On 28.01.2021 20:19, Stefano Garzarella wrote: > 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? Yes, on send any packet with payload could be fragmented if there is not enough space at receiver. On receive 'fwd_cnt' and 'buf_alloc' are updated with header of every packet. Of course, to every such case i've described i can add check for 'RW' packet, to exclude payload from credit accounting, but this is bunch of dumb checks. > > 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. I think it is better than use payload and touch credit logic > >> - 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@xxxxxxxxxxxxx> >> >> -- >> 2.25.1 >> >
