Re: [RFC PATCH v8 00/19] virtio/vsock: introduce SOCK_SEQPACKET support

[Stefano Garzarella]

On Wed, Apr 21, 2021 at 06:06:28PM +0300, Arseny Krasnov wrote:
> On 21.04.2021 12:52, Stefano Garzarella wrote:
> > On Tue, Apr 13, 2021 at 03:39:51PM +0300, Arseny Krasnov wrote:
> > > v7 -> v8:
> > > General changelog:
> > > - whole idea is simplified: channel now considered reliable,
> > >   so SEQ_BEGIN, SEQ_END, 'msg_len' and 'msg_id' were removed.
> > >   Only thing that is used to mark end of message is bit in
> > >   'flags' field of packet header: VIRTIO_VSOCK_SEQ_EOR. Packet
> > >   with such bit set to 1 means, that this is last packet of
> > >   message.
> > >
> > > - POSIX MSG_EOR support is removed, as there is no exact
> > >   description how it works.
> > It would be nice to support it, I'll try to see if I can find anything.
> >
> > I just reviewed the series. I think the most important things to fix are
> > the `seqpacket_allow` stored in the struct virtio_transport that is
> > wrong IMHO, and use cpu_to_le32()/le32_to_cpu() to access the flags.
>
> Thank You, i'll prepare next version. Main question is: does this
> approach(no SEQ_BEGIN, SEQ_END, 'msg_len' and 'msg_id') considered
> good? In this case it will be easier to prepare final version, because 
> is smaller and more simple than previous logic. Also patch to spec
> will be smaller.

Yes, it's definitely much better than before.

The only problem I see is that we add some overhead per fragment 
(header). We could solve that with the mergeable buffers that Jiang is 
considering for DGRAM.

If we have that support, I think we could reuse it here as well, but it 
might be a next step.

Thanks,
Stefano