native-dns-cache

Cache
-----

If you perform a query on an A or AAAA type and it doesn't exist, the cache
will attempt to lookup a CNAME and then resolve that.

The constructor takes an optional object with the following properties:

* store -- implements the cache store model (optional, default MemoryStore)

Methods:

* lookup(question, cb) -- for a given question check the cache store for
existence
* store(packet) -- iterates over the resource records in a packet and sends
them to the cache store
* purge() -- clears the cache store of all entries

MemoryStore / Cache store model
-------------------------------

MemoryStore(opts) -- An in memory store based on a js object

Methods:

* get(domain, key, cb)
- domain is the holder under which keys will be applied,
key is the subdomain that is being queried for.
If you get('example.com', 'www', cb) you are really asking for www.example.com.
- cb(err, results) -- results is an object of types and array of answers
* { 1: [{address: '127.0.0.1', ttl: 300, type: 1, class: 1}] }
* set(domain, key, data, cb)
- domain is the parent under which this key is stored.
key is the subdomain we are storing, data is an object of types with an array of answers.
* set('example.com', 'www', {1: [{class:1, type:1, ttl:300, address:'127.0.0.1'}]}, cb)
- cb(err, data) -- cb merely returns the data that was passed.
* delete(domain[, key[, type]], cb) -- delete all from a domain, a domain and key,
or a domain a key and a type.

Lookup
------

Is a mechanism that given a store performs the common resolution pattern.

Given example.com previous added to a store:

* www.example.com CNAME foo.bar.example.com.
.example.com A 127.0.0.1

A Lookup(store, 'example.com', {name:'www.example.com', type:1}, cb)
will resolve www to the CNAME and then search for foo.bar.example.com which
will return no results, and then search for *.bar.example.com which will also
return no results, and ultimately searches for *.example.com which will return
the desired record.

Callback will be called with (err, results) where results is an array suitable
for use in Packet.answer