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Implement the Happy Eye Balls RFC's
By using the happy eye balls algorithm as described in RFC6555 and RFC8305 it will connect to the quickest responding server with a preference for IPv6.
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‎README.md‎

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@@ -43,6 +43,7 @@ handle multiple concurrent connections without blocking.
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* [Connector](#connector)
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* [Advanced client usage](#advanced-client-usage)
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* [TcpConnector](#tcpconnector)
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* [HappyEyeBallsConnector](#happyeyeballsconnector)
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* [DnsConnector](#dnsconnector)
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* [SecureConnector](#secureconnector)
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* [TimeoutConnector](#timeoutconnector)
@@ -1154,6 +1155,60 @@ be used to set up the TLS peer name.
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This is used by the `SecureConnector` and `DnsConnector` to verify the peer
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name and can also be used if you want a custom TLS peer name.
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#### HappyEyeBallsConnector
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The `HappyEyeBallsConnector` class implements the
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[`ConnectorInterface`](#connectorinterface) and allows you to create plaintext
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TCP/IP connections to any hostname-port-combination. Internally it implements the
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happy eyeballs algorythm from [`RFC6555`](https://tools.ietf.org/html/rfc6555) and
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[`RFC8305`](https://tools.ietf.org/html/rfc8305) to support IPv6 and IPv4 hostnames.
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It does so by decorating a given `TcpConnector` instance so that it first
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looks up the given domain name via DNS (if applicable) and then establishes the
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underlying TCP/IP connection to the resolved target IP address.
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Make sure to set up your DNS resolver and underlying TCP connector like this:
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```php
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$dnsResolverFactory = new React\Dns\Resolver\Factory();
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$dns = $dnsResolverFactory->createCached('8.8.8.8', $loop);
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$dnsConnector = new React\Socket\HappyEyeBallsConnector($loop, $tcpConnector, $dns);
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$dnsConnector->connect('www.google.com:80')->then(function (React\Socket\ConnectionInterface $connection) {
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$connection->write('...');
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$connection->end();
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});
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$loop->run();
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```
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See also the [examples](examples).
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Pending connection attempts can be cancelled by cancelling its pending promise like so:
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```php
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$promise = $dnsConnector->connect('www.google.com:80');
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$promise->cancel();
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```
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Calling `cancel()` on a pending promise will cancel the underlying DNS lookups
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and/or the underlying TCP/IP connection(s) and reject the resulting promise.
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> Advanced usage: Internally, the `HappyEyeBallsConnector` relies on a `Resolver` to
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look up the IP addresses for the given hostname.
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It will then replace the hostname in the destination URI with this IP's and
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append a `hostname` query parameter and pass this updated URI to the underlying
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connector.
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The Happy Eye Balls algorythm describes looking the IPv6 and IPv4 address for
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the given hostname so this connector sends out two DNS lookups for the A and
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AAAA records. It then uses all IP addresses (both v6 and v4) and tries to
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connect to all of them with a 50ms interval in between. Alterating between IPv6
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and IPv4 addresses. When a connection is established all the other DNS lookups
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and connection attempts are cancelled.
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#### DnsConnector
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The `DnsConnector` class implements the

‎src/HappyEyeBallsConnectionBuilder.php‎

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<?php
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namespace React\Socket;
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use React\Dns\Model\Message;
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use React\Dns\Resolver\ResolverInterface;
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use React\EventLoop\LoopInterface;
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use React\EventLoop\TimerInterface;
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use React\Promise;
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use React\Promise\CancellablePromiseInterface;
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/**
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* @internal
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*/
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final class HappyEyeBallsConnectionBuilder
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{
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const CONNECT_INTERVAL = 0.1;
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const RESOLVE_WAIT = 0.5;
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public $loop;
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public $connector;
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public $resolver;
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public $uri;
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public $host;
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public $resolved = array(
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Message::TYPE_A => false,
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Message::TYPE_AAAA => false,
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);
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public $resolverPromises = array();
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public $connectionPromises = array();
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public $connectQueue = array();
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public $timer;
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public $parts;
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public $ipsCount = 0;
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public $failureCount = 0;
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public $resolve;
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public $reject;
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public function __construct(LoopInterface $loop, ConnectorInterface $connector, ResolverInterface $resolver, $uri, $host, $parts)
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{
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$this->loop = $loop;
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$this->connector = $connector;
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$this->resolver = $resolver;
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$this->uri = $uri;
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$this->host = $host;
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$this->parts = $parts;
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}
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public function connect()
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{
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$that = $this;
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return new Promise\Promise(function ($resolve, $reject) use ($that) {
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$lookupResolve = function ($type) use ($that, $resolve, $reject) {
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return function (array $ips) use ($that, $type, $resolve, $reject) {
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unset($that->resolverPromises[$type]);
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$that->resolved[$type] = true;
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$that->mixIpsIntoConnectQueue($ips);
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if ($that->timer instanceof TimerInterface) {
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return;
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}
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$that->check($resolve, $reject);
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};
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};
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$ipv4Deferred = null;
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$that->resolverPromises[Message::TYPE_AAAA] = $that->resolve(Message::TYPE_AAAA, $reject)->then($lookupResolve(Message::TYPE_AAAA))->then(function () use (&$ipv4Deferred) {
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if ($ipv4Deferred instanceof Promise\Deferred) {
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$ipv4Deferred->resolve();
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}
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});
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$that->resolverPromises[Message::TYPE_A] = $that->resolve(Message::TYPE_A, $reject)->then(function ($ips) use ($that, &$ipv4Deferred) {
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if ($that->resolved[Message::TYPE_AAAA] === true) {
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return Promise\resolve($ips);
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}
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/**
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* Delay A lookup by 50ms sending out connection to IPv4 addresses when IPv6 records haven't
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* resolved yet as per RFC.
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*
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* @link https://tools.ietf.org/html/rfc8305#section-3
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*/
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$ipv4Deferred = new Promise\Deferred();
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$deferred = new Promise\Deferred();
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$timer = $that->loop->addTimer($that::RESOLVE_WAIT, function () use ($deferred, $ips) {
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$ipv4Deferred = null;
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$deferred->resolve($ips);
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});
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$ipv4Deferred->promise()->then(function () use ($that, $timer, $deferred, $ips) {
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$that->loop->cancelTimer($timer);
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$deferred->resolve($ips);
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});
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return $deferred->promise();
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})->then($lookupResolve(Message::TYPE_A));
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}, function ($_, $reject) use ($that) {
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$that->cleanUp();
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$reject(new \RuntimeException('Connection to ' . $that->uri . ' cancelled during DNS lookup'));
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$_ = $reject = null;
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});
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}
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/**
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* @internal
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*/
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public function resolve($type, $reject)
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{
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$that = $this;
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return $that->resolver->resolveAll($that->host, $type)->then(null, function () use ($type, $reject, $that) {
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unset($that->resolverPromises[$type]);
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$that->resolved[$type] = true;
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if ($that->hasBeenResolved() === false) {
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return;
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}
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if ($that->ipsCount === 0) {
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$that->resolved = null;
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$that->resolverPromises = null;
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$reject(new \RuntimeException('Connection to ' . $that->uri . ' failed during DNS lookup: DNS error'));
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}
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});
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}
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/**
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* @internal
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*/
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public function check($resolve, $reject)
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{
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$ip = \array_shift($this->connectQueue);
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if (\count($this->connectQueue) === 0 && $this->resolved[Message::TYPE_A] === true && $this->resolved[Message::TYPE_AAAA] === true && $this->timer instanceof TimerInterface) {
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$this->loop->cancelTimer($this->timer);
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$this->timer = null;
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}
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if ($ip === null) {
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return;
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}
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$that = $this;
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$that->connectionPromises[$ip] = $this->attemptConnection($ip)->then(function ($connection) use ($that, $ip, $resolve) {
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unset($that->connectionPromises[$ip]);
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$that->cleanUp();
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$resolve($connection);
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}, function () use ($that, $ip, $resolve, $reject) {
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unset($that->connectionPromises[$ip]);
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$that->failureCount++;
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if ($that->hasBeenResolved() === false) {
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return;
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}
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if ($that->ipsCount === $that->failureCount) {
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$that->cleanUp();
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$reject(new \RuntimeException('All attempts to connect to "' . $that->host . '" have failed'));
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}
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});
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/**
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* As long as we haven't connected yet keep popping an IP address of the connect queue until one of them
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* succeeds or they all fail. We will wait 100ms between connection attempts as per RFC.
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*
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* @link https://tools.ietf.org/html/rfc8305#section-5
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*/
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if ((\count($this->connectQueue) > 0 || ($this->resolved[Message::TYPE_A] === false || $this->resolved[Message::TYPE_AAAA] === false)) && $this->timer === null) {
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$this->timer = $this->loop->addPeriodicTimer(self::CONNECT_INTERVAL, function () use ($that, $resolve, $reject) {
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$that->check($resolve, $reject);
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});
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}
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}
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/**
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* @internal
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*/
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public function attemptConnection($ip)
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{
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$promise = null;
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$that = $this;
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return new Promise\Promise(
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function ($resolve, $reject) use (&$promise, $that, $ip) {
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$uri = '';
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// prepend original scheme if known
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if (isset($that->parts['scheme'])) {
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$uri .= $that->parts['scheme'] . '://';
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}
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if (\strpos($ip, ':') !== false) {
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// enclose IPv6 addresses in square brackets before appending port
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$uri .= '[' . $ip . ']';
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} else {
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$uri .= $ip;
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}
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// append original port if known
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if (isset($that->parts['port'])) {
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$uri .= ':' . $that->parts['port'];
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}
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// append orignal path if known
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if (isset($that->parts['path'])) {
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$uri .= $that->parts['path'];
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}
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// append original query if known
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if (isset($that->parts['query'])) {
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$uri .= '?' . $that->parts['query'];
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}
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// append original hostname as query if resolved via DNS and if
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// destination URI does not contain "hostname" query param already
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$args = array();
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\parse_str(isset($that->parts['query']) ? $that->parts['query'] : '', $args);
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if ($that->host !== $ip && !isset($args['hostname'])) {
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$uri .= (isset($that->parts['query']) ? '&' : '?') . 'hostname=' . \rawurlencode($that->host);
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}
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// append original fragment if known
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if (isset($that->parts['fragment'])) {
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$uri .= '#' . $that->parts['fragment'];
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}
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$promise = $that->connector->connect($uri);
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$promise->then($resolve, $reject);
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},
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function ($_, $reject) use (&$promise, $that) {
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// cancellation should reject connection attempt
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// (try to) cancel pending connection attempt
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$reject(new \RuntimeException('Connection to ' . $that->uri . ' cancelled during connection attempt'));
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if ($promise instanceof CancellablePromiseInterface) {
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// overwrite callback arguments for PHP7+ only, so they do not show
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// up in the Exception trace and do not cause a possible cyclic reference.
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$_ = $reject = null;
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$promise->cancel();
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$promise = null;
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}
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}
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);
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}
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/**
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* @internal
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*/
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public function cleanUp()
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{
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/** @var CancellablePromiseInterface $promise */
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foreach ($this->connectionPromises as $index => $connectionPromise) {
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if ($connectionPromise instanceof CancellablePromiseInterface) {
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$connectionPromise->cancel();
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}
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}
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/** @var CancellablePromiseInterface $promise */
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foreach ($this->resolverPromises as $index => $resolverPromise) {
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if ($resolverPromise instanceof CancellablePromiseInterface) {
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$resolverPromise->cancel();
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}
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}
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if ($this->timer instanceof TimerInterface) {
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$this->loop->cancelTimer($this->timer);
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$this->timer = null;
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}
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}
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/**
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* @internal
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*/
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public function hasBeenResolved()
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{
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foreach ($this->resolved as $typeHasBeenResolved) {
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if ($typeHasBeenResolved === false) {
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return false;
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}
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}
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return true;
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}
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/**
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* Mixes an array of IP addresses into the connect queue in such a way they alternate when attempting to connect.
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* The goal behind it is first attempt to connect to IPv6, then to IPv4, then to IPv6 again until one of those
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* attempts succeeds.
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*
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* @link https://tools.ietf.org/html/rfc8305#section-4
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*
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* @internal
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*/
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public function mixIpsIntoConnectQueue(array $ips)
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{
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$this->ipsCount += \count($ips);
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$connectQueueStash = $this->connectQueue;
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$this->connectQueue = array();
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while (\count($connectQueueStash) > 0 || \count($ips) > 0) {
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if (\count($ips) > 0) {
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$this->connectQueue[] = \array_shift($ips);
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}
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if (\count($connectQueueStash) > 0) {
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$this->connectQueue[] = \array_shift($connectQueueStash);
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}
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}
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}
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}

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