netdev - Re: [MASSMAIL KLMS] Re: [MASSMAIL KLMS] Re: [RFC PATCH v1 0/7] virtio/vsock: introduce MSG

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Date:   Tue, 27 Jul 2021 15:35:06 +0300
From:   Arseny Krasnov <arseny.krasnov@...persky.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
CC:     Stefan Hajnoczi <stefanha@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Colin Ian King <colin.king@...onical.com>,
        Andra Paraschiv <andraprs@...zon.com>,
        Norbert Slusarek <nslusarek@....net>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "oxffffaa@...il.com" <oxffffaa@...il.com>
Subject: Re: [MASSMAIL KLMS] Re: [MASSMAIL KLMS] Re: [RFC PATCH v1 0/7]
 virtio/vsock: introduce MSG_EOR flag for SEQPACKET


On 27.07.2021 12:58, Stefano Garzarella wrote:
> Caution: This is an external email. Be cautious while opening links or attachments.
>
>
>
> On Tue, Jul 27, 2021 at 12:34:36PM +0300, Arseny Krasnov wrote:
>> On 27.07.2021 10:59, Stefano Garzarella wrote:
>>> Caution: This is an external email. Be cautious while opening links or attachments.
>>>
>>>
>>>
>>> On Mon, Jul 26, 2021 at 07:31:33PM +0300, Arseny Krasnov wrote:
>>>>       This patchset implements support of MSG_EOR bit for SEQPACKET
>>>> AF_VSOCK sockets over virtio transport.
>>>>       Idea is to distinguish concepts of 'messages' and 'records'.
>>>> 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.
>>>>       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.
>>> At this point it's probably better to rename the old flag, so we stay
>>> compatible.
>>>
>>> What happens if one of the two peers does not support MSG_EOR handling,
>>> while the other does?
>>>
>>> I'll do a closer review in the next few days.
>> Thank You, also i think MSG_EOR support must be described in spec
> Yep, sure!
>
> What do you think about the concerns above?
I think you are right, i'll rename EOR -> EOM, and EOR will be added by patch
>
> Stefano
>
>