[atlas] RIPE Atlas and nagios status-checks

Dear All,

The following message may be of interest to you if you're using Nagios (or
variations like icinga) to query RIPE Atlas for status-checks.

Yesterday morning our operations team made a change to the service
configuration such that atlas.ripe.net only answers queries if they have
proper Host: headers set. This is arguably a good operational practice, so
we'd like to enforce it.

However, one of the users running said nagios checks noticed that this
causes 403 answers instead of the expected behaviour. We concluded that this
is because the check_http plugin doesn't always set the Host: header.
According to our statistics in total 12 users are affected, and since we
could not foresee this problem, we temporarily reverted our configuration to
the old settings.

The fix on the client side is easy: one needs to add "-H atlas.ripe.net"
parameter (or a similar change depending on forks and versions) to the
checks. We'd like to ask our user to apply this change in the next two weeks
in order to send well-formatted requests to our service.

Thank you,
Robert Kisteleki
RIPE NCC