rbldns - an IP-address-listing DNS server
rbldns is an IP-address-listing DNS server. It accepts iterative DNS
queries from hosts around the Internet asking about various IP
addresses. It provides responses showing whether the addresses are on
a locally configured list, such as RBL or DUL.
Normally rbldns is set up by the rbldns-conf(8) program.
rbldns runs chrooted in the directory specified by the $ROOT
environment variable, under the uid and gid specified by the $UID and
$GID environment variables.
rbldns listens for incoming UDP packets addressed to port 53 of $IP.
It does not listen for TCP queries.
rbldns handles domains of the form d.c.b.a.base where a.b.c.d is the IP
address in question and base is given by the $BASE environment
rbldns rejects inverse queries, non-Internet-class queries, truncated
packets, packets that contain anything other than a single query, query
types other than A, TXT, or *, and queries for domains outside $BASE.
It looks up other queries inside data.cdb, a binary file created by