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 40B9A2690C0; Mon, 16 Feb 2026 12:18:57 +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=1771244337; cv=none; b=e9Pe3bXo9XBeHPexMokiF3Sx3ANwE20/BRo3APPRnZ1ZzIKUPLekFg7yjID5iEhjKe3J06Dgf9NdZsDojmivvsSzNtxaQS7iTwGpEg7JiJw/I3QcbampDxS1JJhXHT5IrHmp0nfdFJ13PRntpNcm2tuHcOncdvYg8EaPDrWw4Ic= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771244337; c=relaxed/simple; bh=Hr6sWNozHcIqkYyQhJ753UqohgXVIZtkIn4+7uzTfok=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=s4tLapRrBT9ND4mBdh3ZfugNhinOD3f6jh7OzSOEEwmQbAp01ALziAJUeUGmShJ/16etR2WPeYgqEYYOECQwNvwyJwsb3zVWTb0cvbdxCp3TG8nQNAfYJ++91gAckfWe5t/KjuOWGgWOXoHGGOu/9S4ay/QlGvmIPPbPOL21I7k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iydi1NuJ; 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="iydi1NuJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E0117C116C6; Mon, 16 Feb 2026 12:18:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771244337; bh=Hr6sWNozHcIqkYyQhJ753UqohgXVIZtkIn4+7uzTfok=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=iydi1NuJLyQmwfBLduz7qcgfJ0i7MIIkdgYNPFV/pPY3E6fq+phL/izkA+oZRN1YM +JzJL5EdfN/VQ8DkN9hUUwbj/POiQZTJFv1P31OCBkIQLW9OmGDOGXxtvdL0H9Ns2w 1RqVEX3+jQ7vBIu5Js2g+ZuP6pwVytZZYQINQgZCyHZfKm8fBMQhKUvzAoxwKKTwKE pL2jD6TxCf6JPAV2XdVl7K8kZgCuEDes5+ryH6xjLFjTjX27e6fTGRqXINk4eLJQKp QU+fFHD3aIfQXd7713p+Dz0Ciu+WX2UY+VmzdOmV6e9ulTSiyNz6o69WJNGSBDRERO 6/9/X7M3HKvvg== Date: Mon, 16 Feb 2026 12:18:51 +0000 From: Simon Horman To: Dimitri Daskalakis Cc: "David S . Miller" , Alexander Duyck , Jakub Kicinski , Eric Dumazet , Paolo Abeni , Andrew Lunn , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Stanislav Fomichev , Mohsin Bashir , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH net] eth: fbnic: Add validation for MTU changes Message-ID: References: <20260214171949.772493-1-dimitri.daskalakis1@gmail.com> 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-Disposition: inline In-Reply-To: <20260214171949.772493-1-dimitri.daskalakis1@gmail.com> On Sat, Feb 14, 2026 at 09:19:49AM -0800, Dimitri Daskalakis wrote: > Increasing the MTU beyond the HDS threshold causes the hardware to > fragment packets across multiple buffers. If a single-buffer XDP program > is attached, the driver will drop all multi-frag frames. While we can't > prevent a remote sender from sending non-TCP packets larger than the MTU, > this will prevent users from inadvertently breaking new TCP streams. > > Traditionally, drivers supported XDP with MTU less than 4Kb > (packet per page). Fbnic currently prevents attaching XDP when MTU is too high. > But it does not prevent increasing MTU after XDP is attached. > > Fixes: 1b0a3950dbd4 ("eth: fbnic: Add XDP pass, drop, abort support") > Signed-off-by: Jakub Kicinski > Signed-off-by: Dimitri Daskalakis Reviewed-by: Simon Horman