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

[Stefan Hajnoczi <stefanha@gmail.com>]

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