TDS can’t do DNS

tds.net provides DSL service in (among other places) the Middleton WI area.

When connecting with PPPoE, one may get any number of different IP addresses. The problem stems from the fact that TDS has aquired several companies along the way, and their IP blocks. Yet, they have busted reverse DNS for those IP blocks. A connection aquired 216.165.151.6 today.

$ host 216.165.151.6
6.151.165.216.in-addr.arpa domain name pointer a29-6.madison.chorus.net.
$ ping a29-6.madison.chorus.net
ping: unknown host a29-6.madison.chorus.net

So, 216.165.151.6 has a valid reverse DNS entry, but a29-6.madison.chorus.net has no associated A records back to 216.165.151.6! This one horribly busted dns setup, and sshd complains thusly, and correctly. TDS should be ashamed of themselves.

sshd[21534]: warning: /etc/hosts.deny, line 17: can’t verify hostname: gethostbyname(a29-6.madison.chorus.net) failed