Djbdns

DNS implementation created by Daniel J. Bernstein because he was fed up with repeated BIND security holes. There have been no bugs found in DJBDNS since version 1.0, and for the first person to find a security hole.

DJBDNS consists of 6 servers:

• dnscache -- the local dns resolver and cache.
• tinydns -- a database-driven dns server.
• walldns -- a "reverse DNS wall", providing IP to domain name lookup only.
• rbldns -- a server designed for dns blacklisting service.
• pickdns -- a database-driven server that chooses from matching records depending on the requester's location. (This feature is now a standard part of tinydns.)
• axfrdns -- a zone-transfer server.

a number of client tools:

• axfr-get -- a zone-transfer client.
• dnsip -- simple address from name lookup.
• dnsipq -- address from name lookup with rewriting rules.
• dnsname -- simple name from address lookup.
• dnstxt -- simple text record from name lookup.
• dnsmx -- mail exchanger lookup.
• dnsfilter -- looks up names for addresses read from stdin, in parallel.
• dnsqr -- recursive general record lookup.
• dnsq -- non-recursive general record lookup, useful for debugging.
• dnstrace (and dnstracesort) -- comprehensive testing of the chains of authority over dns servers and their names.

and associated configuration tools.

DJBDNS splits off ancillary features, like AXFR-style zone transfers, into separate programs. Zone file parsing, DNS caching, and recursive resolving are also implemented as separate programs. The result of these design decisions is a dramatic reduction in code size and complexity of the daemon program that answers lookup requests. Prof. Bernstein (and many others) feel that this is true to the spirit of the Unix operating system, and makes security verification much simpler.

DJBDNS is licensed to permit free redistribution and use, and the source code is publicly available, but the license does not permit distribution of modified versions without permission (and is thus not free software).

See also: Qmail.