/*
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* fs/cifs/dns_resolve.c
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*
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* Copyright (c) 2007 Igor Mammedov
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* Author(s): Igor Mammedov (niallain@gmail.com)
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* Steve French (sfrench@us.ibm.com)
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* Wang Lei (wang840925@gmail.com)
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* David Howells (dhowells@redhat.com)
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*
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* Contains the CIFS DFS upcall routines used for hostname to
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* IP address translation.
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*
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* This library is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published
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* by the Free Software Foundation; either version 2.1 of the License, or
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* (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
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* the GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/slab.h>
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#include <linux/dns_resolver.h>
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#include "dns_resolve.h"
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#include "cifsglob.h"
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#include "cifsproto.h"
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#include "cifs_debug.h"
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/**
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* dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
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* @unc: UNC path specifying the server (with '/' as delimiter)
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* @ip_addr: Where to return the IP address.
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*
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* The IP address will be returned in string form, and the caller is
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* responsible for freeing it.
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*
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* Returns length of result on success, -ve on error.
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*/
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int
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dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
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{
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struct sockaddr_storage ss;
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const char *hostname, *sep;
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char *name;
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int len, rc;
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if (!ip_addr || !unc)
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return -EINVAL;
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len = strlen(unc);
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if (len < 3) {
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cifs_dbg(FYI, "%s: unc is too short: %s\n", __func__, unc);
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return -EINVAL;
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}
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/* Discount leading slashes for cifs */
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len -= 2;
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hostname = unc + 2;
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/* Search for server name delimiter */
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sep = memchr(hostname, '/', len);
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if (sep)
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len = sep - hostname;
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else
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cifs_dbg(FYI, "%s: probably server name is whole unc: %s\n",
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__func__, unc);
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/* Try to interpret hostname as an IPv4 or IPv6 address */
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rc = cifs_convert_address((struct sockaddr *)&ss, hostname, len);
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if (rc > 0)
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goto name_is_IP_address;
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/* Perform the upcall */
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rc = dns_query(current->nsproxy->net_ns, NULL, hostname, len,
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NULL, ip_addr, NULL, false);
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if (rc < 0)
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cifs_dbg(FYI, "%s: unable to resolve: %*.*s\n",
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__func__, len, len, hostname);
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else
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cifs_dbg(FYI, "%s: resolved: %*.*s to %s\n",
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__func__, len, len, hostname, *ip_addr);
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return rc;
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name_is_IP_address:
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name = kmalloc(len + 1, GFP_KERNEL);
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if (!name)
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return -ENOMEM;
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memcpy(name, hostname, len);
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name[len] = 0;
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cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %s\n",
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__func__, name);
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*ip_addr = name;
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return 0;
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}
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