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 E2690219E93; Fri, 28 Mar 2025 11:39:43 +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=1743161984; cv=none; b=PieYllGKkFx7diuKS020o5hkJPnIK5jtvdIfCQXhgzgV/Hnq65aWUfOAbNVWerdl/FQkx2ZPrajw6cEH5supv58EuPJDbPLApEztUtErq4Eso2hY9FgbiGKyOizQQmJ84NsfxcbyDHLh9ZToAnaL/ewXndzt3cXYpqoO2ufp5+s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743161984; c=relaxed/simple; bh=VpclY77LC2UScTUAvSmsEmH/yJZOtBuiJg7uhPWchSA=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=rZjWwktc2eQZ/DrODTQ2Xf3e588mRWBh2Mgw75TibV66GDQfKoYlja8/zFH7bb98o3MZR5cz4/ImU3w+F8xu7QYwmIDVY9NGdmOkgIcoL8aKjyVUL2Bu0Vz+tNz855BXsr9Kt4IIUL0tiym1BD6ieAVlmGfCvwECvuyAkGt01x8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=od0lmCZE; 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="od0lmCZE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9EBBC4CEE4; Fri, 28 Mar 2025 11:39:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743161983; bh=VpclY77LC2UScTUAvSmsEmH/yJZOtBuiJg7uhPWchSA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=od0lmCZEqeq2uaZAtSxzMBD16GJUjxtNFigaGLkpuhGZQTG59fUuRB4e/5iW2AZc8 wXxjNMcbgGI7rQYdQ+nYl9Agi8fUTJVnfTdkXhlBq/rB2qZwX322gvoyWgWW7wXErh uNU8WaDEgpDId/Aste1gXn7/8+NZsQDGWHgOymIqn4SH1e5YMDziquqUWlDJll3bpF wv4vyKKPWNmiTkhCrYEnVR7qjG8p+eebGSo44+xPUSsnhH7p/WLseo30U1f6G9GORI WMFDlJhYsdX1C0b83xju02cA9nI2ZP63VBJKELG4Nql2MRrTuCWddHpVgsWCBA9RlX XLkv9kMyffk3A== Date: Fri, 28 Mar 2025 04:39:41 -0700 From: Jakub Kicinski To: "Jiayuan Chen" Cc: "Willem de Bruijn" , netdev@vger.kernel.org, jasowang@redhat.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, ast@kernel.org, daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com, linux-kernel@vger.kernel.org, syzbot+0e6ddb1ef80986bdfe64@syzkaller.appspotmail.com, bpf@vger.kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, kpsingh@kernel.org, jolsa@kernel.org Subject: Re: [PATCH net v1] net: Fix tuntap uninitialized value Message-ID: <20250328043941.085de23b@kernel.org> In-Reply-To: <17a3bc7273fac6a2e647a6864212510b37b96ab2@linux.dev> References: <20250327134122.399874-1-jiayuan.chen@linux.dev> <67e5be3c65de3_10636329488@willemb.c.googlers.com.notmuch> <17a3bc7273fac6a2e647a6864212510b37b96ab2@linux.dev> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 28 Mar 2025 09:15:53 +0000 Jiayuan Chen wrote: > I'm wondering if we can directly perform a memset in bpf_xdp_adjust_head > when users execute an expand header (offset < 0). Same situation happens in bpf_xdp_adjust_meta(), but I'm pretty sure this was discussed and considered too high cost for XDP. Could you find the old discussions and double check the arguments made back then? Opinions may have changed but let's make sure we're not missing anything. And performance numbers would be good to have since the main reason this isn't done today was perf.