net/ipfwd: fix devif_forward after IOB offload.

Problem:
- `iob_copyout` to `d_buf` doesn't set `io_len` of the IOB, so `devif_poll` failed to copy the data into `buf` by `iob_copyout`

Modification:
- Just Move the IOB in `devif_forward`.

Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>

include/nuttx/net/netdev.h

@@ -895,6 +895,20 @@ int netdev_lladdrsize(FAR struct net_driver_s *dev);
 int netdev_iob_prepare(FAR struct net_driver_s *dev, bool throttled,
                        unsigned int timeout);
 
+/****************************************************************************
+ * Name: netdev_iob_replace
+ *
+ * Description:
+ *   Replace buffer resources for a given NIC
+ *
+ * Assumptions:
+ *   The caller has locked the network and new iob is prepared with
+ *   l2 gruard size as offset.
+ *
+ ****************************************************************************/
+
+void netdev_iob_replace(FAR struct net_driver_s *dev, FAR struct iob_s *iob);
+
 /****************************************************************************
  * Name: netdev_iob_clear
  *

net/devif/devif_forward.c

@@ -60,24 +60,14 @@
 
 void devif_forward(FAR struct forward_s *fwd)
 {
-  unsigned int offset;
-  int ret;
-
   DEBUGASSERT(fwd != NULL && fwd->f_iob != NULL && fwd->f_dev != NULL);
-  offset = NET_LL_HDRLEN(fwd->f_dev);
 
-  /* Copy the IOB chain that contains the L3L3 headers and any data payload */
+  /* Move the IOB chain that contains the L3 header and any data payload */
 
-  DEBUGASSERT(offset + fwd->f_iob->io_pktlen <= NETDEV_PKTSIZE(fwd->f_dev));
+  netdev_iob_replace(fwd->f_dev, fwd->f_iob);
-  ret = iob_copyout(&fwd->f_dev->d_buf[offset], fwd->f_iob,
-                    fwd->f_iob->io_pktlen, 0);
-
-  DEBUGASSERT(ret == fwd->f_iob->io_pktlen);
 
   fwd->f_dev->d_sndlen = 0;
-  fwd->f_dev->d_len    = fwd->f_iob->io_pktlen;
+  fwd->f_iob = NULL;
-
-  UNUSED(ret);
 }
 
 #endif /* CONFIG_NET_IPFORWARD */

net/netdev/netdev_iob.c

@@ -84,6 +84,32 @@ int netdev_iob_prepare(FAR struct net_driver_s *dev, bool throttled,
   return OK;
 }
 
+/****************************************************************************
+ * Name: netdev_iob_replace
+ *
+ * Description:
+ *   Replace buffer resources for a given NIC
+ *
+ * Assumptions:
+ *   The caller has locked the network and new iob is prepared with
+ *   l2 gruard size as offset.
+ *
+ ****************************************************************************/
+
+void netdev_iob_replace(FAR struct net_driver_s *dev, FAR struct iob_s *iob)
+{
+  /* Release previous buffer */
+
+  netdev_iob_release(dev);
+
+  /* Set new buffer */
+
+  dev->d_iob = iob;
+  dev->d_buf = &dev->d_iob->io_data[CONFIG_NET_LL_GUARDSIZE -
+                                    NET_LL_HDRLEN(dev)];
+  dev->d_len = iob->io_pktlen;
+}
+
 /****************************************************************************
  * Name: netdev_iob_clear
  *