On Mon, Feb 05, 2018 at 01:42:50PM -0600, Eric Blake wrote: > On 02/05/2018 09:24 AM, Daniel P. Berrangé wrote: > > From: "Daniel P. Berrange" <[email protected]> > > > > The SocketAddress 'fd' kind accepts the name of a file descriptor passed > > to the monitor with the 'getfd' command. This makes it impossible to use > > the 'fd' kind in cases where a monitor is not available. This can apply in > > handling command line argv at startup, or simply if internal code wants to > > use SocketAddress and pass a numeric FD it has acquired from elsewhere. > > > > Fortunately the 'getfd' command mandated that the FD names must not start > > with a leading digit. We can thus safely extend semantics of the > > SocketAddress 'fd' kind, to allow a purely numeric name to reference an > > file descriptor that QEMU already has open. There will be restrictions on > > when each kind can be used. > > > > In codepaths where we are handling a monitor command (ie cur_mon != NULL), > > we will only support use of named file descriptors as before. Use of FD > > numbers is still not permitted for monitor commands. > > > > In codepaths where we are not handling a monitor command (ie cur_mon == > > NULL), we will not support named file descriptors. Instead we can reference > > FD numers explicitly. This allows the app spawning QEMU to intentionally > > "leak" a pre-opened socket to QEMU and reference that in a SocketAddress > > definition, or for code inside QEMU to pass pre-opened FDs around. > > > > Reviewed-by: Marc-André Lureau <[email protected]> > > Signed-off-by: Daniel P. Berrange <[email protected]> > > --- > > qapi/sockets.json | 7 +++ > > tests/test-util-sockets.c | 112 > > +++++++++++++++++++++++++++++++++++++++++++--- > > util/qemu-sockets.c | 16 +++++-- > > 3 files changed, 126 insertions(+), 9 deletions(-) > > > > diff --git a/qapi/sockets.json b/qapi/sockets.json > > index ac022c6ad0..fc81d8d5e8 100644 > > --- a/qapi/sockets.json > > +++ b/qapi/sockets.json > > @@ -123,6 +123,13 @@ > > # > > # @unix: Unix domain socket > > # > > +# @vsock: VMCI address > > +# > > +# @fd: decimal is for file descriptor number, otherwise a file descriptor > > name. > > +# Named file descriptors are permitted in monitor commands, in > > combination > > +# with the 'getfd' command. Decimal file descriptors are permitted at > > +# startup or other contexts where no monitor context is active. > > +# > > # Since: 2.9 > > There doesn't seem to be any way to introspect if we support decimal fds > from the command line; is that going to be a problem?
Libvirt needs to know when it can use it, so any suggestions ? Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
