check_http fails to decode chunked encoding before performing string checks

[James Troup]

One of our HTTP checks (for the Ubuntu Wiki as it happens) was
flapping between OK and Critical because the string check was failing
despite getting a 200 and similar length content to a successful
check. I eventually managed to reproduce this with a manual
-v-enabled run and discovered it's happening because the string
check_http was looking for happened to cross a chunk boundary in the
failure case (but was within a chunk in the successful case.)

If check_http is going to use HTTP/1.1, it needs to support chunked
encoding properly and decode the stream fully before running string
checks.

This can be worked around in (most?) cases by using '-I <ip> -k "Host:
<hostname>"' in place of '-H <hostname>' as that forces check_http to
drop down to a HTTP/1.0 connection.

[Robert Collins (lifeless)]

(Note that chunked is a MUST requirement for http 1.1 clients)

[Peter Valdemar Mørch (pmorch)]

There is this upstream bugreport, open since 2009-05-04:
check_http asks for HTTP/1.1, but doesn't understand chunked - ID: 2786808
http://sourceforge.net/tracker/index.php?func=detail&aid=2786808&group_id=29880&atid=397597

[Jan Wagner (waja)]

Upstream bug is now https://github.com/monitoring-plugins/monitoring-plugins/issues/1122