libgo/go/net/write_unix_test.go

   1 // Copyright 2017 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // +build darwin dragonfly freebsd linux netbsd openbsd solaris
   6
   7 package net
   8
   9 import (
  10         "bytes"
  11         "syscall"
  12         "testing"
  13         "time"
  14 )
  15
  16 // Test that a client can't trigger an endless loop of write system
  17 // calls on the server by shutting down the write side on the client.
  18 // Possibility raised in the discussion of https://golang.org/cl/71973.
  19 func TestEndlessWrite(t *testing.T) {
  20         t.Parallel()
  21         c := make(chan bool)
  22         server := func(cs *TCPConn) error {
  23                 cs.CloseWrite()
  24                 <-c
  25                 return nil
  26         }
  27         client := func(ss *TCPConn) error {
  28                 // Tell the server to return when we return.
  29                 defer close(c)
  30
  31                 // Loop writing to the server. The server is not reading
  32                 // anything, so this will eventually block, and then time out.
  33                 b := bytes.Repeat([]byte{'a'}, 8192)
  34                 cagain := 0
  35                 for {
  36                         n, err := ss.conn.fd.pfd.WriteOnce(b)
  37                         if n > 0 {
  38                                 cagain = 0
  39                         }
  40                         switch err {
  41                         case nil:
  42                         case syscall.EAGAIN:
  43                                 if cagain == 0 {
  44                                         // We've written enough data to
  45                                         // start blocking. Set a deadline
  46                                         // so that we will stop.
  47                                         ss.SetWriteDeadline(time.Now().Add(5 * time.Millisecond))
  48                                 }
  49                                 cagain++
  50                                 if cagain > 20 {
  51                                         t.Error("looping on EAGAIN")
  52                                         return nil
  53                                 }
  54                                 if err = ss.conn.fd.pfd.WaitWrite(); err != nil {
  55                                         t.Logf("client WaitWrite: %v", err)
  56                                         return nil
  57                                 }
  58                         default:
  59                                 // We expect to eventually get an error.
  60                                 t.Logf("client WriteOnce: %v", err)
  61                                 return nil
  62                         }
  63                 }
  64         }
  65         withTCPConnPair(t, client, server)
  66 }