Index: gcc-6-6.2.1-4.1/src/libgo/go/net/sendfile_gnu.go
===================================================================
--- /dev/null
+++ gcc-6-6.2.1-4.1/src/libgo/go/net/sendfile_gnu.go
@@ -0,0 +1,79 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"io"
+	"os"
+	"syscall"
+)
+
+// maxSendfileSize is the largest chunk size we ask the kernel to copy
+// at a time.
+const maxSendfileSize int = 4 << 20
+
+// sendFile copies the contents of r to c using the sendfile
+// system call to minimize copies.
+//
+// if handled == true, sendFile returns the number of bytes copied and any
+// non-EOF error.
+//
+// if handled == false, sendFile performed no work.
+func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
+	var remain int64 = 1 << 62 // by default, copy until EOF
+
+	lr, ok := r.(*io.LimitedReader)
+	if ok {
+		remain, r = lr.N, lr.R
+		if remain <= 0 {
+			return 0, nil, true
+		}
+	}
+	f, ok := r.(*os.File)
+	if !ok {
+		return 0, nil, false
+	}
+
+	if err := c.writeLock(); err != nil {
+		return 0, err, true
+	}
+	defer c.writeUnlock()
+
+	dst := c.sysfd
+	src := int(f.Fd())
+	for remain > 0 {
+		n := maxSendfileSize
+		if int64(n) > remain {
+			n = int(remain)
+		}
+		n, err1 := syscall.Sendfile(dst, src, nil, n)
+		if n > 0 {
+			written += int64(n)
+			remain -= int64(n)
+		}
+		if n == 0 && err1 == nil {
+			break
+		}
+		if err1 == syscall.EAGAIN {
+			if err1 = c.pd.WaitWrite(); err1 == nil {
+				continue
+			}
+		}
+		if err1 != nil {
+			// This includes syscall.ENOSYS (no kernel
+			// support) and syscall.EINVAL (fd types which
+			// don't implement sendfile)
+			err = err1
+			break
+		}
+	}
+	if lr != nil {
+		lr.N = remain
+	}
+	if err != nil {
+		err = os.NewSyscallError("sendfile", err)
+	}
+	return written, err, written > 0
+}