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>

3 files changed, 69 insertions, 4 deletions

diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index 727e506cacda..b5c067bccc45 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)
 {
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index d3ad81f8da5b..34c522021004 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -1619,6 +1619,7 @@ static const struct rpc_authops authgss_ops = {
         .crcreate       = gss_create_cred,
         .pipes_create   = gss_pipes_dentries_create,
         .pipes_destroy  = gss_pipes_dentries_destroy,
+        .list_pseudoflavors = gss_mech_list_pseudoflavors,
 };
 
 static const struct rpc_credops gss_credops = {
diff --git a/net/sunrpc/auth_gss/gss_mech_switch.c b/net/sunrpc/auth_gss/gss_mech_switch.c
index 782bfe1b6465..6ac5dfcd2928 100644
--- a/net/sunrpc/auth_gss/gss_mech_switch.c
+++ b/net/sunrpc/auth_gss/gss_mech_switch.c
@@ -239,14 +239,26 @@ gss_mech_get_by_pseudoflavor(u32 pseudoflavor)
 
 EXPORT_SYMBOL_GPL(gss_mech_get_by_pseudoflavor);
 
-int gss_mech_list_pseudoflavors(rpc_authflavor_t *array_ptr)
+/**
+ * gss_mech_list_pseudoflavors - Discover registered GSS 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 gss_mech_list_pseudoflavors(rpc_authflavor_t *array_ptr, int size)
 {
         struct gss_api_mech *pos = NULL;
         int j, i = 0;
 
         spin_lock(&registered_mechs_lock);
         list_for_each_entry(pos, &registered_mechs, gm_list) {
-                for (j=0; j < pos->gm_pf_num; j++) {
+                for (j = 0; j < pos->gm_pf_num; j++) {
+                        if (i >= size)
+                                return -ENOMEM;
                         array_ptr[i++] = pos->gm_pfs[j].pseudoflavor;
                 }
         }
@@ -254,8 +266,6 @@ int gss_mech_list_pseudoflavors(rpc_authflavor_t *array_ptr)
         return i;
 }
 
-EXPORT_SYMBOL_GPL(gss_mech_list_pseudoflavors);
-
 u32
 gss_svc_to_pseudoflavor(struct gss_api_mech *gm, u32 service)
 {