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Re: [Qemu-devel] [PATCH 4/4] chardev: clear O_NONBLOCK on SCM_RIGHTS fil
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH 4/4] chardev: clear O_NONBLOCK on SCM_RIGHTS file descriptors |
Date: |
Tue, 26 Mar 2013 10:40:41 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 |
On 03/26/2013 10:07 AM, Stefan Hajnoczi wrote:
> When we receive a file descriptor over a UNIX domain socket the
> O_NONBLOCK flag is preserved. Clear the O_NONBLOCK flag and rely on
> QEMU file descriptor users like migration, SPICE, VNC, block layer, and
> others to set non-blocking only when necessary.
>
> This change ensures we don't accidentally expose O_NONBLOCK in the QMP
> API. QMP clients should not need to get the non-blocking state
> "correct".
>
> A recent real-world example was when libvirt passed a non-blocking TCP
> socket for migration where we expected a blocking socket. The source
> QEMU produced a corrupted migration stream since its code did not cope
> with non-blocking sockets.
>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
> qemu-char.c | 3 +++
> 1 file changed, 3 insertions(+)
Reviewed-by: Eric Blake <address@hidden>
Covers both 'getfd' and 'add-fd' paths.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [PATCH 0/4] monitor: do not rely on O_NONBLOCK for passed file descriptors, Stefan Hajnoczi, 2013/03/26
- [Qemu-devel] [PATCH 2/4] qemu-socket: set passed fd non-blocking in socket_connect(), Stefan Hajnoczi, 2013/03/26
- [Qemu-devel] [PATCH 4/4] chardev: clear O_NONBLOCK on SCM_RIGHTS file descriptors, Stefan Hajnoczi, 2013/03/26
- [Qemu-devel] [PATCH 1/4] net: ensure "socket" backend uses non-blocking fds, Stefan Hajnoczi, 2013/03/26
- [Qemu-devel] [PATCH 3/4] oslib-posix: rename socket_set_nonblock() to qemu_set_nonblock(), Stefan Hajnoczi, 2013/03/26
- Re: [Qemu-devel] [PATCH 0/4] monitor: do not rely on O_NONBLOCK for passed file descriptors, liu ping fan, 2013/03/27