(ctx context.Context, config *ClientConfig) (*Client, error) {
 
 // Process implements proxy.Outbound.Process. We first create a socket tunnel via HTTP CONNECT method, then redirect all inbound traffic to that tunnel.
 func (c *Client) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("target not specified.")
 	}
-	outbound.Name = "http"
-	inbound := session.InboundFromContext(ctx)
-	if inbound != nil {
-		inbound.SetCanSpliceCopy(2)
-	}
-	target := outbound.Target
+	ob.Name = "http"
+	ob.CanSpliceCopy = 2
+	target := ob.Target
 	targetAddr := target.NetAddr()
 
 	if target.Network == net.Network_UDP {
@@ -175,9 +173,10 @@ func fillRequestHeader(ctx context.Context, header []*Header) ([]*Header, error)
 	}
 
 	inbound := session.InboundFromContext(ctx)
-	outbound := session.OutboundFromContext(ctx)
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
 
-	if inbound == nil || outbound == nil {
+	if inbound == nil || ob == nil {
 		return nil, newError("missing inbound or outbound metadata from context")
 	}
 
@@ -186,7 +185,7 @@ func fillRequestHeader(ctx context.Context, header []*Header) ([]*Header, error)
 		Target net.Destination
 	}{
 		Source: inbound.Source,
-		Target: outbound.Target,
+		Target: ob.Target,
 	}
 
 	filled := make([]*Header, len(header))
diff --git a/proxy/http/server.go b/proxy/http/server.go
index 511d9b08c..a7df317dc 100644
--- a/proxy/http/server.go
+++ b/proxy/http/server.go
@@ -85,7 +85,7 @@ type readerOnly struct {
 func (s *Server) Process(ctx context.Context, network net.Network, conn stat.Connection, dispatcher routing.Dispatcher) error {
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "http"
-	inbound.SetCanSpliceCopy(2)
+	inbound.CanSpliceCopy = 2
 	inbound.User = &protocol.MemoryUser{
 		Level: s.config.UserLevel,
 	}
diff --git a/proxy/loopback/loopback.go b/proxy/loopback/loopback.go
index 30c39bd96..f3be5a95d 100644
--- a/proxy/loopback/loopback.go
+++ b/proxy/loopback/loopback.go
@@ -22,12 +22,13 @@ type Loopback struct {
 }
 
 func (l *Loopback) Process(ctx context.Context, link *transport.Link, _ internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("target not specified.")
 	}
-	outbound.Name = "loopback"
-	destination := outbound.Target
+	ob.Name = "loopback"
+	destination := ob.Target
 
 	newError("opening connection to ", destination).WriteToLog(session.ExportIDToError(ctx))
 
diff --git a/proxy/proxy.go b/proxy/proxy.go
index 6a5a1798a..2507d0296 100644
--- a/proxy/proxy.go
+++ b/proxy/proxy.go
@@ -474,45 +474,73 @@ func CopyRawConnIfExist(ctx context.Context, readerConn net.Conn, writerConn net
 	readerConn, readCounter, _ := UnwrapRawConn(readerConn)
 	writerConn, _, writeCounter := UnwrapRawConn(writerConn)
 	reader := buf.NewReader(readerConn)
-	if inbound := session.InboundFromContext(ctx); inbound != nil {
-		if tc, ok := writerConn.(*net.TCPConn); ok && readerConn != nil && writerConn != nil && (runtime.GOOS == "linux" || runtime.GOOS == "android") {
-			for inbound.CanSpliceCopy != 3 {
-				if inbound.CanSpliceCopy == 1 {
-					newError("CopyRawConn splice").WriteToLog(session.ExportIDToError(ctx))
-					statWriter, _ := writer.(*dispatcher.SizeStatWriter)
-					//runtime.Gosched() // necessary
-					time.Sleep(time.Millisecond) // without this, there will be a rare ssl error for freedom splice
-					w, err := tc.ReadFrom(readerConn)
-					if readCounter != nil {
-						readCounter.Add(w) // outbound stats
-					}
-					if writeCounter != nil {
-						writeCounter.Add(w) // inbound stats
-					}
-					if statWriter != nil {
-						statWriter.Counter.Add(w) // user stats
-					}
-					if err != nil && errors.Cause(err) != io.EOF {
-						return err
-					}
-					return nil
-				}
-				buffer, err := reader.ReadMultiBuffer()
-				if !buffer.IsEmpty() {
-					if readCounter != nil {
-						readCounter.Add(int64(buffer.Len()))
-					}
-					timer.Update()
-					if werr := writer.WriteMultiBuffer(buffer); werr != nil {
-						return werr
-					}
-				}
-				if err != nil {
-					return err
-				}
-			}
+	if runtime.GOOS != "linux" && runtime.GOOS != "android" {
+		return readV(ctx, reader, writer, timer, readCounter)
+	}
+	tc, ok := writerConn.(*net.TCPConn)
+	if !ok || readerConn == nil || writerConn == nil {
+		return readV(ctx, reader, writer, timer, readCounter)
+	}
+	inbound := session.InboundFromContext(ctx)
+	if inbound == nil || inbound.CanSpliceCopy == 3 {
+		return readV(ctx, reader, writer, timer, readCounter)
+	}
+	outbounds := session.OutboundsFromContext(ctx)
+	if len(outbounds) == 0 {
+		return readV(ctx, reader, writer, timer, readCounter)
+	}
+	for _, ob := range outbounds {
+		if ob.CanSpliceCopy == 3 {
+			return readV(ctx, reader, writer, timer, readCounter)
 		}
 	}
+
+	for {
+		inbound := session.InboundFromContext(ctx)
+		outbounds := session.OutboundsFromContext(ctx)
+		var splice = inbound.CanSpliceCopy == 1
+		for _, ob := range outbounds {
+			if ob.CanSpliceCopy != 1 {
+				splice = false
+			}
+		}
+		if splice {
+			newError("CopyRawConn splice").WriteToLog(session.ExportIDToError(ctx))
+			statWriter, _ := writer.(*dispatcher.SizeStatWriter)
+			//runtime.Gosched() // necessary
+			time.Sleep(time.Millisecond) // without this, there will be a rare ssl error for freedom splice
+			w, err := tc.ReadFrom(readerConn)
+			if readCounter != nil {
+				readCounter.Add(w) // outbound stats
+			}
+			if writeCounter != nil {
+				writeCounter.Add(w) // inbound stats
+			}
+			if statWriter != nil {
+				statWriter.Counter.Add(w) // user stats
+			}
+			if err != nil && errors.Cause(err) != io.EOF {
+				return err
+			}
+			return nil
+		}
+		buffer, err := reader.ReadMultiBuffer()
+		if !buffer.IsEmpty() {
+			if readCounter != nil {
+				readCounter.Add(int64(buffer.Len()))
+			}
+			timer.Update()
+			if werr := writer.WriteMultiBuffer(buffer); werr != nil {
+				return werr
+			}
+		}
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func readV(ctx context.Context, reader buf.Reader, writer buf.Writer, timer signal.ActivityUpdater, readCounter stats.Counter) error {
 	newError("CopyRawConn readv").WriteToLog(session.ExportIDToError(ctx))
 	if err := buf.Copy(reader, writer, buf.UpdateActivity(timer), buf.AddToStatCounter(readCounter)); err != nil {
 		return newError("failed to process response").Base(err)
diff --git a/proxy/shadowsocks/client.go b/proxy/shadowsocks/client.go
index 57d8f81c7..8ebe7631b 100644
--- a/proxy/shadowsocks/client.go
+++ b/proxy/shadowsocks/client.go
@@ -49,16 +49,14 @@ func NewClient(ctx context.Context, config *ClientConfig) (*Client, error) {
 
 // Process implements OutboundHandler.Process().
 func (c *Client) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("target not specified")
 	}
-	outbound.Name = "shadowsocks"
-	inbound := session.InboundFromContext(ctx)
-	if inbound != nil {
-		inbound.SetCanSpliceCopy(3)
-	}
-	destination := outbound.Target
+	ob.Name = "shadowsocks"
+	ob.CanSpliceCopy = 3
+	destination := ob.Target
 	network := destination.Network
 
 	var server *protocol.ServerSpec
diff --git a/proxy/shadowsocks/server.go b/proxy/shadowsocks/server.go
index 2975ba70a..8253506a6 100644
--- a/proxy/shadowsocks/server.go
+++ b/proxy/shadowsocks/server.go
@@ -73,7 +73,7 @@ func (s *Server) Network() []net.Network {
 func (s *Server) Process(ctx context.Context, network net.Network, conn stat.Connection, dispatcher routing.Dispatcher) error {
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "shadowsocks"
-	inbound.SetCanSpliceCopy(3)
+	inbound.CanSpliceCopy = 3
 	
 	switch network {
 	case net.Network_TCP:
diff --git a/proxy/shadowsocks_2022/inbound.go b/proxy/shadowsocks_2022/inbound.go
index 00314c90e..f1eb76a5a 100644
--- a/proxy/shadowsocks_2022/inbound.go
+++ b/proxy/shadowsocks_2022/inbound.go
@@ -66,7 +66,7 @@ func (i *Inbound) Network() []net.Network {
 func (i *Inbound) Process(ctx context.Context, network net.Network, connection stat.Connection, dispatcher routing.Dispatcher) error {
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "shadowsocks-2022"
-	inbound.SetCanSpliceCopy(3)
+	inbound.CanSpliceCopy = 3
 
 	var metadata M.Metadata
 	if inbound.Source.IsValid() {
diff --git a/proxy/shadowsocks_2022/inbound_multi.go b/proxy/shadowsocks_2022/inbound_multi.go
index df837894d..f80ec6d11 100644
--- a/proxy/shadowsocks_2022/inbound_multi.go
+++ b/proxy/shadowsocks_2022/inbound_multi.go
@@ -155,7 +155,7 @@ func (i *MultiUserInbound) Network() []net.Network {
 func (i *MultiUserInbound) Process(ctx context.Context, network net.Network, connection stat.Connection, dispatcher routing.Dispatcher) error {
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "shadowsocks-2022-multi"
-	inbound.SetCanSpliceCopy(3)
+	inbound.CanSpliceCopy = 3
 
 	var metadata M.Metadata
 	if inbound.Source.IsValid() {
diff --git a/proxy/shadowsocks_2022/inbound_relay.go b/proxy/shadowsocks_2022/inbound_relay.go
index 7317f8dd2..1c4b82487 100644
--- a/proxy/shadowsocks_2022/inbound_relay.go
+++ b/proxy/shadowsocks_2022/inbound_relay.go
@@ -87,7 +87,7 @@ func (i *RelayInbound) Network() []net.Network {
 func (i *RelayInbound) Process(ctx context.Context, network net.Network, connection stat.Connection, dispatcher routing.Dispatcher) error {
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "shadowsocks-2022-relay"
-	inbound.SetCanSpliceCopy(3)
+	inbound.CanSpliceCopy = 3
 
 	var metadata M.Metadata
 	if inbound.Source.IsValid() {
diff --git a/proxy/shadowsocks_2022/outbound.go b/proxy/shadowsocks_2022/outbound.go
index bc1eb556f..cac9a91bb 100644
--- a/proxy/shadowsocks_2022/outbound.go
+++ b/proxy/shadowsocks_2022/outbound.go
@@ -65,15 +65,16 @@ func (o *Outbound) Process(ctx context.Context, link *transport.Link, dialer int
 	inbound := session.InboundFromContext(ctx)
 	if inbound != nil {
 		inboundConn = inbound.Conn
-		inbound.SetCanSpliceCopy(3)
 	}
 
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("target not specified")
 	}
-	outbound.Name = "shadowsocks-2022"
-	destination := outbound.Target
+	ob.Name = "shadowsocks-2022"
+	ob.CanSpliceCopy = 3
+	destination := ob.Target
 	network := destination.Network
 
 	newError("tunneling request to ", destination, " via ", o.server.NetAddr()).WriteToLog(session.ExportIDToError(ctx))
diff --git a/proxy/socks/client.go b/proxy/socks/client.go
index 82591be43..b283eb650 100644
--- a/proxy/socks/client.go
+++ b/proxy/socks/client.go
@@ -57,17 +57,15 @@ func NewClient(ctx context.Context, config *ClientConfig) (*Client, error) {
 
 // Process implements proxy.Outbound.Process.
 func (c *Client) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("target not specified.")
 	}
-	outbound.Name = "socks"
-	inbound := session.InboundFromContext(ctx)
-	if inbound != nil {
-		inbound.SetCanSpliceCopy(2)
-	}
+	ob.Name = "socks"
+	ob.CanSpliceCopy = 2
 	// Destination of the inner request.
-	destination := outbound.Target
+	destination := ob.Target
 
 	// Outbound server.
 	var server *protocol.ServerSpec
diff --git a/proxy/socks/server.go b/proxy/socks/server.go
index 2f7897572..0109d5b42 100644
--- a/proxy/socks/server.go
+++ b/proxy/socks/server.go
@@ -65,7 +65,7 @@ func (s *Server) Network() []net.Network {
 func (s *Server) Process(ctx context.Context, network net.Network, conn stat.Connection, dispatcher routing.Dispatcher) error {
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "socks"
-	inbound.SetCanSpliceCopy(2)
+	inbound.CanSpliceCopy = 2
 	inbound.User = &protocol.MemoryUser{
 		Level: s.config.UserLevel,
 	}
diff --git a/proxy/trojan/client.go b/proxy/trojan/client.go
index d6b95fc0b..3a4d838ae 100644
--- a/proxy/trojan/client.go
+++ b/proxy/trojan/client.go
@@ -50,16 +50,14 @@ func NewClient(ctx context.Context, config *ClientConfig) (*Client, error) {
 
 // Process implements OutboundHandler.Process().
 func (c *Client) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("target not specified")
 	}
-	outbound.Name = "trojan"
-	inbound := session.InboundFromContext(ctx)
-	if inbound != nil {
-		inbound.SetCanSpliceCopy(3)
-	}
-	destination := outbound.Target
+	ob.Name = "trojan"
+	ob.CanSpliceCopy = 3
+	destination := ob.Target
 	network := destination.Network
 
 	var server *protocol.ServerSpec
diff --git a/proxy/trojan/server.go b/proxy/trojan/server.go
index 5c3fcd911..bc52c2b14 100644
--- a/proxy/trojan/server.go
+++ b/proxy/trojan/server.go
@@ -215,7 +215,7 @@ func (s *Server) Process(ctx context.Context, network net.Network, conn stat.Con
 
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "trojan"
-	inbound.SetCanSpliceCopy(3)
+	inbound.CanSpliceCopy = 3
 	inbound.User = user
 	sessionPolicy = s.policyManager.ForLevel(user.Level)
 
diff --git a/proxy/vless/encoding/encoding.go b/proxy/vless/encoding/encoding.go
index 5956389af..2976be749 100644
--- a/proxy/vless/encoding/encoding.go
+++ b/proxy/vless/encoding/encoding.go
@@ -174,15 +174,18 @@ func DecodeResponseHeader(reader io.Reader, request *protocol.RequestHeader) (*A
 }
 
 // XtlsRead filter and read xtls protocol
-func XtlsRead(reader buf.Reader, writer buf.Writer, timer signal.ActivityUpdater, conn net.Conn, input *bytes.Reader, rawInput *bytes.Buffer, trafficState *proxy.TrafficState, ctx context.Context) error {
+func XtlsRead(reader buf.Reader, writer buf.Writer, timer signal.ActivityUpdater, conn net.Conn, input *bytes.Reader, rawInput *bytes.Buffer, trafficState *proxy.TrafficState, ob *session.Outbound, ctx context.Context) error {
 	err := func() error {
 		for {
 			if trafficState.ReaderSwitchToDirectCopy {
 				var writerConn net.Conn
-				if inbound := session.InboundFromContext(ctx); inbound != nil && inbound.Conn != nil {
+				if inbound := session.InboundFromContext(ctx); inbound != nil && inbound.Conn != nil && ob != nil {
 					writerConn = inbound.Conn
 					if inbound.CanSpliceCopy == 2 {
-						inbound.CanSpliceCopy = 1 // force the value to 1, don't use setter
+						inbound.CanSpliceCopy = 1
+					}
+					if ob.CanSpliceCopy == 2 { // ob need to be passed in due to context can change
+						ob.CanSpliceCopy = 1
 					}
 				}
 				return proxy.CopyRawConnIfExist(ctx, conn, writerConn, writer, timer)
@@ -219,14 +222,19 @@ func XtlsRead(reader buf.Reader, writer buf.Writer, timer signal.ActivityUpdater
 }
 
 // XtlsWrite filter and write xtls protocol
-func XtlsWrite(reader buf.Reader, writer buf.Writer, timer signal.ActivityUpdater, conn net.Conn, trafficState *proxy.TrafficState, ctx context.Context) error {
+func XtlsWrite(reader buf.Reader, writer buf.Writer, timer signal.ActivityUpdater, conn net.Conn, trafficState *proxy.TrafficState, ob *session.Outbound, ctx context.Context) error {
 	err := func() error {
 		var ct stats.Counter
 		for {
 			buffer, err := reader.ReadMultiBuffer()
 			if trafficState.WriterSwitchToDirectCopy {
-				if inbound := session.InboundFromContext(ctx); inbound != nil && inbound.CanSpliceCopy == 2 {
-					inbound.CanSpliceCopy = 1 // force the value to 1, don't use setter
+				if inbound := session.InboundFromContext(ctx); inbound != nil && ob != nil {
+					if inbound.CanSpliceCopy == 2 {
+						inbound.CanSpliceCopy = 1
+					}
+					if ob.CanSpliceCopy == 2 {
+						ob.CanSpliceCopy = 1
+					}
 				}
 				rawConn, _, writerCounter := proxy.UnwrapRawConn(conn)
 				writer = buf.NewWriter(rawConn)
diff --git a/proxy/vless/inbound/inbound.go b/proxy/vless/inbound/inbound.go
index 0ffa61d2a..7d2dd5071 100644
--- a/proxy/vless/inbound/inbound.go
+++ b/proxy/vless/inbound/inbound.go
@@ -449,7 +449,7 @@ func (h *Handler) Process(ctx context.Context, network net.Network, connection s
 	switch requestAddons.Flow {
 	case vless.XRV:
 		if account.Flow == requestAddons.Flow {
-			inbound.SetCanSpliceCopy(2)
+			inbound.CanSpliceCopy = 2
 			switch request.Command {
 			case protocol.RequestCommandUDP:
 				return newError(requestAddons.Flow + " doesn't support UDP").AtWarning()
@@ -479,7 +479,7 @@ func (h *Handler) Process(ctx context.Context, network net.Network, connection s
 			return newError(account.ID.String() + " is not able to use " + requestAddons.Flow).AtWarning()
 		}
 	case "":
-		inbound.SetCanSpliceCopy(3)
+		inbound.CanSpliceCopy = 3
 		if account.Flow == vless.XRV && (request.Command == protocol.RequestCommandTCP || isMuxAndNotXUDP(request, first)) {
 			return newError(account.ID.String() + " is not able to use \"\". Note that the pure TLS proxy has certain TLS in TLS characters.").AtWarning()
 		}
@@ -523,7 +523,7 @@ func (h *Handler) Process(ctx context.Context, network net.Network, connection s
 		if requestAddons.Flow == vless.XRV {
 			ctx1 := session.ContextWithInbound(ctx, nil) // TODO enable splice
 			clientReader = proxy.NewVisionReader(clientReader, trafficState, ctx1)
-			err = encoding.XtlsRead(clientReader, serverWriter, timer, connection, input, rawInput, trafficState, ctx1)
+			err = encoding.XtlsRead(clientReader, serverWriter, timer, connection, input, rawInput, trafficState, nil, ctx1)
 		} else {
 			// from clientReader.ReadMultiBuffer to serverWriter.WriteMultiBufer
 			err = buf.Copy(clientReader, serverWriter, buf.UpdateActivity(timer))
@@ -560,7 +560,9 @@ func (h *Handler) Process(ctx context.Context, network net.Network, connection s
 
 		var err error
 		if requestAddons.Flow == vless.XRV {
-			err = encoding.XtlsWrite(serverReader, clientWriter, timer, connection, trafficState, ctx)
+			outbounds := session.OutboundsFromContext(ctx)
+			ob := outbounds[len(outbounds) - 1]
+			err = encoding.XtlsWrite(serverReader, clientWriter, timer, connection, trafficState, ob, ctx)
 		} else {
 			// from serverReader.ReadMultiBuffer to clientWriter.WriteMultiBufer
 			err = buf.Copy(serverReader, clientWriter, buf.UpdateActivity(timer))
diff --git a/proxy/vless/outbound/outbound.go b/proxy/vless/outbound/outbound.go
index a93688139..bf98253b4 100644
--- a/proxy/vless/outbound/outbound.go
+++ b/proxy/vless/outbound/outbound.go
@@ -70,12 +70,12 @@ func New(ctx context.Context, config *Config) (*Handler, error) {
 
 // Process implements proxy.Outbound.Process().
 func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("target not specified").AtError()
 	}
-	outbound.Name = "vless"
-	inbound := session.InboundFromContext(ctx)
+	ob.Name = "vless"
 
 	var rec *protocol.ServerSpec
 	var conn stat.Connection
@@ -96,7 +96,7 @@ func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer inte
 	if statConn, ok := iConn.(*stat.CounterConnection); ok {
 		iConn = statConn.Connection
 	}
-	target := outbound.Target
+	target := ob.Target
 	newError("tunneling request to ", target, " via ", rec.Destination().NetAddr()).AtInfo().WriteToLog(session.ExportIDToError(ctx))
 
 	command := protocol.RequestCommandTCP
@@ -130,9 +130,7 @@ func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer inte
 		requestAddons.Flow = requestAddons.Flow[:16]
 		fallthrough
 	case vless.XRV:
-		if inbound != nil {
-			inbound.SetCanSpliceCopy(2)
-		}
+		ob.CanSpliceCopy = 2
 		switch request.Command {
 		case protocol.RequestCommandUDP:
 			if !allowUDP443 && request.Port == 443 {
@@ -161,9 +159,7 @@ func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer inte
 			rawInput = (*bytes.Buffer)(unsafe.Pointer(p + r.Offset))
 		}
 	default:
-		if inbound != nil {
-			inbound.SetCanSpliceCopy(3)
-		}
+		ob.CanSpliceCopy = 3
 	}
 
 	var newCtx context.Context
@@ -238,8 +234,8 @@ func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer inte
 					return newError(`failed to use `+requestAddons.Flow+`, found outer tls version `, utlsConn.ConnectionState().Version).AtWarning()
 				}
 			}
-			ctx1 := session.ContextWithOutbound(ctx, nil) // TODO enable splice
-			err = encoding.XtlsWrite(clientReader, serverWriter, timer, conn, trafficState, ctx1)
+			ctx1 := session.ContextWithInbound(ctx, nil) // TODO enable splice
+			err = encoding.XtlsWrite(clientReader, serverWriter, timer, conn, trafficState, ob, ctx1)
 		} else {
 			// from clientReader.ReadMultiBuffer to serverWriter.WriteMultiBufer
 			err = buf.Copy(clientReader, serverWriter, buf.UpdateActivity(timer))
@@ -277,7 +273,7 @@ func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer inte
 		}
 
 		if requestAddons.Flow == vless.XRV {
-			err = encoding.XtlsRead(serverReader, clientWriter, timer, conn, input, rawInput, trafficState, ctx)
+			err = encoding.XtlsRead(serverReader, clientWriter, timer, conn, input, rawInput, trafficState, ob, ctx)
 		} else {
 			// from serverReader.ReadMultiBuffer to clientWriter.WriteMultiBufer
 			err = buf.Copy(serverReader, clientWriter, buf.UpdateActivity(timer))
diff --git a/proxy/vmess/inbound/inbound.go b/proxy/vmess/inbound/inbound.go
index 679ea5da6..f5340f20c 100644
--- a/proxy/vmess/inbound/inbound.go
+++ b/proxy/vmess/inbound/inbound.go
@@ -257,7 +257,7 @@ func (h *Handler) Process(ctx context.Context, network net.Network, connection s
 
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "vmess"
-	inbound.SetCanSpliceCopy(3)
+	inbound.CanSpliceCopy = 3
 	inbound.User = request.User
 
 	sessionPolicy = h.policyManager.ForLevel(request.User.Level)
diff --git a/proxy/vmess/outbound/outbound.go b/proxy/vmess/outbound/outbound.go
index c3c55d956..8f102dbb1 100644
--- a/proxy/vmess/outbound/outbound.go
+++ b/proxy/vmess/outbound/outbound.go
@@ -60,15 +60,13 @@ func New(ctx context.Context, config *Config) (*Handler, error) {
 
 // Process implements proxy.Outbound.Process().
 func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("target not specified").AtError()
 	}
-	outbound.Name = "vmess"
-	inbound := session.InboundFromContext(ctx)
-	if inbound != nil {
-		inbound.SetCanSpliceCopy(3)
-	}
+	ob.Name = "vmess"
+	ob.CanSpliceCopy = 3
 
 	var rec *protocol.ServerSpec
 	var conn stat.Connection
@@ -87,7 +85,7 @@ func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer inte
 	}
 	defer conn.Close()
 
-	target := outbound.Target
+	target := ob.Target
 	newError("tunneling request to ", target, " via ", rec.Destination().NetAddr()).WriteToLog(session.ExportIDToError(ctx))
 
 	command := protocol.RequestCommandTCP
diff --git a/proxy/wireguard/client.go b/proxy/wireguard/client.go
index 4136525e6..00a6fa51a 100644
--- a/proxy/wireguard/client.go
+++ b/proxy/wireguard/client.go
@@ -127,22 +127,20 @@ func (h *Handler) processWireGuard(dialer internet.Dialer) (err error) {
 
 // Process implements OutboundHandler.Dispatch().
 func (h *Handler) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
-	outbound := session.OutboundFromContext(ctx)
-	if outbound == nil || !outbound.Target.IsValid() {
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
+	if !ob.Target.IsValid() {
 		return newError("target not specified")
 	}
-	outbound.Name = "wireguard"
-	inbound := session.InboundFromContext(ctx)
-	if inbound != nil {
-		inbound.SetCanSpliceCopy(3)
-	}
+	ob.Name = "wireguard"
+	ob.CanSpliceCopy = 3
 
 	if err := h.processWireGuard(dialer); err != nil {
 		return err
 	}
 
 	// Destination of the inner request.
-	destination := outbound.Target
+	destination := ob.Target
 	command := protocol.RequestCommandTCP
 	if destination.Network == net.Network_UDP {
 		command = protocol.RequestCommandUDP
diff --git a/proxy/wireguard/server.go b/proxy/wireguard/server.go
index bdb4e8018..3d3b584ce 100644
--- a/proxy/wireguard/server.go
+++ b/proxy/wireguard/server.go
@@ -79,13 +79,15 @@ func (*Server) Network() []net.Network {
 func (s *Server) Process(ctx context.Context, network net.Network, conn stat.Connection, dispatcher routing.Dispatcher) error {
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "wireguard"
-	inbound.SetCanSpliceCopy(3)
+	inbound.CanSpliceCopy = 3
+	outbounds := session.OutboundsFromContext(ctx)
+	ob := outbounds[len(outbounds) - 1]
 
 	s.info = routingInfo{
 		ctx:         core.ToBackgroundDetachedContext(ctx),
 		dispatcher:  dispatcher,
 		inboundTag:  session.InboundFromContext(ctx),
-		outboundTag: session.OutboundFromContext(ctx),
+		outboundTag: ob,
 		contentTag:  session.ContentFromContext(ctx),
 	}
 
@@ -145,7 +147,7 @@ func (s *Server) forwardConnection(dest net.Destination, conn net.Conn) {
 		ctx = session.ContextWithInbound(ctx, s.info.inboundTag)
 	}
 	if s.info.outboundTag != nil {
-		ctx = session.ContextWithOutbound(ctx, s.info.outboundTag)
+		ctx = session.ContextWithOutbounds(ctx, []*session.Outbound{s.info.outboundTag})
 	}
 	if s.info.contentTag != nil {
 		ctx = session.ContextWithContent(ctx, s.info.contentTag)
diff --git a/transport/internet/dialer.go b/transport/internet/dialer.go
index 3d5d046f7..ffa868a30 100644
--- a/transport/internet/dialer.go
+++ b/transport/internet/dialer.go
@@ -112,7 +112,12 @@ func canLookupIP(ctx context.Context, dst net.Destination, sockopt *SocketConfig
 func redirect(ctx context.Context, dst net.Destination, obt string) net.Conn {
 	newError("redirecting request " + dst.String() + " to " + obt).WriteToLog(session.ExportIDToError(ctx))
 	h := obm.GetHandler(obt)
-	ctx = session.ContextWithOutbound(ctx, &session.Outbound{Target: dst, Gateway: nil})
+	outbounds := session.OutboundsFromContext(ctx)
+    ctx = session.ContextWithOutbounds(ctx, append(outbounds, &session.Outbound{
+		Target: dst, 
+		Gateway: nil,
+		Tag: obt,
+	})) // add another outbound in session ctx
 	if h != nil {
 		ur, uw := pipe.New(pipe.OptionsFromContext(ctx)...)
 		dr, dw := pipe.New(pipe.OptionsFromContext(ctx)...)
@@ -131,8 +136,10 @@ func redirect(ctx context.Context, dst net.Destination, obt string) net.Conn {
 // DialSystem calls system dialer to create a network connection.
 func DialSystem(ctx context.Context, dest net.Destination, sockopt *SocketConfig) (net.Conn, error) {
 	var src net.Address
-	if outbound := session.OutboundFromContext(ctx); outbound != nil {
-		src = outbound.Gateway
+	outbounds := session.OutboundsFromContext(ctx)
+	if len(outbounds) > 0 {
+		ob := outbounds[len(outbounds) - 1]
+		src = ob.Gateway
 	}
 	if sockopt == nil {
 		return effectiveSystemDialer.Dial(ctx, src, dest, sockopt)
diff --git a/transport/internet/grpc/dial.go b/transport/internet/grpc/dial.go
index 5d5789b47..a4b03cedc 100644
--- a/transport/internet/grpc/dial.go
+++ b/transport/internet/grpc/dial.go
@@ -118,7 +118,7 @@ func getGrpcClient(ctx context.Context, dest net.Destination, streamSettings *in
 			address := net.ParseAddress(rawHost)
 
 			gctx = session.ContextWithID(gctx, session.IDFromContext(ctx))
-			gctx = session.ContextWithOutbound(gctx, session.OutboundFromContext(ctx))
+			gctx = session.ContextWithOutbounds(gctx, session.OutboundsFromContext(ctx))
 			gctx = session.ContextWithTimeoutOnly(gctx, true)
 
 			c, err := internet.DialSystem(gctx, net.TCPDestination(address, port), sockopt)
diff --git a/transport/internet/http/dialer.go b/transport/internet/http/dialer.go
index acccd0b72..0148658c5 100644
--- a/transport/internet/http/dialer.go
+++ b/transport/internet/http/dialer.go
@@ -68,7 +68,7 @@ func getHTTPClient(ctx context.Context, dest net.Destination, streamSettings *in
 			address := net.ParseAddress(rawHost)
 
 			hctx = session.ContextWithID(hctx, session.IDFromContext(ctx))
-			hctx = session.ContextWithOutbound(hctx, session.OutboundFromContext(ctx))
+			hctx = session.ContextWithOutbounds(hctx, session.OutboundsFromContext(ctx))
 			hctx = session.ContextWithTimeoutOnly(hctx, true)
 
 			pconn, err := internet.DialSystem(hctx, net.TCPDestination(address, port), sockopt)