DNS: Make AFS go to the DNS for AFSDB records for unknown cells
Add DNS query support for AFS so that it can get the IP addresses of Volume
Location servers from the DNS using an AFSDB record.
This requires userspace support. /etc/request-key.conf must be configured to
invoke a helper for dns_resolver type keys with a subtype of "afsdb:" in the
description.
Signed-off-by: Wang Lei <wang840925@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/afs/Kconfig b/fs/afs/Kconfig
index 5c4e61d..8f975f2 100644
--- a/fs/afs/Kconfig
+++ b/fs/afs/Kconfig
@@ -2,6 +2,7 @@
tristate "Andrew File System support (AFS) (EXPERIMENTAL)"
depends on INET && EXPERIMENTAL
select AF_RXRPC
+ select DNS_RESOLVER
help
If you say Y here, you will get an experimental Andrew File System
driver. It currently only supports unsecured read-only AFS access.
diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index e19c13f..ffea35c 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -13,6 +13,7 @@
#include <linux/slab.h>
#include <linux/key.h>
#include <linux/ctype.h>
+#include <linux/dns_resolver.h>
#include <linux/sched.h>
#include <keys/rxrpc-type.h>
#include "internal.h"
@@ -36,6 +37,8 @@
struct key *key;
size_t namelen;
char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp, *next;
+ char *dvllist = NULL, *_vllist = NULL;
+ char delimiter = ':';
int ret;
_enter("%s,%s", name, vllist);
@@ -43,8 +46,10 @@
BUG_ON(!name); /* TODO: want to look up "this cell" in the cache */
namelen = strlen(name);
- if (namelen > AFS_MAXCELLNAME)
+ if (namelen > AFS_MAXCELLNAME) {
+ _leave(" = -ENAMETOOLONG");
return ERR_PTR(-ENAMETOOLONG);
+ }
/* allocate and initialise a cell record */
cell = kzalloc(sizeof(struct afs_cell) + namelen + 1, GFP_KERNEL);
@@ -64,15 +69,31 @@
INIT_LIST_HEAD(&cell->vl_list);
spin_lock_init(&cell->vl_lock);
+ /* if the ip address is invalid, try dns query */
+ if (!vllist || strlen(vllist) < 7) {
+ ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
+ if (ret < 0) {
+ _leave(" = %d", ret);
+ return ERR_PTR(ret);
+ }
+ _vllist = dvllist;
+
+ /* change the delimiter for user-space reply */
+ delimiter = ',';
+
+ } else {
+ _vllist = vllist;
+ }
+
/* fill in the VL server list from the rest of the string */
do {
unsigned a, b, c, d;
- next = strchr(vllist, ':');
+ next = strchr(_vllist, delimiter);
if (next)
*next++ = 0;
- if (sscanf(vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
+ if (sscanf(_vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
goto bad_address;
if (a > 255 || b > 255 || c > 255 || d > 255)
@@ -81,7 +102,7 @@
cell->vl_addrs[cell->vl_naddrs++].s_addr =
htonl((a << 24) | (b << 16) | (c << 8) | d);
- } while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (vllist = next));
+ } while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (_vllist = next));
/* create a key to represent an anonymous user */
memcpy(keyname, "afs@", 4);
@@ -110,6 +131,7 @@
ret = -EINVAL;
error:
key_put(cell->anonymous_key);
+ kfree(dvllist);
kfree(cell);
_leave(" = %d", ret);
return ERR_PTR(ret);
@@ -201,14 +223,12 @@
}
cp = strchr(rootcell, ':');
- if (!cp) {
- printk(KERN_ERR "kAFS: no VL server IP addresses specified\n");
- _leave(" = -EINVAL");
- return -EINVAL;
- }
+ if (!cp)
+ _debug("kAFS: no VL server IP addresses specified");
+ else
+ *cp++ = 0;
/* allocate a cell record for the root cell */
- *cp++ = 0;
new_root = afs_cell_create(rootcell, cp);
if (IS_ERR(new_root)) {
_leave(" = %ld", PTR_ERR(new_root));