netdev - Re: [PATCH net-next v2 0/3] icmp: Add RFC 5837 support

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Message-ID: <aQ4qefp51ucf8CAR@eidolon.nox.tf>
Date: Fri, 7 Nov 2025 18:20:57 +0100
From: David 'equinox' Lamparter <equinox@...c24.net>
To: Ido Schimmel <idosch@...dia.com>
Cc: Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
	davem@...emloft.net, pabeni@...hat.com, edumazet@...gle.com,
	horms@...nel.org, dsahern@...nel.org, petrm@...dia.com,
	willemb@...gle.com, daniel@...earbox.net, fw@...len.de,
	ishaangandhi@...il.com, rbonica@...iper.net, tom@...bertland.com,
	Justin Iurman <justin.iurman@...ege.be>
Subject: Re: [PATCH net-next v2 0/3] icmp: Add RFC 5837 support

On Wed, Oct 29, 2025 at 06:31:43PM -0700, Jakub Kicinski wrote:
> On Wed, 29 Oct 2025 11:54:43 +0200 Ido Schimmel wrote:
> > > Is there supposed to be any relation between the ICMP message attrs 
> > > and what's provided via IOAM? For interface ID in IOAM we have
> > > the ioam6_id attr instead of ifindex.  
> > 
> > RFC 5837 precedes IOAM and I don't see any references from IOAM to RFC
> > 5837. RFC 5837 is pretty clear about the interface index that should be
> > provided:
> > 
> > "The ifIndex of the interface of interest MAY be included. This is the
> > 32-bit ifIndex assigned to the interface by the device as specified by
> > the Interfaces Group MIB [RFC2863]".
> 
> Makes sense, thanks. And we have another 4 weeks to change our mind, 
> in case someone from IETF pipes up..

The IETF is in fact doing draft-ietf-intarea-extended-icmp-nodeid, which
is past last call.  The good news is that it's extremely similar,
different class value but same C-Type bitmask, the main distinction is
that 5837 had forbidden the use of "cross-address-family" addresses.

Note that for unnumbered networks, 5837 is wrong - it's
interface/nexthop information.  But the interface has no address, the
node does.  draft-ietf-intarea-extended-icmp-nodeid is about node
information and the correct thing to use for that case.

The good news is that the draft is past last call, IANA values have been
assigned, there's a bunch of text bashing going on but it's well into
the publishing process.

-David