net: Check error when pushing packet into stack

Make tcpip_input() to return 0 if there is an error when
processing the packet. Value != 0 indicates a successfull
packet processing and in this case the application will
free the packet.

Change-Id: I4aaeb5f0039cfbe25f7238a144964e31a8204148
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>

net/ip/contiki/ip/tcpip.c

@@ -540,14 +540,23 @@ eventhandler(process_event_t ev, process_data_t data, struct net_buf *buf)
   };
 }
 /*---------------------------------------------------------------------------*/
-void
+uint8_t
 tcpip_input(struct net_buf *buf)
 {
   process_post_synch(&tcpip_process, PACKET_INPUT, NULL, buf);
+  if (uip_len(buf) == 0) {
+    /* This indicates that there was a parsing/other error
+     * in packet.
+     */
+    return 0;
+  }
+
   uip_len(buf) = 0;
 #if NETSTACK_CONF_WITH_IPV6
   uip_ext_len(buf) = 0;
 #endif /*NETSTACK_CONF_WITH_IPV6*/
+
+  return 1;
 }
 /*---------------------------------------------------------------------------*/
 #if NETSTACK_CONF_WITH_IPV6

net/ip/contiki/ip/tcpip.h

@@ -333,9 +333,11 @@ CCIF extern process_event_t tcpip_event;
  *             deliver an incoming packet to the TCP/IP stack. The
  *             incoming packet must be present in the uip_buf buffer,
  *             and the length of the packet must be in the global
- *             uip_len variable.
+ *             uip_len variable. If 0 is returned, then there was
+ *             an error in the packet and it is discarded. The caller
+ *             can then release the net_buf
  */
-CCIF void tcpip_input(struct net_buf *buf);
+CCIF uint8_t tcpip_input(struct net_buf *buf);
 
 /**
  * \brief Output packet to layer 2

net/ip/contiki/ipv6/uip6.c

@@ -2325,11 +2325,6 @@ uip_process(struct net_buf *buf, uint8_t flag)
   return 1;
 
  drop:
-  /* If there is an error, then just return the buffer to pool */
-  if (uip_len(buf) == 0) {
-    net_buf_put(buf);
-  }
-
   uip_len(buf) = 0;
   uip_ext_len(buf) = 0;
   uip_ext_bitmap(buf) = 0;

net/ip/net_init.c

@@ -352,7 +352,9 @@ static void net_rx_fiber(void)
 		/* Check stack usage (no-op if not enabled) */
 		analyze_stacks(buf, &buf);
 
-		tcpip_input(buf);
+		if (!tcpip_input(buf)) {
+			net_buf_put(buf);
+		}
 	}
 }