kitchen drain stinking

[villageidiotY2K]

Hello folks, ive noticed this musty stinky smell coming out of my kitchen cabinet and im guessing below pic is the suspect drain under the sink.

the plastic tube seems stuffed with gunk and i woulike to change the whole plastic thingies.

but as the first pic, is the plastic white tube connected direct to the pipe? or is there fastners to tighten up by dialing?

 

Or is it better to just flush the system with some corrosive drain cleaners?