From nobody Wed Sep 15 15:57:34 2021 X-Original-To: freebsd-net@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 1ECA917BFEFB for ; Wed, 15 Sep 2021 15:57:47 +0000 (UTC) (envelope-from bzeeb-lists@lists.zabbadoz.net) Received: from mx1.sbone.de (mx1.sbone.de [IPv6:2a01:4f8:13b:39f::9f:25]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mx1.sbone.de", Issuer "SBone.DE" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4H8lGy0G2sz3DFQ; Wed, 15 Sep 2021 15:57:46 +0000 (UTC) (envelope-from bzeeb-lists@lists.zabbadoz.net) Received: from mail.sbone.de (mail.sbone.de [IPv6:fde9:577b:c1a9:31::2013:587]) (using TLSv1 with cipher ADH-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by mx1.sbone.de (Postfix) with ESMTPS id 4DA808D4A21B; Wed, 15 Sep 2021 15:57:38 +0000 (UTC) Received: from content-filter.sbone.de (content-filter.sbone.de [IPv6:fde9:577b:c1a9:31::2013:2742]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.sbone.de (Postfix) with ESMTPS id 63A03E707C7; Wed, 15 Sep 2021 15:57:37 +0000 (UTC) X-Virus-Scanned: amavisd-new at sbone.de Received: from mail.sbone.de ([IPv6:fde9:577b:c1a9:31::2013:587]) by content-filter.sbone.de (content-filter.sbone.de [fde9:577b:c1a9:31::2013:2742]) (amavisd-new, port 10024) with ESMTP id V-XHNnqlfG9V; Wed, 15 Sep 2021 15:57:35 +0000 (UTC) Received: from [169.254.86.56] (unknown [IPv6:fde9:577b:c1a9:4902:1c61:97b8:bcbc:a159]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.sbone.de (Postfix) with ESMTPSA id BAA99E707C6; Wed, 15 Sep 2021 15:57:35 +0000 (UTC) From: "Bjoern A. Zeeb" To: "Mike Karels" Cc: freebsd-net@freebsd.org Subject: Re: change to deprecate broadcast on host 0 of a subnet Date: Wed, 15 Sep 2021 15:57:34 +0000 X-Mailer: MailMate (2.0BETAr6151) Message-ID: In-Reply-To: <202109121525.18CFPuZM067614@mail.karels.net> References: <202109121525.18CFPuZM067614@mail.karels.net> List-Id: Networking and TCP/IP with FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-net List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-net@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; format=flowed X-Rspamd-Queue-Id: 4H8lGy0G2sz3DFQ X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of bzeeb-lists@lists.zabbadoz.net designates 2a01:4f8:13b:39f::9f:25 as permitted sender) smtp.mailfrom=bzeeb-lists@lists.zabbadoz.net X-Spamd-Result: default: False [-3.30 / 15.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; RCVD_COUNT_FIVE(0.00)[5]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; R_SPF_ALLOW(-0.20)[+ip6:2a01:4f8:13b:39f::9f:25]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[zabbadoz.net]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-1.00)[-1.000]; RCPT_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:24940, ipnet:2a01:4f8::/32, country:DE]; RCVD_TLS_LAST(0.00)[]; MID_RHS_MATCH_FROM(0.00)[] X-ThisMailContainsUnwantedMimeParts: N On 12 Sep 2021, at 15:25, Mike Karels wrote: > Long ago (4.2BSD), the IP broadcast address was the lowest address on > a > network, the one with a host part of 0. In RFC1122, the broadcast > address > was standardized using a host part of all ones. 4.3BSD changed its > default, and made the broadcast address settable with ifconfig. > However, > FreeBSD *still* broadcasts packets sent to the lowest address on a > subnet. > > I have a change in review to stop broadcasting the lowest address on a > subnet by default, but added a sysctl to revert to the current > behavior. > I really doubt that anyone is still using a 0-based broadcast address. > This change allows host 0 on a subnet to be used as an assigned host > address, as long as the systems on that network support it (including > routers). Linux already has this change. > > The review is https://reviews.freebsd.org/D31861. See also > https:/datatracker.ietf.org/draft-schoen-intarea-lowest-address/ and I think it is: https://datatracker.ietf.org/doc/draft-schoen-intarea-lowest-address/ > some of the discussion in https://reviews.freebsd.org/D19316. > > Comments are welcome on the review. I will wait a couple of days > for comments before proceeding. I am also interested in comments on > whether this should be MFC'ed to 13-stable after a suitable delay. I would have even gone one further step back and put this under EXPERIMENTAL in HEAD and wait until this draft has gone anywhere but with your sysctl I think it is fine (from reading the email not the recent review). I would prefer if the current behaviour stayed default (would also MFC better) and then flip if this will indeed go anywhere. My personal note on this is: it is riding a dead horse, driven by economics, and it feels 30 year too late to still do this and change this historic behaviour. /bz