icmp_in.c

来自「TCP-IP红宝书源代码」· C语言 代码 · 共 87 行

/* icmp_in.c - icmp_in */

#include <conf.h>
#include <kernel.h>
#include <network.h>
#include <proc.h>

int icredirect(struct ep *);
void icsetsrc(struct ip *);

/*------------------------------------------------------------------------
 *  icmp_in  -  handle ICMP packet coming in from the network
 *------------------------------------------------------------------------
 */
int
icmp_in(struct netif *pni, struct ep *pep)
{
	struct	ip	*pip;
	struct	icmp	*pic;
	int		i, len;

	pip = (struct ip *)pep->ep_data;
	pic = (struct icmp *) pip->ip_data;

	len = pip->ip_len - IP_HLEN(pip);
	if (cksum((WORD *)pic, len)) {
		IcmpInErrors++;
		freebuf(pep);
		return SYSERR;
	}
	IcmpInMsgs++;
	switch(pic->ic_type) {
	case ICT_ECHORQ:
		IcmpInEchos++;
		return icmp(ICT_ECHORP, 0, pip->ip_src, pep, 0);
	case ICT_MASKRQ:
		IcmpInAddrMasks++;
		if (!gateway) {
			freebuf(pep);
			return OK;
		}
		pic->ic_type = (char) ICT_MASKRP;
		*(IPaddr *)pic->ic_data = netmask(pip->ip_dst);
		break;
	case ICT_MASKRP:
		IcmpInAddrMaskReps++;
		for (i=0; i<Net.nif; ++i)
			if (nif[i].ni_ip == pip->ip_dst)
				break;
		if (i != Net.nif) {
			setmask(i, *(IPaddr *)pic->ic_data);
			send(pic->ic_id, ICT_MASKRP);
		}
		freebuf(pep);
		return OK;
	case ICT_ECHORP:
		IcmpInEchoReps++;
		if (send(pic->ic_id, (int)pep) != OK)
			freebuf(pep);
		return OK;
	case ICT_REDIRECT:
		IcmpInRedirects++;
		icredirect(pep);
		return OK;
	case ICT_DESTUR: IcmpInDestUnreachs++;	freebuf(pep); return OK;
	case ICT_SRCQ:	 IcmpInSrcQuenchs++;	freebuf(pep); return OK;
	case ICT_TIMEX:	 IcmpInTimeExcds++;	freebuf(pep); return OK;
	case ICT_PARAMP: IcmpInParmProbs++;	freebuf(pep); return OK;
	case ICT_TIMERQ: IcmpInTimestamps++;	freebuf(pep); return OK;
	case ICT_TIMERP: IcmpInTimestampReps++;	freebuf(pep); return OK;
	default:
		IcmpInErrors++;
		freebuf(pep);
		return OK;
	}
	icsetsrc(pip);

	len = pip->ip_len - IP_HLEN(pip);

	pic->ic_cksum = 0;
	pic->ic_cksum = cksum((WORD *)pic, len);

	IcmpOutMsgs++;
	ipsend(pip->ip_dst, pep, len, IPT_ICMP, IPP_INCTL, IP_TTL);
	return OK;
}