BIO_f_null.3ssl man page
BIO_f_null — null filter
#include <openssl/bio.h> BIO_METHOD * BIO_f_null(void);
BIO_f_null() returns the null filter BIO method. This is a filter BIO that does nothing.
All requests to a null filter BIO are passed through to the next BIO in the chain: this means that a BIO chain containing a null filter BIO behaves just as though the BIO was not there.
As may be apparent a null filter BIO is not particularly useful.
BIO_f_null() returns the null filter BIO method.