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Subject: Re: [MASSMAIL KLMS] Re: [RFC PATCH v1 0/7] virtio/vsock: introduce
 MSG_EOR flag for SEQPACKET
To:     Stefano Garzarella <sgarzare@redhat.com>
CC:     Stefan Hajnoczi <stefanha@redhat.com>,
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References: <20210726163137.2589102-1-arseny.krasnov@kaspersky.com>
 <20210727075948.yl4w3foqa6rp4obg@steredhat>
From:   Arseny Krasnov <arseny.krasnov@kaspersky.com>
Message-ID: <2df68589-96b9-abd4-ad1c-e25918b908a9@kaspersky.com>
Date:   Tue, 27 Jul 2021 12:34:36 +0300
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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
>
> Thanks,
> Stefano
>
>