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Fri, 06 Nov 2026 12:59:48 -0800 (PST) Received: from L9JK9NPFH9.lan ([104.28.20.58]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c4d3562df86sm104305466b.24.2026.11.06.12.59.45 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 06 Nov 2026 12:59:46 -0800 (PST) From: Tianyi Gao To: David Keogh Cc: Jesper Dangaard Brouer , Daniel Borkmann , Dragos Tatulea , David Woodhouse , netdev@vger.kernel.org, Jakub Kicinski , Paolo Abeni , Eric Dumazet , Alasdair McWilliam , bpf@vger.kernel.org, Nimrod Oren , nh-open-source@amazon.com, linux-kernel@vger.kernel.org, kernel-team@cloudflare.com Subject: Re: [RFC net-next 0/6] net: configurable extra TX headroom for local egress Date: Fri, 6 Nov 2026 20:59:39 +0000 Message-ID: <20261106205939.95366-1-tianyi@cloudflare.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: References: <20261015235335.4162993-1-dkeogh@amazon.com> X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit Hi David, Thanks for the review, and for testing it on x86_64 and arm64. On Fri, Nov 06, 2026 at 07:00:42PM +0000, David Keogh wrote: > Tianyi, you have a second use case for this: an XDP program on a veth > peer. Please describe it here, as it bears directly on the points > raised above. At Cloudflare we run some services each in its own network namespace. A veth pair connects the namespace to the host: veth0 is in the host and veth1 is in the namespace, with an XDP program on veth1. XDP needs XDP_PACKET_HEADROOM (256 bytes) in front of each packet. The packets that the host sends into veth0 have much less: 2 bytes from a UDP socket and 64 bytes from AF_XDP. So veth1 copies each of them into a new buffer before the program runs. Raising needed_headroom on veth0 is not an option. The v1 cover letter has the details. > I suggest you post v1, with patches 1-4 from me and 5-8 from you, and > the cover letter under your own name, since the veth XDP case and the > new measurements are yours. I am happy to post v1 as you suggest. I will fold in the points you listed and post it on the latest net-next. Thanks for the TCP test as well. Thanks, Tianyi