b126dbe3f2
The functions returning null or the class property is set explict null Found by phan strict checks Change-Id: I4a271093fb6526564d8083a08249c64cb21f2453
147 lines
3.5 KiB
PHP
147 lines
3.5 KiB
PHP
<?php
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/**
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* Service discovery using DNS SRV records
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* http://www.gnu.org/copyleft/gpl.html
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*
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* @file
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*/
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/**
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* @since 1.29
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*/
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class DnsSrvDiscoverer {
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/**
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* @var string
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*/
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private $service;
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/**
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* @var string
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*/
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private $protocol;
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/**
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* @var string|null
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*/
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private $domain;
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/**
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* @var callable
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*/
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private $resolver;
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/**
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* Construct a new discoverer for the given domain, service, and protocol.
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*
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* @param string $service Name of the service to discover.
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* @param string $protocol Service protocol. Defaults to 'tcp'
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* @param ?string $domain The hostname/domain on which to perform discovery
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* of the given service and protocol. Defaults to null which effectively
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* performs a query relative to the host's configured search domain.
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* @param ?callable $resolver Resolver function. Defaults to using
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* dns_get_record. Primarily useful in testing.
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*/
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public function __construct(
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string $service,
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string $protocol = 'tcp',
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?string $domain = null,
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?callable $resolver = null
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) {
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$this->service = $service;
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$this->protocol = $protocol;
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$this->domain = $domain;
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$this->resolver = $resolver ?? static function ( $srv ) {
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return dns_get_record( $srv, DNS_SRV );
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};
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}
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/**
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* Queries the resolver for an SRV resource record matching the service,
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* protocol, and domain and returns all target/port/priority/weight
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* records.
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*
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* @return array
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*/
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public function getRecords() {
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$result = [];
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$records = ( $this->resolver )( $this->getSrvName() );
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// Respect RFC 2782 with regard to a single '.' entry denoting a valid
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// empty response
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if (
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!$records
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|| ( count( $records ) === 1 && $records[0]['target'] === '.' )
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) {
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return $result;
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}
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foreach ( $records as $record ) {
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$result[] = [
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'target' => $record['target'],
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'port' => (int)$record['port'],
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'pri' => (int)$record['pri'],
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'weight' => (int)$record['weight'],
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];
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}
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return $result;
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}
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/**
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* Performs discovery for the domain, service, and protocol, and returns a
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* list of resolved server name/ip and port number pairs sorted by each
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* record's priority, with servers of the same priority randomly shuffled.
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*
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* @return array
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*/
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public function getServers() {
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$records = $this->getRecords();
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usort( $records, static function ( $a, $b ) {
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if ( $a['pri'] === $b['pri'] ) {
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return mt_rand( 0, 1 ) ? 1 : -1;
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}
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return $a['pri'] - $b['pri'];
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} );
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$serversAndPorts = [];
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foreach ( $records as $record ) {
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$serversAndPorts[] = [ $record['target'], $record['port'] ];
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}
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return $serversAndPorts;
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}
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/**
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* Returns the SRV resource record name.
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*
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* @return string
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*/
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public function getSrvName(): string {
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$srv = "_{$this->service}._{$this->protocol}";
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if ( $this->domain === null || $this->domain === '' ) {
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return $srv;
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}
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return "$srv.{$this->domain}";
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}
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}
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