Nginx FastCGI question

[Some Developer]

Hi,

When you run a FastCGI application behind Nginx does Nginx pass all the 
HTTP request headers to the FastCGI server / app? Or do you need to 
explicitly pass them using fastcgi_param?

If Nginx does pass them, does it pass them all or only a subset of the 
request headers? The FastCGI specification is not at all clear on 
whether the HTTP headers are passed or not.

Also in the same way I've read through the FastCGI specification and can 
find no information in which states which entity is responsible for 
generating all the HTTP response headers. I would assume it would be my 
FastCGI app and Nginx just forwards it on but does Nginx add or modify 
any headers after I have sent my response from my FastCGI app back to Nginx?

Thanks.