On Sun, Jul 04, 2021 at 12:23:03PM +0300, Arseny Krasnov wrote: > > On 04.07.2021 11:30, Michael S. Tsirkin wrote: > > On Sun, Jul 04, 2021 at 11:08:13AM +0300, Arseny Krasnov wrote: > >> This patchset modifies receive logic for SOCK_SEQPACKET. > >> Difference between current implementation and this version is that > >> now reader is woken up when there is at least one RW packet in rx > >> queue of socket and data is copied to user's buffer, while merged > >> approach wake up user only when whole message is received and kept > >> in queue. New implementation has several advantages: > >> 1) There is no limit for message length. Merged approach requires > >> that length must be smaller than 'peer_buf_alloc', otherwise > >> transmission will stuck. > >> 2) There is no need to keep whole message in queue, thus no > >> 'kmalloc()' memory will be wasted until EOR is received. > >> > >> Also new approach has some feature: as fragments of message > >> are copied until EOR is received, it is possible that part of > >> message will be already in user's buffer, while rest of message > >> still not received. And if user will be interrupted by signal or > >> timeout with part of message in buffer, it will exit receive loop, > >> leaving rest of message in queue. To solve this problem special > >> callback was added to transport: it is called when user was forced > >> to leave exit loop and tells transport to drop any packet until > >> EOR met. > > Sorry about commenting late in the game. I'm a bit lost > > > > > > SOCK_SEQPACKET > > Provides sequenced, reliable, bidirectional, connection-mode transmission paths for records. A record can be sent using one or more output operations and received using one or more input operations, but a single operation never transfers part of more than one record. Record boundaries are visible to the receiver via the MSG_EOR flag. > > > > it's supposed to be reliable - how is it legal to drop packets? > > Sorry, seems i need to rephrase description. "Packet" here means fragment of record(message) at transport > > layer. As this is SEQPACKET mode, receiver could get only whole message or error, so if only several fragments > > of message was copied (if signal received for example) we can't return it to user - it breaks SEQPACKET sense. I think, > > in this case we can drop rest of record's fragments legally. > > > Thank You Would not that violate the reliable property? IIUC it's only ok to return an error if socket gets closed. Just like e.g. TCP ... > > > > > >> When EOR is found, this mode is disabled and normal packet > >> processing started. Note, that when 'drop until EOR' mode is on, > >> incoming packets still inserted in queue, reader will be woken up, > >> tries to copy data, but nothing will be copied until EOR found. > >> It was possible to drain such unneeded packets it rx work without > >> kicking user, but implemented way is simplest. Anyway, i think > >> such cases are rare. > > > >> New test also added - it tries to copy to invalid user's > >> buffer. > >> > >> Arseny Krasnov (16): > >> af_vsock/virtio/vsock: change seqpacket receive logic > >> af_vsock/virtio/vsock: remove 'seqpacket_has_data' callback > >> virtio/vsock: remove 'msg_count' based logic > >> af_vsock/virtio/vsock: add 'seqpacket_drop()' callback > >> virtio/vsock: remove record size limit for SEQPACKET > >> vsock_test: SEQPACKET read to broken buffer > >> > >> drivers/vhost/vsock.c | 2 +- > >> include/linux/virtio_vsock.h | 7 +- > >> include/net/af_vsock.h | 4 +- > >> net/vmw_vsock/af_vsock.c | 44 ++++---- > >> net/vmw_vsock/virtio_transport.c | 2 +- > >> net/vmw_vsock/virtio_transport_common.c | 103 ++++++++----------- > >> net/vmw_vsock/vsock_loopback.c | 2 +- > >> tools/testing/vsock/vsock_test.c | 120 ++++++++++++++++++++++ > >> 8 files changed, 193 insertions(+), 91 deletions(-) > >> > >> v1 -> v2: > >> Patches reordered and reorganized. > >> > >> Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx> > >> --- > >> cv.txt | 0 > >> 1 file changed, 0 insertions(+), 0 deletions(-) > >> create mode 100644 cv.txt > >> > >> diff --git a/cv.txt b/cv.txt > >> new file mode 100644 > >> index 000000000000..e69de29bb2d1 > >> -- > >> 2.25.1 > >
