Re: [RFC PATCH v6 00/22] virtio/vsock: introduce SOCK_SEQPACKET support

Stefano Garzarella
2021-03-15T11:40:38Z

Hi Arseny,

On Sun, Mar 07, 2021 at 08:57:19PM +0300, Arseny Krasnov wrote:
> This patchset implements 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 id and message length:
>
> struct virtio_vsock_seq_hdr {
> __le32 msg_id;
> __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 carries length of record and id),then all data
>is sent as usual 'RW' packets and finally SEQ_END is sent(it carries
>id of message, which is equal to id of SEQ_BEGIN), also after sending
>SEQ_END id is incremented. On receiver's side,size of record is known
>from packet with start record marker. To check that no packets were
>dropped by transport, 'msg_id's of two sequential SEQ_BEGIN and SEQ_END
>are checked to be equal and length of data between two markers is
>compared to then 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.
>
> Thanks to stsp2@yandex.ru for encouragements and initial design
>recommendations.
>
> Arseny Krasnov (22):
> 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: set packet's type in virtio_transport_send_pkt_info()
> virtio/vsock: simplify credit update function API
> 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: SEQPACKET feature bit
> vhost/vsock: SEQPACKET feature bit support
> virtio/vsock: SEQPACKET feature bit support
> virtio/vsock: setup SEQPACKET ops for transport
> vhost/vsock: setup SEQPACKET ops for transport
> vsock/loopback: setup SEQPACKET ops for transport
> vsock_test: add SOCK_SEQPACKET tests
> virtio/vsock: update trace event for SEQPACKET
>
> drivers/vhost/vsock.c | 22 +-
> include/linux/virtio_vsock.h | 22 +
> include/net/af_vsock.h | 10 +
> .../events/vsock_virtio_transport_common.h | 48 +-
> include/uapi/linux/virtio_vsock.h | 19 +
> net/vmw_vsock/af_vsock.c | 589 +++++++++++------
> net/vmw_vsock/virtio_transport.c | 18 +
> net/vmw_vsock/virtio_transport_common.c | 364 ++++++++--
> net/vmw_vsock/vsock_loopback.c | 13 +
> tools/testing/vsock/util.c | 32 +-
> tools/testing/vsock/util.h | 3 +
> tools/testing/vsock/vsock_test.c | 126 ++++
> 12 files changed, 1013 insertions(+), 253 deletions(-)
>
> v5 -> v6:
> General changelog:
> - virtio transport specific callbacks which send SEQ_BEGIN or
> SEQ_END now hidden inside virtio transport. Only enqueue,
> dequeue and record length callbacks are provided by transport.
>
> - virtio feature bit for SEQPACKET socket support introduced:
> VIRTIO_VSOCK_F_SEQPACKET.
>
> - 'msg_cnt' field in 'struct virtio_vsock_seq_hdr' renamed to
> 'msg_id' and used as id.
>
> Per patch changelog:
> - 'af_vsock: separate wait data loop':
> 1) Commit message updated.
> 2) 'prepare_to_wait()' moved inside while loop(thanks to
> Jorgen Hansen).
> Marked 'Reviewed-by' with 1), but as 2) I removed R-b.
>
> - 'af_vsock: separate receive data loop': commit message
> updated.
> Marked 'Reviewed-by' with that fix.
>
> - 'af_vsock: implement SEQPACKET receive loop': style fixes.
>
> - 'af_vsock: rest of SEQPACKET support':
> 1) 'module_put()' added when transport callback check failed.
> 2) Now only 'seqpacket_allow()' callback called to check
> support of SEQPACKET by transport.
>
> - 'af_vsock: update comments for stream sockets': commit message
> updated.
> Marked 'Reviewed-by' with that fix.
>
> - 'virtio/vsock: set packet's type in send':
> 1) Commit message updated.
> 2) Parameter 'type' from 'virtio_transport_send_credit_update()'
> also removed in this patch instead of in next.
>
> - 'virtio/vsock: dequeue callback for SOCK_SEQPACKET': SEQPACKET
> related state wrapped to special struct.
>
> - 'virtio/vsock: update trace event for SEQPACKET': format strings
> now not broken by new lines.

I left a bunch of comments in the patches, I hope they are easy to fix
:-)

Thanks for the changelogs. About 'per patch changelog', it is very
useful!
Just a suggestion, I think is better to include them in each patch after
the '---' to simplify the review.

You can use git-notes(1) or you can simply edit the format-patch and add
the changelog after the 3 dashes, so that they are ignored when the
patch is applied.

Thanks,
Stefano