--- openflow-2011-10-12-6.h	2015-07-23 09:54:16.744479346 -0700
+++ openflow-2011-10-14.h	2015-07-23 09:54:16.748479346 -0700
@@ -372,9 +372,11 @@
     uint16_t type;             /* One of OFPMT_* */
     uint16_t length;           /* Length of ofp_match (excluding padding) */
     /* Followed by:
-     *   - Exactly (match_len - 4) (possibly 0) bytes containing OXM TLVs, then
-     *   - Exactly (match_len + 7)/8*8 - match_len (between 0 and 7) bytes of
+     *   - Exactly (length - 4) (possibly 0) bytes containing OXM TLVs, then
+     *   - Exactly ((length + 7)/8*8 - length) (between 0 and 7) bytes of
      *     all-zero bytes
+     * In summary, ofp_match is padded as needed, to make its overall size
+     * a multiple of 8, to preserve alignement in structures using it.
      */
     uint8_t oxm_fields[4];     /* OXMs start here - Make compiler happy */
 };