From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DA992C433E2 for ; Wed, 2 Sep 2020 16:06:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B296F207EA for ; Wed, 2 Sep 2020 16:06:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="hviSWVzB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728257AbgIBQGY (ORCPT ); Wed, 2 Sep 2020 12:06:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726490AbgIBQGL (ORCPT ); Wed, 2 Sep 2020 12:06:11 -0400 Received: from mail-wm1-x344.google.com (mail-wm1-x344.google.com [IPv6:2a00:1450:4864:20::344]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D8161C061244; Wed, 2 Sep 2020 09:06:10 -0700 (PDT) Received: by mail-wm1-x344.google.com with SMTP id z9so5118409wmk.1; Wed, 02 Sep 2020 09:06:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=0O4dQf9ijqc3DJHTRqGfgFX/txsOCHtKdPYLLD83pqA=; b=hviSWVzBIYj8FNGXfXWECTBNPGc00bdNjjr2aNz5Ks38vUJmN1Xf2Ktai2CSbcmP2S VvVfkEJVTeeT8V5676PV1cEYtiupuQd2cmCPoDWsb8O45qWpgYCDj5hmBmTUf+yaYQj2 ho0JukZbw5l6AthWRtrRgKEaUdei8Yvv8JGta1uPTbu0y4mNdP58YOjK0zHReNBkYfUw cyHjeulLy9QARdE0qADfPB4+xI7aklJAj5ZTPNJWR9gvncijU+56BV9RF7pOkf4q1h+x N9xBb3+Y5ci4a1WR9dBxtbUOf37eGOdWZXhCXrFZjHssMLzFh6A1MoB+6BxbazbPY/bB CjGA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=0O4dQf9ijqc3DJHTRqGfgFX/txsOCHtKdPYLLD83pqA=; b=O0uVaBHiNzTi1y0+w/GxKZvLY5RbBWGG6MxloAis5Nty0NPSKdvoCT1B+MXCReBj+9 ncmNeICb4rgqEHkhjoKPUmXZhw+E6aNNY9jfWJyXEFtl9/ApUCKEEhyDNjILgKh3q3/0 ZAw+L6G4sm4ee5aYr/+WflFa+K9PFq8h6uEI0dxePwHqVFaCbe6w+Q0H4QCPuTVmbSC/ APuutOUZmi4ItZlPKi9vUeTit8XHZFyGBup1Fb28LYRxvTq9oQLObmGJaQVK/PtW6Flj JF9J2Od5Vd9N14jEFTt9lkZkPCMmub7+/mHcLMCCN0CeqDSUHZhhQByF9ixYrPkCX/7e Rsgg== X-Gm-Message-State: AOAM53171q7ZybyUnqTg7XG7Zg6/qzXmYFF4ORsdukJ7ztydx8ghUmWI kFOKkwATvQuDGGRIj+QLZ2h8c/3yaijD3GG6KIY= X-Google-Smtp-Source: ABdhPJxdfC3mgIvbt6wua8mzM+KmTyM8048m+AYjGnIYLBeF9SqkT0az/f0O5TPKGpss8BXufe9V77wBncKPW7hIYZ4= X-Received: by 2002:a1c:f605:: with SMTP id w5mr1358007wmc.26.1599062769544; Wed, 02 Sep 2020 09:06:09 -0700 (PDT) MIME-Version: 1.0 References: <20200707171515.110818-1-izabela.bakollari@gmail.com> <20200804160908.46193-1-izabela.bakollari@gmail.com> In-Reply-To: From: Izabela Bakollari Date: Wed, 2 Sep 2020 18:05:58 +0200 Message-ID: Subject: Re: [PATCHv2 net-next] dropwatch: Support monitoring of dropped frames To: Michal Schmidt Cc: nhorman@tuxdriver.com, davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thank you for your review. I am working on a patch v3 and will apply your suggestions where possible. Best, Izabela On Mon, Aug 31, 2020 at 3:18 PM Michal Schmidt wrote: > > Dne 04. 08. 20 v 18:09 izabela.bakollari@gmail.com napsala: > > From: Izabela Bakollari > > > > Dropwatch is a utility that monitors dropped frames by having userspace > > record them over the dropwatch protocol over a file. This augument > > allows live monitoring of dropped frames using tools like tcpdump. > > > > With this feature, dropwatch allows two additional commands (start and > > stop interface) which allows the assignment of a net_device to the > > dropwatch protocol. When assinged, dropwatch will clone dropped frames, > > and receive them on the assigned interface, allowing tools like tcpdump > > to monitor for them. > > > > With this feature, create a dummy ethernet interface (ip link add dev > > dummy0 type dummy), assign it to the dropwatch kernel subsystem, by using > > these new commands, and then monitor dropped frames in real time by > > running tcpdump -i dummy0. > > > > Signed-off-by: Izabela Bakollari > > --- > > Changes in v2: > > - protect the dummy ethernet interface from being changed by another > > thread/cpu > > --- > > include/uapi/linux/net_dropmon.h | 3 ++ > > net/core/drop_monitor.c | 84 ++++++++++++++++++++++++++++++++ > > 2 files changed, 87 insertions(+) > [...] > > @@ -255,6 +259,21 @@ static void trace_drop_common(struct sk_buff *skb, void *location) > > > > out: > > spin_unlock_irqrestore(&data->lock, flags); > > + spin_lock_irqsave(&interface_lock, flags); > > + if (interface && interface != skb->dev) { > > + skb = skb_clone(skb, GFP_ATOMIC); > > I suggest naming the cloned skb "nskb". Less potential for confusion > that way. > > > + if (skb) { > > + skb->dev = interface; > > + spin_unlock_irqrestore(&interface_lock, flags); > > + netif_receive_skb(skb); > > + } else { > > + spin_unlock_irqrestore(&interface_lock, flags); > > + pr_err("dropwatch: Not enough memory to clone dropped skb\n"); > > Maybe avoid logging the error here. In NET_DM_ALERT_MODE_PACKET mode, > drop monitor does not log about the skb_clone() failure either. > We don't want to open the possibility to flood the logs in case this > somehow gets triggered by every packet. > > A coding style suggestion - can you rearrange it so that the error path > code is spelled out first? Then the regular path does not have to be > indented further: > > nskb = skb_clone(skb, GFP_ATOMIC); > if (!nskb) { > spin_unlock_irqrestore(&interface_lock, flags); > return; > } > > /* ... implicit else ... Proceed normally ... */ > > > + return; > > + } > > + } else { > > + spin_unlock_irqrestore(&interface_lock, flags); > > + } > > } > > > > static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb, void *location) > > @@ -1315,6 +1334,53 @@ static int net_dm_cmd_trace(struct sk_buff *skb, > > return -EOPNOTSUPP; > > } > > > > +static int net_dm_interface_start(struct net *net, const char *ifname) > > +{ > > + struct net_device *nd = dev_get_by_name(net, ifname); > > + > > + if (nd) > > + interface = nd; > > + else > > + return -ENODEV; > > + > > + return 0; > > Similarly here, consider: > > if (!nd) > return -ENODEV; > > interface = nd; > return 0; > > But maybe I'm nitpicking ... > > > +} > > + > > +static int net_dm_interface_stop(struct net *net, const char *ifname) > > +{ > > + dev_put(interface); > > + interface = NULL; > > + > > + return 0; > > +} > > + > > +static int net_dm_cmd_ifc_trace(struct sk_buff *skb, struct genl_info *info) > > +{ > > + struct net *net = sock_net(skb->sk); > > + char ifname[IFNAMSIZ]; > > + > > + if (net_dm_is_monitoring()) > > + return -EBUSY; > > + > > + memset(ifname, 0, IFNAMSIZ); > > + nla_strlcpy(ifname, info->attrs[NET_DM_ATTR_IFNAME], IFNAMSIZ - 1); > > + > > + switch (info->genlhdr->cmd) { > > + case NET_DM_CMD_START_IFC: > > + if (!interface) > > + return net_dm_interface_start(net, ifname); > > + else > > + return -EBUSY; > > + case NET_DM_CMD_STOP_IFC: > > + if (interface) > > + return net_dm_interface_stop(net, interface->name); > > + else > > + return -ENODEV; > > ... and here too. > > Best regards, > Michal >