Refine buffered reader

common/bufio/buffer.go

@@ -29,6 +29,10 @@ func (r *BufferedReader) Read(p []byte) (n int, err error) {
 	return r.buffer.Read(p)
 }
 
+func (r *BufferedReader) WriteTo(w io.Writer) (n int64, err error) {
+	return CopyExtendedBuffer(NewExtendedWriter(w), NewExtendedReader(r.upstream), r.buffer)
+}
+
 func (w *BufferedReader) Upstream() any {
 	return w.upstream
 }

common/bufio/conn.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"io"
 	"net"
+	"os"
 	"time"
 
 	"github.com/sagernet/sing/common"
@@ -14,6 +15,27 @@ import (
 	"github.com/sagernet/sing/common/task"
 )
 
+type readOnlyReader struct {
+	io.Reader
+}
+
+func (r *readOnlyReader) WriteTo(w io.Writer) (n int64, err error) {
+	return Copy(w, r.Reader)
+}
+
+func needReadFromWrapper(dst io.ReaderFrom, src io.Reader) bool {
+	_, isTCPConn := dst.(*net.TCPConn)
+	if !isTCPConn {
+		return false
+	}
+	switch src.(type) {
+	case *net.TCPConn, *net.UnixConn, *os.File:
+		return false
+	default:
+		return true
+	}
+}
+
 func Copy(dst io.Writer, src io.Reader) (n int64, err error) {
 	src = N.UnwrapReader(src)
 	dst = N.UnwrapWriter(dst)
@@ -21,6 +43,9 @@ func Copy(dst io.Writer, src io.Reader) (n int64, err error) {
 		return wt.WriteTo(dst)
 	}
 	if rt, ok := dst.(io.ReaderFrom); ok {
+		if needReadFromWrapper(rt, src) {
+			src = &readOnlyReader{src}
+		}
 		return rt.ReadFrom(src)
 	}
 	return CopyExtended(NewExtendedWriter(dst), NewExtendedReader(src))
@@ -37,7 +62,11 @@ func CopyExtended(dst N.ExtendedWriter, src N.ExtendedReader) (n int64, err erro
 
 	_buffer := buf.StackNew()
 	defer common.KeepAlive(_buffer)
-	buffer := common.Dup(_buffer)
+
+	return CopyExtendedBuffer(dst, src, common.Dup(_buffer))
+}
+
+func CopyExtendedBuffer(dst N.ExtendedWriter, src N.ExtendedReader, buffer *buf.Buffer) (n int64, err error) {
 	buffer.IncRef()
 	defer buffer.DecRef()
 	for {