There is control. Even, we build Fence also along border. But Border is very long 4,000+ KM with few loop holes. Hence, Some comes to India illegally for some work. They come and live illegally in large country. 90% Bangladeshi are poor although and work as Vote Bank politics. Hence, Actions are not taken yet. Although it is major concern and After few years when BJP will come in power action will be taken.
Even 1/2 Bangladeshi killed crossing border illegally, BD posters says "BSF is Killing" Lol.
India-Pakistan is different Case. Border is Strict also due to various conflict. But BD is different league. Many BD posters says "Haseena is an Indian Agent". So, you can imagine the strength of BD.