IETF Logo Mail Archive

Re: [Emailcore] Ticket #92: CNAME handling in “5.1. Locating the Target Host” (rfc5321bis)

John Levine <johnl@taugh.com> Tue, 19 March 2024 17:15 UTC

Return-Path: <johnl@iecc.com>
X-Original-To: emailcore@ietfa.amsl.com
Delivered-To: emailcore@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 2200AC14F699 for <emailcore@ietfa.amsl.com>; Tue, 19 Mar 2024 10:15:55 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.858
X-Spam-Level:
X-Spam-Status: No, score=-1.858 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HEADER_FROM_DIFFERENT_DOMAINS=0.249, RCVD_IN_ZEN_BLOCKED_OPENDNS=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01, URIBL_BLOCKED=0.001, URIBL_DBL_BLOCKED_OPENDNS=0.001, URIBL_ZEN_BLOCKED_OPENDNS=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=iecc.com header.b="mAt7LoDs"; dkim=pass (2048-bit key) header.d=taugh.com header.b="UUHIQL5d"
Received: from mail.ietf.org ([50.223.129.194]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 8fH_f0BtPF9S for <emailcore@ietfa.amsl.com>; Tue, 19 Mar 2024 10:15:50 -0700 (PDT)
Received: from gal.iecc.com (gal.iecc.com [IPv6:2001:470:1f07:1126:0:43:6f73:7461]) (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 ietfa.amsl.com (Postfix) with ESMTPS id 38AF5C14F6AD for <emailcore@ietf.org>; Tue, 19 Mar 2024 10:15:49 -0700 (PDT)
Received: (qmail 102 invoked from network); 19 Mar 2024 17:15:47 -0000
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed; d=iecc.com; h=date:message-id:from:to:cc:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:cleverness; s=6465f9c843.k2403; bh=s78ghnnNpXKzlcx5i4i5hkK5X3VWhZho++zecmXeYzI=; b=mAt7LoDsDUj+9+mZgLRzjTBtrn6nO/vF//hbtAXiMhpIzbNhxG5dS+y7C3mKEuozQx3A7cf9D8Tp91Q56+0S40jHYOoNIVgjTOLX+5EtPFgM/rJltq546YzmAFGKE/IPfP0YlAMKgP8WNp0du8jvvVeAZyx7+s6BmpQud3TQohprA9yeWbkhU+74mVEzjNWVfcS+cs60mwDo8+A+Pe1/6Bb1psVZuqmi9XmTst6OAZ7NybQx/HkcZeLh6MwMplJOuaU0JmoYrtr3IITicsslXDWN3XRxQK5h3TC+Y6mnTdXeX0c9nFd+XonR/bQckz9oniblOANB2xxBG7j0gcTVPw==
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed; d=taugh.com; h=date:message-id:from:to:cc:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:cleverness; s=6465f9c843.k2403; bh=s78ghnnNpXKzlcx5i4i5hkK5X3VWhZho++zecmXeYzI=; b=UUHIQL5dnbY8PHGGaKR346QUaoLn5cxsTGyGjsi5Bb5jCOvIwBcYlF9fuUMAHXZAWrHlevBJUrFBrnX0fiwIVfp2L+Soo6lQ7eqhtlxX0EX4aK+3hK4OB31XNe8wSxHi9dRCyG8p5eAhxELVHm6LGRTZuxGe6SlADjPRiNOF58xw0qcP4UYe1GeR0nmkGXFtAHrNIGXnWFyLF5Q0RaUDnel6mDTgzmVT0XUH7UXlPnIqFQSdqpnK/LhmUzLE44m7HXampxky8tF79gXvi1BjKgD9hbtcD+D6Y+/8aydReO3ASMlKVDRJrFb1T5AoE/YwLl5cvGT/9udlON8bWpxAkg==
Received: from ary.qy ([IPv6:2001:470:1f07:1126::78:696d:6170]) by imap.iecc.com ([IPv6:2001:470:1f07:1126::78:696d:6170]) with ESMTPS (TLS1.3 ECDHE-RSA CHACHA20-POLY1305 AEAD) via TCP6; 19 Mar 2024 17:15:47 -0000
Received: by ary.qy (Postfix, from userid 501) id 03AD385B000F; Tue, 19 Mar 2024 13:15:46 -0400 (EDT)
Date: Tue, 19 Mar 2024 13:15:46 -0400
Message-Id: <20240319171547.03AD385B000F@ary.qy>
From: John Levine <johnl@taugh.com>
To: emailcore@ietf.org
Cc: aamelnikov@fastmail.fm
In-Reply-To: <369a0a4a-9a33-442c-836c-2d4d388cce27@app.fastmail.com>
Organization: Taughannock Networks
X-Headerized: yes
Cleverness: minimal
Mime-Version: 1.0
Content-type: text/plain; charset="utf-8"
Content-transfer-encoding: 8bit
Archived-At: <https://mailarchive.ietf.org/arch/msg/emailcore/sjmvwg7gEb-31evb9SfGBE7Ppjk>
Subject: Re: [Emailcore] Ticket #92: CNAME handling in “5.1. Locating the Target Host” (rfc5321bis)
X-BeenThere: emailcore@ietf.org
X-Mailman-Version: 2.1.39
Precedence: list
List-Id: EMAILCORE proposed working group list <emailcore.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/emailcore>, <mailto:emailcore-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/emailcore/>
List-Post: <mailto:emailcore@ietf.org>
List-Help: <mailto:emailcore-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/emailcore>, <mailto:emailcore-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 19 Mar 2024 17:15:55 -0000

It appears that Alexey Melnikov  <aamelnikov@fastmail.fm> said:
>  about a statement in the A/S pointing out that long CNAME chains
>  are a source of trouble, that, when possible, one should stick
>  to 1123-style canonical names, and when that is not possible, to
>  try to keep the chains short.
>
>After thinking a bit more about this, I think I am happy with this proposal.
>John, do you think I should just reassign this ticket to A/S or do you think some small clarification is needed in rfc5321bis?

I agree we put it in the A/S.  Since any application that uses the
DNS has the same problem, I would just note that implenentations
should take the usual precautions against excess DNS work.

The DNS has deliberately not set specific limits on things like CNAME
chains that can cause a lot of resolver work, but just say that
implmentations should set some limit. This is not new, it's in section
7.1 of RFC 1035.

R's,
John

v2.23.0 | Report a Bug | By Email