From owner-freebsd-hackers@freebsd.org Mon Apr 26 14:25:00 2021 Return-Path: Delivered-To: freebsd-hackers@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 158B25E2266 for ; Mon, 26 Apr 2021 14:25:00 +0000 (UTC) (envelope-from phk@critter.freebsd.dk) Received: from phk.freebsd.dk (phk.freebsd.dk [130.225.244.222]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4FTRxR0Nchz3RCM for ; Mon, 26 Apr 2021 14:24:58 +0000 (UTC) (envelope-from phk@critter.freebsd.dk) Received: from critter.freebsd.dk (v-critter.freebsd.dk [192.168.55.3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by phk.freebsd.dk (Postfix) with ESMTPS id 762228928F; Mon, 26 Apr 2021 14:24:56 +0000 (UTC) Received: from critter.freebsd.dk (localhost [127.0.0.1]) by critter.freebsd.dk (8.16.1/8.16.1) with ESMTPS id 13QEOupZ076580 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Mon, 26 Apr 2021 14:24:56 GMT (envelope-from phk@critter.freebsd.dk) Received: (from phk@localhost) by critter.freebsd.dk (8.16.1/8.16.1/Submit) id 13QEOtr9076579; Mon, 26 Apr 2021 14:24:55 GMT (envelope-from phk) To: "Rodney W. Grimes" cc: Zhenlei Huang , freebsd-hackers@freebsd.org Subject: Re: Are there any RFCs for address selection for IPv4 In-reply-to: <202104261350.13QDoA0E097896@gndrsh.dnsmgr.net> From: "Poul-Henning Kamp" References: <202104261350.13QDoA0E097896@gndrsh.dnsmgr.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <76577.1619447095.1@critter.freebsd.dk> Date: Mon, 26 Apr 2021 14:24:55 +0000 Message-ID: <76578.1619447095@critter.freebsd.dk> X-Rspamd-Queue-Id: 4FTRxR0Nchz3RCM X-Spamd-Bar: - Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of phk@critter.freebsd.dk designates 130.225.244.222 as permitted sender) smtp.mailfrom=phk@critter.freebsd.dk X-Spamd-Result: default: False [-1.23 / 15.00]; RCVD_TLS_ALL(0.00)[]; RBL_DBL_DONT_QUERY_IPS(0.00)[130.225.244.222:from]; FREEFALL_USER(0.00)[phk]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; TO_DN_SOME(0.00)[]; R_SPF_ALLOW(-0.20)[+mx]; TAGGED_RCPT(0.00)[]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; DMARC_NA(0.00)[freebsd.dk]; SPAMHAUS_ZRD(0.00)[130.225.244.222:from:127.0.2.255]; RCVD_COUNT_THREE(0.00)[3]; TO_MATCH_ENVRCPT_SOME(0.00)[]; NEURAL_SPAM_SHORT(0.77)[0.775]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; FORGED_SENDER(0.30)[phk@phk.freebsd.dk,phk@critter.freebsd.dk]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:1835, ipnet:130.225.0.0/16, country:EU]; FROM_NEQ_ENVFROM(0.00)[phk@phk.freebsd.dk,phk@critter.freebsd.dk]; MAILMAN_DEST(0.00)[freebsd-hackers]; FREEMAIL_CC(0.00)[gmail.com,freebsd.org] X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Technical discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 26 Apr 2021 14:25:00 -0000 -------- Rodney W. Grimes writes: > > Does anybody know why we put a (ipv6)LL on loopback interfaces ? > > I believe someplace in the bowls of all the IPv6 specs this > is a requirement. I could not find it quickly though. I'm not seeing Linux doing it for instance ? > Question: Should we allow a route to have a next hop of a LL(ipv4)? > Reason: RFC3927 2.6.2: > The host MUST NOT send a packet with an IPv4 Link-Local destination > address to any router for forwarding. > > So, arguably, it is a violation to allow the default route to have > a LL next hop for ipv4. For that matter, it is a violation to allow > ANY ipv4 LL address to be the next hop in the routing table(s). You are reading that wrong. It is OK to have a LL as next-hop. It is not OK to send a packet with dst=LL to any next-hop. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.