Re: [PATCH net-next v1 2/3] virtio_transport_common: Set sibling VMs flag on the receive path

[Paraschiv, Andra-Irina]

On 01/12/2020 18:22, Stefano Garzarella wrote:
> On Tue, Dec 01, 2020 at 05:25:04PM +0200, Andra Paraschiv wrote:
> > The vsock flag can be set during the connect() setup logic, when
> > initializing the vsock address data structure variable. Then the vsock
> > transport is assigned, also considering this flag.
> >
> > The vsock transport is also assigned on the (listen) receive path. The
> > flag needs to be set considering the use case.
> >
> > Set the vsock flag of the remote address to the one targeted for sibling
> > VMs communication if the following conditions are met:
> >
> > * The source CID of the packet is higher than VMADDR_CID_HOST.
> > * The destination CID of the packet is higher than VMADDR_CID_HOST.
> >
> > Signed-off-by: Andra Paraschiv <andraprs@xxxxxxxxxx>
> > ---
> > net/vmw_vsock/virtio_transport_common.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/net/vmw_vsock/virtio_transport_common.c 
> > b/net/vmw_vsock/virtio_transport_common.c
> > index 5956939eebb78..871c84e0916b1 100644
> > --- a/net/vmw_vsock/virtio_transport_common.c
> > +++ b/net/vmw_vsock/virtio_transport_common.c
> > @@ -1062,6 +1062,14 @@ virtio_transport_recv_listen(struct sock *sk, 
> > struct virtio_vsock_pkt *pkt,
> >       vsock_addr_init(&vchild->remote_addr, 
> > le64_to_cpu(pkt->hdr.src_cid),
> >                       le32_to_cpu(pkt->hdr.src_port));
>
> Maybe is better to create an helper function that other transports can
> use for the same purpose or we can put this code in the
> vsock_assign_transport() and set this flag only when the 'psk' argument
> is not NULL (this is the case when it's called by the transports when we
> receive a new connection request and 'psk' is the listener socket).
>
> The second way should allow us to support all the transports without
> touching them.

Ack, I was wondering about the other transports such as vmci or hyperv.

I can move the logic below in the codebase that assigns the transport, 
after checking 'psk'.

> > +      /* If the packet is coming with the source and destination 
> > CIDs higher
> > +       * than VMADDR_CID_HOST, then a vsock channel should be 
> > established for
> > +       * sibling VMs communication.
> > +       */
> > +      if (vchild->local_addr.svm_cid > VMADDR_CID_HOST &&
> > +          vchild->remote_addr.svm_cid > VMADDR_CID_HOST)
> > +              vchild->remote_addr.svm_flag = 
> > VMADDR_FLAG_SIBLING_VMS_COMMUNICATION;
>
> svm_flag is always initialized to 0 in vsock_addr_init(), so this
> assignment is the first one and it's okay, but to avoid future issues
> I'd use |= here to set the flag.

Fair point. I was thinking more towards exclusive flags values 
(purposes), but that's fine with the bitwise operator if we would get a 
set of flag values together. I will also update the field name to 
'svm_flags', let me know if we should keep the previous one or there is 
a better option.

Thanks,
Andra

> > +
> >       ret = vsock_assign_transport(vchild, vsk);
> >       /* Transport assigned (looking at remote_addr) must be the same
> >        * where we received the request.
> > -- 2.20.1 (Apple Git-117)
> >
> >
> >
> >
> > Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. 
> > Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. 
> > Registered in Romania. Registration number J22/2621/2005.




Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.