+/* Attempts to install 'key' into the datapath, fetches it, then deletes it.
+ * Returns true if the datapath supported installing 'flow', false otherwise.
+ */
+bool
+dpif_probe_feature(struct dpif *dpif, const char *name,
+ const struct ofpbuf *key, const ovs_u128 *ufid)
+{
+ struct dpif_flow flow;
+ struct ofpbuf reply;
+ uint64_t stub[DPIF_FLOW_BUFSIZE / 8];
+ bool enable_feature = false;
+ int error;
+
+ /* Use DPIF_FP_MODIFY to cover the case where ovs-vswitchd is killed (and
+ * restarted) at just the right time such that feature probes from the
+ * previous run are still present in the datapath. */
+ error = dpif_flow_put(dpif, DPIF_FP_CREATE | DPIF_FP_MODIFY | DPIF_FP_PROBE,
+ key->data, key->size, NULL, 0, NULL, 0,
+ ufid, PMD_ID_NULL, NULL);
+ if (error) {
+ if (error != EINVAL) {
+ VLOG_WARN("%s: %s flow probe failed (%s)",
+ dpif_name(dpif), name, ovs_strerror(error));
+ }
+ return false;
+ }
+
+ ofpbuf_use_stack(&reply, &stub, sizeof stub);
+ error = dpif_flow_get(dpif, key->data, key->size, ufid,
+ PMD_ID_NULL, &reply, &flow);
+ if (!error
+ && (!ufid || (flow.ufid_present
+ && ovs_u128_equals(ufid, &flow.ufid)))) {
+ enable_feature = true;
+ }
+
+ error = dpif_flow_del(dpif, key->data, key->size, ufid,
+ PMD_ID_NULL, NULL);
+ if (error) {
+ VLOG_WARN("%s: failed to delete %s feature probe flow",
+ dpif_name(dpif), name);
+ }
+
+ return enable_feature;
+}
+