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 /**
  * @file
  * Ethernet Interface Skeleton
  *
  */
 
 /*
  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
  * 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.
  *
  * This file is part of the lwIP TCP/IP stack.
  * 
  * Author: Adam Dunkels <adam@sics.se>
  *
  */
 
 /*
  * This file is a skeleton for developing Ethernet network interface
  * drivers for lwIP. Add code to the low_level functions and do a
  * search-and-replace for the word "ethernetif" to replace it with
  * something that better describes your network interface.
  */
 
 #include "lwip/opt.h"
 
 #if 0 /* don't build, this is only a skeleton, see previous comment */
 
 #include "lwip/def.h"
 #include "lwip/mem.h"
 #include "lwip/pbuf.h"
 #include "lwip/sys.h"
 #include <lwip/stats.h>
 #include <lwip/snmp.h>
 #include "netif/etharp.h"
 #include "netif/ppp_oe.h"
 
 /* Define those to better describe your network interface. */
 #define IFNAME0 'e'
 #define IFNAME1 'n'
 
 /**
  * Helper struct to hold private data used to operate your ethernet interface.
  * Keeping the ethernet address of the MAC in this struct is not necessary
  * as it is already kept in the struct netif.
  * But this is only an example, anyway...
  */
 struct ethernetif {
   struct eth_addr *ethaddr;
   /* Add whatever per-interface state that is needed here. */
 };
 
 /* Forward declarations. */
 static void  ethernetif_input(struct netif *netif);
 
 /**
  * In this function, the hardware should be initialized.
  * Called from ethernetif_init().
  *
  * @param netif the already initialized lwip network interface structure
  *        for this ethernetif
  */
 static void
 low_level_init(struct netif *netif)
 {
   struct ethernetif *ethernetif = netif->state;
   
   /* set MAC hardware address length */
   netif->hwaddr_len = ETHARP_HWADDR_LEN;
 
   /* set MAC hardware address */
   netif->hwaddr[0] = ;
   ...
   netif->hwaddr[5] = ;
 
   /* maximum transfer unit */
   netif->mtu = 1500;
   
   /* device capabilities */
   /* don't set NETIF_FLAG_ETHARP if this device is not an ethernet one */
   netif->flags = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_LINK_UP;
  
   /* Do whatever else is needed to initialize interface. */  
 }
 
 /**
  * This function should do the actual transmission of the packet. The packet is
  * contained in the pbuf that is passed to the function. This pbuf
  * might be chained.
  *
  * @param netif the lwip network interface structure for this ethernetif
  * @param p the MAC packet to send (e.g. IP packet including MAC addresses and type)
  * @return ERR_OK if the packet could be sent
  *         an err_t value if the packet couldn't be sent
  *
  * @note Returning ERR_MEM here if a DMA queue of your MAC is full can lead to
  *       strange results. You might consider waiting for space in the DMA queue
  *       to become availale since the stack doesn't retry to send a packet
  *       dropped because of memory failure (except for the TCP timers).
  */
 
 static err_t
 low_level_output(struct netif *netif, struct pbuf *p)
 {
   struct ethernetif *ethernetif = netif->state;
   struct pbuf *q;
 
   initiate transfer();
   
 #if ETH_PAD_SIZE
   pbuf_header(p, -ETH_PAD_SIZE); /* drop the padding word */
 #endif
 
   for(q = p; q != NULL; q = q->next) {
     /* Send the data from the pbuf to the interface, one pbuf at a
        time. The size of the data in each pbuf is kept in the ->len
        variable. */
     send data from(q->payload, q->len);
   }
 
   signal that packet should be sent();
 
 #if ETH_PAD_SIZE
   pbuf_header(p, ETH_PAD_SIZE); /* reclaim the padding word */
 #endif
   
   LINK_STATS_INC(link.xmit);
 
   return ERR_OK;
 }
 
 /**
  * Should allocate a pbuf and transfer the bytes of the incoming
  * packet from the interface into the pbuf.
  *
  * @param netif the lwip network interface structure for this ethernetif
  * @return a pbuf filled with the received packet (including MAC header)
  *         NULL on memory error
  */
 static struct pbuf *
 low_level_input(struct netif *netif)
 {
   struct ethernetif *ethernetif = netif->state;
   struct pbuf *p, *q;
   u16_t len;
 
   /* Obtain the size of the packet and put it into the "len"
      variable. */
   len = ;
 
 #if ETH_PAD_SIZE
   len += ETH_PAD_SIZE; /* allow room for Ethernet padding */
 #endif
 
   /* We allocate a pbuf chain of pbufs from the pool. */
   p = pbuf_alloc(PBUF_RAW, len, PBUF_POOL);
   
   if (p != NULL) {
 
 #if ETH_PAD_SIZE
     pbuf_header(p, -ETH_PAD_SIZE); /* drop the padding word */
 #endif
 
     /* We iterate over the pbuf chain until we have read the entire
      * packet into the pbuf. */
     for(q = p; q != NULL; q = q->next) {
       /* Read enough bytes to fill this pbuf in the chain. The
        * available data in the pbuf is given by the q->len
        * variable.
        * This does not necessarily have to be a memcpy, you can also preallocate
        * pbufs for a DMA-enabled MAC and after receiving truncate it to the
        * actually received size. In this case, ensure the tot_len member of the
        * pbuf is the sum of the chained pbuf len members.
        */
       read data into(q->payload, q->len);
     }
     acknowledge that packet has been read();
 
 #if ETH_PAD_SIZE
     pbuf_header(p, ETH_PAD_SIZE); /* reclaim the padding word */
 #endif
 
     LINK_STATS_INC(link.recv);
   } else {
     drop packet();
     LINK_STATS_INC(link.memerr);
     LINK_STATS_INC(link.drop);
   }
 
   return p;  
 }
 
 /**
  * This function should be called when a packet is ready to be read
  * from the interface. It uses the function low_level_input() that
  * should handle the actual reception of bytes from the network
  * interface. Then the type of the received packet is determined and
  * the appropriate input function is called.
  *
  * @param netif the lwip network interface structure for this ethernetif
  */
 static void
 ethernetif_input(struct netif *netif)
 {
   struct ethernetif *ethernetif;
   struct eth_hdr *ethhdr;
   struct pbuf *p;
 
   ethernetif = netif->state;
 
   /* move received packet into a new pbuf */
   p = low_level_input(netif);
   /* no packet could be read, silently ignore this */
   if (p == NULL) return;
   /* points to packet payload, which starts with an Ethernet header */
   ethhdr = p->payload;
 
   switch (htons(ethhdr->type)) {
   /* IP or ARP packet? */
   case ETHTYPE_IP:
   case ETHTYPE_ARP:
 #if PPPOE_SUPPORT
   /* PPPoE packet? */
   case ETHTYPE_PPPOEDISC:
   case ETHTYPE_PPPOE:
 #endif /* PPPOE_SUPPORT */
     /* full packet send to tcpip_thread to process */
     if (netif->input(p, netif)!=ERR_OK)
      { LWIP_DEBUGF(NETIF_DEBUG, ("ethernetif_input: IP input error\n"));
        pbuf_free(p);
        p = NULL;
      }
     break;
 
   default:
     pbuf_free(p);
     p = NULL;
     break;
   }
 }
 
 /**
  * Should be called at the beginning of the program to set up the
  * network interface. It calls the function low_level_init() to do the
  * actual setup of the hardware.
  *
  * This function should be passed as a parameter to netif_add().
  *
  * @param netif the lwip network interface structure for this ethernetif
  * @return ERR_OK if the loopif is initialized
  *         ERR_MEM if private data couldn't be allocated
  *         any other err_t on error
  */
 err_t
 ethernetif_init(struct netif *netif)
 {
   struct ethernetif *ethernetif;
 
   LWIP_ASSERT("netif != NULL", (netif != NULL));
     
   ethernetif = mem_malloc(sizeof(struct ethernetif));
   if (ethernetif == NULL) {
     LWIP_DEBUGF(NETIF_DEBUG, ("ethernetif_init: out of memory\n"));
     return ERR_MEM;
   }
 
 #if LWIP_NETIF_HOSTNAME
   /* Initialize interface hostname */
   netif->hostname = "lwip";
 #endif /* LWIP_NETIF_HOSTNAME */
 
   /*
    * Initialize the snmp variables and counters inside the struct netif.
    * The last argument should be replaced with your link speed, in units
    * of bits per second.
    */
   NETIF_INIT_SNMP(netif, snmp_ifType_ethernet_csmacd, LINK_SPEED_OF_YOUR_NETIF_IN_BPS);
 
   netif->state = ethernetif;
   netif->name[0] = IFNAME0;
   netif->name[1] = IFNAME1;
   /* We directly use etharp_output() here to save a function call.
    * You can instead declare your own function an call etharp_output()
    * from it if you have to do some checks before sending (e.g. if link
    * is available...) */
   netif->output = etharp_output;
   netif->linkoutput = low_level_output;
   
   ethernetif->ethaddr = (struct eth_addr *)&(netif->hwaddr[0]);
   
   /* initialize the hardware */
   low_level_init(netif);
 
   return ERR_OK;
 }
 
 #endif /* 0 */