arp.c

实用的程序代码

/*
 * arp file
 */

#include <net/xilsock.h>

/*
 * xilnet_arp: handler for arp packets
 */

int xilnet_arp(unsigned char *buf, int len) {

  struct xilnet_arp_pkt* ar = (struct xilnet_arp_pkt*) (buf+ETH_HDR_LEN);
  
  // Analyse if its a arp request and send a reply if needed
  if (ar->hdr.hard_type == ARP_HARD_TYPE_ETH && ar->hdr.prot_type == ETH_PROTO_IP && 
      ar->hdr.hard_size == ARP_HARD_SIZE && ar->hdr.prot_size == ARP_PROTO_IP_SIZE &&
      (ar->target_ip[0] == mb_ip_addr[0] && ar->target_ip[1] == mb_ip_addr[1] &&
       ar->target_ip[2] == mb_ip_addr[2] && ar->target_ip[3] == mb_ip_addr[3]) ) {
    if (ar->hdr.op == ARP_REQ) {
      // update hw addr table
      xilnet_eth_update_hw_tbl(buf, ETH_PROTO_ARP);
      xilnet_arp_reply(buf+ETH_HDR_LEN, len-ETH_HDR_LEN);
    }
  }
  return 0;
}


/* 
 * xilnet_arp_reply: 
 */

void xilnet_arp_reply(unsigned char *buf, int len) {

  int i;
  struct xilnet_arp_pkt *pkt;
  struct xilnet_arp_pkt *arp_req = (struct xilnet_arp_pkt*) buf;
  struct xilnet_arp_pkt *arp_reply;
#ifdef _DEBUG_  
//    print("arp_reply(): \n");
#endif
  pkt = (struct xilnet_arp_pkt*)(sendbuf+ETH_HDR_LEN);
  
  pkt->hdr.hard_type = ARP_HARD_TYPE_ETH;
  pkt->hdr.prot_type = ETH_PROTO_IP;
  pkt->hdr.hard_size = ARP_HARD_SIZE;
  pkt->hdr.prot_size = ARP_PROTO_IP_SIZE;  
  pkt->hdr.op = ARP_REPLY;
  
  for (i = 0; i < ETH_ADDR_LEN; i++) {
    pkt->sender_hw[i] = mb_hw_addr[i];
    pkt->target_hw[i] = arp_req->sender_hw[i];
  }
  
  for (i = 0; i < ARP_PROTO_IP_SIZE ; i++) {
    pkt->sender_ip[i] = mb_ip_addr[i];
    pkt->target_ip[i] = arp_req->sender_ip[i];
  }
  memset(pkt->pad, 0, ARP_PAD_SIZE);
  
  /* initialize ethernet header */
  xilnet_eth_send_frame(sendbuf, ETH_MIN_FRAME_LEN, arp_req->sender_ip, pkt->target_hw, ETH_PROTO_ARP);
  
}