masqmail: 08b32edca1d5 src/lookup.c

masqmail

view src/lookup.c @ 215:08b32edca1d5

added the contents of the old FAQ page it surely needs an update

author	meillo@marmaro.de
date	Mon, 19 Jul 2010 14:10:14 +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 */

18 #include <sys/types.h>

19 #include <netinet/in.h>

20 #include <arpa/nameser.h>

21 #include <resolv.h>

23 #include "masqmail.h"

26 #ifdef ENABLE_RESOLVER

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;

35 static int num_answers;

36 static char name[MAX_DNSNAME];

38 unsigned short rr_type;

39 unsigned short rr_dlen;

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 }

49 static int

50 dns_resolve(char *domain, int type, gboolean do_search)

51 {

52 int n;

53 int i;

54 int resp_len;

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");

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);

74 resp_end = response.buf + resp_len;

75 resp_pos = response.buf + sizeof(HEADER);

76 n = ntohs(response.hdr.qdcount);

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);

91 return 0;

92 }

94 static int

95 dns_next()

96 {

97 int i;

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 }