SSL_set_bio.3ssl man page

SSL_set_bio, SSL_set0_rbio, SSL_set0_wbio — connect the SSL object with a BIO


#include <openssl/ssl.h>
void SSL_set_bio(SSL *ssl, BIO *rbio, BIO *wbio);
void SSL_set0_rbio(SSL *s, BIO *rbio);
void SSL_set0_wbio(SSL *s, BIO *wbio);


SSL_set0_rbio() connects the BIO rbio for the read operations of the ssl object. The SSL engine inherits the behaviour of rbio. If the BIO is non-blocking then the ssl object will also have non-blocking behaviour. This function transfers ownership of rbio to ssl. It will be automatically freed using BIO_free_all(3) when the ssl is freed. On calling this function, any existing rbio that was previously set will also be freed via a call to BIO_free_all(3) (this includes the case where the rbio is set to the same value as previously).

SSL_set0_wbio() works in the same as SSL_set0_rbio() except that it connects the BIO wbio for the write operations of the ssl object. Note that if the rbio and wbio are the same then SSL_set0_rbio() and SSL_set0_wbio() each take ownership of one reference. Therefore it may be necessary to increment the number of references available using BIO_up_ref(3) before calling the set0 functions.

SSL_set_bio() does a similar job as SSL_set0_rbio() and SSL_set0_wbio() except that it connects both the rbio and the wbio at the same time. This function transfers the ownership of rbio and wbio to ssl except that the rules for this are much more complex. For this reason this function is considered a legacy function and SSL_set0_rbio() and SSL_set0_wbio() should be used in preference. The ownership rules are as follows:

Return Values

SSL_set_bio(), SSL_set_rbio() and SSL_set_wbio() cannot fail.

See Also

SSL_get_rbio(3), SSL_connect(3), SSL_accept(3), SSL_shutdown(3), ssl(3), bio(3)


SSL_set0_rbio() and SSL_set0_wbio() were added in OpenSSL 1.1.0.