Is it possible to have the Unity plug-in perform OpenGLES operations?

I would like to process OpenGLES with the Unity plug-in (dll side) and reflect it to Unity side.

Find out how
https://docs.unity3d.com/ja/540/Manual/NativePluginInterface.html

in such a way that Unity generates the substance of the texture and rewrites the content. Samples and contents were listed.
(There were a lot of articles that verified the above in the search results to see if the method of investigation was bad.)

What I want to implement is

glEnable(GL_TEXTURE_2D);
glGenTextures(1,&m_TexID);
glBindTexture(GL_TEXTURE_2D, m_TexID);

Call to generate textures on the dll side and draw them on the Unity side

glClearColor(r,g,b,a);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

Use to clear the screen or

glViewport(x,y,w,h);

Is it possible to use to specify a viewport?

実行 The running environment is Unity 5.6.0f3, and
Player Setting to work with OpenGLES Changing the Auto Graphics API.

Also
https://docs.unity3d.com/ja/540/ScriptReference/GL.InvalidateState.html

GL.InvalidateState();

Is it necessary to use ?
(I couldn't even find a GL.InvalidateState use case, so
I couldn't decide whether the reference content is relevant or when to use it.)

I would appreciate it if you could let me know if anyone is familiar with it.