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