[PATCH 12/17] SUNRPC: Simplify svc_unregister()

[Chuck Lever <chuck.lever@oracle.com>]

We now have some evidence that PMAP_UNSET clears only "inet" entries,
and not "inet6" entries, in the rpcbind database.  The svc_unregister()
function also must work if user space doesn't support rpcbind version
4 at all.

Thus we'll send an rpcbind v4 UNSET, and if that fails, we'll send a
PMAP_UNSET.

This simplifies the code in svc_unregister() and provides better
backwards compatibility with legacy user space that does not support
rpcbind version 4.

This patch is part of a series that addresses
   http://bugzilla.kernel.org/show_bug.cgi?id=12256

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-and-Acked-by: Steve Dickson <steved@redhat.com>
---

 net/sunrpc/svc.c |   35 ++++++++++++++---------------------
 1 files changed, 14 insertions(+), 21 deletions(-)

diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index c89f04e..f1e0ad8 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -896,38 +896,31 @@ int svc_register(const struct svc_serv *serv, const int family,
 	return error;
 }
 
-#ifdef CONFIG_SUNRPC_REGISTER_V4
-
+/*
+ * If user space is running rpcbind, it should take the v4 UNSET
+ * and clear everything for this [program, version].  If user space
+ * is running portmap, it will reject the v4 UNSET, but won't have
+ * any "inet6" entries anyway.  So a PMAP_UNSET should be sufficient
+ * in this case to clear all existing entries for [program, version].
+ */
 static void __svc_unregister(const u32 program, const u32 version,
 			     const char *progname)
 {
-	struct sockaddr_in6 sin6 = {
-		.sin6_family		= AF_INET6,
-		.sin6_addr		= IN6ADDR_ANY_INIT,
-		.sin6_port		= 0,
-	};
 	int error;
 
-	error = rpcb_v4_register(program, version,
-				(struct sockaddr *)&sin6, "");
-	dprintk("svc: %s(%sv%u), error %d\n",
-			__func__, progname, version, error);
-}
-
-#else	/* CONFIG_SUNRPC_REGISTER_V4 */
+	error = rpcb_v4_register(program, version, NULL, "");
 
-static void __svc_unregister(const u32 program, const u32 version,
-			     const char *progname)
-{
-	int error;
+	/*
+	 * User space didn't support rpcbind v4, so retry this
+	 * request with the legacy rpcbind v2 protocol.
+	 */
+	if (error == -EPROTONOSUPPORT)
+		error = rpcb_register(program, version, 0, 0);
 
-	error = rpcb_register(program, version, 0, 0);
 	dprintk("svc: %s(%sv%u), error %d\n",
 			__func__, progname, version, error);
 }
 
-#endif	/* CONFIG_SUNRPC_REGISTER_V4 */
-
 /*
  * All netids, bind addresses and ports registered for [program, version]
  * are removed from the local rpcbind database (if the service is not