SUNRPC: Support IPv6 when registering kernel RPC services

In order to advertise NFS-related services on IPv6 interfaces via
rpcbind, the kernel RPC server implementation must use
rpcb_v4_register() instead of rpcb_register().

A new kernel build option allows distributions to use the legacy
v2 call until they integrate an appropriate user-space rpcbind
daemon that can support IPv6 RPC services.

I tried adding some automatic logic to fall back if registering
with a v4 protocol request failed, but there are too many corner
cases.  So I just made it a compile-time switch that distributions
can throw when they've replaced portmapper with rpcbind.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 22 insertions, 0 deletions

diff --git a/fs/Kconfig b/fs/Kconfig
index c6ae4d4842eb..ed57a5a37250 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -1773,6 +1773,28 @@ config SUNRPC_XPRT_RDMA
 
           If unsure, say N.
 
+config SUNRPC_REGISTER_V4
+        bool "Register local RPC services via rpcbind v4 (EXPERIMENTAL)"
+        depends on SUNRPC && EXPERIMENTAL
+        default n
+        help
+          Sun added support for registering RPC services at an IPv6
+          address by creating two new versions of the rpcbind protocol
+          (RFC 1833).
+
+          This option enables support in the kernel RPC server for
+          registering kernel RPC services via version 4 of the rpcbind
+          protocol.  If you enable this option, you must run a portmapper
+          daemon that supports rpcbind protocol version 4.
+
+          Serving NFS over IPv6 from knfsd (the kernel's NFS server)
+          requires that you enable this option and use a portmapper that
+          supports rpcbind version 4.
+
+          If unsure, say N to get traditional behavior (register kernel
+          RPC services using only rpcbind version 2).  Distributions
+          using the legacy Linux portmapper daemon must say N here.
+
 config RPCSEC_GSS_KRB5
         tristate "Secure RPC: Kerberos V mechanism (EXPERIMENTAL)"
         depends on SUNRPC && EXPERIMENTAL