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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;
73 DEBUG_CALL("icmp_input");
74 DEBUG_ARG("m = %lx", (long )m);
75 DEBUG_ARG("m_len = %d", m->m_len);
78 * Locate icmp structure in mbuf, and check
79 * that its not corrupted and of at least minimum length.
81 if (icmplen < ICMP_MINLEN) { /* min 8 bytes payload */
89 icp = mtod(m, struct icmp *);
90 if (cksum(m, icmplen)) {
96 DEBUG_ARG("icmp_type = %d", icp->icmp_type);
97 switch (icp->icmp_type) {
99 icp->icmp_type = ICMP_ECHOREPLY;
100 ip->ip_len += hlen; /* since ip_input subtracts this */
101 if (ip->ip_dst.s_addr == vhost_addr.s_addr) {
105 struct sockaddr_in addr;
106 if ((so = socreate()) == NULL) goto freeit;
107 if(udp_attach(so) == -1) {
108 DEBUG_MISC((dfd,"icmp_input udp_attach errno = %d-%s\n",
109 errno,strerror(errno)));
115 so->so_faddr = ip->ip_dst;
116 so->so_fport = htons(7);
117 so->so_laddr = ip->ip_src;
118 so->so_lport = htons(9);
119 so->so_iptos = ip->ip_tos;
120 so->so_type = IPPROTO_ICMP;
121 so->so_state = SS_ISFCONNECTED;
123 /* Send the packet */
124 addr.sin_family = AF_INET;
125 if ((so->so_faddr.s_addr & vnetwork_mask.s_addr) ==
126 vnetwork_addr.s_addr) {
128 if (so->so_faddr.s_addr == vnameserver_addr.s_addr) {
129 addr.sin_addr = dns_addr;
131 addr.sin_addr = loopback_addr;
134 addr.sin_addr = so->so_faddr;
136 addr.sin_port = so->so_fport;
137 if(sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
138 (struct sockaddr *)&addr, sizeof(addr)) == -1) {
139 DEBUG_MISC((dfd,"icmp_input udp sendto tx errno = %d-%s\n",
140 errno,strerror(errno)));
141 icmp_error(m, ICMP_UNREACH,ICMP_UNREACH_NET, 0,strerror(errno));
144 } /* if ip->ip_dst.s_addr == alias_addr.s_addr */
147 /* XXX? report error? close socket? */
150 case ICMP_SOURCEQUENCH:
162 /* m is m_free()'d xor put in a socket xor or given to ip_send */
168 * Send an ICMP message in response to a situation
170 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
171 * MUST NOT change this header information.
172 * MUST NOT reply to a multicast/broadcast IP address.
173 * MUST NOT reply to a multicast/broadcast MAC address.
174 * MUST reply to only the first fragment.
177 * Send ICMP_UNREACH back to the source regarding msrc.
178 * mbuf *msrc is used as a template, but is NOT m_free()'d.
179 * It is reported as the bad ip packet. The header should
180 * be fully correct and in host byte order.
181 * ICMP fragmentation is illegal. All machines must accept 576 bytes in one
182 * packet. The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
185 #define ICMP_MAXDATALEN (IP_MSS-28)
187 icmp_error(struct mbuf *msrc, u_char type, u_char code, int minsize,
190 unsigned hlen, shlen, s_ip_len;
191 register struct ip *ip;
192 register struct icmp *icp;
193 register struct mbuf *m;
195 DEBUG_CALL("icmp_error");
196 DEBUG_ARG("msrc = %lx", (long )msrc);
197 DEBUG_ARG("msrc_len = %d", msrc->m_len);
199 if(type!=ICMP_UNREACH && type!=ICMP_TIMXCEED) goto end_error;
202 if(!msrc) goto end_error;
203 ip = mtod(msrc, struct ip *);
205 { char bufa[20], bufb[20];
206 strcpy(bufa, inet_ntoa(ip->ip_src));
207 strcpy(bufb, inet_ntoa(ip->ip_dst));
208 DEBUG_MISC((dfd, " %.16s to %.16s\n", bufa, bufb));
211 if(ip->ip_off & IP_OFFMASK) goto end_error; /* Only reply to fragment 0 */
213 shlen=ip->ip_hl << 2;
215 if(ip->ip_p == IPPROTO_ICMP) {
216 icp = (struct icmp *)((char *)ip + shlen);
218 * Assume any unknown ICMP type is an error. This isn't
219 * specified by the RFC, but think about it..
221 if(icp->icmp_type>18 || icmp_flush[icp->icmp_type]) goto end_error;
225 if(!(m=m_get())) goto end_error; /* get mbuf */
227 new_m_size=sizeof(struct ip )+ICMP_MINLEN+msrc->m_len+ICMP_MAXDATALEN;
228 if(new_m_size>m->m_size) m_inc(m, new_m_size);
230 memcpy(m->m_data, msrc->m_data, msrc->m_len);
231 m->m_len = msrc->m_len; /* copy msrc to m */
233 /* make the header of the reply packet */
234 ip = mtod(m, struct ip *);
235 hlen= sizeof(struct ip ); /* no options in reply */
241 icp = mtod(m, struct icmp *);
243 if(minsize) s_ip_len=shlen+ICMP_MINLEN; /* return header+8b only */
244 else if(s_ip_len>ICMP_MAXDATALEN) /* maximum size */
245 s_ip_len=ICMP_MAXDATALEN;
247 m->m_len=ICMP_MINLEN+s_ip_len; /* 8 bytes ICMP header */
249 /* min. size = 8+sizeof(struct ip)+8 */
251 icp->icmp_type = type;
252 icp->icmp_code = code;
256 memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len); /* report the ip packet */
257 HTONS(icp->icmp_ip.ip_len);
258 HTONS(icp->icmp_ip.ip_id);
259 HTONS(icp->icmp_ip.ip_off);
262 if(message) { /* DEBUG : append message to ICMP packet */
265 message_len=strlen(message);
266 if(message_len>ICMP_MAXDATALEN) message_len=ICMP_MAXDATALEN;
267 cpnt=(char *)m->m_data+m->m_len;
268 memcpy(cpnt, message, message_len);
269 m->m_len+=message_len;
274 icp->icmp_cksum = cksum(m, m->m_len);
280 ip->ip_hl = hlen >> 2;
281 ip->ip_len = m->m_len;
283 ip->ip_tos=((ip->ip_tos & 0x1E) | 0xC0); /* high priority for errors */
286 ip->ip_p = IPPROTO_ICMP;
287 ip->ip_dst = ip->ip_src; /* ip adresses */
288 ip->ip_src = vhost_addr;
290 (void ) ip_output((struct socket *)NULL, m);
295 #undef ICMP_MAXDATALEN
298 * Reflect the ip packet back to the source
301 icmp_reflect(struct mbuf *m)
303 register struct ip *ip = mtod(m, struct ip *);
304 int hlen = ip->ip_hl << 2;
305 int optlen = hlen - sizeof(struct ip );
306 register struct icmp *icp;
309 * Send an icmp packet back to the ip level,
310 * after supplying a checksum.
314 icp = mtod(m, struct icmp *);
317 icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
325 * Strip out original options by copying rest of first
326 * mbuf's data back, and adjust the IP length.
328 memmove((caddr_t)(ip + 1), (caddr_t)ip + hlen,
329 (unsigned )(m->m_len - hlen));
331 ip->ip_hl = hlen >> 2;
332 ip->ip_len -= optlen;
338 struct in_addr icmp_dst;
339 icmp_dst = ip->ip_dst;
340 ip->ip_dst = ip->ip_src;
341 ip->ip_src = icmp_dst;
344 (void ) ip_output((struct socket *)NULL, m);