/*
 * Copyright (C) 1993 AmiTCP/IP Group, <amitcp-group@hut.fi>
 *                    Helsinki University of Technology, Finland.
 *                    All rights reserved.
 * Copyright (C) 2005 Neil Cafferkey
 *
 * This program is free software; you can redistribute it 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 ANY 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.
 *
 */

/*
 * Copyright (C) 1982, 1986, 1989 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	7.15 (Berkeley) 4/20/91
 */

#include <conf.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
/*#include <sys/time.h>*/
#include <sys/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>

#include <netinet/ip_icmp_protos.h>
#include <netinet/ip_input_protos.h>
#include <netinet/ip_output_protos.h>
#include <netinet/in_cksum_protos.h>
#include <netinet/in_protos.h>
#include <kern/uipc_domain_protos.h>
#include <net/raw_usrreq_protos.h>

struct	icmpstat icmpstat = { 0 };

/*
 * ICMP routines: error generation, receive packet processing, and
 * routines to turnaround packets back to the originator, and
 * host table maintenance routines.
 */
int	icmpprintfs = 0;	/* has effect only if ICMPPRINTFS is defined */

extern	struct protosw inetsw[];

/* tcp_now: 500ms tick counter incremented by tcp_slowtimo() */
extern u_long tcp_now;

/* ICMP rate limiting (token bucket) */
static int icmp_ratelimit_tokens = 10;    /* current tokens */
static int icmp_ratelimit_max = 10;       /* max burst */
static int icmp_ratelimit_rate = 5;       /* tokens per slow-tick (500ms) */
static long icmp_ratelimit_last = 0;      /* last refill time (tcp_now) */

/*
 * Rate-limit ICMP error generation using a token bucket.
 * Returns 1 if allowed, 0 if rate-limited.
 */
static int
icmp_ratelimit(void)
{
    long elapsed;

    elapsed = (long)(tcp_now - icmp_ratelimit_last);
    if (elapsed > 0) {
        icmp_ratelimit_last = tcp_now;
        icmp_ratelimit_tokens += elapsed * icmp_ratelimit_rate;
        if (icmp_ratelimit_tokens > icmp_ratelimit_max)
            icmp_ratelimit_tokens = icmp_ratelimit_max;
    }

    if (icmp_ratelimit_tokens > 0) {
        icmp_ratelimit_tokens--;
        return 1;
    }
    icmpstat.icps_ratelimit++;
    return 0;
}

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

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

#ifdef ICMPPRINTFS
    if(icmpprintfs)
        printf("icmp_error(%lx, %ld, %ld)\n", (u_long)oip, (long)type, (long)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;
    }

    /* Rate-limit ICMP error generation */
    if (!icmp_ratelimit()) {
        goto freeit;
    }

    /*
     * First, formulate icmp message
     */
    m = m_gethdr(M_DONTWAIT, MT_HEADER);
    if(m == NULL)
        goto freeit;
    icmplen = oiplen + MIN(8, oip->ip_len);
    /*
     * The offending packet may be a short copy (e.g. the fixed-size
     * mbuf handed to us from ip_forward), so never quote more bytes
     * than it actually holds or the bcopy below would read past it.
     */
    if(icmplen > n->m_len)
        icmplen = n->m_len;
    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 = dest;
    else
        icp->icmp_void = 0;
    if(type == ICMP_PARAMPROB) {
        icp->icmp_pptr = code;
        code = 0;
    }
    icp->icmp_code = code;
    aligned_bcopy((caddr_t)oip, (caddr_t)&icp->icmp_ip, icmplen);
    nip = &icp->icmp_ip;
    nip->ip_len = htons((u_short)(nip->ip_len + oiplen));

    /*
     * 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 *);
    aligned_bcopy((caddr_t)oip, (caddr_t)nip, oiplen);
    nip->ip_len = m->m_len;
    nip->ip_hl = sizeof(struct ip) >> 2;
    nip->ip_p = IPPROTO_ICMP;
    icmp_reflect(m);

freeit:
    m_freem(n);
}

static struct sockproto icmproto = { AF_INET, IPPROTO_ICMP };
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 };
struct sockaddr_in icmpmask = { 8, 0 };
struct in_ifaddr *ifptoia();

/*
 * Process a received ICMP message.
 */
void icmp_input(void *arg, ...)
{
    register struct mbuf *m = arg;
    register struct icmp *icp;
    register struct ip *ip = mtod(m, struct ip *);
    int icmplen = ip->ip_len;
    register int i;
    struct in_ifaddr *ia;
    int code;
    extern u_char ip_protox[];
    extern struct in_addr in_makeaddr();
    int hlen;
    va_list va;


    va_start(va, arg);
    hlen = va_arg(va, int);
    va_end(va);
    /*
     * Locate icmp structure in mbuf, and check
     * that not corrupted and of at least minimum length.
     */
#ifdef ICMPPRINTFS
    if(icmpprintfs)
        printf("icmp_input from %lx, len %ld\n", (u_long)ip->ip_src.s_addr, (long)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;

#ifdef ICMPPRINTFS
    /*
     * Message type specific processing.
     */
    if(icmpprintfs)
        printf("icmp_input, type %ld code %ld\n", (long)icp->icmp_type,
               (long)icp->icmp_code);
#endif
    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.
         */
        if(icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
                icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
            icmpstat.icps_badlen++;
            goto freeit;
        }
        NTOHS(icp->icmp_ip.ip_len);
#ifdef ICMPPRINTFS
        if(icmpprintfs)
            printf("deliver to protocol %ld\n", (long)icp->icmp_ip.ip_p);
#endif
        icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
        if(inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput)
            (*inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput)
            (code, (struct sockaddr *)&icmpsrc,
             (caddr_t) &icp->icmp_ip);
        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(m->m_pkthdr.rcvif)))
            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(m->m_pkthdr.rcvif)) == 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:
        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(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;
#ifdef	ICMPPRINTFS
        if(icmpprintfs)
            printf("redirect dst %lx to %lx\n", (u_long)icp->icmp_ip.ip_dst.s_addr,
                   (u_long)icp->icmp_gwaddr.s_addr);
#endif
        if(code == ICMP_REDIRECT_NET || code == ICMP_REDIRECT_TOSNET) {
            u_long in_netof();
            icmpsrc.sin_addr =
                in_makeaddr(in_netof(icp->icmp_ip.ip_dst), INADDR_ANY);
            in_sockmaskof(icp->icmp_ip.ip_dst, &icmpmask);
            rtredirect((struct sockaddr *)&icmpsrc,
                       (struct sockaddr *)&icmpdst,
                       (struct sockaddr *)&icmpmask, RTF_GATEWAY,
                       (struct sockaddr *)&icmpgw, (struct rtentry **)0);
            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,
                       (struct sockaddr *)0, RTF_GATEWAY | RTF_HOST,
                       (struct sockaddr *)&icmpgw, (struct rtentry **)0);
            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;
    (void) raw_input(m, &icmproto, (struct sockaddr *)&icmpsrc,
                     (struct sockaddr *)&icmpdst);
    return;

freeit:
    m_freem(m);
}

/*
 * Reflect the ip packet back to the source
 */
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->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(m->m_pkthdr.rcvif);
    if(ia == (struct in_ifaddr *)0)
        ia = in_ifaddr;
    t = IA_SIN(ia)->sin_addr;
    ip->ip_src = t;
    ip->ip_ttl = MAXTTL;

    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) {
#ifdef ICMPPRINTFS
            if(icmpprintfs)
                printf("icmp_reflect optlen %ld rt %ld => ",
                       (long)optlen, (long)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 {
                    len = cp[IPOPT_OLEN];
                    if(len <= 0 || len > cnt)
                        break;
                }
                /*
                 * should check for overflow, but it "can't happen"
                 */
                if(opt == IPOPT_RR || opt == IPOPT_TS) {
                    bcopy((caddr_t)cp,
                          mtod(opts, caddr_t) + opts->m_len, len);
                    opts->m_len += len;
                }
            }
            if(opts->m_len % 4 != 0) {
                *(mtod(opts, caddr_t) + opts->m_len) = IPOPT_EOL;
                opts->m_len++;
            }
#ifdef ICMPPRINTFS
            if(icmpprintfs)
                printf("%ld\n", (long)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_hl = sizeof(struct ip) >> 2;
        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)));
    }
    icmp_send(m, 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.
 */
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;

    hlen = ip->ip_hl << 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;
#ifdef ICMPPRINTFS
    if(icmpprintfs)
        printf("icmp_send dst %lx src %lx\n", (u_long)ip->ip_dst.s_addr, (u_long)ip->ip_src.s_addr);
#endif
    (void) ip_output(m, opts, (struct route *)0, 0);
}

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

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