1 files changed, 108 insertions, 0 deletions
diff --git a/www/wiki/includes/libs/DnsSrvDiscoverer.php b/www/wiki/includes/libs/DnsSrvDiscoverer.php
new file mode 100644
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+++ b/www/wiki/includes/libs/DnsSrvDiscoverer.php
@@ -0,0 +1,108 @@
+<?php
+/**
+ * Service discovery using DNS SRV records
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+
+/**
+ * @since 1.29
+ */
+class DnsSrvDiscoverer {
+	/**
+	 * @var string
+	 */
+	private $domain;
+
+	/**
+	 * @param string $domain
+	 */
+	public function __construct( $domain ) {
+		$this->domain = $domain;
+	}
+
+	/**
+	 * Fetch the servers with a DNS SRV request
+	 *
+	 * @return array
+	 */
+	public function getServers() {
+		$result = [];
+		foreach ( $this->getDnsRecords() as $record ) {
+			$result[] = [
+				'target' => $record['target'],
+				'port' => $record['port'],
+				'pri' => $record['pri'],
+				'weight' => $record['weight'],
+			];
+		}
+
+		return $result;
+	}
+
+	/**
+	 * Pick a server according to the priority fields.
+	 * Note that weight is currently ignored.
+	 *
+	 * @param array $servers from getServers
+	 * @return array|bool
+	 */
+	public function pickServer( array $servers ) {
+		if ( !$servers ) {
+			return false;
+		}
+
+		$srvsByPrio = [];
+		foreach ( $servers as $server ) {
+			$srvsByPrio[$server['pri']][] = $server;
+		}
+
+		$min = min( array_keys( $srvsByPrio ) );
+		if ( count( $srvsByPrio[$min] ) == 1 ) {
+			return $srvsByPrio[$min][0];
+		} else {
+			// Choose randomly
+			$rand = mt_rand( 0, count( $srvsByPrio[$min] ) - 1 );
+
+			return $srvsByPrio[$min][$rand];
+		}
+	}
+
+	/**
+	 * @param array $server
+	 * @param array $servers
+	 * @return array[]
+	 */
+	public function removeServer( $server, array $servers ) {
+		foreach ( $servers as $i => $srv ) {
+			if ( $srv['target'] === $server['target'] && $srv['port'] === $server['port'] ) {
+				unset( $servers[$i] );
+				break;
+			}
+		}
+
+		return array_values( $servers );
+	}
+
+	/**
+	 * @return array[]
+	 */
+	protected function getDnsRecords() {
+		return dns_get_record( $this->domain, DNS_SRV );
+	}
+}