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-rw-r--r--Documentation/networking/dns_resolver.txt146
-rw-r--r--fs/cifs/Kconfig17
-rw-r--r--fs/cifs/cifsfs.c13
-rw-r--r--fs/cifs/dns_resolve.c229
-rw-r--r--fs/cifs/dns_resolve.h2
-rw-r--r--include/keys/dns_resolver-type.h23
-rw-r--r--include/linux/dns_resolver.h34
-rw-r--r--net/Kconfig1
-rw-r--r--net/Makefile1
-rw-r--r--net/dns_resolver/Kconfig27
-rw-r--r--net/dns_resolver/Makefile7
-rw-r--r--net/dns_resolver/dns_key.c210
-rw-r--r--net/dns_resolver/dns_query.c159
-rw-r--r--net/dns_resolver/internal.h44
14 files changed, 708 insertions, 205 deletions
diff --git a/Documentation/networking/dns_resolver.txt b/Documentation/networking/dns_resolver.txt
new file mode 100644
index 00000000000..d8e0ce1d38c
--- /dev/null
+++ b/Documentation/networking/dns_resolver.txt
@@ -0,0 +1,146 @@
+ ===================
+ DNS Resolver Module
+ ===================
+
+Contents:
+
+ - Overview.
+ - Compilation.
+ - Setting up.
+ - Usage.
+ - Mechanism.
+ - Debugging.
+
+
+========
+OVERVIEW
+========
+
+The DNS resolver module provides a way for kernel services to make DNS queries
+by way of requesting a key of key type dns_resolver. These queries are
+upcalled to userspace through /sbin/request-key.
+
+These routines must be supported by userspace tools dns.upcall, cifs.upcall and
+request-key. It is under development and does not yet provide the full feature
+set. The features it does support include:
+
+ (*) Implements the dns_resolver key_type to contact userspace.
+
+It does not yet support the following AFS features:
+
+ (*) Dns query support for AFSDB resource record.
+
+This code is extracted from the CIFS filesystem.
+
+
+===========
+COMPILATION
+===========
+
+The module should be enabled by turning on the kernel configuration options:
+
+ CONFIG_DNS_RESOLVER - tristate "DNS Resolver support"
+
+
+==========
+SETTING UP
+==========
+
+To set up this facility, the /etc/request-key.conf file must be altered so that
+/sbin/request-key can appropriately direct the upcalls. For example, to handle
+basic dname to IPv4/IPv6 address resolution, the following line should be
+added:
+
+ #OP TYPE DESC CO-INFO PROGRAM ARG1 ARG2 ARG3 ...
+ #====== ============ ======= ======= ==========================
+ create dns_resolver * * /usr/sbin/cifs.upcall %k
+
+To direct a query for query type 'foo', a line of the following should be added
+before the more general line given above as the first match is the one taken.
+
+ create dns_resolver foo:* * /usr/sbin/dns.foo %k
+
+
+
+=====
+USAGE
+=====
+
+To make use of this facility, one of the following functions that are
+implemented in the module can be called after doing:
+
+ #include <linux/dns_resolver.h>
+
+ (1) int dns_query(const char *type, const char *name, size_t namelen,
+ const char *options, char **_result, time_t *_expiry);
+
+ This is the basic access function. It looks for a cached DNS query and if
+ it doesn't find it, it upcalls to userspace to make a new DNS query, which
+ may then be cached. The key description is constructed as a string of the
+ form:
+
+ [<type>:]<name>
+
+ where <type> optionally specifies the particular upcall program to invoke,
+ and thus the type of query to do, and <name> specifies the string to be
+ looked up. The default query type is a straight hostname to IP address
+ set lookup.
+
+ The name parameter is not required to be a NUL-terminated string, and its
+ length should be given by the namelen argument.
+
+ The options parameter may be NULL or it may be a set of options
+ appropriate to the query type.
+
+ The return value is a string appropriate to the query type. For instance,
+ for the default query type it is just a list of comma-separated IPv4 and
+ IPv6 addresses. The caller must free the result.
+
+ The length of the result string is returned on success, and a -ve error
+ code is returned otherwise. -EKEYREJECTED will be returned if the DNS
+ lookup failed.
+
+ If _expiry is non-NULL, the expiry time (TTL) of the result will be
+ returned also.
+
+
+=========
+MECHANISM
+=========
+
+The dnsresolver module registers a key type called "dns_resolver". Keys of
+this type are used to transport and cache DNS lookup results from userspace.
+
+When dns_query() is invoked, it calls request_key() to search the local
+keyrings for a cached DNS result. If that fails to find one, it upcalls to
+userspace to get a new result.
+
+Upcalls to userspace are made through the request_key() upcall vector, and are
+directed by means of configuration lines in /etc/request-key.conf that tell
+/sbin/request-key what program to run to instantiate the key.
+
+The upcall handler program is responsible for querying the DNS, processing the
+result into a form suitable for passing to the keyctl_instantiate_key()
+routine. This then passes the data to dns_resolver_instantiate() which strips
+off and processes any options included in the data, and then attaches the
+remainder of the string to the key as its payload.
+
+The upcall handler program should set the expiry time on the key to that of the
+lowest TTL of all the records it has extracted a result from. This means that
+the key will be discarded and recreated when the data it holds has expired.
+
+dns_query() returns a copy of the value attached to the key, or an error if
+that is indicated instead.
+
+See <file:Documentation/keys-request-key.txt> for further information about
+request-key function.
+
+
+=========
+DEBUGGING
+=========
+
+Debugging messages can be turned on dynamically by writing a 1 into the
+following file:
+
+ /sys/module/dnsresolver/parameters/debug
diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index 5739fd7f88b..57f0aa9f141 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -71,14 +71,14 @@ config CIFS_WEAK_PW_HASH
If unsure, say N.
config CIFS_UPCALL
- bool "Kerberos/SPNEGO advanced session setup"
- depends on CIFS && KEYS
- help
- Enables an upcall mechanism for CIFS which accesses
- userspace helper utilities to provide SPNEGO packaged (RFC 4178)
- Kerberos tickets which are needed to mount to certain secure servers
- (for which more secure Kerberos authentication is required). If
- unsure, say N.
+ bool "Kerberos/SPNEGO advanced session setup"
+ depends on CIFS && KEYS
+ select DNS_RESOLVER
+ help
+ Enables an upcall mechanism for CIFS which accesses userspace helper
+ utilities to provide SPNEGO packaged (RFC 4178) Kerberos tickets
+ which are needed to mount to certain secure servers (for which more
+ secure Kerberos authentication is required). If unsure, say N.
config CIFS_XATTR
bool "CIFS extended attributes"
@@ -122,6 +122,7 @@ config CIFS_DEBUG2
config CIFS_DFS_UPCALL
bool "DFS feature support"
depends on CIFS && KEYS
+ select DNS_RESOLVER
help
Distributed File System (DFS) support is used to access shares
transparently in an enterprise name space, even if the share
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 8a2cf129e53..2a0c892959f 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -45,7 +45,6 @@
#include "cifs_fs_sb.h"
#include <linux/mm.h>
#include <linux/key-type.h>
-#include "dns_resolve.h"
#include "cifs_spnego.h"
#include "fscache.h"
#define CIFS_MAGIC_NUMBER 0xFF534D42 /* the first four bytes of SMB PDUs */
@@ -934,22 +933,13 @@ init_cifs(void)
if (rc)
goto out_unregister_filesystem;
#endif
-#ifdef CONFIG_CIFS_DFS_UPCALL
- rc = cifs_init_dns_resolver();
- if (rc)
- goto out_unregister_key_type;
-#endif
rc = slow_work_register_user(THIS_MODULE);
if (rc)
- goto out_unregister_resolver_key;
+ goto out_unregister_key_type;
return 0;
- out_unregister_resolver_key:
-#ifdef CONFIG_CIFS_DFS_UPCALL
- cifs_exit_dns_resolver();
out_unregister_key_type:
-#endif
#ifdef CONFIG_CIFS_UPCALL
unregister_key_type(&cifs_spnego_key_type);
out_unregister_filesystem:
@@ -976,7 +966,6 @@ exit_cifs(void)
cifs_fscache_unregister();
#ifdef CONFIG_CIFS_DFS_UPCALL
cifs_dfs_release_automount_timer();
- cifs_exit_dns_resolver();
#endif
#ifdef CONFIG_CIFS_UPCALL
unregister_key_type(&cifs_spnego_key_type);
diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
index aa967e7917f..0eb87026cad 100644
--- a/fs/cifs/dns_resolve.c
+++ b/fs/cifs/dns_resolve.c
@@ -4,6 +4,8 @@
* 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.
@@ -24,212 +26,73 @@
*/
#include <linux/slab.h>
-#include <linux/keyctl.h>
-#include <linux/key-type.h>
-#include <keys/user-type.h>
+#include <linux/dns_resolver.h>
#include "dns_resolve.h"
#include "cifsglob.h"
#include "cifsproto.h"
#include "cifs_debug.h"
-static const struct cred *dns_resolver_cache;
-
-/* Checks if supplied name is IP address
- * returns:
- * 1 - name is IP
- * 0 - name is not IP
- */
-static int
-is_ip(const char *name, int len)
-{
- struct sockaddr_storage ss;
-
- return cifs_convert_address((struct sockaddr *)&ss, name, len);
-}
-
-static int
-dns_resolver_instantiate(struct key *key, const void *data,
- size_t datalen)
-{
- int rc = 0;
- char *ip;
-
- /* make sure this looks like an address */
- if (!is_ip(data, datalen))
- return -EINVAL;
-
- ip = kmalloc(datalen + 1, GFP_KERNEL);
- if (!ip)
- return -ENOMEM;
-
- memcpy(ip, data, datalen);
- ip[datalen] = '\0';
-
- key->type_data.x[0] = datalen;
- key->payload.data = ip;
-
- return rc;
-}
-
-static void
-dns_resolver_destroy(struct key *key)
-{
- kfree(key->payload.data);
-}
-
-struct key_type key_type_dns_resolver = {
- .name = "dns_resolver",
- .def_datalen = sizeof(struct in_addr),
- .describe = user_describe,
- .instantiate = dns_resolver_instantiate,
- .destroy = dns_resolver_destroy,
- .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 the length of the returned string on success
+/**
+ * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
+ * @unc: UNC path specifying the server
+ * @ip_addr: Where to return the IP address.
+ *
+ * The IP address will be returned in string form, and the caller is
+ * responsible for freeing it.
+ *
+ * Returns length of result on success, -ve on error.
*/
int
dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
{
- const struct cred *saved_cred;
- int rc = -EAGAIN;
- struct key *rkey = ERR_PTR(-EAGAIN);
+ struct sockaddr_storage ss;
+ const char *hostname, *sep;
char *name;
- char *data = NULL;
- int len;
+ int len, rc;
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", __func__, unc);
return -EINVAL;
}
- len -= 2;
- name = memchr(unc+2, '\\', len);
- if (!name) {
- cFYI(1, "%s: probably server name is whole unc: %s",
- __func__, 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;
-
- if (is_ip(name, len)) {
- cFYI(1, "%s: it is IP, skipping dns upcall: %s",
- __func__, name);
- data = name;
- goto skip_upcall;
- }
- saved_cred = override_creds(dns_resolver_cache);
- rkey = request_key(&key_type_dns_resolver, name, "");
- revert_creds(saved_cred);
- if (!IS_ERR(rkey)) {
- if (!(rkey->perm & KEY_USR_VIEW)) {
- down_read(&rkey->sem);
- rkey->perm |= KEY_USR_VIEW;
- up_read(&rkey->sem);
- }
- len = rkey->type_data.x[0];
- data = rkey->payload.data;
- } else {
- cERROR(1, "%s: unable to resolve: %s", __func__, name);
- goto out;
- }
-
-skip_upcall:
- if (data) {
- *ip_addr = kmalloc(len + 1, GFP_KERNEL);
- if (*ip_addr) {
- memcpy(*ip_addr, data, len + 1);
- if (!IS_ERR(rkey))
- cFYI(1, "%s: resolved: %s to %s", __func__,
- name,
- *ip_addr
- );
- rc = len;
- } else {
- rc = -ENOMEM;
- }
- if (!IS_ERR(rkey))
- key_put(rkey);
- }
+ /* Discount leading slashes for cifs */
+ len -= 2;
+ hostname = unc + 2;
-out:
- kfree(name);
+ /* Search for server name delimiter */
+ sep = memchr(hostname, '\\', len);
+ if (sep)
+ len = sep - unc;
+ else
+ cFYI(1, "%s: probably server name is whole unc: %s",
+ __func__, unc);
+
+ /* Try to interpret hostname as an IPv4 or IPv6 address */
+ rc = cifs_convert_address((struct sockaddr *)&ss, hostname, len);
+ if (rc > 0)
+ goto name_is_IP_address;
+
+ /* Perform the upcall */
+ rc = dns_query(NULL, hostname, len, NULL, ip_addr, NULL);
+ if (rc < 0)
+ cERROR(1, "%s: unable to resolve: %*.*s",
+ __func__, len, len, hostname);
+ else
+ cFYI(1, "%s: resolved: %*.*s to %s",
+ __func__, len, len, hostname, *ip_addr);
return rc;
-}
-int __init cifs_init_dns_resolver(void)
-{
- struct cred *cred;
- struct key *keyring;
- int ret;
-
- printk(KERN_NOTICE "Registering the %s key type\n",
- key_type_dns_resolver.name);
-
- /* create an override credential set with a special thread keyring in
- * which DNS requests are cached
- *
- * this is used to prevent malicious redirections from being installed
- * with add_key().
- */
- cred = prepare_kernel_cred(NULL);
- if (!cred)
+name_is_IP_address:
+ name = kmalloc(len + 1, GFP_KERNEL);
+ if (!name)
return -ENOMEM;
-
- keyring = key_alloc(&key_type_keyring, ".dns_resolver", 0, 0, cred,
- (KEY_POS_ALL & ~KEY_POS_SETATTR) |
- KEY_USR_VIEW | KEY_USR_READ,
- KEY_ALLOC_NOT_IN_QUOTA);
- if (IS_ERR(keyring)) {
- ret = PTR_ERR(keyring);
- goto failed_put_cred;
- }
-
- ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL);
- if (ret < 0)
- goto failed_put_key;
-
- ret = register_key_type(&key_type_dns_resolver);
- if (ret < 0)
- goto failed_put_key;
-
- /* instruct request_key() to use this special keyring as a cache for
- * the results it looks up */
- cred->thread_keyring = keyring;
- cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
- dns_resolver_cache = cred;
+ memcpy(name, hostname, len);
+ name[len] = 0;
+ cFYI(1, "%s: unc is IP, skipping dns upcall: %s", __func__, name);
+ *ip_addr = name;
return 0;
-
-failed_put_key:
- key_put(keyring);
-failed_put_cred:
- put_cred(cred);
- return ret;
-}
-
-void cifs_exit_dns_resolver(void)
-{
- key_revoke(dns_resolver_cache->thread_keyring);
- unregister_key_type(&key_type_dns_resolver);
- put_cred(dns_resolver_cache);
- printk(KERN_NOTICE "Unregistered %s key type\n",
- key_type_dns_resolver.name);
}
diff --git a/fs/cifs/dns_resolve.h b/fs/cifs/dns_resolve.h
index 5d7f291df16..d3f5d27f4d0 100644
--- a/fs/cifs/dns_resolve.h
+++ b/fs/cifs/dns_resolve.h
@@ -24,8 +24,6 @@
#define _DNS_RESOLVE_H
#ifdef __KERNEL__
-extern int __init cifs_init_dns_resolver(void);
-extern void cifs_exit_dns_resolver(void);
extern int dns_resolve_server_name_to_ip(const char *unc, char **ip_addr);
#endif /* KERNEL */
diff --git a/include/keys/dns_resolver-type.h b/include/keys/dns_resolver-type.h
new file mode 100644
index 00000000000..9284a19393a
--- /dev/null
+++ b/include/keys/dns_resolver-type.h
@@ -0,0 +1,23 @@
+/* DNS resolver key type
+ *
+ * Copyright (C) 2010 Wang Lei. All Rights Reserved.
+ * Written by Wang Lei (wang840925@gmail.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifndef _KEYS_DNS_RESOLVER_TYPE_H
+#define _KEYS_DNS_RESOLVER_TYPE_H
+
+#include <linux/key-type.h>
+
+extern struct key_type key_type_dns_resolver;
+
+extern int request_dns_resolver_key(const char *description,
+ const char *callout_info,
+ char **data);
+
+#endif /* _KEYS_DNS_RESOLVER_TYPE_H */
diff --git a/include/linux/dns_resolver.h b/include/linux/dns_resolver.h
new file mode 100644
index 00000000000..cc92268af89
--- /dev/null
+++ b/include/linux/dns_resolver.h
@@ -0,0 +1,34 @@
+/*
+ * DNS Resolver upcall management for CIFS DFS and AFS
+ * Handles host name to IP address resolution and DNS query for AFSDB RR.
+ *
+ * Copyright (c) International Business Machines Corp., 2008
+ * Author(s): Steve French (sfrench@us.ibm.com)
+ * Wang Lei (wang840925@gmail.com)
+ *
+ * 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
+ */
+
+#ifndef _LINUX_DNS_RESOLVER_H
+#define _LINUX_DNS_RESOLVER_H
+
+#ifdef __KERNEL__
+
+extern int dns_query(const char *type, const char *name, size_t namelen,
+ const char *options, char **_result, time_t *_expiry);
+
+#endif /* KERNEL */
+
+#endif /* _LINUX_DNS_RESOLVER_H */
diff --git a/net/Kconfig b/net/Kconfig
index e24fa0873f3..e330594d370 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -213,6 +213,7 @@ source "net/phonet/Kconfig"
source "net/ieee802154/Kconfig"
source "net/sched/Kconfig"
source "net/dcb/Kconfig"
+source "net/dns_resolver/Kconfig"
config RPS
boolean
diff --git a/net/Makefile b/net/Makefile
index 41d420070a3..ea60fbce9b1 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -67,3 +67,4 @@ ifeq ($(CONFIG_NET),y)
obj-$(CONFIG_SYSCTL) += sysctl_net.o
endif
obj-$(CONFIG_WIMAX) += wimax/
+obj-$(CONFIG_DNS_RESOLVER) += dns_resolver/
diff --git a/net/dns_resolver/Kconfig b/net/dns_resolver/Kconfig
new file mode 100644
index 00000000000..2ec47cb5d0d
--- /dev/null
+++ b/net/dns_resolver/Kconfig
@@ -0,0 +1,27 @@
+#
+# Configuration for DNS Resolver
+#
+config DNS_RESOLVER
+ tristate "DNS Resolver support"
+ depends on NET && KEYS
+ help
+ Saying Y here will include support for the DNS Resolver key type
+ which can be used to make upcalls to perform DNS lookups in
+ userspace.
+
+ DNS Resolver is used to query DNS server for information. Examples
+ being resolving a UNC hostname element to an IP address for CIFS or
+ performing a DNS query for AFSDB records so that AFS can locate a
+ cell's volume location database servers.
+
+ DNS Resolver is used by the CIFS and AFS modules, and would support
+ samba4 later. DNS Resolver is supported by the userspace upcall
+ helper "/sbin/dns.resolver" via /etc/request-key.conf.
+
+ See <file:Documentation/networking/dns_resolver.txt> for further
+ information.
+
+ To compile this as a module, choose M here: the module will be called
+ dnsresolver.
+
+ If unsure, say N.
diff --git a/net/dns_resolver/Makefile b/net/dns_resolver/Makefile
new file mode 100644
index 00000000000..c0ef4e71dc4
--- /dev/null
+++ b/net/dns_resolver/Makefile
@@ -0,0 +1,7 @@
+#
+# Makefile for the Linux DNS Resolver.
+#
+
+obj-$(CONFIG_DNS_RESOLVER) += dns_resolver.o
+
+dns_resolver-objs := dns_key.o dns_query.o
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
new file mode 100644
index 00000000000..1b1b411adcf
--- /dev/null
+++ b/net/dns_resolver/dns_key.c
@@ -0,0 +1,210 @@
+/* Key type used to cache DNS lookups made by the kernel
+ *
+ * See Documentation/networking/dns_resolver.txt
+ *
+ * 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)
+ *
+ * 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 <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/kernel.h>
+#include <linux/keyctl.h>
+#include <keys/dns_resolver-type.h>
+#include <keys/user-type.h>
+#include "internal.h"
+
+MODULE_DESCRIPTION("DNS Resolver");
+MODULE_AUTHOR("Wang Lei");
+MODULE_LICENSE("GPL");
+
+unsigned dns_resolver_debug;
+module_param_named(debug, dns_resolver_debug, uint, S_IWUSR | S_IRUGO);
+MODULE_PARM_DESC(debug, "DNS Resolver debugging mask");
+
+const struct cred *dns_resolver_cache;
+
+/*
+ * Instantiate a user defined key for dns_resolver.
+ *
+ * The data must be a NUL-terminated string, with the NUL char accounted in
+ * datalen.
+ *
+ * If the data contains a '#' characters, then we take the clause after each
+ * one to be an option of the form 'key=value'. The actual data of interest is
+ * the string leading up to the first '#'. For instance:
+ *
+ * "ip1,ip2,...#foo=bar"
+ */
+static int
+dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
+{
+ struct user_key_payload *upayload;
+ int ret;
+ size_t result_len = 0;
+ const char *data = _data, *opt;
+
+ kenter("%%%d,%s,'%s',%zu",
+ key->serial, key->description, data, datalen);
+
+ if (datalen <= 1 || !data || data[datalen - 1] != '\0')
+ return -EINVAL;
+ datalen--;
+
+ /* deal with any options embedded in the data */
+ opt = memchr(data, '#', datalen);
+ if (!opt) {
+ kdebug("no options currently supported");
+ return -EINVAL;
+ }
+
+ result_len = datalen;
+ ret = key_payload_reserve(key, result_len);
+ if (ret < 0)
+ return -EINVAL;
+
+ upayload = kmalloc(sizeof(*upayload) + result_len + 1, GFP_KERNEL);
+ if (!upayload) {
+ kleave(" = -ENOMEM");
+ return -ENOMEM;
+ }
+
+ upayload->datalen = result_len;
+ memcpy(upayload->data, data, result_len);
+ upayload->data[result_len] = '\0';
+ rcu_assign_pointer(key->payload.data, upayload);
+
+ kleave(" = 0");
+ return 0;
+}
+
+/*
+ * The description is of the form "[<type>:]<domain_name>"
+ *
+ * The domain name may be a simple name or an absolute domain name (which
+ * should end with a period). The domain name is case-independent.
+ */
+static int
+dns_resolver_match(const struct key *key, const void *description)
+{
+ int slen, dlen, ret = 0;
+ const char *src = key->description, *dsp = description;
+
+ kenter("%s,%s", src, dsp);
+
+ if (!src || !dsp)
+ goto no_match;
+
+ if (strcasecmp(src, dsp) == 0)
+ goto matched;
+
+ slen = strlen(src);
+ dlen = strlen(dsp);
+ if (slen <= 0 || dlen <= 0)
+ goto no_match;
+ if (src[slen - 1] == '.')
+ slen--;
+ if (dsp[dlen - 1] == '.')
+ dlen--;
+ if (slen != dlen || strncasecmp(src, dsp, slen) != 0)
+ goto no_match;
+
+matched:
+ ret = 1;
+no_match:
+ kleave(" = %d", ret);
+ return ret;
+}
+
+struct key_type key_type_dns_resolver = {
+ .name = "dns_resolver",
+ .instantiate = dns_resolver_instantiate,
+ .match = dns_resolver_match,
+ .revoke = user_revoke,
+ .destroy = user_destroy,
+ .describe = user_describe,
+ .read = user_read,
+};
+
+static int __init init_dns_resolver(void)
+{
+ struct cred *cred;
+ struct key *keyring;
+ int ret;
+
+ printk(KERN_NOTICE "Registering the %s key type\n",
+ key_type_dns_resolver.name);
+
+ /* create an override credential set with a special thread keyring in
+ * which DNS requests are cached
+ *
+ * this is used to prevent malicious redirections from being installed
+ * with add_key().
+ */
+ cred = prepare_kernel_cred(NULL);
+ if (!cred)
+ return -ENOMEM;
+
+ keyring = key_alloc(&key_type_keyring, ".dns_resolver", 0, 0, cred,
+ (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+ KEY_USR_VIEW | KEY_USR_READ,
+ KEY_ALLOC_NOT_IN_QUOTA);
+ if (IS_ERR(keyring)) {
+ ret = PTR_ERR(keyring);
+ goto failed_put_cred;
+ }
+
+ ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL);
+ if (ret < 0)
+ goto failed_put_key;
+
+ ret = register_key_type(&key_type_dns_resolver);
+ if (ret < 0)
+ goto failed_put_key;
+
+ /* instruct request_key() to use this special keyring as a cache for
+ * the results it looks up */
+ cred->thread_keyring = keyring;
+ cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
+ dns_resolver_cache = cred;
+
+ kdebug("DNS resolver keyring: %d\n", key_serial(keyring));
+ return 0;
+
+failed_put_key:
+ key_put(keyring);
+failed_put_cred:
+ put_cred(cred);
+ return ret;
+}
+
+static void __exit exit_dns_resolver(void)
+{
+ key_revoke(dns_resolver_cache->thread_keyring);
+ unregister_key_type(&key_type_dns_resolver);
+ put_cred(dns_resolver_cache);
+ printk(KERN_NOTICE "Unregistered %s key type\n",
+ key_type_dns_resolver.name);
+}
+
+module_init(init_dns_resolver)
+module_exit(exit_dns_resolver)
+MODULE_LICENSE("GPL");
diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c
new file mode 100644
index 00000000000..6c0cf31ea00
--- /dev/null
+++ b/net/dns_resolver/dns_query.c
@@ -0,0 +1,159 @@
+/* Upcall routine, designed to work as a key type and working through
+ * /sbin/request-key to contact userspace when handling DNS queries.
+ *
+ * See Documentation/networking/dns_resolver.txt
+ *
+ * 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)
+ *
+ * The upcall wrapper used to make an arbitrary DNS query.
+ *
+ * This function requires the appropriate userspace tool dns.upcall to be
+ * installed and something like the following lines should be added to the
+ * /etc/request-key.conf file:
+ *
+ * create dns_resolver * * /sbin/dns.upcall %k
+ *
+ * For example to use this module to query AFSDB RR:
+ *
+ * create dns_resolver afsdb:* * /sbin/dns.afsdb %k
+ *
+ * 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 <linux/module.h>
+#include <linux/slab.h>
+#include <linux/dns_resolver.h>
+#include <keys/dns_resolver-type.h>
+#include <keys/user-type.h>
+
+#include "internal.h"
+
+/*
+ * dns_query - Query the DNS
+ * @type: Query type (or NULL for straight host->IP lookup)
+ * @name: Name to look up
+ * @namelen: Length of name
+ * @options: Request options (or NULL if no options)
+ * @_result: Where to place the returned data.
+ * @_expiry: Where to store the result expiry time (or NULL)
+ *
+ * The data will be returned in the pointer at *result, and the caller is
+ * responsible for freeing it.
+ *
+ * The description should be of the form "[<query_type>:]<domain_name>", and
+ * the options need to be appropriate for the query type requested. If no
+ * query_type is given, then the query is a straight hostname to IP address
+ * lookup.
+ *
+ * The DNS resolution lookup is performed by upcalling to userspace by way of
+ * requesting a key of type dns_resolver.
+ *
+ * Returns the size of the result on success, -ve error code otherwise.
+ */
+int dns_query(const char *type, const char *name, size_t namelen,
+ const char *options, char **_result, time_t *_expiry)
+{
+ struct key *rkey;
+ struct user_key_payload *upayload;
+ const struct cred *saved_cred;
+ size_t typelen, desclen;
+ char *desc, *cp;
+ int ret, len;
+
+ kenter("%s,%*.*s,%zu,%s",
+ type, (int)namelen, (int)namelen, name, namelen, options);
+
+ if (!name || namelen == 0 || !_result)
+ return -EINVAL;
+
+ /* construct the query key description as "[<type>:]<name>" */
+ typelen = 0;
+ desclen = 0;
+ if (type) {
+ typelen = strlen(type);
+ if (typelen < 1)
+ return -EINVAL;
+ desclen += typelen + 1;
+ }
+
+ if (!namelen)
+ namelen = strlen(name);
+ if (namelen < 3)
+ return -EINVAL;
+ desclen += namelen + 1;
+
+ desc = kmalloc(desclen, GFP_KERNEL);
+ if (!desc)
+ return -ENOMEM;
+
+ cp = desc;
+ if (type) {
+ memcpy(cp, type, typelen);
+ cp += typelen;
+ *cp++ = ':';
+ }
+ memcpy(cp, name, namelen);
+ cp += namelen;
+ *cp = '\0';
+
+ if (!options)
+ options = "";
+ kdebug("call request_key(,%s,%s)", desc, options);
+
+ /* make the upcall, using special credentials to prevent the use of
+ * add_key() to preinstall malicious redirections
+ */
+ saved_cred = override_creds(dns_resolver_cache);
+ rkey = request_key(&key_type_dns_resolver, desc, options);
+ revert_creds(saved_cred);
+ kfree(desc);
+ if (IS_ERR(rkey)) {
+ ret = PTR_ERR(rkey);
+ goto out;
+ }
+
+ down_read(&rkey->sem);
+ rkey->perm |= KEY_USR_VIEW;
+
+ ret = key_validate(rkey);
+ if (ret < 0)
+ goto put;
+
+ upayload = rcu_dereference_protected(rkey->payload.data,
+ lockdep_is_held(&rkey->sem));
+ len = upayload->datalen;
+
+ ret = -ENOMEM;
+ *_result = kmalloc(len + 1, GFP_KERNEL);
+ if (!*_result)
+ goto put;
+
+ memcpy(*_result, upayload->data, len + 1);
+ if (_expiry)
+ *_expiry = rkey->expiry;
+
+ ret = len;
+put:
+ up_read(&rkey->sem);
+ key_put(rkey);
+out:
+ kleave(" = %d", ret);
+ return ret;
+}
+EXPORT_SYMBOL(dns_query);
diff --git a/net/dns_resolver/internal.h b/net/dns_resolver/internal.h
new file mode 100644
index 00000000000..189ca9e9b78
--- /dev/null
+++ b/net/dns_resolver/internal.h
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2010 Wang Lei
+ * Author(s): Wang Lei (wang840925@gmail.com). All Rights Reserved.
+ *
+ * Internal DNS Rsolver stuff
+ *
+ * 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 <linux/compiler.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+
+/*
+ * dns_key.c
+ */
+extern const struct cred *dns_resolver_cache;
+
+/*
+ * debug tracing
+ */
+extern unsigned dns_resolver_debug;
+
+#define kdebug(FMT, ...) \
+do { \
+ if (unlikely(dns_resolver_debug)) \
+ printk(KERN_DEBUG "[%-6.6s] "FMT"\n", \
+ current->comm, ##__VA_ARGS__); \
+} while (0)
+
+#define kenter(FMT, ...) kdebug("==> %s("FMT")", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) kdebug("<== %s()"FMT"", __func__, ##__VA_ARGS__)