src/slirp/ip_icmp.c

/*
 * 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 == our_addr.s_addr || 
        (ip->ip_dst.s_addr == (special_addr.s_addr|htonl(CTL_ALIAS))) ) {
      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 == our_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 = our_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++;
}
Revision:	1.1
Committed:	2005-05-13T09:00:59Z (19 years, 6 months ago) by gbeauche
Content type:	text/plain
Branch:	MAIN
CVS Tags:	nigel-build-19, nigel-build-17
Log Message:	slirp user mode network emulation code from qemu
#	User	Rev	Content
1	gbeauche	1.1	/*
2			* Copyright (c) 1982, 1986, 1988, 1993
3			* The Regents of the University of California. All rights reserved.
4			*
5			* Redistribution and use in source and binary forms, with or without
6			* modification, are permitted provided that the following conditions
7			* are met:
8			* 1. Redistributions of source code must retain the above copyright
9			* notice, this list of conditions and the following disclaimer.
10			* 2. Redistributions in binary form must reproduce the above copyright
11			* notice, this list of conditions and the following disclaimer in the
12			* documentation and/or other materials provided with the distribution.
13			* 3. All advertising materials mentioning features or use of this software
14			* must display the following acknowledgement:
15			* This product includes software developed by the University of
16			* California, Berkeley and its contributors.
17			* 4. Neither the name of the University nor the names of its contributors
18			* may be used to endorse or promote products derived from this software
19			* without specific prior written permission.
20			*
21			* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22			* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23			* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24			* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25			* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26			* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27			* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28			* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29			* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30			* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31			* SUCH DAMAGE.
32			*
33			* @(#)ip_icmp.c 8.2 (Berkeley) 1/4/94
34			* ip_icmp.c,v 1.7 1995/05/30 08:09:42 rgrimes Exp
35			*/
36
37			#include "slirp.h"
38			#include "ip_icmp.h"
39
40			struct icmpstat icmpstat;
41
42			/* The message sent when emulating PING */
43			/* Be nice and tell them it's just a psuedo-ping packet */
44			char icmp_ping_msg[] = "This is a psuedo-PING packet used by Slirp to emulate ICMP ECHO-REQUEST packets.\n";
45
46			/* list of actions for icmp_error() on RX of an icmp message */
47			static int icmp_flush[19] = {
48			/* ECHO REPLY (0) */ 0,
49			1,
50			1,
51			/* DEST UNREACH (3) */ 1,
52			/* SOURCE QUENCH (4)*/ 1,
53			/* REDIRECT (5) */ 1,
54			1,
55			1,
56			/* ECHO (8) */ 0,
57			/* ROUTERADVERT (9) */ 1,
58			/* ROUTERSOLICIT (10) */ 1,
59			/* TIME EXCEEDED (11) */ 1,
60			/* PARAMETER PROBLEM (12) */ 1,
61			/* TIMESTAMP (13) */ 0,
62			/* TIMESTAMP REPLY (14) */ 0,
63			/* INFO (15) */ 0,
64			/* INFO REPLY (16) */ 0,
65			/* ADDR MASK (17) */ 0,
66			/* ADDR MASK REPLY (18) */ 0
67			};
68
69			/*
70			* Process a received ICMP message.
71			*/
72			void
73			icmp_input(m, hlen)
74			struct mbuf *m;
75			int hlen;
76			{
77			register struct icmp *icp;
78			register struct ip ip=mtod(m, struct ip );
79			int icmplen=ip->ip_len;
80			/* int code; */
81
82			DEBUG_CALL("icmp_input");
83			DEBUG_ARG("m = %lx", (long )m);
84			DEBUG_ARG("m_len = %d", m->m_len);
85
86			icmpstat.icps_received++;
87
88			/*
89			* Locate icmp structure in mbuf, and check
90			* that its not corrupted and of at least minimum length.
91			*/
92			if (icmplen < ICMP_MINLEN) { /* min 8 bytes payload */
93			icmpstat.icps_tooshort++;
94			freeit:
95			m_freem(m);
96			goto end_error;
97			}
98
99			m->m_len -= hlen;
100			m->m_data += hlen;
101			icp = mtod(m, struct icmp *);
102			if (cksum(m, icmplen)) {
103			icmpstat.icps_checksum++;
104			goto freeit;
105			}
106			m->m_len += hlen;
107			m->m_data -= hlen;
108
109			/* icmpstat.icps_inhist[icp->icmp_type]++; */
110			/* code = icp->icmp_code; */
111
112			DEBUG_ARG("icmp_type = %d", icp->icmp_type);
113			switch (icp->icmp_type) {
114			case ICMP_ECHO:
115			icp->icmp_type = ICMP_ECHOREPLY;
116			ip->ip_len += hlen; /* since ip_input subtracts this */
117			if (ip->ip_dst.s_addr == our_addr.s_addr \|\|
118			(ip->ip_dst.s_addr == (special_addr.s_addr\|htonl(CTL_ALIAS))) ) {
119			icmp_reflect(m);
120			} else {
121			struct socket *so;
122			struct sockaddr_in addr;
123			if ((so = socreate()) == NULL) goto freeit;
124			if(udp_attach(so) == -1) {
125			DEBUG_MISC((dfd,"icmp_input udp_attach errno = %d-%s\n",
126			errno,strerror(errno)));
127			sofree(so);
128			m_free(m);
129			goto end_error;
130			}
131			so->so_m = m;
132			so->so_faddr = ip->ip_dst;
133			so->so_fport = htons(7);
134			so->so_laddr = ip->ip_src;
135			so->so_lport = htons(9);
136			so->so_iptos = ip->ip_tos;
137			so->so_type = IPPROTO_ICMP;
138			so->so_state = SS_ISFCONNECTED;
139
140			/* Send the packet */
141			addr.sin_family = AF_INET;
142			if ((so->so_faddr.s_addr & htonl(0xffffff00)) == special_addr.s_addr) {
143			/* It's an alias */
144			switch(ntohl(so->so_faddr.s_addr) & 0xff) {
145			case CTL_DNS:
146			addr.sin_addr = dns_addr;
147			break;
148			case CTL_ALIAS:
149			default:
150			addr.sin_addr = loopback_addr;
151			break;
152			}
153			} else {
154			addr.sin_addr = so->so_faddr;
155			}
156			addr.sin_port = so->so_fport;
157			if(sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
158			(struct sockaddr *)&addr, sizeof(addr)) == -1) {
159			DEBUG_MISC((dfd,"icmp_input udp sendto tx errno = %d-%s\n",
160			errno,strerror(errno)));
161			icmp_error(m, ICMP_UNREACH,ICMP_UNREACH_NET, 0,strerror(errno));
162			udp_detach(so);
163			}
164			} /* if ip->ip_dst.s_addr == our_addr.s_addr */
165			break;
166			case ICMP_UNREACH:
167			/* XXX? report error? close socket? */
168			case ICMP_TIMXCEED:
169			case ICMP_PARAMPROB:
170			case ICMP_SOURCEQUENCH:
171			case ICMP_TSTAMP:
172			case ICMP_MASKREQ:
173			case ICMP_REDIRECT:
174			icmpstat.icps_notsupp++;
175			m_freem(m);
176			break;
177
178			default:
179			icmpstat.icps_badtype++;
180			m_freem(m);
181			} /* swith */
182
183			end_error:
184			/* m is m_free()'d xor put in a socket xor or given to ip_send */
185			return;
186			}
187
188
189			/*
190			* Send an ICMP message in response to a situation
191			*
192			* RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
193			* MUST NOT change this header information.
194			* MUST NOT reply to a multicast/broadcast IP address.
195			* MUST NOT reply to a multicast/broadcast MAC address.
196			* MUST reply to only the first fragment.
197			*/
198			/*
199			* Send ICMP_UNREACH back to the source regarding msrc.
200			* mbuf *msrc is used as a template, but is NOT m_free()'d.
201			* It is reported as the bad ip packet. The header should
202			* be fully correct and in host byte order.
203			* ICMP fragmentation is illegal. All machines must accept 576 bytes in one
204			* packet. The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
205			*/
206
207			#define ICMP_MAXDATALEN (IP_MSS-28)
208			void
209			icmp_error(msrc, type, code, minsize, message)
210			struct mbuf *msrc;
211			u_char type;
212			u_char code;
213			int minsize;
214			char *message;
215			{
216			unsigned hlen, shlen, s_ip_len;
217			register struct ip *ip;
218			register struct icmp *icp;
219			register struct mbuf *m;
220
221			DEBUG_CALL("icmp_error");
222			DEBUG_ARG("msrc = %lx", (long )msrc);
223			DEBUG_ARG("msrc_len = %d", msrc->m_len);
224
225			if(type!=ICMP_UNREACH && type!=ICMP_TIMXCEED) goto end_error;
226
227			/* check msrc */
228			if(!msrc) goto end_error;
229			ip = mtod(msrc, struct ip *);
230			#if DEBUG
231			{ char bufa[20], bufb[20];
232			strcpy(bufa, inet_ntoa(ip->ip_src));
233			strcpy(bufb, inet_ntoa(ip->ip_dst));
234			DEBUG_MISC((dfd, " %.16s to %.16s\n", bufa, bufb));
235			}
236			#endif
237			if(ip->ip_off & IP_OFFMASK) goto end_error; /* Only reply to fragment 0 */
238
239			shlen=ip->ip_hl << 2;
240			s_ip_len=ip->ip_len;
241			if(ip->ip_p == IPPROTO_ICMP) {
242			icp = (struct icmp )((char )ip + shlen);
243			/*
244			* Assume any unknown ICMP type is an error. This isn't
245			* specified by the RFC, but think about it..
246			*/
247			if(icp->icmp_type>18 \|\| icmp_flush[icp->icmp_type]) goto end_error;
248			}
249
250			/* make a copy */
251			if(!(m=m_get())) goto end_error; /* get mbuf */
252			{ int new_m_size;
253			new_m_size=sizeof(struct ip )+ICMP_MINLEN+msrc->m_len+ICMP_MAXDATALEN;
254			if(new_m_size>m->m_size) m_inc(m, new_m_size);
255			}
256			memcpy(m->m_data, msrc->m_data, msrc->m_len);
257			m->m_len = msrc->m_len; /* copy msrc to m */
258
259			/* make the header of the reply packet */
260			ip = mtod(m, struct ip *);
261			hlen= sizeof(struct ip ); /* no options in reply */
262
263			/* fill in icmp */
264			m->m_data += hlen;
265			m->m_len -= hlen;
266
267			icp = mtod(m, struct icmp *);
268
269			if(minsize) s_ip_len=shlen+ICMP_MINLEN; /* return header+8b only */
270			else if(s_ip_len>ICMP_MAXDATALEN) /* maximum size */
271			s_ip_len=ICMP_MAXDATALEN;
272
273			m->m_len=ICMP_MINLEN+s_ip_len; /* 8 bytes ICMP header */
274
275			/* min. size = 8+sizeof(struct ip)+8 */
276
277			icp->icmp_type = type;
278			icp->icmp_code = code;
279			icp->icmp_id = 0;
280			icp->icmp_seq = 0;
281
282			memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len); /* report the ip packet */
283			HTONS(icp->icmp_ip.ip_len);
284			HTONS(icp->icmp_ip.ip_id);
285			HTONS(icp->icmp_ip.ip_off);
286
287			#if DEBUG
288			if(message) { /* DEBUG : append message to ICMP packet */
289			int message_len;
290			char *cpnt;
291			message_len=strlen(message);
292			if(message_len>ICMP_MAXDATALEN) message_len=ICMP_MAXDATALEN;
293			cpnt=(char *)m->m_data+m->m_len;
294			memcpy(cpnt, message, message_len);
295			m->m_len+=message_len;
296			}
297			#endif
298
299			icp->icmp_cksum = 0;
300			icp->icmp_cksum = cksum(m, m->m_len);
301
302			m->m_data -= hlen;
303			m->m_len += hlen;
304
305			/* fill in ip */
306			ip->ip_hl = hlen >> 2;
307			ip->ip_len = m->m_len;
308
309			ip->ip_tos=((ip->ip_tos & 0x1E) \| 0xC0); /* high priority for errors */
310
311			ip->ip_ttl = MAXTTL;
312			ip->ip_p = IPPROTO_ICMP;
313			ip->ip_dst = ip->ip_src; /* ip adresses */
314			ip->ip_src = our_addr;
315
316			(void ) ip_output((struct socket *)NULL, m);
317
318			icmpstat.icps_reflect++;
319
320			end_error:
321			return;
322			}
323			#undef ICMP_MAXDATALEN
324
325			/*
326			* Reflect the ip packet back to the source
327			*/
328			void
329			icmp_reflect(m)
330			struct mbuf *m;
331			{
332			register struct ip ip = mtod(m, struct ip );
333			int hlen = ip->ip_hl << 2;
334			int optlen = hlen - sizeof(struct ip );
335			register struct icmp *icp;
336
337			/*
338			* Send an icmp packet back to the ip level,
339			* after supplying a checksum.
340			*/
341			m->m_data += hlen;
342			m->m_len -= hlen;
343			icp = mtod(m, struct icmp *);
344
345			icp->icmp_cksum = 0;
346			icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
347
348			m->m_data -= hlen;
349			m->m_len += hlen;
350
351			/* fill in ip */
352			if (optlen > 0) {
353			/*
354			* Strip out original options by copying rest of first
355			* mbuf's data back, and adjust the IP length.
356			*/
357			memmove((caddr_t)(ip + 1), (caddr_t)ip + hlen,
358			(unsigned )(m->m_len - hlen));
359			hlen -= optlen;
360			ip->ip_hl = hlen >> 2;
361			ip->ip_len -= optlen;
362			m->m_len -= optlen;
363			}
364
365			ip->ip_ttl = MAXTTL;
366			{ /* swap */
367			struct in_addr icmp_dst;
368			icmp_dst = ip->ip_dst;
369			ip->ip_dst = ip->ip_src;
370			ip->ip_src = icmp_dst;
371			}
372
373			(void ) ip_output((struct socket *)NULL, m);
374
375			icmpstat.icps_reflect++;
376			}