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

Arseny Krasnov
2021-04-21T15:06:39Z

On 21.04.2021 12:52, Stefano Garzarella wrote:
> On Tue, Apr 13, 2021 at 03:39:51PM +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, new bit for field 'flags' was added: SEQ_EOR. This bit is
>> set to 1 in last RW packet of message.
>> Now as packets of one socket are not reordered neither on vsock
>> nor on vhost transport layers, such bit allows to restore original
>> message on receiver's side. If user's buffer is smaller than message
>> 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_TRUNC' flags.
>> Tests also implemented.
>>
>> Thanks to stsp2@yandex.ru for encouragements and initial design
>> recommendations.
>>
>> Arseny Krasnov (19):
>> 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: 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: defines and constants for SEQPACKET
>> virtio/vsock: dequeue callback for SOCK_SEQPACKET
>> virtio/vsock: add SEQPACKET receive logic
>> virtio/vsock: rest of SOCK_SEQPACKET support
>> virtio/vsock: enable SEQPACKET for transport
>> vhost/vsock: enable SEQPACKET for transport
>> vsock/loopback: enable SEQPACKET for transport
>> vsock_test: add SOCK_SEQPACKET tests
>> virtio/vsock: update trace event for SEQPACKET
>> af_vsock: serialize writes to shared socket
>>
>> drivers/vhost/vsock.c | 31 +-
>> include/linux/virtio_vsock.h | 11 +
>> include/net/af_vsock.h | 8 +
>> .../events/vsock_virtio_transport_common.h | 5 +-
>> include/uapi/linux/virtio_vsock.h | 9 +
>> net/vmw_vsock/af_vsock.c | 470 +++++++++++------
>> net/vmw_vsock/virtio_transport.c | 17 +
>> net/vmw_vsock/virtio_transport_common.c | 167 ++++--
>> net/vmw_vsock/vsock_loopback.c | 12 +
>> tools/testing/vsock/util.c | 32 +-
>> tools/testing/vsock/util.h | 3 +
>> tools/testing/vsock/vsock_test.c | 63 +++
>> 12 files changed, 625 insertions(+), 203 deletions(-)
>>
>> 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 it

is smaller and more simple than previous logic. Also patch to spec

will be smaller.

>
> I also left some other comments around.
>
> Thanks,
> Stefano
>
>> - all changes to 'include/uapi/linux/virtio_vsock.h' moved
>> to dedicated patch, as these changes linked with patch to
>> spec.
>>
>> - patch 'virtio/vsock: SEQPACKET feature bit support' now merged
>> to 'virtio/vsock: setup SEQPACKET ops for transport'.
>>
>> - patch 'vhost/vsock: SEQPACKET feature bit support' now merged
>> to 'vhost/vsock: setup SEQPACKET ops for transport'.
>>
>> Per patch changelog:
>> see every patch after '---' line.
>>
>> v6 -> v7:
>> General changelog:
>> - virtio transport callback for message length now removed
>> from transport. Length of record is returned by dequeue
>> callback.
>>
>> - function which tries to get message length now returns 0
>> when rx queue is empty. Also length of current message in
>> progress is set to 0, when message processed or error
>> happens.
>>
>> - patches for virtio feature bit moved after patches with
>> transport ops.
>>
>> Per patch changelog:
>> see every patch after '---' line.
>>
>> 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.
>>
>> v4 -> v5:
>> - patches reorganized:
>> 1) Setting of packet's type in 'virtio_transport_send_pkt_info()'
>> is moved to separate patch.
>> 2) Simplifying of 'virtio_transport_send_credit_update()' is
>> moved to separate patch and before main virtio/vsock patches.
>> - style problem fixed
>> - in 'af_vsock: separate receive data loop' extra 'release_sock()'
>> removed
>> - added trace event fields for SEQPACKET
>> - in 'af_vsock: separate wait data loop':
>> 1) 'vsock_wait_data()' removed 'goto out;'
>> 2) Comment for invalid data amount is changed.
>> - in 'af_vsock: rest of SEQPACKET support', 'new_transport' pointer
>> check is moved after 'try_module_get()'
>> - in 'af_vsock: update comments for stream sockets', 'connect-oriented'
>> replaced with 'connection-oriented'
>> - in 'loopback/vsock: setup SEQPACKET ops for transport',
>> 'loopback/vsock' replaced with 'vsock/loopback'
>>
>> v3 -> v4:
>> - SEQPACKET specific metadata moved from packet header to payload
>> and called 'virtio_vsock_seq_hdr'
>> - record integrity check:
>> 1) SEQ_END operation was added, which marks end of record.
>> 2) Both SEQ_BEGIN and SEQ_END carries counter which is incremented
>> on every marker send.
>> - af_vsock.c: socket operations for STREAM and SEQPACKET call same
>> functions instead of having own "gates" differs only by names:
>> 'vsock_seqpacket/stream_getsockopt()' now replaced with
>> 'vsock_connectible_getsockopt()'.
>> - af_vsock.c: 'seqpacket_dequeue' callback returns error and flag that
>> record ready. There is no need to return number of copied bytes,
>> because case when record received successfully is checked at virtio
>> transport layer, when SEQ_END is processed. Also user doesn't need
>> number of copied bytes, because 'recv()' from SEQPACKET could return
>> error, length of users's buffer or length of whole record(both are
>> known in af_vsock.c).
>> - af_vsock.c: both wait loops in af_vsock.c(for data and space) moved
>> to separate functions because now both called from several places.
>> - af_vsock.c: 'vsock_assign_transport()' checks that 'new_transport'
>> pointer is not NULL and returns 'ESOCKTNOSUPPORT' instead of 'ENODEV'
>> if failed to use transport.
>> - tools/testing/vsock/vsock_test.c: rename tests
>>
>> v2 -> v3:
>> - patches reorganized: split for prepare and implementation patches
>> - local variables are declared in "Reverse Christmas tree" manner
>> - virtio_transport_common.c: valid leXX_to_cpu() for vsock header
>> fields access
>> - af_vsock.c: 'vsock_connectible_*sockopt()' added as shared code
>> between stream and seqpacket sockets.
>> - af_vsock.c: loops in '__vsock_*_recvmsg()' refactored.
>> - af_vsock.c: 'vsock_wait_data()' refactored.
>>
>> v1 -> v2:
>> - patches reordered: af_vsock.c related changes now before virtio vsock
>> - patches reorganized: more small patches, where +/- are not mixed
>> - tests for SOCK_SEQPACKET added
>> - all commit messages updated
>> - af_vsock.c: 'vsock_pre_recv_check()' inlined to
>> 'vsock_connectible_recvmsg()'
>> - af_vsock.c: 'vsock_assign_transport()' returns ENODEV if transport
>> was not found
>> - virtio_transport_common.c: transport callback for seqpacket dequeue
>> - virtio_transport_common.c: simplified
>> 'virtio_transport_recv_connected()'
>> - virtio_transport_common.c: send reset on socket and packet type
>> mismatch.
>>
>> Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
>>
>> --
>> 2.25.1
>>
>