dns_utils.c revision 243883 
1/*-
2 * Copyright (c) 2012 Baptiste Daroussin <bapt@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer,
10 *    without modification, immediately at the beginning of the file.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: head/usr.sbin/pkg/dns_utils.c 243883 2012-12-05 11:35:50Z bapt $");
29
30#include <stdlib.h>
31#include <string.h>
32#include <netinet/in.h>
33#include <resolv.h>
34
35#include "dns_utils.h"
36
37typedef union {
38	HEADER hdr;
39	unsigned char buf[1024];
40} dns_query;
41
42struct dns_srvinfo *
43dns_getsrvinfo(const char *zone)
44{
45	struct dns_srvinfo **res, *first;
46	unsigned char *end, *p;
47	char host[MAXHOSTNAMELEN];
48	dns_query q;
49	int len, qdcount, ancount, n, i;
50	unsigned int type, class, ttl, priority, weight, port;
51
52	if ((len = res_query(zone, C_IN, T_SRV, q.buf, sizeof(q.buf))) == -1 ||
53	    len < (int)sizeof(HEADER))
54		return (NULL);
55
56	qdcount = ntohs(q.hdr.qdcount);
57	ancount = ntohs(q.hdr.ancount);
58
59	end = q.buf + len;
60	p = q.buf + sizeof(HEADER);
61
62	while(qdcount > 0 && p < end) {
63		qdcount--;
64		if((len = dn_expand(q.buf, end, p, host, MAXHOSTNAMELEN)) < 0)
65			return (NULL);
66		p += len + NS_QFIXEDSZ;
67	}
68
69	res = malloc(sizeof(struct dns_srvinfo) * ancount);
70	if (res == NULL)
71		return (NULL);
72	memset(res, 0, sizeof(struct dns_srvinfo) * ancount);
73
74	n = 0;
75	while (ancount > 0 && p < end) {
76		ancount--;
77		len = dn_expand(q.buf, end, p, host, MAXHOSTNAMELEN);
78		if (len < 0) {
79			for (i = 0; i < n; i++)
80				free(res[i]);
81			free(res);
82			return NULL;
83		}
84
85		p += len;
86
87		NS_GET16(type, p);
88		NS_GET16(class, p);
89		NS_GET32(ttl, p);
90		NS_GET16(len, p);
91
92		if (type != T_SRV) {
93			p += len;
94			continue;
95		}
96
97		NS_GET16(priority, p);
98		NS_GET16(weight, p);
99		NS_GET16(port, p);
100
101		len = dn_expand(q.buf, end, p, host, MAXHOSTNAMELEN);
102		if (len < 0) {
103			for (i = 0; i < n; i++)
104				free(res[i]);
105			free(res);
106			return (NULL);
107		}
108
109		res[n] = malloc(sizeof(struct dns_srvinfo));
110		if (res[n] == NULL) {
111			for (i = 0; i < n; i++)
112				free(res[i]);
113			free(res);
114			return (NULL);
115		}
116		res[n]->type = type;
117		res[n]->class = class;
118		res[n]->ttl = ttl;
119		res[n]->priority = priority;
120		res[n]->weight = weight;
121		res[n]->port = port;
122		res[n]->next = NULL;
123		strlcpy(res[n]->host, host, MAXHOSTNAMELEN);
124
125		p += len;
126		n++;
127	}
128
129	for (i = 0; i < n - 1; i++)
130		res[i]->next = res[i + 1];
131
132	first = res[0];
133	free(res);
134
135	return (first);
136}
137