netdev - Network prefix length for local tunnel address

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Message-ID: <bafe4bfa-17e4-14b2-cdde-54938784b257@gmail.com>
Date:   Tue, 14 Jan 2020 12:57:34 -0300
From:   Eduardo Trápani <etrapani@...il.com>
To:     netdev@...r.kernel.org
Subject: Network prefix length for local tunnel address

The manual for ip-address says:

 > If a peer address is specified, the local address cannot have a 
prefix length. The network prefix is associated with the peer rather 
than with the local address.

Does it means that the local address has no prefix at all? Or that it 
inherits the prefix from the peer address?

The question arises because I found out I can "duplicate" the local ip 
address, instead of getting a "RTNETLINK answers: File exists".

These are the steps:

# ip tuntap add dev tun3 mode tun user alice group alice

# ip address add 10.8.0.1 peer 10.8.0.2/32 dev tun3

# ip address add 10.8.0.1/32 dev tun3

# ip address list dev tun3
…
inet 10.8.0.1 peer 10.8.0.2/32 scope global tun3
…
inet 10.8.0.1/32 scope global tun3
…

Is that the expected behaviour?