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Date:   Mon, 13 May 2019 15:05:28 +0000
From:   Maxim Mikityanskiy <>
To:     "David S. Miller" <>,
        Alexey Kuznetsov <>,
        Hideaki YOSHIFUJI <>
CC:     "" <>,
        Leon Romanovsky <>,
        Maxim Mikityanskiy <>
Subject: [RFC] inet6_validate_link_af improvements

A recent bug in systemd [1] triggered the following kernel warning:

  A link change request failed with some changes committed already.
  Interface eth1 may have been left with an inconsistent configuration,
  please check.

do_setlink() performs multiple configuration updates, and if any of them
fails, do_setlink() has no way to revert the previous ones. It is also
not easy to validate everything in advance and perform a non-failing
update then. However, do_setlink() has some basic validation that can be
extended at least this case. IMO, it's better to fail before doing any
changes than to perform a partial configuration update.

This RFC contains two patches that move some checks to the validation
stage (inet6_validate_link_af() function). Only one of the patches (if
any) should be applied. Patch 1 only checks the presence of at least one
parameter, and patch 2 also moves the validation for addrgenmode that is
currently part of inet6_set_link_af(). Of course, there are still many
ways how do_setlink() can fail and perform a partial update, but IMO
it's better to prevent at least some cases that we can.

Please express your opinions on this fix: do we need it, do we want to
validate as much as possible (patch 2) or only basic stuff like the
presence of parameters (patch 1)? I'm looking forward to hearing the




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