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=-7.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, 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 4A21DC55ABD for ; Mon, 16 Nov 2020 20:35:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E681720782 for ; Mon, 16 Nov 2020 20:35:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="kqPek+cS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733062AbgKPUet (ORCPT ); Mon, 16 Nov 2020 15:34:49 -0500 Received: from mail.kernel.org ([198.145.29.99]:56650 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726426AbgKPUes (ORCPT ); Mon, 16 Nov 2020 15:34:48 -0500 Received: from kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com (unknown [163.114.132.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E922D20782; Mon, 16 Nov 2020 20:34:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605558888; bh=2ruH7IpyyY7Zc5GxUUT8zaXzNlCfnxxKHpm5NRrSynw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=kqPek+cSqfK3KuBCIHEq81ACpLJg6w6ZwX5PicuP8zzv48hPToHufq2oVBUBTBGcs uJsrzRpTTOC2eghu+tg4ebGCBOLMuOtSsc4lodEqCKrR+F+1rwT7GwX3cbc/1D+msG yynLOcc9kHbxz1jYTpOUnTlVOWBoZd2eCt5piUWQ= Date: Mon, 16 Nov 2020 12:34:47 -0800 From: Jakub Kicinski To: "Mahesh Bandewar (=?UTF-8?B?4KSu4KS54KWH4KS2IOCkrOCkguCkoeClh+CktQ==?= =?UTF-8?B?4KS+4KSw?=) " , Ido Schimmel , David Ahern Cc: Jian Yang , David Miller , linux-netdev , Jian Yang Subject: Re: [PATCH net-next] net-loopback: allow lo dev initial state to be controlled Message-ID: <20201116123447.2be5a827@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: References: <20201111204308.3352959-1-jianyang.kernel@gmail.com> <20201114101709.42ee19e0@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, 16 Nov 2020 12:02:48 -0800 Mahesh Bandewar (=E0=A4=AE=E0=A4=B9=E0= =A5=87=E0=A4=B6 =E0=A4=AC=E0=A4=82=E0=A4=A1=E0=A5=87=E0=A4=B5=E0=A4=BE=E0= =A4=B0) wrote: > > > diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c > > > index a1c77cc00416..76dc92ac65a2 100644 > > > --- a/drivers/net/loopback.c > > > +++ b/drivers/net/loopback.c > > > @@ -219,6 +219,13 @@ static __net_init int loopback_net_init(struct n= et *net) > > > > > > BUG_ON(dev->ifindex !=3D LOOPBACK_IFINDEX); > > > net->loopback_dev =3D dev; > > > + > > > + if (sysctl_netdev_loopback_state) { > > > + /* Bring loopback device UP */ > > > + rtnl_lock(); > > > + dev_open(dev, NULL); > > > + rtnl_unlock(); > > > + } =20 > > > > The only concern I have here is that it breaks notification ordering. > > Is there precedent for NETDEV_UP to be generated before all pernet ops = =20 > > ->init was called? =20 > I'm not sure if any and didn't see any issues in our usage / tests. > I'm not even sure anyone is watching/monitoring for lo status as such. Ido, David, how does this sound to you? I can't think of any particular case where bringing the device up (and populating it's addresses) before per netns init is finished could be problematic. But if this is going to make kernel coding harder the minor convenience of the knob is probably not worth it.