From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 51A0C27713; Wed, 18 Feb 2026 10:59:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771412342; cv=none; b=bavKAHo5ekrJ8KkL6STBS+VsJYU8/X1CpAWuvkfGuvA/1amcqHhFpZBoo162HYGMz+xTCiqDUP4hc8KQ/UalyF1qFABfbIB+YdA3y/CuMAGLqlTAaec94JxTcUCd5yMmKKpd7ystFquxvWoiKueHVmO5dY8/4u5vtI9z3/C07Pg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771412342; c=relaxed/simple; bh=ExYM4GllfmADUjEjQoM2UYVUP6BlZRRL6bd+IQoD24U=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=u+JGL6e1jaZdTGtPLl6e4VJlplG3SPZcq6rgpR0gtHZasbVa005uHGujvuYS3vEyIxhit640SrvLtUTs56eMJ1Nov8wTyg5K62vGWsNje2oyYlWMtMU/cIPeQl6aVRl3KMm6y54Le87JzccgRq8oDAhEMyVlvVGA6+7v/gDLK3o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oZpUFL7U; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oZpUFL7U" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7038CC19423; Wed, 18 Feb 2026 10:58:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771412341; bh=ExYM4GllfmADUjEjQoM2UYVUP6BlZRRL6bd+IQoD24U=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=oZpUFL7UbeSg9oxx+5ocBW10Hez4rK8Ywn1GTIJvuvO1VAfuPqKCtELpHKDIxBncs KJ4vtX2edWTa0l5u7iBN93TrkRXf6dVi4M1aAAmJnDiBDDV/QPWh/5YrDIHwGGYx2r aF5bVrkGvkBprxjVeOIVYmgcqx/6TafGUQPuVHur18V6fBZGyu1f6djmo9C2MlaUfv oTZQDU1HbZIQ3syH4WHyc+pQHNJIZu0X/gUbwVmj61uun+juAMQcirK2NsKP4R7B16 /BaCu41DMGuoBBTKJk5s3lRe60sThdtIeJJBB1p1XVErSA0FAMGwCIwWqFhihIKxh1 E8R3wRzIaiePg== Message-ID: Date: Wed, 18 Feb 2026 11:58:52 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v3 1/5] netlink: specs: Add XDP RX checksum capability to XDP metadata specs To: Stanislav Fomichev , Jesse Brandeburg , Arthur Fabre Cc: Donald Hunter , Jakub Kicinski , "David S. Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Alexei Starovoitov , Daniel Borkmann , Lorenzo Bianconi , 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 , Jakub Sitnicki , netdev@vger.kernel.org, bpf@vger.kernel.org, intel-wired-lan@lists.osuosl.org, linux-kselftest@vger.kernel.org, kernel-team , Willem Ferguson References: <20260217-bpf-xdp-meta-rxcksum-v3-0-30024c50ba71@kernel.org> <20260217-bpf-xdp-meta-rxcksum-v3-1-30024c50ba71@kernel.org> Content-Language: en-US From: Jesper Dangaard Brouer In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 18/02/2026 02.01, Stanislav Fomichev wrote: > On 02/17, Lorenzo Bianconi wrote: >> Introduce XDP RX checksum capability to XDP metadata specs. XDP RX >> checksum will be use by devices capable of exposing receive checksum >> result via bpf_xdp_metadata_rx_checksum(). >> Moreover, introduce xmo_rx_checksum netdev callback in order to allow >> the eBPF program bound to the device to retrieve the RX checksum result >> computed by the hw NIC. >> >> Signed-off-by: Lorenzo Bianconi >> --- >> Documentation/netlink/specs/netdev.yaml | 5 +++++ >> include/net/xdp.h | 13 +++++++++++++ >> include/uapi/linux/netdev.h | 3 +++ >> net/core/xdp.c | 28 ++++++++++++++++++++++++++++ >> tools/include/uapi/linux/netdev.h | 3 +++ >> 5 files changed, 52 insertions(+) >> >> diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml >> index 596c306ce52b8303b20680ff0cd34d4fd9db0e48..58eda634668a07860447a65d9fc2284839af6244 100644 >> --- a/Documentation/netlink/specs/netdev.yaml >> +++ b/Documentation/netlink/specs/netdev.yaml >> @@ -61,6 +61,11 @@ definitions: >> doc: | >> Device is capable of exposing receive packet VLAN tag via >> bpf_xdp_metadata_rx_vlan_tag(). >> + - >> + name: checksum >> + doc: | >> + Device is capable of exposing receive checksum result via >> + bpf_xdp_metadata_rx_checksum(). >> - >> type: flags >> name: xsk-flags >> diff --git a/include/net/xdp.h b/include/net/xdp.h >> index aa742f413c358575396530879af4570dc3fc18de..00abb2e1e85514b4080d0e4e6e3b8f5f67f73b61 100644 >> --- a/include/net/xdp.h >> +++ b/include/net/xdp.h >> @@ -586,6 +586,10 @@ void xdp_attachment_setup(struct xdp_attachment_info *info, >> NETDEV_XDP_RX_METADATA_VLAN_TAG, \ >> bpf_xdp_metadata_rx_vlan_tag, \ >> xmo_rx_vlan_tag) \ >> + XDP_METADATA_KFUNC(XDP_METADATA_KFUNC_RX_CHECKSUM, \ >> + NETDEV_XDP_RX_METADATA_CHECKSUM, \ >> + bpf_xdp_metadata_rx_checksum, \ >> + xmo_rx_checksum) >> >> enum xdp_rx_metadata { >> #define XDP_METADATA_KFUNC(name, _, __, ___) name, >> @@ -643,12 +647,21 @@ enum xdp_rss_hash_type { >> XDP_RSS_TYPE_L4_IPV6_SCTP_EX = XDP_RSS_TYPE_L4_IPV6_SCTP | XDP_RSS_L3_DYNHDR, >> }; >> >> +enum xdp_checksum { >> + XDP_CHECKSUM_NONE = CHECKSUM_NONE, >> + XDP_CHECKSUM_UNNECESSARY = CHECKSUM_UNNECESSARY, >> + XDP_CHECKSUM_COMPLETE = CHECKSUM_COMPLETE, >> +}; >> + >> struct xdp_metadata_ops { >> int (*xmo_rx_timestamp)(const struct xdp_md *ctx, u64 *timestamp); >> int (*xmo_rx_hash)(const struct xdp_md *ctx, u32 *hash, >> enum xdp_rss_hash_type *rss_type); >> int (*xmo_rx_vlan_tag)(const struct xdp_md *ctx, __be16 *vlan_proto, >> u16 *vlan_tci); >> + int (*xmo_rx_checksum)(const struct xdp_md *ctx, >> + enum xdp_checksum *ip_summed, >> + u32 *cksum_meta); >> }; >> >> #ifdef CONFIG_NET >> diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h >> index e0b579a1df4f2126acec6c44c299e97bbbefe640..d20da430cfd57bc26b5ea2f406c27b48d8a81693 100644 >> --- a/include/uapi/linux/netdev.h >> +++ b/include/uapi/linux/netdev.h >> @@ -47,11 +47,14 @@ enum netdev_xdp_act { >> * hash via bpf_xdp_metadata_rx_hash(). >> * @NETDEV_XDP_RX_METADATA_VLAN_TAG: Device is capable of exposing receive >> * packet VLAN tag via bpf_xdp_metadata_rx_vlan_tag(). >> + * @NETDEV_XDP_RX_METADATA_CHECKSUM: Device is capable of exposing receive >> + * checksum result via bpf_xdp_metadata_rx_checksum(). >> */ >> enum netdev_xdp_rx_metadata { >> NETDEV_XDP_RX_METADATA_TIMESTAMP = 1, >> NETDEV_XDP_RX_METADATA_HASH = 2, >> NETDEV_XDP_RX_METADATA_VLAN_TAG = 4, >> + NETDEV_XDP_RX_METADATA_CHECKSUM = 8, >> }; >> >> /** >> diff --git a/net/core/xdp.c b/net/core/xdp.c >> index fee6d080ee85fc2d278bfdddfd1365633058ec06..7d1e08d8ab4151ab42c91203def2afafc66d3149 100644 >> --- a/net/core/xdp.c >> +++ b/net/core/xdp.c >> @@ -961,6 +961,34 @@ __bpf_kfunc int bpf_xdp_metadata_rx_vlan_tag(const struct xdp_md *ctx, >> return -EOPNOTSUPP; >> } >> >> +/** >> + * bpf_xdp_metadata_rx_checksum - Read XDP frame RX checksum. >> + * @ctx: XDP context pointer. >> + * @ip_summed: Return value pointer indicating checksum result. >> + * @cksum_meta: Return value pointer indicating checksum result metadata. >> + * >> + * In case of success, ``ip_summed`` is set to the RX checksum result. Possible >> + * values are: >> + * ``XDP_CHECKSUM_NONE`` >> + * ``XDP_CHECKSUM_UNNECESSARY`` >> + * ``XDP_CHECKSUM_COMPLETE`` >> + * >> + * In case of success, ``cksum_meta`` contains the hw computed checksum value >> + * for ``XDP_CHECKSUM_COMPLETE`` or the ``csum_level`` for >> + * ``XDP_CHECKSUM_UNNECESSARY``. It is set to 0 for ``XDP_CHECKSUM_NONE`` > > The only thing I'm still not sure about is the csum_level and whether > we need to export it or just start with csum_level=0 and extend later > when needed. The rest looks good. > > Jesper, Lorenzo mentioned that you might need it? Can you clarify? At Cloudflare our load-balancer Unimog[1] does GUE (Generic UDP Encapsulation) when XDP_TX'ing packets to neighboring servers. Thus, I assume we want to know the csum_level, as this is for encapsulated packets, right? Cc Jesse, as he knows more about the hardware and csum_level. To Jesse, we need to test how hardware handles our GUE packet format (which is slightly modified). Cc Arthur + Willem, as they knows the details around how Unimog currently have to recalc packet checksums in software. Hopefully this patchset can help us avoid doing this in some cases. --Jesper [1] https://blog.cloudflare.com/unimog-cloudflares-edge-load-balancer/#encapsulation [Patch-0/5] https://lore.kernel.org/all/20260217-bpf-xdp-meta-rxcksum-v3-0-30024c50ba71@kernel.org/