+/* Returns true if 'mf' has a zero value in 'flow', false if it is nonzero.
+ *
+ * The caller is responsible for ensuring that 'flow' meets 'mf''s
+ * prerequisites. */
+bool
+mf_is_zero(const struct mf_field *mf, const struct flow *flow)
+{
+ union mf_value value;
+
+ mf_get_value(mf, flow, &value);
+ return is_all_zeros((const uint8_t *) &value, mf->n_bytes);
+}
+