From patchwork Thu Jul 9 09:45:51 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Magnus Karlsson X-Patchwork-Id: 1325858 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=intel.com Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4B2WWs2txGz9sRR for ; Thu, 9 Jul 2020 19:46:01 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726514AbgGIJqA (ORCPT ); Thu, 9 Jul 2020 05:46:00 -0400 Received: from mga09.intel.com ([134.134.136.24]:53390 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726339AbgGIJp7 (ORCPT ); Thu, 9 Jul 2020 05:45:59 -0400 IronPort-SDR: tBHOgqlGJPDw0eFX+9Bz7KoHOSXV2Hh+Ri6SHJBFvweU42Wg8FG/PfUU496ub2Ap+gEqlDf4vY VfOdb2TRSNyw== X-IronPort-AV: E=McAfee;i="6000,8403,9676"; a="149454087" X-IronPort-AV: E=Sophos;i="5.75,331,1589266800"; d="scan'208";a="149454087" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Jul 2020 02:45:59 -0700 IronPort-SDR: AMqKClmMofe59HSHV7z7IqzdRowmHT5pxZC3L4LEaXOSDt3xL8EhYlHs1sq10tW+UsLzZ2j/CA HBkN8zCauOxA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,331,1589266800"; d="scan'208";a="428151292" Received: from mkarlsso-mobl.ger.corp.intel.com (HELO localhost.localdomain) ([10.249.32.71]) by orsmga004.jf.intel.com with ESMTP; 09 Jul 2020 02:45:56 -0700 From: Magnus Karlsson To: magnus.karlsson@intel.com, bjorn.topel@intel.com, ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org, jonathan.lemon@gmail.com Cc: A.Zema@falconvsystems.com Subject: [PATCH bpf] xsk: do not discard packet when QUEUE_STATE_FROZEN Date: Thu, 9 Jul 2020 11:45:51 +0200 Message-Id: <1594287951-27479-1-git-send-email-magnus.karlsson@intel.com> X-Mailer: git-send-email 2.7.4 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org In the skb Tx path, transmission of a packet is performed with dev_direct_xmit(). When QUEUE_STATE_FROZEN is set in the transmit routines, it returns NETDEV_TX_BUSY signifying that it was not possible to send the packet now, please try later. Unfortunately, the xsk transmit code discarded the packet and returned EBUSY to the application. Fix this unnecessary packet loss, by not discarding the packet and return EAGAIN. As EAGAIN is returned to the application, it can then retry the send operation and the packet will finally be sent as we will likely not be in the QUEUE_STATE_FROZEN state anymore. So EAGAIN tells the application that the packet was not discarded from the Tx ring and that it needs to call send() again. EBUSY, on the other hand, signifies that the packet was not sent and discarded from the Tx ring. The application needs to put the packet on the Tx ring again if it wants it to be sent. This unnecessary packet loss has been reported by the user below to occur at high transmit loads. Fixes: 35fcde7f8deb ("xsk: support for Tx") Signed-off-by: Magnus Karlsson Reported-by: Arkadiusz Zema Suggested-by: Arkadiusz Zema --- net/xdp/xsk.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 3700266..5304250 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -376,13 +376,22 @@ static int xsk_generic_xmit(struct sock *sk) skb->destructor = xsk_destruct_skb; err = dev_direct_xmit(skb, xs->queue_id); - xskq_cons_release(xs->tx); /* Ignore NET_XMIT_CN as packet might have been sent */ - if (err == NET_XMIT_DROP || err == NETDEV_TX_BUSY) { + if (err == NET_XMIT_DROP) { /* SKB completed but not sent */ + xskq_cons_release(xs->tx); err = -EBUSY; goto out; + } else if (err == NETDEV_TX_BUSY) { + /* QUEUE_STATE_FROZEN, tell application to + * retry sending the packet + */ + skb->destructor = NULL; + kfree_skb(skb); + err = -EAGAIN; + goto out; } + xskq_cons_release(xs->tx); sent_frame = true; }