src/ip_icmp.c - libslirp - Git at Google

 /* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * 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.h"
 #include "ip_icmp.h"

 #ifndef WITH_ICMP_ERROR_MSG
 #define WITH_ICMP_ERROR_MSG 0
 #endif

 /* The message sent when emulating PING */
 /* Be nice and tell them it's just a pseudo-ping packet */
 static 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_send_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
 };

 void icmp_init(Slirp *slirp)
 {
     slirp->icmp.so_next = slirp->icmp.so_prev = &slirp->icmp;
     slirp->icmp_last_so = &slirp->icmp;
 }

 void icmp_cleanup(Slirp *slirp)
 {
     struct socket *so, *so_next;

     for (so = slirp->icmp.so_next; so != &slirp->icmp; so = so_next) {
         so_next = so->so_next;
         icmp_detach(so);
     }
 }

 static int icmp_send(struct socket *so, struct mbuf *m, int hlen)
 {
     struct ip *ip = mtod(m, struct ip *);
     struct sockaddr_in addr;

     so->s = slirp_socket(AF_INET, SOCK_DGRAM, IPPROTO_ICMP);
     if (so->s == -1) {
         return -1;
     }

     if (slirp_bind_outbound(so, AF_INET) != 0) {
         // bind failed - close socket
         closesocket(so->s);
         so->s = -1;
         return -1;
     }

     so->so_m = m;
     so->so_faddr = ip->ip_dst;
     so->so_laddr = ip->ip_src;
     so->so_iptos = ip->ip_tos;
     so->so_type = IPPROTO_ICMP;
     so->so_state = SS_ISFCONNECTED;
     so->so_expire = curtime + SO_EXPIRE;

     addr.sin_family = AF_INET;
     addr.sin_addr = so->so_faddr;

     insque(so, &so->slirp->icmp);

     if (sendto(so->s, m->m_data + hlen, m->m_len - hlen, 0,
                (struct sockaddr *)&addr, sizeof(addr)) == -1) {
         DEBUG_MISC("icmp_input icmp sendto tx errno = %d-%s", errno,
                    strerror(errno));
         icmp_send_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0, strerror(errno));
         icmp_detach(so);
     }

     return 0;
 }

 void icmp_detach(struct socket *so)
 {
     so->slirp->cb->unregister_poll_fd(so->s, so->slirp->opaque);
     closesocket(so->s);
     sofree(so);
 }

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

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

     /*
      * 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 */
     freeit:
         m_free(m);
         goto end_error;
     }

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

     DEBUG_ARG("icmp_type = %d", icp->icmp_type);
     switch (icp->icmp_type) {
     case ICMP_ECHO:
         ip->ip_len += hlen; /* since ip_input subtracts this */
         if (ip->ip_dst.s_addr == slirp->vhost_addr.s_addr ||
             ip->ip_dst.s_addr == slirp->vnameserver_addr.s_addr) {
             icmp_reflect(m);
         } else if (slirp->restricted) {
             goto freeit;
         } else {
             struct socket *so;
             struct sockaddr_storage addr;
             so = socreate(slirp);
             if (icmp_send(so, m, hlen) == 0) {
                 return;
             }
             if (udp_attach(so, AF_INET) == -1) {
                 DEBUG_MISC("icmp_input udp_attach errno = %d-%s", errno,
                            strerror(errno));
                 sofree(so);
                 m_free(m);
                 goto end_error;
             }
             so->so_m = m;
             so->so_ffamily = AF_INET;
             so->so_faddr = ip->ip_dst;
             so->so_fport = htons(7);
             so->so_lfamily = AF_INET;
             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 = so->fhost.ss;
             if (sotranslate_out(so, &addr) < 0) {
                 icmp_send_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0,
                                 strerror(errno));
                 udp_detach(so);
                 return;
             }

             if (sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
                        (struct sockaddr *)&addr, sockaddr_size(&addr)) == -1) {
                 DEBUG_MISC("icmp_input udp sendto tx errno = %d-%s", errno,
                            strerror(errno));
                 icmp_send_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:
         m_free(m);
         break;

     default:
         m_free(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_send_error(struct mbuf *msrc, uint8_t type, uint8_t code, int minsize,
                      const char *message)
 {
     unsigned hlen, shlen, s_ip_len;
     register struct ip *ip;
     register struct icmp *icp;
     register struct mbuf *m;

     DEBUG_CALL("icmp_send_error");
     DEBUG_ARG("msrc = %p", 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 & DBG_MISC) {
         char bufa[20], bufb[20];
         slirp_pstrcpy(bufa, sizeof(bufa), inet_ntoa(ip->ip_src));
         slirp_pstrcpy(bufb, sizeof(bufb), inet_ntoa(ip->ip_dst));
         DEBUG_MISC(" %.16s to %.16s", bufa, bufb);
     }
     if (ip->ip_off & IP_OFFMASK)
         goto end_error; /* Only reply to fragment 0 */

     /* Do not reply to source-only IPs */
     if ((ip->ip_src.s_addr & htonl(~(0xf << 28))) == 0) {
         goto end_error;
     }

     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 */
     m = m_get(msrc->slirp);
     if (!m) {
         goto end_error;
     }

     {
         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 (message && WITH_ICMP_ERROR_MSG) { /* 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;
     }

     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 addresses */
     ip->ip_src = m->slirp->vhost_addr;

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

 end_error:
     return;
 }
 #undef ICMP_MAXDATALEN

 /*
  * Reflect the ip packet back to the source
  */
 void icmp_reflect(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_type = ICMP_ECHOREPLY;
     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((char *)(ip + 1), (char *)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);
 }

 void icmp_receive(struct socket *so)
 {
     struct mbuf *m = so->so_m;
     struct ip *ip = mtod(m, struct ip *);
     int hlen = ip->ip_hl << 2;
     uint8_t error_code;
     struct icmp *icp;
     int id, len;

     m->m_data += hlen;
     m->m_len -= hlen;
     icp = mtod(m, struct icmp *);

     id = icp->icmp_id;
     len = recv(so->s, icp, M_ROOM(m), 0);
     /*
      * The behavior of reading SOCK_DGRAM+IPPROTO_ICMP sockets is inconsistent
      * between host OSes.  On Linux, only the ICMP header and payload is
      * included.  On macOS/Darwin, the socket acts like a raw socket and
      * includes the IP header as well.  On other BSDs, SOCK_DGRAM+IPPROTO_ICMP
      * sockets aren't supported at all, so we treat them like raw sockets.  It
      * isn't possible to detect this difference at runtime, so we must use an
      * #ifdef to determine if we need to remove the IP header.
      */
 #ifdef CONFIG_BSD
     if (len >= sizeof(struct ip)) {
         struct ip *inner_ip = mtod(m, struct ip *);
         int inner_hlen = inner_ip->ip_hl << 2;
         if (inner_hlen > len) {
             len = -1;
             errno = -EINVAL;
         } else {
             len -= inner_hlen;
             memmove(icp, (unsigned char *)icp + inner_hlen, len);
         }
     } else {
         len = -1;
         errno = -EINVAL;
     }
 #endif
     icp->icmp_id = id;

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

     if (len == -1 || len == 0) {
         if (errno == ENETUNREACH) {
             error_code = ICMP_UNREACH_NET;
         } else {
             error_code = ICMP_UNREACH_HOST;
         }
         DEBUG_MISC(" udp icmp rx errno = %d-%s", errno, strerror(errno));
         icmp_send_error(so->so_m, ICMP_UNREACH, error_code, 0, strerror(errno));
     } else {
         icmp_reflect(so->so_m);
         so->so_m = NULL; /* Don't m_free() it again! */
     }
     icmp_detach(so);
 }
	/* SPDX-License-Identifier: BSD-3-Clause */
	/*
	* 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.h"
	#include "ip_icmp.h"

	#ifndef WITH_ICMP_ERROR_MSG
	#define WITH_ICMP_ERROR_MSG 0
	#endif

	/* The message sent when emulating PING */
	/* Be nice and tell them it's just a pseudo-ping packet */
	static 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_send_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
	};

	void icmp_init(Slirp *slirp)
	{
	slirp->icmp.so_next = slirp->icmp.so_prev = &slirp->icmp;
	slirp->icmp_last_so = &slirp->icmp;
	}

	void icmp_cleanup(Slirp *slirp)
	{
	struct socket so, so_next;

	for (so = slirp->icmp.so_next; so != &slirp->icmp; so = so_next) {
	so_next = so->so_next;
	icmp_detach(so);
	}
	}

	static int icmp_send(struct socket so, struct mbuf m, int hlen)
	{
	struct ip ip = mtod(m, struct ip );
	struct sockaddr_in addr;

	so->s = slirp_socket(AF_INET, SOCK_DGRAM, IPPROTO_ICMP);
	if (so->s == -1) {
	return -1;
	}

	if (slirp_bind_outbound(so, AF_INET) != 0) {
	// bind failed - close socket
	closesocket(so->s);
	so->s = -1;
	return -1;
	}

	so->so_m = m;
	so->so_faddr = ip->ip_dst;
	so->so_laddr = ip->ip_src;
	so->so_iptos = ip->ip_tos;
	so->so_type = IPPROTO_ICMP;
	so->so_state = SS_ISFCONNECTED;
	so->so_expire = curtime + SO_EXPIRE;

	addr.sin_family = AF_INET;
	addr.sin_addr = so->so_faddr;

	insque(so, &so->slirp->icmp);

	if (sendto(so->s, m->m_data + hlen, m->m_len - hlen, 0,
	(struct sockaddr *)&addr, sizeof(addr)) == -1) {
	DEBUG_MISC("icmp_input icmp sendto tx errno = %d-%s", errno,
	strerror(errno));
	icmp_send_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0, strerror(errno));
	icmp_detach(so);
	}

	return 0;
	}

	void icmp_detach(struct socket *so)
	{
	so->slirp->cb->unregister_poll_fd(so->s, so->slirp->opaque);
	closesocket(so->s);
	sofree(so);
	}

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

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

	/*
	* 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 */
	freeit:
	m_free(m);
	goto end_error;
	}

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

	DEBUG_ARG("icmp_type = %d", icp->icmp_type);
	switch (icp->icmp_type) {
	case ICMP_ECHO:
	ip->ip_len += hlen; /* since ip_input subtracts this */
	if (ip->ip_dst.s_addr == slirp->vhost_addr.s_addr \|\|
	ip->ip_dst.s_addr == slirp->vnameserver_addr.s_addr) {
	icmp_reflect(m);
	} else if (slirp->restricted) {
	goto freeit;
	} else {
	struct socket *so;
	struct sockaddr_storage addr;
	so = socreate(slirp);
	if (icmp_send(so, m, hlen) == 0) {
	return;
	}
	if (udp_attach(so, AF_INET) == -1) {
	DEBUG_MISC("icmp_input udp_attach errno = %d-%s", errno,
	strerror(errno));
	sofree(so);
	m_free(m);
	goto end_error;
	}
	so->so_m = m;
	so->so_ffamily = AF_INET;
	so->so_faddr = ip->ip_dst;
	so->so_fport = htons(7);
	so->so_lfamily = AF_INET;
	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 = so->fhost.ss;
	if (sotranslate_out(so, &addr) < 0) {
	icmp_send_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0,
	strerror(errno));
	udp_detach(so);
	return;
	}

	if (sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
	(struct sockaddr *)&addr, sockaddr_size(&addr)) == -1) {
	DEBUG_MISC("icmp_input udp sendto tx errno = %d-%s", errno,
	strerror(errno));
	icmp_send_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:
	m_free(m);
	break;

	default:
	m_free(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_send_error(struct mbuf *msrc, uint8_t type, uint8_t code, int minsize,
	const char *message)
	{
	unsigned hlen, shlen, s_ip_len;
	register struct ip *ip;
	register struct icmp *icp;
	register struct mbuf *m;

	DEBUG_CALL("icmp_send_error");
	DEBUG_ARG("msrc = %p", 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 & DBG_MISC) {
	char bufa[20], bufb[20];
	slirp_pstrcpy(bufa, sizeof(bufa), inet_ntoa(ip->ip_src));
	slirp_pstrcpy(bufb, sizeof(bufb), inet_ntoa(ip->ip_dst));
	DEBUG_MISC(" %.16s to %.16s", bufa, bufb);
	}
	if (ip->ip_off & IP_OFFMASK)
	goto end_error; /* Only reply to fragment 0 */

	/* Do not reply to source-only IPs */
	if ((ip->ip_src.s_addr & htonl(~(0xf << 28))) == 0) {
	goto end_error;
	}

	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 */
	m = m_get(msrc->slirp);
	if (!m) {
	goto end_error;
	}

	{
	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 (message && WITH_ICMP_ERROR_MSG) { /* 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;
	}

	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 addresses */
	ip->ip_src = m->slirp->vhost_addr;

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

	end_error:
	return;
	}
	#undef ICMP_MAXDATALEN

	/*
	* Reflect the ip packet back to the source
	*/
	void icmp_reflect(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_type = ICMP_ECHOREPLY;
	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((char )(ip + 1), (char )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);
	}

	void icmp_receive(struct socket *so)
	{
	struct mbuf *m = so->so_m;
	struct ip ip = mtod(m, struct ip );
	int hlen = ip->ip_hl << 2;
	uint8_t error_code;
	struct icmp *icp;
	int id, len;

	m->m_data += hlen;
	m->m_len -= hlen;
	icp = mtod(m, struct icmp *);

	id = icp->icmp_id;
	len = recv(so->s, icp, M_ROOM(m), 0);
	/*
	* The behavior of reading SOCK_DGRAM+IPPROTO_ICMP sockets is inconsistent
	* between host OSes. On Linux, only the ICMP header and payload is
	* included. On macOS/Darwin, the socket acts like a raw socket and
	* includes the IP header as well. On other BSDs, SOCK_DGRAM+IPPROTO_ICMP
	* sockets aren't supported at all, so we treat them like raw sockets. It
	* isn't possible to detect this difference at runtime, so we must use an
	* #ifdef to determine if we need to remove the IP header.
	*/
	#ifdef CONFIG_BSD
	if (len >= sizeof(struct ip)) {
	struct ip inner_ip = mtod(m, struct ip );
	int inner_hlen = inner_ip->ip_hl << 2;
	if (inner_hlen > len) {
	len = -1;
	errno = -EINVAL;
	} else {
	len -= inner_hlen;
	memmove(icp, (unsigned char *)icp + inner_hlen, len);
	}
	} else {
	len = -1;
	errno = -EINVAL;
	}
	#endif
	icp->icmp_id = id;

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

	if (len == -1 \|\| len == 0) {
	if (errno == ENETUNREACH) {
	error_code = ICMP_UNREACH_NET;
	} else {
	error_code = ICMP_UNREACH_HOST;
	}
	DEBUG_MISC(" udp icmp rx errno = %d-%s", errno, strerror(errno));
	icmp_send_error(so->so_m, ICMP_UNREACH, error_code, 0, strerror(errno));
	} else {
	icmp_reflect(so->so_m);
	so->so_m = NULL; /* Don't m_free() it again! */
	}
	icmp_detach(so);
	}