Networking: Allow receipt of empty UDP packets. From Max Neklyudov

ChangeLog

@@ -10797,10 +10797,11 @@
 	* arch/arm/src/samv7: Add the framework for an SPI slave drvier.  This
 	  driver has a lot of missing logic on initial commit (2015-08-09).
 	* arch/arm/src/samv7: Basic, no-DMA SPI slave driver is in place
-	  (2015-080=-10).
+	  (2015-08-10).
 	* fs/vfs/epoll.c and include/sys/epoll.h: Add a very simple epoll layer
 	  just around poll calls. To satisfy build app requirements.  From Anton
-	  D. Kachalov.
+	  D. Kachalov (2015-08-10).
 	* drivers/mtd/ramtron.c:  Update to include supportf for newer
-	  RAMTRON parts.  From David Sidrane.
+	  RAMTRON parts.  From David Sidrane (2015-08-10).
-
+	* Networking:  Allow receipt of empty UDP packets.  From Max Neklyudov
+	  (2015-08-11).

net/iob/iob_copyout.c

@@ -101,6 +101,12 @@ int iob_copyout(FAR uint8_t *dest, FAR const struct iob_s *iob,
     {
       offset -= iob->io_len;
       iob     = iob->io_flink;
+      if (iob == NULL)
+        {
+          /* We have no requested data in iob chain */
+
+          return 0;
+        }
     }
 
   /* Then loop until all of the I/O data is copied to the user buffer */

net/socket/recvfrom.c

@@ -101,7 +101,7 @@ struct recvfrom_s
   uint8_t                 *rf_buffer;    /* Pointer to receive buffer */
   FAR struct sockaddr     *rf_from;      /* Address of sender */
   FAR socklen_t           *rf_fromlen;   /* Number of bytes allocated for address of sender */
-  size_t                   rf_recvlen;   /* The received length */
+  ssize_t                  rf_recvlen;   /* The received length */
   int                      rf_result;    /* Success:OK, failure:negated errno */
 };
 #endif /* CONFIG_NET_UDP || CONFIG_NET_TCP */
@@ -404,8 +404,9 @@ static inline void recvfrom_udpreadahead(struct recvfrom_s *pstate)
    * buffer.
    */
 
-  if ((iob = iob_peek_queue(&conn->readahead)) != NULL &&
+  pstate->rf_recvlen = -1;
-          pstate->rf_buflen > 0)
+
+  if ((iob = iob_peek_queue(&conn->readahead)) != NULL)
     {
       FAR struct iob_s *tmp;
       uint8_t src_addr_size;
@@ -445,16 +446,23 @@ static inline void recvfrom_udpreadahead(struct recvfrom_s *pstate)
             }
         }
 
-      recvlen = iob_copyout(pstate->rf_buffer, iob, pstate->rf_buflen,
+      if (pstate->rf_buflen > 0)
-                            src_addr_size + sizeof(uint8_t));
+        {
+          recvlen = iob_copyout(pstate->rf_buffer, iob, pstate->rf_buflen,
+                                src_addr_size + sizeof(uint8_t));
 
-      nllvdbg("Received %d bytes (of %d)\n", recvlen, iob->io_pktlen);
+          nllvdbg("Received %d bytes (of %d)\n", recvlen, iob->io_pktlen);
 
-      /* Update the accumulated size of the data read */
+          /* Update the accumulated size of the data read */
 
-      pstate->rf_recvlen += recvlen;
+          pstate->rf_recvlen  = recvlen;
-      pstate->rf_buffer  += recvlen;
+          pstate->rf_buffer  += recvlen;
-      pstate->rf_buflen  -= recvlen;
+          pstate->rf_buflen  -= recvlen;
+        }
+      else
+        {
+          pstate->rf_recvlen = 0;
+        }
 
 out:
       /* Remove the I/O buffer chain from the head of the read-ahead
@@ -1482,7 +1490,7 @@ static ssize_t udp_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
        * something was received (already in 'ret'); EAGAIN if not.
        */
 
-      if (ret <= 0)
+      if (ret < 0)
         {
           /* Nothing was received */
 

net/udp/udp_callback.c

@@ -200,19 +200,23 @@ static uint16_t udp_datahandler(FAR struct net_driver_s *dev, FAR struct udp_con
       return 0;
     }
 
-  /* Copy the new appdata into the I/O buffer chain */
+  if (buflen > 0)
-
-  ret = iob_trycopyin(iob, buffer, buflen, src_addr_size + sizeof(uint8_t),
-                      true);
-  if (ret < 0)
     {
-      /* On a failure, iob_trycopyin return a negated error value but does
+      /* Copy the new appdata into the I/O buffer chain */
-       * not free any I/O buffers.
-       */
 
-      nlldbg("ERROR: Failed to add data to the I/O buffer chain: %d\n", ret);
+      ret = iob_trycopyin(iob, buffer, buflen,
-      (void)iob_free_chain(iob);
+                          src_addr_size + sizeof(uint8_t), true);
-      return 0;
+      if (ret < 0)
+        {
+          /* On a failure, iob_trycopyin return a negated error value but
+           * does not free any I/O buffers.
+           */
+
+          nlldbg("ERROR: Failed to add data to the I/O buffer chain: %d\n",
+                 ret);
+          (void)iob_free_chain(iob);
+          return 0;
+        }
     }
 
   /* Add the new I/O buffer chain to the tail of the read-ahead queue */
@@ -243,6 +247,11 @@ net_dataevent(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn,
               uint16_t flags)
 {
   uint16_t ret;
+#ifdef CONFIG_NET_UDP_READAHEAD
+  uint8_t *buffer = dev->d_appdata;
+  int      buflen = dev->d_len;
+  uint16_t recvlen;
+#endif
 
   ret = (flags & ~UDP_NEWDATA);
 
@@ -250,35 +259,26 @@ net_dataevent(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn,
    * can have zero-length with UDP_NEWDATA set just to cause an ACK).
    */
 
-  if (dev->d_len > 0)
+  nllvdbg("No receive on connection\n");
-    {
+
 #ifdef CONFIG_NET_UDP_READAHEAD
-      uint8_t *buffer = dev->d_appdata;
+  /* Save as the packet data as in the read-ahead buffer.  NOTE that
-      int      buflen = dev->d_len;
+   * partial packets will not be buffered.
-      uint16_t recvlen;
+   */
+
+  recvlen = udp_datahandler(dev, conn, buffer, buflen);
+  if (recvlen < buflen)
 #endif
-
+    {
-      nllvdbg("No receive on connection\n");
+      /* There is no handler to receive new data and there are no free
-
+       * read-ahead buffers to retain the data -- drop the packet.
-#ifdef CONFIG_NET_UDP_READAHEAD
-      /* Save as the packet data as in the read-ahead buffer.  NOTE that
-       * partial packets will not be buffered.
        */
 
-      recvlen = udp_datahandler(dev, conn, buffer, buflen);
+     nllvdbg("Dropped %d bytes\n", dev->d_len);
-      if (recvlen < buflen)
-#endif
-        {
-          /* There is no handler to receive new data and there are no free
-           * read-ahead buffers to retain the data -- drop the packet.
-           */
 
-         nllvdbg("Dropped %d bytes\n", dev->d_len);
+#ifdef CONFIG_NET_STATISTICS
-
+      g_netstats.udp.drop++;
- #ifdef CONFIG_NET_STATISTICS
-          g_netstats.udp.drop++;
 #endif
-        }
     }
 
   /* In any event, the new data has now been handled */