--- libgo/go/net/sendfile_bsdsunix.go.orig	2016-10-24 12:27:04 UTC
+++ libgo/go/net/sendfile_bsdsunix.go
@@ -0,0 +1,105 @@
+// 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) {
+	// BSDSUniX uses 0 as the "until EOF" value. If you pass in more bytes than the
+	// file contains, it will loop back to the beginning ad nauseum until it's sent
+	// exactly the number of bytes told to. As such, we need to know exactly how many
+	// bytes to send.
+	var remain int64 = 0
+
+	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 remain == 0 {
+		fi, err := f.Stat()
+		if err != nil {
+			return 0, err, false
+		}
+
+		remain = fi.Size()
+	}
+
+	// The other quirk with BSDSUniX's sendfile implementation is that it doesn't
+	// use the current position of the file -- if you pass it offset 0, it starts
+	// from offset 0. There's no way to tell it "start from current position", so
+	// we have to manage that explicitly.
+	pos, err := f.Seek(0, os.SEEK_CUR)
+	if err != nil {
+		return 0, err, false
+	}
+
+	c.wio.Lock()
+	defer c.wio.Unlock()
+	if err := c.incref(false); err != nil {
+		return 0, err, true
+	}
+	defer c.decref()
+
+	dst := c.sysfd
+	src := int(f.Fd())
+	for remain > 0 {
+		n := maxSendfileSize
+		if int64(n) > remain {
+			n = int(remain)
+		}
+		pos1 := pos
+		n, err1 := syscall.Sendfile(dst, src, &pos1, n)
+		if n > 0 {
+			pos += int64(n)
+			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 == syscall.EINTR {
+			continue
+		}
+		if err1 != nil {
+			// This includes syscall.ENOSYS (no kernel
+			// support) and syscall.EINVAL (fd types which
+			// don't implement sendfile together)
+			err = &OpError{"sendfile", c.net, c.raddr, err1}
+			break
+		}
+	}
+	if lr != nil {
+		lr.N = remain
+	}
+	return written, err, written > 0
+}