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

[Arseny Krasnov <arseny.krasnov@kaspersky.com>]

On 15.03.2021 18:22, Arseny Krasnov wrote:
> On 15.03.2021 14:40, Stefano Garzarella wrote:
>> 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 
>> :-)
> Thank you, yes, there are still small fixes.

So one more question, this is final review for this version of patchset and can

prepare next version with fixes? All other patches will reviewed in next version?

Thank You

>> 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.
> Ack
>> 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
>>
>>