1*86d7f5d3SJohn Marino /* Host name canonicalization
2*86d7f5d3SJohn Marino
3*86d7f5d3SJohn Marino Copyright (C) 2005 Free Software Foundation, Inc.
4*86d7f5d3SJohn Marino
5*86d7f5d3SJohn Marino Written by Derek Price <derek@ximbiot.com>.
6*86d7f5d3SJohn Marino
7*86d7f5d3SJohn Marino This program is free software; you can redistribute it and/or
8*86d7f5d3SJohn Marino modify it under the terms of the GNU General Public License as
9*86d7f5d3SJohn Marino published by the Free Software Foundation; either version 2, or (at
10*86d7f5d3SJohn Marino your option) any later version.
11*86d7f5d3SJohn Marino
12*86d7f5d3SJohn Marino This program is distributed in the hope that it will be useful, but
13*86d7f5d3SJohn Marino WITHOUT ANY WARRANTY; without even the implied warranty of
14*86d7f5d3SJohn Marino MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15*86d7f5d3SJohn Marino General Public License for more details.
16*86d7f5d3SJohn Marino
17*86d7f5d3SJohn Marino You should have received a copy of the GNU General Public License
18*86d7f5d3SJohn Marino along with this program; if not, write to the Free Software Foundation,
19*86d7f5d3SJohn Marino Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
20*86d7f5d3SJohn Marino
21*86d7f5d3SJohn Marino #ifdef HAVE_CONFIG_H
22*86d7f5d3SJohn Marino # include <config.h>
23*86d7f5d3SJohn Marino #endif
24*86d7f5d3SJohn Marino
25*86d7f5d3SJohn Marino #include "canon-host.h"
26*86d7f5d3SJohn Marino
27*86d7f5d3SJohn Marino #include "getaddrinfo.h"
28*86d7f5d3SJohn Marino #include "strdup.h"
29*86d7f5d3SJohn Marino
30*86d7f5d3SJohn Marino /* Store the last error for the single-threaded version of this function. */
31*86d7f5d3SJohn Marino static int last_cherror;
32*86d7f5d3SJohn Marino
33*86d7f5d3SJohn Marino /* Single-threaded of wrapper for canon_host_r. After a NULL return, error
34*86d7f5d3SJohn Marino messages may be retrieved via ch_strerror(). */
35*86d7f5d3SJohn Marino char *
canon_host(const char * host)36*86d7f5d3SJohn Marino canon_host (const char *host)
37*86d7f5d3SJohn Marino {
38*86d7f5d3SJohn Marino return canon_host_r (host, &last_cherror);
39*86d7f5d3SJohn Marino }
40*86d7f5d3SJohn Marino
41*86d7f5d3SJohn Marino /* Return a malloc'd string containing the canonical hostname associated with
42*86d7f5d3SJohn Marino HOST, or NULL if a canonical name cannot be determined. On NULL return,
43*86d7f5d3SJohn Marino if CHERROR is not NULL, set *CHERROR to an error code as returned by
44*86d7f5d3SJohn Marino getaddrinfo(). Use ch_strerror_r() or gai_strerror() to convert a *CHERROR
45*86d7f5d3SJohn Marino value to a string suitable for error messages.
46*86d7f5d3SJohn Marino
47*86d7f5d3SJohn Marino WARNINGS
48*86d7f5d3SJohn Marino HOST must be a string representation of a resolvable name for this host.
49*86d7f5d3SJohn Marino Strings containing an IP address in dotted decimal notation will be
50*86d7f5d3SJohn Marino returned as-is, without further resolution.
51*86d7f5d3SJohn Marino
52*86d7f5d3SJohn Marino The use of the word "canonical" in this context is unfortunate but
53*86d7f5d3SJohn Marino entrenched. The value returned by this function will be the end result
54*86d7f5d3SJohn Marino of the resolution of any CNAME chains in the DNS. There may only be one
55*86d7f5d3SJohn Marino such value for any given hostname, though the actual IP address
56*86d7f5d3SJohn Marino referenced by this value and the device using that IP address may each
57*86d7f5d3SJohn Marino actually have any number of such "canonical" hostnames. See the POSIX
58*86d7f5d3SJohn Marino getaddrinfo spec <http://www.opengroup.org/susv3xsh/getaddrinfo.html">,
59*86d7f5d3SJohn Marino RFC 1034 <http://www.faqs.org/rfcs/rfc1034.html>, & RFC 2181
60*86d7f5d3SJohn Marino <http://www.faqs.org/rfcs/rfc2181.html> for more on what this confusing
61*86d7f5d3SJohn Marino term really refers to. */
62*86d7f5d3SJohn Marino char *
canon_host_r(char const * host,int * cherror)63*86d7f5d3SJohn Marino canon_host_r (char const *host, int *cherror)
64*86d7f5d3SJohn Marino {
65*86d7f5d3SJohn Marino char *retval = NULL;
66*86d7f5d3SJohn Marino static struct addrinfo hints;
67*86d7f5d3SJohn Marino struct addrinfo *res = NULL;
68*86d7f5d3SJohn Marino int status;
69*86d7f5d3SJohn Marino
70*86d7f5d3SJohn Marino hints.ai_flags = AI_CANONNAME;
71*86d7f5d3SJohn Marino status = getaddrinfo (host, NULL, &hints, &res);
72*86d7f5d3SJohn Marino if (!status)
73*86d7f5d3SJohn Marino {
74*86d7f5d3SJohn Marino retval = strdup (res->ai_canonname);
75*86d7f5d3SJohn Marino if (!retval && cherror)
76*86d7f5d3SJohn Marino *cherror = EAI_MEMORY;
77*86d7f5d3SJohn Marino freeaddrinfo (res);
78*86d7f5d3SJohn Marino }
79*86d7f5d3SJohn Marino else if (cherror)
80*86d7f5d3SJohn Marino *cherror = status;
81*86d7f5d3SJohn Marino
82*86d7f5d3SJohn Marino return retval;
83*86d7f5d3SJohn Marino }
84*86d7f5d3SJohn Marino
85*86d7f5d3SJohn Marino /* Return a string describing the last error encountered by canon_host. */
86*86d7f5d3SJohn Marino const char *
ch_strerror(void)87*86d7f5d3SJohn Marino ch_strerror (void)
88*86d7f5d3SJohn Marino {
89*86d7f5d3SJohn Marino return gai_strerror (last_cherror);
90*86d7f5d3SJohn Marino }
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