/* $Copyright: $
 * Copyright (c) 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991
 * Sequent Computer Systems, Inc.   All rights reserved.
 *  
 * This software is furnished under a license and may be used
 * only in accordance with the terms of that license and with the
 * inclusion of the above copyright notice.   This software may not
 * be provided or otherwise made available to, or used by, any
 * other person.  No title to or ownership of the software is
 * hereby transferred.
 */

#ifndef	lint
static	char	rcsid[] = "$Header: ip_icmp.c 2.9 1991/04/30 17:17:20 $";
#endif

/* $Log: ip_icmp.c,v $
 *
 */

#include "../h/param.h"
#include "../h/systm.h"
#include "../h/mutex.h"
#include "../machine/gate.h"
#include "../machine/intctl.h"
#include "../h/mbuf.h"
#include "../h/protosw.h"
#include "../h/socket.h"
#include "../h/time.h"
#include "../h/kernel.h"

#include "../net/route.h"
#include "../net/if.h"

#include "../netinet/in.h"
#include "../netinet/in_systm.h"
#include "../netinet/in_var.h"
#include "../netinet/ip.h"
#include "../netinet/ip_icmp.h"
#include "../netinet/icmp_var.h"

/*
 * ICMP routines: error generation, receive packet processing, and
 * routines to turnaround packets back to the originator, and
 * host table maintenance routines.
 */

struct	icmpstat icmpstat;

/*
 * Generate an error packet of type error
 * in response to bad packet ip.
 */

icmp_error(oip, type, code, ifp, dest)
	struct ip *oip;
	int type, code;
	struct ifnet *ifp;
	struct in_addr dest;
{
	register unsigned oiplen = oip->ip_hl << 2;
	register struct icmp *icp;
	struct mbuf *m;
	struct ip *nip;
	unsigned icmplen;

	if (type != ICMP_REDIRECT)
		icmpstat.icps_error++;
	/*
	 * Don't send error if not the first fragment of message.
	 * Don't EVER error if the old packet protocol was ICMP.
	 * (Could do ECHO, etc, but not error indications.)
	 */
	if (oip->ip_off &~ (IP_MF|IP_DF))
		goto free;
	if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT) {
		icmpstat.icps_oldicmp++;
		goto free;
	}

	/*
	 * First, formulate icmp message
	 */
	m = m_get(M_DONTWAIT, MT_HEADER);
	if (m == NULL) {
		icmpstat.icps_outerrors++;
		goto free;
	}
	icmplen = oiplen + MIN(8, oip->ip_len);
	m->m_len = icmplen + ICMP_MINLEN;
	m->m_off = MMAXOFF - m->m_len;
	icp = mtod(m, struct icmp *);
	ASSERT((u_int) type <= ICMP_MAXTYPE, "icmp_error");
	icmpstat.icps_outhist[type]++;
	icp->icmp_type = type;
	if (type == ICMP_REDIRECT)
		icp->icmp_gwaddr = dest;
	else
		icp->icmp_void = 0;
	if (type == ICMP_PARAMPROB) {
		icp->icmp_pptr = code;
		code = 0;
	}
	icp->icmp_code = code;
	bcopy((caddr_t)oip, (caddr_t)&icp->icmp_ip, icmplen);
	nip = &icp->icmp_ip;
	nip->ip_len += oiplen;
	nip->ip_len = htons((u_short)nip->ip_len);

	/*
	 * Now, copy old ip header in front of icmp message.
	 */
	if (m->m_len + oiplen > MLEN)
		oiplen = sizeof(struct ip);
	if(m->m_len + oiplen > MLEN) {
		(void) m_free(m);
		icmpstat.icps_outerrors++;
		goto free;		/* don't panic */
	}
	m->m_off -= oiplen;
	m->m_len += oiplen;
	nip = mtod(m, struct ip *);
	bcopy((caddr_t)oip, (caddr_t)nip, oiplen);
	nip->ip_len = m->m_len;
	nip->ip_p = IPPROTO_ICMP;
	icmp_reflect(nip, ifp);

free:
	m_freem(dtom(oip));
}

static struct sockproto icmproto = { AF_INET, IPPROTO_ICMP };
static struct sockaddr_in icmpsrc = { AF_INET };
static struct sockaddr_in icmpdst = { AF_INET };
static struct sockaddr_in icmpgw = { AF_INET };
struct in_ifaddr *ifptoia();

/*
 * Process a received ICMP message.
 */

icmp_input(m, ifp)
	register struct mbuf *m;
	struct ifnet *ifp;
{
	register struct icmp *icp;
	register struct ip *ip = mtod(m, struct ip *);
	int icmplen = ip->ip_len, hlen = ip->ip_hl << 2;
	register int i;
	struct in_ifaddr *ia;
	int (*ctlfunc)(), code;
	extern u_char ip_protox[];
	extern struct in_addr in_makeaddr();

	/*
	 * Locate icmp structure in mbuf, and check
	 * that not corrupted and of at least minimum length.
	 */

	if (icmplen < ICMP_MINLEN) {
		icmpstat.icps_tooshort++;
		goto free;
	}
	i = hlen + MIN(icmplen, ICMP_ADVLENMIN);
 	if ((m->m_off > MMAXOFF || m->m_len < i) &&
 		(m = m_pullup(m, i)) == 0)  {
		icmpstat.icps_tooshort++;
		return;
	}
 	ip = mtod(m, struct ip *);
	m->m_len -= hlen;
	m->m_off += hlen;
	icp = mtod(m, struct icmp *);
	if (in_cksum(m, icmplen)) {
		icmpstat.icps_checksum++;
		goto free;
	}
	m->m_len += hlen;
	m->m_off -= hlen;

	if (icp->icmp_type > ICMP_MAXTYPE)
		goto raw;
	icmpstat.icps_inhist[icp->icmp_type]++;
	code = icp->icmp_code;
	switch (icp->icmp_type) {

	case ICMP_UNREACH:
		if (code > 5)
			goto badcode;
		code += PRC_UNREACH_NET;
		goto deliver;

	case ICMP_TIMXCEED:
		if (code > 1)
			goto badcode;
		code += PRC_TIMXCEED_INTRANS;
		goto deliver;

	case ICMP_PARAMPROB:
		if (code)
			goto badcode;
		code = PRC_PARAMPROB;
		goto deliver;

	case ICMP_SOURCEQUENCH:
		if (code)
			goto badcode;
		code = PRC_QUENCH;
	deliver:
		/*
		 * Problem with datagram; advise higher level routines.
		 */
		icp->icmp_ip.ip_len = ntohs((u_short)icp->icmp_ip.ip_len);
		if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp)) {
			icmpstat.icps_badlen++;
			goto free;
		}

		icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
		if (ctlfunc = inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput)
			(*ctlfunc)(code, (struct sockaddr *)&icmpsrc);
		break;

	badcode:
		icmpstat.icps_badcode++;
		break;

	case ICMP_ECHO:
		icp->icmp_type = ICMP_ECHOREPLY;
		goto reflect;

	case ICMP_TSTAMP:
		if (icmplen < ICMP_TSLEN) {
			icmpstat.icps_badlen++;
			break;
		}
		icp->icmp_type = ICMP_TSTAMPREPLY;
		icp->icmp_rtime = iptime();
		icp->icmp_ttime = icp->icmp_rtime;	/* bogus, do later! */
		goto reflect;
		
	case ICMP_IREQ:
#define	satosin(sa)	((struct sockaddr_in *)(sa))
		if (in_netof(ip->ip_src) == 0 && (ia = ifptoia(ifp)))
			ip->ip_src = in_makeaddr(in_netof(IA_SIN(ia)->sin_addr),
			    in_lnaof(ip->ip_src));
		icp->icmp_type = ICMP_IREQREPLY;
		goto reflect;

	case ICMP_MASKREQ:
		if (icmplen < ICMP_MASKLEN || (ia = ifptoia(ifp)) == 0)
			break;
		icp->icmp_type = ICMP_MASKREPLY;           
		icp->icmp_mask = htonl(ia->ia_subnetmask); 
		if (ip->ip_src.s_addr == 0) {
			if (ia->ia_ifp->if_flags & IFF_BROADCAST)
			    ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr;
			else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT)
			    ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr;
		}
reflect:
		ip->ip_len += hlen;	/* since ip_input deducts this */
		icmpstat.icps_reflect++;
		icmpstat.icps_outhist[icp->icmp_type]++;
		icmp_reflect(ip, ifp);
		return;

	case ICMP_REDIRECT:
		if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp)) {
			icmpstat.icps_badlen++;
			break;
		}
		/*
		 * Short circuit routing redirects to force
		 * immediate change in the kernel's routing
		 * tables.  The message is also handed to anyone
		 * listening on a raw socket (e.g. the routing
		 * daemon for use in updating its tables).
		 */

		icmpgw.sin_addr = ip->ip_src;
		icmpdst.sin_addr = icp->icmp_gwaddr;

		if (code == ICMP_REDIRECT_NET || code == ICMP_REDIRECT_TOSNET) {
			icmpsrc.sin_addr =
			 in_makeaddr(in_netof(icp->icmp_ip.ip_dst), INADDR_ANY);
			rtredirect((struct sockaddr *)&icmpsrc,
			  (struct sockaddr *)&icmpdst, RTF_GATEWAY,
			  (struct sockaddr *)&icmpgw);
			icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
			pfctlinput(PRC_REDIRECT_NET,
			  (struct sockaddr *)&icmpsrc);
		} else {
			icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
			rtredirect((struct sockaddr *)&icmpsrc,
			  (struct sockaddr *)&icmpdst, RTF_GATEWAY | RTF_HOST,
			  (struct sockaddr *)&icmpgw);
			pfctlinput(PRC_REDIRECT_HOST,
			  (struct sockaddr *)&icmpsrc);
		}
		break;

	/*
	 * No kernel processing for the following;
	 * just fall through to send to raw listener.
	 */
	case ICMP_ECHOREPLY:
	case ICMP_TSTAMPREPLY:
	case ICMP_IREQREPLY:
	case ICMP_MASKREPLY:
	default:
		break;
	}

raw:
	icmpsrc.sin_addr = ip->ip_src;
	icmpdst.sin_addr = ip->ip_dst;
	raw_input(m, &icmproto, (struct sockaddr *)&icmpsrc,
	    (struct sockaddr *)&icmpdst);
	return;

free:
	m_freem(m);
}

/*
 * Reflect the ip packet back to the source
 */
icmp_reflect(ip, ifp)
	register struct ip *ip;
	struct ifnet *ifp;
{
	register struct in_ifaddr *ia;
	struct in_addr t;
	struct mbuf *opts = 0, *ip_srcroute();
	int optlen = (ip->ip_hl << 2) - sizeof(struct ip);

	t = ip->ip_dst;
	ip->ip_dst = ip->ip_src;
	/*
	 * If the incoming packet was addressed directly to us,
	 * use dst as the src for the reply.  Otherwise (broadcast
	 * or anonymous), use the address which corresponds
	 * to the incoming interface.
	 */
	for (ia = in_ifaddr; ia; ia = ia->ia_next) {
		if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr)
			break;
		if ((ia->ia_ifp->if_flags & IFF_BROADCAST) &&
		    t.s_addr == satosin(&ia->ia_broadaddr)->sin_addr.s_addr)
			break;
	}
	if (ia == (struct in_ifaddr *)0)
		ia = ifptoia(ifp);
	if (ia == (struct in_ifaddr *)0)
		ia = in_ifaddr;
	t = IA_SIN(ia)->sin_addr;
	ip->ip_src = t;
	ip->ip_ttl = ip_ttl;

	if (optlen > 0) {
		/*
		 * Retrieve any source routing from the incoming packet
		 * and strip out other options.  Adjust the IP length.
		 */
		opts = ip_srcroute();
		ip->ip_len -= optlen;
		ip_stripoptions(ip, (struct mbuf *)0);
	}
	icmp_send(ip, opts);
	if (opts)
		(void)m_free(opts);
}

struct in_ifaddr *
ifptoia(ifp)
	struct ifnet *ifp;
{
	register struct in_ifaddr *ia;

	for (ia = in_ifaddr; ia; ia = ia->ia_next)
		if (ia->ia_ifp == ifp)
			return (ia);
	return ((struct in_ifaddr *)0);
}

/*
 * Send an icmp packet back to the ip level,
 * after supplying a checksum.
 */

icmp_send(ip, opts)
	register struct ip *ip;
	struct mbuf *opts;
{
	register int hlen;
	register struct icmp *icp;
	register struct mbuf *m;

	m = dtom(ip);
	hlen = ip->ip_hl << 2;
	m->m_off += hlen;
	m->m_len -= hlen;
	icp = mtod(m, struct icmp *);
	icp->icmp_cksum = 0;
	icp->icmp_cksum = in_cksum(m, ip->ip_len - hlen);
	m->m_off -= hlen;
	m->m_len += hlen;
	(void) ip_output(m, opts, (struct route *)0, 0);
}

n_time
iptime()
{
	u_long t;
	GATESPL(s);

	P_GATE(G_TIME, s);
	t = (time.tv_sec % (24*60*60)) * 1000 + time.tv_usec / 1000;
	V_GATE(G_TIME, s);
	return (htonl(t));
}
