2 * icmpdnd - ICMP Domain Name responder daemon for Linux
3 * Copyright (C) 2005 Fredrik Tolf <fredrik@dolda2000.com>
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
26 #include <sys/socket.h>
28 #include <netinet/in.h>
29 #include <arpa/inet.h>
30 #include <netinet/ip.h>
31 #include <sys/types.h>
56 #define ICMP_NAMEREQ 37
57 #define ICMP_NAMEREP 38
61 size_t filldn(char *dst)
67 if(gethostname(namebuf, sizeof(namebuf)) < 0) {
68 perror("gethostname");
73 if(getdomainname(namebuf + hl, sizeof(namebuf) - hl) < 0) {
74 perror("getdomainname");
77 if(strlen(namebuf + hl) != 0) {
85 while((p2 = strchr(p, '.')) != NULL) {
88 memcpy(dp, p, p2 - p);
97 void cksum(void *hdr, size_t len)
104 ih = (struct icmphdr *)hdr;
105 cb = (u_int8_t *)hdr;
108 for(i = 0; i < (len & ~1); i += 2) {
127 cb = (u_int8_t *)&ih->checksum;
128 cb[0] = ~(u_int8_t)b1;
129 cb[1] = ~(u_int8_t)b2;
132 int main(int argc, char **argv)
135 int c, cs, s4, s6, namelen, datalen;
137 unsigned char buf[65536];
138 struct sockaddr_storage name;
143 struct pollfd pfd[2];
144 time_t curtime, lasterr;
148 while((c = getopt(argc, argv, "nht:")) != -1) {
160 fprintf(stderr, "usage: icmpdnd [-n]");
161 exit((c == 'h')?0:1);
165 s4 = socket(PF_INET, SOCK_RAW, IPPROTO_ICMP);
166 s6 = socket(PF_INET6, SOCK_RAW, IPPROTO_ICMP);
167 if((s4 < 0) && (s6 < 0)) {
168 perror("could not open raw socket");
175 openlog("icmpdnd", LOG_PID | LOG_NDELAY, LOG_DAEMON);
183 pfd[n].events = POLLIN;
188 pfd[n].events = POLLIN;
191 ret = poll(pfd, n, -1);
193 curtime = time(NULL);
197 syslog(LOG_ERR, "error while polling sockets: %m");
198 if(lasterr == curtime) {
199 syslog(LOG_CRIT, "exiting due to repeated errors");
205 for(i = 0; i < n; i++) {
206 if((pfd[i].revents & POLLIN) == 0)
209 namelen = sizeof(name);
210 memset(&name, 0, sizeof(name));
211 ret = recvfrom(cs, buf, sizeof(buf), 0, (struct sockaddr *)&name, &namelen);
213 syslog(LOG_WARNING, "error while receiving datagram: %m");
218 if(ret < sizeof(iphdr) + sizeof(req))
220 hdrlen = sizeof(iphdr);
221 memcpy(&iphdr, buf, sizeof(iphdr));
222 if(iphdr.protocol != IPPROTO_ICMP)
224 } else if(cs == s6) {
225 if(ret < sizeof(req))
227 ((struct sockaddr_in6 *)&name)->sin6_port = 0;
230 syslog(LOG_CRIT, "strangeness!");
233 memcpy(&req, buf + hdrlen, sizeof(req));
234 if(req.type != ICMP_NAMEREQ)
236 rep.type = ICMP_NAMEREP;
240 rep.ttl = htonl(ttl);
241 memcpy(buf, &rep, sizeof(rep));
242 datalen = filldn(buf + sizeof(rep));
244 cksum(buf, datalen + sizeof(rep));
246 /* XXX: The correct source address needs to be filled in from
247 * the request's destination address. */
248 ret = sendto(cs, buf, datalen + sizeof(rep), 0, (struct sockaddr *)&name, namelen);
250 syslog(LOG_WARNING, "error in sending reply: %m");