SUNRPC: Add rpcauth_list_flavors()

The gss_mech_list_pseudoflavors() function provides a list of
currently registered GSS pseudoflavors.  This list does not include
any non-GSS flavors that have been registered with the RPC client.
nfs4_find_root_sec() currently adds these extra flavors by hand.

Instead, nfs4_find_root_sec() should be looking at the set of flavors
that have been explicitly registered via rpcauth_register().  And,
other areas of code will soon need the same kind of list that
contains all flavors the kernel currently knows about (see below).

Rather than cloning the open-coded logic in nfs4_find_root_sec() to
those new places, introduce a generic RPC function that generates a
full list of registered auth flavors and pseudoflavors.

A new rpc_authops method is added that lists a flavor's
pseudoflavors, if it has any.  I encountered an interesting module
loader loop when I tried to get the RPC client to invoke
gss_mech_list_pseudoflavors() by name.

This patch is a pre-requisite for server trunking discovery, and a
pre-requisite for fixing up the in-kernel mount client to do better
automatic security flavor selection.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 54 insertions, 0 deletions

diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index 727e506..b5c067b 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -13,6 +13,7 @@
 #include <linux/errno.h>
 #include <linux/hash.h>
 #include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/gss_api.h>
 #include <linux/spinlock.h>
 
 #ifdef RPC_DEBUG
@@ -122,6 +123,59 @@ rpcauth_unregister(const struct rpc_authops *ops)
 }
 EXPORT_SYMBOL_GPL(rpcauth_unregister);
 
+/**
+ * rpcauth_list_flavors - discover registered flavors and pseudoflavors
+ * @array: array to fill in
+ * @size: size of "array"
+ *
+ * Returns the number of array items filled in, or a negative errno.
+ *
+ * The returned array is not sorted by any policy.  Callers should not
+ * rely on the order of the items in the returned array.
+ */
+int
+rpcauth_list_flavors(rpc_authflavor_t *array, int size)
+{
+	rpc_authflavor_t flavor;
+	int result = 0;
+
+	spin_lock(&rpc_authflavor_lock);
+	for (flavor = 0; flavor < RPC_AUTH_MAXFLAVOR; flavor++) {
+		const struct rpc_authops *ops = auth_flavors[flavor];
+		rpc_authflavor_t pseudos[4];
+		int i, len;
+
+		if (result >= size) {
+			result = -ENOMEM;
+			break;
+		}
+
+		if (ops == NULL)
+			continue;
+		if (ops->list_pseudoflavors == NULL) {
+			array[result++] = ops->au_flavor;
+			continue;
+		}
+		len = ops->list_pseudoflavors(pseudos, ARRAY_SIZE(pseudos));
+		if (len < 0) {
+			result = len;
+			break;
+		}
+		for (i = 0; i < len; i++) {
+			if (result >= size) {
+				result = -ENOMEM;
+				break;
+			}
+			array[result++] = pseudos[i];
+		}
+	}
+	spin_unlock(&rpc_authflavor_lock);
+
+	dprintk("RPC:       %s returns %d\n", __func__, result);
+	return result;
+}
+EXPORT_SYMBOL_GPL(rpcauth_list_flavors);
+
 struct rpc_auth *
 rpcauth_create(rpc_authflavor_t pseudoflavor, struct rpc_clnt *clnt)
 {