text: /****************************************************************************
   * net/udp/udp_input.c
   * Handling incoming UDP input
   *
   *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
   *   Author: Gregory Nutt <gnutt@nuttx.org>
   *
   * Adapted for NuttX from logic in uIP which also has a BSD-like license:
   *
   *   Original author Adam Dunkels <adam@dunkels.com>
   *   Copyright () 2001-2003, Adam Dunkels.
   *   All rights reserved.
   *
   * 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. The name of the author may not be used to endorse or promote
   *    products derived from this software without specific prior
   *    written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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>
  #if defined(CONFIG_NET) && defined(CONFIG_NET_UDP)
  
  #include <debug.h>
  
  #include <nuttx/net/netconfig.h>
  #include <nuttx/net/netdev.h>
  #include <nuttx/net/udp.h>
  #include <nuttx/net/netstats.h>
  
  #include "devif/devif.h"
  #include "utils/utils.h"
  #include "udp/udp.h"
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: udp_input
   *
   * Description:
   *   Handle incoming UDP input
   *
   * Parameters:
   *   dev   - The device driver structure containing the received UDP packet
   *   udp   - A pointer to the UDP header in the packet
   *   iplen - Length of the IP and UDP headers
   *
   * Return:
   *   OK  The packet has been processed  and can be deleted
   *   ERROR Hold the packet and try again later. There is a listening socket
   *         but no receive in place to catch the packet yet.
   *
   * Assumptions:
   *   Called from the interrupt level or with interrupts disabled.
   *
   ****************************************************************************/
  
  static int udp_input(FAR struct net_driver_s *dev, unsigned int iplen)
  {
    FAR struct udp_hdr_s *udp;
    FAR struct udp_conn_s *conn;
    unsigned int udpiplen;
    unsigned int hdrlen;
  #ifdef CONFIG_NET_UDP_CHECKSUMS
    uint16_t chksum;
  #endif
    int ret = OK;
  
    /* Update the count of UDP packets received */
  
  #ifdef CONFIG_NET_STATISTICS
    g_netstats.udp.recv++;
  #endif
  
    /* Get a pointer to the UDP header.  The UDP header lies just after the
     * the link layer header and the IP header.
     */
  
    udp = (FAR struct udp_hdr_s *)&dev->d_buf[iplen + NET_LL_HDRLEN(dev)];
  
    /* Get the size of the IP header and the UDP header */
  
    udpiplen = iplen + UDP_HDRLEN;
  
    /* Get the size of the link layer header, the IP header, and the UDP header */
  
    hdrlen = udpiplen + NET_LL_HDRLEN(dev);
  
    /* UDP processing is really just a hack. We don't do anything to the UDP/IP
     * headers, but let the UDP application do all the hard work. If the
     * application sets d_sndlen, it has a packet to send.
     */
  
    dev->d_len    -= udpiplen;
    dev->d_appdata = &dev->d_buf[hdrlen];
  
  #ifdef CONFIG_NET_UDP_CHECKSUMS
    chksum = udp->udpchksum;
    if (chksum != 0)
      {
  #ifdef CONFIG_NET_IPv6
  #ifdef CONFIG_NET_IPv4
        if (IFF_IS_IPv6(dev->d_flags))
  #endif
          {
            chksum = ~udp_ipv6_chksum(dev);
          }
  #endif /* CONFIG_NET_IPv6 */
  
  #ifdef CONFIG_NET_IPv4
  #ifdef CONFIG_NET_IPv6
        else
  #endif
          {
            chksum = ~udp_ipv4_chksum(dev);
          }
  #endif /* CONFIG_NET_IPv6 */
       }
  
     if (chksum != 0)
       {
  #ifdef CONFIG_NET_STATISTICS
        g_netstats.udp.drop++;
        g_netstats.udp.chkerr++;
  #endif
        nwarn("WARNING: Bad UDP checksum\n");
        dev->d_len = 0;
      }
    else
  #endif
      {
        /* Demultiplex this UDP packet between the UDP "connections".
         *
         * REVISIT:  The logic here expects either a single receive socket or
         * none at all.  However, multiple sockets should be capable of
         * receiving a UDP datagram (multicast reception).  This could be
         * handled easily by something like:
         *
         *   for (conn = NULL; conn = udp_active(dev, udp); )
         *
         * If the callback logic that receives a packet responds with an
         * outgoing packet, then it will over-write the received buffer,
         * however.  recvfrom() will not do that, however.  We would have to
         * make that the rule: Recipients of a UDP packet must treat the
         * packet as read-only.
         */
  
        conn = udp_active(dev, udp);
        if (conn)
          {
            uint16_t flags;
  
            /* Set-up for the application callback */
  
            dev->d_appdata = &dev->d_buf[hdrlen];
            dev->d_sndlen  = 0;
  
            /* Perform the application callback */
  
            flags = udp_callback(dev, conn, UDP_NEWDATA);
  
            /* If the operation was successful, the UDP_NEWDATA flag is removed
             * and thus the packet can be deleted (OK will be returned).
             */
  
            if ((flags & UDP_NEWDATA) != 0)
              {
                /* No.. the packet was not processed now.  Return ERROR so
                 * that the driver may retry again later.
                 */
  
                ret = ERROR;
              }
  
            /* If the application has data to send, setup the UDP/IP header */
  
            if (dev->d_sndlen > 0)
              {
                udp_send(dev, conn);
              }
          }
        else
          {
            nwarn("WARNING: No listener on UDP port\n");
            dev->d_len = 0;
          }
      }
  
    return ret;
  }
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: udp_ipv4_input
   *
   * Description:
   *   Handle incoming UDP input in an IPv4 packet
   *
   * Parameters:
   *   dev - The device driver structure containing the received UDP packet
   *
   * Return:
   *   OK  The packet has been processed  and can be deleted
   *   ERROR Hold the packet and try again later. There is a listening socket
   *         but no receive in place to catch the packet yet.
   *
   * Assumptions:
   *   Called from network stack logic with the network stack locked
   *
   ****************************************************************************/
  
  #ifdef CONFIG_NET_IPv4
  int udp_ipv4_input(FAR struct net_driver_s *dev)
  {
    /* Configure to receive an UDP IPv4 packet */
  
    udp_ipv4_select(dev);
  
    /* Then process in the UDP IPv4 input */
  
    return udp_input(dev, IPv4_HDRLEN);
  }
  #endif
  
  /****************************************************************************
   * Name: udp_ipv6_input
   *
   * Description:
   *   Handle incoming UDP input in an IPv6 packet
   *
   * Parameters:
   *   dev - The device driver structure containing the received UDP packet
   *
   * Return:
   *   OK  The packet has been processed  and can be deleted
   *   ERROR Hold the packet and try again later. There is a listening socket
   *         but no receive in place to catch the packet yet.
   *
   * Assumptions:
   *   Called from network stack logic with the network stack locked
   *
   ****************************************************************************/
  
  #ifdef CONFIG_NET_IPv6
  int udp_ipv6_input(FAR struct net_driver_s *dev)
  {
    /* Configure to receive an UDP IPv6 packet */
  
    udp_ipv6_select(dev);
  
    /* Then process in the UDP IPv6 input */
  
    return udp_input(dev, IPv6_HDRLEN);
  }
  #endif
  
  #endif /* CONFIG_NET && CONFIG_NET_UDP */
  