From patchwork Wed Mar 30 22:37:28 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Soheil Hassas Yeganeh X-Patchwork-Id: 603683 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3qb2bb4MjQz9sBm for ; Thu, 31 Mar 2016 09:38:03 +1100 (AEDT) Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b=giBtOd8V; dkim-atps=neutral Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755307AbcC3Whz (ORCPT ); Wed, 30 Mar 2016 18:37:55 -0400 Received: from mail-qg0-f67.google.com ([209.85.192.67]:36457 "EHLO mail-qg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754574AbcC3Whv (ORCPT ); Wed, 30 Mar 2016 18:37:51 -0400 Received: by mail-qg0-f67.google.com with SMTP id n34so6175657qge.3 for ; Wed, 30 Mar 2016 15:37:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=b70jBANJ2kICGCE6w5/H3McmO0BxhvofWNvreihqSxc=; b=giBtOd8VjbACRJLkaWrdILGnPnE9Ay8kq8mfrtXoRtyjJotLu5A1PO++EVeaa9m7oi 97208Nr/58wwVnDgnJGQhx0OewjWFH3KPOxdW+uGeSQ7F3fJNraGkZrL4E0yfC050SCl LwDSIuXOVjV+HIF+P7n3D4mpPlGCdrnMqDvJUI3T1Pk6J88mO3P+jfLF1+ZU3u5w4p9b Inans2l2/+IhI+OiQkLzZNErB2dtCeafwahC0FE9DRCl6YQTVw5mFts3Is+8877ChcO0 85ie9cx5+jULthovzi27onkoa7Y/uBQ/nO1ZlD6xdLHaWbqtogC9sKJEnlA7xe0BfSnw dmRw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=b70jBANJ2kICGCE6w5/H3McmO0BxhvofWNvreihqSxc=; b=khnY0jq8O3DUtFb4YcYk1L5olZs0yWK8CapkkzpJqzSja7i891wCM8dJ2Mi/XeW+mp XHfjVaWvSCSTciPDKXEDuA6AoCdWu6HSd+1oc/7BYoqumJrktjjwyfj+L71/VUgwLX3W bw1zsvcEGkDcfA91styExJ3tBqcQz051iSorCyVbAuCP63U8JcIV5xM4wGccK2uV+FyI UlviQCuugTxDR2Hn1AMKQ+3rX9z9ZkNmLjeN++azXV5KnLx8AWLa/cKcDnsZsetDHoQ6 dPIdUvNCP0wtMpLmb0mZeJk8x0rHcTaD6mKWHDtu8+w426OvxbqROL9VNtz81ehpF7lZ VnKA== X-Gm-Message-State: AD7BkJLFakwUNh71qJk3iyJvtwfS/S6mb/xq9/0bQ2xncRTtlgzhGpk5D/L6+exQCXlFvQ== X-Received: by 10.140.218.139 with SMTP id o133mr13755574qhb.33.1459377470900; Wed, 30 Mar 2016 15:37:50 -0700 (PDT) Received: from soheil.nyc.corp.google.com ([100.101.230.231]) by smtp.gmail.com with ESMTPSA id l67sm2782265qgl.47.2016.03.30.15.37.50 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 30 Mar 2016 15:37:50 -0700 (PDT) From: Soheil Hassas Yeganeh To: davem@davemloft.net, netdev@vger.kernel.org Cc: willemb@google.com, edumazet@google.com, ycheng@google.com, ncardwell@google.com, kafai@fb.com, Soheil Hassas Yeganeh Subject: [PATCH net-next 8/8] sock: document timestamping via cmsg in Documentation Date: Wed, 30 Mar 2016 18:37:28 -0400 Message-Id: <1459377448-2239-9-git-send-email-soheil.kdev@gmail.com> X-Mailer: git-send-email 2.8.0.rc3.226.g39d4020 In-Reply-To: <1459377448-2239-1-git-send-email-soheil.kdev@gmail.com> References: <1459377448-2239-1-git-send-email-soheil.kdev@gmail.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Soheil Hassas Yeganeh Update docs and add code snippet for using cmsg for timestamping. Signed-off-by: Soheil Hassas Yeganeh Acked-by: Willem de Bruijn --- Documentation/networking/timestamping.txt | 48 +++++++++++++++++++++++++++++-- 1 file changed, 45 insertions(+), 3 deletions(-) diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt index a977339..1505d3d 100644 --- a/Documentation/networking/timestamping.txt +++ b/Documentation/networking/timestamping.txt @@ -44,11 +44,17 @@ timeval of SO_TIMESTAMP (ms). Supports multiple types of timestamp requests. As a result, this socket option takes a bitmap of flags, not a boolean. In - err = setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING, (void *) val, &val); + err = setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING, (void *) val, + sizeof(val)); val is an integer with any of the following bits set. Setting other bit returns EINVAL and does not change the current state. +The socket option configures timestamp generation for individual +sk_buffs (1.3.1), timestamp reporting to the socket's error +queue (1.3.2) and options (1.3.3). Timestamp generation can also +be enabled for individual sendmsg calls using cmsg (1.3.4). + 1.3.1 Timestamp Generation @@ -71,13 +77,16 @@ SOF_TIMESTAMPING_RX_SOFTWARE: kernel receive stack. SOF_TIMESTAMPING_TX_HARDWARE: - Request tx timestamps generated by the network adapter. + Request tx timestamps generated by the network adapter. This flag + can be enabled via both socket options and control messages. SOF_TIMESTAMPING_TX_SOFTWARE: Request tx timestamps when data leaves the kernel. These timestamps are generated in the device driver as close as possible, but always prior to, passing the packet to the network interface. Hence, they require driver support and may not be available for all devices. + This flag can be enabled via both socket options and control messages. + SOF_TIMESTAMPING_TX_SCHED: Request tx timestamps prior to entering the packet scheduler. Kernel @@ -90,7 +99,8 @@ SOF_TIMESTAMPING_TX_SCHED: machines with virtual devices where a transmitted packet travels through multiple devices and, hence, multiple packet schedulers, a timestamp is generated at each layer. This allows for fine - grained measurement of queuing delay. + grained measurement of queuing delay. This flag can be enabled + via both socket options and control messages. SOF_TIMESTAMPING_TX_ACK: Request tx timestamps when all data in the send buffer has been @@ -99,6 +109,7 @@ SOF_TIMESTAMPING_TX_ACK: over-report measurement, because the timestamp is generated when all data up to and including the buffer at send() was acknowledged: the cumulative acknowledgment. The mechanism ignores SACK and FACK. + This flag can be enabled via both socket options and control messages. 1.3.2 Timestamp Reporting @@ -183,6 +194,37 @@ having access to the contents of the original packet, so cannot be combined with SOF_TIMESTAMPING_OPT_TSONLY. +1.3.4. Enabling timestamps via control messages + +In addition to socket options, timestamp generation can be requested +per write via cmsg, only for SOF_TIMESTAMPING_TX_* (see Section 1.3.1). +Using this feature, applications can sample timestamps per sendmsg() +without paying the overhead of enabling and disabling timestamps via +setsockopt: + + struct msghdr *msg; + ... + cmsg = CMSG_FIRSTHDR(msg); + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_type = SO_TIMESTAMPING; + cmsg->cmsg_len = CMSG_LEN(sizeof(u32)); + *((u32 *) CMSG_DATA(cmsg)) = SOF_TIMESTAMPING_TX_SCHED | + SOF_TIMESTAMPING_TX_SOFTWARE | + SOF_TIMESTAMPING_TX_ACK; + err = sendmsg(fd, msg, 0); + +The SOF_TIMESTAMPING_TX_* flags set via cmsg will override +the SOF_TIMESTAMPING_TX_* flags set via setsockopt. + +Moreover, applications must still enable timestamp reporting via +setsockopt to receive timestamps: + + u32 val = SOF_TIMESTAMPING_SOFTWARE | + SOF_TIMESTAMPING_OPT_ID /* or any other flag */; + err = setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING, (void *) val, + sizeof(val)); + + 1.4 Bytestream Timestamps The SO_TIMESTAMPING interface supports timestamping of bytes in a