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chardev: clear O_NONBLOCK on SCM_RIGHTS file descriptors

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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 <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2013-03-27 10:10:46 +01:00 committed by Luiz Capitulino
parent 1a751ebfbb
commit 9b938c7262
1 changed files with 3 additions and 0 deletions
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3
qemu-char.c
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@ -2440,6 +2440,9 @@ static void unix_process_msgfd(CharDriverState *chr, struct msghdr *msg)
if (fd < 0)
continue;
/* O_NONBLOCK is preserved across SCM_RIGHTS so reset it */
qemu_set_block(fd);
#ifndef MSG_CMSG_CLOEXEC
qemu_set_cloexec(fd);
#endif