Loopback outbound: Use DispatchLink() (#6005)

https://github.com/XTLS/Xray-core/pull/6000

Fixes https://github.com/XTLS/Xray-core/issues/5917

proxy/loopback/loopback.go

@@ -4,13 +4,8 @@ import (
 	"context"
 
 	"github.com/xtls/xray-core/common"
-	"github.com/xtls/xray-core/common/buf"
 	"github.com/xtls/xray-core/common/errors"
-	"github.com/xtls/xray-core/common/net"
-	"github.com/xtls/xray-core/common/net/cnc"
-	"github.com/xtls/xray-core/common/retry"
 	"github.com/xtls/xray-core/common/session"
-	"github.com/xtls/xray-core/common/task"
 	"github.com/xtls/xray-core/core"
 	"github.com/xtls/xray-core/features/routing"
 	"github.com/xtls/xray-core/transport"
@@ -32,83 +27,24 @@ func (l *Loopback) Process(ctx context.Context, link *transport.Link, _ internet
 	destination := ob.Target
 
 	errors.LogInfo(ctx, "opening connection to ", destination)
+	content := new(session.Content)
+	content.SkipDNSResolve = true
 
-	input := link.Reader
+	ctx = session.ContextWithContent(ctx, content)
-	output := link.Writer
+	inbound := &session.Inbound{}
+	originInbound := session.InboundFromContext(ctx)
+	if originInbound != nil {
+		// get a shallow copy to avoid modifying the inbound tag in upstream context
+		*inbound = *originInbound
+	}
+	inbound.Tag = l.config.InboundTag
+	ctx = session.ContextWithInbound(ctx, inbound)
 
-	var conn net.Conn
+	err := l.dispatcherInstance.DispatchLink(ctx, destination, link)
-	err := retry.ExponentialBackoff(2, 100).On(func() error {
-		dialDest := destination
-
-		content := new(session.Content)
-		content.SkipDNSResolve = true
-
-		ctx = session.ContextWithContent(ctx, content)
-
-		inbound := &session.Inbound{}
-		originInbound := session.InboundFromContext(ctx)
-		if originInbound != nil {
-			// get a shallow copy to avoid modifying the inbound tag in upstream context
-			*inbound = *originInbound
-		}
-
-		inbound.Tag = l.config.InboundTag
-
-		ctx = session.ContextWithInbound(ctx, inbound)
-
-		rawConn, err := l.dispatcherInstance.Dispatch(ctx, dialDest)
-		if err != nil {
-			return err
-		}
-
-		var readerOpt cnc.ConnectionOption
-		if dialDest.Network == net.Network_TCP {
-			readerOpt = cnc.ConnectionOutputMulti(rawConn.Reader)
-		} else {
-			readerOpt = cnc.ConnectionOutputMultiUDP(rawConn.Reader)
-		}
-
-		conn = cnc.NewConnection(cnc.ConnectionInputMulti(rawConn.Writer), readerOpt)
-		return nil
-	})
 	if err != nil {
-		return errors.New("failed to open connection to ", destination).Base(err)
+		errors.New(ctx, "failed to process loopback connection").Base(err)
+		return err
 	}
-	defer conn.Close()
-
-	requestDone := func() error {
-		var writer buf.Writer
-		if destination.Network == net.Network_TCP {
-			writer = buf.NewWriter(conn)
-		} else {
-			writer = &buf.SequentialWriter{Writer: conn}
-		}
-
-		if err := buf.Copy(input, writer); err != nil {
-			return errors.New("failed to process request").Base(err)
-		}
-
-		return nil
-	}
-
-	responseDone := func() error {
-		var reader buf.Reader
-		if destination.Network == net.Network_TCP {
-			reader = buf.NewReader(conn)
-		} else {
-			reader = buf.NewPacketReader(conn)
-		}
-		if err := buf.Copy(reader, output); err != nil {
-			return errors.New("failed to process response").Base(err)
-		}
-
-		return nil
-	}
-
-	if err := task.Run(ctx, requestDone, task.OnSuccess(responseDone, task.Close(output))); err != nil {
-		return errors.New("connection ends").Base(err)
-	}
-
 	return nil
 }