2 * Copyright (c) 2008-2014, Simon Schubert <2@0x2c.org>.
3 * Copyright (c) 2008 The DragonFly Project. All rights reserved.
5 * This code is derived from software contributed to The DragonFly Project
6 * by Simon Schubert <2@0x2c.org>.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the
18 * 3. Neither the name of The DragonFly Project nor the names of its
19 * contributors may be used to endorse or promote products derived
20 * from this software without specific, prior written permission.
22 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
23 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
24 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
25 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
26 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
27 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
28 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
29 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
30 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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32 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 #include <sys/types.h>
37 #include <sys/param.h>
38 #include <netinet/in.h>
39 #include <arpa/inet.h>
40 #include <arpa/nameser.h>
50 sort_pref(const void *a, const void *b)
52 const struct mx_hostentry *ha = a, *hb = b;
55 /* sort increasing by preference primarily */
56 v = ha->pref - hb->pref;
60 /* sort PF_INET6 before PF_INET */
61 v = - (ha->ai.ai_family - hb->ai.ai_family);
66 add_host(int pref, const char *host, int port, struct mx_hostentry **he, size_t *ps)
68 struct addrinfo hints, *res, *res0 = NULL;
70 struct mx_hostentry *p;
71 const int count_inc = 10;
73 memset(&hints, 0, sizeof(hints));
74 hints.ai_family = PF_UNSPEC;
75 hints.ai_socktype = SOCK_STREAM;
76 hints.ai_protocol = IPPROTO_TCP;
78 snprintf(servname, sizeof(servname), "%d", port);
79 switch (getaddrinfo(host, servname, &hints, &res0)) {
85 * EAI_NONAME gets returned for:
86 * SMARTHOST set but DNS server not reachable -> defer
87 * SMARTHOST set but DNS server returns "host does not exist"
88 * -> buggy configuration
89 * -> either defer or bounce would be ok -> defer
90 * MX entry was returned by DNS server but name doesn't resolve
91 * -> hopefully transient situation -> defer
92 * all other DNS problems should have been caught earlier
93 * in dns_get_mx_list().
100 for (res = res0; res != NULL; res = res->ai_next) {
101 if (*ps + 1 >= roundup(*ps, count_inc)) {
102 size_t newsz = roundup(*ps + 2, count_inc);
103 *he = reallocf(*he, newsz * sizeof(**he));
109 strlcpy(p->host, host, sizeof(p->host));
112 p->ai.ai_addr = NULL;
113 bcopy(res->ai_addr, &p->sa, p->ai.ai_addrlen);
115 getnameinfo((struct sockaddr *)&p->sa, p->ai.ai_addrlen,
116 p->addr, sizeof(p->addr),
117 NULL, 0, NI_NUMERICHOST);
132 dns_get_mx_list(const char *host, int port, struct mx_hostentry **he, int no_mx)
134 char outname[MAXDNAME];
137 const char *searchhost;
138 const unsigned char *cp;
140 struct mx_hostentry *hosts = NULL;
162 err = res_search(searchhost, ns_c_in, ns_t_mx, ans, anssz);
167 * Host exists, but no MX (or CNAME) entry.
168 * Not an error, use host name instead.
172 /* transient error */
182 if (!ns_initparse(ans, anssz, &msg))
185 switch (ns_msg_getflag(msg, ns_f_rcode)) {
194 for (i = 0; i < ns_msg_count(msg, ns_s_an); i++) {
195 if (ns_parserr(&msg, ns_s_an, i, &rr))
198 cp = ns_rr_rdata(rr);
200 switch (ns_rr_type(rr)) {
205 err = ns_name_uncompress(ns_msg_base(msg), ns_msg_end(msg),
206 cp, outname, sizeof(outname));
210 err = add_host(pref, outname, port, &hosts, &nhosts);
216 err = ns_name_uncompress(ns_msg_base(msg), ns_msg_end(msg),
217 cp, outname, sizeof(outname));
221 /* Prevent a CNAME loop */
222 if (cname_recurse++ > 10)
225 searchhost = outname;
250 * If we didn't find any MX, use the hostname instead.
252 err = add_host(0, host, port, &hosts, &nhosts);
253 } else if (nhosts == 0) {
255 * We did get MX, but couldn't resolve any of them
256 * due to transient errors.
263 qsort(hosts, nhosts, sizeof(*hosts), sort_pref);
265 *hosts[nhosts].host = 0;
283 main(int argc, char **argv)
285 struct mx_hostentry *he, *p;
288 err = dns_get_mx_list(argv[1], 53, &he, 0);
292 for (p = he; *p->host != 0; p++) {
293 printf("%d\t%s\t%s\n", p->pref, p->host, p->addr);