On 04.07.2021 12:54, Michael S. Tsirkin wrote: > 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 ... > Sorry for late answer, yes You're right, seems this is unwanted drop... Lets wait for Stefano Garzarella feedback Thank You > >>> >>>> 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 >
