masqmail

view src/lookup.c @ 214:ecd8d737d78e

find changesets by author, revision, files, or words in the commit message
removed the old manual because it is really outdated now In masqmail's 0.3 branch, so much changed that the old manual causes more harm than it improves the distribution. Most content is covered by the man pages anyway. You'll still find the old manual on masqmail's homepage.
author meillo@marmaro.de
date Mon, 19 Jul 2010 14:06:08 +0200
parents 138e66e1a61f
children 996b53a50f55
line source
1 /* MasqMail Copyright (C) Oliver Kurth,
2 *
3 * This program is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License as published by
5 * the Free Software Foundation; either version 2 of the License, or
6 * (at your option) any later version.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public License
14 * along with this program; if not, write to the Free Software
15 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
16 */
17
18 #include <sys/types.h>
19 #include <netinet/in.h>
20 #include <arpa/nameser.h>
21 #include <resolv.h>
22
23 #include "masqmail.h"
24
25
26 #ifdef ENABLE_RESOLVER
27
28 static union {
29 HEADER hdr;
30 unsigned char buf[PACKETSZ];
31 } response;
32 static unsigned char *resp_end;
33 static unsigned char *resp_pos;
34
35 static int num_answers;
36 static char name[MAX_DNSNAME];
37
38 unsigned short rr_type;
39 unsigned short rr_dlen;
40
41 static unsigned short
42 getshort(unsigned char *c)
43 {
44 unsigned short u;
45 u = c[0];
46 return (u << 8) + c[1];
47 }
48
49 static int
50 dns_resolve(char *domain, int type, gboolean do_search)
51 {
52 int n;
53 int i;
54 int resp_len;
55
56 DEBUG(5) debugf("DNS: before res_search()\n");
57 if (do_search)
58 resp_len = res_search(domain, C_IN, type, response.buf, sizeof(response));
59 else
60 resp_len = res_query(domain, C_IN, type, response.buf, sizeof(response));
61 DEBUG(5) debugf("DBG: after res_search()\n");
62
63 if (resp_len <= 0) {
64 /*
65 if (errno == ECONNREFUSED) return DNS_SOFT;
66 if (h_errno == TRY_AGAIN) return DNS_SOFT;
67 return DNS_HARD;
68 */
69 return -1;
70 }
71 if (resp_len >= sizeof(response))
72 resp_len = sizeof(response);
73
74 resp_end = response.buf + resp_len;
75 resp_pos = response.buf + sizeof(HEADER);
76 n = ntohs(response.hdr.qdcount);
77
78 while (n-- > 0) {
79 i = dn_expand(response.buf, resp_end, resp_pos, name, MAX_DNSNAME);
80 if (i < 0)
81 return -1;
82 DEBUG(5) debugf("DBG: resolve name = %s\n", name);
83 resp_pos += i;
84 i = resp_end - resp_pos;
85 if (i < QFIXEDSZ)
86 return -1;
87 resp_pos += QFIXEDSZ;
88 }
89 num_answers = ntohs(response.hdr.ancount);
90
91 return 0;
92 }
93
94 static int
95 dns_next()
96 {
97 int i;
98
99 if (num_answers <= 0)
100 return 2;
101 num_answers--;
102
103 if (resp_pos == resp_end)
104 return -1; /* soft */
105
106 i = dn_expand(response.buf, resp_end, resp_pos, name, 256);
107 if (i < 0)
108 return -1; /* soft */
109 resp_pos += i;
110
111 i = resp_end - resp_pos;
112 if (i < 4 + 3 * 2)
113 return -1; /* soft */
114
115 rr_type = getshort(resp_pos);
116 rr_dlen = getshort(resp_pos + 8);
117 resp_pos += 10;
118
119 return 0;
120 }
121
122 static int
123 dns_getip(guint32 * ip)
124 {
125 int ret;
126
127 if ((ret = dns_next()))
128 return ret;
129
130 if (rr_type == T_A) {
131 if (rr_dlen < 4)
132 return -1; /* soft */
133 *ip = *(guint32 *) (resp_pos);
134 DEBUG(5) debugf("DNS: dns_getip(): ip = %s\n", inet_ntoa(*(struct in_addr *) ip));
135 resp_pos += rr_dlen;
136
137 return 1;
138 }
139 resp_pos += rr_dlen;
140 return 0;
141 }
142
143 static int
144 dns_getmx(int *pref)
145 {
146 int ret;
147
148 if ((ret = dns_next()))
149 return ret;
150
151 if (rr_type == T_MX) {
152 if (rr_dlen < 3)
153 return -1; /* soft */
154
155 *pref = (resp_pos[0] << 8) + resp_pos[1];
156 if (dn_expand(response.buf, resp_end, resp_pos + 2, name, MAX_DNSNAME) < 0)
157 return -1;
158
159 resp_pos += rr_dlen;
160
161 return 1;
162 }
163 resp_pos += rr_dlen;
164 return 0;
165 }
166
167 int
168 dns_look_ip(gchar * domain, guint32 * ip)
169 {
170 gchar *n = domain;
171
172 while (TRUE) {
173 if (dns_resolve(n, T_A, FALSE) != 0) {
174 return -1;
175 }
176
177 dns_next();
178 if (rr_type == T_A) {
179 if (rr_dlen < 4) {
180 return -1; /* soft */
181 }
182 *ip = *(guint32 *) (resp_pos);
183
184 DEBUG(5) debugf("DNS: dns_look_ip(): ip = %s\n", inet_ntoa(*(struct in_addr *) ip));
185
186 resp_pos += rr_dlen;
187 return 0;
188 } else if (rr_type == T_CNAME) {
189 if (dn_expand(response.buf, resp_end, resp_pos, name, MAX_DNSNAME) < 0) {
190 return -1;
191 }
192
193 DEBUG(5) debugf("DNS: (CNAME) dns_look_ip(): name = %s\n", name);
194
195 resp_pos += rr_dlen;
196 n = name;
197 } else {
198 return -1;
199 }
200 }
201 }
202
203 GList*
204 resolve_dns_a(GList * list, gchar * domain)
205 {
206 int ret;
207
208 DEBUG(5) debugf("DNS: resolve_dns_a entered\n");
209
210 if (dns_resolve(domain, T_A, TRUE) == 0) {
211 mxip_addr mxip;
212 while ((ret = dns_getip(&(mxip.ip))) != 2) {
213 if (ret == 1) {
214 mxip.name = g_strdup(name);
215 mxip.pref = 0;
216 list = g_list_append(list, g_memdup(&mxip, sizeof(mxip)));
217 }
218 }
219 }
220 return list;
221 }
222
223 static gint
224 _mx_sort_func(gconstpointer aa, gconstpointer bb)
225 {
226 const mxip_addr *a = (mxip_addr *) aa;
227 const mxip_addr *b = (mxip_addr *) bb;
228
229 if (a->pref == b->pref)
230 return a->ip - b->ip;
231 else
232 return a->pref - b->pref;
233 }
234
235 GList*
236 resolve_dns_mx(GList * list, gchar * domain)
237 {
238 GList *node;
239 int ret;
240 int cnt = 0;
241
242 DEBUG(5) debugf("DNS: resolve_dns_mx entered\n");
243
244 if (dns_resolve(domain, T_MX, TRUE) == 0) {
245 GList *node_next;
246 mxip_addr mxip;
247 while ((ret = dns_getmx(&(mxip.pref))) != 2) {
248 if (ret == 1) {
249 mxip.name = g_strdup(name);
250 mxip.ip = rand();
251 list = g_list_append(list, g_memdup(&mxip, sizeof(mxip)));
252 cnt++;
253 }
254 }
255
256 DEBUG(5) debugf("DNS: found %d mx records\n", cnt);
257
258 /* to randomize sequences with equal pref values,
259 we temporarily 'misused' the ip field and
260 put a random number in it as a secondary sort key.
261 */
262 list = g_list_sort(list, _mx_sort_func);
263
264 /* CNAME resolving has to be added as well. */
265
266 for (node = g_list_first(list); node != NULL; node = node_next) {
267
268 mxip_addr *p_mxip = (mxip_addr *) (node->data);
269 node_next = g_list_next(node);
270
271 if (dns_look_ip(p_mxip->name, &(p_mxip->ip)) != 0) {
272 DEBUG(1) debugf("DNS: could not resolve target of mx %s\n", p_mxip->name);
273 list = g_list_remove_link(list, node);
274 g_free(node->data);
275 g_list_free_1(node);
276 }
277 }
278 }
279 return list;
280 }
281
282 #endif
283
284 /* now something completely different... */
285
286 GList*
287 resolve_byname(GList * list, gchar * domain)
288 {
289 struct hostent *hent;
290
291 DEBUG(5) debugf("DNS: resolve_byname entered\n");
292
293 if ((hent = gethostbyname(domain))) {
294 char *haddr;
295 int i = 0;
296 while ((haddr = hent->h_addr_list[i++])) {
297 mxip_addr mxip;
298 mxip.ip = *(guint32 *) (haddr);
299 mxip.pref = 0;
300 mxip.name = g_strdup(hent->h_name);
301 list = g_list_append(list, g_memdup(&mxip, sizeof(mxip)));
302 }
303 }
304 return list;
305 }