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[35.245.46.111]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-5eae983efe8sm587906e0c.17.2026.10.20.13.19.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Oct 2026 13:19:41 -0700 (PDT) Date: Tue, 20 Oct 2026 16:19:41 -0400 From: Willem de Bruijn To: "Michael S. Tsirkin" , Willem de Bruijn Cc: linux-kernel@vger.kernel.org, Chris Arges , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Phil Sutter , Jason Wang , =?UTF-8?B?RXVnZW5pbyBQw6lyZXo=?= , Xuan Zhuo , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, virtualization@lists.linux.dev, Max Krasnyansky , Rusty Russell , Jonathan Corbet , Shuah Khan , Randy Dunlap , Simon Horman , linux-doc@vger.kernel.org Message-ID: In-Reply-To: <20261020155917-mutt-send-email-mst@kernel.org> References: <6f23c55c6eba3e3ec6b2c7e3a80728a326ed58af.1792411304.git.mst@redhat.com> <20261020155917-mutt-send-email-mst@kernel.org> Subject: Re: [PATCH net v3 6/8] net: add a sysctl to opt out of virtio net hdr checksum validation X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Michael S. Tsirkin wrote: > On Tue, Oct 20, 2026 at 03:54:23PM -0400, Willem de Bruijn wrote: > > Michael S. Tsirkin wrote: > > > The ingress validation as implemented by the previous > > > patch is stricter than what it replaced: GSO > > > packets whose checksum metadata matches no transport header are > > > dropped, and non-GSO ones get their checksum completed in place. > > > Such packets used to pass with the metadata unvalidated, > > > and with no overhead. > > > > > > I judge that this should not affect any deployments, but there is still > > > some risk that it does. In case a deployment depends on them anyway, > > > provide a per-netns switch to get the old behavior back: > > > > > > echo 0 > /proc/sys/net/core/virtio_net_hdr_csum_check > > > > > > The default is validating. > > > > > > Assisted-by: LLM > > > Signed-off-by: Michael S. Tsirkin > > > --- > > > Documentation/admin-guide/sysctl/net.rst | 19 ++++++++ > > > include/linux/virtio_net.h | 23 +++++++++ > > > include/net/netns/core.h | 1 + > > > net/core/dev.c | 6 +++ > > > net/core/net_namespace.c | 1 + > > > net/core/sysctl_net_core.c | 60 ++++++++++++++++++++++++ > > > 6 files changed, 110 insertions(+) > > > > > > diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst > > > index e586e17fc7a5..b1a1c4714b22 100644 > > > --- a/Documentation/admin-guide/sysctl/net.rst > > > +++ b/Documentation/admin-guide/sysctl/net.rst > > > @@ -246,6 +246,25 @@ processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set. > > > Default: 1 (on) > > > > > > > > > +virtio_net_hdr_csum_check > > > +------------------------- > > > > virtio_net_hdr_validate? In case we do have to add more validation > > later. > > If you insist. My worry would be what if that validation is again > user-visible somehow and we need to distinguish users who want > to disable that future thing and users who want to disable > just this current thing. > > Hard to predict the future. But I will go with your intuition. Thanks, but definitely feel free to ignore my suggestions. My intuition would be to define as 0: off 1: everything one 2+: sadly needed fudge values because we keep having to tighten, but some crazy workloads need to opt-out to avoid breakage.