From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj2-f7.google.com (mail-pj2-f7.google.com [74.125.227.135]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D5D0D434E3B for ; Tue, 21 Jul 2026 23:04:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.227.135 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784675065; cv=none; b=k7NGvBzId5lcJnPSVZSpX+oJKKe9bwVDvkkeHGQPDTtKWEGA6kU5cd9ryoS4bcQAbIDZm1wZ38JIHH9HDy5/N72niXVcf0xaF7P3nsn6or6L3yK/Cn3//G4K37mAUyYQ1nfkiEogc4pEalMk1ppFOZjK9qp9GHPkaOPVfpPYJsw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784675065; c=relaxed/simple; bh=bsBDcaEWHfWi9EnHhLs/antnWvm8UXtXCT476zF8ObA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OLK/WkXPC76MVimrG3xiSNafpC7sBvE8vb71Ml4i7hFbYpnJeO3MLOVhVV8ymOSV1lL5tmBG8eQtjnvbJgE+14yAoO/hUseZQ0PFjiwNJ4wW72zk6gDtaQwv/vYXdkCt1DKfQlx+zuiN0X85Ykm/YPe1F1rFBrsca+jhXG8bY/M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=W/yU6Voj; arc=none smtp.client-ip=74.125.227.135 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="W/yU6Voj" Received: by mail-pj2-f7.google.com with SMTP id 98e67ed59e1d1-38dcd98e5easo5996425a91.0 for ; Tue, 21 Jul 2026 16:04:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1784675063; x=1785279863; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=78htSqZa+5pBteZG4UB1DmemzqB0eVW2EvSwVDuZiqs=; b=W/yU6Vojyn0IQ/2Dj7hxKhuzvUJFNOt8u6KUXfTzVkwHb3bPt3a667VzXTwGk9Fjwl ncyUYCHOsoUljIQ2aDlEgtRCRhSd9qyd9CF++enHIu9ctuxj1zGOW7WNqIxxhf6jjvQ4 6R7w6FTOY9URCMrhyBCWqMWq2oVCD3HaAWYYP6j9kr/EwnA9e6FxE92i0uQvO6AyWD5i lCN5l40DbKVagHnPq19q+Efzamrui6PyPccwl+um9Dd7h5mrMO+vAIN3w5/M9JcMcpNn BKkItXp0WGGOL8uXrlyO2vpXAuQWpG8uR6+V8MvBjJyQiYLhoIpnewVf+oQ5OB+hKSWq OKRA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784675063; x=1785279863; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=78htSqZa+5pBteZG4UB1DmemzqB0eVW2EvSwVDuZiqs=; b=c5zwuPfMT59+sEDkxj5mmmhscTHflO/fDbvhkrw/qBn7abu4Aedx05CnfHeP4oB34E IcZrSihLq7Mg6M98DVgI77ydlmVoZJ+zMKQkMdJo+7bmcUdot1m7qUqoGSnRIIK4fqsI pN0S/+Ma++8YT+Sbm9ZdCX5+ZRid1HDNZVwYmtWODF2tHZyczndKh293Jm3UFQZW/X8g PL57s6Fp9A5h3C+zoeAe+NleI5hmils15ONFHzwVouXQZGfART+ciEfcaKVz+E5ezCHF pb/0IUUq1BAkD2tUUX5xXdvAwKenCZXE24G1OLPWHdIpkROPQlAjSkcKtoW7fycbCvZ1 9CcQ== X-Forwarded-Encrypted: i=1; AHgh+Rr5JXxzgqDCZZgwmFgYKDgtEIOHD0tnrONV5uz6isFDbfYYH38QWrG2bN/URPBBpV1cxE6xo9L+ivg=@vger.kernel.org X-Gm-Message-State: AOJu0YzFrZIRlb+SfxmxunoU/YbbisfHDUr5RcPBYutFBejUqvN6LpX8 J0NB+NgCbtSZU65fD9hyKZbGCTNtV8I7qQwTaiUAF78Pun8fzSYLZK8s X-Gm-Gg: AR+sD11lD7epHeUhutCL7DK1qfmgyy72gmes5CiSvdU+MB+DCnHCzgitkgrezgEyKMv b0EWyRrnkHsuzbNCGOKDMSHzh7U6lI4U2DayvnDjLBznhKBvJs4JHXPAgria+TWY4f7QZN71MMM z2+UzM3tXffSYyTTAbhkTfGwya9PHcbCWjd/pKIl2QG+eQ8qkjbKLE9oP9KkrH570z+27QmLVkd KYntMho11re18T6IndM3QP+dQN5dHD0SxIFL4H2CKL8t0pmrIJ4cHhCheGiyf5BvQX5Ytj6ORcy QBnVujwLFZjfT26iCz6fXiNY9vhEssKpgnZbbpnz/d90HUe1E32r5aNvGkiT3ZRu6GtdLq2G5cz vvLUPPwPFLeFjJl8STdTWa76+BCEyW3pcxljX4ToCkd89CHk54IpzaJnE8BAAwpiHpPtGkg== X-Received: by 2002:a17:90b:38ca:b0:387:e0db:3d8f with SMTP id 98e67ed59e1d1-38e4b5b4fadmr19229906a91.42.1784675063089; Tue, 21 Jul 2026 16:04:23 -0700 (PDT) Received: from localhost ([2a03:2880:2ff:4::]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-38ea81b2c92sm24438a91.14.2026.07.21.16.04.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jul 2026 16:04:22 -0700 (PDT) Date: Tue, 21 Jul 2026 16:03:37 -0700 From: Stanislav Fomichev To: Jakub Kicinski Cc: Lorenzo Bianconi , Donald Hunter , "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> <20260721082728.74142e6c@kernel.org> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260721082728.74142e6c@kernel.org> On 07/21, Jakub Kicinski wrote: > On Mon, 20 Jul 2026 12:32:55 -0700 Stanislav Fomichev wrote: > > > > (although for gve I might be wrong, there is also gve_rx_skb_csum that only > > > > does UNNECESSARY). > > > > > > > > I'd wait for Jakub to chime in, but it feels like we should just document > > > > what we currently do as a recommended approach: for the drivers > > > > that support COMPLETE, do not report it when the bpf program is attached. > > > > Both NONE and UNNECESSARY are ok. > > > > > > I am not completely sure the UNNECESSARY case is different from the COMPLETE > > > one. What are we supposed to do if the driver reports UNNECESSARY and the ebpf > > > program modifies some fields covered by the rx-checksum? > > > > 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 data? > > Documenting as expected behavior which no driver currently follows > is a bit silly. I thought the ask was to sketch out the plan of > explicitly updating/invalidating the checksum even if we don't > implement it today? This is about current drivers that only report UNNECESSARY with xdp: the xdp prog has to maintain in-packet checksum if it changes the payload. I think it's a fair assumption? In terms of documentation, here is what I have on my side, lmk if that makes sense, roughly: - TODAY - some drivers (correctly) disable reporting COMPLETE when XDP is attached - the xdp program has to modify the packet checksum value if it changes the payload - some drivers (incorrectly?) report COMPLETE for xdp-to-skb path -> unsafe, needs to be fixed - updating the payload doesn't update skb->csum, so the safest option right now is to only do UNNECESSARY with xdp for all drivers - the hw test needs to make sure that the csum is either NONE or UNNECESSARY, and will error out on COMPLETE - TOMORROW - if we want to properly support COMPLETE, we need a new set of kfuncs to update skb->csum value in the skb Does that make sense?