netdev - Re: [PATCH net-next v5 0/6] virtio/vsock: introduce MSG

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Date:   Fri, 3 Sep 2021 15:17:31 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Arseny Krasnov <arseny.krasnov@...persky.com>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Colin Ian King <colin.king@...onical.com>,
        Norbert Slusarek <nslusarek@....net>,
        Andra Paraschiv <andraprs@...zon.com>, <kvm@...r.kernel.org>,
        <virtualization@...ts.linux-foundation.org>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <stsp2@...dex.ru>, <oxffffaa@...il.com>
Subject: Re: [PATCH net-next v5 0/6] virtio/vsock: introduce MSG_EOR flag
 for SEQPACKET

On Fri, 3 Sep 2021 15:30:13 +0300 Arseny Krasnov wrote:
> 	This patchset implements support of MSG_EOR bit for SEQPACKET
> AF_VSOCK sockets over virtio transport.
> 	First we need to define 'messages' and 'records' like this:
> Message is result of sending calls: 'write()', 'send()', 'sendmsg()'
> etc. It has fixed maximum length, and it bounds are visible using
> return from receive calls: 'read()', 'recv()', 'recvmsg()' etc.
> Current implementation based on message definition above.
> 	Record has unlimited length, it consists of multiple message,
> and bounds of record are visible via MSG_EOR flag returned from
> 'recvmsg()' call. Sender passes MSG_EOR to sending system call and
> receiver will see MSG_EOR when corresponding message will be processed.
> 	Idea of patchset comes from POSIX: it says that SEQPACKET
> supports record boundaries which are visible for receiver using
> MSG_EOR bit. So, it looks like MSG_EOR is enough thing for SEQPACKET
> and we don't need to maintain boundaries of corresponding send -
> receive system calls. But, for 'sendXXX()' and 'recXXX()' POSIX says,
> that all these calls operates with messages, e.g. 'sendXXX()' sends
> message, while 'recXXX()' reads messages and for SEQPACKET, 'recXXX()'
> must read one entire message from socket, dropping all out of size
> bytes. Thus, both message boundaries and MSG_EOR bit must be supported
> to follow POSIX rules.
> 	To support MSG_EOR new bit was added along with existing
> 'VIRTIO_VSOCK_SEQ_EOR': 'VIRTIO_VSOCK_SEQ_EOM'(end-of-message) - now it
> works in the same way as 'VIRTIO_VSOCK_SEQ_EOR'. But 'VIRTIO_VSOCK_SEQ_EOR'
> is used to mark 'MSG_EOR' bit passed from userspace.
> 	This patchset includes simple test for MSG_EOR.

Assuming you want this merged to net-next:


# Form letter - net-next is closed

We have already sent the networking pull request for 5.15 
and therefore net-next is closed for new drivers, features, 
code refactoring and optimizations. We are currently accepting 
bug fixes only.

Please repost when net-next reopens after 5.15-rc1 is cut.

Look out for the announcement on the mailing list or check:
http://vger.kernel.org/~davem/net-next.html

RFC patches sent for review only are obviously welcome at any time.