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SubjectRe: [RFC PATCH v4 00/17] virtio/vsock: introduce SOCK_SEQPACKET support
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On 11.02.2021 17:57, Stefano Garzarella wrote:
> Hi Arseny,
>
> On Mon, Feb 08, 2021 at 09:32:59AM +0300, Arseny Krasnov wrote:
>> On 07.02.2021 19:20, Michael S. Tsirkin wrote:
>>> On Sun, Feb 07, 2021 at 06:12:56PM +0300, Arseny Krasnov wrote:
>>>> This patchset impelements support of SOCK_SEQPACKET for virtio
>>>> transport.
>>>> As SOCK_SEQPACKET guarantees to save record boundaries, so to
>>>> do it, two new packet operations were added: first for start of record
>>>> and second to mark end of record(SEQ_BEGIN and SEQ_END later). Also,
>>>> both operations carries metadata - to maintain boundaries and payload
>>>> integrity. Metadata is introduced by adding special header with two
>>>> fields - message count and message length:
>>>>
>>>> struct virtio_vsock_seq_hdr {
>>>> __le32 msg_cnt;
>>>> __le32 msg_len;
>>>> } __attribute__((packed));
>>>>
>>>> This header is transmitted as payload of SEQ_BEGIN and SEQ_END
>>>> packets(buffer of second virtio descriptor in chain) in the same way as
>>>> data transmitted in RW packets. Payload was chosen as buffer for this
>>>> header to avoid touching first virtio buffer which carries header of
>>>> packet, because someone could check that size of this buffer is equal
>>>> to size of packet header. To send record, packet with start marker is
>>>> sent first(it's header contains length of record and counter), then
>>>> counter is incremented and all data is sent as usual 'RW' packets and
>>>> finally SEQ_END is sent(it also carries counter of message, which is
>>>> counter of SEQ_BEGIN + 1), also after sedning SEQ_END counter is
>>>> incremented again. On receiver's side, length of record is known from
>>>> packet with start record marker. To check that no packets were dropped
>>>> by transport, counters of two sequential SEQ_BEGIN and SEQ_END are
>>>> checked(counter of SEQ_END must be bigger that counter of SEQ_BEGIN by
>>>> 1) and length of data between two markers is compared to length in
>>>> SEQ_BEGIN header.
>>>> Now as packets of one socket are not reordered neither on
>>>> vsock nor on vhost transport layers, such markers allows to restore
>>>> original record on receiver's side. If user's buffer is smaller that
>>>> record length, when all out of size data is dropped.
>>>> Maximum length of datagram is not limited as in stream socket,
>>>> because same credit logic is used. Difference with stream socket is
>>>> that user is not woken up until whole record is received or error
>>>> occurred. Implementation also supports 'MSG_EOR' and 'MSG_TRUNC' flags.
>>>> Tests also implemented.
>>>>
>>>> Arseny Krasnov (17):
>>>> af_vsock: update functions for connectible socket
>>>> af_vsock: separate wait data loop
>>>> af_vsock: separate receive data loop
>>>> af_vsock: implement SEQPACKET receive loop
>>>> af_vsock: separate wait space loop
>>>> af_vsock: implement send logic for SEQPACKET
>>>> af_vsock: rest of SEQPACKET support
>>>> af_vsock: update comments for stream sockets
>>>> virtio/vsock: dequeue callback for SOCK_SEQPACKET
>>>> virtio/vsock: fetch length for SEQPACKET record
>>>> virtio/vsock: add SEQPACKET receive logic
>>>> virtio/vsock: rest of SOCK_SEQPACKET support
>>>> virtio/vsock: setup SEQPACKET ops for transport
>>>> vhost/vsock: setup SEQPACKET ops for transport
>>>> vsock_test: add SOCK_SEQPACKET tests
>>>> loopback/vsock: setup SEQPACKET ops for transport
>>>> virtio/vsock: simplify credit update function API
>>>>
>>>> drivers/vhost/vsock.c | 8 +-
>>>> include/linux/virtio_vsock.h | 15 +
>>>> include/net/af_vsock.h | 9 +
>>>> include/uapi/linux/virtio_vsock.h | 16 +
>>>> net/vmw_vsock/af_vsock.c | 588 +++++++++++++++-------
>>>> net/vmw_vsock/virtio_transport.c | 5 +
>>>> net/vmw_vsock/virtio_transport_common.c | 316 ++++++++++--
>>>> net/vmw_vsock/vsock_loopback.c | 5 +
>>>> tools/testing/vsock/util.c | 32 +-
>>>> tools/testing/vsock/util.h | 3 +
>>>> tools/testing/vsock/vsock_test.c | 126 +++++
>>>> 11 files changed, 895 insertions(+), 228 deletions(-)
>>>>
>>>> TODO:
>>>> - What to do, when server doesn't support SOCK_SEQPACKET. In current
>>>> implementation RST is replied in the same way when listening port
>>>> is not found. I think that current RST is enough,because case when
>>>> server doesn't support SEQ_PACKET is same when listener missed(e.g.
>>>> no listener in both cases).
> I think is fine.
>
>>> - virtio spec patch
>> Ok
> Yes, please prepare a patch to discuss the VIRTIO spec changes.
>
> For example for 'virtio_vsock_seq_hdr', I left a comment about 'msg_cnt'
> naming that should be better to discuss with virtio guys.

Ok, i'll prepare it in v5. So I have to send it both LKML(as one of patches) and

virtio mailing lists? (e.g. virtio-comment@lists.oasis-open.org)

>
> Anyway, I reviewed this series and I left some comments.
> I think we are in a good shape :-)
Great, thanks for review. I'll consider all review comments in next version.
>
> Thanks,
> Stefano
>
>

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