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. drivers/vhost/vsock.c | 6 +- include/linux/virtio_vsock.h | 7 + include/net/af_vsock.h | 4 + include/uapi/linux/virtio_vsock.h | 9 + net/vmw_vsock/af_vsock.c | 457 +++++++++++++++++++----- net/vmw_vsock/virtio_transport.c | 3 + net/vmw_vsock/virtio_transport_common.c | 323 ++++++++++++++--- 7 files changed, 673 insertions(+), 136 deletions(-) -- 2.25.1
