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Steve French197c1832008-01-10 17:10:23 +00001/*
2 * fs/cifs/dns_resolve.c
3 *
4 * Copyright (c) 2007 Igor Mammedov
5 * Author(s): Igor Mammedov (niallain@gmail.com)
6 * Steve French (sfrench@us.ibm.com)
Wang Lei1a4240f2010-08-04 15:16:33 +01007 * Wang Lei (wang840925@gmail.com)
8 * David Howells (dhowells@redhat.com)
Steve French197c1832008-01-10 17:10:23 +00009 *
10 * Contains the CIFS DFS upcall routines used for hostname to
11 * IP address translation.
12 *
13 * This library is free software; you can redistribute it and/or modify
14 * it under the terms of the GNU Lesser General Public License as published
15 * by the Free Software Foundation; either version 2.1 of the License, or
16 * (at your option) any later version.
17 *
18 * This library is distributed in the hope that it will be useful,
19 * but WITHOUT ANY WARRANTY; without even the implied warranty of
20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
21 * the GNU Lesser General Public License for more details.
22 *
23 * You should have received a copy of the GNU Lesser General Public License
24 * along with this library; if not, write to the Free Software
25 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
26 */
27
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090028#include <linux/slab.h>
Wang Lei1a4240f2010-08-04 15:16:33 +010029#include <linux/dns_resolver.h>
Steve French197c1832008-01-10 17:10:23 +000030#include "dns_resolve.h"
31#include "cifsglob.h"
32#include "cifsproto.h"
33#include "cifs_debug.h"
34
Wang Lei1a4240f2010-08-04 15:16:33 +010035/**
36 * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
37 * @unc: UNC path specifying the server
38 * @ip_addr: Where to return the IP address.
39 *
40 * The IP address will be returned in string form, and the caller is
41 * responsible for freeing it.
42 *
43 * Returns length of result on success, -ve on error.
Steve French197c1832008-01-10 17:10:23 +000044 */
45int
Steve French366781c2008-01-25 10:12:41 +000046dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
47{
Wang Lei1a4240f2010-08-04 15:16:33 +010048 struct sockaddr_storage ss;
49 const char *hostname, *sep;
Steve French197c1832008-01-10 17:10:23 +000050 char *name;
Wang Lei1a4240f2010-08-04 15:16:33 +010051 int len, rc;
Steve French197c1832008-01-10 17:10:23 +000052
Steve French366781c2008-01-25 10:12:41 +000053 if (!ip_addr || !unc)
Steve French197c1832008-01-10 17:10:23 +000054 return -EINVAL;
55
Steve French197c1832008-01-10 17:10:23 +000056 len = strlen(unc);
57 if (len < 3) {
Joe Perchesb6b38f72010-04-21 03:50:45 +000058 cFYI(1, "%s: unc is too short: %s", __func__, unc);
Steve French197c1832008-01-10 17:10:23 +000059 return -EINVAL;
60 }
Wang Lei1a4240f2010-08-04 15:16:33 +010061
62 /* Discount leading slashes for cifs */
Steve French197c1832008-01-10 17:10:23 +000063 len -= 2;
Wang Lei1a4240f2010-08-04 15:16:33 +010064 hostname = unc + 2;
65
66 /* Search for server name delimiter */
67 sep = memchr(hostname, '\\', len);
68 if (sep)
69 len = sep - unc;
70 else
Joe Perchesb6b38f72010-04-21 03:50:45 +000071 cFYI(1, "%s: probably server name is whole unc: %s",
Wang Lei1a4240f2010-08-04 15:16:33 +010072 __func__, unc);
Steve French197c1832008-01-10 17:10:23 +000073
Wang Lei1a4240f2010-08-04 15:16:33 +010074 /* Try to interpret hostname as an IPv4 or IPv6 address */
75 rc = cifs_convert_address((struct sockaddr *)&ss, hostname, len);
76 if (rc > 0)
77 goto name_is_IP_address;
Steve French197c1832008-01-10 17:10:23 +000078
Wang Lei1a4240f2010-08-04 15:16:33 +010079 /* Perform the upcall */
80 rc = dns_query(NULL, hostname, len, NULL, ip_addr, NULL);
81 if (rc < 0)
82 cERROR(1, "%s: unable to resolve: %*.*s",
83 __func__, len, len, hostname);
84 else
85 cFYI(1, "%s: resolved: %*.*s to %s",
86 __func__, len, len, hostname, *ip_addr);
Steve French197c1832008-01-10 17:10:23 +000087 return rc;
Steve French197c1832008-01-10 17:10:23 +000088
Wang Lei1a4240f2010-08-04 15:16:33 +010089name_is_IP_address:
90 name = kmalloc(len + 1, GFP_KERNEL);
91 if (!name)
David Howells4c0c03c2010-07-22 12:53:18 +010092 return -ENOMEM;
Wang Lei1a4240f2010-08-04 15:16:33 +010093 memcpy(name, hostname, len);
94 name[len] = 0;
95 cFYI(1, "%s: unc is IP, skipping dns upcall: %s", __func__, name);
96 *ip_addr = name;
David Howells4c0c03c2010-07-22 12:53:18 +010097 return 0;
David Howells4c0c03c2010-07-22 12:53:18 +010098}