Hi Arseny,
On Sun, Jan 03, 2021 at 10:54:52PM +0300, Arseny Krasnov wrote:
As SOCK_SEQPACKET guarantees to save record boundaries, so to
do it, new packet operation was added: it marks start of record (with
record length in header). To send record, packet with start marker is
sent first, then all data is transmitted as 'RW' packets. On receiver's
side, length of record is known from packet with start record marker.
Now as packets of one socket are not reordered neither on vsock nor on
vhost transport layers, these marker allows to restore original record
on receiver's side. When each 'RW' packet is inserted to rx queue of
receiver, user is woken up, data is copied to user's buffer and credit
update message is sent. If there is no user waiting for data, credit
won't be updated and sender will wait. Also, if user's buffer is full,
and record is bigger, all unneeded data will be dropped (with sending of
credit update message).
'MSG_EOR' flag is implemented with special value of 'flags' field
in packet header. When record is received with such flags, 'MSG_EOR' is
set in 'recvmsg()' flags. 'MSG_TRUNC' flag is also supported.
In this implementation maximum length of datagram is not limited
as in stream socket.
I did a a quick review. I like the idea of adding SOCK_SEQPACKET, but
the series needs more work.
Some patches miss the SoB, the commit messages are very minimal.
Anyway I like that you shared your patches, but please use RFC tag if
they are not ready to be merged.
Another suggestion is to move the patches that modify the core
(af_vsock.c) before the transport modifications to make the review
easier.
I'd also like to see new tests in tools/testing/vsock/vsock_test.c
Thanks,
Stefano
