From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B06A7C73C66 for ; Sun, 14 Jul 2019 03:58:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 80EC52053B for ; Sun, 14 Jul 2019 03:58:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Vb4V+Q2r" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728208AbfGND6D (ORCPT ); Sat, 13 Jul 2019 23:58:03 -0400 Received: from mail-yw1-f68.google.com ([209.85.161.68]:39439 "EHLO mail-yw1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728009AbfGND6D (ORCPT ); Sat, 13 Jul 2019 23:58:03 -0400 Received: by mail-yw1-f68.google.com with SMTP id x74so6317917ywx.6 for ; Sat, 13 Jul 2019 20:58:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=bdMIhDBdVNcvCSBNvQXpoSmrS4IyNeg0f/UUKfcyc1Y=; b=Vb4V+Q2rmU0ayZFsAnMF/xjDaFk1AqllI6ljdul/YG5ITQibZP4CYA7Unv0zdSdmHS tdIN88OeJKBcmVsJA93I3J65GJO3wWo6Pz8Lvlarns2mhd2sYd3XVrhdirdx89LfGs69 HAvETivdrg9qbERxfRFrQ2bxvs2R578rekDUPduhMQl6rOxlZJONCaQBH24pHLcB5Eh3 6VxUC13Qj3grP8/R7GW5pVfNSA37ueiUduzCQUSJnjwIMzpdyLIhvEQxugKO3OU16iM/ skHc/3p2grvjCIVDJELm8OCs9Mj1v98/7+V8dxkYmIsix27AnxSBYYGNYKQeCe0Oo6pf GGLw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=bdMIhDBdVNcvCSBNvQXpoSmrS4IyNeg0f/UUKfcyc1Y=; b=Gi7lk2W4ePEjZQS52e/uHgfnlYPl0tSTTpthPy2+iva1dl2MSkqgKfy6AwPFleLWmt dtMLuO7mkRSo668PAJeqGEK3UlndVcjJF3rxgHnzwDDbGu2DMETfx7k6WwxTgDuguVWy RWT+0YCrPoYTKFVF4Vqm97sMRSEPeh1GDYi/tqCqBzDechpR1gslVr+a0XL+KTCLysdy KrziY/TO3i+EPPrcjz1LoeCEdqmYRsx2w2wZoikUc8hW7WscdZXD+7AbWfnWxEj7uDAH sZb+iCTz0NX10NXNZZHBkNdM2dcQf5xAZZ8y9CS1yClmcJfaDHqw5VpLr8rH/W0BpStq PNng== X-Gm-Message-State: APjAAAXzKMimy4c7eRvc9g1BPn7AOSMjvPQDsVF5HetR57pAi9aL0aeR rhcb0ybejYoCBdH7/B2NGoHPHTOG7Vt2qT0p1ssHZQ== X-Google-Smtp-Source: APXvYqys1x7u/g0NVzfVDDUD27Q2ksVy7Z9Ovi4YcCdHSZT0BeNRlFT8TZPJG79V32TuNQZcyMKLQz8XYLfqrdJ2vXY= X-Received: by 2002:a81:57d0:: with SMTP id l199mr11614165ywb.179.1563076682115; Sat, 13 Jul 2019 20:58:02 -0700 (PDT) MIME-Version: 1.0 References: <1561223254-13589-1-git-send-email-dave.taht@gmail.com> <1561223254-13589-2-git-send-email-dave.taht@gmail.com> <20190626.132003.50827799670386389.davem@davemloft.net> In-Reply-To: <20190626.132003.50827799670386389.davem@davemloft.net> From: Paul Marks Date: Sat, 13 Jul 2019 20:57:50 -0700 Message-ID: Subject: Re: [PATCH net-next 1/1] Allow 0.0.0.0/8 as a valid address range To: David Miller Cc: dave.taht@gmail.com, netdev@vger.kernel.org, gnu@toad.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Jun 26, 2019 at 1:20 PM David Miller wrote: > > From: Dave Taht > Date: Sat, 22 Jun 2019 10:07:34 -0700 > > > The longstanding prohibition against using 0.0.0.0/8 dates back > > to two issues with the early internet. > > > > There was an interoperability problem with BSD 4.2 in 1984, fixed in > > BSD 4.3 in 1986. BSD 4.2 has long since been retired. > > > > Secondly, addresses of the form 0.x.y.z were initially defined only as > > a source address in an ICMP datagram, indicating "node number x.y.z on > > this IPv4 network", by nodes that know their address on their local > > network, but do not yet know their network prefix, in RFC0792 (page > > 19). This usage of 0.x.y.z was later repealed in RFC1122 (section > > 3.2.2.7), because the original ICMP-based mechanism for learning the > > network prefix was unworkable on many networks such as Ethernet (which > > have longer addresses that would not fit into the 24 "node number" > > bits). Modern networks use reverse ARP (RFC0903) or BOOTP (RFC0951) > > or DHCP (RFC2131) to find their full 32-bit address and CIDR netmask > > (and other parameters such as default gateways). 0.x.y.z has had > > 16,777,215 addresses in 0.0.0.0/8 space left unused and reserved for > > future use, since 1989. > > > > This patch allows for these 16m new IPv4 addresses to appear within > > a box or on the wire. Layer 2 switches don't care. > > > > 0.0.0.0/32 is still prohibited, of course. > > > > Signed-off-by: Dave Taht > > Signed-off-by: John Gilmore > > Acked-by: Toke H=C3=B8iland-J=C3=B8rgensen > > Applied, thanks for following up on this. This breaks an undocumented feature of Linux: $ telnet 0.0.0.1 22 Trying 0.0.0.1... telnet: Unable to connect to remote host: Invalid argument It's sometimes useful to put 0.x.x.x in command-line flags, /etc/hosts, or other config files, because it forces connect() to fail immediately, instead of sending packets and waiting for a timeout. Given that this has been user-visible for decades, is it a good idea to pull out the rug?