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

From: Stefano Garzarella
Date: Tue Mar 16 2021 - 04:09:18 EST

On Tue, Mar 16, 2021 at 06:37:31AM +0300, Arseny Krasnov wrote:

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
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@xxxxxxxxx for encouragements and initial design

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:

- '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
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
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?

For me yes, the other patches seem okay, but I would like to see them later, with the right order and the last things fixed.

Maybe to merge all this we should wait for the agreement from the specs patch.