On Sat, Jul 29, 2017 at 11:18:15PM +0200, Knut Omang wrote:
> There's a potential race condition between multiple bind()'s
> attempting to bind to the same port, which occasionally
> allows more than one bind to succeed against the same port.
> 
> When a subsequent listen() call is made with the same socket
> only one will succeed.
> 
> The current QEMU code does however not take this situation into account
> and the listen will cause the code to break out and fail even
> when there are actually available ports to use.
> 
> This test exposes two subtests:
> 
> /socket/listen-serial
> /socket/listen-compete
> 
> The "compete" subtest creates a number of threads and have them all trying to 
> bind
> to the same port with a large enough offset input to
> allow all threads to get it's own port.
> The "serial" subtest just does the same, except in series in a
> single thread.
> 
> The serial version passes, probably in most versions of QEMU.
> 
> The parallel version exposes the problem in a relatively reliable way,
> eg. it fails a majority of times, but not with a 100% rate, occasional
> passes can be seen. Nevertheless this is quite good given that
> the bug was tricky to reproduce and has been left undetected for
> a while.
> 
> The problem seems to be present in all versions of QEMU.
> 
> The original failure scenario occurred with VNC port allocation
> in a traditional Xen based build, in different code
> but with similar functionality.
> 
> Reported-by: Bhavesh Davda <bhavesh.da...@oracle.com>
> Signed-off-by: Knut Omang <knut.om...@oracle.com>
> Reviewed-by: Yuval Shaia <yuval.sh...@oracle.com>
> Reviewed-by: Bhavesh Davda <bhavesh.da...@oracle.com>
> Reviewed-by: Girish Moodalbail <girish.moodalb...@oracle.com>
> ---
>  tests/Makefile.include |   2 +-
>  tests/test-listen.c    | 253 ++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 255 insertions(+)
>  create mode 100644 tests/test-listen.c
> 
> diff --git a/tests/Makefile.include b/tests/Makefile.include
> index 7af278d..b37c0c8 100644
> --- a/tests/Makefile.include
> +++ b/tests/Makefile.include
> @@ -128,6 +128,7 @@ check-unit-y += tests/test-bufferiszero$(EXESUF)
>  gcov-files-check-bufferiszero-y = util/bufferiszero.c
>  check-unit-y += tests/test-uuid$(EXESUF)
>  check-unit-y += tests/ptimer-test$(EXESUF)
> +#check-unit-y += tests/test-listen$(EXESUF)
>  gcov-files-ptimer-test-y = hw/core/ptimer.c
>  check-unit-y += tests/test-qapi-util$(EXESUF)
>  gcov-files-test-qapi-util-y = qapi/qapi-util.c
> @@ -769,6 +770,7 @@ tests/test-arm-mptimer$(EXESUF): tests/test-arm-mptimer.o
>  tests/test-qapi-util$(EXESUF): tests/test-qapi-util.o $(test-util-obj-y)
>  tests/numa-test$(EXESUF): tests/numa-test.o
>  tests/vmgenid-test$(EXESUF): tests/vmgenid-test.o tests/boot-sector.o 
> tests/acpi-utils.o
> +tests/test-listen$(EXESUF): tests/test-listen.o $(test-util-obj-y)
>  
>  tests/migration/stress$(EXESUF): tests/migration/stress.o
>       $(call quiet-command, $(LINKPROG) -static -O3 $(PTHREAD_LIB) -o $@ $< 
> ,"LINK","$(TARGET_DIR)$@")
> diff --git a/tests/test-listen.c b/tests/test-listen.c
> new file mode 100644
> index 0000000..5c07537
> --- /dev/null
> +++ b/tests/test-listen.c
> @@ -0,0 +1,253 @@
> +/*
> + * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
> + *    Author: Knut Omang <knut.om...@oracle.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2
> + * as published by the Free Software Foundation.

Can you change that to "version 2 or later" - per the LICENSE file, we don't
accept contributions under "version 2 only" except for 4 specific subdirs:


  "As of July 2013, contributions under version 2 of the GNU General Public
   License (and no later version) are only accepted for the following files
   or directories: bsd-user/, linux-user/, hw/vfio/, hw/xen/xen_pt*."


> + *
> + * Test parallel port listen configuration with
> + * dynamic port allocation
> + */


Regards,
Daniel
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