code review 5128048: net: Set family in newFileFD to fix "unexpected socket ...

src/pkg/net/file_test.go

 // 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 (
         "os"
         "reflect"
         "runtime"
@@ skipping 55 matching lines @@
                 testFileListener(t, "tcp", "[::ffff:127.0.0.1]")
                 testFileListener(t, "tcp", "127.0.0.1")
                 testFileListener(t, "tcp", "[::ffff:127.0.0.1]")
         }
         if syscall.OS == "linux" {
                 testFileListener(t, "unix", "@gotest/net")
                 testFileListener(t, "unixpacket", "@gotest/net")
         }
 }
 
-func testFilePacketConn(t *testing.T, pcf packetConnFile) {
+func testFilePacketConn(t *testing.T, pcf packetConnFile, listen bool) {
         f, err := pcf.File()
         if err != nil {
                 t.Fatalf("File failed: %v", err)
         }
         c, err := FilePacketConn(f)
         if err != nil {
                 t.Fatalf("FilePacketConn failed: %v", err)
         }
         if !reflect.DeepEqual(pcf.LocalAddr(), c.LocalAddr()) {
                 t.Fatalf("LocalAddrs not equal: %#v != %#v", pcf.LocalAddr(), c.LocalAddr())
         }
+        if listen {
+                if _, err := c.WriteTo([]byte{}, c.LocalAddr()); err != nil {
+                        t.Fatalf("WriteTo failed: %v", err)
+                }
+        }
         if err := c.Close(); err != nil {
                 t.Fatalf("Close failed: %v", err)
         }
         if err := f.Close(); err != nil {
                 t.Fatalf("Close failed: %v", err)
         }
 }
 
 func testFilePacketConnListen(t *testing.T, net, laddr string) {
         l, err := ListenPacket(net, laddr)
         if err != nil {
                 t.Fatalf("Listen failed: %v", err)
         }
-        testFilePacketConn(t, l.(packetConnFile))
+        testFilePacketConn(t, l.(packetConnFile), true)
         if err := l.Close(); err != nil {
                 t.Fatalf("Close failed: %v", err)
         }
 }
 
 func testFilePacketConnDial(t *testing.T, net, raddr string) {
         c, err := Dial(net, raddr)
         if err != nil {
                 t.Fatalf("Dial failed: %v", err)
         }
-        testFilePacketConn(t, c.(packetConnFile))
+        testFilePacketConn(t, c.(packetConnFile), false)
         if err := c.Close(); err != nil {
                 t.Fatalf("Close failed: %v", err)
         }
 }
 
 func TestFilePacketConn(t *testing.T) {
         if runtime.GOOS == "windows" || runtime.GOOS == "plan9" {
                 return
         }
         testFilePacketConnListen(t, "udp", "127.0.0.1:0")
         testFilePacketConnDial(t, "udp", "127.0.0.1:12345")
         if supportsIPv6 {
                 testFilePacketConnListen(t, "udp", "[::1]:0")
         }
         if supportsIPv6 && supportsIPv4map {
                 testFilePacketConnDial(t, "udp", "[::ffff:127.0.0.1]:12345")
         }
         if syscall.OS == "linux" {
                 testFilePacketConnListen(t, "unixgram", "@gotest1/net")
         }
 }