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/*

 * 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

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

 */

#include "slirp.h"

#include "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 mbuf *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 mbuf, 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 socket *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.

 * mbuf *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 mbuf *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 mbuf *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 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 mbuf */

  { 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 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 = 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 socket *)NULL, m);

  icmpstat.icps_reflect++;

end_error:

  return;

}

#undef ICMP_MAXDATALEN

/*

 * Reflect the ip packet back to the source

 */

void

icmp_reflect(m)

     struct mbuf *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

     * mbuf's data back, and adjust the IP length.

     */

    memmove((caddr_t)(ip + 1), (caddr_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 socket *)NULL, m);

  icmpstat.icps_reflect++;

}