From 5586250c2ebbbd1c0d394c068c249081e3d34949 Mon Sep 17 00:00:00 2001
From: Olivier Bellone <ob@stripe.com>
Date: Tue, 2 Apr 2019 11:10:57 -0700
Subject: [PATCH] Only use HTTP/2 with curl >= 7.60.0

---
 lib/HttpClient/CurlClient.php | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/lib/HttpClient/CurlClient.php b/lib/HttpClient/CurlClient.php
index c9155ca61..01ed67203 100644
--- a/lib/HttpClient/CurlClient.php
+++ b/lib/HttpClient/CurlClient.php
@@ -44,6 +44,8 @@ public static function instance()
 
     protected $enablePersistentConnections = null;
 
+    protected $enableHttp2 = null;
+
     protected $curlHandle = null;
 
     /**
@@ -68,6 +70,8 @@ public function __construct($defaultOptions = null, $randomGenerator = null)
         // TODO: curl_reset requires PHP >= 5.5.0. Once we drop support for PHP 5.4, we can simply
         // initialize this to true.
         $this->enablePersistentConnections = function_exists('curl_reset');
+
+        $this->enableHttp2 = $this->canSafelyUseHttp2();
     }
 
     public function __destruct()
@@ -110,6 +114,22 @@ public function setEnablePersistentConnections($enable)
         $this->enablePersistentConnections = $enable;
     }
 
+    /**
+     * @return boolean
+     */
+    public function getEnableHttp2()
+    {
+        return $this->enableHttp2;
+    }
+
+    /**
+     * @param boolean $enable
+     */
+    public function setEnableHttp2($enable)
+    {
+        $this->enableHttp2 = $enable;
+    }
+
     // USER DEFINED TIMEOUTS
 
     const DEFAULT_TIMEOUT = 80;
@@ -228,7 +248,7 @@ public function request($method, $absUrl, $headers, $params, $hasFile)
             $opts[CURLOPT_SSL_VERIFYPEER] = false;
         }
 
-        if (!isset($opts[CURLOPT_HTTP_VERSION])) {
+        if (!isset($opts[CURLOPT_HTTP_VERSION]) && $this->getEnableHttp2()) {
             // For HTTPS requests, enable HTTP/2, if supported
             $opts[CURLOPT_HTTP_VERSION] = CURL_HTTP_VERSION_2TLS;
         }
@@ -406,4 +426,17 @@ private function resetCurlHandle()
             $this->initCurlHandle();
         }
     }
+
+    /**
+     * Indicates whether it is safe to use HTTP/2 or not.
+     *
+     * @return boolean
+     */
+    private function canSafelyUseHttp2()
+    {
+        // Versions of curl older than 7.60.0 don't respect GOAWAY frames
+        // (cf. https://github.com/curl/curl/issues/2416), which Stripe use.
+        $curlVersion = curl_version()['version'];
+        return (version_compare($curlVersion, '7.60.0') >= 0);
+    }
 }