* The caller owns the data of 'upcall->packet' and may modify it. If
* packet's headroom is exhausted as it is manipulated, 'upcall->packet'
* will be reallocated. This requires the data of 'upcall->packet' to be
- * released with ofpbuf_uninit() before 'upcall' is destroyed.
+ * released with ofpbuf_uninit() before 'upcall' is destroyed. However,
+ * when an error is returned, the 'upcall->packet' may be uninitialized
+ * and should not be released.
*
* This function must not block. If no upcall is pending when it is
* called, it should return EAGAIN without blocking. */