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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A346C46467 for ; Wed, 4 Jan 2023 08:44:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234248AbjADIod (ORCPT ); Wed, 4 Jan 2023 03:44:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42600 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234206AbjADIob (ORCPT ); Wed, 4 Jan 2023 03:44:31 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C812B1A058; Wed, 4 Jan 2023 00:44:30 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 5AFF1B815C2; Wed, 4 Jan 2023 08:44:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 842B9C433D2; Wed, 4 Jan 2023 08:44:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1672821868; bh=dhU/nCpwMIeJj3XRgwHtRg9MAK6LNzONvI7prwCy/ig=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=U8QF2kd66RpNSVoDCopZ1nryaoJTBepMn9LFLZtBnvNQWxoyo0Zzd8IKfGwn/ygcd bHeMTDUXcxeuGd9yQMUOmDDvWNon8Xyxrns4j0hL9lhoQ8VNYCVUHAa4tXFfTJR5UI KRGpurmyhzJvx2LoSltExr2diTEha6oY++G+fO/Zb//ugWWWV0dzIUhfG6n+uRrjqD d+fhCy3qLg3FA3UQGqY0EH5bkh9dXI/yn+h6c1wzv1NjN6X4YggU15jn/JOaxJzO3W k7qHyxXxRAB3H+yXBGkJ0Y96hmFB/Zo6bd202Zfe/g10K0Yfz6JWd48jnSmuTjXm2Z dbF/4YSBsYW7g== Date: Wed, 4 Jan 2023 09:44:24 +0100 From: Lorenzo Bianconi To: Jakub Kicinski Cc: Toke =?iso-8859-1?Q?H=F8iland-J=F8rgensen?= , Tariq Toukan , Andy Gospodarek , ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, hawk@kernel.org, john.fastabend@gmail.com, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, kpsingh@kernel.org, lorenzo.bianconi@redhat.com, netdev@vger.kernel.org, bpf@vger.kernel.org, Jesper Dangaard Brouer , Ilias Apalodimas , Andy Gospodarek , gal@nvidia.com, Saeed Mahameed , tariqt@nvidia.com Subject: Re: [PATCH net-next v2] samples/bpf: fixup some tools to be able to support xdp multibuffer Message-ID: References: <20220621175402.35327-1-gospo@broadcom.com> <40fd78fc-2bb1-8eed-0b64-55cb3db71664@gmail.com> <87k0234pd6.fsf@toke.dk> <20230103172153.58f231ba@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="e1TbLDOmNoNp9c+g" Content-Disposition: inline In-Reply-To: <20230103172153.58f231ba@kernel.org> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org --e1TbLDOmNoNp9c+g Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable > On Tue, 03 Jan 2023 16:19:49 +0100 Toke H=F8iland-J=F8rgensen wrote: > > Hmm, good question! I don't think we've ever explicitly documented any > > assumptions one way or the other. My own mental model has certainly > > always assumed the first frag would continue to be the same size as in > > non-multi-buf packets. >=20 > Interesting! :) My mental model was closer to GRO by frags=20 > so the linear part would have no data, just headers. That is assumption as well. Regards, Lorenzo >=20 > A random datapoint is that bpf_xdp_adjust_head() seems=20 > to enforce that there is at least ETH_HLEN. --e1TbLDOmNoNp9c+g Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTquNwa3Txd3rGGn7Y6cBh0uS2trAUCY7U8aAAKCRA6cBh0uS2t rC0sAP9Wj8TbwcYxrX2MfzTIpike7c8ukxeJjGrDXdn85FrJiwD+Oz3kURLL7uMq 7r4VDGFRDSVANSTQNKfV73cWZrP49AU= =AJ4V -----END PGP SIGNATURE----- --e1TbLDOmNoNp9c+g--