man SSL_CTX_sessions () - access internal session cache
NAME
SSL_CTX_sessions - access internal session cache
SYNOPSIS
#include <openssl/ssl.h>
struct lhash_st *SSL_CTX_sessions(SSL_CTX *ctx);
DESCRIPTION
SSL_CTX_sessions() returns a pointer to the lhash databases containing the internal session cache for ctx.
NOTES
The sessions in the internal session cache are kept in an lhash(3) type database. It is possible to directly access this database e.g. for searching. In parallel, the sessions form a linked list which is maintained separately from the lhash(3) operations, so that the database must not be modified directly but by using the SSL_CTX_add_session(3) family of functions.