Update comments.

net/devif/ipv4_input.c

@@ -309,10 +309,11 @@ nullreturn:
  * Description:
  *
  * Returned Value:
- *   OK    The packet was processed (or dropped) and can be discarded.
+ *   OK    - The packet was processed (or dropped) and can be discarded.
- *   ERROR There is a matching connection, but could not dispatch the packet
+ *   ERROR - Hold the packet and try again later.  There is a listening
- *         yet.  Currently useful for UDP when a packet arrives before a recv
+ *           socket but no receive in place to catch the packet yet.  The
- *         call is in place.
+ *           device's d_len will be set to zero in this case as there is
+ *           no outgoing data.
  *
  ****************************************************************************/
 

net/devif/ipv6_input.c

@@ -238,9 +238,10 @@ static bool check_destipaddr(FAR struct net_driver_s *dev,
  *           the IPv6 packet.
  * Returned Value:
  *   OK    - The packet was processed (or dropped) and can be discarded.
- *   ERROR - There is a matching connection, but could not dispatch the
+ *   ERROR - Hold the packet and try again later.  There is a listening
- *           packet yet.  Currently useful for UDP when a packet arrives
+ *           socket but no receive in place to catch the packet yet.  The
- *           before a recv call is in place.
+ *           device's d_len will be set to zero in this case as there is
+ *           no outgoing data.
  *
  *   If this function returns to the network driver with dev->d_len > 0,
  *   that is an indication to the driver that there is an outgoing response

net/pkt/pkt_input.c

@@ -74,9 +74,10 @@
  *   dev - The device driver structure containing the received packet
  *
  * Return:
- *   OK  The packet has been processed  and can be deleted
+ *   OK    The packet has been processed  and can be deleted
- *   ERROR Hold the packet and try again later. There is a listening socket
+ *   ERROR There is a matching connection, but could not dispatch the packet
- *         but no recv in place to catch the packet yet.
+ *         yet.  Currently useful for UDP when a packet arrives before a recv
+ *         call is in place.
  *
  * Assumptions:
  *   Called from the interrupt level or with interrupts disabled.
@@ -110,10 +111,14 @@ int pkt_input(struct net_driver_s *dev)
       if ((flags & PKT_NEWDATA) != 0)
         {
           /* No.. the packet was not processed now.  Return ERROR so
-           * that the driver may retry again later.
+           * that the driver may retry again later.  We still need to
+           * set d_len to zero so that the driver is aware that there
+           * is nothing to be sent.
            */
 
-          ret = ERROR;
+           nwarn("WARNING: Packet not processed\n");
+           //dev->d_len = 0; REVISIT
+           ret = ERROR;
         }
     }
   else

net/udp/udp_input.c

@@ -72,11 +72,11 @@
  *   iplen - Length of the IP and UDP headers
  *
  * Return:
- *   OK    The packet has been processed  and can be deleted
+ *   OK    - The packet has been processed  and can be deleted
- *   ERROR Hold the packet and try again later.  There is a listening socket
+ *   ERROR - Hold the packet and try again later.  There is a listening
- *         but no receive in place to catch the packet yet.  The device's
+ *           socket but no receive in place to catch the packet yet.  The
- *         d_len will be set to zero in this case as there is no outgoing
+ *           device's d_len will be set to zero in this case as there is
- *         data.
+ *           no outgoing data.
  *
  * Assumptions:
  *   Called from the interrupt level or with interrupts disabled.