Re: [RFC PATCH v3 10/13] virtio/vsock: rest of SOCK_SEQPACKET support

[Stefano Garzarella]

On Fri, Jan 29, 2021 at 07:00:16PM +0300, Arseny Krasnov wrote:
> On 29.01.2021 14:03, Stefano Garzarella wrote:
> > On Mon, Jan 25, 2021 at 02:15:26PM +0300, Arseny Krasnov wrote:
> > > This adds rest of logic for SEQPACKET:
> > > 1) Shared functions for packet sending now set valid type of packet
> > >   according socket type.
> > > 2) SEQPACKET specific function like SEQ_BEGIN send and data dequeue.
> > > 3) TAP support for SEQPACKET is not so easy if it is necessary to
> > > send whole record to TAP interface. This could be done by allocating
> > > new packet when whole record is received, data of record must be
> > > copied to TAP packet.
> > >
> > > Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
> > > ---
> > > include/linux/virtio_vsock.h            |  7 ++++
> > > net/vmw_vsock/virtio_transport_common.c | 55 +++++++++++++++++++++----
> > > 2 files changed, 55 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> > > index af8705ea8b95..ad9783df97c9 100644
> > > --- a/include/linux/virtio_vsock.h
> > > +++ b/include/linux/virtio_vsock.h
> > > @@ -84,7 +84,14 @@ virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
> > > 			       struct msghdr *msg,
> > > 			       size_t len, int flags);
> > >
> > > +bool virtio_transport_seqpacket_seq_send_len(struct vsock_sock *vsk, size_t len);
> > > size_t virtio_transport_seqpacket_seq_get_len(struct vsock_sock *vsk);
> > > +ssize_t
> > > +virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
> > > +				   struct msghdr *msg,
> > > +				   size_t len,
> > > +				   int type);
> > > +
> > > s64 virtio_transport_stream_has_data(struct vsock_sock *vsk);
> > > s64 virtio_transport_stream_has_space(struct vsock_sock *vsk);
> > >
> > > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> > > index 90f9feef9d8f..fab14679ca7b 100644
> > > --- a/net/vmw_vsock/virtio_transport_common.c
> > > +++ b/net/vmw_vsock/virtio_transport_common.c
> > > @@ -139,6 +139,7 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
> > > 		break;
> > > 	case VIRTIO_VSOCK_OP_CREDIT_UPDATE:
> > > 	case VIRTIO_VSOCK_OP_CREDIT_REQUEST:
> > > +	case VIRTIO_VSOCK_OP_SEQ_BEGIN:
> > > 		hdr->op = cpu_to_le16(AF_VSOCK_OP_CONTROL);
> > > 		break;
> > > 	default:
> > > @@ -157,6 +158,10 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
> > >
> > > void virtio_transport_deliver_tap_pkt(struct virtio_vsock_pkt *pkt)
> > > {
> > > +	/* TODO: implement tap support for SOCK_SEQPACKET. */
> > I think we should do this before merging SOCK_SEQPACKET support because
> > it can be very useful to use tcpdump to figure out what's going on, do
> > you think it's complicated?
>
> It is not complicated if for TAP interface we will consider seqpacket
>
> same as stream, e.g. TAP reader won't see whole record as one
>
> packet,it will see fragments of record as in stream socket. Implement

Maybe as initial support we can have this limitation and complete it 
later.

> normal interpretation of seqpacket is not complicated, but requires
>
> some extra work. Ok, i'll check it

Thanks,
Stefano