ip.c

实用的程序代码

/*
 * IP layer specific functions
 */

#include <net/xilsock.h>


/* 
 * initialize xilnet ip address
 */
void xilnet_ip_init(unsigned char* addr) {
   int k = 0;
   int j;
   int sum = 0;
  
   for (j = 0; j < 3; j++) {
   
      // parse input for dotted decimal notation of ip address
      while(addr[k] != '.') { 
         sum = sum * 10 + addr[k] - 48;
         k++;
      }
    
      k++; // move over the dot
      mb_ip_addr[j] = (unsigned char) sum;
      sum = 0;    
   }
   
   // read last byte of ip address
   while (addr[k] != '\0') {
      sum = sum * 10 + addr[k] - 48;
      k++;
   }  
   mb_ip_addr[3] = (unsigned char) sum;

}


/* 
 * ip datagram handler:
 * checks for the source ip address and calls the corr protocol handler
 * no checksum calc is done to detect any errors
 */

int xilnet_ip(unsigned char*buf, int len) {
  
  int iplen = 0;
  struct xilnet_ip_hdr *iph = (struct xilnet_ip_hdr *) (buf+ETH_HDR_LEN);
#ifdef _DEBUG_  
  //print("In ip(): \n");
#endif
  if ((buf+ETH_HDR_LEN)[IP_DADDR_BASE] == mb_ip_addr[0] && (buf+ETH_HDR_LEN)[IP_DADDR_BASE+1] == mb_ip_addr[1] &&
      (buf+ETH_HDR_LEN)[IP_DADDR_BASE+2] == mb_ip_addr[2] && (buf+ETH_HDR_LEN)[IP_DADDR_BASE+3] == mb_ip_addr[3]) {
    // update hw addr table
    xilnet_eth_update_hw_tbl(buf, ETH_PROTO_IP);
    
    iplen = (unsigned short)( ((((unsigned short)buf[ETH_HDR_LEN+2]) << 8) & 0xFF00) + 
                                (((unsigned short)buf[ETH_HDR_LEN+3]) & 0x00FF) );
    
    // call corr protocol handler with the ip datagram
      switch (iph->prot) {
      case IP_PROTO_UDP:
	return (xilnet_udp(buf+ETH_HDR_LEN, iplen));
	break;
      case IP_PROTO_TCP:
	return (xilnet_tcp(buf+ETH_HDR_LEN, iplen));
	break;
      case IP_PROTO_ICMP:
	return (xilnet_icmp(buf+ETH_HDR_LEN, iplen));
	break;
      default:
	break;
      }
  }
  return 0;
}


/* 
 * xilnet_ip_header: fills in the ip header for proto
 */
int ip_id_cnt = 0;

void xilnet_ip_header(unsigned char* buf, int len, int proto, unsigned char *peer_ip_addr) {
  
   struct xilnet_ip_hdr *iph = (struct xilnet_ip_hdr*) buf;
   unsigned short temp;

#ifdef _DEBUG_
   //  print("ip_header(): \n");
#endif /*  _DEBUG_ */
   
   buf[0] = IP_VERSION << 4;
   buf[0] |= IP_HDR_LEN;
   iph->tos = IP_TOS;
   iph->total_len = len;
   iph->ident = ip_id_cnt++;
   iph->frag_off = IP_FRAG_OFF;
   iph->ttl = IP_TTL;
   iph->prot = proto;
   iph->check_sum = 0;
   buf[IP_SADDR_BASE]  = mb_ip_addr[0];
   buf[IP_SADDR_BASE+1] = mb_ip_addr[1];
   buf[IP_SADDR_BASE+2] = mb_ip_addr[2];
   buf[IP_SADDR_BASE+3] = mb_ip_addr[3];
   buf[IP_DADDR_BASE]  = peer_ip_addr[0];
   buf[IP_DADDR_BASE+1] = peer_ip_addr[1];
   buf[IP_DADDR_BASE+2] = peer_ip_addr[2];
   buf[IP_DADDR_BASE+3] = peer_ip_addr[3];
   iph->check_sum = xilnet_ip_calc_chksum(buf, IP_HDR_LEN*4);
   
}


/*
 * xilnet_ip_calc_chksum: compute checksum for ip header
 */

unsigned short xilnet_ip_calc_chksum(unsigned char* buf, int len) {
  
   unsigned int sum = 0;
   unsigned short w16 = 0;
   int i;

   for (i = 0; i < len; i = i + 2) {
      w16 = ((buf[i] << 8) & 0xFF00) + (buf[i+1] & 0x00FF);
      sum = sum + (unsigned int) w16;
   }
  
   while (sum >> 16) 
      sum = (sum & 0xFFFF) + (sum >> 16);
  
   return (unsigned short) (~sum);
}