make sure that TCP_CORK is supported

History.md

@@ -2,6 +2,7 @@
 * Bugfixes
   * Resolve issue with threadpool waiting counter decrement when thread is killed
   * Constrain rake-compiler version to 0.9.4 to fix `ClassNotFound` exception when using MiniSSL with Java8.
+  * Ensure that TCP_CORK is usable
 
 ## 5.0.0
 

lib/puma/server.rb

@@ -98,26 +98,38 @@ def inherit_binder(bind)
       @binder = bind
     end
 
+    class << self
+      # :nodoc:
+      def tcp_cork_supported?
+        RbConfig::CONFIG['host_os'] =~ /linux/ &&
+          Socket.const_defined?(:IPPROTO_TCP) &&
+          Socket.const_defined?(:TCP_CORK) &&
+          Socket.const_defined?(:SOL_TCP) &&
+          Socket.const_defined?(:TCP_INFO)
+      end
+      private :tcp_cork_supported?
+    end
+
     # On Linux, use TCP_CORK to better control how the TCP stack
     # packetizes our stream. This improves both latency and throughput.
     #
-    if RbConfig::CONFIG['host_os'] =~ /linux/
+    if tcp_cork_supported?
       UNPACK_TCP_STATE_FROM_TCP_INFO = "C".freeze
 
       # 6 == Socket::IPPROTO_TCP
       # 3 == TCP_CORK
       # 1/0 == turn on/off
       def cork_socket(socket)
         begin
-          socket.setsockopt(6, 3, 1) if socket.kind_of? TCPSocket
+          socket.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_CORK, 1) if socket.kind_of? TCPSocket
         rescue IOError, SystemCallError
           Thread.current.purge_interrupt_queue if Thread.current.respond_to? :purge_interrupt_queue
         end
       end
 
       def uncork_socket(socket)
         begin
-          socket.setsockopt(6, 3, 0) if socket.kind_of? TCPSocket
+          socket.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_CORK, 0) if socket.kind_of? TCPSocket
         rescue IOError, SystemCallError
           Thread.current.purge_interrupt_queue if Thread.current.respond_to? :purge_interrupt_queue
         end