icmp.c

实用的程序代码

/*
 * ICMP layer specific functions
 */

#include <net/xilsock.h>
#include <string.h>

/*
 * icmp packet handler - handles only echo requests (ping program requests)
 * "buf" is an IP datagram
 */

int xilnet_icmp(unsigned char* buf, int len) {
   
   struct xilnet_icmp_hdr *icmph = (struct xilnet_icmp_hdr*) (buf+IP_HDR_LEN*4);
   
   if ((icmph->type == ICMP_ECHO_REQ_TYPE) && (icmph->code == ICMP_ECHO_CODE)) {
      xilnet_icmp_echo_reply( buf, len);	
   }
   return 0;
}


void xilnet_icmp_echo_reply(unsigned char *buf, int len) {
  
   short w0, w1, w2, w3;
   struct xilnet_icmp_hdr* icmp_req = (struct xilnet_icmp_hdr*) (buf + IP_HDR_LEN*4);
   struct xilnet_icmp_hdr* icmp_reply = (struct xilnet_icmp_hdr*)(sendbuf+LINK_HDR_LEN+IP_HDR_LEN*4);
   char * icmp_buf = &sendbuf[LINK_HDR_LEN+IP_HDR_LEN*4];
   
   icmp_reply->type = ICMP_ECHO_REPLY_TYPE;
   icmp_reply->code = ICMP_ECHO_CODE;
   icmp_reply->check_sum = 0;
   icmp_reply->ident = icmp_req->ident;
   icmp_reply->seq_no = icmp_req->seq_no;
   icmp_reply->check_sum = xilnet_ip_calc_chksum(sendbuf + LINK_HDR_LEN+(IP_HDR_LEN*4), ICMP_HDR_LEN);
   
   // call ip
   xilnet_ip_header(sendbuf+LINK_HDR_LEN, ICMP_HDR_LEN+(IP_HDR_LEN*4), IP_PROTO_ICMP, (buf+IP_SADDR_BASE) );
   
   // call ethernet
   xilnet_eth_send_frame(sendbuf, len+ICMP_HDR_LEN+IP_HDR_LEN*4+ETH_HDR_LEN, (buf+IP_SADDR_BASE), NULL, ETH_PROTO_IP);
   
}