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? > 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
