From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F35C33C988F; Mon, 20 Jul 2026 22:08:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784585336; cv=none; b=WcMMXr6pXg1qtp6fahKO59vhDQH4PnVakv6uo9ThpG9VYhoWv2eIFJ7sHSqBNqwKfmHX5YLc2wbxwDtU+zReXkbYw8g6Kel1++u8zF/wsrNI9ykwuyU4TsJN33E+RCtUeQwu49zLm+nuThzQhhJcwG9gTiJtKltae0UhiGmncFk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784585336; c=relaxed/simple; bh=6ZcSLCTlpeIECEMaTVZOgkzcpZtJ4JqCSc2WOUljvDI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fsDOuR+DoKugxeMm3C3RzA3zGR+y+lgtKNqoRinDAWrhex9D+0ef3pAR84JB95cRq8M9L9fOkTHv8LLhzr4IiA7fVzMKtvxWB4tUWfiRtzJOYGOXjnzQGZyyLeWa+IV7fcYMOV4dMbQIyVq4TryYe2bLLYw0bN2o7Rqle1AuzYw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mT6UbtmY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mT6UbtmY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2966B1F000E9; Mon, 20 Jul 2026 22:08:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784585334; bh=z11ITbQvt4NP+i0GjTjmCBTKhf0Lxqrhu6WfRIGhnpQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=mT6UbtmYOcXsiFK7elvuKwRHp7wkmlw03MJRL5gqKdAITLpvWFTnN92LZxOKLVAcj fXA1y3IrVJq/qALoBLutVthJWs6NmYVJ7RPOJ5wSk1RXGByldWP4//t2HWuNmCjQp2 ciykP2LyK2iACclGNuy2mMgN6gNl/30oqyv1T0gJxiQsFY6T0XgT7hzt1y7vIUTWpR MBW156AzU1Ad82gIWGpqXDhgVPauUlTW0kFkWxhGT58S3tExitlwiz9EUbtRT6lsg4 dsY+rQPSG72eOv4NPr7XthzSTlx8UwILF0pPjRcVGHOAcGXE+InVWtBRsAAx8sfR9b yFes13reBTApQ== Date: Tue, 21 Jul 2026 00:08:52 +0200 From: Lorenzo Bianconi To: Stanislav Fomichev Cc: Donald Hunter , Jakub Kicinski , "David S. Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Stanislav Fomichev , Andrew Lunn , Tony Nguyen , Przemek Kitszel , Alexander Lobakin , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Hao Luo , Jiri Olsa , Shuah Khan , Maciej Fijalkowski , Jonathan Corbet , Shuah Khan , Kumar Kartikeya Dwivedi , Emil Tsalapatis , Vladimir Vdovin , Jakub Sitnicki , netdev@vger.kernel.org, bpf@vger.kernel.org, intel-wired-lan@lists.osuosl.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH bpf-next v5 8/8] selftests: net: add test for XDP_PASS skb checksum invalidation Message-ID: References: <20260715-bpf-xdp-meta-rxcksum-v5-0-623d5c0d0ab7@kernel.org> <20260715-bpf-xdp-meta-rxcksum-v5-8-623d5c0d0ab7@kernel.org> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="Poik8L3QQ7fei6lR" Content-Disposition: inline In-Reply-To: --Poik8L3QQ7fei6lR Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable > On 07/16, Lorenzo Bianconi wrote: > > On Jul 16, Stanislav Fomichev wrote: > > > On 07/15, Lorenzo Bianconi wrote: > > > > Add a test that verifies skb->ip_summed is set to CHECKSUM_NONE > > > > when a device running in XDP mode creates an skb from a xdp_buff > > > > if the attached ebpf program returns an XDP_PASS. > > > > The test attaches an XDP program returning XDP_PASS, and a TC > > > > ingress program that runs the bpf_skb_rx_checksum() kfunc to > > > > inspect the resulting skb. After XDP_PASS the driver must invalidate > > > > any previously computed hardware RX checksum since XDP may have > > > > modified the packet data. > > > > The BPF program counts packets per checksum type in a map, and the > > > > test runner verifies that after sending traffic the CHECKSUM_NONE > > > > counter is non-zero while CHECKSUM_UNNECESSARY and CHECKSUM_COMPLETE > > > > counters are zero. > > > >=20 > > > > Signed-off-by: Lorenzo Bianconi > > > > --- > > > > Documentation/networking/xdp-rx-metadata.rst | 5 ++ > > > > .../selftests/drivers/net/hw/xdp_metadata.py | 55 ++++++++++= +++++- > > > > .../selftests/net/lib/skb_metadata_csum.bpf.c | 73 ++++++++++= ++++++++++++ > > > > 3 files changed, 132 insertions(+), 1 deletion(-) > > > >=20 > > > > diff --git a/Documentation/networking/xdp-rx-metadata.rst b/Documen= tation/networking/xdp-rx-metadata.rst > > > > index 93918b3769a3..7434ac98242a 100644 > > > > --- a/Documentation/networking/xdp-rx-metadata.rst > > > > +++ b/Documentation/networking/xdp-rx-metadata.rst > > > > @@ -90,6 +90,11 @@ conversion, and the XDP metadata is not used by = the kernel when building > > > > ``skbs``. However, TC-BPF programs can access the XDP metadata are= a using > > > > the ``data_meta`` pointer. > > >=20 > > > [..] > > >=20 > > > > +If a driver is running in XDP mode, any existing hardware RX check= sum > > > > +(``CHECKSUM_UNNECESSARY`` or ``CHECKSUM_COMPLETE``) must be invali= dated > > > > +by setting ``skb->ip_summed`` to ``CHECKSUM_NONE`` before passing = the > > > > +skb to the kernel, since XDP may have modified the packet data. > > > > + > > > > In the future, we'd like to support a case where an XDP program > > > > can override some of the metadata used for building ``skbs``. > > >=20 > > > Sorry for keeping nitpicking on this, but I'm still not convinced that > > > it is what we currently do. From my previous reply: > >=20 > > no worries :) > > My current take-away from the previous discussion is we just need to do= cument > > what would be the driver expected behaviour adding a kselftest for it (= without > > modifying any driver). > >=20 > > >=20 > > > > > Looking at a few drivers: > > > > > - bnxt (bnxt_rx_pkt) does UNNECESSARY - ok > > > > > - mlx5 (mlx5e_handle_csum) does UNNECESSARY and skips COMPLETE if= there is > > > > > bpf prog attached > > > > > - fbnic (fbnic_rx_csum) - can do COMPLETE even with xdp attached? > > > > > - gve (gve_rx) - can do COMPLETE even with xdp attached? > > >=20 > > > (although for gve I might be wrong, there is also gve_rx_skb_csum tha= t only > > > does UNNECESSARY). > > >=20 > > > I'd wait for Jakub to chime in, but it feels like we should just docu= ment > > > what we currently do as a recommended approach: for the drivers > > > that support COMPLETE, do not report it when the bpf program is attac= hed. > > > Both NONE and UNNECESSARY are ok. > >=20 > > I am not completely sure the UNNECESSARY case is different from the COM= PLETE > > one. What are we supposed to do if the driver reports UNNECESSARY and t= he ebpf > > program modifies some fields covered by the rx-checksum? >=20 > For unnecessary, I think the safe expectation is that the bpf program > will update the value of the checksum in the packet if it touches the dat= a? I do not have a strong opinion on it. @Jakub: any input on it? >=20 > > > Also, did you run this test on real HW? NIPA now has HW tests, maybe = it > > > makes sense to route this series via net-next to get the real coverag= e? > >=20 > > What about splitting this series and have two different series: > > - bpf-next: add xdp rx kfunc and related selftest > > - net-next: add kselftest for the driver expected behaviour. > >=20 > > What do you think? >=20 > I'd post everything to net-next to get the HW coverage. Once you get all > the acks we can ask the maintainers' guidance. ack, I am fine with that. Regards, Lorenzo --Poik8L3QQ7fei6lR Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTquNwa3Txd3rGGn7Y6cBh0uS2trAUCal6cdAAKCRA6cBh0uS2t rBbAAQDuKu2WNBvm2CcO6No6R6S427G1mLi7hdfmjTMduKOLYwEA9/j6hFjjCn7s 9OGAW6D4Pk31PHVDpSIYW7xQEkUWTwU= =j1RN -----END PGP SIGNATURE----- --Poik8L3QQ7fei6lR--