Support parsing DNS config from WMIC on Windows

src/Config/Config.php

@@ -17,7 +17,7 @@ class Config
      *
      * Note that this method will try to access its files and/or commands and
      * try to parse its output. Currently, this will only parse valid nameserver
-     * entries from `/etc/resolv.conf` and will ignore all other output without
+     * entries from its output and will ignore all other output without
      * complaining.
      *
      * Note that the previous section implies that this may return an empty
@@ -28,6 +28,12 @@ class Config
      */
     public static function loadSystemConfigBlocking()
     {
+        // Use WMIC output on Windows
+        if (DIRECTORY_SEPARATOR === '\\') {
+            return self::loadWmicBlocking();
+        }
+
+        // otherwise (try to) load from resolv.conf
         try {
             return self::loadResolvConfBlocking();
         } catch (RuntimeException $ignored) {
@@ -84,5 +90,38 @@ public static function loadResolvConfBlocking($path = null)
         return $config;
     }
 
+    /**
+     * Loads the DNS configurations from Windows's WMIC (from the given command or default command)
+     *
+     * Note that this method blocks while loading the given command and should
+     * thus be used with care! While this should be relatively fast for normal
+     * WMIC commands, it remains unknown if this may block under certain
+     * circumstances. In particular, this method should only be executed before
+     * the loop starts, not while it is running.
+     *
+     * Note that this method will only try to execute the given command try to
+     * parse its output, irrespective of whether this command exists. In
+     * particular, this command is only available on Windows. Currently, this
+     * will only parse valid nameserver entries from the command output and will
+     * ignore all other output without complaining.
+     *
+     * Note that the previous section implies that this may return an empty
+     * `Config` object if no valid nameserver entries can be found.
+     *
+     * @param ?string $command (advanced) should not be given (NULL) unless you know what you're doing
+     * @return self
+     * @link https://ss64.com/nt/wmic.html
+     */
+    public static function loadWmicBlocking($command = null)
+    {
+        $contents = shell_exec($command === null ? 'wmic NICCONFIG get "DNSServerSearchOrder" /format:CSV' : $command);
+        preg_match_all('/(?:{|,|")([\da-f.:]{4,})(?:}|,|")/i', $contents, $matches);
+
+        $config = new self();
+        $config->nameservers = $matches[1];
+
+        return $config;
+    }
+
     public $nameservers = array();
 }

tests/Config/ConfigTest.php

@@ -95,4 +95,80 @@ public function testParsesFileAndIgnoresCommentsAndInvalidNameserverEntries()
         $config = Config::loadResolvConfBlocking('data://text/plain;base64,' . base64_encode($contents));
         $this->assertEquals($expected, $config->nameservers);
     }
+
+    public function testLoadsFromWmicOnWindows()
+    {
+        if (DIRECTORY_SEPARATOR !== '\\') {
+            $this->markTestSkipped('Only on Windows');
+        }
+
+        $config = Config::loadWmicBlocking();
+
+        $this->assertInstanceOf('React\Dns\Config\Config', $config);
+    }
+
+    public function testLoadsSingleEntryFromWmicOutput()
+    {
+        $contents = '
+Node,DNSServerSearchOrder
+ACE,
+ACE,{192.168.2.1}
+ACE,
+';
+        $expected = array('192.168.2.1');
+
+        $config = Config::loadWmicBlocking($this->echoCommand($contents));
+
+        $this->assertEquals($expected, $config->nameservers);
+    }
+
+    public function testLoadsEmptyListFromWmicOutput()
+    {
+        $contents = '
+Node,DNSServerSearchOrder
+ACE,
+';
+        $expected = array();
+
+        $config = Config::loadWmicBlocking($this->echoCommand($contents));
+
+        $this->assertEquals($expected, $config->nameservers);
+    }
+
+    public function testLoadsSingleEntryForMultipleNicsFromWmicOutput()
+    {
+        $contents = '
+Node,DNSServerSearchOrder
+ACE,
+ACE,{192.168.2.1}
+ACE,
+ACE,{192.168.2.2}
+ACE,
+';
+        $expected = array('192.168.2.1', '192.168.2.2');
+
+        $config = Config::loadWmicBlocking($this->echoCommand($contents));
+
+        $this->assertEquals($expected, $config->nameservers);
+    }
+
+    public function testLoadsMultipleEntriesForSingleNicFromWmicOutput()
+    {
+        $contents = '
+Node,DNSServerSearchOrder
+ACE,
+ACE,{"192.168.2.1","192.168.2.2"}
+ACE,
+';
+        $expected = array('192.168.2.1', '192.168.2.2');
+
+        $config = Config::loadWmicBlocking($this->echoCommand($contents));
+
+        $this->assertEquals($expected, $config->nameservers);
+    }
+
+    private function echoCommand($output)
+    {
+        return 'echo ' . escapeshellarg($output);
+    }
 }