ip.c

阿根廷教授编写的嵌入式internet的实验教程的高质量代码

/******************************************************************************************
   ip.c (v1.0)
-------------------------------------------------------------------------------------
This code is from the book:
"Embedded Internet: TCP/IP Basics, Implementation and Applications" by Sergio Scaglia
[Pearson Education, 2006 - ISBN: 0-32-130638-4]

This code is copyright (c) 2006 by Sergio Scaglia, and it may only be used for educational
purposes.  For commercial use, please contact me at [e-mail]
For more information and updates, please visit www.embeddedinternet.org
******************************************************************************************/

#include "stack.h"
#include "ip.h"
#ifdef ETHERNET
  #include "Ethernet.h"
#endif
#ifdef PPP_LINK
  #include "PPP.h"
#endif
#include <stdio.h>
#include <string.h>	

unsigned short ipid;			


/***************************************/
/* IP Private Functions                */
/***************************************/
#if debug_ip
void ip_display(void) {
  printf("IP Message:\n");
  printf("IP Version:       %d\n", (IPr->verhl>>4));
  printf("Hdr Len:          %d bytes\n", (IPr->verhl & 0x0F) * 4);
  printf("TOS:              0x%02x\n", IPr->tos);
  printf("Tot Len:          %d bytes\n", HTONS(IPr->len));
  printf("Id:               %d\n", HTONS(IPr->id));
  printf("Fragment:         0x%04x\n", HTONS(IPr->fragment));
  printf("TTL:              %d\n", IPr->ttl);
  printf("Protocol:         %d\n", IPr->protocol);
  printf("Hdr Chksum:       0x%04x\n", HTONS(IPr->hdrchksum));
  printf("Source Address:   %d.%d.%d.%d\n", IPr->srcipaddr[0], IPr->srcipaddr[1], IPr->srcipaddr[2], IPr->srcipaddr[3]);
  printf("Dest.  Address:   %d.%d.%d.%d\n", IPr->destipaddr[0], IPr->destipaddr[1], IPr->destipaddr[2], IPr->destipaddr[3]);														
  printf("\n--------------------------------\n");
}
#endif //debug_ip



/***************************************/
/*   IP Public Functions               */
/***************************************/
int chksum16(void *buf1, short len, int chksum, char complement) {
  unsigned short * buf = buf1;
  int chksum16;

  while(len > 0) {	
    if (len == 1)
      chksum16 = ((*buf)&0x00FF);
    else
      chksum16 = (*buf);
    chksum = chksum + HTONS(chksum16);
    *buf++;
    len -=2;
  }
  if (complement)
    return (~(chksum + ((chksum & 0xFFFF0000) >> 16))&0xFFFF);
  return chksum;
}


void ip_process(void) {
  unsigned short len;
  unsigned short chksum1;
  unsigned short chksum2;


#if debug_ip
  ip_display();
#endif //debug_ip


  if ((IPr->verhl & 0xF0) != 0x40) {
    printf("IP: packet version not supported!\r\n");
    return;
  }
  if ((IPr->verhl & 0x0F) != 0x05) {
    printf("IP: header options not supported!\r\n");
    return;
  }
  if ((HTONS(IPr->fragment) & 0x1FFF) != 0x0000) {
    printf("IP: fragmented packets not supported!\r\n");
    return;
  }
  chksum1 = HTONS(IPr->hdrchksum);
  IPr->hdrchksum = 0;
  chksum2 = chksum16(&IPr->verhl, (IPr->verhl & 0x0F) * 4, 0, 1);
  if (chksum2 != chksum1) {
    printf("IP: Bad Checksum %04x (it should be %04x)\n",chksum1, chksum2);
    return;											// returns if chksum failed!
  }
  IPr->hdrchksum = HTONS(chksum1);				// restore checksum
  if (memcmp(IPr->destipaddr, MyIP, 4))				// is this IP datagram for us?
    return;											// if not, return

  len = HTONS(IPr->len) - ((IPr->verhl & 0x0F) * 4); 		// Length of IP Data
  switch (IPr->protocol) {
    case ICMP_PROTOCOL:
    //icmp_process(len);
      break;
    case UDP_PROTOCOL:
    //udp_process(len);
      break;
    case TCP_PROTOCOL:
    //tcp_process(len);
      break;
    default:	            //  send Protocol Unreachable ICMP message...
    //  ICMP Protocol Not Yet Implemented...			
      break;
  }
}


void ip_send(char protocol, char *IPdest, unsigned short len) {

  IPt->verhl=0x45;
  IPt->tos=0x00;
  IPt->len=HTONS(len+sizeof(struct ip_hdr));		
  ipid++;
  IPt->id = HTONS(ipid);
  IPt->fragment=0;
  IPt->ttl=128;
  IPt->protocol=protocol;     		
  IPt->hdrchksum=0;
  memcpy(IPt->destipaddr, IPdest, 4);
  memcpy(IPt->srcipaddr, MyIP, 4);		
  IPt->hdrchksum = HTONS(chksum16(&IPt->verhl, (IPt->verhl & 0x0F) * 4, 0, 1));
  datalink_send(IP_PROTOCOL, len+sizeof(struct ip_hdr));					
}