SSL_set_session.3ssl man page
SSL_set_session — set a TLS/SSL session to be used during TLS/SSL connect
#include <openssl/ssl.h> int SSL_set_session(SSL *ssl, SSL_SESSION *session);
SSL_set_session() sets session to be used when the TLS/SSL connection is to be established. SSL_set_session() is only useful for TLS/SSL clients. When the session is set, the reference count of session is incremented by 1. If the session is not reused, the reference count is decremented again during SSL_connect(). Whether the session was reused can be queried with the SSL_session_reused(3) call.
If there is already a session set inside ssl (because it was set with SSL_set_session() before or because the same ssl was already used for a connection), SSL_SESSION_free() will be called for that session.
SSL_SESSION objects keep internal link information about the session cache list, when being inserted into one SSL_CTX object's session cache. One SSL_SESSION object, regardless of its reference count, must therefore only be used with one SSL_CTX object (and the SSL objects created from this SSL_CTX object).
The following return values can occur:
The operation failed; check the error stack to find out the reason.
The operation succeeded.
ssl(3), SSL_SESSION_free(3), SSL_get_session(3), SSL_session_reused(3), SSL_CTX_set_session_cache_mode(3)