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Tue, 10 Mar 2026 15:58:36 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: Aes-ty0OVaaR Date: Tue, 10 Mar 2026 20:58:15 +0100 From: "Arnd Bergmann" To: =?UTF-8?Q?Kolbj=C3=B8rn_Barmen?= , "Krzysztof Kozlowski" Cc: "Fernando Fernandez Mancera" , Netdev , linux-kernel@vger.kernel.org, "Geert Uytterhoeven" , "Jason Gunthorpe" , "Leon Romanovsky" , "Selvin Xavier" , "Andrew Lunn" , "David S . Miller" , "Eric Dumazet" , "Jakub Kicinski" , "Paolo Abeni" , "Ido Schimmel" , "Petr Machata" , "Simon Horman" , "Saurav Kashyap" , "Javed Hasan" , "maintainer:BROADCOM BNX2FC 10 GIGABIT FCOE DRIVER" , "James E . J . Bottomley" , "Martin K. Petersen" , "Nilesh Javali" , "Manish Rangankar" , "Varun Prakash" , "Alexander Aring" , "David Teigland" , "Andreas Gruenbacher" , "Nikolay Aleksandrov" , "David Ahern" , "Pablo Neira Ayuso" , "Florian Westphal" , "Phil Sutter" , "David Howells" , "Marc Dionne" , "Marcelo Ricardo Leitner" , "Xin Long" , "Jon Maloy" , "Krzysztof Kozlowski" , "Bjorn Andersson" , "Dmitry Baryshkov" , "Eric Biggers" , "Michal Simek" , "Luca Weiss" , "Sven Peter" , "Lad, Prabhakar" , "Kuninori Morimoto" , "Andrew Morton" , "David Gow" , "Herbert Xu" , "Ryota Sakamoto" , "Kuniyuki Iwashima" , "Kir Chou" , "Kuan-Wei Chiu" , "Vikas Gupta" , "Bhargava Marreddy" , "Rajashekar Hudumula" , =?UTF-8?Q?Markus_Bl=C3=B6chl?= , "open list:M68K ARCHITECTURE" , "open list:INFINIBAND SUBSYSTEM" , "open list:NETRONOME ETHERNET DRIVERS" , "open list:BROADCOM BNX2FC 10 GIGABIT FCOE DRIVER" , "open list:DISTRIBUTED LOCK MANAGER (DLM)" , "open list:ETHERNET BRIDGE" , "open list:NETFILTER" , "open list:NETFILTER" , "open list:RXRPC SOCKETS (AF_RXRPC)" , "open list:SCTP PROTOCOL" , "open list:TIPC NETWORK LAYER" Message-Id: <5c4b6043-a484-479d-83bc-a86ecdb8f810@app.fastmail.com> In-Reply-To: References: <20260309022013.5199-1-fmancera@suse.de> <20260309022013.5199-2-fmancera@suse.de> <01a4936f-77cd-4c60-a1be-cabec872a2bb@kernel.org> Subject: Re: [PATCH 01/10 net-next] ipv6: convert CONFIG_IPV6 to built-in only and clean up Kconfigs Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Tue, Mar 10, 2026, at 20:40, Kolbj=C3=B8rn Barmen wrote: > On Mon, 9 Mar 2026, Krzysztof Kozlowski wrote: >> On 09/03/2026 03:19, Fernando Fernandez Mancera wrote: >> >> It must stay module for me. Alternatively, drop it, but then some use= rs >> will be really affected. > > I agree. If anything I would prefer to see IPv4 be made optional (and > modular) as well, and not as something IPv6 depends on, it's (AFAIK) > impossible today to build an IPv6-only Linux kernel.=20 My first feeling was that this is a bad idea as well. On the other hand I found that the default changed from =3Dm to -y over 10 years ago, all recent distros listed in https://github.com/nyrahul/linux-kernel-configs use that default (the only two exceptions are board specific builds of Debian and Ubuntu for linux-5.x). The list does not include openwrt though, and I know that in previous releases, there was an optional kmod-ipv6 package that could be left out of an install without rebuilding the kernel. Configurations under 128MB are only partially supported there these days, so maybe it's no longer important for openwrt either, but it would be good to get a confirmation from someone doing the packaging. For optional IPv4 support, I would expect that it's possible to make it a loadable module, with a significant amount of work and little benefit. Loading an ipv6 module without also loading ipv4 sounds completely unrealistic though, given the way the code is structured today. Arnd