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net, syscall: a race condition caused by syscall.SocketDisableIPv6 #7687

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mikioh opened this issue Apr 2, 2014 · 7 comments

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@mikioh
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commented Apr 2, 2014

Sigh, at this point using syscall.SocketDisableIPv6 is completely pointless.

==================
WARNING: DATA RACE
Write by goroutine 408:
  net.TestDialGoogleIPv4()
      /home/mikioh/go/src/pkg/net/dialgoogle_test.go:149 +0x8e8
  testing.tRunner()
      /home/mikioh/go/src/pkg/testing/testing.go:422 +0x10f

Previous read by goroutine 400:
  syscall.Socket()
      /home/mikioh/go/src/pkg/syscall/syscall_unix.go:274 +0x67
  net.sysSocket()
      /home/mikioh/go/src/pkg/net/sys_cloexec.go:19 +0x6b
  net.socket()
      /home/mikioh/go/src/pkg/net/sock_posix.go:40 +0x91
  net.internetSocket()
      /home/mikioh/go/src/pkg/net/ipsock_posix.go:137 +0x189
  net.dialTCP()
      /home/mikioh/go/src/pkg/net/tcpsock_posix.go:155 +0x117
  net.dialSingle()
      /home/mikioh/go/src/pkg/net/dial.go:238 +0x42e
  net.func·020()
      /home/mikioh/go/src/pkg/net/dial.go:200 +0x12e

Goroutine 408 (running) created at:
  testing.RunTests()
      /home/mikioh/go/src/pkg/testing/testing.go:503 +0xb32
  testing.Main()
      /home/mikioh/go/src/pkg/testing/testing.go:435 +0xba
  main.main()
      /var/folders/7d/d3y9vsls2yd880k121jmzcyr0000gn/T/go-build643325068/net/_test/_testmain.go:333 +0xdc

Goroutine 400 (finished) created at:
  net.dialMulti()
      /home/mikioh/go/src/pkg/net/dial.go:210 +0x326
  net.func·019()
      /home/mikioh/go/src/pkg/net/dial.go:168 +0x176
  net.dial()
      /home/mikioh/go/src/pkg/net/fd_unix.go:40 +0x82
  net.(*Dialer).Dial()
      /home/mikioh/go/src/pkg/net/dial.go:171 +0x594
  net.TestDialDualStackLocalhost()
      /home/mikioh/go/src/pkg/net/dial_test.go:546 +0x601
  testing.tRunner()
      /home/mikioh/go/src/pkg/testing/testing.go:422 +0x10f
==================
@dvyukov

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commented Apr 2, 2014

Comment 1:

Labels changed: added threadsanitizer.

@rsc

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commented May 21, 2014

Comment 2:

Labels changed: added release-go1.4.

Status changed to Accepted.

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commented Jun 12, 2014

Comment 3:

CL https://golang.org/cl/108930044 mentions this issue.
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commented Sep 16, 2014

Comment 4:

I don't understand the race here. Presumably TestDialDualStackLocahost runs and
completes before TestDialGoogleIPv4 starts. Why is the read during
TestDialDualStackLocahost not seen as happening before the write in TestDialGoogleIPv4?
Is TestDialDualStackLocahost leaving a background goroutine running that it should not?
@mikioh

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commented Sep 17, 2014

Comment 5:

TestDialDualStackLocahost uses net.Dialer{DualStack: true} so that it tests ipv4-only,
ipv6-only and dual ipv{4,6} cases, and it leaves the looser dial goroutine until the
kernel gives up to attempt 3-way handshaking. Would you prefer to introduce
syscall.Connect cancelleration stuff in go1.5? Though I`m wondering why we still need
syscall.SocketDisableIPv6.
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commented Sep 18, 2014

Comment 6:

We have syscall.SocketDisableIPv6 so that we can test the IPv4 code paths even on
machines that would use IPv6 instead.
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commented Oct 15, 2014

Comment 7:

Too late for changes.

Labels changed: added release-none, removed release-go1.4.

@mikioh mikioh closed this in 21ed40c Apr 3, 2015

@mikioh mikioh added this to the Go1.5 milestone Apr 5, 2015

@golang golang locked and limited conversation to collaborators Jun 25, 2016

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