icmp.c

本代码是本人毕设所做的GPRS数传系统的软件部分

#include "ip.h"
#include "icmp.h"
/*/////////////////////////////////////////////////////////////////////////////
File Name : ICMP.c
Author : Rene Trenado
Location : Motorola Applications Lab, Baja California
Date Created : January 2001
Current Revision : 0.0
Notes : This file contains the code to handle and create ICMP messages
//////////////////////////////////////////////////////////////////////////////*/

/***********************************************************************
Function : ICMPPing
Parameters : IP Address to ping
Date : September 2000
Desc : Sends a ICMP ECHO message to a remote host
***********************************************************************/
void IcmpPing (BYTE Ip[]) {
WORD Value;
static BYTE Seq = 0xAB;
ip_out->SourceAddress[0]=IPAddress[0];// Ping will have our source address
ip_out->SourceAddress [1] = IPAddress [1];
ip_out->SourceAddress [2] = IPAddress [2];
ip_out->SourceAddress [3] = IPAddress [3];
ip_out->DestAddress [0] = Ip[0]; // Set destination IP address
ip_out->DestAddress [1] = Ip[1];
ip_out->DestAddress [2] = Ip[2];
ip_out->DestAddress [3] = Ip[3];
ip_out->Payload [0] = ECHO; // ICMP message type set to ECHO
ip_out->Payload [1] = 0; // ICMP code must by set to zero
ip_out->Payload [2] = 0; // reset checksum
ip_out->Payload [3] = 0;
ip_out->Payload [4] = 1; // set ID of ICMP message
ip_out->Payload [5] = 0;
Seq++;
ip_out->Payload [6] = (Seq >> 8) & 0xFF; // set sequence number of ICMP Msg
ip_out->Payload [7] = Seq & 0xFF;
ip_out->Protocol = ICMP; // IP datagram will carry ICMP data
ip_out->Length = 28; // ECHO message doesn't include data
Value = IPCheckSum ((BYTE *)&ip_out->Payload[0], (ip_out->Length - 20) >> 1);
ip_out->Payload [2] = (Value >> 8); // obtain ICMP checksum
ip_out->Payload [3] = (Value & 0xFF);
IPNetSend (ip_out); // Net send to IP layer
}/***********************************************************************
Function : ICMP_Handler
Parameters : IP Datagram containing ICMP data
Date : September 2000
Desc : Handles incoming IP datagrams according to the TYPE field
of the ICMP message contained in the input IP datagram
***********************************************************************/
void IcmpHandler (IPDatagram* ip) {
WORD Value;
switch (ip->Payload [0]) {
case ECHO:
/* Move ping datagram to output buffer */
Move ((BYTE *)ip, (BYTE *)ip_out, ip->Length);
/* Swap source and destination IP addresses on Output Buffer */
ip_out->DestAddress[0]=ip->SourceAddress[0];
ip_out->DestAddress [1] = ip->SourceAddress [1];
ip_out->DestAddress [2] = ip->SourceAddress [2];
ip_out->DestAddress [3] = ip->SourceAddress [3];
ip_out->SourceAddress [0] = ip->DestAddress [0];
ip_out->SourceAddress [1] = ip->DestAddress [1];
ip_out->SourceAddress [2] = ip->DestAddress [2];
ip_out->SourceAddress [3] = ip->DestAddress [3];
ip_out->Payload [0] = ECHO_REPLY;/* Echo reply */
ip_out->Payload [1] = 0; /* Set ICMP Code to 0 */
ip_out->Payload [2] = 0; /* Set ICMP checksum to 0
during checksum generation */
ip_out->Payload [3] = 0;
Value = IPCheckSum ((BYTE *)&ip_out->Payload[0], (ip->Length - 20)>> 1); /* Calculate ICMP checksum */
ip_out->Payload [2] = (Value >> 8);/* Set ICMP checksum */
ip_out->Payload [3] = (Value & 0xFF);
IPNetSend (ip_out); /* Send ICMP packet over IP */
break;
case ECHO_REPLY: // Code to handle ping responses
// goes here
NoOperation;
break;
case TRACEROUTE:
break;
default:
break;
}
}