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-rw-r--r--dns.c400
1 files changed, 400 insertions, 0 deletions
diff --git a/dns.c b/dns.c
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index 0000000..ed42787
--- /dev/null
+++ b/dns.c
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1#include <stdio.h>
2#include <netdb.h>
3#include <sys/types.h>
4#include <netinet/in.h>
5#include <arpa/nameser.h>
6#include <resolv.h>
7#include <errno.h>
8extern int res_query();
9extern int res_search();
10extern int errno;
11extern int h_errno;
12#include "ip.h"
13#include "ipalloc.h"
14#include "fmt.h"
15#include "alloc.h"
16#include "str.h"
17#include "stralloc.h"
18#include "dns.h"
19#include "case.h"
20
21static unsigned short getshort(c) unsigned char *c;
22{ unsigned short u; u = c[0]; return (u << 8) + c[1]; }
23
24static union { HEADER hdr; unsigned char buf[PACKETSZ]; } response;
25static int responselen;
26static unsigned char *responseend;
27static unsigned char *responsepos;
28
29static int numanswers;
30static char name[MAXDNAME];
31static struct ip_address ip;
32unsigned short pref;
33
34static stralloc glue = {0};
35
36static int (*lookup)() = res_query;
37
38static int resolve(domain,type)
39stralloc *domain;
40int type;
41{
42 int n;
43 int i;
44
45 errno = 0;
46 if (!stralloc_copy(&glue,domain)) return DNS_MEM;
47 if (!stralloc_0(&glue)) return DNS_MEM;
48 responselen = lookup(glue.s,C_IN,type,response.buf,sizeof(response));
49 if (responselen <= 0)
50 {
51 if (errno == ECONNREFUSED) return DNS_SOFT;
52 if (h_errno == TRY_AGAIN) return DNS_SOFT;
53 return DNS_HARD;
54 }
55 if (responselen >= sizeof(response))
56 responselen = sizeof(response);
57 responseend = response.buf + responselen;
58 responsepos = response.buf + sizeof(HEADER);
59 n = ntohs(response.hdr.qdcount);
60 while (n-- > 0)
61 {
62 i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME);
63 if (i < 0) return DNS_SOFT;
64 responsepos += i;
65 i = responseend - responsepos;
66 if (i < QFIXEDSZ) return DNS_SOFT;
67 responsepos += QFIXEDSZ;
68 }
69 numanswers = ntohs(response.hdr.ancount);
70 return 0;
71}
72
73static int findname(wanttype)
74int wanttype;
75{
76 unsigned short rrtype;
77 unsigned short rrdlen;
78 int i;
79
80 if (numanswers <= 0) return 2;
81 --numanswers;
82 if (responsepos == responseend) return DNS_SOFT;
83
84 i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME);
85 if (i < 0) return DNS_SOFT;
86 responsepos += i;
87
88 i = responseend - responsepos;
89 if (i < 4 + 3 * 2) return DNS_SOFT;
90
91 rrtype = getshort(responsepos);
92 rrdlen = getshort(responsepos + 8);
93 responsepos += 10;
94
95 if (rrtype == wanttype)
96 {
97 if (dn_expand(response.buf,responseend,responsepos,name,MAXDNAME) < 0)
98 return DNS_SOFT;
99 responsepos += rrdlen;
100 return 1;
101 }
102
103 responsepos += rrdlen;
104 return 0;
105}
106
107static int findip(wanttype)
108int wanttype;
109{
110 unsigned short rrtype;
111 unsigned short rrdlen;
112 int i;
113
114 if (numanswers <= 0) return 2;
115 --numanswers;
116 if (responsepos == responseend) return DNS_SOFT;
117
118 i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME);
119 if (i < 0) return DNS_SOFT;
120 responsepos += i;
121
122 i = responseend - responsepos;
123 if (i < 4 + 3 * 2) return DNS_SOFT;
124
125 rrtype = getshort(responsepos);
126 rrdlen = getshort(responsepos + 8);
127 responsepos += 10;
128
129 if (rrtype == wanttype)
130 {
131 if (rrdlen < 4)
132 return DNS_SOFT;
133 ip.d[0] = responsepos[0];
134 ip.d[1] = responsepos[1];
135 ip.d[2] = responsepos[2];
136 ip.d[3] = responsepos[3];
137 responsepos += rrdlen;
138 return 1;
139 }
140
141 responsepos += rrdlen;
142 return 0;
143}
144
145static int findmx(wanttype)
146int wanttype;
147{
148 unsigned short rrtype;
149 unsigned short rrdlen;
150 int i;
151
152 if (numanswers <= 0) return 2;
153 --numanswers;
154 if (responsepos == responseend) return DNS_SOFT;
155
156 i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME);
157 if (i < 0) return DNS_SOFT;
158 responsepos += i;
159
160 i = responseend - responsepos;
161 if (i < 4 + 3 * 2) return DNS_SOFT;
162
163 rrtype = getshort(responsepos);
164 rrdlen = getshort(responsepos + 8);
165 responsepos += 10;
166
167 if (rrtype == wanttype)
168 {
169 if (rrdlen < 3)
170 return DNS_SOFT;
171 pref = (responsepos[0] << 8) + responsepos[1];
172 if (dn_expand(response.buf,responseend,responsepos + 2,name,MAXDNAME) < 0)
173 return DNS_SOFT;
174 responsepos += rrdlen;
175 return 1;
176 }
177
178 responsepos += rrdlen;
179 return 0;
180}
181
182void dns_init(flagsearch)
183int flagsearch;
184{
185 res_init();
186 if (flagsearch) lookup = res_search;
187}
188
189int dns_cname(sa)
190stralloc *sa;
191{
192 int r;
193 int loop;
194 for (loop = 0;loop < 10;++loop)
195 {
196 if (!sa->len) return loop;
197 if (sa->s[sa->len - 1] == ']') return loop;
198 if (sa->s[sa->len - 1] == '.') { --sa->len; continue; }
199 switch(resolve(sa,T_ANY))
200 {
201 case DNS_MEM: return DNS_MEM;
202 case DNS_SOFT: return DNS_SOFT;
203 case DNS_HARD: return loop;
204 default:
205 while ((r = findname(T_CNAME)) != 2)
206 {
207 if (r == DNS_SOFT) return DNS_SOFT;
208 if (r == 1)
209 {
210 if (!stralloc_copys(sa,name)) return DNS_MEM;
211 break;
212 }
213 }
214 if (r == 2) return loop;
215 }
216 }
217 return DNS_HARD; /* alias loop */
218}
219
220#define FMT_IAA 40
221
222static int iaafmt(s,ip)
223char *s;
224struct ip_address *ip;
225{
226 unsigned int i;
227 unsigned int len;
228 len = 0;
229 i = fmt_ulong(s,(unsigned long) ip->d[3]); len += i; if (s) s += i;
230 i = fmt_str(s,"."); len += i; if (s) s += i;
231 i = fmt_ulong(s,(unsigned long) ip->d[2]); len += i; if (s) s += i;
232 i = fmt_str(s,"."); len += i; if (s) s += i;
233 i = fmt_ulong(s,(unsigned long) ip->d[1]); len += i; if (s) s += i;
234 i = fmt_str(s,"."); len += i; if (s) s += i;
235 i = fmt_ulong(s,(unsigned long) ip->d[0]); len += i; if (s) s += i;
236 i = fmt_str(s,".in-addr.arpa."); len += i; if (s) s += i;
237 return len;
238}
239
240int dns_ptr(sa,ip)
241stralloc *sa;
242struct ip_address *ip;
243{
244 int r;
245
246 if (!stralloc_ready(sa,iaafmt((char *) 0,ip))) return DNS_MEM;
247 sa->len = iaafmt(sa->s,ip);
248 switch(resolve(sa,T_PTR))
249 {
250 case DNS_MEM: return DNS_MEM;
251 case DNS_SOFT: return DNS_SOFT;
252 case DNS_HARD: return DNS_HARD;
253 }
254 while ((r = findname(T_PTR)) != 2)
255 {
256 if (r == DNS_SOFT) return DNS_SOFT;
257 if (r == 1)
258 {
259 if (!stralloc_copys(sa,name)) return DNS_MEM;
260 return 0;
261 }
262 }
263 return DNS_HARD;
264}
265
266static int dns_ipplus(ia,sa,pref)
267ipalloc *ia;
268stralloc *sa;
269int pref;
270{
271 int r;
272 struct ip_mx ix;
273
274 if (!stralloc_copy(&glue,sa)) return DNS_MEM;
275 if (!stralloc_0(&glue)) return DNS_MEM;
276 if (glue.s[0]) {
277 ix.pref = 0;
278 if (!glue.s[ip_scan(glue.s,&ix.ip)] || !glue.s[ip_scanbracket(glue.s,&ix.ip)])
279 {
280 if (!ipalloc_append(ia,&ix)) return DNS_MEM;
281 return 0;
282 }
283 }
284
285 switch(resolve(sa,T_A))
286 {
287 case DNS_MEM: return DNS_MEM;
288 case DNS_SOFT: return DNS_SOFT;
289 case DNS_HARD: return DNS_HARD;
290 }
291 while ((r = findip(T_A)) != 2)
292 {
293 ix.ip = ip;
294 ix.pref = pref;
295 if (r == DNS_SOFT) return DNS_SOFT;
296 if (r == 1)
297 if (!ipalloc_append(ia,&ix)) return DNS_MEM;
298 }
299 return 0;
300}
301
302int dns_ip(ia,sa)
303ipalloc *ia;
304stralloc *sa;
305{
306 if (!ipalloc_readyplus(ia,0)) return DNS_MEM;
307 ia->len = 0;
308 return dns_ipplus(ia,sa,0);
309}
310
311int dns_mxip(ia,sa,random)
312ipalloc *ia;
313stralloc *sa;
314unsigned long random;
315{
316 int r;
317 struct mx { stralloc sa; unsigned short p; } *mx;
318 struct ip_mx ix;
319 int nummx;
320 int i;
321 int j;
322 int flagsoft;
323
324 if (!ipalloc_readyplus(ia,0)) return DNS_MEM;
325 ia->len = 0;
326
327 if (!stralloc_copy(&glue,sa)) return DNS_MEM;
328 if (!stralloc_0(&glue)) return DNS_MEM;
329 if (glue.s[0]) {
330 ix.pref = 0;
331 if (!glue.s[ip_scan(glue.s,&ix.ip)] || !glue.s[ip_scanbracket(glue.s,&ix.ip)])
332 {
333 if (!ipalloc_append(ia,&ix)) return DNS_MEM;
334 return 0;
335 }
336 }
337
338 switch(resolve(sa,T_MX))
339 {
340 case DNS_MEM: return DNS_MEM;
341 case DNS_SOFT: return DNS_SOFT;
342 case DNS_HARD: return dns_ip(ia,sa);
343 }
344
345 mx = (struct mx *) alloc(numanswers * sizeof(struct mx));
346 if (!mx) return DNS_MEM;
347 nummx = 0;
348
349 while ((r = findmx(T_MX)) != 2)
350 {
351 if (r == DNS_SOFT) { alloc_free(mx); return DNS_SOFT; }
352 if (r == 1)
353 {
354 mx[nummx].p = pref;
355 mx[nummx].sa.s = 0;
356 if (!stralloc_copys(&mx[nummx].sa,name))
357 {
358 while (nummx > 0) alloc_free(mx[--nummx].sa.s);
359 alloc_free(mx); return DNS_MEM;
360 }
361 ++nummx;
362 }
363 }
364
365 if (!nummx) return dns_ip(ia,sa); /* e.g., CNAME -> A */
366
367 flagsoft = 0;
368 while (nummx > 0)
369 {
370 unsigned long numsame;
371
372 i = 0;
373 numsame = 1;
374 for (j = 1;j < nummx;++j)
375 if (mx[j].p < mx[i].p)
376 {
377 i = j;
378 numsame = 1;
379 }
380 else if (mx[j].p == mx[i].p)
381 {
382 ++numsame;
383 random = random * 69069 + 1;
384 if ((random / 2) < (2147483647 / numsame))
385 i = j;
386 }
387
388 switch(dns_ipplus(ia,&mx[i].sa,mx[i].p))
389 {
390 case DNS_MEM: case DNS_SOFT:
391 flagsoft = 1; break;
392 }
393
394 alloc_free(mx[i].sa.s);
395 mx[i] = mx[--nummx];
396 }
397
398 alloc_free(mx);
399 return flagsoft;
400}
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