/*
 * 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
 * ip_icmp.c,v 1.7 1995/05/30 08:09:42 rgrimes Exp
 */

#include "slirp/slirp.h"
#include "slirp/ip_icmp.h"

struct icmpstat icmpstat;

/* The message sent when emulating PING */
/* Be nice and tell them it's just a psuedo-ping packet */
char icmp_ping_msg[] = "This is a psuedo-PING packet used by Slirp to emulate ICMP ECHO-REQUEST packets.\n";

/* list of actions for icmp_error() on RX of an icmp message */
static int icmp_flush[19] = {
        /*  ECHO REPLY (0)  */ 0,
        1,
        1,
        /* DEST UNREACH (3) */ 1,
        /* SOURCE QUENCH (4)*/ 1,
        /* REDIRECT (5) */ 1,
        1,
        1,
        /* ECHO (8) */ 0,
        /* ROUTERADVERT (9) */ 1,
        /* ROUTERSOLICIT (10) */ 1,
        /* TIME EXCEEDED (11) */ 1,
        /* PARAMETER PROBLEM (12) */ 1,
        /* TIMESTAMP (13) */ 0,
        /* TIMESTAMP REPLY (14) */ 0,
        /* INFO (15) */ 0,
        /* INFO REPLY (16) */ 0,
        /* ADDR MASK (17) */ 0,
        /* ADDR MASK REPLY (18) */ 0};

/*
 * Process a received ICMP message.
 */
void icmp_input(m, hlen) struct SLIRPmbuf *m;
int hlen;
{
        register struct icmp *icp;
        register struct ip *ip = mtod(m, struct ip *);
        int icmplen = ip->ip_len;
        /* int code; */

        DEBUG_CALL("icmp_input");
        DEBUG_ARG("m = %lx", (long)m);
        DEBUG_ARG("m_len = %d", m->m_len);

        icmpstat.icps_received++;

        /*
         * Locate icmp structure in SLIRPmbuf, and check
         * that its not corrupted and of at least minimum length.
         */
        if (icmplen < ICMP_MINLEN) { /* min 8 bytes payload */
                icmpstat.icps_tooshort++;
        freeit:
                m_freem(m);
                goto end_error;
        }

        m->m_len -= hlen;
        m->m_data += hlen;
        icp = mtod(m, struct icmp *);
        if (cksum(m, icmplen)) {
                icmpstat.icps_checksum++;
                goto freeit;
        }
        m->m_len += hlen;
        m->m_data -= hlen;

        /*	icmpstat.icps_inhist[icp->icmp_type]++; */
        /* code = icp->icmp_code; */

        DEBUG_ARG("icmp_type = %d", icp->icmp_type);
        switch (icp->icmp_type) {
        case ICMP_ECHO:
                icp->icmp_type = ICMP_ECHOREPLY;
                ip->ip_len += hlen; /* since ip_input subtracts this */
                if (ip->ip_dst.s_addr == alias_addr.s_addr) {
                        icmp_reflect(m);
                } else {
                        struct SLIRPsocket *so;
                        struct sockaddr_in addr;
                        if ((so = socreate()) == NULL)
                                goto freeit;
                        if (udp_attach(so) == -1) {
                                DEBUG_MISC((dfd, "icmp_input udp_attach errno = %d-%s\n", errno, strerror(errno)));
                                sofree(so);
                                m_free(m);
                                goto end_error;
                        }
                        so->so_m = m;
                        so->so_faddr = ip->ip_dst;
                        so->so_fport = htons(7);
                        so->so_laddr = ip->ip_src;
                        so->so_lport = htons(9);
                        so->so_iptos = ip->ip_tos;
                        so->so_type = IPPROTO_ICMP;
                        so->so_state = SS_ISFCONNECTED;

                        /* Send the packet */
                        addr.sin_family = AF_INET;
                        if ((so->so_faddr.s_addr & htonl(0xffffff00)) == special_addr.s_addr) {
                                /* It's an alias */
                                switch (ntohl(so->so_faddr.s_addr) & 0xff) {
                                case CTL_DNS:
                                        addr.sin_addr = dns_addr;
                                        break;
                                case CTL_ALIAS:
                                default:
                                        addr.sin_addr = loopback_addr;
                                        break;
                                }
                        } else {
                                addr.sin_addr = so->so_faddr;
                        }
                        addr.sin_port = so->so_fport;
                        if (sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0, (struct sockaddr *)&addr, sizeof(addr)) ==
                            -1) {
                                DEBUG_MISC((dfd, "icmp_input udp sendto tx errno = %d-%s\n", errno, strerror(errno)));
                                icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0, strerror(errno));
                                udp_detach(so);
                        }
                } /* if ip->ip_dst.s_addr == alias_addr.s_addr */
                break;
        case ICMP_UNREACH:
                /* XXX? report error? close socket? */
        case ICMP_TIMXCEED:
        case ICMP_PARAMPROB:
        case ICMP_SOURCEQUENCH:
        case ICMP_TSTAMP:
        case ICMP_MASKREQ:
        case ICMP_REDIRECT:
                icmpstat.icps_notsupp++;
                m_freem(m);
                break;

        default:
                icmpstat.icps_badtype++;
                m_freem(m);
        } /* swith */

end_error:
        /* m is m_free()'d xor put in a socket xor or given to ip_send */
        return;
}

/*
 *	Send an ICMP message in response to a situation
 *
 *	RFC 1122: 3.2.2	MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
 *			MUST NOT change this header information.
 *			MUST NOT reply to a multicast/broadcast IP address.
 *			MUST NOT reply to a multicast/broadcast MAC address.
 *			MUST reply to only the first fragment.
 */
/*
 * Send ICMP_UNREACH back to the source regarding msrc.
 * SLIRPmbuf *msrc is used as a template, but is NOT m_free()'d.
 * It is reported as the bad ip packet.  The header should
 * be fully correct and in host byte order.
 * ICMP fragmentation is illegal.  All machines must accept 576 bytes in one
 * packet.  The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
 */

#define ICMP_MAXDATALEN (IP_MSS - 28)
void icmp_error(msrc, type, code, minsize, message) struct SLIRPmbuf *msrc;
u_char type;
u_char code;
int minsize;
char *message;
{
        unsigned hlen, shlen, s_ip_len;
        register struct ip *ip;
        register struct icmp *icp;
        register struct SLIRPmbuf *m;

        DEBUG_CALL("icmp_error");
        DEBUG_ARG("msrc = %lx", (long)msrc);
        DEBUG_ARG("msrc_len = %d", msrc->m_len);

        if (type != ICMP_UNREACH && type != ICMP_TIMXCEED)
                goto end_error;

        /* check msrc */
        if (!msrc)
                goto end_error;
        ip = mtod(msrc, struct ip *);
#if SLIRP_DEBUG
        {
                char bufa[20], bufb[20];
                strcpy(bufa, inet_ntoa(ip->ip_src));
                strcpy(bufb, inet_ntoa(ip->ip_dst));
                DEBUG_MISC((dfd, " %.16s to %.16s\n", bufa, bufb));
        }
#endif
        if (ip->ip_off & IP_OFFMASK)
                goto end_error; /* Only reply to fragment 0 */

        shlen = ip->ip_hl << 2;
        s_ip_len = ip->ip_len;
        if (ip->ip_p == IPPROTO_ICMP) {
                icp = (struct icmp *)((char *)ip + shlen);
                /*
                 *	Assume any unknown ICMP type is an error. This isn't
                 *	specified by the RFC, but think about it..
                 */
                if (icp->icmp_type > 18 || icmp_flush[icp->icmp_type])
                        goto end_error;
        }

        /* make a copy */
        if (!(m = m_get()))
                goto end_error; /* get SLIRPmbuf */
        {
                u_int new_m_size;
                new_m_size = sizeof(struct ip) + ICMP_MINLEN + msrc->m_len + ICMP_MAXDATALEN;
                if (new_m_size > m->m_size)
                        m_inc(m, new_m_size);
        }
        memcpy(m->m_data, msrc->m_data, msrc->m_len);
        m->m_len = msrc->m_len; /* copy msrc to m */

        /* make the header of the reply packet */
        ip = mtod(m, struct ip *);
        hlen = sizeof(struct ip); /* no options in reply */

        /* fill in icmp */
        m->m_data += hlen;
        m->m_len -= hlen;

        icp = mtod(m, struct icmp *);

        if (minsize)
                s_ip_len = shlen + ICMP_MINLEN; /* return header+8b only */
        else if (s_ip_len > ICMP_MAXDATALEN)    /* maximum size */
                s_ip_len = ICMP_MAXDATALEN;

        m->m_len = ICMP_MINLEN + s_ip_len; /* 8 bytes ICMP header */

        /* min. size = 8+sizeof(struct ip)+8 */

        icp->icmp_type = type;
        icp->icmp_code = code;
        icp->icmp_id = 0;
        icp->icmp_seq = 0;

        memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len); /* report the ip packet */
        HTONS(icp->icmp_ip.ip_len);
        HTONS(icp->icmp_ip.ip_id);
        HTONS(icp->icmp_ip.ip_off);

#if SLIRP_DEBUG
        if (message) { /* DEBUG : append message to ICMP packet */
                int message_len;
                char *cpnt;
                message_len = strlen(message);
                if (message_len > ICMP_MAXDATALEN)
                        message_len = ICMP_MAXDATALEN;
                cpnt = (char *)m->m_data + m->m_len;
                memcpy(cpnt, message, message_len);
                m->m_len += message_len;
        }
#endif

        icp->icmp_cksum = 0;
        icp->icmp_cksum = cksum(m, m->m_len);

        m->m_data -= hlen;
        m->m_len += hlen;

        /* fill in ip */
        ip->ip_hl = hlen >> 2;
        ip->ip_len = (u_int16_t)m->m_len;

        ip->ip_tos = ((ip->ip_tos & 0x1E) | 0xC0); /* high priority for errors */

        ip->ip_ttl = MAXTTL;
        ip->ip_p = IPPROTO_ICMP;
        ip->ip_dst = ip->ip_src; /* ip adresses */
        ip->ip_src = alias_addr;

        (void)ip_output((struct SLIRPsocket *)NULL, m);

        icmpstat.icps_reflect++;

end_error:
        return;
}
#undef ICMP_MAXDATALEN

/*
 * Reflect the ip packet back to the source
 */
void icmp_reflect(m) struct SLIRPmbuf *m;
{
        register struct ip *ip = mtod(m, struct ip *);
        int hlen = ip->ip_hl << 2;
        int optlen = hlen - sizeof(struct ip);
        register struct icmp *icp;

        /*
         * Send an icmp packet back to the ip level,
         * after supplying a checksum.
         */
        m->m_data += hlen;
        m->m_len -= hlen;
        icp = mtod(m, struct icmp *);

        icp->icmp_cksum = 0;
        icp->icmp_cksum = cksum(m, ip->ip_len - hlen);

        m->m_data -= hlen;
        m->m_len += hlen;

        /* fill in ip */
        if (optlen > 0) {
                /*
                 * Strip out original options by copying rest of first
                 * SLIRPmbuf's data back, and adjust the IP length.
                 */
                memmove((SLIRPcaddr_t)(ip + 1), (SLIRPcaddr_t)ip + hlen, (unsigned)(m->m_len - hlen));
                hlen -= optlen;
                ip->ip_hl = hlen >> 2;
                ip->ip_len -= optlen;
                m->m_len -= optlen;
        }

        ip->ip_ttl = MAXTTL;
        { /* swap */
                struct in_addr icmp_dst;
                icmp_dst = ip->ip_dst;
                ip->ip_dst = ip->ip_src;
                ip->ip_src = icmp_dst;
        }

        (void)ip_output((struct SLIRPsocket *)NULL, m);

        icmpstat.icps_reflect++;
}
