SUNRPC: Introduce rpcauth_get_pseudoflavor()

A SECINFO reply may contain flavors whose kernel module is not
yet loaded by the client's kernel.  A new RPC client API, called
rpcauth_get_pseudoflavor(), is introduced to do proper checking
for support of a security flavor.

When this API is invoked, the RPC client now tries to load the
module for each flavor first before performing the "is this
supported?" check.  This means if a module is available on the
client, but has not been loaded yet, it will be loaded and
registered automatically when the SECINFO reply is processed.

The new API can take a full GSS tuple (OID, QoP, and service).
Previously only the OID and service were considered.

nfs_find_best_sec() is updated to verify all flavors requested in a
SECINFO reply, including AUTH_NULL and AUTH_UNIX.  Previously these
two flavors were simply assumed to be supported without consulting
the RPC client.

Note that the replaced version of nfs_find_best_sec() can return
RPC_AUTH_MAXFLAVOR if the server returns a recognized OID but an
unsupported "service" value.  nfs_find_best_sec() now returns
RPC_AUTH_UNIX in this case.

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

1 files changed, 35 insertions, 0 deletions

diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index f529404..9b81be8 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -124,6 +124,41 @@ rpcauth_unregister(const struct rpc_authops *ops)
 EXPORT_SYMBOL_GPL(rpcauth_unregister);
 
 /**
+ * rpcauth_get_pseudoflavor - check if security flavor is supported
+ * @flavor: a security flavor
+ * @info: a GSS mech OID, quality of protection, and service value
+ *
+ * Verifies that an appropriate kernel module is available or already loaded.
+ * Returns an equivalent pseudoflavor, or RPC_AUTH_MAXFLAVOR if "flavor" is
+ * not supported locally.
+ */
+rpc_authflavor_t
+rpcauth_get_pseudoflavor(rpc_authflavor_t flavor, struct rpcsec_gss_info *info)
+{
+	const struct rpc_authops *ops;
+	rpc_authflavor_t pseudoflavor;
+
+	ops = auth_flavors[flavor];
+	if (ops == NULL)
+		request_module("rpc-auth-%u", flavor);
+	spin_lock(&rpc_authflavor_lock);
+	ops = auth_flavors[flavor];
+	if (ops == NULL || !try_module_get(ops->owner)) {
+		spin_unlock(&rpc_authflavor_lock);
+		return RPC_AUTH_MAXFLAVOR;
+	}
+	spin_unlock(&rpc_authflavor_lock);
+
+	pseudoflavor = flavor;
+	if (ops->info2flavor != NULL)
+		pseudoflavor = ops->info2flavor(info);
+
+	module_put(ops->owner);
+	return pseudoflavor;
+}
+EXPORT_SYMBOL_GPL(rpcauth_get_pseudoflavor);
+
+/**
  * rpcauth_list_flavors - discover registered flavors and pseudoflavors
  * @array: array to fill in
  * @size: size of "array"