SSL_CTX_set_psk_client_callback
SSL_CTX_set_psk_client_callback(ctx, dummy_psk);
SSL_CTX_set_psk_client_callback(ctx, psk_client_cb);
void SSL_CTX_set_psk_client_callback(SSL_CTX *ctx, SSL_psk_client_cb_func cb);
SSL_CTX_set_psk_client_callback(ctx, clnt_psk_callback);
SSL_CTX_set_psk_client_callback(ctx, clnt_psk_callback);
SSL_CTX_set_psk_client_callback(c_ctx, psk_client_callback);
SSL_CTX_set_psk_client_callback(cctx, psk_client_cb);