net/netdev: add devif_loopback_out() to check the loopback case where a packet is being sent to itself. Modify the net driver to call this function in this case. This function will simply re-inject the packet back into the network and the network driver will not put anything on the wire.

arch/arm/src/c5471/c5471_ethernet.c

@@ -1046,19 +1046,22 @@ static int c5471_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->c_dev))
-
-      c5471_transmit(priv);
-
-      /* Check if the ESM has let go of the RX descriptor giving us access
-       * rights to submit another Ethernet frame.
-       */
-
-      if ((EIM_TXDESC_OWN_HOST & getreg32(priv->c_rxcpudesc)) != 0)
         {
-          /* No, then return non-zero to terminate the poll */
+          /* Send the packet */
 
-          return 1;
+          c5471_transmit(priv);
+
+          /* Check if the ESM has let go of the RX descriptor giving us access
+           * rights to submit another Ethernet frame.
+           */
+
+          if ((EIM_TXDESC_OWN_HOST & getreg32(priv->c_rxcpudesc)) != 0)
+            {
+              /* No, then return non-zero to terminate the poll */
+
+              return 1;
+            }
         }
     }
 

arch/arm/src/imxrt/imxrt_enet.c

@@ -600,20 +600,23 @@ static int imxrt_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      imxrt_transmit(priv);
-      priv->dev.d_buf =
-        (uint8_t*)imxrt_swap32((uint32_t)priv->txdesc[priv->txhead].data);
-
-      /* Check if there is room in the device to hold another packet. If not,
-       * return a non-zero value to terminate the poll.
-       */
-
-      if (imxrt_txringfull(priv))
         {
-          return -EBUSY;
+          /* Send the packet */
-        }
+
+          imxrt_transmit(priv);
+          priv->dev.d_buf =
+            (uint8_t*)imxrt_swap32((uint32_t)priv->txdesc[priv->txhead].data);
+
+          /* Check if there is room in the device to hold another packet. If not,
+           * return a non-zero value to terminate the poll.
+           */
+
+          if (imxrt_txringfull(priv))
+            {
+              return -EBUSY;
+            }
+       }
     }
 
   /* If zero is returned, the polling will continue until all connections have

arch/arm/src/kinetis/kinetis_enet.c

@@ -571,19 +571,22 @@ static int kinetis_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      kinetis_transmit(priv);
-      priv->dev.d_buf =
-        (uint8_t*)kinesis_swap32((uint32_t)priv->txdesc[priv->txhead].data);
-
-      /* Check if there is room in the device to hold another packet. If not,
-       * return a non-zero value to terminate the poll.
-       */
-
-      if (kinetis_txringfull(priv))
         {
-          return -EBUSY;
+          /* Send the packet */
+
+          kinetis_transmit(priv);
+          priv->dev.d_buf =
+            (uint8_t*)kinesis_swap32((uint32_t)priv->txdesc[priv->txhead].data);
+
+          /* Check if there is room in the device to hold another packet. If not,
+           * return a non-zero value to terminate the poll.
+           */
+
+          if (kinetis_txringfull(priv))
+            {
+              return -EBUSY;
+            }
         }
     }
 

arch/arm/src/lpc17xx/lpc17_ethernet.c

@@ -716,17 +716,20 @@ static int lpc17_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send this packet.  In this context, we know that there is space for
+      if (!devif_loopback_out(&priv->lp_dev))
-       * at least one more packet in the descriptor list.
+        {
-       */
+          /* Send this packet.  In this context, we know that there is space for
+           * at least one more packet in the descriptor list.
+           */
 
-      lpc17_transmit(priv);
+          lpc17_transmit(priv);
 
-      /* Check if there is room in the device to hold another packet. If not,
+          /* Check if there is room in the device to hold another packet. If not,
-       * return any non-zero value to terminate the poll.
+           * return any non-zero value to terminate the poll.
-       */
+           */
 
-      ret = lpc17_txdesc(priv);
+          ret = lpc17_txdesc(priv);
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

arch/arm/src/lpc43xx/lpc43_ethernet.c

@@ -1165,44 +1165,47 @@ static int lpc43_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      lpc43_transmit(priv);
-      DEBUGASSERT(dev->d_len == 0 && dev->d_buf == NULL);
-
-      /* Check if the next TX descriptor is owned by the Ethernet DMA or CPU.  We
-       * cannot perform the TX poll if we are unable to accept another packet for
-       * transmission.
-       *
-       * In a race condition, ETH_TDES0_OWN may be cleared BUT still not available
-       * because lpc43_freeframe() has not yet run.  If lpc43_freeframe() has run,
-       * the buffer1 pointer (tdes2) will be nullified (and inflight should be <
-       * CONFIG_LPC43_ETH_NTXDESC).
-       */
-
-      if ((priv->txhead->tdes0 & ETH_TDES0_OWN) != 0 ||
-           priv->txhead->tdes2 != 0)
         {
-          /* We have to terminate the poll if we have no more descriptors
+          /* Send the packet */
-           * available for another transfer.
+
+          lpc43_transmit(priv);
+          DEBUGASSERT(dev->d_len == 0 && dev->d_buf == NULL);
+
+          /* Check if the next TX descriptor is owned by the Ethernet DMA or CPU.  We
+           * cannot perform the TX poll if we are unable to accept another packet for
+           * transmission.
+           *
+           * In a race condition, ETH_TDES0_OWN may be cleared BUT still not available
+           * because lpc43_freeframe() has not yet run.  If lpc43_freeframe() has run,
+           * the buffer1 pointer (tdes2) will be nullified (and inflight should be <
+           * CONFIG_LPC43_ETH_NTXDESC).
            */
 
-          return -EBUSY;
+          if ((priv->txhead->tdes0 & ETH_TDES0_OWN) != 0 ||
-        }
+               priv->txhead->tdes2 != 0)
+            {
+              /* We have to terminate the poll if we have no more descriptors
+               * available for another transfer.
+               */
 
-      /* We have the descriptor, we can continue the poll. Allocate a new
+              return -EBUSY;
-       * buffer for the poll.
+            }
-       */
 
-      dev->d_buf = lpc43_allocbuffer(priv);
+          /* We have the descriptor, we can continue the poll. Allocate a new
+           * buffer for the poll.
+           */
 
-      /* We can't continue the poll if we have no buffers */
+          dev->d_buf = lpc43_allocbuffer(priv);
 
-      if (dev->d_buf == NULL)
+          /* We can't continue the poll if we have no buffers */
-        {
-          /* Terminate the poll. */
 
-          return -ENOMEM;
+          if (dev->d_buf == NULL)
+            {
+              /* Terminate the poll. */
+
+              return -ENOMEM;
+            }
         }
     }
 

arch/arm/src/lpc54xx/lpc54_ethernet.c

@@ -790,49 +790,52 @@ static int lpc54_eth_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->eth_dev))
-
-      chan   = lpc54_eth_getring(priv);
-      txring = &priv->eth_txring[chan];
-
-      (txring->tr_buffers)[txring->tr_supply] =
-        (uint32_t *)priv->eth_dev.d_buf;
-
-      lpc54_eth_transmit(priv, chan);
-
-      txring0 = &priv->eth_txring[0];
-#ifdef CONFIG_LPC54_ETH_MULTIQUEUE
-      txring1 = &priv->eth_txring[1];
-
-      /* We cannot perform the Tx poll now if all of the Tx descriptors for
-       * both channels are in-use.
-       */
-
-      if (txring0->tr_inuse >= txring0->tr_ndesc ||
-          txring1->tr_inuse >= txring1->tr_ndesc)
-#else
-      /* We cannot continue the Tx poll now if all of the Tx descriptors for
-       * this channel 0 are in-use.
-       */
-
-      if (txring0->tr_inuse >= txring0->tr_ndesc)
-#endif
         {
-          /* Stop the poll.. no more Tx descriptors */
+          /* Send the packet */
 
-          return 1;
+          chan   = lpc54_eth_getring(priv);
-        }
+          txring = &priv->eth_txring[chan];
 
-      /* There is a free descriptor in the ring, allocate a new Tx buffer
+          (txring->tr_buffers)[txring->tr_supply] =
-       * to perform the poll.
+            (uint32_t *)priv->eth_dev.d_buf;
-       */
 
-       priv->eth_dev.d_buf = (uint8_t *)lpc54_pktbuf_alloc(priv);
+          lpc54_eth_transmit(priv, chan);
-       if (priv->eth_dev.d_buf == NULL)
-         {
-          /* Stop the poll.. no more packet buffers */
 
-          return 1;
+          txring0 = &priv->eth_txring[0];
+#ifdef CONFIG_LPC54_ETH_MULTIQUEUE
+          txring1 = &priv->eth_txring[1];
+
+          /* We cannot perform the Tx poll now if all of the Tx descriptors for
+           * both channels are in-use.
+           */
+
+          if (txring0->tr_inuse >= txring0->tr_ndesc ||
+              txring1->tr_inuse >= txring1->tr_ndesc)
+#else
+          /* We cannot continue the Tx poll now if all of the Tx descriptors for
+           * this channel 0 are in-use.
+           */
+
+          if (txring0->tr_inuse >= txring0->tr_ndesc)
+#endif
+            {
+              /* Stop the poll.. no more Tx descriptors */
+
+              return 1;
+            }
+
+          /* There is a free descriptor in the ring, allocate a new Tx buffer
+           * to perform the poll.
+           */
+
+           priv->eth_dev.d_buf = (uint8_t *)lpc54_pktbuf_alloc(priv);
+           if (priv->eth_dev.d_buf == NULL)
+             {
+              /* Stop the poll.. no more packet buffers */
+
+              return 1;
+            }
         }
     }
 

arch/arm/src/sam34/sam_emac.c

@@ -889,21 +889,24 @@ static int sam_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      sam_transmit(priv);
-
-      /* Check if there are any free TX descriptors.  We cannot perform
-       * the TX poll if we do not have buffering for another packet.
-       */
-
-      if (sam_txfree(priv) == 0)
         {
-          /* We have to terminate the poll if we have no more descriptors
+          /* Send the packet */
-           * available for another transfer.
+
+          sam_transmit(priv);
+
+          /* Check if there are any free TX descriptors.  We cannot perform
+           * the TX poll if we do not have buffering for another packet.
            */
 
-          return -EBUSY;
+          if (sam_txfree(priv) == 0)
+            {
+              /* We have to terminate the poll if we have no more descriptors
+               * available for another transfer.
+               */
+
+              return -EBUSY;
+            }
         }
     }
 

arch/arm/src/sama5/sam_emaca.c

@@ -898,21 +898,24 @@ static int sam_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      sam_transmit(priv);
-
-      /* Check if there are any free TX descriptors.  We cannot perform
-       * the TX poll if we do not have buffering for another packet.
-       */
-
-      if (sam_txfree(priv) == 0)
         {
-          /* We have to terminate the poll if we have no more descriptors
+          /* Send the packet */
-           * available for another transfer.
+
+          sam_transmit(priv);
+
+          /* Check if there are any free TX descriptors.  We cannot perform
+           * the TX poll if we do not have buffering for another packet.
            */
 
-          return -EBUSY;
+          if (sam_txfree(priv) == 0)
+            {
+              /* We have to terminate the poll if we have no more descriptors
+               * available for another transfer.
+               */
+
+              return -EBUSY;
+            }
         }
     }
 

arch/arm/src/sama5/sam_emacb.c

@@ -1233,21 +1233,24 @@ static int sam_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      sam_transmit(priv);
-
-      /* Check if there are any free TX descriptors.  We cannot perform
-       * the TX poll if we do not have buffering for another packet.
-       */
-
-      if (sam_txfree(priv) == 0)
         {
-          /* We have to terminate the poll if we have no more descriptors
+          /* Send the packet */
-           * available for another transfer.
+
+          sam_transmit(priv);
+
+          /* Check if there are any free TX descriptors.  We cannot perform
+           * the TX poll if we do not have buffering for another packet.
            */
 
-          return -EBUSY;
+          if (sam_txfree(priv) == 0)
+            {
+              /* We have to terminate the poll if we have no more descriptors
+               * available for another transfer.
+               */
+
+              return -EBUSY;
+            }
         }
     }
 

arch/arm/src/sama5/sam_gmac.c

@@ -830,21 +830,24 @@ static int sam_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      sam_transmit(priv);
-
-      /* Check if there are any free TX descriptors.  We cannot perform
-       * the TX poll if we do not have buffering for another packet.
-       */
-
-      if (sam_txfree(priv) == 0)
         {
-          /* We have to terminate the poll if we have no more descriptors
+          /* Send the packet */
-           * available for another transfer.
+
+          sam_transmit(priv);
+
+          /* Check if there are any free TX descriptors.  We cannot perform
+           * the TX poll if we do not have buffering for another packet.
            */
 
-          return -EBUSY;
+          if (sam_txfree(priv) == 0)
+            {
+              /* We have to terminate the poll if we have no more descriptors
+               * available for another transfer.
+               */
+
+              return -EBUSY;
+            }
         }
     }
 

arch/arm/src/samv7/sam_emac.c

@@ -1547,21 +1547,24 @@ static int sam_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      sam_transmit(priv, EMAC_QUEUE_0);
-
-      /* Check if there are any free TX descriptors.  We cannot perform
-       * the TX poll if we do not have buffering for another packet.
-       */
-
-      if (sam_txfree(priv, EMAC_QUEUE_0) == 0)
         {
-          /* We have to terminate the poll if we have no more descriptors
+          /* Send the packet */
-           * available for another transfer.
+
+          sam_transmit(priv, EMAC_QUEUE_0);
+
+          /* Check if there are any free TX descriptors.  We cannot perform
+           * the TX poll if we do not have buffering for another packet.
            */
 
-          return -EBUSY;
+          if (sam_txfree(priv, EMAC_QUEUE_0) == 0)
+            {
+              /* We have to terminate the poll if we have no more descriptors
+               * available for another transfer.
+               */
+
+              return -EBUSY;
+            }
         }
     }
 

arch/arm/src/stm32/stm32_eth.c

@@ -1271,44 +1271,47 @@ static int stm32_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      stm32_transmit(priv);
-      DEBUGASSERT(dev->d_len == 0 && dev->d_buf == NULL);
-
-      /* Check if the next TX descriptor is owned by the Ethernet DMA or CPU.  We
-       * cannot perform the TX poll if we are unable to accept another packet for
-       * transmission.
-       *
-       * In a race condition, ETH_TDES0_OWN may be cleared BUT still not available
-       * because stm32_freeframe() has not yet run.  If stm32_freeframe() has run,
-       * the buffer1 pointer (tdes2) will be nullified (and inflight should be <
-       * CONFIG_STM32_ETH_NTXDESC).
-       */
-
-      if ((priv->txhead->tdes0 & ETH_TDES0_OWN) != 0 ||
-           priv->txhead->tdes2 != 0)
         {
-          /* We have to terminate the poll if we have no more descriptors
+          /* Send the packet */
-           * available for another transfer.
+
+          stm32_transmit(priv);
+          DEBUGASSERT(dev->d_len == 0 && dev->d_buf == NULL);
+
+          /* Check if the next TX descriptor is owned by the Ethernet DMA or CPU.  We
+           * cannot perform the TX poll if we are unable to accept another packet for
+           * transmission.
+           *
+           * In a race condition, ETH_TDES0_OWN may be cleared BUT still not available
+           * because stm32_freeframe() has not yet run.  If stm32_freeframe() has run,
+           * the buffer1 pointer (tdes2) will be nullified (and inflight should be <
+           * CONFIG_STM32_ETH_NTXDESC).
            */
 
-          return -EBUSY;
+          if ((priv->txhead->tdes0 & ETH_TDES0_OWN) != 0 ||
-        }
+               priv->txhead->tdes2 != 0)
+            {
+              /* We have to terminate the poll if we have no more descriptors
+               * available for another transfer.
+               */
 
-      /* We have the descriptor, we can continue the poll. Allocate a new
+              return -EBUSY;
-       * buffer for the poll.
+            }
-       */
 
-      dev->d_buf = stm32_allocbuffer(priv);
+          /* We have the descriptor, we can continue the poll. Allocate a new
+           * buffer for the poll.
+           */
 
-      /* We can't continue the poll if we have no buffers */
+          dev->d_buf = stm32_allocbuffer(priv);
 
-      if (dev->d_buf == NULL)
+          /* We can't continue the poll if we have no buffers */
-        {
-          /* Terminate the poll. */
 
-          return -ENOMEM;
+          if (dev->d_buf == NULL)
+            {
+              /* Terminate the poll. */
+
+              return -ENOMEM;
+            }
         }
     }
 

arch/arm/src/stm32f7/stm32_ethernet.c

@@ -1305,44 +1305,47 @@ static int stm32_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      stm32_transmit(priv);
-      DEBUGASSERT(dev->d_len == 0 && dev->d_buf == NULL);
-
-      /* Check if the next TX descriptor is owned by the Ethernet DMA or CPU.  We
-       * cannot perform the TX poll if we are unable to accept another packet for
-       * transmission.
-       *
-       * In a race condition, ETH_TDES0_OWN may be cleared BUT still not available
-       * because stm32_freeframe() has not yet run.  If stm32_freeframe() has run,
-       * the buffer1 pointer (tdes2) will be nullified (and inflight should be <
-       * CONFIG_STM32F7_ETH_NTXDESC).
-       */
-
-      if ((priv->txhead->tdes0 & ETH_TDES0_OWN) != 0 ||
-           priv->txhead->tdes2 != 0)
         {
-          /* We have to terminate the poll if we have no more descriptors
+          /* Send the packet */
-           * available for another transfer.
+
+          stm32_transmit(priv);
+          DEBUGASSERT(dev->d_len == 0 && dev->d_buf == NULL);
+
+          /* Check if the next TX descriptor is owned by the Ethernet DMA or CPU.  We
+           * cannot perform the TX poll if we are unable to accept another packet for
+           * transmission.
+           *
+           * In a race condition, ETH_TDES0_OWN may be cleared BUT still not available
+           * because stm32_freeframe() has not yet run.  If stm32_freeframe() has run,
+           * the buffer1 pointer (tdes2) will be nullified (and inflight should be <
+           * CONFIG_STM32F7_ETH_NTXDESC).
            */
 
-          return -EBUSY;
+          if ((priv->txhead->tdes0 & ETH_TDES0_OWN) != 0 ||
-        }
+               priv->txhead->tdes2 != 0)
+            {
+              /* We have to terminate the poll if we have no more descriptors
+               * available for another transfer.
+               */
 
-      /* We have the descriptor, we can continue the poll. Allocate a new
+              return -EBUSY;
-       * buffer for the poll.
+            }
-       */
 
-      dev->d_buf = stm32_allocbuffer(priv);
+          /* We have the descriptor, we can continue the poll. Allocate a new
+           * buffer for the poll.
+           */
 
-      /* We can't continue the poll if we have no buffers */
+          dev->d_buf = stm32_allocbuffer(priv);
 
-      if (dev->d_buf == NULL)
+          /* We can't continue the poll if we have no buffers */
-        {
-          /* Terminate the poll. */
 
-          return -ENOMEM;
+          if (dev->d_buf == NULL)
+            {
+              /* Terminate the poll. */
+
+              return -ENOMEM;
+            }
         }
     }
 

arch/arm/src/tiva/lm3s_ethernet.c

@@ -644,11 +644,14 @@ static int tiva_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet.  tiva_transmit() will return zero if the
+      if (!devif_loopback_out(&priv->ld_dev))
-       * packet was successfully handled.
+        {
-       */
+          /* Send the packet.  tiva_transmit() will return zero if the
+           * packet was successfully handled.
+           */
 
-      ret = tiva_transmit(priv);
+          ret = tiva_transmit(priv);
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

arch/arm/src/tiva/tm4c_ethernet.c

@@ -1273,44 +1273,47 @@ static int tiva_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
-
-      tiva_transmit(priv);
-      DEBUGASSERT(dev->d_len == 0 && dev->d_buf == NULL);
-
-      /* Check if the next TX descriptor is owned by the Ethernet DMA or CPU.  We
-       * cannot perform the TX poll if we are unable to accept another packet for
-       * transmission.
-       *
-       * In a race condition, EMAC_TDES0_OWN may be cleared BUT still not available
-       * because tiva_freeframe() has not yet run.  If tiva_freeframe() has run,
-       * the buffer1 pointer (tdes2) will be nullified (and inflight should be <
-       * CONFIG_TIVA_EMAC_NTXDESC).
-       */
-
-      if ((priv->txhead->tdes0 & EMAC_TDES0_OWN) != 0 ||
-           priv->txhead->tdes2 != 0)
         {
-          /* We have to terminate the poll if we have no more descriptors
+          /* Send the packet */
-           * available for another transfer.
+
+          tiva_transmit(priv);
+          DEBUGASSERT(dev->d_len == 0 && dev->d_buf == NULL);
+
+          /* Check if the next TX descriptor is owned by the Ethernet DMA or CPU.  We
+           * cannot perform the TX poll if we are unable to accept another packet for
+           * transmission.
+           *
+           * In a race condition, EMAC_TDES0_OWN may be cleared BUT still not available
+           * because tiva_freeframe() has not yet run.  If tiva_freeframe() has run,
+           * the buffer1 pointer (tdes2) will be nullified (and inflight should be <
+           * CONFIG_TIVA_EMAC_NTXDESC).
            */
 
-          return -EBUSY;
+          if ((priv->txhead->tdes0 & EMAC_TDES0_OWN) != 0 ||
-        }
+               priv->txhead->tdes2 != 0)
+            {
+              /* We have to terminate the poll if we have no more descriptors
+               * available for another transfer.
+               */
 
-      /* We have the descriptor, we can continue the poll. Allocate a new
+              return -EBUSY;
-       * buffer for the poll.
+            }
-       */
 
-      dev->d_buf = tiva_allocbuffer(priv);
+          /* We have the descriptor, we can continue the poll. Allocate a new
+           * buffer for the poll.
+           */
 
-      /* We can't continue the poll if we have no buffers */
+          dev->d_buf = tiva_allocbuffer(priv);
 
-      if (dev->d_buf == NULL)
+          /* We can't continue the poll if we have no buffers */
-        {
-          /* Terminate the poll. */
 
-          return -ENOMEM;
+          if (dev->d_buf == NULL)
+            {
+              /* Terminate the poll. */
+
+              return -ENOMEM;
+            }
         }
     }
 

arch/hc/src/m9s12/m9s12_ethernet.c

@@ -244,13 +244,16 @@ static int emac_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->d_dev))
+        {
+          /* Send the packet */
 
-      emac_transmit(priv);
+          emac_transmit(priv);
 
-      /* Check if there is room in the device to hold another packet. If not,
+          /* Check if there is room in the device to hold another packet. If not,
-       * return a non-zero value to terminate the poll.
+           * return a non-zero value to terminate the poll.
-       */
+           */
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

arch/mips/src/pic32mx/pic32mx-ethernet.c

@@ -1149,31 +1149,34 @@ static int pic32mx_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send this packet.  In this context, we know that there is space for
+      if (!devif_loopback_out(&priv->pd_dev))
-       * at least one more packet in the descriptor list.
-       */
-
-      pic32mx_transmit(priv);
-
-      /* Check if the next TX descriptor is available. If not, return a
-       * non-zero value to terminate the poll.
-       */
-
-      if (pic32mx_txdesc(priv) == NULL)
         {
-          /* There are no more TX descriptors/buffers available.. stop the poll */
+          /* Send this packet.  In this context, we know that there is space for
+           * at least one more packet in the descriptor list.
+           */
 
-          return -EAGAIN;
+          pic32mx_transmit(priv);
-        }
 
-      /* Get the next Tx buffer needed in order to continue the poll */
+          /* Check if the next TX descriptor is available. If not, return a
+           * non-zero value to terminate the poll.
+           */
 
-      priv->pd_dev.d_buf = pic32mx_allocbuffer(priv);
+          if (pic32mx_txdesc(priv) == NULL)
-      if (priv->pd_dev.d_buf == NULL)
+            {
-        {
+              /* There are no more TX descriptors/buffers available.. stop the poll */
-          /* We have no more buffers available for the nex Tx.. stop the poll */
 
-          return -ENOMEM;
+              return -EAGAIN;
+            }
+
+          /* Get the next Tx buffer needed in order to continue the poll */
+
+          priv->pd_dev.d_buf = pic32mx_allocbuffer(priv);
+          if (priv->pd_dev.d_buf == NULL)
+            {
+              /* We have no more buffers available for the nex Tx.. stop the poll */
+
+              return -ENOMEM;
+            }
         }
     }
 

arch/mips/src/pic32mz/pic32mz-ethernet.c

@@ -1176,31 +1176,34 @@ static int pic32mz_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send this packet.  In this context, we know that there is space for
+      if (!devif_loopback_out(&priv->pd_dev))
-       * at least one more packet in the descriptor list.
-       */
-
-      pic32mz_transmit(priv);
-
-      /* Check if the next TX descriptor is available. If not, return a
-       * non-zero value to terminate the poll.
-       */
-
-      if (pic32mz_txdesc(priv) == NULL)
         {
-          /* There are no more TX descriptors/buffers available.. stop the poll */
+          /* Send this packet.  In this context, we know that there is space for
+           * at least one more packet in the descriptor list.
+           */
 
-          return -EAGAIN;
+          pic32mz_transmit(priv);
-        }
 
-      /* Get the next Tx buffer needed in order to continue the poll */
+          /* Check if the next TX descriptor is available. If not, return a
+           * non-zero value to terminate the poll.
+           */
 
-      priv->pd_dev.d_buf = pic32mz_allocbuffer(priv);
+          if (pic32mz_txdesc(priv) == NULL)
-      if (priv->pd_dev.d_buf == NULL)
+            {
-        {
+              /* There are no more TX descriptors/buffers available.. stop the poll */
-          /* We have no more buffers available for the nex Tx.. stop the poll */
 
-          return -ENOMEM;
+              return -EAGAIN;
+            }
+
+          /* Get the next Tx buffer needed in order to continue the poll */
+
+          priv->pd_dev.d_buf = pic32mz_allocbuffer(priv);
+          if (priv->pd_dev.d_buf == NULL)
+            {
+              /* We have no more buffers available for the nex Tx.. stop the poll */
+
+              return -ENOMEM;
+            }
         }
     }
 

arch/misoc/src/common/misoc_net.c

@@ -334,13 +334,16 @@ static int misoc_net_txpoll(FAR struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->misoc_net_dev))
+        {
+          /* Send the packet */
 
-      misoc_net_transmit(priv);
+          misoc_net_transmit(priv);
 
-      /* Check if there is room in the device to hold another packet. If not,
+          /* Check if there is room in the device to hold another packet. If not,
-       * return a non-zero value to terminate the poll.
+           * return a non-zero value to terminate the poll.
-       */
+           */
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

arch/sim/src/up_netdriver.c

@@ -151,9 +151,12 @@ static int sim_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&g_sim_dev))
+        {
+          /* Send the packet */
 
-      netdev_send(g_sim_dev.d_buf, g_sim_dev.d_len);
+          netdev_send(g_sim_dev.d_buf, g_sim_dev.d_len);
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

arch/z80/src/ez80/ez80_emac.c

@@ -1147,11 +1147,14 @@ static int ez80emac_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet.  ez80emac_transmit() will return zero if the
+      if (!devif_loopback_out(&priv->dev))
-       * packet was successfully handled.
+        {
-       */
+          /* Send the packet.  ez80emac_transmit() will return zero if the
+           * packet was successfully handled.
+           */
 
-      ret = ez80emac_transmit(priv);
+          ret = ez80emac_transmit(priv);
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

drivers/net/dm90x0.c

@@ -819,19 +819,22 @@ static int dm9x_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dm_dev))
-
-      dm9x_transmit(priv);
-
-      /* Check if there is room in the DM90x0 to hold another packet.  In 100M mode,
-       * that can be 2 packets, otherwise it is a single packet.
-       */
-
-      if (priv->dm_ntxpending > 1 || !priv->dm_b100M)
         {
-          /* Returning a non-zero value will terminate the poll operation */
+          /* Send the packet */
 
-          return 1;
+          dm9x_transmit(priv);
+
+          /* Check if there is room in the DM90x0 to hold another packet.  In 100M mode,
+           * that can be 2 packets, otherwise it is a single packet.
+           */
+
+          if (priv->dm_ntxpending > 1 || !priv->dm_b100M)
+            {
+              /* Returning a non-zero value will terminate the poll operation */
+
+              return 1;
+            }
         }
     }
 

drivers/net/enc28j60.c

@@ -1213,13 +1213,16 @@ static int enc_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
+        {
+          /* Send the packet */
 
-      enc_transmit(priv);
+          enc_transmit(priv);
 
-      /* Stop the poll now because we can queue only one packet */
+          /* Stop the poll now because we can queue only one packet */
 
-      return -EBUSY;
+          return -EBUSY;
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

drivers/net/encx24j600.c

@@ -1194,9 +1194,12 @@ static int enc_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
+        {
+          /* Send the packet */
 
-      ret = enc_txenqueue(priv);
+          ret = enc_txenqueue(priv);
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

drivers/net/ftmac100.c

@@ -388,13 +388,16 @@ static int ftmac100_txpoll(struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->ft_dev))
+        {
+          /* Send the packet */
 
-      ftmac100_transmit(priv);
+          ftmac100_transmit(priv);
 
-      /* Check if there is room in the device to hold another packet. If not,
+          /* Check if there is room in the device to hold another packet. If not,
-       * return a non-zero value to terminate the poll.
+           * return a non-zero value to terminate the poll.
-       */
+           */
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

drivers/net/skeleton.c

@@ -299,13 +299,21 @@ static int skel_txpoll(FAR struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      /* Check if the network is sending this packet to the IP address of
-
+       * this device.  If so, just loop the packet back into the network but
-      skel_transmit(priv);
+       * don't attmpt to put it on the wire.
-
-      /* Check if there is room in the device to hold another packet. If not,
-       * return a non-zero value to terminate the poll.
        */
+
+      if (!devif_loopback_out(&priv->sk_dev))
+        {
+          /* Send the packet */
+
+          skel_transmit(priv);
+
+          /* Check if there is room in the device to hold another packet. If not,
+           * return a non-zero value to terminate the poll.
+           */
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

drivers/net/slip.c

@@ -405,7 +405,10 @@ static int slip_txpoll(FAR struct net_driver_s *dev)
 
   if (priv->dev.d_len > 0)
     {
-      slip_transmit(priv);
+      if (!devif_loopback_out(&priv->dev))
+        {
+          slip_transmit(priv);
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

drivers/usbdev/cdcecm.c

@@ -400,15 +400,18 @@ static int cdcecm_txpoll(FAR struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->dev))
+        {
+          /* Send the packet */
 
-      cdcecm_transmit(priv);
+          cdcecm_transmit(priv);
 
-      /* Check if there is room in the device to hold another packet. If
+          /* Check if there is room in the device to hold another packet. If
-       * not, return a non-zero value to terminate the poll.
+           * not, return a non-zero value to terminate the poll.
-       */
+           */
 
-      return 1;
+          return 1;
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections

drivers/usbdev/rndis.c

@@ -994,8 +994,10 @@ static int rndis_txpoll(FAR struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      ret = rndis_transmit(priv);
+      if (!devif_loopback_out(&priv->netdev))
-
+        {
+          ret = rndis_transmit(priv);
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

drivers/wireless/ieee80211/bcmf_netdev.c

@@ -473,16 +473,19 @@ static int bcmf_txpoll(FAR struct net_driver_s *dev)
         }
 #endif /* CONFIG_NET_IPv6 */
 
-      /* Send the packet */
+      if (!devif_loopback_out(&priv->bc_dev))
+        {
+          /* Send the packet */
 
-      bcmf_transmit(priv, priv->cur_tx_frame);
+          bcmf_transmit(priv, priv->cur_tx_frame);
 
-      /* TODO: Check if there is room in the device to hold another packet.
+          /* TODO: Check if there is room in the device to hold another packet.
-       * If not, return a non-zero value to terminate the poll.
+           * If not, return a non-zero value to terminate the poll.
-       */
+           */
 
-      priv->cur_tx_frame = NULL;
+          priv->cur_tx_frame = NULL;
-      return 1;
+          return 1;
+        }
     }
 
   /* If zero is returned, the polling will continue until all connections have

include/nuttx/net/netdev.h

@@ -568,6 +568,23 @@ int devif_timer(FAR struct net_driver_s *dev, devif_poll_callback_t callback);
 void neighbor_out(FAR struct net_driver_s *dev);
 #endif /* CONFIG_NET_IPv6 */
 
+/****************************************************************************
+ * Name: devif_loopback_out
+ *
+ * Description:
+ *   This function should be called before sending out a packet. The function
+ *   checks the destination address of the packet to see whether the target of
+ *   packet is ourself and then consume the packet directly by calling input
+ *   process functions.
+ *
+ * Returned Value:
+ *   Zero is returned if the packet don't loop back to ourself, otherwise
+ *   a no zero value is returned.
+ *
+ ****************************************************************************/
+
+int devif_loopback_out(FAR struct net_driver_s *dev);
+
 /****************************************************************************
  * Carrier detection
  *

net/devif/Make.defs

@@ -36,6 +36,7 @@
 # Network device interface source files
 
 NET_CSRCS += devif_initialize.c devif_send.c devif_poll.c devif_callback.c
+NET_CSRCS += devif_loopbackout.c
 
 # Device driver IP packet receipt interfaces
 

net/devif/devif_loopbackout.c

@@ -0,0 +1,161 @@
+/****************************************************************************
+ * net/devif/devif_loopbackout.c
+ *
+ *   Copyright (C) 2018 Pinecone Inc. All rights reserved.
+ *   Author: Xiang Xiao <xiaoxiang@pinecone.net>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <debug.h>
+
+#include <nuttx/net/ip.h>
+#include <nuttx/net/pkt.h>
+#include <nuttx/net/netdev.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* This is a helper pointer for accessing the contents of the ip header */
+
+#define IPv4BUF ((FAR struct ipv4_hdr_s *)(dev->d_buf + dev->d_llhdrlen))
+#define IPv6BUF ((FAR struct ipv6_hdr_s *)(dev->d_buf + dev->d_llhdrlen))
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+static bool is_loopback(FAR struct net_driver_s *dev)
+{
+  if (dev->d_len > 0)
+    {
+#ifdef CONFIG_NET_IPv4
+      if ((IPv4BUF->vhl & IP_VERSION_MASK) == IPv4_VERSION &&
+           net_ipv4addr_hdrcmp(IPv4BUF->destipaddr, &dev->d_ipaddr))
+        {
+          return true;
+        }
+#endif
+
+#ifdef CONFIG_NET_IPv6
+      if ((IPv6BUF->vtc & IP_VERSION_MASK) == IPv6_VERSION &&
+          net_ipv6addr_hdrcmp(IPv6BUF->destipaddr, dev->d_ipv6addr))
+        {
+          return true;
+        }
+#endif
+    }
+
+  return false;
+}
+
+/****************************************************************************
+ * Name: devif_loopback_out
+ *
+ * Description:
+ *   This function should be called before sending out a packet. The function
+ *   checks the destination address of the packet to see whether the target of
+ *   packet is ourself and then consume the packet directly by calling input
+ *   process functions.
+ *
+ * Returned Value:
+ *   Zero is returned if the packet don't loop back to ourself, otherwise
+ *   a no zero value is returned.
+ *
+ ****************************************************************************/
+
+int devif_loopback_out(FAR struct net_driver_s *dev)
+{
+  if (!is_loopback(dev))
+    {
+      return 0;
+    }
+
+  /* Loop while if there is data "sent" to ourself.
+   * Sending, of course, just means relaying back through the network.
+   */
+
+  do
+    {
+       NETDEV_TXPACKETS(dev);
+       NETDEV_RXPACKETS(dev);
+
+#ifdef CONFIG_NET_PKT
+      /* When packet sockets are enabled, feed the frame into the packet tap */
+
+       pkt_input(dev);
+#endif
+
+      /* We only accept IP packets of the configured type */
+
+#ifdef CONFIG_NET_IPv4
+      if ((IPv4BUF->vhl & IP_VERSION_MASK) == IPv4_VERSION)
+        {
+          ninfo("IPv4 frame\n");
+
+          NETDEV_RXIPV4(dev);
+          ipv4_input(dev);
+        }
+      else
+#endif
+#ifdef CONFIG_NET_IPv6
+      if ((IPv6BUF->vtc & IP_VERSION_MASK) == IPv6_VERSION)
+        {
+          ninfo("Iv6 frame\n");
+
+          NETDEV_RXIPV6(dev);
+          ipv6_input(dev);
+        }
+      else
+#endif
+        {
+          NETDEV_RXDROPPED(dev);
+        }
+
+      NETDEV_TXDONE(dev);
+
+      /* Add the data link header length for the next loop */
+
+      if (dev->d_len != 0)
+        {
+          dev->d_len += dev->d_llhdrlen;
+        }
+    }
+  while (dev->d_len > 0);
+
+  return 1;
+}
+