title: ESP8266 Core 1.3.0 and Lwip sources
body: <p>i am trying to modify the lwip to get additional functionality.
  However i am unable to pair my ESP8266 core version with lwip sources.</p>
  
  <p>Here is what ESP returns by calling:</p>
  
  <pre><code>Serial.printf( "SDK: %s\n", ESP.getSdkVersion() );
  </code></pre>
  
  <p>Output:</p>
  
  <blockquote>
    <p>SDK: 1.3.0</p>
  </blockquote>
  
  <p>In this version, the lwip is stored in libraries/ESP8266WIFI - but there are no sources to compile, only headers and already built library:</p>
  
  <p><a href="https://i.stack.imgur.com/ZPZHt.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ZPZHt.png" alt="enter image description here"></a></p>
  
  <p><a href="https://i.stack.imgur.com/AESsj.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AESsj.png" alt="enter image description here"></a></p>
  
  <p>How do i get the lwip sources for this ESP8266 Core version please?</p>