From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53537) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VHZv8-0004ve-A4 for qemu-devel@nongnu.org; Thu, 05 Sep 2013 09:48:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VHZv1-0001CT-0p for qemu-devel@nongnu.org; Thu, 05 Sep 2013 09:48:26 -0400 Received: from ex-e-2.perimeter.fzi.de ([141.21.8.251]:36659) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VHZv0-0001CL-NA for qemu-devel@nongnu.org; Thu, 05 Sep 2013 09:48:18 -0400 Message-ID: <52288BA0.6060508@fzi.de> Date: Thu, 5 Sep 2013 15:48:16 +0200 From: Sebastian Ottlik MIME-Version: 1.0 References: <1378314535-27587-1-git-send-email-ottlik@fzi.de> In-Reply-To: <1378314535-27587-1-git-send-email-ottlik@fzi.de> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 0/5] Do not set SO_REUSEADDR on Windows List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Peter Maydell , Anthony Liguori , Jan Kiszka , Michael Tokarev , Stefan Hajnoczi , Stefan Weil , Paolo Bonzini 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. It was also suggested to introduce a qemu_stream_listen_socket, but I do not see a clear advantage of this approach over the one taken in my patches. To my understanding there also may be situations where one would like to enable fast reuse of client sockets (i.e. those used with connect()). Best Regards, Sebastian