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fa6ac2fc DC |
1 | /* |
2 | * icmpdnd - ICMP Domain Name responder daemon for Linux | |
b39da562 | 3 | * Copyright (C) 2005 Fredrik Tolf <fredrik@dolda2000.com> |
fa6ac2fc DC |
4 | * |
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. | |
9 | * | |
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. | |
14 | * | |
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 | |
18 | */ | |
19 | #include <stdlib.h> | |
20 | #include <unistd.h> | |
21 | #include <stdio.h> | |
22 | #include <string.h> | |
23 | #include <errno.h> | |
b39da562 | 24 | #include <syslog.h> |
dcb0aee6 | 25 | #include <time.h> |
fa6ac2fc | 26 | #include <sys/socket.h> |
6796167f | 27 | #include <sys/poll.h> |
fa6ac2fc DC |
28 | #include <netinet/in.h> |
29 | #include <arpa/inet.h> | |
30 | #include <netinet/ip.h> | |
31 | #include <sys/types.h> | |
606a39c9 | 32 | #ifdef HAVE_CONFIG_H |
2269406c | 33 | #include "config.h" |
606a39c9 | 34 | #endif |
fa6ac2fc | 35 | |
ac46a58c DC |
36 | #ifndef MAXHNAME |
37 | #define MAXHNAME 1024 | |
38 | #endif | |
39 | ||
fa6ac2fc DC |
40 | struct icmphdr { |
41 | u_int8_t type; | |
42 | u_int8_t code; | |
43 | u_int16_t checksum; | |
44 | }; | |
45 | ||
46 | struct reqhdr { | |
47 | u_int8_t type; | |
48 | u_int8_t code; | |
49 | u_int16_t checksum; | |
50 | u_int16_t id; | |
51 | u_int16_t seq; | |
52 | }; | |
53 | ||
54 | struct rephdr { | |
55 | u_int8_t type; | |
56 | u_int8_t code; | |
57 | u_int16_t checksum; | |
58 | u_int16_t id; | |
59 | u_int16_t seq; | |
60 | int32_t ttl; | |
61 | }; | |
62 | ||
63 | #define ICMP_NAMEREQ 37 | |
64 | #define ICMP_NAMEREP 38 | |
65 | ||
fa6ac2fc | 66 | volatile int alive; |
ac46a58c | 67 | char myname[MAXHNAME] = ""; |
fa6ac2fc | 68 | |
ac46a58c | 69 | void setname(char *newname) |
fa6ac2fc | 70 | { |
ac46a58c | 71 | int nl; |
fa6ac2fc | 72 | |
ac46a58c DC |
73 | if(newname == NULL) { |
74 | if(gethostname(myname, sizeof(myname)) < 0) { | |
75 | perror("gethostname"); | |
76 | exit(1); | |
77 | } | |
78 | nl = strlen(myname); | |
79 | myname[nl++] = '.'; | |
80 | if(getdomainname(myname + nl, sizeof(myname) - nl) < 0) { | |
81 | perror("getdomainname"); | |
82 | exit(1); | |
83 | } | |
84 | if(strlen(myname + nl) != 0) { | |
85 | nl = strlen(myname); | |
86 | myname[nl++] = '.'; | |
87 | } | |
88 | myname[nl] = 0; | |
89 | } else { | |
90 | strcpy(myname, newname); | |
91 | nl = strlen(myname); | |
92 | if(myname[nl - 1] != '.') { | |
93 | myname[nl] = '.'; | |
94 | myname[nl + 1] = 0; | |
95 | } | |
fa6ac2fc | 96 | } |
ac46a58c DC |
97 | } |
98 | ||
99 | size_t filldn(char *dst) | |
100 | { | |
101 | char *p, *p2, *dp; | |
102 | char namebuf[MAXHNAME]; | |
fa6ac2fc | 103 | |
ac46a58c | 104 | strcpy(namebuf, myname); |
fa6ac2fc DC |
105 | p = namebuf; |
106 | dp = dst; | |
107 | while((p2 = strchr(p, '.')) != NULL) { | |
108 | *p2 = 0; | |
109 | *(dp++) = p2 - p; | |
110 | memcpy(dp, p, p2 - p); | |
111 | dp += p2 - p; | |
112 | p = p2 + 1; | |
113 | } | |
114 | *(dp++) = 0; | |
115 | ||
116 | return(dp - dst); | |
117 | } | |
118 | ||
119 | void cksum(void *hdr, size_t len) | |
120 | { | |
121 | struct icmphdr *ih; | |
122 | u_int8_t *cb; | |
123 | int i; | |
124 | int b1, b2; | |
125 | ||
126 | ih = (struct icmphdr *)hdr; | |
127 | cb = (u_int8_t *)hdr; | |
128 | ih->checksum = 0; | |
129 | b1 = b2 = 0; | |
130 | for(i = 0; i < (len & ~1); i += 2) { | |
131 | b1 += cb[i]; | |
132 | b2 += cb[i + 1]; | |
133 | } | |
134 | if(i & 1) | |
135 | b1 += cb[len - 1]; | |
136 | while(1) { | |
137 | if(b1 >= 256) { | |
138 | b2 += b1 >> 8; | |
139 | b1 &= 0xff; | |
140 | continue; | |
141 | } | |
142 | if(b2 >= 256) { | |
143 | b1 += b2 >> 8; | |
144 | b2 &= 0xff; | |
145 | continue; | |
146 | } | |
147 | break; | |
148 | } | |
149 | cb = (u_int8_t *)&ih->checksum; | |
150 | cb[0] = ~(u_int8_t)b1; | |
151 | cb[1] = ~(u_int8_t)b2; | |
152 | } | |
153 | ||
154 | int main(int argc, char **argv) | |
155 | { | |
6796167f | 156 | int i, n, ret; |
df4e01a5 | 157 | int c, cs, s4, s6, datalen; |
b39da562 | 158 | int daemonize, ttl; |
fa6ac2fc | 159 | unsigned char buf[65536]; |
6796167f | 160 | struct sockaddr_storage name; |
fa6ac2fc DC |
161 | struct reqhdr req; |
162 | struct rephdr rep; | |
163 | struct iphdr iphdr; | |
df4e01a5 DC |
164 | struct msghdr mhdr; |
165 | struct iovec iov; | |
166 | char cmsgbuf[CMSG_SPACE(sizeof(struct in6_pktinfo))]; | |
6796167f DC |
167 | size_t hdrlen; |
168 | struct pollfd pfd[2]; | |
dcb0aee6 | 169 | time_t curtime, lasterr; |
b39da562 DC |
170 | |
171 | daemonize = 1; | |
172 | ttl = 3600; | |
ac46a58c | 173 | while((c = getopt(argc, argv, "nht:d:")) != -1) { |
b39da562 DC |
174 | switch(c) { |
175 | case 't': | |
176 | ttl = atoi(optarg); | |
177 | break; | |
ac46a58c DC |
178 | case 'd': |
179 | setname(optarg); | |
180 | break; | |
b39da562 DC |
181 | case 'n': |
182 | daemonize = 0; | |
183 | break; | |
184 | case 'h': | |
185 | case '?': | |
186 | case ':': | |
187 | default: | |
4ca7c46f | 188 | fprintf(stderr, "usage: icmpdnd [-nh] [-t ttl] [-d domainname]\n"); |
b39da562 DC |
189 | exit((c == 'h')?0:1); |
190 | } | |
191 | } | |
ac46a58c DC |
192 | if(*myname == 0) |
193 | setname(NULL); | |
b39da562 | 194 | |
6796167f DC |
195 | s4 = socket(PF_INET, SOCK_RAW, IPPROTO_ICMP); |
196 | s6 = socket(PF_INET6, SOCK_RAW, IPPROTO_ICMP); | |
197 | if((s4 < 0) && (s6 < 0)) { | |
198 | perror("could not open raw socket"); | |
fa6ac2fc DC |
199 | exit(1); |
200 | } | |
df4e01a5 DC |
201 | if(s6 >= 0) { |
202 | i = 1; | |
203 | if(setsockopt(s6, IPPROTO_IPV6, IPV6_PKTINFO, &i, sizeof(i))) { | |
204 | perror("could not set IPV6_PKTINFO sockopt"); | |
205 | exit(1); | |
206 | } | |
207 | } | |
fa6ac2fc | 208 | |
b39da562 DC |
209 | if(daemonize) |
210 | daemon(0, 0); | |
211 | ||
6796167f | 212 | openlog("icmpdnd", LOG_PID | LOG_NDELAY, LOG_DAEMON); |
b39da562 | 213 | |
fa6ac2fc | 214 | alive = 1; |
dcb0aee6 | 215 | lasterr = 0; |
fa6ac2fc | 216 | while(alive) { |
6796167f DC |
217 | n = 0; |
218 | if(s4 >= 0) { | |
219 | pfd[n].fd = s4; | |
220 | pfd[n].events = POLLIN; | |
221 | n++; | |
222 | } | |
223 | if(s6 >= 0) { | |
224 | pfd[n].fd = s6; | |
225 | pfd[n].events = POLLIN; | |
226 | n++; | |
227 | } | |
228 | ret = poll(pfd, n, -1); | |
229 | ||
dcb0aee6 | 230 | curtime = time(NULL); |
fa6ac2fc DC |
231 | if(ret < 0) { |
232 | if(errno == EINTR) | |
233 | continue; | |
6796167f | 234 | syslog(LOG_ERR, "error while polling sockets: %m"); |
dcb0aee6 DC |
235 | if(lasterr == curtime) { |
236 | syslog(LOG_CRIT, "exiting due to repeated errors"); | |
237 | exit(1); | |
238 | } | |
239 | lasterr = curtime; | |
fa6ac2fc | 240 | } |
dcb0aee6 | 241 | |
6796167f DC |
242 | for(i = 0; i < n; i++) { |
243 | if((pfd[i].revents & POLLIN) == 0) | |
244 | continue; | |
245 | cs = pfd[i].fd; | |
6796167f | 246 | memset(&name, 0, sizeof(name)); |
df4e01a5 DC |
247 | |
248 | iov.iov_len = sizeof(buf); | |
249 | iov.iov_base = buf; | |
250 | mhdr.msg_name = &name; | |
251 | mhdr.msg_namelen = sizeof(name); | |
252 | mhdr.msg_iov = &iov; | |
253 | mhdr.msg_iovlen = 1; | |
254 | mhdr.msg_control = cmsgbuf; | |
255 | mhdr.msg_controllen = sizeof(cmsgbuf); | |
256 | ||
257 | ret = recvmsg(cs, &mhdr, 0); | |
6796167f DC |
258 | if(ret < 0) { |
259 | syslog(LOG_WARNING, "error while receiving datagram: %m"); | |
260 | continue; | |
261 | } | |
262 | ||
263 | if(cs == s4) { | |
264 | if(ret < sizeof(iphdr) + sizeof(req)) | |
265 | continue; | |
266 | hdrlen = sizeof(iphdr); | |
267 | memcpy(&iphdr, buf, sizeof(iphdr)); | |
268 | if(iphdr.protocol != IPPROTO_ICMP) | |
269 | continue; | |
df4e01a5 DC |
270 | mhdr.msg_control = NULL; |
271 | mhdr.msg_controllen = 0; | |
6796167f DC |
272 | } else if(cs == s6) { |
273 | if(ret < sizeof(req)) | |
274 | continue; | |
275 | ((struct sockaddr_in6 *)&name)->sin6_port = 0; | |
276 | hdrlen = 0; | |
df4e01a5 | 277 | /* Just keep mhdr.msg_control. */ |
6796167f DC |
278 | } else { |
279 | syslog(LOG_CRIT, "strangeness!"); | |
280 | abort(); | |
281 | } | |
282 | memcpy(&req, buf + hdrlen, sizeof(req)); | |
283 | if(req.type != ICMP_NAMEREQ) | |
284 | continue; | |
285 | rep.type = ICMP_NAMEREP; | |
286 | rep.code = 0; | |
287 | rep.id = req.id; | |
288 | rep.seq = req.seq; | |
289 | rep.ttl = htonl(ttl); | |
290 | memcpy(buf, &rep, sizeof(rep)); | |
291 | datalen = filldn(buf + sizeof(rep)); | |
b39da562 | 292 | |
6796167f | 293 | cksum(buf, datalen + sizeof(rep)); |
df4e01a5 DC |
294 | |
295 | iov.iov_len = sizeof(rep) + datalen; | |
296 | iov.iov_base = buf; | |
297 | mhdr.msg_iov = &iov; | |
298 | mhdr.msg_iovlen = 1; | |
299 | ret = sendmsg(cs, &mhdr, 0); | |
6796167f DC |
300 | if(ret < 0) |
301 | syslog(LOG_WARNING, "error in sending reply: %m"); | |
302 | } | |
fa6ac2fc DC |
303 | } |
304 | ||
6796167f DC |
305 | close(s4); |
306 | close(s6); | |
fa6ac2fc DC |
307 | return(0); |
308 | } | |
f82409dd DC |
309 | |
310 | /* | |
311 | * Local Variables: | |
ac46a58c | 312 | * compile-command: "make CFLAGS='-Wall -g'" |
f82409dd DC |
313 | * End: |
314 | */ |