walldns - a reverse DNS wall

walldns is a reverse DNS wall. It accepts iterative DNS queries for in-addr.arpa domains from hosts around the Internet, and supplies generic responses that avoid revealing local host information.

For example, walldns provides a PTR record for 4.3.2.1.in-addr.arpa showing 4.3.2.1.in-addr.arpa as the name of IP address 1.2.3.4, and a matching A record showing 1.2.3.4 as the IP address of 4.3.2.1.in-addr.arpa.

Normally walldns is set up by the walldns-conf(8) program.

walldns runs chrooted in the directory specified by the $ROOT environment variable, under the uid and gid specified by the $UID and $GID environment variables.

walldns listens for incoming UDP packets addressed to port 53 of $IP. It does not listen for TCP queries.

walldns rejects inverse queries, non-Internet-class queries, truncated packets, packets that contain anything other than a single question, queries for domains outside in-addr.arpa, and request types other than A, PTR, and *.

walldns does not include NS or SOA records with its responses.

walldns uses TTLs slightly over one week.

walldns-conf(8) http://cr.yp.to/djbdns.html