Re: [virtio-comment] [RFC PATCH v1 1/1] virtio-vsock: add SOCK_SEQPACKET description
From: Stefano Garzarella <sgarzare@redhat.com>
Date: 2021-02-24 09:32:10
Also in:
virtio-comment
On Thu, Feb 18, 2021 at 09:08:23AM +0300, Arseny Krasnov wrote:
quoted hunk
Signed-off-by: Arseny Krasnov <redacted> --- 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 OpVIRTIO_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 Operaconsists 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 Odestination) 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.
+special header in payload:
+
+\begin{lstlisting}
+struct virtio_vsock_seq_hdr {
+ __le32 msg_cnt;
+ __le32 msg_len;
+};
+\end{lstlisting}
+
+\field{msg_cnt} is per socket and incremented by 1 on every send of
+VIRTIO_VSOCK_OP_SEQ_BEGIN or VIRTIO_VSOCK_OP_SEQ_END. \field{msg_len} contains
+message length. This header is used to check integrity of each message: message
+is valid if length of data in VIRTIO_VSOCK_OP_RW packets is equal to
+\field{msg_len} of prepending VIRTIO_VSOCK_OP_SEQ_BEGIN and \field{msg_cnt} of
+VIRTIO_VSOCK_OP_SEQ_END differs from \field{msg_cnt} of
+VIRTIO_VSOCK_OP_SEQ_BEGIN by 1.If we replace msg_cnt with msg_id, I think we should have the same 'msg_id' for VIRTIO_VSOCK_OP_SEQ_BEGIN or VIRTIO_VSOCK_OP_SEQ_END. If you want to use 'msg_cnt' and you increment it between BEGIN and END, we should consider the overflow case.
+
+POSIX MSG_EOR flag is supported by special value of \field{flags} in packet's
+header. If this flag is set for message, then all VIRTIO_VSOCK_OP_RW packets
+of this message have bit 0 is set to 1 in \field{flags}.Maybe we need to define what MSG_EOR means. Thanks, Stefano
+
\subsubsection{Device Events}\label{sec:Device Types / Socket Device / Device Operation / Device Events}
Certain events are communicated by the device to the driver using the event
--
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