From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Durrant Subject: [PATCH v7 1/2] public/io/netif.h: clarifications to wire formats Date: Tue, 12 Jan 2016 09:58:55 +0000 Message-ID: <1452592736-6463-2-git-send-email-paul.durrant@citrix.com> References: <1452592736-6463-1-git-send-email-paul.durrant@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta4.messagelabs.com ([85.158.143.247]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aIvpK-0007PI-TC for xen-devel@lists.xenproject.org; Tue, 12 Jan 2016 10:05:23 +0000 In-Reply-To: <1452592736-6463-1-git-send-email-paul.durrant@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: xen-devel@lists.xenproject.org Cc: Keir Fraser , Ian Campbell , Tim Deegan , Ian Jackson , Paul Durrant , Jan Beulich List-Id: xen-devel@lists.xenproject.org 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