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From: David Howells on 4 Aug 2010 10:20
From: Wang Lei <wang840925(a)gmail.com>

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(a)gmail.com>
Signed-off-by: David Howells <dhowells(a)redhat.com>
---

fs/afs/Kconfig | 1 +
fs/afs/cell.c | 40 ++++++++++++++++++++++++++++++----------
2 files changed, 31 insertions(+), 10 deletions(-)

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 @@ config AFS_FS
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 @@ static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
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 @@ static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
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 @@ static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
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 @@ static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
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 @@ bad_address:
ret = -EINVAL;
error:
key_put(cell->anonymous_key);
+ kfree(dvllist);
kfree(cell);
_leave(" = %d", ret);
return ERR_PTR(ret);
@@ -201,14 +223,12 @@ int afs_cell_init(char *rootcell)
}

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));

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Prev: Crypto Update for 2.6.36
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