ssl_ctx_st
typedef struct ssl_ctx_st SSL_CTX;
void (*remove_session_cb)(struct ssl_ctx_st *ctx, SSL_SESSION *sess));
void (*SSL_CTX_sess_get_remove_cb(SSL_CTX *ctx))(struct ssl_ctx_st *ctx,
void (*remove_session_cb)(struct ssl_ctx_st *ctx, SSL_SESSION *sess);