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 BFF981B4F09; Mon, 9 Mar 2026 13:02:49 +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=1773061369; cv=none; b=rF1KTz6B1672gNqGJVdGQzVEwFrbVczSsXvdylteUvM+EMknaNqhT3kcYSqwJQcRJMUZt+hSLnbZyzVxD8GvCRBmln1Tz0yA9OK8zrTJbV8Y4/8qB+e6rK1aAMoG6pWfJsq+9yI4m+V5BHdsaK3RJLzoSxsTgezYwAMSorbD3cE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773061369; c=relaxed/simple; bh=8DNFqs9BqyWbsZij3jgAnNR3Kg6pkLFQFJhfdOuSUtA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=p1KguEeWGQxtIaJC5EgZeBUHfARz/5yAZjXy7qf2jY4erv+0W/QdQes92JAkGuAQWAr3J3eHw8BMd6pgBx7Lv0HLw67mUq/7wdUgfZcmDjHKKjeX1Cj5H6hN+kUVtW9f4LapGuhU1tyLftF+lWzMP0WxEOmGf+824zTSOPHuugM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BCjAa/qx; 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="BCjAa/qx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 433E6C4CEF7; Mon, 9 Mar 2026 13:02:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773061369; bh=8DNFqs9BqyWbsZij3jgAnNR3Kg6pkLFQFJhfdOuSUtA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=BCjAa/qxra1Sa1Hn2PhEc7IljzEUxXbuDPwi7EdNmLZr1ctd7lO8oep6GHv7aL592 co3fi/w8tqJlw0H0c0w57HGLcAPT0j2RBnkW/cVDUuF7RMu8XYb3Yb31CcRqnDdpAZ LxM9IKzmY5nzU9Zog8E8xHzrFKOtKoVn3YcIMj3quOHGDMfzUEvQKSn9OvQnPK/ewV hYqVO5sXG1NV7FUfxrsdMOEEd5xjKem59lcH3arzAR1I0Bg7qhVU9WAMzwSQZbIzsY jkGlUHzHeMlSOVhn/PlUQjjqOAw6HKCIZqIGt0qpgLZFjOWZvLzu8VcO4sp0BWXtOI kEZanN/flpcNA== Message-ID: <4e3cd289-2b7a-4f64-99f6-05eb9d67c0fc@kernel.org> Date: Mon, 9 Mar 2026 14:02:45 +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: Daniel Borkmann , 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> <6c005900-3461-4e3c-a396-b2984735af9b@kernel.org> <51102620-fb8a-467e-9144-786d1fe27e31@iogearbox.net> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 09/03/2026 13:58, Daniel Borkmann wrote: > On 3/9/26 1:43 PM, Krzysztof Kozlowski wrote: >> 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. > > If that is the case for them, then they should just CONFIG_IPV6=n. That's not a question to me. Look what I wrote: "We all use generic kernels" - in a meaning of generic kernel, with generic defconfig built once serving every machine. > >> 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... > > Are you talking about [0]? That's legacy hardware and in this case just Dunno what is legacy there... > disable IPv6 altogether, why would you still prefer to have it as a module? That's not a question to me - someone added it as a module now. The author here changes it to built-in. > > [0] https://en.wikipedia.org/wiki/Amiga > >> 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. > > You are arguing that these will never be able to migrate to an IPv6 world > given their memory is too small? No. I argue that they do not need IPv6 in many cases, thus use-case of IPV6=m is perfectly valid. The entire discussion here started with "The modular IPv6 use-case provides little to no practical benefit today." and this is clearly false. I brought you already few arguments of valid use case today. > >>> 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. > > If IPv6 is not relevant for amiga_defconfig presumably it should just be > set to CONFIG_IPV6=n? It might be relevant to some, but this makes it relevant to everyone on Amiga. There is a reason why kernel supports modules or do you suggest "modules provide little to no practical benefit today" and let's just have everything built-in or disabled. Best regards, Krzysztof