icmp_input.c

一款类linux的操作系统源码

/*
 *  Roadrunner/pk
 *    Copyright (C) 1989-2002  Cornfed Systems, Inc.
 *
 *  The Roadrunner/pk operating system is free software; you can
 *  redistribute and/or modify it under the terms of the GNU General
 *  Public License, version 2, as published by the Free Software
 *  Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public
 *  License along with this program; if not, write to the Free
 *  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *  MA 02111-1307 USA
 *
 *  More information about the Roadrunner/pk operating system of
 *  which this file is a part is available on the World-Wide Web
 *  at: http://www.cornfed.com.
 *
 */

#include <net/ether.h>
#include <net/icmp.h>
#include <net/ip.h>
#include <net/netif.h>
#if _DEBUG_ICMP
#include <stdio.h>
#endif
#include <string.h>

u_short cksum(void *buf, int len);

void
icmp_input(buf_t b)
{
    etherhdr_t eh = (etherhdr_t) bstart(b);
    iphdr_t ih = (iphdr_t) eh->data;
    icmphdr_t ich = (icmphdr_t) (eh->data + IP_HLEN(ih));

    if (ich->type == ICMP_ECHO_REQUEST) {
	ipaddr ip;
	int len;

	/* Format and send an ICMP echo reply */
	ich->type = ICMP_ECHO_REPLY;
	ip = ih->dst;
	ih->dst = ih->src;
	ih->src = ip;
	bcopy(eh->src, eh->dst, ETHER_ADDR_LEN);
	ich->cksum = 0;
	len = NET2HS(ih->len) - IP_HLEN(ih);
	ich->cksum = cksum(ich, len);
	netif_send(b);
	return;
    }
#if _DEBUG_ICMP
    switch (ich->type) {
    case ICMP_ECHO_REPLY:
	kprintf("icmp_input: echo reply\n");
	break;
    case ICMP_DEST_UNREACH:
	kprintf("icmp_input: destination unreachable\n");
	break;
    case ICMP_REDIRECT:
	kprintf("icmp_input: redirect\n");
	break;
    case ICMP_TIMESTAMP_REQUEST:
	kprintf("icmp_input: timestamp request\n");
	break;
    case ICMP_TIMESTAMP_REPLY:
	kprintf("icmp_input: timestamp reply\n");
	break;
    default:
	kprintf("icmp_input: unsupported type (%02x)\n", ich->type);
    }
#endif
    brel(b);
}