Re: [Xen-devel] [DRAFT v2] XenSock protocol design document

[Juergen Gross <jgross@xxxxxxxx>]

On 13/07/16 17:47, Stefano Stabellini wrote:
> Hi all,
> 
> This is the design document of the XenSock protocol. You can find
> prototypes of the Linux frontend and backend drivers here:
...
> ### Commands Ring
> 
> The shared ring is used by the frontend to forward socket API calls to the
> backend. I'll refer to this ring as **commands ring** to distinguish it from
> other rings which will be created later in the lifecycle of the protocol (data
> rings). The ring format is defined using the familiar `DEFINE_RING_TYPES` 
> macro
> (`xen/include/public/io/ring.h`). Frontend requests are allocated on the ring
> using the `RING_GET_REQUEST` macro.
> 
> The format is defined as follows:
>     
>     #define XENSOCK_SOCKET         0
>     #define XENSOCK_CONNECT        1
>     #define XENSOCK_RELEASE        2
>     #define XENSOCK_BIND           3
>     #define XENSOCK_LISTEN         4
>     #define XENSOCK_ACCEPT         5
>     #define XENSOCK_POLL           6
>     
>     struct xen_xensock_request {
>       uint32_t id; /* private to guest, echoed in response */
>       uint32_t cmd; /* command to execute */
>       uint64_t sockid;
>       union {
>               struct xen_xensock_socket {
>                       uint32_t domain;
>                       uint32_t type;
>                       uint32_t protocol;
>               } socket;
>               struct xen_xensock_connect {
>                       uint8_t addr[28];
>                       uint32_t len;
>                       uint32_t flags;
>                       grant_ref_t ref;
>                       uint32_t evtchn;
>               } connect;
>               struct xen_xensock_bind {
>                       uint8_t addr[28];
>                       uint32_t len;
>               } bind;
>               struct xen_xensock_listen {
>                       uint32_t backlog;
>               } listen;
>               struct xen_xensock_accept {
>                       uint64_t sockid;
>                       grant_ref_t ref;
>                       uint32_t evtchn;
>               } accept;
>       } u;
>     };

Please add padding at the end (or a dummy union member) to make sure
32- and 64-bit variants have the same size (I believe now the size will
be 60 bytes on 32-bit system and 64 bytes on 64-bit).


Juergen


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