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6 * modification, are permitted provided that the following conditions
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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
36 /* The message sent when emulating PING */
37 /* Be nice and tell them it's just a pseudo-ping packet */
38 static const char icmp_ping_msg[] = "This is a pseudo-PING packet used by Slirp to emulate ICMP ECHO-REQUEST packets.\n";
40 /* list of actions for icmp_error() on RX of an icmp message */
41 static const int icmp_flush[19] = {
42 /* ECHO REPLY (0) */ 0,
45 /* DEST UNREACH (3) */ 1,
46 /* SOURCE QUENCH (4)*/ 1,
51 /* ROUTERADVERT (9) */ 1,
52 /* ROUTERSOLICIT (10) */ 1,
53 /* TIME EXCEEDED (11) */ 1,
54 /* PARAMETER PROBLEM (12) */ 1,
55 /* TIMESTAMP (13) */ 0,
56 /* TIMESTAMP REPLY (14) */ 0,
58 /* INFO REPLY (16) */ 0,
59 /* ADDR MASK (17) */ 0,
60 /* ADDR MASK REPLY (18) */ 0
64 * Process a received ICMP message.
67 icmp_input(struct mbuf *m, int hlen)
69 register struct icmp *icp;
70 register struct ip *ip=mtod(m, struct ip *);
71 int icmplen=ip->ip_len;
72 Slirp *slirp = m->slirp;
74 DEBUG_CALL("icmp_input");
75 DEBUG_ARG("m = %lx", (long )m);
76 DEBUG_ARG("m_len = %d", m->m_len);
79 * Locate icmp structure in mbuf, and check
80 * that its not corrupted and of at least minimum length.
82 if (icmplen < ICMP_MINLEN) { /* min 8 bytes payload */
90 icp = mtod(m, struct icmp *);
91 if (cksum(m, icmplen)) {
97 DEBUG_ARG("icmp_type = %d", icp->icmp_type);
98 switch (icp->icmp_type) {
100 icp->icmp_type = ICMP_ECHOREPLY;
101 ip->ip_len += hlen; /* since ip_input subtracts this */
102 if (ip->ip_dst.s_addr == slirp->vhost_addr.s_addr) {
106 struct sockaddr_in addr;
107 if ((so = socreate(slirp)) == NULL) goto freeit;
108 if(udp_attach(so) == -1) {
109 DEBUG_MISC((dfd,"icmp_input udp_attach errno = %d-%s\n",
110 errno,strerror(errno)));
116 so->so_faddr = ip->ip_dst;
117 so->so_fport = htons(7);
118 so->so_laddr = ip->ip_src;
119 so->so_lport = htons(9);
120 so->so_iptos = ip->ip_tos;
121 so->so_type = IPPROTO_ICMP;
122 so->so_state = SS_ISFCONNECTED;
124 /* Send the packet */
125 addr.sin_family = AF_INET;
126 if ((so->so_faddr.s_addr & slirp->vnetwork_mask.s_addr) ==
127 slirp->vnetwork_addr.s_addr) {
129 if (so->so_faddr.s_addr == slirp->vnameserver_addr.s_addr) {
130 if (get_dns_addr(&addr.sin_addr) < 0)
131 addr.sin_addr = loopback_addr;
133 addr.sin_addr = loopback_addr;
136 addr.sin_addr = so->so_faddr;
138 addr.sin_port = so->so_fport;
139 if(sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
140 (struct sockaddr *)&addr, sizeof(addr)) == -1) {
141 DEBUG_MISC((dfd,"icmp_input udp sendto tx errno = %d-%s\n",
142 errno,strerror(errno)));
143 icmp_error(m, ICMP_UNREACH,ICMP_UNREACH_NET, 0,strerror(errno));
146 } /* if ip->ip_dst.s_addr == alias_addr.s_addr */
149 /* XXX? report error? close socket? */
152 case ICMP_SOURCEQUENCH:
164 /* m is m_free()'d xor put in a socket xor or given to ip_send */
170 * Send an ICMP message in response to a situation
172 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
173 * MUST NOT change this header information.
174 * MUST NOT reply to a multicast/broadcast IP address.
175 * MUST NOT reply to a multicast/broadcast MAC address.
176 * MUST reply to only the first fragment.
179 * Send ICMP_UNREACH back to the source regarding msrc.
180 * mbuf *msrc is used as a template, but is NOT m_free()'d.
181 * It is reported as the bad ip packet. The header should
182 * be fully correct and in host byte order.
183 * ICMP fragmentation is illegal. All machines must accept 576 bytes in one
184 * packet. The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
187 #define ICMP_MAXDATALEN (IP_MSS-28)
189 icmp_error(struct mbuf *msrc, u_char type, u_char code, int minsize,
192 unsigned hlen, shlen, s_ip_len;
193 register struct ip *ip;
194 register struct icmp *icp;
195 register struct mbuf *m;
197 DEBUG_CALL("icmp_error");
198 DEBUG_ARG("msrc = %lx", (long )msrc);
199 DEBUG_ARG("msrc_len = %d", msrc->m_len);
201 if(type!=ICMP_UNREACH && type!=ICMP_TIMXCEED) goto end_error;
204 if(!msrc) goto end_error;
205 ip = mtod(msrc, struct ip *);
207 { char bufa[20], bufb[20];
208 strcpy(bufa, inet_ntoa(ip->ip_src));
209 strcpy(bufb, inet_ntoa(ip->ip_dst));
210 DEBUG_MISC((dfd, " %.16s to %.16s\n", bufa, bufb));
213 if(ip->ip_off & IP_OFFMASK) goto end_error; /* Only reply to fragment 0 */
215 shlen=ip->ip_hl << 2;
217 if(ip->ip_p == IPPROTO_ICMP) {
218 icp = (struct icmp *)((char *)ip + shlen);
220 * Assume any unknown ICMP type is an error. This isn't
221 * specified by the RFC, but think about it..
223 if(icp->icmp_type>18 || icmp_flush[icp->icmp_type]) goto end_error;
227 m = m_get(msrc->slirp);
233 new_m_size=sizeof(struct ip )+ICMP_MINLEN+msrc->m_len+ICMP_MAXDATALEN;
234 if(new_m_size>m->m_size) m_inc(m, new_m_size);
236 memcpy(m->m_data, msrc->m_data, msrc->m_len);
237 m->m_len = msrc->m_len; /* copy msrc to m */
239 /* make the header of the reply packet */
240 ip = mtod(m, struct ip *);
241 hlen= sizeof(struct ip ); /* no options in reply */
247 icp = mtod(m, struct icmp *);
249 if(minsize) s_ip_len=shlen+ICMP_MINLEN; /* return header+8b only */
250 else if(s_ip_len>ICMP_MAXDATALEN) /* maximum size */
251 s_ip_len=ICMP_MAXDATALEN;
253 m->m_len=ICMP_MINLEN+s_ip_len; /* 8 bytes ICMP header */
255 /* min. size = 8+sizeof(struct ip)+8 */
257 icp->icmp_type = type;
258 icp->icmp_code = code;
262 memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len); /* report the ip packet */
263 HTONS(icp->icmp_ip.ip_len);
264 HTONS(icp->icmp_ip.ip_id);
265 HTONS(icp->icmp_ip.ip_off);
268 if(message) { /* DEBUG : append message to ICMP packet */
271 message_len=strlen(message);
272 if(message_len>ICMP_MAXDATALEN) message_len=ICMP_MAXDATALEN;
273 cpnt=(char *)m->m_data+m->m_len;
274 memcpy(cpnt, message, message_len);
275 m->m_len+=message_len;
280 icp->icmp_cksum = cksum(m, m->m_len);
286 ip->ip_hl = hlen >> 2;
287 ip->ip_len = m->m_len;
289 ip->ip_tos=((ip->ip_tos & 0x1E) | 0xC0); /* high priority for errors */
292 ip->ip_p = IPPROTO_ICMP;
293 ip->ip_dst = ip->ip_src; /* ip adresses */
294 ip->ip_src = m->slirp->vhost_addr;
296 (void ) ip_output((struct socket *)NULL, m);
301 #undef ICMP_MAXDATALEN
304 * Reflect the ip packet back to the source
307 icmp_reflect(struct mbuf *m)
309 register struct ip *ip = mtod(m, struct ip *);
310 int hlen = ip->ip_hl << 2;
311 int optlen = hlen - sizeof(struct ip );
312 register struct icmp *icp;
315 * Send an icmp packet back to the ip level,
316 * after supplying a checksum.
320 icp = mtod(m, struct icmp *);
323 icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
331 * Strip out original options by copying rest of first
332 * mbuf's data back, and adjust the IP length.
334 memmove((caddr_t)(ip + 1), (caddr_t)ip + hlen,
335 (unsigned )(m->m_len - hlen));
337 ip->ip_hl = hlen >> 2;
338 ip->ip_len -= optlen;
344 struct in_addr icmp_dst;
345 icmp_dst = ip->ip_dst;
346 ip->ip_dst = ip->ip_src;
347 ip->ip_src = icmp_dst;
350 (void ) ip_output((struct socket *)NULL, m);