michael orlitzky

haeredes

get it

The development version can be found in the haeredes git repository. Official releases can be found on the haeredes hackage page.

What is it?

Haeredes is primarily useful for ISP network administrators. Customers will occasionally decide to switch hosts without alerting the current host; this can cause two problems:

Haeredes can alert administrators when NS/MX records are changed.

Usage

user $ haeredes [OPTIONS] [DELEGATES] <input>

Normalization

By default, domain/hostnames given will be normalized in two ways:

Query Results

When Haeredes makes a query for an MX record, the result is parsed from the answer section of the response. This is straightforward.

For NS records, however, there are two sections that may contain results. If you query the authoritative nameservers for example.com, they will return the response in the answer section, as with MX records:

user $ dig +short @a.iana-servers.net example.com NS
b.iana-servers.net. a.iana-servers.net.

However, if you ask a root server, they will return the response in another section, called authority. The answer section is empty:

user $ dig +short @a.gtld-servers.net example.com NS

We have to request the authority section explicitly:

user $ dig +noall +authority @a.gtld-servers.net example.com NS
example.com. 172800 IN NS a.iana-servers.net. example.com. 172800 IN NS b.iana-servers.net.

Given Haeredes' use case, it is useful to combine the two. You can query a root server to check the registrar data, or a recursive resolver to check the data on the authoritative nameservers.

So that's what we do. In NS mode, Haeredes will check both the answer and authority sections for results.

Parallel Queries

Haeredes can use multiple threads to perform its queries. It will use a number of threads equal to the number of processors available to the GHC runtime. This can be changed with the +RTS -N flag. For example, to use 10 threads,

user $ haeredes [OPTIONS] [DELEGATES] +RTS -N10

DNS Errors

There are three types of DNS errors that can occur:

Haeredes is designed to ignore these errors. A timeout or bad response to a query is not an indication that something is wrong with the DNS for the supplied domains. There might be something else wrong with your (caching/recursive) DNS infrastructure, but it isn't one of the problems that Haeredes is designed to detect.

Options

--no-append-root, -n
Don't append a trailing dot to any DNS names. If you know what you're doing, this can be used to check relative results. Otherwise, it will probably just lead to false positives.
--server, -s
Use the given DNS server rather than the resolvers listed in /etc/resolv.conf. Either an IP address or a hostname will work.

Examples

Requirements

All of the software dependencies are listed in the haeredes.cabal file. Just use cabal to build it.

Installation

Cabal handles the build, so do whatever you normally do to install cabal packages. If you just want to install it for your user,

user $ runghc Setup.hs configure --user
user $ runghc Setup.hs build
user $ runghc Setup.hs install

should do it.

How to report bugs

Email them to me at that address on the home page.