Stefano Garzarella
2021-Jan-28 17:19 UTC
[RFC PATCH v3 00/13] virtio/vsock: introduce SOCK_SEQPACKET support
Hi Arseny, I reviewed a part, tomorrow I hope to finish the other patches. Just a couple of comments in the TODOs below. On Mon, Jan 25, 2021 at 02:09:00PM +0300, Arseny Krasnov wrote:> This patchset impelements support of SOCK_SEQPACKET for virtio >transport. > 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), such packet doesn't carry any data. To send >record, packet with start marker is sent first, then all data is sent >as usual '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, such >marker allows to restore original record on receiver's side. If user's >buffer is smaller that record length, when all out of size data is >dropped. > Maximum length of datagram is not limited as in stream socket, >because same credit logic is used. Difference with stream socket is >that user is not woken up until whole record is received or error >occurred. Implementation also supports 'MSG_EOR' and 'MSG_TRUNC' flags. > Tests also implemented. > > Arseny Krasnov (13): > af_vsock: prepare for SOCK_SEQPACKET support > af_vsock: prepare 'vsock_connectible_recvmsg()' > af_vsock: implement SEQPACKET rx loop > af_vsock: implement send logic for SOCK_SEQPACKET > af_vsock: rest of SEQPACKET support > af_vsock: update comments for stream sockets > virtio/vsock: dequeue callback for SOCK_SEQPACKET > virtio/vsock: fetch length for SEQPACKET record > virtio/vsock: add SEQPACKET receive logic > virtio/vsock: rest of SOCK_SEQPACKET support > virtio/vsock: setup SEQPACKET ops for transport > vhost/vsock: setup SEQPACKET ops for transport > vsock_test: add SOCK_SEQPACKET tests > > drivers/vhost/vsock.c | 7 +- > include/linux/virtio_vsock.h | 12 + > include/net/af_vsock.h | 6 + > include/uapi/linux/virtio_vsock.h | 9 + > net/vmw_vsock/af_vsock.c | 543 ++++++++++++++++------ > net/vmw_vsock/virtio_transport.c | 4 + > net/vmw_vsock/virtio_transport_common.c | 295 ++++++++++-- > tools/testing/vsock/util.c | 32 +- > tools/testing/vsock/util.h | 3 + > tools/testing/vsock/vsock_test.c | 126 +++++ > 10 files changed, 862 insertions(+), 175 deletions(-) > > TODO: > - Support for record integrity control. As transport could drop some > packets, something like "record-id" and record end marker need to > be implemented. Idea is that SEQ_BEGIN packet carries both record > length and record id, end marker(let it be SEQ_END) carries only > record id. To be sure that no one packet was lost, receiver checks > length of data between SEQ_BEGIN and SEQ_END(it must be same with > value in SEQ_BEGIN) and record ids of SEQ_BEGIN and SEQ_END(this > means that both markers were not dropped. I think that easiest way > to implement record id for SEQ_BEGIN is to reuse another field of > packet header(SEQ_BEGIN already uses 'flags' as record length).For > SEQ_END record id could be stored in 'flags'.I don't really like the idea of reusing the 'flags' field for this purpose.> Another way to implement it, is to move metadata of both SEQ_END > and SEQ_BEGIN to payload. But this approach has problem, because > if we move something to payload, such payload is accounted by > credit logic, which fragments payload, while payload with record > length and id couldn't be fragmented. One way to overcome it is to > ignore credit update for SEQ_BEGIN/SEQ_END packet.Another solution > is to update 'stream_has_space()' function: current implementation > return non-zero when at least 1 byte is allowed to use,but updated > version will have extra argument, which is needed length. For 'RW' > packet this argument is 1, for SEQ_BEGIN it is sizeof(record len + > record id) and for SEQ_END it is sizeof(record id).Is the payload accounted by credit logic also if hdr.op is not VIRTIO_VSOCK_OP_RW? I think that we can define a specific header to put after the virtio_vsock_hdr when hdr.op is SEQ_BEGIN or SEQ_END, and in this header we can store the id and the length of the message.> > - What to do, when server doesn't support SOCK_SEQPACKET. In current > implementation RST is replied in the same way when listening port > is not found. I think that current RST is enough,because case when > server doesn't support SEQ_PACKET is same when listener missed(e.g. > no listener in both cases).I think so, but I'll check better if we can have some issues. Thanks, Stefano> > v2 -> v3: > - patches reorganized: split for prepare and implementation patches > - local variables are declared in "Reverse Christmas tree" manner > - virtio_transport_common.c: valid leXX_to_cpu() for vsock header > fields access > - af_vsock.c: 'vsock_connectible_*sockopt()' added as shared code > between stream and seqpacket sockets. > - af_vsock.c: loops in '__vsock_*_recvmsg()' refactored. > - af_vsock.c: 'vsock_wait_data()' refactored. > > v1 -> v2: > - patches reordered: af_vsock.c related changes now before virtio vsock > - patches reorganized: more small patches, where +/- are not mixed > - tests for SOCK_SEQPACKET added > - all commit messages updated > - af_vsock.c: 'vsock_pre_recv_check()' inlined to > 'vsock_connectible_recvmsg()' > - af_vsock.c: 'vsock_assign_transport()' returns ENODEV if transport > was not found > - virtio_transport_common.c: transport callback for seqpacket dequeue > - virtio_transport_common.c: simplified > 'virtio_transport_recv_connected()' > - virtio_transport_common.c: send reset on socket and packet type > mismatch. > >Signed-off-by: Arseny Krasnov <arseny.krasnov at kaspersky.com> > >-- >2.25.1 >