masqmail: 1e5e457dea18 src/lookup.c

masqmail

view src/lookup.c @ 264:1e5e457dea18

comments and a small refactoring

author	markus schnalke <meillo@marmaro.de>
date	Fri, 03 Dec 2010 10:43:38 -0300
parents	dcb315792513
children	41958685480d

line source

1 /* MasqMail

2 * Copyright (C) Oliver Kurth

3 * Copyright (C) markus schnalke <meillo@marmaro.de>

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., 675 Mass Ave, Cambridge, MA 02139, USA.

18 */

20 #include <sys/types.h>

21 #include <netinet/in.h>

22 #include <arpa/nameser.h>

23 #include <resolv.h>

25 #include "masqmail.h"

28 #ifdef ENABLE_RESOLVER

30 static union {

31 HEADER hdr;

32 unsigned char buf[PACKETSZ];

33 } response;

34 static unsigned char *resp_end;

35 static unsigned char *resp_pos;

37 static int num_answers;

38 static char name[MAX_DNSNAME];

40 unsigned short rr_type;

41 unsigned short rr_dlen;

43 static unsigned short

44 getshort(unsigned char *c)

45 {

46 unsigned short u;

47 u = c[0];

48 return (u << 8) + c[1];

49 }

51 static int

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

53 {

54 int n;

55 int i;

56 int resp_len;

58 DEBUG(5) debugf("DNS: before res_search()\n");

59 if (do_search)

60 resp_len = res_search(domain, C_IN, type, response.buf, sizeof(response));

61 else

62 resp_len = res_query(domain, C_IN, type, response.buf, sizeof(response));

63 DEBUG(5) debugf("DBG: after res_search()\n");

65 if (resp_len <= 0) {

66 /*

67 if (errno == ECONNREFUSED) return DNS_SOFT;

68 if (h_errno == TRY_AGAIN) return DNS_SOFT;

69 return DNS_HARD;

70 */

71 return -1;

72 }

73 if (resp_len >= sizeof(response))

74 resp_len = sizeof(response);

76 resp_end = response.buf + resp_len;

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

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

80 while (n-- > 0) {

81 i = dn_expand(response.buf, resp_end, resp_pos, name, MAX_DNSNAME);

82 if (i < 0)

83 return -1;

84 DEBUG(5) debugf("DBG: resolve name = %s\n", name);

85 resp_pos += i;

86 i = resp_end - resp_pos;

87 if (i < QFIXEDSZ)

88 return -1;

89 resp_pos += QFIXEDSZ;

90 }

91 num_answers = ntohs(response.hdr.ancount);

93 return 0;

94 }

96 static int

97 dns_next()

98 {

99 int i;

100

101 if (num_answers <= 0)

102 return 2;

103 num_answers--;

104

105 if (resp_pos == resp_end)

106 return -1; /* soft */

107

108 i = dn_expand(response.buf, resp_end, resp_pos, name, 256);

109 if (i < 0)

110 return -1; /* soft */

111 resp_pos += i;

112

113 i = resp_end - resp_pos;

114 if (i < 4 + 3 * 2)

115 return -1; /* soft */

116

117 rr_type = getshort(resp_pos);

118 rr_dlen = getshort(resp_pos + 8);

119 resp_pos += 10;

120

121 return 0;

122 }

123

124 static int

125 dns_getip(guint32 * ip)

126 {

127 int ret;

128

129 if ((ret = dns_next()))

130 return ret;

131

132 if (rr_type == T_A) {

133 if (rr_dlen < 4)

134 return -1; /* soft */

135 *ip = *(guint32 *) (resp_pos);

136 DEBUG(5) debugf("DNS: dns_getip(): ip = %s\n", inet_ntoa(*(struct in_addr *) ip));

137 resp_pos += rr_dlen;

138

139 return 1;

140 }

141 resp_pos += rr_dlen;

142 return 0;

143 }

144

145 static int

146 dns_getmx(int *pref)

147 {

148 int ret;

149

150 if ((ret = dns_next()))

151 return ret;

152

153 if (rr_type == T_MX) {

154 if (rr_dlen < 3)

155 return -1; /* soft */

156

157 *pref = (resp_pos[0] << 8) + resp_pos[1];

158 if (dn_expand(response.buf, resp_end, resp_pos + 2, name, MAX_DNSNAME) < 0)

159 return -1;

160

161 resp_pos += rr_dlen;

162

163 return 1;

164 }

165 resp_pos += rr_dlen;

166 return 0;

167 }

168

169 int

170 dns_look_ip(gchar * domain, guint32 * ip)

171 {

172 gchar *n = domain;

173

174 while (TRUE) {

175 if (dns_resolve(n, T_A, FALSE) != 0) {

176 return -1;

177 }

178

179 dns_next();

180 if (rr_type == T_A) {

181 if (rr_dlen < 4) {

182 return -1; /* soft */

183 }

184 *ip = *(guint32 *) (resp_pos);

185

186 DEBUG(5) debugf("DNS: dns_look_ip(): ip = %s\n", inet_ntoa(*(struct in_addr *) ip));

187

188 resp_pos += rr_dlen;

189 return 0;

190 } else if (rr_type == T_CNAME) {

191 if (dn_expand(response.buf, resp_end, resp_pos, name, MAX_DNSNAME) < 0) {

192 return -1;

193 }

194

195 DEBUG(5) debugf("DNS: (CNAME) dns_look_ip(): name = %s\n", name);

196

197 resp_pos += rr_dlen;

198 n = name;

199 } else {

200 return -1;

201 }

202 }

203 }

204

205 GList*

206 resolve_dns_a(GList * list, gchar * domain)

207 {

208 int ret;

209

210 DEBUG(5) debugf("DNS: resolve_dns_a entered\n");

211

212 if (dns_resolve(domain, T_A, TRUE) == 0) {

213 mxip_addr mxip;

214 while ((ret = dns_getip(&(mxip.ip))) != 2) {

215 if (ret == 1) {

216 mxip.name = g_strdup(name);

217 mxip.pref = 0;

218 list = g_list_append(list, g_memdup(&mxip, sizeof(mxip)));

219 }

220 }

221 }

222 return list;

223 }

224

225 static gint

226 _mx_sort_func(gconstpointer aa, gconstpointer bb)

227 {

228 const mxip_addr *a = (mxip_addr *) aa;

229 const mxip_addr *b = (mxip_addr *) bb;

230

231 if (a->pref == b->pref)

232 return a->ip - b->ip;

233 else

234 return a->pref - b->pref;

235 }

236

237 GList*

238 resolve_dns_mx(GList * list, gchar * domain)

239 {

240 GList *node;

241 int ret;

242 int cnt = 0;

243

244 DEBUG(5) debugf("DNS: resolve_dns_mx entered\n");

245

246 if (dns_resolve(domain, T_MX, TRUE) == 0) {

247 GList *node_next;

248 mxip_addr mxip;

249 while ((ret = dns_getmx(&(mxip.pref))) != 2) {

250 if (ret == 1) {

251 mxip.name = g_strdup(name);

252 mxip.ip = rand();

253 list = g_list_append(list, g_memdup(&mxip, sizeof(mxip)));

254 cnt++;

255 }

256 }

257

258 DEBUG(5) debugf("DNS: found %d mx records\n", cnt);

259

260 /* to randomize sequences with equal pref values,

261 we temporarily 'misused' the ip field and

262 put a random number in it as a secondary sort key.

263 */

264 list = g_list_sort(list, _mx_sort_func);

265

266 /* CNAME resolving has to be added as well. */

267

268 for (node = g_list_first(list); node != NULL; node = node_next) {

269

270 mxip_addr *p_mxip = (mxip_addr *) (node->data);

271 node_next = g_list_next(node);

272

273 if (dns_look_ip(p_mxip->name, &(p_mxip->ip)) != 0) {

274 DEBUG(1) debugf("DNS: could not resolve target of mx %s\n", p_mxip->name);

275 list = g_list_remove_link(list, node);

276 g_free(node->data);

277 g_list_free_1(node);

278 }

279 }

280 }

281 return list;

282 }

283

284 #endif

285

286 /* now something completely different... */

287

288 GList*

289 resolve_byname(GList * list, gchar * domain)

290 {

291 struct hostent *hent;

292

293 DEBUG(5) debugf("DNS: resolve_byname entered\n");

294

295 if ((hent = gethostbyname(domain))) {

296 char *haddr;

297 int i = 0;

298 while ((haddr = hent->h_addr_list[i++])) {

299 mxip_addr mxip;

300 mxip.ip = *(guint32 *) (haddr);

301 mxip.pref = 0;

302 mxip.name = g_strdup(hent->h_name);

303 list = g_list_append(list, g_memdup(&mxip, sizeof(mxip)));

304 }

305 }

306 return list;

307 }