xnu-792.13.8.tar.gz

[apple/xnu.git] / bsd / netinet / ip_icmp.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_OSREFERENCE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code 
 * as defined in and that are subject to the Apple Public Source License 
 * Version 2.0 (the 'License'). You may not use this file except in 
 * compliance with the License.  The rights granted to you under the 
 * License may not be used to create, or enable the creation or 
 * redistribution of, unlawful or unlicensed copies of an Apple operating 
 * system, or to circumvent, violate, or enable the circumvention or 
 * violation of, any terms of an Apple operating system software license 
 * agreement.
 *
 * Please obtain a copy of the License at 
 * http://www.opensource.apple.com/apsl/ and read it before using this 
 * file.
 *
 * The Original Code and all software distributed under the License are 
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 
 * Please see the License for the specific language governing rights and 
 * limitations under the License.
 *
 * @APPLE_LICENSE_OSREFERENCE_HEADER_END@
 */
/*
 * Copyright (c) 1982, 1986, 1988, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)ip_icmp.c	8.2 (Berkeley) 1/4/94
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/route.h>

#define _IP_VHL
#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/ip_var.h>
#include <netinet/icmp_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>

#if IPSEC
#include <netinet6/ipsec.h>
#include <netkey/key.h>
#endif

#if defined(NFAITH) && NFAITH > 0
#include "faith.h"
#include <net/if_types.h>
#endif

 /* XXX This one should go in sys/mbuf.h. It is used to avoid that
 * a firewall-generated packet loops forever through the firewall.
 */
#ifndef M_SKIP_FIREWALL
#define M_SKIP_FIREWALL         0x4000
#endif

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

static struct	icmpstat icmpstat;
SYSCTL_STRUCT(_net_inet_icmp, ICMPCTL_STATS, stats, CTLFLAG_RD,
	&icmpstat, icmpstat, "");

static int	icmpmaskrepl = 0;
SYSCTL_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_RW,
	&icmpmaskrepl, 0, "");

static int	icmptimestamp = 0;
SYSCTL_INT(_net_inet_icmp, ICMPCTL_TIMESTAMP, timestamp, CTLFLAG_RW,
	&icmptimestamp, 0, "");

static int	drop_redirect = 0;
SYSCTL_INT(_net_inet_icmp, OID_AUTO, drop_redirect, CTLFLAG_RW, 
	&drop_redirect, 0, "");

static int	log_redirect = 0;
SYSCTL_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_RW, 
	&log_redirect, 0, "");

#if ICMP_BANDLIM 
 
/*    
 * ICMP error-response bandwidth limiting sysctl.  If not enabled, sysctl
 *      variable content is -1 and read-only.
 */     
    
static int      icmplim = 250;
SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_RW,
	&icmplim, 0, "");
#else

static int      icmplim = -1;
SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_RD,
	&icmplim, 0, "");
	
#endif 

/*
 * ICMP broadcast echo sysctl
 */

static int	icmpbmcastecho = 1;
SYSCTL_INT(_net_inet_icmp, OID_AUTO, bmcastecho, CTLFLAG_RW,
	&icmpbmcastecho, 0, "");


#if ICMPPRINTFS
int	icmpprintfs = 0;
#endif

static void	icmp_reflect(struct mbuf *);
static void	icmp_send(struct mbuf *, struct mbuf *);
static int	ip_next_mtu(int, int);

extern	struct protosw inetsw[];

/*
 * Generate an error packet of type error
 * in response to bad packet ip.
 */
void
icmp_error(
	struct mbuf *n,
	int type,
	int code,
	n_long dest,
	struct ifnet *destifp)
{
	register struct ip *oip = mtod(n, struct ip *), *nip;
	register unsigned oiplen = IP_VHL_HL(oip->ip_vhl) << 2;
	register struct icmp *icp;
	register struct mbuf *m;
	unsigned icmplen;

#if ICMPPRINTFS
	if (icmpprintfs)
		printf("icmp_error(%p, %x, %d)\n", oip, type, code);
#endif
	if (type != ICMP_REDIRECT)
		icmpstat.icps_error++;
	/*
	 * Don't send error if not the first fragment of message.
	 * Don't error if the old packet protocol was ICMP
	 * error message, only known informational types.
	 */
	if (oip->ip_off &~ (IP_MF|IP_DF))
		goto freeit;
	if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT &&
	  n->m_len >= oiplen + ICMP_MINLEN &&
	  !ICMP_INFOTYPE(((struct icmp *)((caddr_t)oip + oiplen))->icmp_type)) {
		icmpstat.icps_oldicmp++;
		goto freeit;
	}
	/* Don't send error in response to a multicast or broadcast packet */
	if (n->m_flags & (M_BCAST|M_MCAST))
		goto freeit;
	/*
	 * First, formulate icmp message
	 */
	m = m_gethdr(M_DONTWAIT, MT_HEADER);
	if (m == NULL)
		goto freeit;

	if (n->m_flags & M_SKIP_FIREWALL) {
		/* set M_SKIP_FIREWALL to skip firewall check, since we're called from firewall */
		m->m_flags |= M_SKIP_FIREWALL;
	}

	icmplen = min(oiplen + 8, oip->ip_len);
	if (icmplen < sizeof(struct ip)) {
		printf("icmp_error: bad length\n");
		m_free(m);
		goto freeit;
	}
	m->m_len = icmplen + ICMP_MINLEN;
	MH_ALIGN(m, m->m_len);
	icp = mtod(m, struct icmp *);
	if ((u_int)type > ICMP_MAXTYPE)
		panic("icmp_error");
	icmpstat.icps_outhist[type]++;
	icp->icmp_type = type;
	if (type == ICMP_REDIRECT)
		icp->icmp_gwaddr.s_addr = dest;
	else {
		icp->icmp_void = 0;
		/*
		 * The following assignments assume an overlay with the
		 * zeroed icmp_void field.
		 */
		if (type == ICMP_PARAMPROB) {
			icp->icmp_pptr = code;
			code = 0;
		} else if (type == ICMP_UNREACH &&
			code == ICMP_UNREACH_NEEDFRAG && destifp) {
			icp->icmp_nextmtu = htons(destifp->if_mtu);
		}
	}

	icp->icmp_code = code;
	m_copydata(n, 0, icmplen, (caddr_t)&icp->icmp_ip);
	nip = &icp->icmp_ip;

	/*
	 * Convert fields to network representation.
	 */
	HTONS(nip->ip_len);
	HTONS(nip->ip_off);

	/*
	 * Now, copy old ip header (without options)
	 * in front of icmp message.
	 */
	if (m->m_data - sizeof(struct ip) < m->m_pktdat)
		panic("icmp len");
	m->m_data -= sizeof(struct ip);
	m->m_len += sizeof(struct ip);
	m->m_pkthdr.len = m->m_len;
	m->m_pkthdr.rcvif = n->m_pkthdr.rcvif;
	m->m_pkthdr.aux = NULL; /* for IPsec */
	nip = mtod(m, struct ip *);
	bcopy((caddr_t)oip, (caddr_t)nip, sizeof(struct ip));
	nip->ip_len = m->m_len;
	nip->ip_vhl = IP_VHL_BORING;
	nip->ip_p = IPPROTO_ICMP;
	nip->ip_tos = 0;
	icmp_reflect(m);

freeit:
	m_freem(n);
}

static struct sockaddr_in icmpsrc = { sizeof (struct sockaddr_in), AF_INET };
static struct sockaddr_in icmpdst = { sizeof (struct sockaddr_in), AF_INET };
static struct sockaddr_in icmpgw = { sizeof (struct sockaddr_in), AF_INET };

/*
 * Process a received ICMP message.
 */
void
icmp_input(m, hlen)
	register struct mbuf *m;
	int hlen;
{
	register struct icmp *icp;
	register struct ip *ip = mtod(m, struct ip *);
	int icmplen = ip->ip_len;
	register int i;
	struct in_ifaddr *ia;
	void (*ctlfunc)(int, struct sockaddr *, void *);
	int code;
	char ipv4str[MAX_IPv4_STR_LEN];

	/*
	 * Locate icmp structure in mbuf, and check
	 * that not corrupted and of at least minimum length.
	 */
#if ICMPPRINTFS
	if (icmpprintfs) {
		char buf[MAX_IPv4_STR_LEN];

		printf("icmp_input from %s to %s, len %d\n",
		       inet_ntop(AF_INET, &ip->ip_src, buf, sizeof(buf)),
		       inet_ntop(AF_INET, &ip->ip_dst, ipv4str, sizeof(ipv4str)),
		       icmplen);
	}
#endif
	if (icmplen < ICMP_MINLEN) {
		icmpstat.icps_tooshort++;
		goto freeit;
	}
	i = hlen + min(icmplen, ICMP_ADVLENMIN);
	if (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_data += hlen;
	icp = mtod(m, struct icmp *);
	if (in_cksum(m, icmplen)) {
		icmpstat.icps_checksum++;
		goto freeit;
	}
	m->m_len += hlen;
	m->m_data -= hlen;

#if defined(NFAITH) && 0 < NFAITH
	if (m->m_pkthdr.rcvif && m->m_pkthdr.rcvif->if_type == IFT_FAITH) {
		/*
		 * Deliver very specific ICMP type only.
		 */
		switch (icp->icmp_type) {
		case ICMP_UNREACH:
		case ICMP_TIMXCEED:
			break;
		default:
			goto freeit;
		}
	}
#endif

#if ICMPPRINTFS
	if (icmpprintfs)
		printf("icmp_input, type %d code %d\n", icp->icmp_type,
		    icp->icmp_code);
#endif

	/*
	 * Message type specific processing.
	 */
	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:
		switch (code) {
			case ICMP_UNREACH_NET:
			case ICMP_UNREACH_HOST:
			case ICMP_UNREACH_SRCFAIL:
			case ICMP_UNREACH_NET_UNKNOWN:
			case ICMP_UNREACH_HOST_UNKNOWN:
			case ICMP_UNREACH_ISOLATED:
			case ICMP_UNREACH_TOSNET:
			case ICMP_UNREACH_TOSHOST:
			case ICMP_UNREACH_HOST_PRECEDENCE:
			case ICMP_UNREACH_PRECEDENCE_CUTOFF:
				code = PRC_UNREACH_NET;
				break;

			case ICMP_UNREACH_NEEDFRAG:
				code = PRC_MSGSIZE;
				break;

			/*
			 * RFC 1122, Sections 3.2.2.1 and 4.2.3.9.
			 * Treat subcodes 2,3 as immediate RST
			 */
			case ICMP_UNREACH_PROTOCOL:
			case ICMP_UNREACH_PORT:
				code = PRC_UNREACH_PORT;
				break;

			case ICMP_UNREACH_NET_PROHIB:
			case ICMP_UNREACH_HOST_PROHIB:
			case ICMP_UNREACH_FILTER_PROHIB:
				code = PRC_UNREACH_ADMIN_PROHIB;
				break;

			default:
				goto badcode;
		}
		goto deliver;

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

	case ICMP_PARAMPROB:
		if (code > 1)
			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.
		 */
		if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
		    IP_VHL_HL(icp->icmp_ip.ip_vhl) < (sizeof(struct ip) >> 2)) {
			icmpstat.icps_badlen++;
			goto freeit;
		}
		NTOHS(icp->icmp_ip.ip_len);
		/* Discard ICMP's in response to multicast packets */
		if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr)))
			goto badcode;
#if ICMPPRINTFS
		if (icmpprintfs)
			printf("deliver to protocol %d\n", icp->icmp_ip.ip_p);
#endif
		icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
#if 1
		/*
		 * MTU discovery:
		 * If we got a needfrag and there is a host route to the
		 * original destination, and the MTU is not locked, then
		 * set the MTU in the route to the suggested new value
		 * (if given) and then notify as usual.  The ULPs will
		 * notice that the MTU has changed and adapt accordingly.
		 * If no new MTU was suggested, then we guess a new one
		 * less than the current value.  If the new MTU is 
		 * unreasonably small (defined by sysctl tcp_minmss), then
		 * we reset the MTU to the interface value and enable the
		 * lock bit, indicating that we are no longer doing MTU
		 * discovery.
		 */
		if (code == PRC_MSGSIZE) {
			struct rtentry *rt;
			int mtu;

			rt = rtalloc1((struct sockaddr *)&icmpsrc, 0,
				      RTF_CLONING | RTF_PRCLONING);
			if (rt && (rt->rt_flags & RTF_HOST)
			    && !(rt->rt_rmx.rmx_locks & RTV_MTU)) {
				mtu = ntohs(icp->icmp_nextmtu);
				if (!mtu)
					mtu = ip_next_mtu(rt->rt_rmx.rmx_mtu,
							  1);
#if DEBUG_MTUDISC
				printf("MTU for %s reduced to %d\n",
					   inet_ntop(AF_INET, &icmpsrc.sin_addr, ipv4str,
					   			 sizeof(ipv4str)),
					   mtu);
#endif
				if (mtu < max(296, (tcp_minmss + sizeof(struct tcpiphdr)))) {
					/* rt->rt_rmx.rmx_mtu =
						rt->rt_ifp->if_mtu; */
					rt->rt_rmx.rmx_locks |= RTV_MTU;
				} else if (rt->rt_rmx.rmx_mtu > mtu) {
					rt->rt_rmx.rmx_mtu = mtu;
				}
			}
			if (rt)
				rtfree(rt);
		}

#endif
		/*
		 * XXX if the packet contains [IPv4 AH TCP], we can't make a
		 * notification to TCP layer.
		 */
		ctlfunc = ip_protox[icp->icmp_ip.ip_p]->pr_ctlinput;
		if (ctlfunc)
			(*ctlfunc)(code, (struct sockaddr *)&icmpsrc,
				   (void *)&icp->icmp_ip);
		break;

	badcode:
		icmpstat.icps_badcode++;
		break;

	case ICMP_ECHO:
		if (!icmpbmcastecho
		    && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
			icmpstat.icps_bmcastecho++;
			break;
		}
		icp->icmp_type = ICMP_ECHOREPLY;
#if ICMP_BANDLIM
		if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0)
			goto freeit;
		else
#endif
			goto reflect;

	case ICMP_TSTAMP:

		if (icmptimestamp == 0)
			break;

		if (!icmpbmcastecho
		    && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
			icmpstat.icps_bmcasttstamp++;
			break;
		}
		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! */
#if ICMP_BANDLIM
		if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0)
			goto freeit;
		else
#endif
			goto reflect;

	case ICMP_MASKREQ:
#define	satosin(sa)	((struct sockaddr_in *)(sa))
		if (icmpmaskrepl == 0)
			break;
		/*
		 * We are not able to respond with all ones broadcast
		 * unless we receive it over a point-to-point interface.
		 */
		if (icmplen < ICMP_MASKLEN)
			break;
		switch (ip->ip_dst.s_addr) {

		case INADDR_BROADCAST:
		case INADDR_ANY:
			icmpdst.sin_addr = ip->ip_src;
			break;

		default:
			icmpdst.sin_addr = ip->ip_dst;
		}
		ia = (struct in_ifaddr *)ifaof_ifpforaddr(
			    (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif);
		if (ia == 0)
			break;
		if (ia->ia_ifp == 0) {
			ifafree(&ia->ia_ifa);
			ia = 0;
			break;
		}
		icp->icmp_type = ICMP_MASKREPLY;
		icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr;
		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;
		}
		ifafree(&ia->ia_ifa);
reflect:
		ip->ip_len += hlen;	/* since ip_input deducts this */
		icmpstat.icps_reflect++;
		icmpstat.icps_outhist[icp->icmp_type]++;
		icmp_reflect(m);
		return;

	case ICMP_REDIRECT:
		if (log_redirect) {
			u_long src, dst, gw;

			src = ntohl(ip->ip_src.s_addr);
			dst = ntohl(icp->icmp_ip.ip_dst.s_addr);
			gw = ntohl(icp->icmp_gwaddr.s_addr);
			printf("icmp redirect from %d.%d.%d.%d: "
			       "%d.%d.%d.%d => %d.%d.%d.%d\n",
			       (int)(src >> 24), (int)((src >> 16) & 0xff),
			       (int)((src >> 8) & 0xff), (int)(src & 0xff),
			       (int)(dst >> 24), (int)((dst >> 16) & 0xff),
			       (int)((dst >> 8) & 0xff), (int)(dst & 0xff),
			       (int)(gw >> 24), (int)((gw >> 16) & 0xff),
			       (int)((gw >> 8) & 0xff), (int)(gw & 0xff));
		}
		if (drop_redirect)
			break;
		if (code > 3)
			goto badcode;
		if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
		    IP_VHL_HL(icp->icmp_ip.ip_vhl) < (sizeof(struct ip) >> 2)) {
			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	ICMPPRINTFS
		if (icmpprintfs) {
			char buf[MAX_IPv4_STR_LEN];

			printf("redirect dst %s to %s\n",
			       inet_ntop(AF_INET, &icp->icmp_ip.ip_dst, buf, sizeof(buf)),
			       inet_ntop(AF_INET, &icp->icmp_gwaddr, ipv4str,
			       			 sizeof(ipv4str)));
		}
#endif
		icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
		rtredirect((struct sockaddr *)&icmpsrc,
		  (struct sockaddr *)&icmpdst,
		  (struct sockaddr *)0, RTF_GATEWAY | RTF_HOST,
		  (struct sockaddr *)&icmpgw, (struct rtentry **)0);
		pfctlinput(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc);
#if IPSEC
		key_sa_routechange((struct sockaddr *)&icmpsrc);
#endif
		break;

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

raw:
	rip_input(m, hlen);
	return;

freeit:
	m_freem(m);
}

/*
 * Reflect the ip packet back to the source
 */
static void
icmp_reflect(m)
	struct mbuf *m;
{
	register struct ip *ip = mtod(m, struct ip *);
	register struct in_ifaddr *ia;
	struct in_addr t;
	struct mbuf *opts = 0;
	int optlen = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof(struct ip);

	if (!in_canforward(ip->ip_src) &&
	    ((ntohl(ip->ip_src.s_addr) & IN_CLASSA_NET) !=
	     (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))) {
		m_freem(m);	/* Bad return address */
		goto done;	/* Ip_output() will check for broadcast */
	}
	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.
	 */
	lck_mtx_lock(rt_mtx);
	for (ia = in_ifaddrhead.tqh_first; ia; ia = ia->ia_link.tqe_next) {
		if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr)
			break;
		if (ia->ia_ifp && (ia->ia_ifp->if_flags & IFF_BROADCAST) &&
		    t.s_addr == satosin(&ia->ia_broadaddr)->sin_addr.s_addr)
			break;
	}
	if (ia)
		ifaref(&ia->ia_ifa);
	icmpdst.sin_addr = t;
	if ((ia == (struct in_ifaddr *)0) && m->m_pkthdr.rcvif)
		ia = (struct in_ifaddr *)ifaof_ifpforaddr(
			(struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif);
	/*
	 * The following happens if the packet was not addressed to us,
	 * and was received on an interface with no IP address.
	 */
	if (ia == (struct in_ifaddr *)0) {
		ia = in_ifaddrhead.tqh_first;
		if (ia == (struct in_ifaddr *)0) {/* no address yet, bail out */
			m_freem(m);
			lck_mtx_unlock(rt_mtx);
			goto done;
		}
		ifaref(&ia->ia_ifa);
	}
	lck_mtx_unlock(rt_mtx);
	t = IA_SIN(ia)->sin_addr;
	ip->ip_src = t;
	ip->ip_ttl = ip_defttl;
	ifafree(&ia->ia_ifa);
	ia = NULL;

	if (optlen > 0) {
		register u_char *cp;
		int opt, cnt;
		u_int len;

		/*
		 * Retrieve any source routing from the incoming packet;
		 * add on any record-route or timestamp options.
		 */
		cp = (u_char *) (ip + 1);
		if ((opts = ip_srcroute()) == 0 &&
		    (opts = m_gethdr(M_DONTWAIT, MT_HEADER))) {
			opts->m_len = sizeof(struct in_addr);
			mtod(opts, struct in_addr *)->s_addr = 0;
		}
		if (opts) {
#if ICMPPRINTFS
		    if (icmpprintfs)
			    printf("icmp_reflect optlen %d rt %d => ",
				optlen, opts->m_len);
#endif
		    for (cnt = optlen; cnt > 0; cnt -= len, cp += len) {
			    opt = cp[IPOPT_OPTVAL];
			    if (opt == IPOPT_EOL)
				    break;
			    if (opt == IPOPT_NOP)
				    len = 1;
			    else {
				    if (cnt < IPOPT_OLEN + sizeof(*cp))
					    break;
				    len = cp[IPOPT_OLEN];
				    if (len < IPOPT_OLEN + sizeof(*cp) ||
				        len > cnt)
					    break;
			    }
			    /*
			     * Should check for overflow, but it "can't happen"
			     */
			    if (opt == IPOPT_RR || opt == IPOPT_TS ||
				opt == IPOPT_SECURITY) {
				    bcopy((caddr_t)cp,
					mtod(opts, caddr_t) + opts->m_len, len);
				    opts->m_len += len;
			    }
		    }
		    /* Terminate & pad, if necessary */
		    cnt = opts->m_len % 4;
		    if (cnt) {
			    for (; cnt < 4; cnt++) {
				    *(mtod(opts, caddr_t) + opts->m_len) =
					IPOPT_EOL;
				    opts->m_len++;
			    }
		    }
#if ICMPPRINTFS
		    if (icmpprintfs)
			    printf("%d\n", opts->m_len);
#endif
		}
		/*
		 * Now strip out original options by copying rest of first
		 * mbuf's data back, and adjust the IP length.
		 */
		ip->ip_len -= optlen;
		ip->ip_vhl = IP_VHL_BORING;
		m->m_len -= optlen;
		if (m->m_flags & M_PKTHDR)
			m->m_pkthdr.len -= optlen;
		optlen += sizeof(struct ip);
		bcopy((caddr_t)ip + optlen, (caddr_t)(ip + 1),
			 (unsigned)(m->m_len - sizeof(struct ip)));
	}
	m->m_flags &= ~(M_BCAST|M_MCAST);
	icmp_send(m, opts);
done:
	if (opts)
		(void)m_free(opts);
}

/*
 * Send an icmp packet back to the ip level,
 * after supplying a checksum.
 */
static void
icmp_send(m, opts)
	register struct mbuf *m;
	struct mbuf *opts;
{
	register struct ip *ip = mtod(m, struct ip *);
	register int hlen;
	register struct icmp *icp;
	struct route ro;
	char ipv4str[MAX_IPv4_STR_LEN];

	hlen = IP_VHL_HL(ip->ip_vhl) << 2;
	m->m_data += 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_data -= hlen;
	m->m_len += hlen;
	m->m_pkthdr.rcvif = 0;
	m->m_pkthdr.aux = NULL;
	m->m_pkthdr.csum_data = 0;
	m->m_pkthdr.csum_flags = 0;
#if ICMPPRINTFS
	if (icmpprintfs) {
		char buf[MAX_IPv4_STR_LEN];

		printf("icmp_send dst %s src %s\n",
		       inet_ntop(AF_INET, &ip->ip_dst, buf, sizeof(buf)),
		       inet_ntop(AF_INET, &ip->ip_src, ipv4str, sizeof(ipv4str)));
	}
#endif
	bzero(&ro, sizeof ro);
	(void) ip_output(m, opts, &ro, 0, NULL);
	if (ro.ro_rt)
		rtfree(ro.ro_rt);
}

n_time
iptime()
{
	struct timeval atv;
	u_long t;

	microtime(&atv);
	t = (atv.tv_sec % (24*60*60)) * 1000 + atv.tv_usec / 1000;
	return (htonl(t));
}

#if 1
/*
 * Return the next larger or smaller MTU plateau (table from RFC 1191)
 * given current value MTU.  If DIR is less than zero, a larger plateau
 * is returned; otherwise, a smaller value is returned.
 */
static int
ip_next_mtu(mtu, dir)
	int mtu;
	int dir;
{
	static int mtutab[] = {
		65535, 32000, 17914, 8166, 4352, 2002, 1492, 1006, 508, 296,
		68, 0
	};
	int i;

	for (i = 0; i < (sizeof mtutab) / (sizeof mtutab[0]); i++) {
		if (mtu >= mtutab[i])
			break;
	}

	if (dir < 0) {
		if (i == 0) {
			return 0;
		} else {
			return mtutab[i - 1];
		}
	} else {
		if (mtutab[i] == 0) {
			return 0;
		} else if(mtu > mtutab[i]) {
			return mtutab[i];
		} else {
			return mtutab[i + 1];
		}
	}
}
#endif

#if ICMP_BANDLIM

/*
 * badport_bandlim() - check for ICMP bandwidth limit
 *
 *	Return 0 if it is ok to send an ICMP error response, -1 if we have
 *	hit our bandwidth limit and it is not ok.  
 *
 *	If icmplim is <= 0, the feature is disabled and 0 is returned.
 *
 *	For now we separate the TCP and UDP subsystems w/ different 'which'
 *	values.  We may eventually remove this separation (and simplify the
 *	code further).
 *
 *	Note that the printing of the error message is delayed so we can
 *	properly print the icmp error rate that the system was trying to do
 *	(i.e. 22000/100 pps, etc...).  This can cause long delays in printing
 *	the 'final' error, but it doesn't make sense to solve the printing 
 *	delay with more complex code.
 */

int
badport_bandlim(int which)
{
	static struct timeval lticks[BANDLIM_MAX + 1];
	static int lpackets[BANDLIM_MAX + 1];
	struct timeval time;
	int secs;

	const char *bandlimittype[] = {
		"Limiting icmp unreach response",
		"Limiting icmp ping response",
		"Limiting icmp tstamp response",
		"Limiting closed port RST response",
		"Limiting open port RST response"
		};

	/*
	 * Return ok status if feature disabled or argument out of
	 * ranage.
	 */

	if (icmplim <= 0 || which > BANDLIM_MAX || which < 0)
		return(0);

	getmicrouptime(&time);

 	secs = time.tv_sec - lticks[which].tv_sec ;
			
	/*
	 * reset stats when cumulative delta exceeds one second.
	 */

	if ((secs > 1) || (secs == 1 && (lticks[which].tv_usec > time.tv_usec))) { 
		if (lpackets[which] > icmplim) {
			printf("%s from %d to %d packets per second\n",
				bandlimittype[which],
				lpackets[which],
				icmplim
			);
		}
		lticks[which].tv_sec = time.tv_sec;
		lticks[which].tv_usec = time.tv_usec;
		lpackets[which] = 0;
	}

	/*
	 * bump packet count
	 */

	if (++lpackets[which] > icmplim) {
		return(-1);
	}
	return(0);
}

#endif

#if __APPLE__

/*
 * Non-privileged ICMP socket operations
 * - send ICMP echo request
 * - all ICMP
 * - limited socket options
 */

#include <netinet/ip_icmp.h>
#include <netinet/in_pcb.h>

extern struct domain inetdomain;
extern u_long rip_sendspace;
extern u_long rip_recvspace;
extern struct inpcbinfo ripcbinfo;

int rip_abort(struct socket *);
int rip_bind(struct socket *, struct sockaddr *, struct proc *);
int rip_connect(struct socket *, struct sockaddr *, struct proc *);
int rip_detach(struct socket *);
int rip_disconnect(struct socket *);
int rip_shutdown(struct socket *);

__private_extern__ int icmp_dgram_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam, struct mbuf *control, struct proc *p);
__private_extern__ int icmp_dgram_attach(struct socket *so, int proto, struct proc *p);
__private_extern__ int icmp_dgram_ctloutput(struct socket *so, struct sockopt *sopt);

__private_extern__ struct pr_usrreqs icmp_dgram_usrreqs = {
        rip_abort, pru_accept_notsupp, icmp_dgram_attach, rip_bind, rip_connect,
        pru_connect2_notsupp, in_control, rip_detach, rip_disconnect,
        pru_listen_notsupp, in_setpeeraddr, pru_rcvd_notsupp,
        pru_rcvoob_notsupp, icmp_dgram_send, pru_sense_null, rip_shutdown,
        in_setsockaddr, sosend, soreceive, pru_sopoll_notsupp
};

/* Like rip_attach but without root privilege enforcement */
__private_extern__ int
icmp_dgram_attach(struct socket *so, int proto, struct proc *p)
{
        struct inpcb *inp;
        int error, s;

        inp = sotoinpcb(so);
        if (inp)
                panic("icmp_dgram_attach");

        error = soreserve(so, rip_sendspace, rip_recvspace);
        if (error)
                return error;
        s = splnet();
        error = in_pcballoc(so, &ripcbinfo, p);
        splx(s);
        if (error)
                return error;
        inp = (struct inpcb *)so->so_pcb;       
        inp->inp_vflag |= INP_IPV4;
        inp->inp_ip_p = IPPROTO_ICMP;
        inp->inp_ip_ttl = ip_defttl;
        return 0;
}

/*
 * Raw IP socket option processing.
 */
__private_extern__ int
icmp_dgram_ctloutput(struct socket *so, struct sockopt *sopt)
{
	struct	inpcb *inp = sotoinpcb(so);
	int	error, optval;

	if (sopt->sopt_level != IPPROTO_IP)
		return (EINVAL);

	switch (sopt->sopt_name) {
		case IP_OPTIONS:
		case IP_HDRINCL:
		case IP_TOS:
		case IP_TTL:
		case IP_RECVOPTS:
		case IP_RECVRETOPTS:
		case IP_RECVDSTADDR:
		case IP_RETOPTS:
		case IP_MULTICAST_IF:
		case IP_MULTICAST_TTL:
		case IP_MULTICAST_LOOP:
		case IP_ADD_MEMBERSHIP:
		case IP_DROP_MEMBERSHIP:
		case IP_MULTICAST_VIF:
		case IP_PORTRANGE:
		case IP_RECVIF:
		case IP_IPSEC_POLICY:
#if defined(NFAITH) && NFAITH > 0
		case IP_FAITH:
#endif
		case IP_STRIPHDR:
		case IP_RECVTTL:
			error = rip_ctloutput(so, sopt);
			break;
		
		default:
			error = EINVAL;
			break;
	}

	return (error);
}

__private_extern__ int
icmp_dgram_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
         struct mbuf *control, struct proc *p)
{
	struct ip *ip;
	struct inpcb *inp = sotoinpcb(so);
	int hlen;
	struct icmp *icp;
        struct in_ifaddr *ia = NULL;
	int icmplen;

	if ((inp->inp_flags & INP_HDRINCL) != 0) {
		/*
		 * This is not raw IP, we liberal only for fields TOS, id and TTL 
		 */
		ip = mtod(m, struct ip *);

		hlen = IP_VHL_HL(ip->ip_vhl) << 2;
		/* Some sanity checks */
		if (m->m_pkthdr.len < hlen + ICMP_MINLEN) {
			goto bad;
		}
		/* Only IPv4 */
		if (IP_VHL_V(ip->ip_vhl) != 4)
			goto bad;
		if (hlen < 20 || hlen > 40 || ip->ip_len != m->m_pkthdr.len)
			goto bad;
		/* Bogus fragments can tie up peer resources */ 
		if (ip->ip_off != 0)
			goto bad;
		/* Allow only ICMP even for user provided IP header */
		if (ip->ip_p != IPPROTO_ICMP)
			goto bad;
		/* To prevent spoofing, specified source address must be one of ours */
		if (ip->ip_src.s_addr != INADDR_ANY) {
			socket_unlock(so, 0);
			lck_mtx_lock(rt_mtx);
			if (TAILQ_EMPTY(&in_ifaddrhead)) {
				lck_mtx_unlock(rt_mtx);
				socket_lock(so, 0);
				goto bad;
			}
			TAILQ_FOREACH(ia, &in_ifaddrhead, ia_link) {
				if (IA_SIN(ia)->sin_addr.s_addr == ip->ip_src.s_addr) {
					lck_mtx_unlock(rt_mtx);
					socket_lock(so, 0);
					goto ours;
				}
			}
			lck_mtx_unlock(rt_mtx);
			socket_lock(so, 0);
			goto bad;
		}
ours:
		/* Do not trust we got a valid checksum */
		ip->ip_sum = 0;
		
		icp = (struct icmp *)(((char *)m->m_data) + hlen);
		icmplen = m->m_pkthdr.len - hlen;
	} else {
		if ((icmplen = m->m_pkthdr.len) < ICMP_MINLEN) {
			goto bad;
		}
		icp = mtod(m, struct icmp *);
	}
	/*
	 * Allow only to send request types with code 0
	 */
	if (icp->icmp_code != 0)
		goto bad;
	switch (icp->icmp_type) {
		case ICMP_ECHO:
			break;
		case ICMP_TSTAMP:
			if (icmplen != 20)
				goto bad;
			break;
		case ICMP_MASKREQ:
			if (icmplen != 12)
				goto bad;
			break;
		default:
			goto bad;
	}
	return rip_send(so, flags, m, nam, control, p);
bad:
	m_freem(m);
	return EINVAL;
}

#endif /* __APPLE__ */