Networking: Add UDP read-ahead support and support for poll/select on UDP sockets. From Macs N.

6 files changed, 689 insertions, 33 deletions

diff --git a/nuttx/net/socket/net_poll.c b/nuttx/net/socket/net_poll.c
index 37f990bd2..d2cacf13a 100644
--- a/nuttx/net/socket/net_poll.c
+++ b/nuttx/net/socket/net_poll.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * net/socket/net_poll.c
  *
- *   Copyright (C) 2008-2009, 2011-2014 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011-2015 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -56,6 +56,7 @@
 
 #include <devif/devif.h>
 #include "tcp/tcp.h"
+#include "udp/udp.h"
 #include "socket/socket.h"
 
 /****************************************************************************
@@ -91,7 +92,7 @@ struct net_poll_s
  ****************************************************************************/
 
 /****************************************************************************
- * Function: poll_interrupt
+ * Function: tcp_poll_interrupt
  *
  * Description:
  *   This function is called from the interrupt level to perform the actual
@@ -111,8 +112,8 @@ struct net_poll_s
  ****************************************************************************/
 
 #ifdef HAVE_NETPOLL
-static uint16_t poll_interrupt(FAR struct net_driver_s *dev, FAR void *conn,
-                               FAR void *pvpriv, uint16_t flags)
+static uint16_t tcp_poll_interrupt(FAR struct net_driver_s *dev, FAR void *conn,
+                                   FAR void *pvpriv, uint16_t flags)
 {
   FAR struct net_poll_s *info = (FAR struct net_poll_s *)pvpriv;
 
@@ -164,13 +165,76 @@ static uint16_t poll_interrupt(FAR struct net_driver_s *dev, FAR void *conn,
 #endif /* HAVE_NETPOLL */
 
 /****************************************************************************
- * Function: net_pollsetup
+ * Function: udp_poll_interrupt
+ *
+ * Description:
+ *   This function is called from the interrupt level to perform the actual
+ *   UDP receive operation via by the device interface layer.
+ *
+ * Parameters:
+ *   dev      The structure of the network driver that caused the interrupt
+ *   conn     The connection structure associated with the socket
+ *   flags    Set of events describing why the callback was invoked
+ *
+ * Returned Value:
+ *   None
+ *
+ * Assumptions:
+ *   Running at the interrupt level
+ *
+ ****************************************************************************/
+
+#ifdef HAVE_NETPOLL
+static uint16_t udp_poll_interrupt(FAR struct net_driver_s *dev, FAR void *conn,
+                                   FAR void *pvpriv, uint16_t flags)
+{
+  FAR struct net_poll_s *info = (FAR struct net_poll_s *)pvpriv;
+
+  nllvdbg("flags: %04x\n", flags);
+
+  DEBUGASSERT(!info || (info->psock && info->fds));
+
+  /* 'priv' might be null in some race conditions (?) */
+
+  if (info)
+    {
+      pollevent_t eventset = 0;
+
+      /* Check for data or connection availability events. */
+
+      if ((flags & (UDP_NEWDATA)) != 0)
+        {
+          eventset |= (POLLIN & info->fds->events);
+        }
+
+      /* A poll is a sign that we are free to send data. */
+
+      if ((flags & UDP_POLL) != 0)
+        {
+          eventset |= (POLLOUT & info->fds->events);
+        }
+
+      /* Awaken the caller of poll() is requested event occurred. */
+
+      if (eventset)
+        {
+          info->fds->revents |= eventset;
+          sem_post(info->fds->sem);
+        }
+    }
+
+  return flags;
+}
+#endif /* HAVE_NETPOLL */
+
+/****************************************************************************
+ * Function: tcp_pollsetup
  *
  * Description:
  *   Setup to monitor events on one TCP/IP socket
  *
  * Input Parameters:
- *   conn  - The TCP/IP connection of interest
+ *   psock - The TCP/IP socket of interest
  *   fds   - The structure describing the events to be monitored, OR NULL if
  *           this is a request to stop monitoring events.
  *
@@ -180,7 +244,7 @@ static uint16_t poll_interrupt(FAR struct net_driver_s *dev, FAR void *conn,
  ****************************************************************************/
 
 #ifdef HAVE_NETPOLL
-static inline int net_pollsetup(FAR struct socket *psock,
+static inline int tcp_pollsetup(FAR struct socket *psock,
                                 FAR struct pollfd *fds)
 {
   FAR struct tcp_conn_s *conn = psock->s_conn;
@@ -233,7 +297,7 @@ static inline int net_pollsetup(FAR struct socket *psock,
   cb->flags    = (TCP_NEWDATA | TCP_BACKLOG | TCP_POLL | TCP_CLOSE |
                   TCP_ABORT | TCP_TIMEDOUT);
   cb->priv     = (FAR void *)info;
-  cb->event    = poll_interrupt;
+  cb->event    = tcp_poll_interrupt;
 
   /* Save the reference in the poll info structure as fds private as well
    * for use durring poll teardown as well.
@@ -323,16 +387,169 @@ errout_with_lock:
   net_unlock(flags);
   return ret;
 }
+
+/****************************************************************************
+ * Function: udp_pollsetup
+ *
+ * Description:
+ *   Setup to monitor events on one UDP/IP socket
+ *
+ * Input Parameters:
+ *   psock - The UDP/IP socket of interest
+ *   fds   - The structure describing the events to be monitored, OR NULL if
+ *           this is a request to stop monitoring events.
+ *
+ * Returned Value:
+ *  0: Success; Negated errno on failure
+ *
+ ****************************************************************************/
+
+static inline int udp_pollsetup(FAR struct socket *psock,
+                                FAR struct pollfd *fds)
+{
+  FAR struct udp_conn_s *conn = psock->s_conn;
+  FAR struct net_poll_s *info;
+  FAR struct devif_callback_s *cb;
+  net_lock_t flags;
+  int ret;
+
+  /* Sanity check */
+
+#ifdef CONFIG_DEBUG
+  if (!conn || !fds)
+    {
+      return -EINVAL;
+    }
+#endif
+
+  /* Allocate a container to hold the poll information */
+
+  info = (FAR struct net_poll_s *)kmm_malloc(sizeof(struct net_poll_s));
+  if (!info)
+    {
+      return -ENOMEM;
+    }
+
+  /* Some of the  following must be atomic */
+
+  flags = net_lock();
+
+  /* Setup the UDP remote connection */
+
+  ret = udp_connect(conn, NULL);
+  if (ret)
+    {
+      goto errout_with_lock;
+    }
+
+  /* Allocate a TCP/IP callback structure */
+
+  cb = udp_callback_alloc(conn);
+  if (!cb)
+    {
+      ret = -EBUSY;
+      goto errout_with_lock;
+    }
+
+  /* Initialize the poll info container */
+
+  info->psock  = psock;
+  info->fds    = fds;
+  info->cb     = cb;
+
+  /* Initialize the callback structure.  Save the reference to the info
+   * structure as callback private data so that it will be available during
+   * callback processing.
+   */
+
+  cb->flags    = (0);
+  cb->priv     = (FAR void *)info;
+  cb->event    = udp_poll_interrupt;
+
+  if (info->fds->events & POLLOUT)
+    cb->flags |= UDP_POLL;
+  if (info->fds->events & POLLIN)
+    cb->flags |= UDP_NEWDATA;
+
+  /* Save the reference in the poll info structure as fds private as well
+   * for use durring poll teardown as well.
+   */
+
+  fds->priv    = (FAR void *)info;
+
+  /* Check for read data availability now */
+
+  if (!IOB_QEMPTY(&conn->readahead))
+    {
+      /* Normal data may be read without blocking. */
+
+      fds->revents |= (POLLRDNORM & fds->events);
+    }
+
+  /* Check if any requested events are already in effect */
+
+  if (fds->revents != 0)
+    {
+      /* Yes.. then signal the poll logic */
+      sem_post(fds->sem);
+    }
+
+  net_unlock(flags);
+  return OK;
+
+errout_with_lock:
+  kmm_free(info);
+  net_unlock(flags);
+  return ret;
+}
+
+/****************************************************************************
+ * Function: net_pollsetup
+ *
+ * Description:
+ *   Setup to monitor events on one socket
+ *
+ * Input Parameters:
+ *   psock - The socket of interest
+ *   fds   - The structure describing the events to be monitored, OR NULL if
+ *           this is a request to stop monitoring events.
+ *
+ * Returned Value:
+ *  0: Success; Negated errno on failure
+ *
+ ****************************************************************************/
+
+static inline int net_pollsetup(FAR struct socket *psock,
+                                FAR struct pollfd *fds)
+{
+#ifdef CONFIG_NET_TCP
+  if (psock->s_type == SOCK_STREAM)
+    {
+      return tcp_pollsetup(psock, fds);
+    }
+#endif
+
+#ifdef CONFIG_NET_UDP
+  if (psock->s_type != SOCK_STREAM)
+    {
+      return udp_pollsetup(psock, fds);
+    }
+#endif
+
+  return -ENOSYS;
+}
 #endif /* HAVE_NETPOLL */
 
 /****************************************************************************
- * Function: net_pollteardown
+ * Function: tcp_pollteardown
  *
  * Description:
  *   Teardown monitoring of events on an TCP/IP socket
  *
  * Input Parameters:
- *   conn  - The TCP/IP connection of interest
+ *   psock - The TCP/IP socket of interest
+ *   fds   - The structure describing the events to be monitored, OR NULL if
+ *           this is a request to stop monitoring events.
  *
  * Returned Value:
  *  0: Success; Negated errno on failure
@@ -340,7 +557,7 @@ errout_with_lock:
  ****************************************************************************/
 
 #ifdef HAVE_NETPOLL
-static inline int net_pollteardown(FAR struct socket *psock,
+static inline int tcp_pollteardown(FAR struct socket *psock,
                                    FAR struct pollfd *fds)
 {
   FAR struct tcp_conn_s *conn = psock->s_conn;
@@ -379,6 +596,98 @@ static inline int net_pollteardown(FAR struct socket *psock,
 
   return OK;
 }
+
+/****************************************************************************
+ * Function: udp_pollteardown
+ *
+ * Description:
+ *   Teardown monitoring of events on an UDP/IP socket
+ *
+ * Input Parameters:
+ *   psock - The TCP/IP socket of interest
+ *   fds   - The structure describing the events to be monitored, OR NULL if
+ *           this is a request to stop monitoring events.
+ *
+ * Returned Value:
+ *  0: Success; Negated errno on failure
+ *
+ ****************************************************************************/
+
+static inline int udp_pollteardown(FAR struct socket *psock,
+                                   FAR struct pollfd *fds)
+{
+  FAR struct udp_conn_s *conn = psock->s_conn;
+  FAR struct net_poll_s *info;
+  net_lock_t flags;
+
+  /* Sanity check */
+
+#ifdef CONFIG_DEBUG
+  if (!conn || !fds->priv)
+    {
+      return -EINVAL;
+    }
+#endif
+
+  /* Recover the socket descriptor poll state info from the poll structure */
+
+  info = (FAR struct net_poll_s *)fds->priv;
+  DEBUGASSERT(info && info->fds && info->cb);
+  if (info)
+    {
+      /* Release the callback */
+
+      flags = net_lock();
+      udp_callback_free(conn, info->cb);
+      net_unlock(flags);
+
+      /* Release the poll/select data slot */
+
+      info->fds->priv = NULL;
+
+      /* Then free the poll info container */
+
+      kmm_free(info);
+    }
+
+  return OK;
+}
+
+/****************************************************************************
+ * Function: net_pollteardown
+ *
+ * Description:
+ *   Teardown monitoring of events on an socket
+ *
+ * Input Parameters:
+ *   psock - The TCP/IP socket of interest
+ *   fds   - The structure describing the events to be monitored, OR NULL if
+ *           this is a request to stop monitoring events.
+ *
+ * Returned Value:
+ *  0: Success; Negated errno on failure
+ *
+ ****************************************************************************/
+
+static inline int net_pollteardown(FAR struct socket *psock,
+                                   FAR struct pollfd *fds)
+{
+#ifdef CONFIG_NET_TCP
+  if (psock->s_type == SOCK_STREAM)
+    {
+      return tcp_pollteardown(psock, fds);
+    }
+#endif
+
+#ifdef CONFIG_NET_UDP
+  if (psock->s_type != SOCK_STREAM)
+    {
+      return udp_pollteardown(psock, fds);
+    }
+#endif
+
+  return -ENOSYS;
+}
 #endif /* HAVE_NETPOLL */
 
 /****************************************************************************
@@ -408,15 +717,6 @@ int psock_poll(FAR struct socket *psock, FAR struct pollfd *fds, bool setup)
 {
   int ret;
 
-#ifdef CONFIG_NET_UDP
-  /* poll() not supported for UDP */
-
-  if (psock->s_type != SOCK_STREAM)
-    {
-      return -ENOSYS;
-    }
-#endif
-
   /* Check if we are setting up or tearing down the poll */
 
   if (setup)
diff --git a/nuttx/net/socket/recvfrom.c b/nuttx/net/socket/recvfrom.c
index e9fcd7a83..cdb018093 100644
--- a/nuttx/net/socket/recvfrom.c
+++ b/nuttx/net/socket/recvfrom.c
@@ -100,6 +100,7 @@ struct recvfrom_s
   size_t                   rf_buflen;    /* Length of receive buffer */
   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 */
   int                      rf_result;    /* Success:OK, failure:negated errno */
 };
@@ -310,7 +311,7 @@ static inline void recvfrom_newudpdata(FAR struct net_driver_s *dev,
 #endif /* CONFIG_NET_TCP */
 
 /****************************************************************************
- * Function: recvfrom_readahead
+ * Function: recvfrom_tcpreadahead
  *
  * Description:
  *   Copy the read data from the packet
@@ -328,7 +329,7 @@ static inline void recvfrom_newudpdata(FAR struct net_driver_s *dev,
  ****************************************************************************/
 
 #if defined(CONFIG_NET_TCP) && defined(CONFIG_NET_TCP_READAHEAD)
-static inline void recvfrom_readahead(struct recvfrom_s *pstate)
+static inline void recvfrom_tcpreadahead(struct recvfrom_s *pstate)
 {
   FAR struct tcp_conn_s *conn = (FAR struct tcp_conn_s *)pstate->rf_sock->s_conn;
   FAR struct iob_s *iob;
@@ -391,6 +392,83 @@ static inline void recvfrom_readahead(struct recvfrom_s *pstate)
 }
 #endif /* CONFIG_NET_UDP || CONFIG_NET_TCP */
 
+#if defined(CONFIG_NET_UDP) && defined(CONFIG_NET_UDP_READAHEAD)
+
+static inline void recvfrom_udpreadahead(struct recvfrom_s *pstate)
+{
+  FAR struct udp_conn_s *conn = (FAR struct udp_conn_s *)pstate->rf_sock->s_conn;
+  FAR struct iob_s *iob;
+  int recvlen;
+
+  /* Check there is any UDP datagram already buffered in a read-ahead
+   * buffer.
+   */
+
+  if ((iob = iob_peek_queue(&conn->readahead)) != NULL &&
+          pstate->rf_buflen > 0)
+    {
+      FAR struct iob_s *tmp;
+      uint8_t src_addr_size;
+
+      DEBUGASSERT(iob->io_pktlen > 0);
+
+      /* Transfer that buffered data from the I/O buffer chain into
+       * the user buffer.
+       */
+
+      recvlen = iob_copyout(&src_addr_size, iob, sizeof(uint8_t), 0);
+      if (recvlen != sizeof(uint8_t))
+        {
+          goto out;
+        }
+
+      if ( 0
+#ifdef CONFIG_NET_IPv6
+           || src_addr_size == 16
+#endif
+#ifdef CONFIG_NET_IPv4
+           || src_addr_size == 4
+#endif
+        )
+        {
+          if (pstate->rf_from)
+            {
+              socklen_t len = *pstate->rf_fromlen;
+              len = (socklen_t)src_addr_size > len ? len : (socklen_t)src_addr_size;
+
+              recvlen = iob_copyout(pstate->rf_from, iob, len, sizeof(uint8_t));
+              if (recvlen != len)
+                {
+                  goto out;
+                }
+            }
+        }
+
+      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);
+
+      /* Update the accumulated size of the data read */
+
+      pstate->rf_recvlen += recvlen;
+      pstate->rf_buffer  += recvlen;
+      pstate->rf_buflen  -= recvlen;
+
+out:
+      /* Remove the I/O buffer chain from the head of the read-ahead
+       * buffer queue.
+       */
+
+      tmp = iob_remove_queue(&conn->readahead);
+      DEBUGASSERT(tmp == iob);
+      UNUSED(tmp);
+
+      /* And free the I/O buffer chain */
+
+      (void)iob_free_chain(iob);
+    }
+}
+#endif
+
 /****************************************************************************
  * Function: recvfrom_timeout
  *
@@ -1015,6 +1093,7 @@ static uint16_t recvfrom_udpinterrupt(struct net_driver_s *dev, void *pvconn,
 #if defined(CONFIG_NET_UDP) || defined(CONFIG_NET_TCP)
 static void recvfrom_init(FAR struct socket *psock, FAR void *buf,
                           size_t len, FAR struct sockaddr *infrom,
+                          FAR socklen_t *fromlen,
                           FAR struct recvfrom_s *pstate)
 {
   /* Initialize the state structure. */
@@ -1024,6 +1103,7 @@ static void recvfrom_init(FAR struct socket *psock, FAR void *buf,
   pstate->rf_buflen    = len;
   pstate->rf_buffer    = buf;
   pstate->rf_from      = infrom;
+  pstate->rf_fromlen   = fromlen;
 
   /* Set up the start time for the timeout */
 
@@ -1184,7 +1264,7 @@ static inline void recvfrom_udp_rxnotify(FAR struct socket *psock,
 
 #ifdef CONFIG_NET_PKT
 static ssize_t pkt_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
-                            FAR struct sockaddr *from)
+                            FAR struct sockaddr *from, FAR socklen_t *fromlen)
 {
   FAR struct pkt_conn_s *conn = (FAR struct pkt_conn_s *)psock->s_conn;
   struct recvfrom_s state;
@@ -1199,7 +1279,7 @@ static ssize_t pkt_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
    */
 
   save = net_lock();
-  recvfrom_init(psock, buf, len, from, &state);
+  recvfrom_init(psock, buf, len, from, fromlen, &state);
 
   /* TODO recvfrom_init() expects from to be of type sockaddr_in, but
    * in our case is sockaddr_ll
@@ -1277,7 +1357,7 @@ errout_with_state:
 
 #ifdef CONFIG_NET_UDP
 static ssize_t udp_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
-                            FAR struct sockaddr *from)
+                            FAR struct sockaddr *from, FAR socklen_t *fromlen)
 {
   FAR struct udp_conn_s *conn = (FAR struct udp_conn_s *)psock->s_conn;
   struct recvfrom_s state;
@@ -1292,7 +1372,7 @@ static ssize_t udp_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
    */
 
   save = net_lock();
-  recvfrom_init(psock, buf, len, from, &state);
+  recvfrom_init(psock, buf, len, from, fromlen, &state);
 
   /* Setup the UDP remote connection */
 
@@ -1302,6 +1382,48 @@ static ssize_t udp_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
       goto errout_with_state;
     }
 
+#ifdef CONFIG_NET_UDP_READAHEAD
+  recvfrom_udpreadahead(&state);
+
+  /* The default return value is the number of bytes that we just copied
+   * into the user buffer.  We will return this if the socket has become
+   * disconnected or if the user request was completely satisfied with
+   * data from the readahead buffers.
+   */
+
+  ret = state.rf_recvlen;
+
+#else
+  /* Otherwise, the default return value of zero is used (only for the case
+   * where len == state.rf_buflen is zero).
+   */
+
+  ret = 0;
+#endif
+
+#ifdef CONFIG_NET_UDP_READAHEAD
+  if (_SS_ISNONBLOCK(psock->s_flags))
+    {
+      /* Return the number of bytes read from the read-ahead buffer if
+       * something was received (already in 'ret'); EAGAIN if not.
+       */
+
+      if (ret <= 0)
+        {
+          /* Nothing was received */
+
+          ret = -EAGAIN;
+        }
+    }
+
+  /* It is okay to block if we need to.  If there is space to receive anything
+   * more, then we will wait to receive the data.  Otherwise return the number
+   * of bytes read from the read-ahead buffer (already in 'ret').
+   */
+
+  else if (state.rf_recvlen == 0)
+#endif
+  {
   /* Set up the callback in the connection */
 
   state.rf_cb = udp_callback_alloc(conn);
@@ -1334,6 +1456,7 @@ static ssize_t udp_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
     {
       ret = -EBUSY;
     }
+  }
 
 errout_with_state:
   net_unlock(save);
@@ -1364,7 +1487,7 @@ errout_with_state:
 
 #ifdef CONFIG_NET_TCP
 static ssize_t tcp_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
-                            FAR struct sockaddr *from)
+                            FAR struct sockaddr *from, FAR socklen_t *fromlen)
 {
   struct recvfrom_s       state;
   net_lock_t              save;
@@ -1376,7 +1499,7 @@ static ssize_t tcp_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
    */
 
   save = net_lock();
-  recvfrom_init(psock, buf, len, from, &state);
+  recvfrom_init(psock, buf, len, from, fromlen, &state);
 
   /* Handle any any TCP data already buffered in a read-ahead buffer.  NOTE
    * that there may be read-ahead data to be retrieved even after the
@@ -1384,7 +1507,7 @@ static ssize_t tcp_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
    */
 
 #ifdef CONFIG_NET_TCP_READAHEAD
-  recvfrom_readahead(&state);
+  recvfrom_tcpreadahead(&state);
 
   /* The default return value is the number of bytes that we just copied
    * into the user buffer.  We will return this if the socket has become
@@ -1597,6 +1720,12 @@ ssize_t psock_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
     }
 #endif
 
+  if (from && !fromlen)
+    {
+      err = EINVAL;
+      goto errout;
+    }
+
   /* Verify that the sockfd corresponds to valid, allocated socket */
 
   if (!psock || psock->s_crefs <= 0)
@@ -1666,7 +1795,7 @@ ssize_t psock_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
 #ifdef CONFIG_NET_PKT
     case SOCK_RAW:
       {
-        ret = pkt_recvfrom(psock, buf, len, from);
+        ret = pkt_recvfrom(psock, buf, len, from, fromlen);
       }
       break;
 #endif /* CONFIG_NET_PKT */
@@ -1689,7 +1818,7 @@ ssize_t psock_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
         else
 #endif
           {
-            ret = tcp_recvfrom(psock, buf, len, from);
+            ret = tcp_recvfrom(psock, buf, len, from, fromlen);
           }
 #endif /* CONFIG_NET_TCP */
       }
@@ -1714,7 +1843,7 @@ ssize_t psock_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
         else
 #endif
           {
-            ret = udp_recvfrom(psock, buf, len, from);
+            ret = udp_recvfrom(psock, buf, len, from, fromlen);
           }
 #endif /* CONFIG_NET_UDP */
       }
diff --git a/nuttx/net/tcp/tcp_send_buffered.c b/nuttx/net/tcp/tcp_send_buffered.c
index ca8dddc4a..98621835d 100644
--- a/nuttx/net/tcp/tcp_send_buffered.c
+++ b/nuttx/net/tcp/tcp_send_buffered.c
@@ -307,7 +307,7 @@ static inline bool psock_send_addrchck(FAR struct tcp_conn_s *conn)
 }
 
 #else /* CONFIG_NET_ETHERNET */
-#  psock_send_addrchck(r) (true)
+#  define psock_send_addrchck(r) (true)
 #endif /* CONFIG_NET_ETHERNET */
 
 /****************************************************************************
diff --git a/nuttx/net/udp/Kconfig b/nuttx/net/udp/Kconfig
index 68a80bced..b387b402d 100644
--- a/nuttx/net/udp/Kconfig
+++ b/nuttx/net/udp/Kconfig
@@ -50,5 +50,10 @@ config NET_RXAVAIL
 		NOTE:  If this option is enabled, the driver must support the
 		rxavail() method in the net_driver_s structure.
 
+config NET_UDP_READAHEAD
+	bool "Enable UDP/IP read-ahead buffering"
+	default y
+	select NET_IOB
+
 endif # NET_UDP
 endmenu # UDP Networking
diff --git a/nuttx/net/udp/udp.h b/nuttx/net/udp/udp.h
index 305f28b37..2f193dea0 100644
--- a/nuttx/net/udp/udp.h
+++ b/nuttx/net/udp/udp.h
@@ -47,6 +47,10 @@
 
 #include <nuttx/net/ip.h>
 
+#ifdef CONFIG_NET_UDP_READAHEAD
+#  include <nuttx/net/iob.h>
+#endif
+
 #ifdef CONFIG_NET_UDP
 
 /****************************************************************************
@@ -77,6 +81,16 @@ struct udp_conn_s
   uint8_t  ttl;           /* Default time-to-live */
   uint8_t  crefs;         /* Reference counts on this instance */
 
+#ifdef CONFIG_NET_UDP_READAHEAD
+  /* Read-ahead buffering.
+   *
+   *   readahead - A singly linked list of type struct iob_qentry_s
+   *               where the UDP/IP read-ahead data is retained.
+   */
+
+  struct iob_queue_s readahead;   /* Read-ahead buffering */
+#endif
+
   /* Defines the list of UDP callbacks */
 
   FAR struct devif_callback_s *list;
diff --git a/nuttx/net/udp/udp_callback.c b/nuttx/net/udp/udp_callback.c
index a1553adb2..ab06e2522 100644
--- a/nuttx/net/udp/udp_callback.c
+++ b/nuttx/net/udp/udp_callback.c
@@ -48,9 +48,20 @@
 #include <nuttx/net/udp.h>
 
 #include "devif/devif.h"
+#include "iob/iob.h"
 #include "udp/udp.h"
 
 /****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define IPv4BUF    ((FAR struct ipv4_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+#define IPv6BUF    ((FAR struct ipv6_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev)])
+
+#define UDPIPv4BUF ((FAR struct udp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv4_HDRLEN])
+#define UDPIPv6BUF ((FAR struct udp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
+
+/****************************************************************************
  * Private Data
  ****************************************************************************/
 
@@ -59,6 +70,196 @@
  ****************************************************************************/
 
 /****************************************************************************
+ * Function: udp_datahandler
+ *
+ * Description:
+ *   Handle the receipt of UDP data by adding the newly received packet to
+ *   the UDP read-ahead buffer.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_NET_UDP_READAHEAD
+static uint16_t udp_datahandler(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn,
+                                FAR uint8_t *buffer, uint16_t buflen)
+{
+  FAR struct iob_s *iob;
+  int ret;
+#ifdef CONFIG_NET_IPv6
+  FAR struct sockaddr_in6 src_addr6;
+#endif
+#ifdef CONFIG_NET_IPv4
+  FAR struct sockaddr_in src_addr4;
+#endif
+  FAR void  *src_addr;
+  uint8_t src_addr_size;
+
+  /* Allocate on I/O buffer to start the chain (throttling as necessary).
+   * We will not wait for an I/O buffer to become available in this context.
+   */
+
+  iob = iob_tryalloc(true);
+  if (iob == NULL)
+    {
+      nlldbg("ERROR: Failed to create new I/O buffer chain\n");
+      return 0;
+    }
+
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+  if (IFF_IS_IPv6(dev->d_flags))
+#endif
+    {
+      FAR struct udp_hdr_s *udp   = UDPIPv6BUF;
+      FAR struct ipv6_hdr_s *ipv6 = IPv6BUF;
+
+      src_addr6.sin6_family = AF_INET6;
+      src_addr6.sin6_port   = udp->srcport;
+
+      net_ipv6addr_copy(src_addr6.sin6_addr.s6_addr, ipv6->srcipaddr);
+
+      src_addr_size = sizeof(src_addr6);
+      src_addr = &src_addr6;
+    }
+#endif /* CONFIG_NET_IPv6 */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+  else
+#endif
+    {
+      FAR struct udp_hdr_s *udp   = UDPIPv4BUF;
+      FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
+
+      src_addr4.sin_family = AF_INET;
+      src_addr4.sin_port   = udp->srcport;
+
+      net_ipv4addr_copy(src_addr4.sin_addr.s_addr,
+                            net_ip4addr_conv32(ipv4->srcipaddr));
+
+      src_addr_size = sizeof(src_addr4);
+      src_addr = &src_addr4;
+    }
+#endif /* CONFIG_NET_IPv4 */
+
+  /* Copy the src address info into the I/O buffer chain.  We will not wait
+   * for an I/O buffer to become available in this context.  It there is
+   * any failure to allocated, the entire I/O buffer chain will be discarded.
+   */
+
+  ret = iob_trycopyin(iob, (FAR const uint8_t*)&src_addr_size,
+                      sizeof(uint8_t), 0, true);
+  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;
+    }
+
+  ret = iob_trycopyin(iob, (FAR const uint8_t*)src_addr, src_addr_size,
+                      sizeof(uint8_t), true);
+  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;
+    }
+
+  /* Copy the new appdata into the I/O buffer chain */
+
+  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
+       * 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 */
+
+  ret = iob_tryadd_queue(iob, &conn->readahead);
+  if (ret < 0)
+    {
+      nlldbg("ERROR: Failed to queue the I/O buffer chain: %d\n", ret);
+      (void)iob_free_chain(iob);
+      return 0;
+    }
+
+  nllvdbg("Buffered %d bytes\n", buflen);
+  return buflen;
+}
+#endif /* CONFIG_NET_UDP_READAHEAD */
+
+/****************************************************************************
+ * Function: net_dataevent
+ *
+ * Description:
+ *   Handling the network UDP_NEWDATA event.
+ *
+ ****************************************************************************/
+
+static inline uint16_t
+net_dataevent(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn,
+              uint16_t flags)
+{
+  uint16_t ret;
+
+  ret = (flags & ~UDP_NEWDATA);
+
+  /* Is there new data?  With non-zero length?  (Certain connection events
+   * can have zero-length with UDP_NEWDATA set just to cause an ACK).
+   */
+
+  if (dev->d_len > 0)
+    {
+#ifdef CONFIG_NET_UDP_READAHEAD
+      uint8_t *buffer = dev->d_appdata;
+      int      buflen = dev->d_len;
+      uint16_t recvlen;
+#endif
+
+      nllvdbg("No receive on connection\n");
+
+#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);
+      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++;
+#endif
+        }
+    }
+
+  /* In any event, the new data has now been handled */
+
+  dev->d_len = 0;
+  return ret;
+}
+
+/****************************************************************************
  * Public Functions
  ****************************************************************************/
 
@@ -88,6 +289,13 @@ uint16_t udp_callback(FAR struct net_driver_s *dev,
       /* Perform the callback */
 
       flags = devif_callback_execute(dev, conn, flags, conn->list);
+
+      if ((flags & UDP_NEWDATA) != 0)
+        {
+          /* Data was not handled.. dispose of it appropriately */
+
+          flags = net_dataevent(dev, conn, flags);
+        }
     }
 
   return flags;