BUG #9518: temporary login failure - "missing pg_hba entry"

The following bug has been logged on the website:

Bug reference: 9518
Logged by: Mike Blackwell
Email address: mike(dot)blackwell(at)rrd(dot)com
PostgreSQL version: 9.3.3
Operating system: RHEL 6
Description:

The following sequence showed up in the error log recently:

2014-03-09 19:53:18 CDT [30632]: [2-1] username(at)databasename
10.17.x.y(53454)LOCATION: ClientAuthentication, auth.c:486
2014-03-09 19:53:18 CDT [30633]: [1-1] username(at)databasename
10.17.x.y(53455)FATAL: 28000: no pg_hba.conf entry for host "10.17.x.y",
user "username", database "databasename", SSL off
2014-03-09 19:53:18 CDT [30633]: [2-1] username(at)databasename
10.17.x.y(53455)LOCATION: ClientAuthentication, auth.c:486
2014-03-09 20:05:15 CDT [32505]: [1-1] username(at)databasename
10.17.x.y(54134)LOG: 00000: duration: 13641.600 ms execute dbdpg_p28498_2:

select ...;

2014-03-09 20:05:15 CDT [32505]: [2-1] username(at)databasename
10.17.x.y(54134)LOCATION: exec_execute_message, postgres.c:1991

The auth failure shows up seven times over a span of approximately six
seconds, with the one above being the last of the sequence.

This is on a server that has been running for quite a while. The last conf
reload was at the last Postgres restart on 3/1. The pg_hba.conf file
timestamps indicate no recent change as well.

This may not be a PostgreSQL bug but I'm running out of other explanations.