From 22c90049f38e222828e31c10031a8f7db6782c2a Mon Sep 17 00:00:00 2001
From: Chris Wright <daverandom@php.net>
Date: Tue, 17 Jun 2014 18:01:10 +0100
Subject: [PATCH] Handle CNAME resource records correctly

---
 lib/Addr/AddressModes.php        |  1 +
 lib/Addr/Client.php              | 43 ++++++++++++++++++++++++----
 lib/Addr/ResponseInterpreter.php | 48 +++++++++++++++++++++++++++-----
 3 files changed, 79 insertions(+), 13 deletions(-)

diff --git a/lib/Addr/AddressModes.php b/lib/Addr/AddressModes.php
index 7c80c02..b8cccd5 100644
--- a/lib/Addr/AddressModes.php
+++ b/lib/Addr/AddressModes.php
@@ -7,4 +7,5 @@ class AddressModes
     const INET4_ADDR = 1;
     const INET6_ADDR = 2;
     const PREFER_INET6 = 4;
+    const CNAME = 8;
 }
diff --git a/lib/Addr/Client.php b/lib/Addr/Client.php
index 8227b0d..6ba8c6b 100644
--- a/lib/Addr/Client.php
+++ b/lib/Addr/Client.php
@@ -198,24 +198,40 @@ class Client
     {
         $packet = fread($this->socket, 512);
 
-        $response = $this->responseInterpreter->interpret($packet);
-        if ($response === null) {
+        // Decode the response and clean up the pending requests list
+        $decoded = $this->responseInterpreter->decode($packet);
+        if ($decoded === null) {
             return;
         }
 
-        list($id, $addr, $ttl) = $response;
+        list($id, $response) = $decoded;
         $request = $this->pendingRequestsById[$id];
-        $type = $request['type'];
         $name = $request['name'];
 
         $this->reactor->cancel($request['timeout_id']);
-        unset($this->pendingRequestsById[$id], $this->pendingRequestsByNameAndType[$name][$type]);
+        unset($this->pendingRequestsById[$id], $this->pendingRequestsByNameAndType[$name][$request['type']]);
         if (!$this->pendingRequestsById) {
             $this->reactor->cancel($this->readWatcherId);
             $this->readWatcherId = null;
         }
 
-        if ($addr !== null) {
+        // Interpret the response and make sure we have at least one resource record
+        $interpreted = $this->responseInterpreter->interpret($response, $request['type']);
+        if ($interpreted === null) {
+            foreach ($request['lookups'] as $id => $lookup) {
+                $this->processPendingLookup($id);
+            }
+
+            return;
+        }
+
+        // Distribute the result to the appropriate lookup routine
+        list($type, $addr, $ttl) = $interpreted;
+        if ($type === AddressModes::CNAME) {
+            foreach ($request['lookups'] as $id => $lookup) {
+                $this->redirectPendingLookup($id, $addr);
+            }
+        } else if ($addr !== null) {
             if ($request['cache_store']) {
                 call_user_func($request['cache_store'], $name, $addr, $type, $ttl);
             }
@@ -277,6 +293,21 @@ class Client
         }
     }
 
+    /**
+     * Redirect a lookup to search for another name
+     *
+     * @param int $id
+     * @param string $name
+     */
+    private function redirectPendingLookup($id, $name)
+    {
+        array_unshift($this->pendingLookups[$id]['requests'], $this->pendingLookups[$id]['last_type']);
+        $this->pendingLookups[$id]['last_type'] = null;
+        $this->pendingLookups[$id]['name'] = $name;
+
+        $this->processPendingLookup($id);
+    }
+
     /**
      * Resolve a name from a server
      *
diff --git a/lib/Addr/ResponseInterpreter.php b/lib/Addr/ResponseInterpreter.php
index 859fe57..ec0aa13 100644
--- a/lib/Addr/ResponseInterpreter.php
+++ b/lib/Addr/ResponseInterpreter.php
@@ -3,7 +3,9 @@
 namespace Addr;
 
 use LibDNS\Decoder\Decoder,
-    LibDNS\Messages\MessageTypes;
+    LibDNS\Messages\Message,
+    LibDNS\Messages\MessageTypes,
+    LibDNS\Records\ResourceTypes;
 
 class ResponseInterpreter
 {
@@ -23,12 +25,12 @@ class ResponseInterpreter
     }
 
     /**
-     * Extract the message ID and response data from a DNS response packet
+     * Attempt to decode a data packet to a DNS response message
      *
      * @param string $packet
-     * @return array|null
+     * @return Message|null
      */
-    public function interpret($packet)
+    public function decode($packet)
     {
         try {
             $message = $this->decoder->decode($packet);
@@ -40,13 +42,45 @@ class ResponseInterpreter
             return null;
         }
 
+        return [$message->getID(), $message];
+    }
+
+    /**
+     * Extract the message ID and response data from a DNS response packet
+     *
+     * @param Message $message
+     * @param int $expectedType
+     * @return array|null
+     */
+    public function interpret($message, $expectedType)
+    {
+        static $typeMap = [
+            AddressModes::INET4_ADDR => ResourceTypes::A,
+            AddressModes::INET6_ADDR => ResourceTypes::AAAA,
+        ];
+
         $answers = $message->getAnswerRecords();
         if (!count($answers)) {
-            return [$message->getID(), null];
+            return null;
         }
 
         /** @var \LibDNS\Records\Resource $record */
-        $record = $answers->getRecordByIndex(0);
-        return [$message->getID(), (string)$record->getData(), $record->getTTL()];
+        $cname = null;
+        foreach ($answers as $record) {
+            switch ($record->getType()) {
+                case $typeMap[$expectedType]:
+                    return [$expectedType, (string)$record->getData(), $record->getTTL()];
+
+                case ResourceTypes::CNAME:
+                    $cname = (string)$record->getData();
+                    break;
+            }
+        }
+
+        if ($cname) {
+            return [AddressModes::CNAME, $cname, null];
+        }
+
+        return null;
     }
 }