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Re: Debian jessie > buster IPv6 link scope change of behaviour

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On Wed 20 Jan 2021 at 14:46:31 (+0100), Marc SCHAEFER wrote:
> 
> I experiment [experienced] a change of behaviour between the kernel of Debian jessie
> and Debian buster.
> 
> Namely, before, ping6 fe80::1 would fail, since it is ambiguous (fe80::1
> is a link scope, thus a zone/interface scope ID is required).
> 
> With buster, it tries the first Ethernet interface, no error (unless
> NDP does not find it, obviously).
> 
> The correct behaviour when specifying the zone (interface scope ID) is
> the same on both versions:
> 
>    ping6 fe80::1%eth0 # e.g.
> 
> Is there something broken with my setup, or has something changed in the
> way the Linux kernel behaves when the required zone (interface scope ID)
> is not specified ?
> 
> I found the idea of reporting an error when a scope is not given very
> correct, simple and pedagogic (aka jessie behaviour).

I'm not convinced that reporting an error would be correct. I think,
rather, that it should use the interface that it considers "nearest".
On success, it will continue to use that interface; on failure, it
will try others in round-robin fashion to find one that works.

That's desirable behaviour for the packets themselves, is it not.
As far as the address is concerned, fe80::1 is perfectly formed,
but ambiguous. Is that what your jessie error message used to say?

Cheers,
David.

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Thread

Debian jessie > buster IPv6 link scope change of behaviour Marc SCHAEFER <schaefer@alphanet.ch> - 2021-01-20 15:30 +0100
  Re: Debian jessie > buster IPv6 link scope change of behaviour David Wright <deblis@lionunicorn.co.uk> - 2021-01-21 07:10 +0100
    Re: Debian jessie > buster IPv6 link scope change of behaviour Marc SCHAEFER <schaefer@alphanet.ch> - 2021-01-21 08:10 +0100
      Re: Debian jessie > buster IPv6 link scope change of behaviour Marc SCHAEFER <schaefer@alphanet.ch> - 2021-01-21 08:20 +0100
        Re: Debian jessie > buster IPv6 link scope change of behaviour David Wright <deblis@lionunicorn.co.uk> - 2021-01-22 01:30 +0100
          Re: Debian jessie > buster IPv6 link scope change of behaviour Marc SCHAEFER <schaefer@alphanet.ch> - 2021-01-23 10:10 +0100

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