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 5BB2D38B7AB; Mon, 9 Mar 2026 12:43:45 +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=1773060225; cv=none; b=hos54hiULWFlc10WABVP03+OD/lzvV2Yy3ohkXHi1Bf/Yc2SV4QUJCPJojy8u3np59SBqjfs9TnjfJkuQu0WJH+b+RWyecE6MsvWRTmkvm40OUcJ8VdJfvtD1UvWX/xhBrV7sDQMu+n+ftAfIJK6vXle+K1Y6ksAK5wWeZ7uqBk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773060225; c=relaxed/simple; bh=irtEASAFFHD2A1Q7bmb+zrGm60eMWjCDht/lICODbpc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qkOM7M3i+mA2c9p/x8SyyY0s3Wbjw/I49jw+3hTVXiwr39goyBeab6DEmBIaQ/jM+ndq/K/NDb2b6XzYoaDPVkMfhjNPw5ZW6LLKQM5fHh/c8EqPCrxrFo431mGbrOO9xJI2r3unpv5P93YxM5XDzHB/DMRzNhkuEeSpFaQQu8k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=imKH99KG; 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="imKH99KG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 036F3C4CEF7; Mon, 9 Mar 2026 12:43:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773060225; bh=irtEASAFFHD2A1Q7bmb+zrGm60eMWjCDht/lICODbpc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=imKH99KGYOF+EiwaZPwM2zjULPpAalYXs/1bCM/Fgcn+NAOp5ZvdQh6osNRMQIOft 2hLMeidvMTE7hGyvKQS0+UgE4UFW2z3Yx4pDHOZvqwijjM79W7XKGCdKKdbww1tQn9 e2rrqjs9Wfgpi3p9zWo/CuLsX6q+olqPaz78mwz8qMfbvsWYXiRoEosanyhpxZ3hLe POwt9xWHR7fL5zmT4rGRmGa/r3tT22ADthvsQ/HSJdV/7o8lofGaZyK9amlsIkNC4D TR4CxL/ZDuCVAS0QmNWMI+Q/0cvM+/XqHwdpB994Fi2bZ2WbWYkcgSa6oIvk6zo5Ia aCvugPIFnvn4g== Message-ID: <6c005900-3461-4e3c-a396-b2984735af9b@kernel.org> Date: Mon, 9 Mar 2026 13:43:41 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 00/10 net-next] Convert CONFIG_IPV6 to built-in and remove stubs To: Fernando Fernandez Mancera , netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, dsahern@kernel.org References: <20260309022013.5199-1-fmancera@suse.de> <48ccec3f-dbc8-45c8-afda-e4f7e8f150d6@kernel.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; keydata= xsFNBFVDQq4BEAC6KeLOfFsAvFMBsrCrJ2bCalhPv5+KQF2PS2+iwZI8BpRZoV+Bd5kWvN79 cFgcqTTuNHjAvxtUG8pQgGTHAObYs6xeYJtjUH0ZX6ndJ33FJYf5V3yXqqjcZ30FgHzJCFUu JMp7PSyMPzpUXfU12yfcRYVEMQrmplNZssmYhiTeVicuOOypWugZKVLGNm0IweVCaZ/DJDIH gNbpvVwjcKYrx85m9cBVEBUGaQP6AT7qlVCkrf50v8bofSIyVa2xmubbAwwFA1oxoOusjPIE J3iadrwpFvsZjF5uHAKS+7wHLoW9hVzOnLbX6ajk5Hf8Pb1m+VH/E8bPBNNYKkfTtypTDUCj NYcd27tjnXfG+SDs/EXNUAIRefCyvaRG7oRYF3Ec+2RgQDRnmmjCjoQNbFrJvJkFHlPeHaeS BosGY+XWKydnmsfY7SSnjAzLUGAFhLd/XDVpb1Een2XucPpKvt9ORF+48gy12FA5GduRLhQU vK4tU7ojoem/G23PcowM1CwPurC8sAVsQb9KmwTGh7rVz3ks3w/zfGBy3+WmLg++C2Wct6nM Pd8/6CBVjEWqD06/RjI2AnjIq5fSEH/BIfXXfC68nMp9BZoy3So4ZsbOlBmtAPvMYX6U8VwD TNeBxJu5Ex0Izf1NV9CzC3nNaFUYOY8KfN01X5SExAoVTr09ewARAQABzSVLcnp5c3p0b2Yg S296bG93c2tpIDxrcnprQGtlcm5lbC5vcmc+wsGVBBMBCgA/AhsDBgsJCAcDAgYVCAIJCgsE FgIDAQIeAQIXgBYhBJvQfg4MUfjVlne3VBuTQ307QWKbBQJoF1BKBQkWlnSaAAoJEBuTQ307 QWKbHukP/3t4tRp/bvDnxJfmNdNVn0gv9ep3L39IntPalBFwRKytqeQkzAju0whYWg+R/rwp +r2I1Fzwt7+PTjsnMFlh1AZxGDmP5MFkzVsMnfX1lGiXhYSOMP97XL6R1QSXxaWOpGNCDaUl ajorB0lJDcC0q3xAdwzRConxYVhlgmTrRiD8oLlSCD5baEAt5Zw17UTNDnDGmZQKR0fqLpWy 786Lm5OScb7DjEgcA2PRm17st4UQ1kF0rQHokVaotxRM74PPDB8bCsunlghJl1DRK9s1aSuN hL1Pv9VD8b4dFNvCo7b4hfAANPU67W40AaaGZ3UAfmw+1MYyo4QuAZGKzaP2ukbdCD/DYnqi tJy88XqWtyb4UQWKNoQqGKzlYXdKsldYqrLHGoMvj1UN9XcRtXHST/IaLn72o7j7/h/Ac5EL 8lSUVIG4TYn59NyxxAXa07Wi6zjVL1U11fTnFmE29ALYQEXKBI3KUO1A3p4sQWzU7uRmbuxn naUmm8RbpMcOfa9JjlXCLmQ5IP7Rr5tYZUCkZz08LIfF8UMXwH7OOEX87Y++EkAB+pzKZNNd hwoXulTAgjSy+OiaLtuCys9VdXLZ3Zy314azaCU3BoWgaMV0eAW/+gprWMXQM1lrlzvwlD/k whyy9wGf0AEPpLssLVt9VVxNjo6BIkt6d1pMg6mHsUEVzsFNBFVDXDQBEADNkrQYSREUL4D3 Gws46JEoZ9HEQOKtkrwjrzlw/tCmqVzERRPvz2Xg8n7+HRCrgqnodIYoUh5WsU84N03KlLue MNsWLJBvBaubYN4JuJIdRr4dS4oyF1/fQAQPHh8Thpiz0SAZFx6iWKB7Qrz3OrGCjTPcW6ei OMheesVS5hxietSmlin+SilmIAPZHx7n242u6kdHOh+/SyLImKn/dh9RzatVpUKbv34eP1wA GldWsRxbf3WP9pFNObSzI/Bo3kA89Xx2rO2roC+Gq4LeHvo7ptzcLcrqaHUAcZ3CgFG88CnA 6z6lBZn0WyewEcPOPdcUB2Q7D/NiUY+HDiV99rAYPJztjeTrBSTnHeSBPb+qn5ZZGQwIdUW9 YegxWKvXXHTwB5eMzo/RB6vffwqcnHDoe0q7VgzRRZJwpi6aMIXLfeWZ5Wrwaw2zldFuO4Dt 91pFzBSOIpeMtfgb/Pfe/a1WJ/GgaIRIBE+NUqckM+3zJHGmVPqJP/h2Iwv6nw8U+7Yyl6gU BLHFTg2hYnLFJI4Xjg+AX1hHFVKmvl3VBHIsBv0oDcsQWXqY+NaFahT0lRPjYtrTa1v3tem/ JoFzZ4B0p27K+qQCF2R96hVvuEyjzBmdq2esyE6zIqftdo4MOJho8uctOiWbwNNq2U9pPWmu 4vXVFBYIGmpyNPYzRm0QPwARAQABwsF8BBgBCgAmAhsMFiEEm9B+DgxR+NWWd7dUG5NDfTtB YpsFAmgXUF8FCRaWWyoACgkQG5NDfTtBYptO0w//dlXJs5/42hAXKsk+PDg3wyEFb4NpyA1v qmx7SfAzk9Hf6lWwU1O6AbqNMbh6PjEwadKUk1m04S7EjdQLsj/MBSgoQtCT3MDmWUUtHZd5 RYIPnPq3WVB47GtuO6/u375tsxhtf7vt95QSYJwCB+ZUgo4T+FV4hquZ4AsRkbgavtIzQisg Dgv76tnEv3YHV8Jn9mi/Bu0FURF+5kpdMfgo1sq6RXNQ//TVf8yFgRtTUdXxW/qHjlYURrm2 H4kutobVEIxiyu6m05q3e9eZB/TaMMNVORx+1kM3j7f0rwtEYUFzY1ygQfpcMDPl7pRYoJjB dSsm0ZuzDaCwaxg2t8hqQJBzJCezTOIkjHUsWAK+tEbU4Z4SnNpCyM3fBqsgYdJxjyC/tWVT AQ18NRLtPw7tK1rdcwCl0GFQHwSwk5pDpz1NH40e6lU+NcXSeiqkDDRkHlftKPV/dV+lQXiu jWt87ecuHlpL3uuQ0ZZNWqHgZoQLXoqC2ZV5KrtKWb/jyiFX/sxSrodALf0zf+tfHv0FZWT2 zHjUqd0t4njD/UOsuIMOQn4Ig0SdivYPfZukb5cdasKJukG1NOpbW7yRNivaCnfZz6dTawXw XRIV/KDsHQiyVxKvN73bThKhONkcX2LWuD928tAR6XMM2G5ovxLe09vuOzzfTWQDsm++9UKF a/A= In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 09/03/2026 12:38, Fernando Fernandez Mancera wrote: > On 3/9/26 11:22 AM, Krzysztof Kozlowski wrote: >> On 09/03/2026 03:19, Fernando Fernandez Mancera wrote: >>> Historically, the Linux kernel has supported compiling the IPv6 stack as >>> a loadable module. While this made sense in the early days of IPv6 >>> adoption, modern deployments and distributions overwhelmingly either >>> build IPv6 directly into the kernel (CONFIG_IPV6=y) or disable it >>> entirely (CONFIG_IPV6=n). The modular IPv6 use-case provides little to >>> no practical benefit today. >> >> It does. We all use generic kernels, thus it is one configuration for >> all boards and some setups have IPv6 and some not. The ones without IPv6 >> just don't use that module. >> > > While I understand this, I would like to clarify that IMHO IPv6 isn't a > secondary protocol and it is fundamental to modern networking. This is Not for end user devices. None of my devices - neither routers, nor embedded boards, nor mobile phone from 5G provider - receive IPv6 address, thus for them it is not fundamental. I agree it is fundamental for your cloud machines and network backbone which you are targeting, but this patchset completely ignores other users calling their use-cases "little practical benefit"! Try running Amiga machine... There is no even bloatometer stats for these defconfigs so we can see the impact. > why I believe it should be built-in by default. Currently OpenWRT, > Debian ARM and others already ships the kernel with CONFIG_IPV6=y. I > know that Alpine and Yocto doesn't do that for arm64. Maybe there are other reasons why distro should not choose it as module (like module load calls on ipv6 packets) but that was not explained here. Arch Linux Rpi kernel on arm64 has IPV6=6 and the module itself is 650 kB. That's noticeable for smaller arm64 boards. For arm it would be even more noticeable as some have 256 MB RAM like first Rpi. > > I guess the most critical one here is Yocto but if the developer of the > embedded device is sure they won't use IPv6 at all, they should turn it off. > > At the same time, Alpine ships software that enable IPV6 and is > frequently loaded as a module. So the only remaining concern would be > the boot partition size. I don't really have a solution for that problem. > > I think that the infrastructure for allowing IPV6=m is bug-prone and it > impacts performance. Forcing the use of indirect function calls in core > networking, Netfilter or BPF datapaths seems like a heavy tax to me. > >> Also, with these generic kernels (so again all machines are using same >> ones, e.g. distro) users can easily blacklist the module. >> > > FWIW; users can still boot with kernel command line parameter > ipv6.disable=1 and then IPV6 will be administratively disabled. It's not the same. You enabled it on amiga_defconfig and do you understand what sort of machine is that? The newest have 16 MB RAM, many much less like 2 MB, and ipv6 module on m68k is 400 kB, so pretty significant change. Best regards, Krzysztof