Re: [Xen-devel] [PATCH v7 1/2] public/io/netif.h: clarifications to wire formats

[Ian Campbell]

On Tue, 2016-01-12 at 09:58 +, Paul Durrant wrote:
> My previous patch 03809ae7 "document transmit and receive wire formats
> separately" improved documentation of the receive and transmit wire
> formats but further clarifications were requested.
> 
> This patch adds those clarifications.
> 
> Signed-off-by: Paul Durrant 

Acked-by: Ian Campbell 

> Cc: Ian Jackson 
> Cc: Jan Beulich 
> Cc: Keir Fraser 
> Cc: Tim Deegan 
> ---
> 
> v6:
>  - v4 of the original patch was committed so this is an
>    incremental version of the patch in v5.
> 
> v5:
>  - Add extra clarifications.
> ---
>  xen/include/public/io/netif.h | 28 
>  1 file changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/include/public/io/netif.h
> b/xen/include/public/io/netif.h
> index 1790ea0..0a3272f 100644
> --- a/xen/include/public/io/netif.h
> +++ b/xen/include/public/io/netif.h
> @@ -154,19 +154,29 @@
>   * Guest transmit
>   * ==
>   *
> - * This is the 'wire' format for packets:
> + * This is the 'wire' format for transmit (frontend -> backend) packets:
> + *
>   *  Fragment 1: netif_tx_request_t  - flags = NETTXF_*
>   *size = total packet size
>   * [Extra 1: netif_extra_info_t]- (only if fragment 1 flags include
>   * NETTXF_extra_info)
> + *  ...
>   * [Extra N: netif_extra_info_t]- (only if extra N-1 flags include
>   * XEN_NETIF_EXTRA_MORE)
>   *  ...
>   *  Fragment N: netif_tx_request_t  - (only if fragment N-1 flags
> include
> - * NETTXF_more_data)
> + * NETTXF_more_data - flags on
> preceding
> + * extras are not relevent here)
>   *flags = 0
>   *size = fragment size
>   *
> + * NOTE:
> + *
> + * This format slightly is different from that used for receive
> + * (backend -> frontend) packets. Specifically, in a multi-fragment
> + * packet the actual size of fragment 1 can only be determined by
> + * subtracting the sizes of fragments 2..N from the total packet size.
> + *
>   * Ring slot size is 12 octets, however not all request/response
>   * structs use the full size.
>   *
> @@ -202,19 +212,29 @@
>   * Guest receive
>   * =
>   *
> - * This is the 'wire' format for packets:
> + * This is the 'wire' format for receive (backend -> frontend) packets:
> + *
>   *  Fragment 1: netif_rx_request_t  - flags = NETRXF_*
>   *size = fragment size
>   * [Extra 1: netif_extra_info_t]- (only if fragment 1 flags include
>   * NETRXF_extra_info)
> + *  ...
>   * [Extra N: netif_extra_info_t]- (only if extra N-1 flags include
>   * XEN_NETIF_EXTRA_MORE)
>   *  ...
>   *  Fragment N: netif_rx_request_t  - (only if fragment N-1 flags
> include
> - * NETRXF_more_data)
> + * NETRXF_more_data - flags on
> preceding
> + * extras are not relevent here)
>   *flags = 0
>   *size = fragment size
>   *
> + * NOTE:
> + *
> + * This format slightly is different from that used for transmit
> + * (frontend -> backend) packets. Specifically, in a multi-fragment
> + * packet the size of the packet can only be determined by summing the
> + * sizes of fragments 1..N.
> + *
>   * Ring slot size is 8 octets.
>   *
>   * rx request (netif_rx_request_t)
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[Xen-devel] [PATCH v7 1/2] public/io/netif.h: clarifications to wire formats

[Paul Durrant]

My previous patch 03809ae7 "document transmit and receive wire formats
separately" improved documentation of the receive and transmit wire
formats but further clarifications were requested.

This patch adds those clarifications.

Signed-off-by: Paul Durrant 
Cc: Ian Campbell 
Cc: Ian Jackson 
Cc: Jan Beulich 
Cc: Keir Fraser 
Cc: Tim Deegan 
---

v6:
 - v4 of the original patch was committed so this is an
   incremental version of the patch in v5.

v5:
 - Add extra clarifications.
---
 xen/include/public/io/netif.h | 28 
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h
index 1790ea0..0a3272f 100644
--- a/xen/include/public/io/netif.h
+++ b/xen/include/public/io/netif.h
@@ -154,19 +154,29 @@
  * Guest transmit
  * ==
  *
- * This is the 'wire' format for packets:
+ * This is the 'wire' format for transmit (frontend -> backend) packets:
+ *
  *  Fragment 1: netif_tx_request_t  - flags = NETTXF_*
  *size = total packet size
  * [Extra 1: netif_extra_info_t]- (only if fragment 1 flags include
  * NETTXF_extra_info)
+ *  ...
  * [Extra N: netif_extra_info_t]- (only if extra N-1 flags include
  * XEN_NETIF_EXTRA_MORE)
  *  ...
  *  Fragment N: netif_tx_request_t  - (only if fragment N-1 flags include
- * NETTXF_more_data)
+ * NETTXF_more_data - flags on preceding
+ * extras are not relevent here)
  *flags = 0
  *size = fragment size
  *
+ * NOTE:
+ *
+ * This format slightly is different from that used for receive
+ * (backend -> frontend) packets. Specifically, in a multi-fragment
+ * packet the actual size of fragment 1 can only be determined by
+ * subtracting the sizes of fragments 2..N from the total packet size.
+ *
  * Ring slot size is 12 octets, however not all request/response
  * structs use the full size.
  *
@@ -202,19 +212,29 @@
  * Guest receive
  * =
  *
- * This is the 'wire' format for packets:
+ * This is the 'wire' format for receive (backend -> frontend) packets:
+ *
  *  Fragment 1: netif_rx_request_t  - flags = NETRXF_*
  *size = fragment size
  * [Extra 1: netif_extra_info_t]- (only if fragment 1 flags include
  * NETRXF_extra_info)
+ *  ...
  * [Extra N: netif_extra_info_t]- (only if extra N-1 flags include
  * XEN_NETIF_EXTRA_MORE)
  *  ...
  *  Fragment N: netif_rx_request_t  - (only if fragment N-1 flags include
- * NETRXF_more_data)
+ * NETRXF_more_data - flags on preceding
+ * extras are not relevent here)
  *flags = 0
  *size = fragment size
  *
+ * NOTE:
+ *
+ * This format slightly is different from that used for transmit
+ * (frontend -> backend) packets. Specifically, in a multi-fragment
+ * packet the size of the packet can only be determined by summing the
+ * sizes of fragments 1..N.
+ *
  * Ring slot size is 8 octets.
  *
  * rx request (netif_rx_request_t)
-- 
2.1.4


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