Detection of multicast IPv4 addresses was looking at the wrong end.
[darkstat] / dns.c
1 /* darkstat 3
2 * copyright (c) 2001-2011 Emil Mikulic.
3 *
4 * dns.c: synchronous DNS in a child process.
5 *
6 * You may use, modify and redistribute this file under the terms of the
7 * GNU General Public License version 2. (see COPYING.GPL)
8 */
9
10 #include "cdefs.h"
11 #include "conv.h"
12 #include "decode.h"
13 #include "dns.h"
14 #include "err.h"
15 #include "hosts_db.h"
16 #include "queue.h"
17 #include "str.h"
18 #include "tree.h"
19 #include "bsd.h" /* for setproctitle, strlcpy */
20
21 #include <sys/param.h>
22 #include <sys/socket.h>
23 #include <sys/wait.h>
24 #include <assert.h>
25 #include <errno.h>
26 #include <netdb.h>
27 #include <signal.h>
28 #include <stdlib.h>
29 #include <string.h>
30 #include <unistd.h>
31
32 static void dns_main(void) _noreturn_; /* the child process runs this */
33
34 #define CHILD 0 /* child process uses this socket */
35 #define PARENT 1
36 static int sock[2];
37 static pid_t pid = -1;
38
39 struct dns_reply {
40 struct addr addr;
41 int error; /* for gai_strerror(), or 0 if no error */
42 char name[256]; /* http://tools.ietf.org/html/rfc1034#section-3.1 */
43 };
44
45 void
46 dns_init(const char *privdrop_user)
47 {
48 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sock) == -1)
49 err(1, "socketpair");
50
51 pid = fork();
52 if (pid == -1)
53 err(1, "fork");
54
55 if (pid == 0) {
56 /* We are the child. */
57 privdrop(NULL /* don't chroot */, privdrop_user);
58 close(sock[PARENT]);
59 sock[PARENT] = -1;
60 daemonize_finish(); /* drop our copy of the lifeline! */
61 if (signal(SIGUSR1, SIG_IGN) == SIG_ERR)
62 errx(1, "signal(SIGUSR1, ignore) failed");
63 dns_main();
64 verbosef("fell out of dns_main()");
65 exit(0);
66 } else {
67 /* We are the parent. */
68 close(sock[CHILD]);
69 sock[CHILD] = -1;
70 fd_set_nonblock(sock[PARENT]);
71 verbosef("DNS child has PID %d", pid);
72 }
73 }
74
75 void
76 dns_stop(void)
77 {
78 if (pid == -1)
79 return; /* no child was started */
80 close(sock[PARENT]);
81 if (kill(pid, SIGINT) == -1)
82 err(1, "kill");
83 verbosef("dns_stop() waiting for child");
84 if (waitpid(pid, NULL, 0) == -1)
85 err(1, "waitpid");
86 verbosef("dns_stop() done waiting for child");
87 }
88
89 struct tree_rec {
90 RB_ENTRY(tree_rec) ptree;
91 struct addr ip;
92 };
93
94 static int
95 tree_cmp(struct tree_rec *a, struct tree_rec *b)
96 {
97 if (a->ip.family != b->ip.family)
98 /* Sort IPv4 to the left of IPv6. */
99 return ((a->ip.family == IPv4) ? -1 : +1);
100
101 if (a->ip.family == IPv4)
102 return (memcmp(&a->ip.ip.v4, &b->ip.ip.v4, sizeof(a->ip.ip.v4)));
103 else {
104 assert(a->ip.family == IPv6);
105 return (memcmp(&a->ip.ip.v6, &b->ip.ip.v6, sizeof(a->ip.ip.v6)));
106 }
107 }
108
109 static RB_HEAD(tree_t, tree_rec) ip_tree = RB_INITIALIZER(&tree_rec);
110 /* Quiet warnings. */
111 static struct tree_rec * tree_t_RB_NEXT(struct tree_rec *elm)
112 _unused_;
113 static struct tree_rec * tree_t_RB_MINMAX(struct tree_t *head, int val)
114 _unused_;
115 RB_GENERATE(tree_t, tree_rec, ptree, tree_cmp)
116
117 void
118 dns_queue(const struct addr *const ipaddr)
119 {
120 struct tree_rec *rec;
121 ssize_t num_w;
122
123 if (pid == -1)
124 return; /* no child was started - we're not doing any DNS */
125
126 if ((ipaddr->family != IPv4) && (ipaddr->family != IPv6)) {
127 verbosef("dns_queue() for unknown family %d", ipaddr->family);
128 return;
129 }
130
131 rec = xmalloc(sizeof(*rec));
132 memcpy(&rec->ip, ipaddr, sizeof(rec->ip));
133
134 if (RB_INSERT(tree_t, &ip_tree, rec) != NULL) {
135 /* Already queued - this happens seldom enough that we don't care about
136 * the performance hit of needlessly malloc()ing. */
137 verbosef("already queued %s", addr_to_str(ipaddr));
138 free(rec);
139 return;
140 }
141
142 num_w = write(sock[PARENT], ipaddr, sizeof(*ipaddr)); /* won't block */
143 if (num_w == 0)
144 warnx("dns_queue: write: ignoring end of file");
145 else if (num_w == -1)
146 warn("dns_queue: ignoring write error");
147 else if (num_w != sizeof(*ipaddr))
148 err(1, "dns_queue: wrote %zu instead of %zu", num_w, sizeof(*ipaddr));
149 }
150
151 static void
152 dns_unqueue(const struct addr *const ipaddr)
153 {
154 struct tree_rec tmp, *rec;
155
156 memcpy(&tmp.ip, ipaddr, sizeof(tmp.ip));
157 if ((rec = RB_FIND(tree_t, &ip_tree, &tmp)) != NULL) {
158 RB_REMOVE(tree_t, &ip_tree, rec);
159 free(rec);
160 }
161 else
162 verbosef("couldn't unqueue %s - not in queue!", addr_to_str(ipaddr));
163 }
164
165 /*
166 * Returns non-zero if result waiting, stores IP and name into given pointers
167 * (name buffer is allocated by dns_poll)
168 */
169 static int
170 dns_get_result(struct addr *ipaddr, char **name)
171 {
172 struct dns_reply reply;
173 ssize_t numread;
174
175 numread = read(sock[PARENT], &reply, sizeof(reply));
176 if (numread == -1) {
177 if (errno == EAGAIN)
178 return (0); /* no input waiting */
179 else
180 goto error;
181 }
182 if (numread == 0)
183 goto error; /* EOF */
184 if (numread != sizeof(reply))
185 errx(1, "dns_get_result read got %zu, expected %zu",
186 numread, sizeof(reply));
187
188 /* Return successful reply. */
189 memcpy(ipaddr, &reply.addr, sizeof(*ipaddr));
190 if (reply.error != 0) {
191 /* Identify common special cases. */
192 const char *type = "none";
193
194 switch (reply.addr.family) {
195 case IPv6:
196 if (IN6_IS_ADDR_LINKLOCAL(&reply.addr.ip.v6))
197 type = "link-local";
198 else if (IN6_IS_ADDR_SITELOCAL(&reply.addr.ip.v6))
199 type = "site-local";
200 else if (IN6_IS_ADDR_MULTICAST(&reply.addr.ip.v6))
201 type = "multicast";
202 break;
203 case IPv4:
204 if (IN_MULTICAST(htonl(reply.addr.ip.v4)))
205 type = "multicast";
206 }
207 xasprintf(name, "(%s)", type);
208 }
209 else /* Correctly resolved name. */
210 *name = xstrdup(reply.name);
211
212 dns_unqueue(&reply.addr);
213 return (1);
214
215 error:
216 warn("dns_get_result: ignoring read error");
217 /* FIXME: re-align to stream? restart dns child? */
218 return (0);
219 }
220
221 void
222 dns_poll(void)
223 {
224 struct addr ip;
225 char *name;
226
227 if (pid == -1)
228 return; /* no child was started - we're not doing any DNS */
229
230 while (dns_get_result(&ip, &name)) {
231 /* push into hosts_db */
232 struct bucket *b = host_find(&ip);
233
234 if (b == NULL) {
235 verbosef("resolved %s to %s but it's not in the DB!",
236 addr_to_str(&ip), name);
237 return;
238 }
239 if (b->u.host.dns != NULL) {
240 verbosef("resolved %s to %s but it's already in the DB!",
241 addr_to_str(&ip), name);
242 return;
243 }
244 b->u.host.dns = name;
245 }
246 }
247
248 /* ------------------------------------------------------------------------ */
249
250 struct qitem {
251 STAILQ_ENTRY(qitem) entries;
252 struct addr ip;
253 };
254
255 STAILQ_HEAD(qhead, qitem) queue = STAILQ_HEAD_INITIALIZER(queue);
256
257 static void
258 enqueue(const struct addr *const ip)
259 {
260 struct qitem *i;
261
262 i = xmalloc(sizeof(*i));
263 memcpy(&i->ip, ip, sizeof(i->ip));
264 STAILQ_INSERT_TAIL(&queue, i, entries);
265 verbosef("DNS: enqueued %s", addr_to_str(ip));
266 }
267
268 /* Return non-zero and populate <ip> pointer if queue isn't empty. */
269 static int
270 dequeue(struct addr *ip)
271 {
272 struct qitem *i;
273
274 i = STAILQ_FIRST(&queue);
275 if (i == NULL)
276 return (0);
277 STAILQ_REMOVE_HEAD(&queue, entries);
278 memcpy(ip, &i->ip, sizeof(*ip));
279 free(i);
280 verbosef("DNS: dequeued %s", addr_to_str(ip));
281 return 1;
282 }
283
284 static void
285 xwrite(const int d, const void *buf, const size_t nbytes)
286 {
287 ssize_t ret = write(d, buf, nbytes);
288
289 if (ret == -1)
290 err(1, "write");
291 if (ret != (ssize_t)nbytes)
292 err(1, "wrote %d bytes instead of all %d bytes", (int)ret, (int)nbytes);
293 }
294
295 static void
296 dns_main(void)
297 {
298 struct addr ip;
299
300 setproctitle("DNS child");
301 fd_set_nonblock(sock[CHILD]);
302 verbosef("DNS child entering main DNS loop");
303 for (;;) {
304 int blocking;
305
306 if (STAILQ_EMPTY(&queue)) {
307 blocking = 1;
308 fd_set_block(sock[CHILD]);
309 verbosef("entering blocking read loop");
310 } else {
311 blocking = 0;
312 fd_set_nonblock(sock[CHILD]);
313 verbosef("non-blocking poll");
314 }
315 for (;;) {
316 /* While we have input to process... */
317 ssize_t numread = read(sock[CHILD], &ip, sizeof(ip));
318 if (numread == 0)
319 exit(0); /* end of file, nothing more to do here. */
320 if (numread == -1) {
321 if (!blocking && (errno == EAGAIN))
322 break; /* ran out of input */
323 /* else error */
324 err(1, "DNS: read failed");
325 }
326 if (numread != sizeof(ip))
327 err(1, "DNS: read got %zu bytes, expecting %zu",
328 numread, sizeof(ip));
329 enqueue(&ip);
330 if (blocking) {
331 /* After one blocking read, become non-blocking so that when we
332 * run out of input we fall through to queue processing.
333 */
334 blocking = 0;
335 fd_set_nonblock(sock[CHILD]);
336 }
337 }
338
339 /* Process queue. */
340 if (dequeue(&ip)) {
341 struct dns_reply reply;
342 struct sockaddr_in sin;
343 struct sockaddr_in6 sin6;
344 struct hostent *he;
345 char host[NI_MAXHOST];
346 int ret, flags;
347
348 reply.addr = ip;
349 flags = NI_NAMEREQD;
350 # ifdef NI_IDN
351 flags |= NI_IDN;
352 # endif
353 switch (ip.family) {
354 case IPv4:
355 sin.sin_family = AF_INET;
356 sin.sin_addr.s_addr = ip.ip.v4;
357 ret = getnameinfo((struct sockaddr *) &sin, sizeof(sin),
358 host, sizeof(host), NULL, 0, flags);
359 if (ret == EAI_FAMILY) {
360 verbosef("getnameinfo error %s, trying gethostbyname",
361 gai_strerror(ret));
362 he = gethostbyaddr(&sin.sin_addr.s_addr,
363 sizeof(sin.sin_addr.s_addr), sin.sin_family);
364 if (he == NULL) {
365 ret = EAI_FAIL;
366 verbosef("gethostbyname error %s", hstrerror(h_errno));
367 } else {
368 ret = 0;
369 strlcpy(host, he->h_name, sizeof(host));
370 }
371 }
372 break;
373 case IPv6:
374 sin6.sin6_family = AF_INET6;
375 memcpy(&sin6.sin6_addr, &ip.ip.v6, sizeof(sin6.sin6_addr));
376 ret = getnameinfo((struct sockaddr *) &sin6, sizeof(sin6),
377 host, sizeof(host), NULL, 0, flags);
378 break;
379 default:
380 ret = EAI_FAMILY;
381 }
382
383 if (ret != 0) {
384 reply.name[0] = '\0';
385 reply.error = ret;
386 } else {
387 assert(sizeof(reply.name) > sizeof(char *)); /* not just a ptr */
388 strlcpy(reply.name, host, sizeof(reply.name));
389 reply.error = 0;
390 }
391 fd_set_block(sock[CHILD]);
392 xwrite(sock[CHILD], &reply, sizeof(reply));
393 verbosef("DNS: %s is \"%s\".", addr_to_str(&reply.addr),
394 (ret == 0) ? reply.name : gai_strerror(ret));
395 }
396 }
397 }
398
399 /* vim:set ts=3 sw=3 tw=78 expandtab: */