1 files changed, 8 insertions, 4 deletions
diff --git a/lib/flow.c b/lib/flow.c
index aa1cc47ea..e54280a45 100644
--- a/lib/flow.c
+++ b/lib/flow.c
@@ -859,10 +859,14 @@ flow_format(struct ds *ds, const struct flow *flow)
 
     /* As this function is most often used for formatting a packet in a
      * packet-in message, skip formatting the packet context fields that are
-     * all-zeroes (Openflow spec encourages leaving out all-zeroes context
-     * fields from the packet-in messages).  We make an exception with the
-     * 'in_port' field, which we always format, as packets usually have an
-     * in_port, and 0 is a port just like any other port. */
+     * all-zeroes to make the print-out easier on the eyes.  This means that a
+     * missing context field implies a zero value for that field.  This is
+     * similar to OpenFlow encoding of these fields, as the specification
+     * states that all-zeroes context fields should not be encoded in the
+     * packet-in messages. */
+    if (!flow->in_port.ofp_port) {
+        WC_UNMASK_FIELD(wc, in_port);
+    }
     if (!flow->skb_priority) {
         WC_UNMASK_FIELD(wc, skb_priority);
     }