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 objects 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).