From nobody Thu Apr 2 00:08:15 2026 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 9133238643E; Wed, 1 Apr 2026 07:45:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775029546; cv=none; b=dCRrc8gmOT4oXHzxmVgOMVteIpES5/nAUSlGXVDJftgaw3atZ5cyaY5C/WYe6dvqODhl+F95/LJgloSzl+Z196khTuX0Gs0OT3tRPJYc6tIzSdQ+HyxWP0cu2YPLdsMeZtl8mpdL89yTvqzXO68D2Z7fjK4gfKJ+xxzJjApb5Os= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775029546; c=relaxed/simple; bh=9R+JVXf4BtoLSJ29Oe17bA2hZ9tUe54L63YtyNAu4Ys=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=h7fCMqQODH0kLX20RoRiiU3N6lgvb0cK63XmpibI8IrSbAxEkyGiHFXowjAgSfBtmAcYHIlDEaamuuaUp75gdf9DOS11qdQXxWDvDPEgzO2hJaGQayRFbDljn/Skmczki330V5gpWPdCx4pRwojLodYRKjHF5Kpk6zrvU7VnzWU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=desiato.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=cGXZEtGH; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=desiato.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="cGXZEtGH" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:To: From:Reply-To:Cc:Content-ID:Content-Description; bh=5iG19Rn9VazMkVS9llniL6PBW1JOyaflEHOOD98tRZo=; b=cGXZEtGHD9fH3O9CZN4XP5sxfi H8mHOXi9NQOmDZi4ip1Y6phk85JdqIAuKBx+xqD+WQReEjlWnndfUL9yz3LdeD4sCBOas46aF6W7I bcK3LJaLrEDUmYK/7fg7uR0BRH2pbgTxQ+v5yl8oq1vkTYgnLYVTxyv/FeydxPJBssY88jdSgioW1 z/wT7xqPFDUMM4Dl+GgRna90n+n9hKzCX0Dl3jB1kbs1WJj/8I/LUPqb2AVjuUjpFAPdQxAK1Qbdf DA9oYeheAcq/IUqUFSNZDQ4DHMmZs7leRaYMlDeIgUiYAuD9OTc1d7rGbKsGbXvAbd4nM7pX41kUC poZKL3SA==; Received: from [2001:8b0:10b:1::425] (helo=i7.infradead.org) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1w7qGN-0000000HLQN-0BwS; Wed, 01 Apr 2026 07:45:19 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1w7qGM-00000007xe8-1pgr; Wed, 01 Apr 2026 08:45:18 +0100 From: David Woodhouse To: Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Mark Bloch , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Nikolay Aleksandrov , Ido Schimmel , Martin KaFai Lau , Daniel Borkmann , John Fastabend , Stanislav Fomichev , Alexei Starovoitov , Andrii Nakryiko , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Hao Luo , Jiri Olsa , Kuniyuki Iwashima , Willem de Bruijn , David Ahern , Neal Cardwell , Johannes Berg , Pablo Neira Ayuso , Florian Westphal , Phil Sutter , Guillaume Nault , David Woodhouse , Kees Cook , Alexei Lazar , Gal Pressman , Paul Moore , netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, oss-drivers@corigine.com, bridge@lists.linux.dev, bpf@vger.kernel.org, linux-wireless@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, torvalds@linux-foundation.org, jon.maddog.hall@gmail.com Subject: [PATCH 2/6] net: Add CONFIG_LEGACY_IP option Date: Wed, 1 Apr 2026 08:44:16 +0100 Message-ID: <20260401074509.1897527-3-dwmw2@infradead.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260401074509.1897527-1-dwmw2@infradead.org> References: <20260401074509.1897527-1-dwmw2@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html From: David Woodhouse Add a new CONFIG_LEGACY_IP boolean option under CONFIG_INET that will gate Legacy IP functionality. When disabled, the kernel will not register the AF_INET socket family, IPv4 packet handler, ARP, or IPv4 routing, while the shared TCP/UDP/INET socket infrastructure remains available for IPv6. This is the first step toward making Legacy IP optional. The option defaults to y and currently has no effect =E2=80=94 subsequent patches will= use it to guard IPv4 entry points. Signed-off-by: David Woodhouse --- net/ipv4/Kconfig | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig index df922f9f5289..aef2c5349e62 100644 --- a/net/ipv4/Kconfig +++ b/net/ipv4/Kconfig @@ -2,6 +2,17 @@ # # IP configuration # +config LEGACY_IP + bool "The IPv4 protocol (Legacy IP)" + help + Support for IP version 4 (IPv4). + + Legacy IP is the protocol used by the early ARPANET, before IPv6 + was standardised in the final decade of the 1900s. It should only + be necessary these days to interoperate with legacy networks. + + If unsure, say N. + config IP_MULTICAST bool "IP: multicasting" help --=20 2.51.0