1 files changed, 124 insertions, 0 deletions
diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
new file mode 100644
index 000000000000..ef7f43824347
--- /dev/null
+++ b/fs/cifs/dns_resolve.c
@@ -0,0 +1,124 @@
+/*
+ *  fs/cifs/dns_resolve.c
+ *
+ *   Copyright (c) 2007 Igor Mammedov
+ *   Author(s): Igor Mammedov (niallain@gmail.com)
+ *              Steve French (sfrench@us.ibm.com)
+ *
+ *   Contains the CIFS DFS upcall routines used for hostname to
+ *   IP address translation.
+ *
+ *   This library is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU Lesser General Public License as published
+ *   by the Free Software Foundation; either version 2.1 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This library is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU Lesser General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Lesser General Public License
+ *   along with this library; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <keys/user-type.h>
+#include "dns_resolve.h"
+#include "cifsglob.h"
+#include "cifsproto.h"
+#include "cifs_debug.h"
+
+static int dns_resolver_instantiate(struct key *key, const void *data,
+		size_t datalen)
+{
+	int rc = 0;
+	char *ip;
+
+	ip = kmalloc(datalen+1, GFP_KERNEL);
+	if (!ip)
+		return -ENOMEM;
+
+	memcpy(ip, data, datalen);
+	ip[datalen] = '\0';
+
+	rcu_assign_pointer(key->payload.data, ip);
+
+	return rc;
+}
+
+struct key_type key_type_dns_resolver = {
+	.name        = "dns_resolver",
+	.def_datalen = sizeof(struct in_addr),
+	.describe    = user_describe,
+	.instantiate = dns_resolver_instantiate,
+	.match       = user_match,
+};
+
+
+/* Resolves server name to ip address.
+ * input:
+ * 	unc - server UNC
+ * output:
+ * 	*ip_addr - pointer to server ip, caller responcible for freeing it.
+ * return 0 on success
+ */
+int
+dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
+{
+	int rc = -EAGAIN;
+	struct key *rkey;
+	char *name;
+	int len;
+
+	if (!ip_addr || !unc)
+		return -EINVAL;
+
+	/* search for server name delimiter */
+	len = strlen(unc);
+	if (len < 3) {
+		cFYI(1, ("%s: unc is too short: %s", __FUNCTION__, unc));
+		return -EINVAL;
+	}
+	len -= 2;
+	name = memchr(unc+2, '\\', len);
+	if (!name) {
+		cFYI(1, ("%s: probably server name is whole unc: %s",
+					__FUNCTION__, unc));
+	} else {
+		len = (name - unc) - 2/* leading // */;
+	}
+
+	name = kmalloc(len+1, GFP_KERNEL);
+	if (!name) {
+		rc = -ENOMEM;
+		return rc;
+	}
+	memcpy(name, unc+2, len);
+	name[len] = 0;
+
+	rkey = request_key(&key_type_dns_resolver, name, "");
+	if (!IS_ERR(rkey)) {
+		len = strlen(rkey->payload.data);
+		*ip_addr = kmalloc(len+1, GFP_KERNEL);
+		if (*ip_addr) {
+			memcpy(*ip_addr, rkey->payload.data, len);
+			(*ip_addr)[len] = '\0';
+			cFYI(1, ("%s: resolved: %s to %s", __FUNCTION__,
+					rkey->description,
+					*ip_addr
+				));
+			rc = 0;
+		} else {
+			rc = -ENOMEM;
+		}
+		key_put(rkey);
+	} else {
+		cERROR(1, ("%s: unable to resolve: %s", __FUNCTION__, name));
+	}
+
+	kfree(name);
+	return rc;
+}
+
+