Re: [MASSMAIL KLMS] [virtio-comment] Re: [RFC PATCH v1] virtio-vsock: use enums instead of hardcoded constants

[Stefano Garzarella <sgarzare@redhat.com>]

On Tue, Mar 16, 2021 at 06:35:11AM +0300, Arseny Krasnov wrote:
> On 15.03.2021 18:53, Cornelia Huck wrote:
> > On Mon, 15 Mar 2021 11:35:41 +0300
> > Arseny Krasnov <arseny.krasnov@kaspersky.com> wrote:
> >
> > > This replaces constants defined in "bit X set to Y" manner
> > > with enums from Linux kernel uapi headers.
> > > ---
> > >  virtio-vsock.tex | 29 ++++++++++++++++++++++-------
> > >  1 file changed, 22 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/virtio-vsock.tex b/virtio-vsock.tex
> > > index da7e641..a97a81e 100644
> > > --- a/virtio-vsock.tex
> > > +++ b/virtio-vsock.tex
> > > @@ -140,8 +140,14 @@ \subsubsection{Addressing}\label{sec:Device Types / Socket Device / Device Opera
> > >  consists of a (cid, port number) tuple. The header fields used for this are
> > >  \field{src_cid}, \field{src_port}, \field{dst_cid}, and \field{dst_port}.
> > >
> > > -Currently only stream sockets are supported. \field{type} is 1 for stream
> > > -socket types.
> > > +Currently only stream sockets are supported. \field{type} is one of the
> > > +following constants:
> > > +
> > > +\begin{lstlisting}
> > > +enum virtio_vsock_type {
> > > +	VIRTIO_VSOCK_TYPE_STREAM = 1,
> > > +};
> > > +\end{lstlisting}
> > >
> > >  Stream sockets provide in-order, guaranteed, connection-oriented delivery
> > >  without message boundaries.
> > > @@ -221,11 +227,20 @@ \subsubsection{Stream Sockets}\label{sec:Device Types / Socket Device / Device O
> > >  a listening socket does not exist on the destination or the destination has
> > >  insufficient resources to establish the connection.
> > >
> > > -When a connected socket receives VIRTIO_VSOCK_OP_SHUTDOWN the header
> > > -\field{flags} field bit 0 indicates that the peer will not receive any more
> > > -data and bit 1 indicates that the peer will not send any more data.  These
> > > -hints are permanent once sent and successive packets with bits clear do not
> > > -reset them.
> > > +When a connected socket receives VIRTIO_VSOCK_OP_SHUTDOWN, header \field{flags}
> > > +field is one of the following constants:
> > I don't think these two are required to be mutually exclusive (i.e.
> > both can be indicated at the same time?)
>
> I'm not sure, in Linux driver there are several cases when these constants are used
>
> independently from each over, but I think, this is question to implementation of virtio
>
> vsock protocol, while this patch is cosmetic for specification.

I think Cornelia's point is that from the "is one of the following 
constants" sentence it looks like only one of these flags can be set.
Instead both of them could be set together, and I guess this is the most 
frequent use case.

Thanks,
Stefano

> > > +
> > > +\begin{lstlisting}
> > > +enum virtio_vsock_shutdown {
> > > +	VIRTIO_VSOCK_SHUTDOWN_RCV = 1,
> > > +	VIRTIO_VSOCK_SHUTDOWN_SEND = 2,
> > > +};
> > > +\end{lstlisting}
> > > +
> > > +VIRTIO_VSOCK_SHUTDOWN_RCV indicates that the peer will not receive any more
> > > +data and VIRTIO_VSOCK_SHUTDOWN_SEND indicates that the peer will not send
> > > +any more data.  These hints are permanent once sent and successive packets
> > > +with bits clear do not reset them.
> > >
> > >  The VIRTIO_VSOCK_OP_RST packet aborts the connection process or forcibly
> > >  disconnects a connected socket.
> >
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