sunrpc: add a new "stringify_acceptor" rpc_credop

...and add an new rpc_auth function to call it when it exists. This
is only applicable for AUTH_GSS mechanisms, so we only specify this
for those sorts of credentials.
Signed-off-by: Jeff Layton <jlayton@poochiereds.net>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

include/linux/sunrpc/auth.h

@@ -140,6 +140,7 @@ struct rpc_credops {
 						void *, __be32 *, void *);
 	int			(*crkey_timeout)(struct rpc_cred *);
 	bool			(*crkey_to_expire)(struct rpc_cred *);
+	char *			(*crstringify_acceptor)(struct rpc_cred *);
 };
 
 extern const struct rpc_authops	authunix_ops;
@@ -182,6 +183,7 @@ void			rpcauth_clear_credcache(struct rpc_cred_cache *);
 int			rpcauth_key_timeout_notify(struct rpc_auth *,
 						struct rpc_cred *);
 bool			rpcauth_cred_key_to_expire(struct rpc_cred *);
+char *			rpcauth_stringify_acceptor(struct rpc_cred *);
 
 static inline
 struct rpc_cred *	get_rpccred(struct rpc_cred *cred)

net/sunrpc/auth.c

@@ -363,6 +363,15 @@ rpcauth_cred_key_to_expire(struct rpc_cred *cred)
 }
 EXPORT_SYMBOL_GPL(rpcauth_cred_key_to_expire);
 
+char *
+rpcauth_stringify_acceptor(struct rpc_cred *cred)
+{
+	if (!cred->cr_ops->crstringify_acceptor)
+		return NULL;
+	return cred->cr_ops->crstringify_acceptor(cred);
+}
+EXPORT_SYMBOL_GPL(rpcauth_stringify_acceptor);
+
 /*
  * Destroy a list of credentials
  */

net/sunrpc/auth_gss/auth_gss.c

@@ -1346,6 +1346,26 @@ gss_cred_init(struct rpc_auth *auth, struct rpc_cred *cred)
 	return err;
 }
 
+static char *
+gss_stringify_acceptor(struct rpc_cred *cred)
+{
+	char *string;
+	struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
+	struct xdr_netobj *acceptor = &gss_cred->gc_ctx->gc_acceptor;
+
+	/* no point if there's no string */
+	if (!acceptor->len)
+		return NULL;
+
+	string = kmalloc(acceptor->len + 1, GFP_KERNEL);
+	if (!string)
+		return string;
+
+	memcpy(string, acceptor->data, acceptor->len);
+	string[acceptor->len] = '\0';
+	return string;
+}
+
 /*
  * Returns -EACCES if GSS context is NULL or will expire within the
  * timeout (miliseconds)
@@ -1934,6 +1954,7 @@ static const struct rpc_credops gss_credops = {
 	.crwrap_req		= gss_wrap_req,
 	.crunwrap_resp		= gss_unwrap_resp,
 	.crkey_timeout		= gss_key_timeout,
+	.crstringify_acceptor	= gss_stringify_acceptor,
 };
 
 static const struct rpc_credops gss_nullops = {
@@ -1946,6 +1967,7 @@ static const struct rpc_credops gss_nullops = {
 	.crvalidate		= gss_validate,
 	.crwrap_req		= gss_wrap_req,
 	.crunwrap_resp		= gss_unwrap_resp,
+	.crstringify_acceptor	= gss_stringify_acceptor,
 };
 
 static const struct rpc_pipe_ops gss_upcall_ops_v0 = {