Re: [Qemu-devel] [PATCH v2 0/5] Do not set SO_REUSEADDR on Windows

[Sebastian Ottlik <ottlik@fzi.de>]

On 09.09.2013 14:05, Stefan Hajnoczi wrote:
> On Thu, Sep 05, 2013 at 03:48:16PM +0200, Sebastian Ottlik wrote:
>> On 04.09.2013 19:08, Sebastian Ottlik wrote:
>>> This patchset disabels all use of SO_REUSEADDR on Windows. On Windows systems
>>> the default behaviour is equivalent to SO_REUSEADDR on other operating
>>> systems. SO_REUSEADDR can still be set but results in undesired behaviour
>>> instead. It may even lead to situations were system behaviour is
>>> unspecified. More information on this can be found at:
>>> http://msdn.microsoft.com/en-us/library/windows/desktop/ms740621.aspx
>>>
>>> I originally encountered this issue when accidentally launching two QEMU
>>> instances with identical GDB ports at the same time. In which case QEMU won't
>>> fail as one might expect.
>>>
>>> v2 Changes:
>>>
>>> - Introduce a function with os specific implementation instead of using #ifdef
>>>    I named it socket_set_fast_reuse instead of the suggested qemu_set_reuseaddr
>>>    so the name better reflects what the function actually does.
>>>
>>>   gdbstub.c              |    6 ++----
>>>   include/qemu/sockets.h |    1 +
>>>   net/socket.c           |   19 +++++++------------
>>>   slirp/misc.c           |    3 +--
>>>   slirp/socket.c         |    4 +---
>>>   slirp/tcp_subr.c       |    6 ++----
>>>   slirp/udp.c            |    4 ++--
>>>   util/oslib-posix.c     |   14 ++++++++++++++
>>>   util/oslib-win32.c     |   10 ++++++++++
>>>   util/qemu-sockets.c    |    6 +++---
>>>   10 files changed, 43 insertions(+), 30 deletions(-)
>>>
>>>
>>> util: add socket_set_fast_reuse function
>>> gdbstub: call socket_set_fast_reuse instead of setting SO_REUSEADDR
>>> net: call socket_set_fast_reuse instead of setting SO_REUSEADDR
>>> slirp: call socket_set_fast_reuse instead of setting SO_REUSEADDR
>>> util: call socket_set_fast_reuse instead of setting SO_REUSEADDR
>>>
>> Pinging this patch, as I think it is still an appropriate approach
>> to the issue:
>>
>> I did some research and apparently there is a valid use case for
>> SO_REUSEADDR
>> on windows when multiple clients need to listen to the same port for
>> the same
>> multicast group. IMHO making qemu_setsockopt ignore SO_REUSEADDR on windows
>> might be confusing for some use cases. Actually net_socket_mcast_create in
>> net/socket.c should probably set SO_REUSEADDR on windows. This is
>> also an issue
>> with patch 3 I supplied that I will address in a new version of this
>> patch set if there is
>> an agreement on a general approach.
> Sounds like a good idea.  The patch series overall looks good.
>
> Stefan
Thanks for the feedback. I will resubmit the patch series including the 
change for net_socket_mcast_create and fixes for the style issues you 
pointed out soon.

When I submitted this new version of the patch set I think I was a 
little early as there was still some discussion in the thread of the 
original version. In general, what is a good period to wait before 
submitting a new version?

Best Regards,
   Sebastian