Re: [virtio-comment] [RFC PATCH v1 1/1] virtio-vsock: add SOCK_SEQPACKET description

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 24 Feb 2021 10:32:00 +0100
Stefano Garzarella <sgarzare@redhat.com> wrote:

> On Thu, Feb 18, 2021 at 09:08:23AM +0300, Arseny Krasnov wrote:
> >Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
> >---
> > virtio-vsock.tex | 40 +++++++++++++++++++++++++++++++++++++---
> > 1 file changed, 37 insertions(+), 3 deletions(-)
> >
> >diff --git a/virtio-vsock.tex b/virtio-vsock.tex
> >index da7e641..1ee8f99 100644
> >--- a/virtio-vsock.tex
> >+++ b/virtio-vsock.tex
> >@@ -102,6 +102,11 @@ \subsection{Device Operation}\label{sec:Device Types / Socket Device / Device Op
> > 	VIRTIO_VSOCK_OP_CREDIT_UPDATE = 6,
> > 	/* Request the peer to send the credit info to us */
> > 	VIRTIO_VSOCK_OP_CREDIT_REQUEST = 7,
> >+
> >+	/* Message begin for SOCK_SEQPACKET */
> >+	VIRTIO_VSOCK_OP_SEQ_BEGIN = 8,
> >+	/* Message end for SOCK_SEQPACKET */
> >+	VIRTIO_VSOCK_OP_SEQ_END = 9,
> > };
> > \end{lstlisting}
> >
> >@@ -140,11 +145,11 @@ \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 stream and seqpacket sockets are supported. \field{type} is 1 for
> >+stream socket types. \field{type} is 2 for seqpacket socket types.
> >
> > Stream sockets provide in-order, guaranteed, connection-oriented delivery
> >-without message boundaries.
> >+without message boundaries. Seqpacket sockets also provide message boundaries.
> >
> > \subsubsection{Buffer Space Management}\label{sec:Device Types / Socket Device / Device Operation / Buffer Space Management}
> > \field{buf_alloc} and \field{fwd_cnt} are used for buffer space management of
> >@@ -240,6 +245,35 @@ \subsubsection{Stream Sockets}\label{sec:Device Types / Socket Device / Device O
> > destination) address tuple for a new connection while the other peer is still
> > processing the old connection.
> >
> >+\subsubsection{Seqpacket Sockets}\label{sec:Device Types / Socket Device / Device Operation / Seqpacket Sockets}
> >+
> >+Seqpacket sockets differ from stream sockets only in data transmission way: in
> >+stream sockets all data is sent using only VIRTIO_VSOCK_OP_RW packets. In
> >+seqpacket sockets, to provide message boundaries, every sequence of
> >+VIRTIO_VSOCK_OP_RW packets of each message is headed with  
>                                               ^
> Since this is a spec, I think we should use MUST when something must be 
> respected by the peer, for example here we can say "MUST be headed"
> 
> >+VIRTIO_VSOCK_OP_SEQ_BEGIN and tailed with VIRTIO_VSOCK_OP_SEQ_END packets.
> >+Both VIRTIO_VSOCK_OP_SEQ_BEGIN and VIRTIO_VSOCK_OP_SEQ_END packets carry  
>                                                                       ^
> Same here "MUST carry" and in the rest of the patch.

Actually, MUST and friends are really for normative sections; I'd
advise to have a description of how this feature works and then some
device/driver normative clauses with MUST statements (like "the device
MUST reject <malformed packets>" or so).