This page explains the qualification rules followed by the dns_ip4_qualify library routine in DNScache.
Sample instructions:
# anything.local -> me -.local:me # me -> 127.0.0.1 =me:127.0.0.1 # any.name.a -> any.name.af.mil *.a:.af.mil # any-name-without-dots -> any-name-without-dots.heaven.af.mil ?:.heaven.af.mil # remove trailing dot *.:
Instructions are followed in order, each at most once. There are four types of instructions:
cheetah+.heaven.af.mil+.af.milis qualified as cheetah.heaven.af.mil if that name has IP addresses listed in DNS, or cheetah.af.mil otherwise.
In general, x+y1+y2+y3 is qualified as xy1 if xy1 has IP addresses listed in DNS; otherwise, as xy2 if xy2 has IP addresses listed in DNS; otherwise, as xy3. You can list any number of +'s.
Searching is applied after rewriting, so you can use a rewriting instruction such as
?:+.heaven.af.mil+.af.milto have lion qualified as lion.heaven.af.mil or lion.af.mil, and tiger qualified as tiger.heaven.af.mil or tiger.af.mil, and so on.
Searching is generally not a recommended feature. If you rely on gw being qualified as gw.af.mil, and someone suddenly adds a new gw.heaven.af.mil, you'll end up talking to the wrong host. It's better to rely on syntactic rules that you control.
?:.domain *.:so that .domain is added to any name without dots or brackets.
You can specify searching in $LOCALDOMAIN by using several domain names separated by spaces. Your system administrator can specify searching in /etc/resolv.conf by putting several domains on a search line.
Some resolver libraries interpret a domain line in /etc/resolv.conf as specifying a search list consisting of various suffixes of the domain.
With most resolver libraries, a long-running program won't see changes in /etc/resolv.conf. dns_ip4_qualify checks for changes every ten minutes.
Many resolver libraries will search the local domain for names with dots. This almost certainly isn't what you want. However, if it is, you can simulate it through rewriting:
# aol.com -> aol.com or aol.com.heaven.af.mil *:++.heaven.af.mil # but skip directly to heaven.af.mil if no dots ?++.heaven.af.mil:.heaven.af.mil