Re: I-D Action: draft-carpenter-6man-rfc6874bis-00.txt

Brian E Carpenter <> Wed, 07 July 2021 21:18 UTC

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Subject: Re: I-D Action: draft-carpenter-6man-rfc6874bis-00.txt
To: Philip Homburg <>,
Cc: Michael Richardson <>
References: <> <> <> <> <> <> <> <> <6771.1625578366@localhost> <>
From: Brian E Carpenter <>
Message-ID: <>
Date: Thu, 08 Jul 2021 09:18:39 +1200
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On 08-Jul-21 03:31, Philip Homburg wrote:
>> Nico Schottelius <> wrote:
>>    > While copy & paste won't work with this proposal, I believe the %25
>>    > escape should be "good enough" for most daily usage.
>> Also, ping and/or getaddrinfo() could become tolerant of %25 as a special
>> case (and given that few Windows machines have 25 interfaces), which would
>> let the copy&paste work the other way.
> Instead of doing this, maybe we should pick a new character in an update of
> RFC 4007 and deprecate '%' as a mistake?

Even 9 years ago the WG concluded that '%' was too engrained in code and
actual practice to deprecate it. Many libraries that handle IPv6 addresses
support '%' and that means that innumerable pieces of software would be
impacted, so deprecation seems impractical.

If this was a mistake, it was made in 2005 when we approved RFC4007.
> Aternatively, if we make fe80::ABCD%0 a valid address in the socket API

I think you'll find that it already is. I use the netifaces module in Python
and it returns things like [{'addr': '00:ff:19:f7:7d:9a'}], 23: [{'addr': 'fe80::216a:f0d3:2303:3d1%6', 'netmask': 'ffff:ffff:ffff:ffff::/64', 'broadcast': 'fe80::ffff:ffff:ffff:ffff%6'}]. It's a bit obscure, though. Also (before
Python 3.7) socket.getaddrinfo(socket.gethostname(),0) on Windows would
return fe80::216a:f0d3:2303:3d1%6, but somebody changed that behaviour.

I needed to make this work to implement RFC 8990 and it wasn't exactly

> (and do something sensible in operating systems to select a default interface)

But the interesting use cases are ones where the default won't do.


> then we can reduce the use of scoped addresses and thus the copy paste problem.
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