openssh unix dev - Oct 2015 - Permanently added hostkeys (due to IP address pool), without confirmation

Hello,

maybe someone could please help and shed some light on a problem
that i don't understand, and that even in multiple ways.
The problem occurred three or four times over the past months
(maybe half a year?) and manifests as

  ++ Pushing to "gitlab" (at least "master" differs)!
  Warning: Permanently added the RSA host key for IP address
'104.46.105.89' to the list of known hosts.

I get no confirmation prompt, which i normally do?!
Of course i do have a configuration file with an

  UserKnownHostsFile        ~/arena/data/ssh/known_hosts

entry, and that already has a

  gitlab.com,54.93.71.23  DATA

line for months.  I do have a "Host" entry for "*gitlab.org"
(with
explicit IdentityFile).  The entry in known_hosts that i (hope to
have confirmed correctly back then) is not identical with the
other two entries, but which are, except for the addresses

  --- k.1 2015-10-09 18:09:10.511793883 +0200
  +++ k.2 2015-10-09 18:09:26.508373888 +0200
  @@ -1,2 +1,2 @@
  -52.21.36.51
  +104.46.105.89
   ssh-rsa ...

I understand that the keys in k.1 and k.2 are the same that
ssh-keyscan(1) gives me, whereas the address i verified does
currently give no ssh-keyscan result at all.  (I verified it back
in the day in that i was able to login after placing my public key
at their server via a HTTPS connection after i had created my
account.  I'm no expert in mathematics or the SSH protocols, but
i'm confident as only a greenhorn or real expert can be.)

So: no confirmation prompt, no hostname but only the address for
the entry in known_hosts even though the connection is to
gitlab.com (they're appended though), and multiple entries with
the same key.
I'm on "OpenSSH_7.1p1, OpenSSL 1.0.2d 9 Jul 2015".
Thank you in advance for any hint, ciao,

--steffen

On Fri, 9 Oct 2015, Steffen Nurpmeso wrote:
> Hello,
> 
> maybe someone could please help and shed some light on a problem
> that i don't understand, and that even in multiple ways.
> The problem occurred three or four times over the past months
> (maybe half a year?) and manifests as
> 
>   ++ Pushing to "gitlab" (at least "master" differs)!
>   Warning: Permanently added the RSA host key for IP address
'104.46.105.89' to the list of known hosts.
> 
> I get no confirmation prompt, which i normally do?!
> Of course i do have a configuration file with an
> 
>   UserKnownHostsFile        ~/arena/data/ssh/known_hosts
> 
> entry, and that already has a
> 
>   gitlab.com,54.93.71.23  DATA
> 
> line for months.  I do have a "Host" entry for
"*gitlab.org" (with
> explicit IdentityFile).  The entry in known_hosts that i (hope to
> have confirmed correctly back then) is not identical with the
> other two entries, but which are, except for the addresses
> 
>   --- k.1 2015-10-09 18:09:10.511793883 +0200
>   +++ k.2 2015-10-09 18:09:26.508373888 +0200
>   @@ -1,2 +1,2 @@
>   -52.21.36.51
>   +104.46.105.89
>    ssh-rsa ...
You have CheckHostIP enabled (it is on by default) and some DNS server
or hosts file is returning 104.46.105.89 for that hostname. When ssh
connects to 104.46.105.89, it is offering the same key as you have
already learned for 52.21.36.51, so it is automatically added to
known_hosts.

See ssh_config's entry on CheckHostIP for a few more details.

-d

Damien Miller <djm at mindrot.org> wrote:
 |On Fri, 9 Oct 2015, Steffen Nurpmeso wrote:

 |You have CheckHostIP enabled (it is on by default) and some DNS server
 |or hosts file is returning 104.46.105.89 for that hostname. When ssh
 |connects to 104.46.105.89, it is offering the same key as you have
 |already learned for 52.21.36.51, so it is automatically added to
 |known_hosts.
 |
 |See ssh_config's entry on CheckHostIP for a few more details.

Yes (through default).  Ok that explains the missing confirmation.
It's pretty clear from the manual, thank you.

--steffen