/*
 * 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. 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
 * $FreeBSD: src/sys/netinet/ip_icmp.c,v 1.39.2.19 2003/01/24 05:11:34 sam Exp $
 */

#include "opt_icmpprintfs.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h> /* for M_NOWAIT */
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketops.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/in_cksum.h>

#include <machine/stdarg.h>

#include <net/if.h>
#include <net/if_types.h>
#include <net/netisr2.h>
#include <net/netmsg2.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>

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

struct icmpstat icmpstat;
SYSCTL_STRUCT(_net_inet_icmp, ICMPCTL_STATS, stats, CTLFLAG_RW,
        &icmpstat, icmpstat, "ICMP statistics");

static int      icmpmaskrepl = 0;
SYSCTL_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_RW,
        &icmpmaskrepl, 0, "Allow replies to netmask requests");

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

static int      log_redirect = 0;
SYSCTL_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_RW,
        &log_redirect, 0, "Enable output about ICMP redirects");

static int      discard_sourcequench = 1;
SYSCTL_INT(_net_inet_icmp, OID_AUTO, discard_sourcequench, CTLFLAG_RW,
        &discard_sourcequench, 0, "Discard ICMP Source Quench");

#ifdef ICMP_BANDLIM

/*
 * ICMP error-response bandwidth limiting sysctl.  If not enabled, sysctl
 *      variable content is -1 and read-only.
 */

static int      icmplim = 200;
SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_RW,
        &icmplim, 0, "ICMP bandwidth limit");
#else

static int      icmplim = -1;
SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_RD,
        &icmplim, 0, "ICMP bandwidth limit");

#endif

static int      icmplim_output = 0;
SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_output, CTLFLAG_RW,
        &icmplim_output, 0, "Enable output about ICMP bandwidth limits");

/*
 * ICMP broadcast echo sysctl
 */

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

static char     icmp_reply_src[IFNAMSIZ];
SYSCTL_STRING(_net_inet_icmp, OID_AUTO, reply_src, CTLFLAG_RW,
        icmp_reply_src, IFNAMSIZ, "icmp reply source for non-local packets.");

static int      icmp_rfi;
SYSCTL_INT(_net_inet_icmp, OID_AUTO, reply_from_interface, CTLFLAG_RW,
        &icmp_rfi, 0, "ICMP reply from incoming interface for "
        "non-local packets");

#ifdef ICMPPRINTFS
static int      icmpprintfs = 0;
SYSCTL_INT(_net_inet_icmp, OID_AUTO, debug_prints, CTLFLAG_RW,
        &icmpprintfs, 0, "extra ICMP debug prints");
#endif

static void     icmp_reflect (struct mbuf *);
static void     icmp_send (struct mbuf *, struct mbuf *, struct route *);

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, int destmtu)
{
        struct ip *oip = mtod(n, struct ip *), *nip;
        unsigned oiplen = IP_VHL_HL(oip->ip_vhl) << 2;
        struct icmp *icp;
        struct mbuf *m;
        unsigned icmplen;

#ifdef ICMPPRINTFS
        if (icmpprintfs)
                kprintf("icmp_error(%p, %d, %d)\n", oip, type, code);
#endif
        if (type != ICMP_REDIRECT)
                icmpstat.icps_error++;
        /*
         * Don't send error if the original packet was encrypted.
         * 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 (n->m_flags & M_DECRYPTED)
                goto freeit;
        if (oip->ip_off & htons(~(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_NOWAIT, MT_HEADER);
        if (m == NULL)
                goto freeit;
        icmplen = min(oiplen + 8, ntohs(oip->ip_len));
        if (icmplen < sizeof(struct ip))
                panic("icmp_error: bad length");
        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 && destmtu) {
                        icp->icmp_nextmtu = htons(destmtu);
                }
        }

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

        /*
         * 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;
        nip = mtod(m, struct ip *);
        bcopy(oip, nip, sizeof(struct ip));
        nip->ip_len = htons(m->m_len);
        nip->ip_vhl = IP_VHL_BORING;
        nip->ip_p = IPPROTO_ICMP;
        nip->ip_tos = 0;
        m->m_pkthdr.fw_flags |= n->m_pkthdr.fw_flags & FW_MBUF_GENERATED;
        icmp_reflect(m);

freeit:
        m_freem(n);
}

static void
icmp_ctlinput_done_handler(netmsg_t nmsg)
{
        struct netmsg_ctlinput *msg = (struct netmsg_ctlinput *)nmsg;
        struct mbuf *m = msg->m;
        int hlen = msg->hlen;

        rip_input(&m, &hlen, msg->proto);
}

static void
icmp_ctlinput_done(struct mbuf *m)
{
        struct netmsg_ctlinput *msg = &m->m_hdr.mh_ctlmsg;

        netmsg_init(&msg->base, NULL, &netisr_apanic_rport, 0,
            icmp_ctlinput_done_handler);
        lwkt_sendmsg(netisr_cpuport(0), &msg->base.lmsg);
}

static void
icmp_mtudisc(struct mbuf *m, int hlen)
{
        struct sockaddr_in icmpsrc = { sizeof(struct sockaddr_in), AF_INET };
        struct rtentry *rt;
        struct icmp *icp;

        KASSERT(curthread->td_type == TD_TYPE_NETISR, ("not in netisr"));

        icp = mtodoff(m, struct icmp *, hlen);
        icmpsrc.sin_addr = icp->icmp_ip.ip_dst;

        /*
         * 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 (arbitrarily set at 296), then we reset the MTU to the
         * interface value and enable the lock bit, indicating that we are
         * no longer doing MTU discovery.
         */
        rt = rtpurelookup((struct sockaddr *)&icmpsrc);
        if (rt != NULL && (rt->rt_flags & RTF_HOST) &&
            !(rt->rt_rmx.rmx_locks & RTV_MTU)) {
#ifdef DEBUG_MTUDISC
                char src_buf[INET_ADDRSTRLEN];
#endif
                int mtu;

                mtu = ntohs(icp->icmp_nextmtu);
                if (!mtu)
                        mtu = ip_next_mtu(rt->rt_rmx.rmx_mtu, 1);
#ifdef DEBUG_MTUDISC
                kprintf("MTU for %s reduced to %d\n",
                    inet_ntop(AF_INET, &icmpsrc.sin_addr,
                        src_buf, INET_ADDRSTRLEN), mtu);
#endif
                if (mtu < 296) {
                        /* 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 != NULL)
                --rt->rt_refcnt;

        /*
         * XXX if the packet contains [IPv4 AH TCP], we can't make a
         * notification to TCP layer.
         */
        so_pr_ctlinput_direct(&inetsw[ip_protox[icp->icmp_ip.ip_p]],
            PRC_MSGSIZE, (struct sockaddr *)&icmpsrc, &icp->icmp_ip);
}

static void
icmp_mtudisc_handler(netmsg_t nmsg)
{
        struct netmsg_ctlinput *msg = (struct netmsg_ctlinput *)nmsg;
        int nextcpu;

        ASSERT_NETISR_NCPUS(mycpuid);

        icmp_mtudisc(msg->m, msg->hlen);

        nextcpu = mycpuid + 1;
        if (nextcpu < netisr_ncpus)
                lwkt_forwardmsg(netisr_cpuport(nextcpu), &msg->base.lmsg);
        else
                icmp_ctlinput_done(msg->m);
}

static boolean_t
icmp_mtudisc_start(struct mbuf *m, int hlen, int proto)
{
        struct netmsg_ctlinput *msg;

        ASSERT_NETISR0;

        icmp_mtudisc(m, hlen);

        if (netisr_ncpus == 1) {
                /* There is only one netisr; done */
                return FALSE;
        }

        msg = &m->m_hdr.mh_ctlmsg;
        netmsg_init(&msg->base, NULL, &netisr_apanic_rport, 0,
            icmp_mtudisc_handler);
        msg->m = m;
        msg->cmd = PRC_MSGSIZE;
        msg->hlen = hlen;
        msg->proto = proto;

        lwkt_sendmsg(netisr_cpuport(1), &msg->base.lmsg);
        return TRUE;
}

static void
icmp_ctlinput(struct mbuf *m, int cmd, int hlen)
{
        struct sockaddr_in icmpsrc = { sizeof(struct sockaddr_in), AF_INET };
        struct icmp *icp;

        KASSERT(curthread->td_type == TD_TYPE_NETISR, ("not in netisr"));

        icp = mtodoff(m, struct icmp *, hlen);
        icmpsrc.sin_addr = icp->icmp_ip.ip_dst;

        /*
         * XXX if the packet contains [IPv4 AH TCP], we can't make a
         * notification to TCP layer.
         */
        so_pr_ctlinput_direct(&inetsw[ip_protox[icp->icmp_ip.ip_p]],
            cmd, (struct sockaddr *)&icmpsrc, &icp->icmp_ip);
}

static void
icmp_ctlinput_handler(netmsg_t nmsg)
{
        struct netmsg_ctlinput *msg = (struct netmsg_ctlinput *)nmsg;

        ASSERT_NETISR_NCPUS(mycpuid);

        icmp_ctlinput(msg->m, msg->cmd, msg->hlen);
        icmp_ctlinput_done(msg->m);
}

static void
icmp_ctlinput_start(struct mbuf *m, struct lwkt_port *port,
    int cmd, int hlen, int proto)
{
        struct netmsg_ctlinput *msg;

        KASSERT(&curthread->td_msgport != port,
            ("send icmp ctlinput to the current netisr"));

        msg = &m->m_hdr.mh_ctlmsg;
        netmsg_init(&msg->base, NULL, &netisr_apanic_rport, 0,
            icmp_ctlinput_handler);
        msg->m = m;
        msg->cmd = cmd;
        msg->hlen = hlen;
        msg->proto = proto;

        lwkt_sendmsg(port, &msg->base.lmsg);
}

static void
icmp_ctlinput_global_handler(netmsg_t nmsg)
{
        struct netmsg_ctlinput *msg = (struct netmsg_ctlinput *)nmsg;
        int nextcpu;

        ASSERT_NETISR_NCPUS(mycpuid);

        icmp_ctlinput(msg->m, msg->cmd, msg->hlen);

        nextcpu = mycpuid + 1;
        if (nextcpu < netisr_ncpus)
                lwkt_forwardmsg(netisr_cpuport(nextcpu), &msg->base.lmsg);
        else
                icmp_ctlinput_done(msg->m);
}

static void
icmp_ctlinput_global_start(struct mbuf *m, int cmd, int hlen, int proto)
{
        struct netmsg_ctlinput *msg;

        ASSERT_NETISR0;
        KASSERT(netisr_ncpus > 1, ("there is only 1 netisr cpu"));

        icmp_ctlinput(m, cmd, hlen);

        msg = &m->m_hdr.mh_ctlmsg;
        netmsg_init(&msg->base, NULL, &netisr_apanic_rport, 0,
            icmp_ctlinput_global_handler);
        msg->m = m;
        msg->cmd = cmd;
        msg->hlen = hlen;
        msg->proto = proto;

        lwkt_sendmsg(netisr_cpuport(1), &msg->base.lmsg);
}

#define ICMP_RTREDIRECT_FLAGS   (RTF_GATEWAY | RTF_HOST)

static void
icmp_redirect(struct mbuf *m, int hlen, boolean_t prt)
{
        struct sockaddr_in icmpsrc = { sizeof(struct sockaddr_in), AF_INET };
        struct sockaddr_in icmpdst = { sizeof(struct sockaddr_in), AF_INET };
        struct sockaddr_in icmpgw = { sizeof(struct sockaddr_in), AF_INET };
        struct icmp *icp;
        struct ip *ip;

        KASSERT(curthread->td_type == TD_TYPE_NETISR, ("not in netisr"));

        ip = mtod(m, struct ip *);
        icp = mtodoff(m, struct icmp *, hlen);

        /*
         * 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).
         */
#ifdef ICMPPRINTFS
        if (icmpprintfs && prt) {
                char dst_buf[INET_ADDRSTRLEN], gw_buf[INET_ADDRSTRLEN];

                kprintf("redirect dst %s to %s\n",
                    inet_ntop(AF_INET, &icp->icmp_ip.ip_dst,
                        dst_buf, INET_ADDRSTRLEN),
                    inet_ntop(AF_INET, &icp->icmp_gwaddr,
                        gw_buf, INET_ADDRSTRLEN));
        }
#endif
        icmpgw.sin_addr = ip->ip_src;
        icmpdst.sin_addr = icp->icmp_gwaddr;
        icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
        rtredirect_oncpu((struct sockaddr *)&icmpsrc,
            (struct sockaddr *)&icmpdst, NULL, ICMP_RTREDIRECT_FLAGS,
            (struct sockaddr *)&icmpgw);
        kpfctlinput_direct(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc);
}

static void
icmp_redirect_done_handler(netmsg_t nmsg)
{
        struct netmsg_ctlinput *msg = (struct netmsg_ctlinput *)nmsg;
        struct mbuf *m = msg->m;
        int hlen = msg->hlen;

        rip_input(&m, &hlen, msg->proto);
}

static void
icmp_redirect_done(struct mbuf *m, int hlen, boolean_t dispatch_rip)
{
        struct rt_addrinfo rtinfo;
        struct sockaddr_in icmpsrc = { sizeof(struct sockaddr_in), AF_INET };
        struct sockaddr_in icmpdst = { sizeof(struct sockaddr_in), AF_INET };
        struct sockaddr_in icmpgw = { sizeof(struct sockaddr_in), AF_INET };
        struct icmp *icp;
        struct ip *ip;

        ip = mtod(m, struct ip *);
        icp = mtodoff(m, struct icmp *, hlen);

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

        bzero(&rtinfo, sizeof(struct rt_addrinfo));
        rtinfo.rti_info[RTAX_DST] = (struct sockaddr *)&icmpsrc;
        rtinfo.rti_info[RTAX_GATEWAY] = (struct sockaddr *)&icmpdst;
        rtinfo.rti_info[RTAX_NETMASK] = NULL;
        rtinfo.rti_info[RTAX_AUTHOR] = (struct sockaddr *)&icmpgw;
        rt_missmsg(RTM_REDIRECT, &rtinfo, ICMP_RTREDIRECT_FLAGS, 0);

        if (dispatch_rip) {
                struct netmsg_ctlinput *msg = &m->m_hdr.mh_ctlmsg;

                netmsg_init(&msg->base, NULL, &netisr_apanic_rport, 0,
                    icmp_redirect_done_handler);
                lwkt_sendmsg(netisr_cpuport(0), &msg->base.lmsg);
        }
}

static void
icmp_redirect_handler(netmsg_t nmsg)
{
        struct netmsg_ctlinput *msg = (struct netmsg_ctlinput *)nmsg;
        int nextcpu;

        ASSERT_NETISR_NCPUS(mycpuid);

        icmp_redirect(msg->m, msg->hlen, FALSE);

        nextcpu = mycpuid + 1;
        if (nextcpu < netisr_ncpus)
                lwkt_forwardmsg(netisr_cpuport(nextcpu), &msg->base.lmsg);
        else
                icmp_redirect_done(msg->m, msg->hlen, TRUE);
}

static boolean_t
icmp_redirect_start(struct mbuf *m, int hlen, int proto)
{
        struct netmsg_ctlinput *msg;

        ASSERT_NETISR0;

        icmp_redirect(m, hlen, TRUE);

        if (netisr_ncpus == 1) {
                /* There is only one netisr; done */
                icmp_redirect_done(m, hlen, FALSE);
                return FALSE;
        }

        msg = &m->m_hdr.mh_ctlmsg;
        netmsg_init(&msg->base, NULL, &netisr_apanic_rport, 0,
            icmp_redirect_handler);
        msg->m = m;
        msg->cmd = PRC_REDIRECT_HOST;
        msg->hlen = hlen;
        msg->proto = proto;

        lwkt_sendmsg(netisr_cpuport(1), &msg->base.lmsg);
        return TRUE;
}

/*
 * Process a received ICMP message.
 */
int
icmp_input(struct mbuf **mp, int *offp, int proto)
{
        struct sockaddr_in icmpsrc = { sizeof(struct sockaddr_in), AF_INET };
        struct sockaddr_in icmpdst = { sizeof(struct sockaddr_in), AF_INET };
        struct icmp *icp;
        struct in_ifaddr *ia;
        struct mbuf *m = *mp;
        struct ip *ip;
        int icmplen;
        int i, hlen;
        int code;

        ASSERT_NETISR0;

        *mp = NULL;
        hlen = *offp;
        ip = mtod(m, struct ip *);
        icmplen = ntohs(ip->ip_len) - hlen;

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

                kprintf("icmp_input from %s to %s, len %d\n",
                    inet_ntop(AF_INET, &ip->ip_src, src_buf, INET_ADDRSTRLEN),
                    inet_ntop(AF_INET, &ip->ip_dst, dst_buf, INET_ADDRSTRLEN),
                    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)) == NULL)  {
                icmpstat.icps_tooshort++;
                return(IPPROTO_DONE);
        }
        ip = mtod(m, struct ip *);

        if (in_cksum_skip(m, hlen + icmplen, hlen)) {
                icmpstat.icps_checksum++;
                goto freeit;
        }
        icp = (struct icmp *)((caddr_t)ip + hlen);

#ifdef ICMPPRINTFS
        if (icmpprintfs)
                kprintf("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;
                if (discard_sourcequench)
                        break;
                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;
                }
                /* Discard ICMP's in response to multicast packets */
                if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr)))
                        goto badcode;
#ifdef ICMPPRINTFS
                if (icmpprintfs)
                        kprintf("deliver to protocol %d\n", icp->icmp_ip.ip_p);
#endif
                icmpsrc.sin_addr = icp->icmp_ip.ip_dst;

                /*
                 * MTU discovery
                 */
                if (code == PRC_MSGSIZE) {
                        /* Run MTU discovery in all netisrs */
                        if (icmp_mtudisc_start(m, hlen, proto)) {
                                /* Forwarded; done */
                                return IPPROTO_DONE;
                        }
                        /* Move on; run rip_input() directly */
                } else {
                        struct protosw *pr;
                        struct lwkt_port *port;
                        int cpu;

                        pr = &inetsw[ip_protox[icp->icmp_ip.ip_p]];
                        port = so_pr_ctlport(pr, code,
                            (struct sockaddr *)&icmpsrc, &icp->icmp_ip, &cpu);
                        if (port != NULL) {
                                if (cpu == netisr_ncpus) {
                                        if (netisr_ncpus > 1) {
                                                /*
                                                 * Run pr_ctlinput in all
                                                 * netisrs
                                                 */
                                                icmp_ctlinput_global_start(m,
                                                    code, hlen, proto);
                                                return IPPROTO_DONE;
                                        }
                                        /*
                                         * There is only one netisr; run
                                         * pr_ctlinput directly.
                                         */
                                } else if (cpu != mycpuid) {
                                        /*
                                         * Send to the target netisr to run
                                         * pr_ctlinput.
                                         */
                                        icmp_ctlinput_start(m, port,
                                            code, hlen, proto);
                                        return IPPROTO_DONE;
                                }

                                /*
                                 * The target netisr is this netisr.
                                 *
                                 * XXX if the packet contains [IPv4 AH TCP],
                                 * we can't make a notification to TCP layer.
                                 */
                                so_pr_ctlinput_direct(pr, code,
                                    (struct sockaddr *)&icmpsrc, &icp->icmp_ip);
                        }
                        /* Move on; run rip_input() directly */
                }
                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;
#ifdef ICMP_BANDLIM
                if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0)
                        goto freeit;
                else
#endif
                        goto reflect;

        case ICMP_TSTAMP:
                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! */
#ifdef ICMP_BANDLIM
                if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0)
                        goto freeit;
                else
#endif
                        goto reflect;

        case ICMP_MASKREQ:
                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 == NULL)
                        break;
                if (ia->ia_ifp == 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;
                }
reflect:
                icmpstat.icps_reflect++;
                icmpstat.icps_outhist[icp->icmp_type]++;
                icmp_reflect(m);
                return(IPPROTO_DONE);

        case ICMP_REDIRECT:
                if (log_redirect) {
                        char src_buf[INET_ADDRSTRLEN];
                        char dst_buf[INET_ADDRSTRLEN];
                        char gwy_buf[INET_ADDRSTRLEN];

                        kprintf("icmp redirect from %s: %s => %s\n",
                            inet_ntop(AF_INET, &ip->ip_src,
                                src_buf, INET_ADDRSTRLEN),
                            inet_ntop(AF_INET, &icp->icmp_ip.ip_dst,
                                dst_buf, INET_ADDRSTRLEN),
                            inet_ntop(AF_INET, &icp->icmp_gwaddr,
                                gwy_buf, INET_ADDRSTRLEN));
                }
                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;
                }
#ifdef ICMPPRINTFS
                if (icmpprintfs) {
                        char dst_buf[INET_ADDRSTRLEN], gw_buf[INET_ADDRSTRLEN];

                        kprintf("redirect dst %s to %s\n",
                            inet_ntop(AF_INET, &icp->icmp_ip.ip_dst,
                                dst_buf, INET_ADDRSTRLEN),
                            inet_ntop(AF_INET, &icp->icmp_gwaddr,
                                gw_buf, INET_ADDRSTRLEN));
                }
#endif
                icmpsrc.sin_addr = icp->icmp_ip.ip_dst;

                /* Run redirect in all netisrs */
                if (icmp_redirect_start(m, hlen, proto)) {
                        /* Forwarded; done */
                        return IPPROTO_DONE;
                }
                /* Move on; run rip_input() directly */
                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:
        *mp = m;
        rip_input(mp, offp, proto);
        return(IPPROTO_DONE);

freeit:
        m_freem(m);
        return(IPPROTO_DONE);
}

/*
 * Reflect the ip packet back to the source
 */
static void
icmp_reflect(struct mbuf *m)
{
        struct ip *ip = mtod(m, struct ip *);
        struct in_ifaddr *ia;
        struct in_ifaddr_container *iac;
        struct ifaddr_container *ifac;
        struct ifnet *ifp;
        struct in_addr t;
        struct mbuf *opts = NULL;
        int optlen = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof(struct ip);
        struct route *ro = NULL, rt;

        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 */
                icmpstat.icps_badaddr++;
                goto done;      /* Ip_output() will check for broadcast */
        }
        t = ip->ip_dst;
        ip->ip_dst = ip->ip_src;

        ro = &rt;
        bzero(ro, sizeof *ro);

        /*
         * 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.
         */
        ia = NULL;
        LIST_FOREACH(iac, INADDR_HASH(t.s_addr), ia_hash) {
                if (t.s_addr == IA_SIN(iac->ia)->sin_addr.s_addr) {
                        ia = iac->ia;
                        goto match;
                }
        }
        ifp = m->m_pkthdr.rcvif;
        if (ifp != NULL && (ifp->if_flags & IFF_BROADCAST)) {
                TAILQ_FOREACH(ifac, &ifp->if_addrheads[mycpuid], ifa_link) {
                        struct ifaddr *ifa = ifac->ifa;

                        if (ifa->ifa_addr->sa_family != AF_INET)
                                continue;
                        ia = ifatoia(ifa);
                        if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
                            t.s_addr)
                                goto match;
                }
        }
        /*
         * If the packet was transiting through us, use the address of
         * the interface the packet came through in.  If that interface
         * doesn't have a suitable IP address, the normal selection
         * criteria apply.
         */
        if (icmp_rfi && ifp != NULL) {
                TAILQ_FOREACH(ifac, &ifp->if_addrheads[mycpuid], ifa_link) {
                        struct ifaddr *ifa = ifac->ifa;

                        if (ifa->ifa_addr->sa_family != AF_INET)
                                continue;
                        ia = ifatoia(ifa);
                        goto match;
                }
        }
        /*
         * If the incoming packet was not addressed directly to us, use
         * designated interface for icmp replies specified by sysctl
         * net.inet.icmp.reply_src (default not set). Otherwise continue
         * with normal source selection.
         */
        if (icmp_reply_src[0] != '\0' &&
            (ifp = ifunit_netisr(icmp_reply_src))) {
                TAILQ_FOREACH(ifac, &ifp->if_addrheads[mycpuid], ifa_link) {
                        struct ifaddr *ifa = ifac->ifa;

                        if (ifa->ifa_addr->sa_family != AF_INET)
                                continue;
                        ia = ifatoia(ifa);
                        goto match;
                }
        }
        /*
         * If the packet was transiting through us, use the address of
         * the interface that is the closest to the packet source.
         * When we don't have a route back to the packet source, stop here
         * and drop the packet.
         */
        ia = ip_rtaddr(ip->ip_dst, ro);
        if (ia == NULL) {
                m_freem(m);
                icmpstat.icps_noroute++;
                goto done;
        }
match:
        t = IA_SIN(ia)->sin_addr;
        ip->ip_src = t;
        ip->ip_ttl = ip_defttl;

        if (optlen > 0) {
                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(m)) == NULL &&
                    (opts = m_gethdr(M_NOWAIT, MT_HEADER))) {
                        opts->m_len = sizeof(struct in_addr);
                        mtod(opts, struct in_addr *)->s_addr = 0;
                }
                if (opts) {
#ifdef ICMPPRINTFS
                        if (icmpprintfs)
                                kprintf("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(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++;
                                }
                        }
#ifdef ICMPPRINTFS
                        if (icmpprintfs)
                                kprintf("%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 = htons(ntohs(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, ip + 1,
                      m->m_len - sizeof(struct ip));
        }
        m->m_pkthdr.fw_flags &= FW_MBUF_GENERATED;
        m->m_flags &= ~(M_BCAST|M_MCAST);
        icmp_send(m, opts, ro);
done:
        if (opts)
                m_free(opts);
        if (ro && ro->ro_rt)
                RTFREE(ro->ro_rt);
}

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

        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, ntohs(ip->ip_len) - hlen);
        m->m_data -= hlen;
        m->m_len += hlen;
        m->m_pkthdr.rcvif = NULL;
#ifdef ICMPPRINTFS
        if (icmpprintfs) {
                char dst_buf[INET_ADDRSTRLEN], src_buf[INET_ADDRSTRLEN];

                kprintf("icmp_send dst %s src %s\n",
                    inet_ntop(AF_INET, &ip->ip_dst, dst_buf, INET_ADDRSTRLEN),
                    inet_ntop(AF_INET, &ip->ip_src, src_buf, INET_ADDRSTRLEN));
        }
#endif
        ip_output(m, opts, rt, 0, NULL, NULL);
}

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

        getmicrotime(&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.
 */
int
ip_next_mtu(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

#ifdef 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 int lticks[BANDLIM_MAX + 1];
        static int lpackets[BANDLIM_MAX + 1];
        int dticks;
        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);
        dticks = ticks - lticks[which];

        /*
         * reset stats when cumulative dt exceeds one second.
         */

        if ((unsigned int)dticks > hz) {
                if (lpackets[which] > icmplim && icmplim_output) {
                        kprintf("%s from %d to %d packets per second\n",
                                bandlimittype[which],
                                lpackets[which],
                                icmplim
                        );
                }
                lticks[which] = ticks;
                lpackets[which] = 0;
        }

        /*
         * bump packet count
         */

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