text: /*
   * 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"
  
  #ifdef LOG_ENABLED
  struct icmpstat icmpstat;
  #endif
  
  /* The message sent when emulating PING */
  /* Be nice and tell them it's just a pseudo-ping packet */
  const char icmp_ping_msg[] = "This is a pseudo-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 const 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);
  
    STAT(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 */
      STAT(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)) {
      STAT(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:
      STAT(icmpstat.icps_notsupp++);
      m_freem(m);
      break;
  
    default:
      STAT(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);
  
    STAT(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);
  
    STAT(icmpstat.icps_reflect++);
  }
  