[Qemu-devel] [Bug 1795100] Re: unix-domain socket unlink()ed prematurely

[LukeShu <lukeshu@lukeshu.com>]

This is still a problem with 3.1.0.

** Summary changed:

- unix-domain socket unlink()ed prematurely
+ VNC unix-domain socket unlink()ed prematurely

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https://bugs.launchpad.net/bugs/1795100

Title:
  VNC unix-domain socket unlink()ed prematurely

Status in QEMU:
  New

Bug description:
  With qemu 3.0.0 (I don't believe this happened with previous
  versions), if I tell it `-vnc unix:/path/to/vnc.sock`, qemu will
  unlink() that file when the first client disconnects, meaning that
  once I disconnect, I can't ever reconnect without restarting the VM.

  A stupid testcase demonstrating the issue:

  In terminal A:

      $ qemu-system-x86_64 -vnc unix:$PWD/vnc.sock

  In terminal B:

      $ ls vnc.sock
      vnc.sock
      $ socat STDIO UNIX-CONNECT:vnc.sock <<<''
      RFB 003.008
      $ ls vnc.sock
      ls: cannot access 'vnc.sock': No such file or directory

  I have determined that the offending unlink() call is the one in
  io/channel-socket.c:qio_channel_socket_close().  That call was first
  introduced in commit d66f78e1eaa832f73c771d9df1b606fe75d52a50, which
  first appeared in version 3.0.0.

  This type of premature unlink() does not happen on monitor.sock with
  `-monitor unix:/path/to/monitor.sock,server,nowait`.

  I am not familiar enough with the QIO subsystem to suggest a fix that
  fixes VNC, but preserves the QMP fix targeted in the offending commit.

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