Re: [dhcwg] [v6ops] [EXTERNAL] Re: Question to DHCPv6 Relay Implementors regarding draft-ietf-dhc-dhcpv6-pd-relay-requirements

Jen Linkova <furry13@gmail.com> Fri, 09 October 2020 01:09 UTC

Return-Path: <furry13@gmail.com>
X-Original-To: dhcwg@ietfa.amsl.com
Delivered-To: dhcwg@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 561443A10FB; Thu, 8 Oct 2020 18:09:19 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.848
X-Spam-Level:
X-Spam-Status: No, score=-1.848 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, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=gmail.com
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id LXn1J6Cv3FXi; Thu, 8 Oct 2020 18:09:18 -0700 (PDT)
Received: from mail-qk1-x743.google.com (mail-qk1-x743.google.com [IPv6:2607:f8b0:4864:20::743]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id F2DEA3A0E17; Thu, 8 Oct 2020 18:09:17 -0700 (PDT)
Received: by mail-qk1-x743.google.com with SMTP id s7so9005133qkh.11; Thu, 08 Oct 2020 18:09:17 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=ylCPku13r0j9UqhPi+igQ9MBe3gd7DlsX+BTIcjL2iI=; b=myiJT//7f3GLIdss8abvwnKr1edKm/IMB10Rb+NkbtVKGUtQqKwO1gFlxCJFyoHRTN ajXWgrdpN6/7pAFCsHw6TtJuSrNmflanDn/4+HMzWeXNDAaJFNUrncDjw2HPFrvPkqka ejMD+r7HglJBGZXD1s3ZIyQJkAOYmko33qaCPqpRwpZE5dNVhyKSm//fxw9ozDuQ7fRV xPj4Nkfztw2jfZT6Geq1mS1zHjCIngENEJwPjrrEubm21UwYbLPdnwb2EfsasLD4DlSg xbvZxBXa/l0e1Z0pJux/dl7GC8eoBNUc72WSecTVfDyigQIxC0mIv4GY8J+nVSpPoEe0 TYbg==
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=ylCPku13r0j9UqhPi+igQ9MBe3gd7DlsX+BTIcjL2iI=; b=LUhR+SH9Fl2jwlkzGrEC+496j06WShOpdglUyXiAUpmpVRilcvdbcGcT7+w4Bdvxwu XN0agitRHM5M0xsSnD+idRVYTGR0oEG4xLkpzdUPj2RpT8/Wy5p1bkqWXCBo18KU6pnh yxoIwIgMq52jcCjgU75xiWc2WLlt15UdQ2Ci1f0uR5aiUtMcFY75Oqoz9O/yuVFZBLZX ao/X77+PDUv7p9R5+ilkDYO5gV6i3m+ogijwQ4/X171zwH1HkOU4lt7aH9iRb9BN7u2z Qx9M8yqvQbM/w2jdfqcSo41zHlUWqtlw47Dfi3QDj/8oXPb7wV38SAbyO/37suUsLvyv bPhQ==
X-Gm-Message-State: AOAM530IhLgi0C6WAsTyi/8QhN0m/mq31Z9HlmUK+3lH6RVdkZADQK4M 2EOCbynmPe/cHe9hzur1kzwJ6qfJt/dqSVU6/gY=
X-Google-Smtp-Source: ABdhPJysip0ptA/Ilf8YtNiw0ESd++TqCvxJJiOnl/ZUvgOvAXFat44CRTcnvhg0wlKEXhOy5iBaOsJFQG9anfjsNok=
X-Received: by 2002:a37:849:: with SMTP id 70mr11367189qki.332.1602205756844; Thu, 08 Oct 2020 18:09:16 -0700 (PDT)
MIME-Version: 1.0
References: <ff36a6d9f0834b5bbf331c6c40df16b8@boeing.com> <6373DDB1-753B-4E15-8097-9ED03F1BFC19@employees.org>
In-Reply-To: <6373DDB1-753B-4E15-8097-9ED03F1BFC19@employees.org>
From: Jen Linkova <furry13@gmail.com>
Date: Fri, 9 Oct 2020 12:09:05 +1100
Message-ID: <CAFU7BATCX4L=07sF5-M+uwnkxm1sNcnGRYCWd82U0mD6S2P53w@mail.gmail.com>
To: Ole Troan <otroan@employees.org>
Cc: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>, dhcwg <dhcwg@ietf.org>, v6ops list <v6ops@ietf.org>, 6man <ipv6@ietf.org>, "Bernie Volz (volz)" <volz@cisco.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Archived-At: <https://mailarchive.ietf.org/arch/msg/dhcwg/405mpzRBXQKycDtUSpul_sotgwo>
Subject: Re: [dhcwg] [v6ops] [EXTERNAL] Re: Question to DHCPv6 Relay Implementors regarding draft-ietf-dhc-dhcpv6-pd-relay-requirements
X-BeenThere: dhcwg@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: <dhcwg.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/dhcwg>, <mailto:dhcwg-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/dhcwg/>
List-Post: <mailto:dhcwg@ietf.org>
List-Help: <mailto:dhcwg-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/dhcwg>, <mailto:dhcwg-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 09 Oct 2020 01:09:19 -0000

On Fri, Oct 9, 2020 at 9:01 AM Ole Troan <otroan@employees.org> wrote:
> > On 8 Oct 2020, at 23:55, Templin (US), Fred L <Fred.L.Templin@boeing.com> wrote:
> >
> > Now, client B sends packets destined to an address in A to R, and R forwards the
> > packets to client A since it still has a route for A. When the packets arrive at A,
> > however, A forwards them back to R since it has "forgotten" that it holds the
> > prefix A. When R receives the packets from A with destination address also
> > from prefix A, it must drop them instead of forwarding them back to A to
> > avoid looping.
>
> This is indeed what the requirement in the draft says.

Well, then I should say that the requirement is not clear and open to
misinterpretation. I read it as:
- the client B sends a packet with the destination address in A to R.
When R receives it, it finds out that the both conditions from R4 are
met:
1) a route for a delegated prefix points to this interface
2) the receives traffic (from the device B) on this interface with a
destination address within the delegated prefix.
So the traffic will be dropped right away, not after it went to the
client A (and back, if A forgot about the delegation).

I read Ian's response as he confirmed my interpretation and the
traffic will be dropped.
It looks to me like R4  assumes that all links are p2p, and 'receiving
a traffic from an interface the client is connected to' == 'receiving
a traffic from the client'.

> This isn’t quite obvious how to implement, which why I brought up the question if anyone had implemented this. And if it’s supported in hw etc.

What you and Fred described does look like a hard thing to implement,
while the way I read R4 seems to be very easy to do (kind of URPF,
basically) but, as discussed, might break working scenarios.


-- 
SY, Jen Linkova aka Furry