/*
    Copyright 2000 (c) by David Schweikert,
    Swiss Federal Institute of Technology,
    Computer Engineering and Networks Laboratory.

    TOPSY -- A Teachable Operating System.
             Implementation of a tiny and simple
             micro kernel for teaching purposes.

    For further information, please visit http://www.tik.ee.ethz.ch/~topsy

    This software is provided under the terms of the GNU General Public 
    Licence. A full copy of the GNU GPL is provided in the file COPYING 
    found in the development root of Topsy.
*/
/*
	
    File:                  $Source: /usr/drwho/vault/cvs/topsy/Topsy/Net/ICMP/NetICMP.c,v $
    Author(s):             
    Affiliation:           ETH Zuerich, TIK
    Version:               $Revision: 1.1 $
    Creation Date:         
    Last Date of Change:   $Date: 2000/03/31 17:50:36 $      by: $Author: gfa $


    $Log: NetICMP.c,v $
    Revision 1.1  2000/03/31 17:50:36  gfa
    Merged with /Net from several term projects


*/
#include "NetICMP.h"

#include <Topsy.h>
#include <Messages.h>
#include <Syscall.h>
#include <NetAttr.h>
#include <NetBuf.h>
#include <NetConfig.h>
#include <NetDebug.h>
#include <NetIface.h>
#include <NetModules.h>
#include <IP/NetIP.h>
#include <IP/NetIPchecksum.h>

void neticmpRead(ThreadId id, unsigned long int length);
static void neticmpMain(ThreadArg arg);
static void neticmpUp(NetBuf buf, NetAttrs attrs);
static void neticmpDown(NetBuf buf, NetAttrs attrs);

void neticmpInit()
{
	ThreadId neticmpId;
	
	/* Start main thread */
	if (tmStart(&neticmpId, neticmpMain, (ThreadArg)0, "neticmp") != TM_STARTOK) {
		netdbgDisplay(NETDEBUG_GENERIC, "Start: couldn't start ICMP thread\n");
		return;
	}
}

static void neticmpMain(ThreadArg arg)
{
	ThreadId myThreadId, parentThreadId;
	NetModMsg msg;

	tmGetInfo(SELF, &myThreadId, &parentThreadId);

	// Add to list of modules
	netmodAdd(NETMODULE_ICMP, myThreadId);
	
	netdbgPrintf(NETDEBUG_MODULES,
		     "ICMP module started (moduleId=%d, threadId=%d).\n",
		     NETMODULE_ICMP, myThreadId);

	while(1) {
		if(!netmodMsgRecv(&msg)) return;

		switch (msg.id) {
		case NETMOD_SENDUP:
			neticmpUp(msg.buf, msg.attrs);
			break;
		case NETMOD_SENDDOWN:
			neticmpDown(msg.buf, msg.attrs);
			break;
		default:
			netdbgPrintf(NETDEBUG_GENERIC,
				      "*** ERROR: ICMP: Unknown message (%d)!\n",
				     msg.id);
			break;
		}
	}
}

static void neticmpEchoUp(NetBuf buf, NetAttrs attrs)
{
	NetICMPHdr hdr=(NetICMPHdr) NETBUF_DATA(buf);
	NetAttrs newattrs=0;
	unsigned short tmp;
	
	netdbgDisplay(NETDEBUG_ICMP, "neticmp: Got ECHO REQUEST.\n");

	/* We resend exactly the same data to the sender. */
	/* Only 'type' is changed from ECHO to ECHOREPLY */
	hdr->type = NETICMP_TYPE_ECHOREPLY;

	/* We rebuild the attributes for the down-going packet */
	if(!netattrNew(&newattrs)) goto error;

	/* Determine sender and set destination to the same. */
	if(!netattrGet(attrs, NETATTR_IP_FROM_0, &tmp)) goto error;
	netattrSet(newattrs, NETATTR_IP_TO_0, tmp);
	if(!netattrGet(attrs, NETATTR_IP_FROM_1, &tmp)) goto error;
	netattrSet(newattrs, NETATTR_IP_TO_1, tmp);
	if(!netattrGet(attrs, NETATTR_IP_FROM_2, &tmp)) goto error;
	netattrSet(newattrs, NETATTR_IP_TO_2, tmp);
	if(!netattrGet(attrs, NETATTR_IP_FROM_3, &tmp)) goto error;
	netattrSet(newattrs, NETATTR_IP_TO_3, tmp);

	/* 'Protocol' for IP is ICMP */
	netattrSet(newattrs, NETATTR_IP_PROTOCOL, NETIP_PROTOCOL_ICMP);

	/* Re-calculate checksum (see RFC 1141) */
	/* ~C' = ~(C + (-m) + m') = ~C + (m - m') = ~C + m + ~m' */
	hdr->checksum+=NETICMP_TYPE_ECHO + ~(NETICMP_TYPE_ECHOREPLY);
	//hdr->checksum=htons(netipChecksum(buf,netbufLen(buf)));
	
	/* Send down the reply packet */
	netdbgDisplay(NETDEBUG_ICMP, "neticmp: Sending ECHO REPLY.\n");
	netcfgSendNextDown(NETMODULE_ICMP, buf, newattrs);

	/* Free the old attributes */
	netattrFree(attrs);
	
	return;
	
error:
	netdbgDisplay(NETDEBUG_ICMP, "neticmp: Discarding packet.\n");
	if(newattrs) netattrFree(newattrs);
	netattrFree(attrs);
	netbufFree(buf);
}

static void neticmpUp(NetBuf buf, NetAttrs attrs)
{
	NetICMPHdr hdr=(NetICMPHdr) NETBUF_DATA(buf);
	int len = netbufLen(buf);
	
	/* Process packet and fill attrs */
	
	netdbgPrintf(NETDEBUG_ICMP, "neticmp: Got packet (len=%d).\n",NETBUF_LEN(buf));
	
	/* Check length */
	if(len<4) goto discard;

	/* Check checksum */
	if(netipChecksum(buf,netbufLen(buf))) {
		netdbgPrintf(NETDEBUG_GENERIC, "neticmp: Checkum error!\n");
		goto discard;
	}
	
	switch(hdr->type) {
	case NETICMP_TYPE_ECHO: neticmpEchoUp(buf,attrs); break;
	default: goto discard;
	}

	return;
	
discard:
	netdbgDisplay(NETDEBUG_ICMP, "neticmp: Discarding packet.\n");
	netbufFree(buf);
	netbufFree((NetBuf)attrs);
}

static void neticmpDown(NetBuf buf, NetAttrs attrs)
{
	/* Build header and fill attrs */
	
	/* Send down packet */
	netcfgSendNextDown(NETMODULE_ICMP, buf, attrs);
}