[WIP] DNS Server Implementation

[attozk]

• Added DNS server implementation
• Added example for a simple echo dns name server
• Updated readme

(Missing test cases for Server, but would like the implementation to be reviewed)

Current Server implementation:

$loop = React\EventLoop\Factory::create();
$server = new React\Dns\Server\Server($loop);
$server->listen(53, '0.0.0.0');
$server->ready();

$server->on('query', function($question, $clientIP, $response, $deferred)
{
    /**
        @var $question  React\Dns\Query\Query
        @var $request   React\Dns\Model\Message
        @var $deferred  React\Promise\Deferred
    */

    // Add records to answer
    //$response->answers[] = new \React\Dns\Model\Record($question->name, $question->type, $question->class, rand(1,9999),
    //                                                   'DATA BASED ON TYPE GOES HERE');

    // or add records to authority and additional
    // $response->authority[] = new  \React\Dns\Model\Record(....)
    // $response->additional[] = new  \React\Dns\Model\Record(....)

    $deferred->resolve($response);

    // or reject this
    // $deferred->reject($response);
});


// print some stats as well
$loop->addPeriodicTimer(60, function() use($server)
{
    echo "DNS Server stats:\n";
    $server->stats();
});

$loop->run();

[attozk]

@igorw This is pending test cases, but I am putting it up for your review of nameserver implementation. Your feedback is appreciated.

Thanks

[clue]

Thanks for your PR @attozk, 👍 on having a DNS server implementation!

This is a bit hard to review given how huge this PR is. Also, it appears to leak some changes that were meant to be part of #8, I guess?

Either way, is there anything that needs to be done to push this forward?

[attozk]

@clue server implementation is piggy backing on #8; otherwise the server implementation itself is pretty small.

You can see additional server setup examples I have drafted without the clutter @ https://github.com/hathoora/babaji-dns/tree/master/experiment