On Mon, Aug 16, 2021 at 11:56:13AM +0300, Arseny Krasnov wrote:
This adds description of SOCK_SEQPACKET socket type
support for virtio-vsock.
Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
---
virtio-vsock.tex | 43 ++++++++++++++++++++++++++++++++++++++-----
1 file changed, 38 insertions(+), 5 deletions(-)
diff --git a/virtio-vsock.tex b/virtio-vsock.tex
index ad57f9d..51d785a 100644
--- a/virtio-vsock.tex
+++ b/virtio-vsock.tex
@@ -16,7 +16,10 @@ \subsection{Virtqueues}\label{sec:Device Types / Socket Device / Virtqueues}
\subsection{Feature bits}\label{sec:Device Types / Socket Device / Feature bits}
-There are currently no feature bits defined for this device.
+\begin{description}
+\item VIRTIO_VSOCK_F_SEQPACKET (1) SOCK_SEQPACKET socket type is
+ supported.
+\end{description}
\subsection{Device configuration layout}\label{sec:Device Types / Socket Device / Device configuration layout}
@@ -135,15 +138,17 @@ \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 (VIRTIO_VSOCK_TYPE_STREAM)
-for stream socket types.
+Currently stream and seqpacket sockets are supported. \field{type} is 1 (VIRTIO_VSOCK_TYPE_STREAM)
+for stream socket types, and 2 (VIRTIO_VSOCK_TYPE_SEQPACKET) for seqpacket socket types.
\begin{lstlisting}
-#define VIRTIO_VSOCK_TYPE_STREAM 1
+#define VIRTIO_VSOCK_TYPE_STREAM 1
+#define VIRTIO_VSOCK_TYPE_SEQPACKET 2
\end{lstlisting}
Stream sockets provide in-order, guaranteed, connection-oriented delivery
-without message boundaries.
+without message boundaries. Seqpacket sockets provide in-order,
guaranteed,
+connection-oriented delivery with message and record 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
@@ -244,6 +249,34 @@ \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}
+
+\paragraph{Message and record boundaries}\label{sec:Device Types / Socket Device / Device Operation / Seqpacket Sockets / Boundaries}
+Two types of boundaries supported: message and record boundaries.
+
+Message is data, sent by single system call. Message boundary means
^
Could be "A message contains data sent by a single system call"
+that data of single send system call is guaranteed to be read wholly by single
+receive system call. If receive buffer is not enough, then out of size data
+will be dropped.
+
+Record is any number of subsequent messages, where last message is sent with POSIX
+MSG_EOR flag set. Record boundary means that receiver gets MSG_EOR flag set
+in the corresponding message where sender set it.
+
+To provide message boundaries, last RW packet of each message has VIRTIO_VSOCK_SEQ_EOM
+bit (bit 0) set in the \field{flags} of packet's header.
+
+\begin{lstlisting}
+#define VIRTIO_VSOCK_SEQ_EOM 1
+\end{lstlisting}
+
+To provide record boundaries, last RW packet of each record has VIRTIO_VSOCK_SEQ_EOR
+bit (bit 1) set in the \field{flags} of packet's header.
+
+\begin{lstlisting}
+#define VIRTIO_VSOCK_SEQ_EOR 2
+\end{lstlisting}
+
For other flags in the specs we use the shift operator, which is
actually clearer to understand which bit is set, so I guess we could use
it here too:
#define VIRTIO_VSOCK_SEQ_EOM (1 << 0)
#define VIRTIO_VSOCK_SEQ_EOR (1 << 1)
The rest LGTM.
Thanks,
Stefano
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