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