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// SPDX-License-Identifier: LGPL-2.1
/*
*
* Copyright (c) 2007 Igor Mammedov
* Author(s): Igor Mammedov (niallain@gmail.com)
* Steve French (sfrench@us.ibm.com)
* Wang Lei (wang840925@gmail.com)
* David Howells (dhowells@redhat.com)
*
* Contains the CIFS DFS upcall routines used for hostname to
* IP address translation.
*
*/
#include <linux/inet.h>
#include <linux/slab.h>
#include <linux/dns_resolver.h>
#include "dns_resolve.h"
#include "cifsglob.h"
#include "cifsproto.h"
#include "cifs_debug.h"
static int resolve_name(const char *name, size_t namelen, struct sockaddr *addr)
{
char *ip;
int rc;
rc = dns_query(current->nsproxy->net_ns, NULL, name,
namelen, NULL, &ip, NULL, false);
if (rc < 0) {
cifs_dbg(FYI, "%s: unable to resolve: %*.*s\n",
__func__, (int)namelen, (int)namelen, name);
} else {
cifs_dbg(FYI, "%s: resolved: %*.*s to %s\n",
__func__, (int)namelen, (int)namelen, name, ip);
rc = cifs_convert_address(addr, ip, strlen(ip));
kfree(ip);
if (!rc) {
cifs_dbg(FYI, "%s: unable to determine ip address\n",
__func__);
rc = -EHOSTUNREACH;
} else {
rc = 0;
}
}
return rc;
}
/**
* dns_resolve_name - Perform an upcall to resolve hostname to an ip address.
* @dom: DNS domain name (or NULL)
* @name: Name to look up
* @namelen: Length of name
* @ip_addr: Where to return the IP address
*
* Returns zero on success, -ve code otherwise.
*/
int dns_resolve_name(const char *dom, const char *name,
size_t namelen, struct sockaddr *ip_addr)
{
size_t len;
char *s;
int rc;
cifs_dbg(FYI, "%s: dom=%s name=%.*s\n", __func__, dom, (int)namelen, name);
if (!ip_addr || !name || !*name || !namelen)
return -EINVAL;
cifs_dbg(FYI, "%s: hostname=%.*s\n", __func__, (int)namelen, name);
/* Try to interpret hostname as an IPv4 or IPv6 address */
rc = cifs_convert_address(ip_addr, name, namelen);
if (rc > 0) {
cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %*.*s\n",
__func__, (int)namelen, (int)namelen, name);
return 0;
}
/*
* If @name contains a NetBIOS name and @dom has been specified, then
* convert @name to an FQDN and try resolving it first.
*/
if (dom && *dom && cifs_netbios_name(name, namelen)) {
len = strnlen(dom, CIFS_MAX_DOMAINNAME_LEN) + namelen + 2;
s = kmalloc(len, GFP_KERNEL);
if (!s)
return -ENOMEM;
scnprintf(s, len, "%.*s.%s", (int)namelen, name, dom);
rc = resolve_name(s, len - 1, ip_addr);
kfree(s);
if (!rc)
return 0;
}
return resolve_name(name, namelen, ip_addr);
}
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