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Subject: Re: [PATCH 0/5] virtio/vsock: introduce SOCK_SEQPACKET support.
To:     Arseny Krasnov <arseny.krasnov@kaspersky.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Colin Ian King <colin.king@canonical.com>,
        Jorgen Hansen <jhansen@vmware.com>,
        Arseniy Krasnov <oxffffaa@gmail.com>,
        Andra Paraschiv <andraprs@amazon.com>,
        Jeff Vander Stoep <jeffv@google.com>
Cc:     kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210103195454.1954169-1-arseny.krasnov@kaspersky.com>
From:   stsp <stsp2@yandex.ru>
Message-ID: <b93e36c7-fd0b-6c5c-f598-234520b9fe01@yandex.ru>
Date:   Mon, 4 Jan 2021 00:18:44 +0300
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Hi Arseny, thanks for your work on this!

I did a small review in a hope it helps.
Also it may be cool to have the driver feature
for that (so that the host can see if its supported).
But I guess this was already said by Michael. :)

03.01.2021 22:54, Arseny Krasnov пишет:
> 	As SOCK_SEQPACKET guarantees to save record boundaries, so to
> do it, new packet operation was added: it marks start of record (with
> record length in header). To send record, packet with start marker is
> sent first, then all data is transmitted as 'RW' packets. On receiver's
> side, length of record is known from packet with start record marker.
> Now as  packets of one socket are not reordered neither on vsock nor on
> vhost transport layers, these marker allows to restore original record
> on receiver's side. When each 'RW' packet is inserted to rx queue of
> receiver, user is woken up, data is copied to user's buffer and credit
> update message is sent. If there is no user waiting for data, credit
> won't be updated and sender will wait. Also,  if user's buffer is full,
> and record is bigger, all unneeded data will be dropped (with sending of
> credit update message).
> 	'MSG_EOR' flag is implemented with special value of 'flags' field
> in packet header. When record is received with such flags, 'MSG_EOR' is
> set in 'recvmsg()' flags. 'MSG_TRUNC' flag is also supported.
> 	In this implementation maximum length of datagram is not limited
> as in stream socket.
>
>   drivers/vhost/vsock.c                   |   6 +-
>   include/linux/virtio_vsock.h            |   7 +
>   include/net/af_vsock.h                  |   4 +
>   include/uapi/linux/virtio_vsock.h       |   9 +
>   net/vmw_vsock/af_vsock.c                | 457 +++++++++++++++++++-----
>   net/vmw_vsock/virtio_transport.c        |   3 +
>   net/vmw_vsock/virtio_transport_common.c | 323 ++++++++++++++---
>   7 files changed, 673 insertions(+), 136 deletions(-)
>