Kernel allows to add the same IPv4 address that only differs by
peer-address (IFL_ADDRESS):

    $ ip link add dummy type dummy
    $ ip address add 1.1.1.1 peer 1.1.1.3/24 dev dummy
    $ ip address add 1.1.1.1 peer 1.1.1.4/24 dev dummy
    RTNETLINK answers: File exists
    $ ip address add 1.1.1.1 peer 1.1.2.3/24 dev dummy
    $ ip address show dev dummy
    2: dummy@NONE: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN group default
        link/ether 52:58:a7:1e:e8:93 brd ff:ff:ff:ff:ff:ff
        inet 1.1.1.1 peer 1.1.1.3/24 scope global dummy
           valid_lft forever preferred_lft forever
        inet 1.1.1.1 peer 1.1.2.3/24 scope global dummy
           valid_lft forever preferred_lft forever

We must also consider peer-address, otherwise platform will treat
two different addresses as one and the same.

https://bugzilla.gnome.org/show_bug.cgi?id=756356