Debian jessie > buster IPv6 link scope change of behaviour

[Marc SCHAEFER <schaefer@alphanet.ch>]

Hello,

I experiment 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).

Thank you for your help :)

PS: I upgraded from jessie to buster, so I don't know when the
    behaviour change happened in the Linux kernel