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=-12.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=ham 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 3505CC4743C for ; Mon, 21 Jun 2021 10:52:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C040610CA for ; Mon, 21 Jun 2021 10:52:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229888AbhFUKy5 (ORCPT ); Mon, 21 Jun 2021 06:54:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37490 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229663AbhFUKyp (ORCPT ); Mon, 21 Jun 2021 06:54:45 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BE9F4C061574 for ; Mon, 21 Jun 2021 03:52:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Mime-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=ArqsqdtJsi+Av2RpahMb90Dw/82HEHNmcrpt43Fq8qo=; b=ckhgEGnXdxoyCaIm0tHonbZKzO /R3L3nRBViny3WH/6///6zAdYH/r3FxeU+E4nL/vA4fD1GGA/8XD6O/LY0j+67ysOlLkBh1aU/09k OsEDzpjUnD5RO10PMELOk3ORJMuWIsi7tfi1fwj9qiw4aTRRkBfuRBRw4znFhCAMLX2Ve98S3ELRl +VB/k+xCuVyyRJjGt6ldo1h0UHclFcsqgHOuQg4PXMMdM66tDaLNIMXYe+Ev/CMWRDNJNpDq9ImwD Rb0IQkto5fmOP5KY+lGCx/mSebtQMba0KgjuGgqiSw3quMZ0oCN06ZVmhk+UybnvBHRa3Zmi6bZR1 TJ7St8Sw==; Received: from [2001:8b0:10b:1::3ae] (helo=u3832b3a9db3152.infradead.org) by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1lvHXa-003C28-K2; Mon, 21 Jun 2021 10:52:30 +0000 Message-ID: <2cbe878845eb2a1e3803b3340263ea14436fe053.camel@infradead.org> Subject: Re: [PATCH] net: tun: fix tun_xdp_one() for IFF_TUN mode From: David Woodhouse To: Jason Wang , netdev Cc: Eugenio =?ISO-8859-1?Q?P=E9rez?= Date: Mon, 21 Jun 2021 11:52:28 +0100 In-Reply-To: References: <03ee62602dd7b7101f78e0802249a6e2e4c10b7f.camel@infradead.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-YLTXKaq0aWNt9JJ+5iVe" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org --=-YLTXKaq0aWNt9JJ+5iVe Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2021-06-21 at 15:00 +0800, Jason Wang wrote: > I think it's probably too late to fix? Since it should work before=20 > 043d222f93ab. >=20 > The only way is to backport this fix to stable. Yeah, I assumed the fix would be backported; if not then the "does the kernel have it" check is fairly trivial. I *can* avoid it for now by just using TUNSNDBUF to reduce the sndbuf and then we never take the XDP path at all. My initial crappy hacks are slowly turning into something that I might actually want to commit to mainline (once I've fixed endianness and memory ordering issues): https://gitlab.com/openconnect/openconnect/-/compare/master...vhost I have a couple of remaining problems using vhost-net directly from userspace though. Firstly, I don't think I can set IFF_VNET_HDR on the tun device after opening it. So my model of "open the tun device, then *see* if we can use vhost to accelerate it" doesn't work. I tried setting VHOST_NET_F_VIRTIO_NET_HDR in the vhost features instead, but that gives me a weird failure mode where it drops around half the incoming packets, and I haven't yet worked out why. Of course I don't *actually* want a vnet header at all but the vhost code really assumes that *someone* will add one; if I *don't* set VHOST_NET_F_VIRTIO_NET_HDR then it always *assumes* it can read ten bytes more from the tun socket than the 'peek' says, and barfs when it can't. (Or such was my initial half-thought-through diagnosis before I made it go away by setting IFF_VNET_HDR, at least). Secondly, I need to pull numbers out of my posterior for the VHOST_SET_MEM_TABLE call. This works for x86_64: vmem->nregions =3D 1; vmem->regions[0].guest_phys_addr =3D 4096; vmem->regions[0].memory_size =3D 0x7fffffffe000; vmem->regions[0].userspace_addr =3D 4096; if (ioctl(vpninfo->vhost_fd, VHOST_SET_MEM_TABLE, vmem) < 0) { Is there a way to bypass that and just unconditionally set a 1:1 mapping of *all* userspace address space?=20 It's possible that one or the other of those problems will result in a new advertised "feature" which is so simple (like a 1:1 map) that we can call it a bugfix and backport it along with the tun fix I already posted, and the presence of *that* can indicate that the tun bug is fixed :) --=-YLTXKaq0aWNt9JJ+5iVe Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCECow ggUcMIIEBKADAgECAhEA4rtJSHkq7AnpxKUY8ZlYZjANBgkqhkiG9w0BAQsFADCBlzELMAkGA1UE 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