From patchwork Mon Jan 11 15:25:37 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Durrant X-Patchwork-Id: 8006251 Return-Path: X-Original-To: patchwork-xen-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 7A25F9F2F4 for ; Mon, 11 Jan 2016 15:35:04 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8C68E20279 for ; Mon, 11 Jan 2016 15:35:03 +0000 (UTC) Received: from lists.xen.org (lists.xenproject.org [50.57.142.19]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9046D20256 for ; Mon, 11 Jan 2016 15:35:02 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xen.org) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aIeRu-0001Bc-MU; Mon, 11 Jan 2016 15:32:02 +0000 Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aIeRt-0001BG-Cq for xen-devel@lists.xenproject.org; Mon, 11 Jan 2016 15:32:01 +0000 Received: from [85.158.137.68] by server-7.bemta-3.messagelabs.com id 85/D5-23747-0FAC3965; Mon, 11 Jan 2016 15:32:00 +0000 X-Env-Sender: prvs=811e07856=Paul.Durrant@citrix.com X-Msg-Ref: server-12.tower-31.messagelabs.com!1452526317!15057391!2 X-Originating-IP: [66.165.176.63] X-SpamReason: No, hits=0.0 required=7.0 tests=sa_preprocessor: VHJ1c3RlZCBJUDogNjYuMTY1LjE3Ni42MyA9PiAzMDYwNDg=\n, received_headers: No Received headers X-StarScan-Received: X-StarScan-Version: 7.35.1; banners=-,-,- X-VirusChecked: Checked Received: (qmail 10911 invoked from network); 11 Jan 2016 15:31:59 -0000 Received: from smtp02.citrix.com (HELO SMTP02.CITRIX.COM) (66.165.176.63) by server-12.tower-31.messagelabs.com with RC4-SHA encrypted SMTP; 11 Jan 2016 15:31:59 -0000 X-IronPort-AV: E=Sophos;i="5.20,553,1444694400"; d="scan'208";a="330410054" From: Paul Durrant To: Date: Mon, 11 Jan 2016 15:25:37 +0000 Message-ID: <1452525938-9493-2-git-send-email-paul.durrant@citrix.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1452525938-9493-1-git-send-email-paul.durrant@citrix.com> References: <1452525938-9493-1-git-send-email-paul.durrant@citrix.com> MIME-Version: 1.0 X-DLP: MIA1 Cc: Keir Fraser , Ian Campbell , Tim Deegan , Ian Jackson , Paul Durrant , Jan Beulich Subject: [Xen-devel] [PATCH v5 1/2] public/io/netif.h: document transmit and receive wire formats separately X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Currently there is no documented wire format for guest receive-side packets but the location of the 'wire format' comment block suggests it is the same as transmit-side. This is almost true but there is a subtle difference in the use of the 'size' field for the first fragment. For clarity this patch creates separate comment blocks for receive and transmit side packet wire formats, tries to be more clear about the distinction between 'fragments' and 'extras', and documents the subtlety concerning the size field of the first fragment. Signed-off-by: Paul Durrant Cc: Ian Campbell Cc: Ian Jackson Cc: Jan Beulich Cc: Keir Fraser Cc: Tim Deegan --- v5: - Add extra clarifications. --- xen/include/public/io/netif.h | 59 +++++++++++++++++++++++++++++++++---------- 1 file changed, 46 insertions(+), 13 deletions(-) diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h index e103cf3..0a3272f 100644 --- a/xen/include/public/io/netif.h +++ b/xen/include/public/io/netif.h @@ -151,22 +151,32 @@ */ /* - * This is the 'wire' format for packets: - * Request 1: netif_tx_request_t -- NETTXF_* (any flags) - * [Request 2: netif_extra_info_t] (only if request 1 has - * NETTXF_extra_info) - * [Request 3: netif_extra_info_t] (only if request 2 has - * XEN_NETIF_EXTRA_MORE) - * Request 4: netif_tx_request_t -- NETTXF_more_data - * Request 5: netif_tx_request_t -- NETTXF_more_data - * ... - * Request N: netif_tx_request_t -- 0 - */ - -/* * Guest transmit * ============== * + * 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 - 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. * @@ -202,6 +212,29 @@ * Guest receive * ============= * + * 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 - 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)